Omega Temp

Technical Reference SectionClick on a title or page number below to jump to that section.

Table of Contents Z-3

Temperature Measurement Z-4

Thermocouples Z-16

Probe Response Times Z-51

Resistance Temperature Measurement Z-53

Infrared Temperature Measurement Z-57

Cryogenic Temperature Measurement Z-94

Humidity & Dewpoint Z-100

Electrical Noise Reduction Z-104

Temperature Control Z-110

Safety Z-128

Data Storage and Transmission Z-149

ITS-90 Z-158

Standards Z-194

Non-Electric Temperature Measurement Z-197

Thermocouple Reference Data Z-198

RTD & Thermistor Reference Data Z-250

Conversion Charts Z-259

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TemperatureHandbook

Contents A - Z

OMEGA®

Z-3

Z Section Table of Contents

Technical Reference Section......Z-2Z Section Table of Contents .......Z-3Frequently Asked

Temperature Questions............Z-4Temperature Measurement

and Control Glossary................Z-5Practical Guidelines for

Temperature Measurement....Z-13Physical Properties of

Thermoelement Materials.......Z-16OMEGACLAD® Sheath

Selection Guide ......................Z-17Introduction to Practical

Temperature Measurements ...Z-19Using Thermocouples.............Z-21Using RTD’s............................Z-33Using Thermistors ..................Z-36

Nicrosil/Nisil Type N Thermocouple ........................Z-41

The Choice of Sheathingfor Mineral InsulatedThermocouples.......................Z-45

Temperature Properties ofSome Metals, Elementsand Compounds .....................Z-48

Thermocouple Properties .........Z-49Metal Sheathed and Exposed

Thermocouple ResponseTimes in Air ............................Z-51

Metal Sheathed and ExposedThermocouple ResponseTimes in Water .......................Z-52

OMEGA® InterchangeableThermistor Applications..........Z-53

Resistance Elementsand RTD’s ..............................Z-54

Introduction to InfraredPyrometers .............................Z-57

Principles of InfraredThermometry ..........................Z-59

Infrared TemperatureMeasurement: Theory and Application.......................Z-63

Noncontact TemperatureMeasurement: Theory and Application.......................Z-67

Fiber Optics ..............................Z-70Handheld Infrared

Thermometers forAll Applications .......................Z-74

Principles of Infrared Thermocouples.......................Z-76

Microcomputer-Based InfraredTemperature Transducers......Z-81

Infrared ThermocouplesExtended Temperature Ranges ...................................Z-84

Infrared Window Data...............Z-86IR Quick Help ...........................Z-87Table of Total Infrared

Emissivity ...............................Z-88Cryogenic Temperature Sensors:

CY7 Series Silicon Diodes .....Z-90Resolution and Accuracy of

Cryogenic TemperatureMeasurements........................Z-94

Heat Wave:A National Problem ..............Z-100

Dewpoint.................................Z-102Equilibrium Relative Humidity:

Saturated Salt Solutions.......Z-103Two-Wire Transmitters

For Temperature Applications ..........................Z-104

How to Use Ferrite CoresWith Instrumentation ............Z-105

“Electromagnetic Compatibility”and CE Conformity ...............Z-106

Low Noise ThermocoupleSystem .................................Z-108

Introduction to TemperatureControllers and SelectionConsiderations .....................Z-110

Temperature Control:Tuning a PID Controller........Z-115

Controller Operation ...............Z-118SSR Thermal Considerations..Z-119OMEGA PT41 Precision

Clock/Timer/ControllerFunctions..............................Z-122

Solid State Relays ..................Z-124Intrinsic Safety ........................Z-128Intrinsic Safety Circuit

Design ..................................Z-131Selecting a Recorder ..............Z-149Overview of IEEE-488 ............Z-151ASCII Code Values

and Hexadecimal Conversion Chart .................Z-154

The RS-232 Standard.............Z-157Guidelines for Realizing the

ITS-90...................................Z-158The International Temperature

Scale of 1990 .......................Z-186International Standard

Codes ...................................Z-194Application Notes:

Low-Cost Non-ElectricTemperature Gauges ...........Z-197

ITS-90 Thermocouple Directand Inverse Polynomials ......Z-198

Tungsten-Rhenium Thermocouples: Calibration Equivalents.........Z-202

Thermocouple Reference TablesRevised to ITS-90Type J, Deg. C .....................Z-203Type K, Deg. C.....................Z-204Type E, Deg. C.....................Z-207Type S, Deg. C.....................Z-208Type R, Deg. C.....................Z-210Type B, Deg. C.....................Z-212Type N, Deg. C.....................Z-214Type J, Deg. F......................Z-216Type K, Deg. F .....................Z-218Type E, Deg. F .....................Z-221Type T, Deg. F .....................Z-225Type S, Deg. F .....................Z-225Type R, Deg. F .....................Z-228Type B, Deg. F .....................Z-231Type N, Deg. F .....................Z-237Type C, Deg. C.....................Z-239Type C, Deg. F .....................Z-241

Tungsten and Tungsten/Rhenium:Thermocouple Tables...........Z-246

CHROMEGA® vs. Gold-0.07 Atomic Percent IronThermocouple Tableof Temp. vs.ThermoelectricVoltage .................................Z-247

Space for Transmittersin Probe Assembly Heads ....Z-249

Platinum Resistance Temp.Detector:Interchangability Tolerance Chart.....................................Z-250

ITS-90 Polynomial for RTDTemperature vs. Resistance ..Z-251

RTD Temp. vs. ResistanceTable For European Curve,Alpha = .00385 .....................Z-252

RTD Temp. vs. ResistanceTable For American Curve,Alpha = .00392 .....................Z-255

Thermistor Resistance vs. Temp............Z-256

Resistance vs. Temperaturefor Series “700” Linear Thermistor Pairs ........Z-258

Temperature ConversionChart Between C and F........Z-259

Conversion Factors forPhysical Units of Measure....Z-261

Ohm’s Law, Summary ............Z-263Conversion Factors for

Electrical Units of Measure...Z-264

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Q. How many feet of T/C wire can Irun?

A. For a specific instrument, check itsspecifications to see if there areany limits to the input impedance.However as a rule of thumb, limitthe resistance to 100 Ohmsresistance maximum, and thisdepends on the gage of the wire;the larger the diameter, the lessresistance/foot, the longer the runcan be. However, if theenvironment is electrically noisy,then a transmitter may be requiredwhich transmits a 4-20 mA signalthat can be run longer distancesand is more resistant to noise.

Q. Should I use a grounded orungrounded probe?

A. It depends on the instrumentation.If there is any chance that theremay be a reference to ground(common in controllers with non-isolated inputs), then anungrounded probe is required. If theinstrument is a handheld meter,then a grounded probe can almostalways be used.

Q. What size relay do I need tocontrol my heaters?

A. This must be calculated from knownparameters. Take the total wattageof heaters and divide this value inwatts by the voltage rating of theheaters in volts. The answer will bein amperes, and solid state andmechanical relays are rated by“current rating” in amperes.

Q. Can I send my 4-20 mA controloutput to a chart recorder tomonitor a process input?

A. No. A control output is designed tocontrol a valve or some equivalentcontrol device. If you need to sendan analog signal to a recordingdevice, then choose a controllerthat has a “retransmission orrecorder output” option.

Q. Can I split my one T/C signal totwo separate instruments?

A. No. The T/C signal is a very low-level millivolt signal, and shouldonly be connected to one device.Splitting to two devices may resultin bad readings or loss of signal.The solution is to use a “dual” T/Cprobe, or convert one T/C output toa 4-20 mA signal by using atransmitter or signal conditioner;then the new signal can be sent tomore than one instrument.

Q. What are the accuracies andtemperature ranges of thevarious thermocouples?

A. They are summarized in the tableson the first few pages of Section H.It is important to know that bothaccuracy and range depend onsuch things as the thermocouplealloys, the temperature beingmeasured, the construction of thesensor, the material of the sheath,the media being measured, thestate of the media (liquid, solid, orgas) and the diameter of either thethermocouple wire (if it is exposed)or the sheath diameter (if thethermocouple wire is not exposedbut is sheathed).

Q. Why can't I use ANY multimeterfor measuring temperature withthermocouples? What errors willresult if I don't use athermocouple temperaturemeter?

A. The magnitude of thethermoelectric voltage depends onthe closed (sensing) end as well asthe open (measuring) end of theparticular thermocouple alloy leads.Temperature sensing instrumentsthat use thermocouples take intoaccount the temperature of themeasuring end to determine thetemperature at the sensing end.Most millivoltmeters do not havethis capability, nor do they have theability to do non-linear scaling toconvert a millivoltage measurementto a temperature value. It ispossible to use lookup tables tocorrect a particular millivoltagereading and calculate thetemperature being sensed.However, the correction valueneeds to be continuouslyrecalculated, as it is generally notconstant over time. Small changesin temperature at the measuringinstrument and the sensing end willchange the correction value.

Q. How can I choose betweenthermocouples, resistancetemperature detectors (RTD’s),thermistors and infrared deviceswhen measuring temperature?

A. You have to consider thecharacteristics and costs of thevarious sensors as well as theavailable instrumentation. Inaddition: THERMOCOUPLESgenerally can measuretemperatures over widetemperature ranges, inexpensively,and are very rugged, but they arenot as accurate or stable as RTD’sand thermistors. RTD’s are stableand have a fairly wide temperaturerange, but are not as rugged andinexpensive as thermocouples.Since they require the use of

electric current to makemeasurements, RTD’s are subjectto inaccuracies from self-heating.THERMISTORS tend to be moreaccurate than RTD’s orthermocouples, but they have amuch more limited temperaturerange. They are also subject to self-heating. INFRARED SENSORScan be used to measuretemperatures higher than any of theother devices and do so withoutdirect contact with the surfacesbeing measured. However, they aregenerally not as accurate and aresensitive to surface radiationefficiency (or more precisely,surface emissivity). Using fiberoptic cables, they can measuresurfaces that are not within a directline of sight.

Q. What are the two most oftenoverlooked considerations inselecting an infrared temperaturemeasuring device?

A. The surface being measured mustfill the field of view, and the surfaceemissivity must be taken intoaccount.

Q. What are the best ways ofovercoming electrical noiseproblems?

A. 1) Use low noise, shielded leads,connectors and probes. 2) Useinstruments and connectors thatsuppress EMI and RF radiation. 3) Consider using analog signaltransmitters, especially currenttransmitters. 4) Evaluate thepossibility of using digitized signals.

Q. If a part is moving, can I stillmeasure temperature?

A. Yes. Use infrared devices or directcontacting sensors plus a slip ringassembly.

Q. Can a two-color infrared systembe used to measure lowemissivity surfaces?

A. Only if at high temperature, say,above 700°C (1300°F).

Q. What error will result if the spotsize of the infrared pyrometer islarger than the target size?

A. It would be indeterminate. Thevalue would be a weighted averagethat wouldn’t necessarily berepeatable.

Q. What readout should be usedwith the OS36, OS37 and OS38units?

A. Using the DP5000, BS6000, or theHH-200 would be best.

Frequently Asked Questions

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Absolute Zero: Temperature at which thermal energy is at a minimum.Defined as 0 Kelvin, calculated to be –273.15°C or –459.67°F.

AC: Alternating current; an electric current that reverses its direction atregularly recurring intervals.

Accuracy: The closeness of an indication or reading of a measurementdevice to the actual value of the quantity being measured. Usuallyexpressed as ± percent of full scale output or reading.

Adaptor: A mechanism or device for attaching non-mating parts.ADC: Analog-to-Digital Converter: an electronic device which converts

analog signals to an equivalent digital form, in either a binary codeor a binary-coded decimal code. When used for dynamicwaveforms, the sampling rate must be high to prevent aliasingerrors from occurring.

Address: The label or number identifying the memory location where aunit of information is stored.

Aliasing: If the sample rate of a function (fs) is less than two times thehighest frequency value of the function, the frequency isambiguously presented. The frequencies above (fs/2) will be foldedback into the lower frequencies producing erroneous data.

Alloy 11: A compensating alloy used in conjunction with pure copperas the negative leg to form extension wire for platinum—platinum-rhodium thermocouples Types R and S.

Alloy 200/226: The combination of compensating alloys used withtungsten vs. tungsten/26%-rhenium thermocouples as extensioncable for applications under 200°C.

Alloy 203/225: The combination of compensating alloys used withtungsten/3%-rhenium vs. tungsten/25%-rhenium thermocouples asextension cable for applications under 200°C.

Alloy 405/426: The combination of compensating alloys used withtungsten/5%-rhenium vs. tungsten/26%-rhenium thermocouples asextension cable for applications under 870°C.

ALOMEGA®: An aluminum nickel alloy used in the negative leg of atype K thermocouple (registered trademark of OMEGAENGINEERING, INC.).

Alphanumeric: A character set that contains both letters and digits.Alumel: An aluminum nickel alloy used in the negative leg of a Type K

thermocouple (Trade name of Hoskins Manufacturing Company).Ambient Compensation: The design of an instrument such that

changes in ambient temperature do not affect the readings of theinstrument.

Ambient Conditions: The conditions around the transducer (pressure,temperature, etc.).

Ambient Temperature: The average or mean temperature of thesurrounding air which comes in contact with the equipment andinstruments under test.

Ammeter: An instrument used to measure current.Ampere (amp): A unit used to define the rate of flow of electricity

(current) in a circuit; units are one coulomb (6.25 x 108 electrons)per second.

Amplifier: A device which draws power from a source other than theinput signal and which produces as an output an enlargedreproduction of the essential features of its input.

Amplitude: A measurement of the distance from the highest to thelowest excursion of motion, as in the case of mechanical body inoscillation or the peak-to-peak swing of an electrical waveform.

Analog Output: A voltage or current signal that is a continuousfunction of the measured parameter.

Analog-to-Digital Converter (A/D or ADC): A device or circuit thatoutputs a binary number corresponding to an analog signal level atthe input.

Angstrom: Ten to the minus tenth (10–10) meters or one millimicron, aunit used to define the wavelength of light. Designated by thesymbol Å.

ANSI: American National Standards Institute.Anti-Reset Windup: This is a feature in a three-mode PID controller

which prevents the integral (auto reset) circuit from functioningwhen the temperature is outside the proportional band.

Application Program: A computer program that accomplishes specifictasks, such as word processing.

ASCII: American Standard Code for Information Interchange. A sevenor eight bit code used to represent alphanumeric characters. It isthe standard code used for communications between dataprocessing systems and associated equipment.

ASME: American Society of Mechanical Engineers.Assembler: A program that translates assembly language instructions

into machine language instructions.ASTM: American Society for Testing and Materials.Asynchronous: A communication method where data is sent when it is

ready without being referenced to a timing clock, rather thanwaiting until the receiver signals that it is ready to receive.

ATC: Automatic temperature compensation.Auto-Zero: An automatic internal correction for offsets and/or drift at

zero voltage input.Automatic Reset: 1. A feature on a limit controller that automatically

resets the controller when the controlled temperature returns towithin the limit bandwidth set. 2. The integral function on a PIDcontroller which adjusts the proportional bandwidth with respect tothe set point to compensate for droop in the circuit, i.e., adjusts thecontrolled temperature to a set point after the system stabilizes.

AWG: American Wire Gage.

Background Noise: The total noise floor from all sources ofinterference in a measurement system, independent of the presenceof a data signal.

Backup: A system, device, file or facility that can be used as analternative in case of a malfunction or loss of data.

Bandwidth: A symmetrical region around the set point in whichproportional control occurs.

Basic: A high-level programming language designed at DartmouthCollege as a learning tool. Acronym for Beginner’s All-purposeSymbolic Instruction Code.

Baud: A unit of data transmission speed equal to the number of bits(or signal events) per second; 300 baud = 300 bits per second.

BCD, Buffered: Binary-coded decimal output with output drivers, toincrease line-drive capability.

BCD, Parallel: A digital data output format where every decimal digitis represented by binary signals on four lines and all digits arepresented in parallel. The total number of lines is 4 times thenumber of decimal digits.

BCD, Serial: A digital data output format where every decimal digit isrepresented by binary signals on four lines and up to five decimaldigits are presented sequentially. The total number of lines is fourdata lines plus one strobe line per digit.

BCD, Three-State: An implementation of parallel BCD, which has 0, 1and high-impedance output states. The high-impedance state isused when the BCD output is not addressed in parallel connectapplications.

Beryllia: BeO (Beryllium Oxide), a high-temperature mineral insulationmaterial; toxic when in powder form.

BIAS Current: A very low-level DC current generated by a panel meterand superimposed on a signal. This current may introduce ameasurable offset across a very high source impedance.

Binary Coded Decimal (BCD): The representation of a decimal number(base 10, 0 through 9) by means of a 4-bit binary nibble.

Binary: Refers to the base 2 numbering system, in which the onlyallowable digits are 0 and 1. Pertaining to a condition that has onlytwo possible values or states.

Bipolar: The ability of a panel meter to display both positive andnegative readings.

Bit: Acronym for binary digit. The smallest unit of computerinformation, it is either 0 or 1.

Blackbody: A theoretical object that radiates the maximum amount ofenergy at a given temperature, and absorbs all the energy incidentupon it. A blackbody is not necessarily black. (The name blackbodywas chosen because the color black is defined as the totalabsorption of light energy.)

BNC: A quick disconnect electrical connector used to interconnectand/or terminate coaxial cables.

Presenting . . . OMEGA’s TemperatureMeasurement and Control GlossaryA comprehensive glossary of terms used in the field of temperature measurement and control. A helpful referencetool for scientists, engineers, and technicians!

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Boiling Point: The temperature at which a substance in the liquidphase transforms to the gaseous phase; commonly refers to theboiling point of water which is 100°C (212°F) at sea level.

BPS: Bits per second.Breakdown Voltage Rating: The dc or ac voltage which can be applied

across insulation portions of a transducer without arcing orconduction above a specific current value.

BTU: British thermal unit. The quantity of thermal energy required toraise one pound of water at its maximum density, 1 degree F. OneBTU is equivalent to .293 watt hours, or 252 calories. One kilowatthour is equivalent to 3412 BTU.

Bulb (Liquid-in-Glass Thermometer): The area at the tip of a liquid-in-glass thermometer containing the liquid reservoir.

Burn-In: A long term screening test (either vibration, temperature orcombined test) that is effective in weeding out premature failuresbecause it simulates actual or worst case operation of the device,accelerated through a time, power, and temperature relationship.

Burst Proportioning: A fast-cycling output form on a timeproportioning controller (typically adjustable from 2 to 4 seconds)used in conjunction with a solid state relay to prolong the life ofheaters by minimizing thermal stress.

Bus: Parallel lines used to transfer signals between devices orcomponents. Computers are often described by their bus structure(i.e., S-100, IBM PC).

Byte: The representation of a character in binary. Eight bits.

Calender-van Dusen Equation: An equation that defines theresistance-temperature value of any pure metal that takes the formof (RT = RO) (1 + AT + BT2) for values between the ice point (0°C)and the freezing point of antimony (630.7°C) and the form RT = RO[1 + AT + BT2 + C (T–100)T2] between the oxygen point (–183.0°C)and the ice point (0°C).

Calibration: The process of adjusting an instrument or compiling adeviation chart so that its reading can be correlated to the actualvalue being measured.

Calorie: The quantity of thermal energy required to raise one gram ofwater 1°C at 15°C.

Cavitation: The boiling of a liquid caused by a decrease in pressurerather than an increase in temperature.

Celsius (Centigrade): A temperature scale defined by 0°C at the icepoint and 100°C at the boiling point of water at sea level.

Ceramic Insulation: High-temperature compositions of metal oxides usedto insulate a pair of thermocouple wires. The most common areAlumina (Al2O3), Beryllia (BeO), and Magnesia (MgO). Their applicationdepends upon temperature and type of thermocouple. High-purityalumina is required for platinum alloy thermocouples. Ceramicinsulators are available as single and multihole tubes or as beads.

Ceramic: Polycrystalline ferroelectric materials which are used as thesensing units in piezoelectric accelerometers. There are manydifferent grades, all of which can be made in various configurationsto satisfy different design requirements.

Character: A letter, digit or other symbol that is used as therepresentation of data. A connected sequence of characters is calleda character string.

Chatter: The rapid cycling on and off of a relay in a control processdue to insufficient bandwidth in the controller.

CHROMEGA®: A chromium-nickel alloy which makes up the positiveleg of type K and type E thermocouples (registered trademark ofOMEGA ENGINEERING, INC.).

Clear: To restore a device to a prescribed initial state, usually the zero state.Clipping: The term applied to the phenomenon which occurs when an

output signal is limited in some way by the full range of anamplifier, ADC or other device. When this occurs, the signal isflattened at the peak values, the signal approaches the shape of asquare wave, and high frequency components are introduced.Clipping may be hard, as is the case when the signal is strictlylimited at some level, or it may be soft, in which case the clippingsignal continues to follow the input at some reduced gain.

Clock: The device that generates periodic signals for synchronization.Closeness of Control: Total temperature variation from a desired set

point of system. Expressed as “closeness of control” is ±2°C or asystem bandwidth with 4°C, also referred to as “amplitude ofdeviation.”

CMR (Common-Mode Rejection): The ability of a panel meter toeliminate the effect of AC or DC noise between signal and ground.Normally expressed in dB at dc to 60 Hz. One type of CMR isspecified between SIG LO and PWR GND. In differential meters, asecond type of CMR is specified between SIG LO and ANA GND(METER GND).

CMV (Common-Mode Voltage): The AC or DC voltage which istolerable between signal and ground. One type of CMV is specifiedbetween SIG LO and PWR GND. In differential meters, a secondtype of CMV is specified between SIG HI or LO and ANA GND(METER GND).

Color Code: The ANSI established color code for thermocouple wiresin the negative lead is always red. Color Code for base metalthermocouples is yellow for Type K, black for Type J, purple forType E and blue for Type T.

Common Mode: The output form or type of control action used by atemperature controller to control temperature, i.e. on/off, timeproportioning, PID.

Common-Mode Rejection Ratio: The ability of an instrument to rejectinterference from a common voltage at it’s input terminals withrelation to ground, usually expressed in dB (decibels).

Communication: Transmission and reception of data among dataprocessing equipment and related peripherals.

Compensated Connector: A connector made of thermocouple alloysused to connect thermocouple probes and wires.

Compensating Alloys: Alloys used to connect thermocouples toinstrumentation. These alloys are selected to have similar thermalelectric properties as the thermocouple alloys (however, only over avery limited temperature range).

Compensating Loop: Lead wire resistance compensation for RTDelements where an extra length of wire is run from the instrument tothe RTD and back to the instrument, with no connection to the RTD.

Compensation: An addition of specific materials or devices tocounteract a known error.

Compiler: A program that translates a high-level language, such asBasic, into machine language.

Conductance: The measure of the ability of a solution to carry anelectrical current. (See Equivalent Conductance)

Conduction: The conveying of electrical energy or heat through or bymeans of a conductor.

Confidence Level: The range (with a specified value of uncertainty,usually expressed in percent) within which the true value of ameasured quantity exists.

Conformity Error: For thermocouples and RTD’s, the differencebetween the actual reading and the temperature shown in publishedtables for a specific voltage input.

Connection Head: An enclosure attached to the end of a thermocouplewhich can be cast iron, aluminum or plastic within which theelectrical connections are made.

Constantan: A copper-nickel alloy used as the negative lead in Type E,Type J, and Type T thermocouples.

Continuous Spectrum: A frequency spectrum that is characterized bynon-periodic data. The spectrum is continuous in the frequencydomain and is characterized by an infinite number of frequencycomponents.

Control Character: A character whose occurrence in a particularcontext starts, modifies or stops an operation that affects therecording, processing, transmission or interpretation of data.

Control Mode: The output form or type of control action used by atemperature controller to control temperature, i.e., on/off, timeproportioning, PID.

Control Point: The temperature at which a system is to be maintained.Convection: 1. The circulatory motion that occurs in a fluid at a non-

uniform temperature owing to the variation of its density and the actionof gravity. 2. The transfer of heat by this automatic circulation of fluid.

Counts: The number of time intervals counted by the dual-slope A/Dconverter and displayed as the reading of the panel meter, beforeaddition of the decimal point.

CPS: Cycles per second; the rate or number of periodic events in onesecond, expressed in Hertz (Hz).

CPU: Central processing unit. The part of the computer that containsthe circuits that control and perform the execution of computerinstructions.

Critical Damping: Critical damping is the smallest amount of dampingat which a given system is able to respond to a step functionwithout overshoot.

Cryogenics: Measurement of temperature at extremely low values, i.e.,below –200°C.

CSA: Canadian Standards Administration.Current Proportioning: An output form of a temperature controller

which provides a current proportional to the amount of controlrequired. Normally, a 4 to 20 milliamp current proportioning band.

Temperature Measurement and Control Glossary

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Current: The rate of flow of electricity. The unit is the ampere (a)defined as 1 ampere = 1 coulomb per second.

Curve Fitting: Curve fitting is the process of computing thecoefficients of a function to approximate the values of a given dataset within that function. The approximation is called a “fit”. Amathematical function, such as a least squares regression, is usedto judge the accuracy of the fit.

Cycle Time: The time, usually expressed in seconds, for a controller tocomplete one on/off cycle.

Damping: The reduction of vibratory movement through dissipation ofenergy. Types include viscous, coulomb, and solid.

Data Base: A large amount of data stored in a well-organized manner.A data base management system (DBMS) is a program that allowsaccess to the information.

dB (Decibel): 20 times the log to the base 10 of the ratio of twovoltages. Every 20 dB’s correspond to a voltage ratio of 10, every10 dB’s to a voltage ratio of 3.162. For instance, a CMR of 120 dBprovides voltage noise rejection of 1,000,000/1. An NMR of 70 dBprovides voltage noise rejection of 3,162/1.

DC: Direct current; an electric current flowing in one direction only andsubstantially constant in value.

Deadband: 1. For chart records: the minimum change of input signalrequired to cause a deflection in the pen position. 2. For temperaturecontrollers: the temperature band where heat is turned off upon risingtemperature and turned on upon falling temperature expressed indegrees. The area where no heating (or cooling) takes place.

Debug: To find and correct mistakes in a program.Decimal: Refers to a base ten number system using the characters 0

through 9 to represent values.Default: The value(s) or option(s) that are assumed during operation

when not specified.Degree: An incremental value in the temperature scale, i.e., there are

100 degrees between the ice point and the boiling point of water inthe Celsius scale and 180°F between the same two points in theFahrenheit scale.

Density: Mass per unit of volume of a substance, i.e.: grams/cu.cm. orpounds/cu.ft.

Deviation: The difference between the value of the controlled variableand the value at which it is being controlled.

Differential Input: A signal-input circuit where SIG LO and SIG HI areelectrically floating with respect to ANALOG GND (METER GND,which is normally tied to DIG GND). This allows the measurementof the voltage difference between two signals tied to the sameground and provides superior common-mode noise rejection.

Differential: For an on/off controller, it refers to the temperaturedifference between the temperature at which the controller turnsheat off and the temperature at which the heat is turned back on. Itis expressed in degrees.

Digit: A measure of the display span of a panel meter. By convention, afull digit can assume any value from 0 through 9, a 1⁄2-digit willdisplay a 1 and overload at 2, a 3⁄4-digit will display digits up to 3 andoverload at 4, etc. For example, a meter with a display span of±3999 counts is said to be a 3 3⁄4 digit meter.

Digital Output: An output signal which represents the size of an inputin the form of a series of discrete quantities.

Digital-to-Analog Converter (D/A or DAC): A device or circuit toconvert a digital value to an analog signal level.

DIN (Deutsche Industrial Norm): A set of German standardsrecognized throughout the world. The 1⁄8 DIN standard for panelmeters specifies an outer bezel dimension of 96 x 48 mm and apanel cutout of 92 x 45 mm.

DIN 43760: The standard that defines the characteristics of a 100 ohmplatinum RTD having a resistance vs. temperature curve specifiedby a = 0.00385 ohms per degree.

Discharge Time Constant: The time required for the output-voltagefrom a sensor or system to discharge 37% of its original value inresponse to a zero rise time step function input. This parameterdetermines a low frequency response.

Disk Operating System (DOS): Program used to control the transfer ofinformation to and from a disk, such as MS DOS.

Displacement: The measured distance traveled by a point from itsposition at rest. Peak to peak displacement is the total measuredmovement of a vibrating point between its positive and negativeextremes. Measurement units expressed as inches or milli-inches.

Dissipation Constant: The ratio for a thermistor which relates a changein internal power dissipation to a resultant change of bodytemperature.

Drift: A change of a reading or a set point value over long periods dueto several factors including change in ambient temperature, time,and line voltage.

Droop: A common occurrence in time-proportional controllers. Itrefers to the difference in temperature between the set point andwhere the system temperature actually stabilizes due to the time-proportioning action of the controller.

Dual Element Sensor: A sensor assembly with two independentsensing elements.

Dual-Slope A/D Converter: An analog-to-digital converter whichintegrates the signal for a specific time, then counts time intervalsfor a reference voltage to bring the integrated signal back to zero.Such converters provide high resolution at low cost, excellentnormal-mode noise rejection, and minimal dependence on circuitelements.

Duplex: Pertaining to simultaneous two-way independent datacommunication transmission in both directions. Same as “fullduplex”.

Duplex Wire: A pair of wires insulated from each other and with anouter jacket of insulation around the inner insulated pair.

Duty Cycle: The total time to one on/off cycle. Usually refers to theon/off cycle time of a temperature controller.

Dynamic Calibration: Calibration in which the input varies over aspecific length of time and the output is recorded vs. time.

Echo: To reflect received data to the sender. For example, keysdepressed on a keyboard are usually echoed as charactersdisplayed on the screen.

Electrical Interference: Electrical noise induced upon the signal wiresthat obscures the wanted information signal.

Electromotive Force (emf): The potential difference between the twoelectrodes in a cell. The cell emf is the cell voltage measured whenno current is flowing through the cell. It can be measured by meansof a pH meter with high input impedance.

Electronic Industries Association (EIA): A standards organizationspecializing in the electrical and functional characteristics ofinterface equipment.

EMF: Electromotive force. A rise in (electrical) potential energy. Theprincipal unit is the volt.

EMI: Electromagnetic interference.Emissivity: The ratio of energy emitted by an object to the energy

emitted by a blackbody at the same temperature. The emissivity ofan object depends upon its material and surface texture; a polishedmetal surface can have an emissivity around 0.2 and a piece ofwood can have an emissivity around 0.95.

Endothermic: A process is said to be endothermic when it absorbsheat.

End Point (Potentiometric): The apparent equivalence point of atitration at which a relatively large potential change is observed.

Enthalpy: The sum of the internal energy of a body and the product ofits volume multiplied by the pressure.

Environmental Conditions: All conditions to which a transducer maybe exposed during shipping, storage, handling, and operation.

Eprom: Erasable Programmable Read-Only Memory. The PROM can beerased by ultraviolet light or electricity.

Error: The difference between the value indicated by the transducerand the true value of the measured value being sensed. Usuallyexpressed in percent of full scale output.

Error Band: The allowable deviations to output from a specificreference norm. Usually expressed as a percentage of full scale.

Eutectic Temperature: The lowest possible melting point of a mixtureof alloys.

Excitation: The external application of electrical voltage current appliedto a transducer for normal operation.

Exothermic: A process is said to be exothermic when it releases heat.Expansion Factor: Correction factor for the change in density between

two pressure measurement areas in a constricted flow.Explosion-Proof Enclosure: An enclosure that can withstand an

explosion of gases within it and prevent the explosion of gasessurrounding it due to sparks, flashes or the explosion of thecontainer itself, and maintain an external temperature which will notignite the surrounding gases.

Exposed Junction: A form of construction of a thermocouple probewhere the hot or measuring junction protrudes beyond the sheathmaterial so as to be fully exposed to the medium being measured.This form of construction usually gives the fastest response time.


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Fahrenheit: A temperature scale defined by 32° at the ice point and212° at the boiling point of water at sea level.

Ferrule: A compressible tubular fitting that is compressed onto aprobe inside a compression fitting to form a gas-tight seal.

Field of View: A volume in space defined by an angular cone extendingfrom the focal plane of an instrument.

File: A set of related records or data treated as a unit.Firmware: Programs stored in PROM’s.Flag: Any of various types of indicators used for identification of a

condition or event, for example, a character that signals thetermination of a transmission.

Floppy Disk: A small, flexible disk carrying a magnetic medium inwhich digital data is stored for later retrieval and use.

FM: Factory Mutual Research Corporation. An organization which setsindustrial safety standards.

FM Approved: An instrument that meets a specific set of specificationsestablished by Factory Mutual Research Corporation.

FORTRAN: Formula Translation language. A widely used high-levelprogramming language well suited to problems that can beexpressed in terms of algebraic formulas. It is generally used inscientific applications.

Freezing Point: The temperature at which a substance goes from theliquid phase to the solid phase.

Frequency: The number of cycles over a specified time period overwhich an event occurs. The reciprocal is called the period.

Frequency Modulated Output: A transducer output which is obtainedin the form of a deviation from a center frequency, where thedeviation is proportional to the applied stimulus.

Frequency, Natural: The frequency of free (not forced) oscillations ofthe sensing element of a fully assembled transducer.

Frequency Output: An output in the form of frequency which varies asa function of the applied input.

Full Scale Output: The algebraic difference between the minimumoutput and maximum output.

Gain: The amount of amplification used in an electrical circuit.Galvanometer: An instrument that measures small electrical currents

by means of deflecting magnetic coils.Ground: 1. The electrical neutral line having the same potential as the

surrounding earth. 2. The negative side of DC power supply. 3.Reference point for an electrical system.

Grounded Junction: A form of construction of a thermocouple probewhere the hot or measuring junction is in electrical contact with thesheath material so that the sheath and thermocouple will have thesame electrical potential.

Half-Duplex: One way at a time data communication; both devices cantransmit and receive data, but only one at a time.

Handshake: An interface procedure that is based on status/data signalsthat assure orderly data transfer as opposed to asynchronousexchange.

Hardcopy: Output in a permanent form (usually a printout) rather thanin temporary form, as on disk or terminal display.

Hardware: The electrical, mechanical and electromechanicalequipment and parts associated with a computing system, asopposed to its firmware or software.

Heat: Thermal energy. Heat is expressed in units of calories or BTU’s.Heat Sink: 1. Thermodynamic. A body which can absorb thermal

energy. 2. Practical. A finned piece of metal used to dissipate theheat of solid state components mounted on it.

Heat Transfer: The process of thermal energy flowing from a body ofhigh energy to a body of low energy. Means of transfer are:conduction; the two bodies contact. Convection; a form ofconduction where the two bodies in contact are of different phases,i.e. solid and gas. Radiation: all bodies emit infrared radiation.

Heat Treating: A process for treating metals where heating to aspecific temperature and cooling at a specific rate changes theproperties of the metal.

Hertz (Hz): Units in which frequency is expressed. Synonymous withcycles per second.

Hexadecimal: Refers to a base sixteen number system using thecharacters 0 through 9 and A through F to represent the values.Machine language programs are often written in hexadecimal notation.

Hold: Meter HOLD is an external input which is used to stop the A/Dprocess and freeze the display. BCD HOLD is an external input usedto freeze the BCD output while allowing the A/D process to continueoperation.

Host: The primary or controlling computer in a multiple part system.Hysteresis: The difference in output when the measurand value is first

approached with increasing and then with decreasing values.Expressed in percent of full scale during any one calibration cycle.See Deadband

Impedance: The total opposition to electrical flow (resistive plusreactive).

Infrared: an area in the electromagnetic spectrum extending beyondred light from 760 nanometers to 1000 microns (106 nm). It is theform of radiation used for making non-contact temperaturemeasurements.

Input Impedance: The resistance of a panel meter as seen from thesource. In the case of a voltmeter, this resistance has to be takeninto account when the source impedance is high; in the case of anammeter, when the source impedance is low.

Insulated Junction: See Ungrounded JunctionInsulation Resistance: The resistance measured between two

insulated points on a transducer when a specific dc voltage isapplied at room temperature.

Integral: A form of temperature control. See Automatic Reset (2)Interchangeability Error: A measurement error that can occur if two or

more probes are used to make the same measurement. It is causedby a slight variation in characteristics of different probes.

Interface: The means by which two systems or devices are connectedand interact with each other.

Interrupt: To stop a process in such a way that it can be resumed.Intrinsically Safe: An instrument which will not produce any spark or

thermal effects under normal or abnormal conditions that will ignitea specified gas mixture.

IPTS-48: International Practical Temperature Scale of 1948. Fixedpoints in thermometry as specified by the Ninth General Conferenceof Weights and Measures which was held in 1948.

IPTS-68: International Practical Temperature Scale of 1968. Fixedpoints in thermometry set by the 1968 General Conference ofWeights and Measures.

ISA: Instrument Society of America.Isolation: The reduction of the capacity of a system to respond to an

external force by use of resilient isolating materials.Isothermal: A process or area that is a constant temperature.

Joule: The basic unit of thermal energy.Junction: The point in a thermocouple where the two dissimilar metals

are joined.

K: When referring to memory capacity, two to the tenth power (1024 indecimal notation).

Kelvin: Symbol K. The unit of absolute or thermodynamic temperaturescale based upon the Celsius scale with 100 units between the icepoint and boiling point of water. 0°C = 273.15K (there is no degree(°) symbol used with the Kelvin scale).

Kilowatt (kw): Equivalent to 1000 watts.Kilowatt Hour (kwh): 1000 watthours. Kilovolt amperes (kva): 1000

volt amps.KVA: Kilovolt amperes (1000 volt amps).

Lag: 1. A time delay between the output of a signal and the responseof the instrument to which the signal is sent. 2. A time relationshipbetween two waveforms where a fixed reference point on one waveoccurs after the same point of the reference wave.

Latent Heat: Expressed in BTU per pound. The amount of heat needed(absorbed) to convert a pound of boiling water to a pound of steam.

Leakage Rate: The maximum rate at which a fluid is permitted ordetermined to leak through a seal.

Limits of Error: A tolerance band for the thermal electric response ofthermocouple wire expressed in degrees or percentage defined byANSI specification MC-96.1 (1975).

Linearity: The closeness of a calibration curve to a specified straightline. Linearity is expressed as the maximum deviation of anycalibration point on a specified straight line during any onecalibration cycle.

Load: The electrical demand of a process expressed as power (watts),current (amps) or resistance (ohms).

Load Impedance: The impedance presented to the output terminals ofa transducer by the associated external circuitry.

Logarithmic Scale: A method of displaying data (in powers of ten) to yieldmaximum range while keeping resolution at the low end of the scale.


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Loop Resistance: The total resistance of a thermocouple circuitcaused by the resistance of the thermocouple wire. Usually used inreference to analog pyrometers which have typical loop resistancerequirements of 10 ohms.

LSD (Least-Significant Digit): The rightmost active (non-dummy)digit of the display.

LS-TTL Compatible: For digital input circuits, a logic 1 is obtained forinputs of 2.0 to 5.5 V which can source 20 µA, and a logic 0 isobtained for inputs of 0 to 0.8 V which can sink 400 µA. For digitaloutput signals, a logic 1 is represented by 2.4 to 5.5 V with acurrent source capability of at least 400 µA, and a logic 0 isrepresented by 0 to 0.6 V with a current sink capability of at least 16MA. “LS” stands for Low-power Schottky.

LS-TTL Unit Load: A load with LS-TTL voltage levels, which will draw20 µA for a logic 1 and –400 µA for a logic 0.

M: Mega; one million. When referring to memory capacity, two to thetwentieth power (1,048,576 in decimal notation).

Manual Reset (Adjustment): The adjustment on a proportioningcontroller which shifts the proportioning band in relationship to theset point to eliminate droop or offset errors.

Manual Reset (Switch): The switch in a limit controller that manuallyresets the controller after the limit has been exceeded.

Maximum Operating Temperature: The maximum temperature atwhich an instrument or sensor can be safely operated.

Maximum Power Rating: The maximum power in watts that a devicecan safely handle.

Mean Temperature: The average of the maximum and minimumtemperature of a process equilibrium.

Measurand: A physical quantity, property, or condition which is measured.Measuring Junction: The thermocouple junction referred to as the hot

junction that is used to measure an unknown temperature.Melting Point: The temperature at which a substance transforms from

a solid phase to a liquid phase.Mica: A transparent mineral used as window material in high-

temperature ovens.Microamp: One millionth of an ampere, 10–6 amps.Microcomputer: A computer which is physically small. It can fit on top

of or under a desk; based on LSI circuitry, computers of this typeare now available with much of the power currently associated withminicomputer systems.

Micron: One millionth of a meter, 10–6 meters.Microvolt: One millionth of a volt, 10–6 volts.Mil: One thousandth of an inch (.001≤).Milliamp: One thousandth of an amp, 10–3 amps, symbol mA.Millimeter: One thousandth of a meter, symbol mm.Millivolt: Unit of electromotive force. It is the difference in potential

required to make a current of 1 millampere flow through aresistance of 1 ohm; one thousandth of a volt, symbol mV.

Mineral-insulated Thermocouple: A type of thermocouple cable whichhas an outer metal sheath and mineral (magnesium oxide)insulation inside separating a pair of thermocouple wires fromthemselves and from the outer sheath. This cable is usually drawndown to compact the mineral insulation and is available indiameters from .375 to .010 inches. It is ideally suited for high-temperature and severe-duty applications.

Minor Scale Division: On an analog scale, the smallest indicateddivision of units on the scale.

Modem: Modulator/Demodulator. A device that transforms digitalsignals into audio tones for transmission over telephone lines, anddoes the reverse for reception.

MSD (Most-Significant Digit): The leftmost digit of the display.Mueller Bridge: A high-accuracy bridge configuration used to measure

three-wire RTD thermometers.Multiplex: A technique which allows different input (or output) signals

to use the same lines at different times, controlled by an externalsignal. Multiplexing is used to save on wiring and I/O ports.

N/C (No Connection): A connector point for which there is no internalconnection.

NBS: National Bureau of Standards.NEC: National Electric Codes.Negative Temperature Coefficient: A decrease in resistance with an

increase in temperature.

NEMA-4: A standard from the National Electrical ManufacturersAssociation, which defines enclosures intended for indoor oroutdoor use primarily to provide a degree of protection againstwindblown dust and rain, splashing water, and hose-directed water.

NEMA-7: A standard from the National Electrical ManufacturersAssociation, which defines explosion-proof enclosures for use inlocations classified as Class I, Groups A, B, C or D, as specified inthe National Electrical Code.

NEMA-12: A standard from the National Electrical ManufacturersAssociation, which defines enclosures with protection against dirt,dust, splashes by non-corrosive liquids, and salt spray.

NEMA-Size Case: An older US case standard for panel meters, whichrequires a panel cutout of 3.93 x 1.69 inches.

Network: A group of computers that are connected to each other bycommunications lines to share information and resources.

Nibble: One half of a byte.Nicrosil/Nisil: A nickel-chrome/nickel-silicone thermal alloy used to

measure high temperatures. Inconsistencies in thermoelectricvoltages exist in these alloys with respect to the wire gage.

NMR (Normal-Mode Rejection): The ability of a panel meter to filterout noise superimposed on the signal and applied across the SIG HIto SIG LO input terminals. Normally expressed in dB at 50/60 Hz.

Noise: An unwanted electrical interference on the signal wires.Normal-Mode Rejection Ratio: The ability of an instrument to reject

interference usually of line frequency (50–60 Hz) across its inputterminals.

NPT: National Pipe Thread.Null: A condition, such as balance, which results in a minimum

absolute value of output.

Octal: Pertaining to a base 8 number system.O.D.: Outside diameter.Offset: The difference in temperature between the set point and the

actual process temperature. Also referred to as droop.Ohmmeter: An instrument used to measure electrical resistance.On/off Controller: A controller whose action is fully on or fully off.Open Circuit: The lack of electrical contact in any part of the

measuring circuit. An open circuit is usually characterized by rapidlarge jumps in displayed potential, followed by an off-scale reading.

Operating System: A collection of programs that controls the overalloperation of a computer and performs such tasks as assigning placesin memory to programs and data, processing interrupts, schedulingjobs and controlling the overall input/output of the system.

Optical Isolation: Two networks which are connected only through anLED transmitter and photoelectric receiver with no electricalcontinuity between the two networks.

Output: The electrical signal which is produced by an applied input tothe transducer.

Output Impedance: The resistance as measured on the outputterminals of a pressure transducer.

Output Noise: The RMS, peak-to-peak (as specified) ac component ofa transducer’s dc output in the absence of a measurand variation.

Overshoot: The number of degrees by which a process exceeds the setpoint temperature when coming up to the set point temperature.

Parallax: An optical illusion which occurs in analog meters and causesreading errors. It occurs when the viewing eye is not in the sameplane, perpendicular to the meter face, as the indicating needle.

Parallel Transmission: Sending all data bits simultaneously.Commonly used for communications between computers andprinter devices.

Parity: A technique for testing transmitting data. Typically, a binarydigit is added to the data to make the sum of all the digits of thebinary data either always even (even parity) or always odd (oddparity).

Peltier Effect: When a current flows through a thermocouple junction,heat will either be absorbed or evolved depending on the directionof current flow. This effect is independent of joule I2 R heating.

Peripheral: A device that is external to the CPU and main memory, i.e.,printer, modem or terminal, but is connected by the appropriateelectrical connections.

Phase: A time-based relationship between a periodic function and areference. In electricity, it is expressed in angular degrees todescribe the voltage or current relationship of two alternatingwaveforms.

Phase Difference: The time expressed in degrees between the samereference point on two periodic waveforms.


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Phase Proportioning: A form of temperature control where the powersupplied to the process is controlled by limiting the phase angle ofthe line voltage.

PID: Proportional, integral, derivative. A three-mode control actionwhere the controller has time proportioning, integral (auto reset)and derivative rate action.

Piezoresistance: Resistance that changes with stress.Pixel: Picture element. Definable locations on a display screen that are

used to form images on the screen. For graphic displays, screenswith more pixels provide higher resolution.

Platinel: A non-standard, high temperature platinum thermocouplealloy whose thermoelectric voltage nearly matches a Type Kthermocouple (Trademark of Englehard Industries).

Platinum: A noble metal which in its pure form is the negative wire ofType R and Type S thermocouples.

Platinum 6% Rhodium: The platinum-rhodium alloy used as thenegative wire in conjunction with platinum-30% rhodium to form aType B thermocouple.

Platinum 10% Rhodium: The platinum-rhodium alloy used as thepositive wire in conjunction with pure platinum to form a Type Sthermocouple.

Platinum 13% Rhodium: The platinum-rhodium alloy used as thepositive wire in conjunction with pure platinum to form a Type Rthermocouple.

Platinum 30% Rhodium: The platinum-rhodium alloy used as thepositive wire in conjunction with platinum 6% rhodium to form aType B thermocouple.

Platinum 67: To develop thermal emf tables for thermocouples, theNational Bureau of Standards paired each thermocouple alloyagainst a pure platinum wire (designated Platinum 2 prior to 1973,and currently Platinum 67). The thermal emf’s of any alloycombination can be determined by summing the “vs. Pt-67” emf’sof the alloys, i.e., the emf table for a Type K thermocouple is derivedfrom the Chromel vs. Pt-67 and the Alumel vs .Pt-67 values.

Polarity: In electricity, the quality of having two oppositely chargedpoles, one positive, one negative.

Port: A signal input (access) or output point on a computer.Positive Temperature Coefficient: An increase in resistance due to an

increase in temperature.Potential Energy: Energy related to the position or height above a

place to which fluid could possibly flow.Potentiometer: 1. A variable resistor often used to control a circuit.

2. A balancing bridge used to measure voltage.Power Supply: A separate unit or part of a circuit that supplies power

to the rest of the circuit or to a system.PPM: Abbreviation for “parts per million,” sometimes used to express

temperature coefficients. For instance, 100 ppm is identical to 0.01%.Primary Standard (NBS): The standard reference units and physical

constants maintained by the National Bureau of Standards uponwhich all measurement units in the United States are based.

Probe: A generic term that is used to describe many types oftemperature sensor.

Process Meter: A panel meter with sizeable zero and span adjustmentcapabilities, which can be scaled for readout in engineering units forsignals such as 4–20 mA, 10–50 mA and 1–5 V.

Program: A list of instructions that a computer follows to perform atask.

Prom: Programmable read-only memory. A semiconductor memorywhose contents cannot be changed by the computer after it hasbeen programmed.

Proportioning Band: A temperature band expressed in degrees withinwhich a temperature controller’s time proportioning function isactive.

Proportioning Control Mode: A time proportioning controller wherethe amount of time that the relay is energized is dependent upon thesystem’s temperature.

Proportioning Control plus Derivative Function: A time proportioningcontroller with a derivative function. The derivative function sensesthe rate at which a system’s temperature is either increasing ordecreasing and adjusts the cycle time of the controller to minimizeovershoot or undershoot.

Proportioning Control plus Integral: A two-mode controller with timeproportioning and integral (auto reset) action. The integral functionautomatically adjusts the temperature at which a system hasstabilized back to the set point temperature, thereby eliminatingdroop in the system.

Proportioning Control with Integral and Derivative Functions: Threemode PID controller. A time-proportioning controller with integraland derivative functions. The integral function automatically adjuststhe system temperature to the set point temperature to eliminatedroop due to the time proportioning function. The derivativefunction senses the rate of rise or fall of the system temperatureand automatically adjusts the cycle time of the controller tominimize overshoot or undershoot.

Protection Head: An enclosure usually made out of metal at the end ofa heater or probe where connections are made.

Protection Tube: A metal or ceramic tube, closed at one end, intowhich a temperature sensor is inserted. The tube protects thesensor from the medium into which it is inserted.

Protocol: A formal definition that describes how data is to beexchanged.

PSIA: Pounds per square inch absolute. Pressure referenced to avacuum.

PSID: Pounds per square inch differential. Pressure difference betweentwo points.

PSIG: Pound per square inch gage. Pressure referenced to ambient airpressure.

PSIS: Pounds per square inch standard. Pressure referenced to astandard atmosphere.

Pulse Width Modulation: An output in the form of duty cycle whichvaries as a function of the applied measurand.

Radiation: See InfraredRandom Access Memory (RAM): Memory that can be both read and

changed during computer operation. Unlike other semi-conductormemories, RAM is volatile—if power to the RAM is disrupted orlost, all the data stored is lost.

Range: Those values which a transducer is intended to measure,specified by upper and lower limits.

Rangeability: The ratio of the maximum flowrate to the minimumflowrate of a meter.

Rankine (°R): An absolute temperature scale based upon theFahrenheit scale with 180° between the ice point and boiling pointof water. 459.67°R = 0°F.

Rate Action: The derivative function of a temperature controller.Rate Time: The time interval over which the system temperature is

sampled for the derivative function.Ratiometric Measurement: A measurement technique where an

external signal is used to provide the voltage reference for the dual-slope A/D converter. The external signal can be derived from thevoltage excitation applied to a bridge circuit or pick-off supply,thereby eliminating errors due to power supply fluctuations.

Read Only Memory (ROM): Memory that contains fixed data. Thecomputer can read the data, but cannot change it in any way.

Real Time: The time interval over which the system temperature issampled for the derivative function.

Record: A collection of unrelated information that is treated as a singleunit.

Recovery Time: The length of time which it takes a transducer toreturn to normal after applying a proof pressure.

Reference Junction: The cold junction in a thermocouple circuit which isheld at a stable, known temperature. The standard referencetemperature is 0°C (32°F). However, other temperatures can be used.

Refractory Metal Thermocouple: A class of thermocouples withmelting points above 3600°F. The most common are made fromtungsten and tungsten/rhenium alloys, Types G and C. They can beused for measuring high temperatures up to 4000°F (2200°C) innon-oxidizing, inert, or vacuum environments.

Relay (Mechanical): An electromechanical device that completes orinterrupts a circuit by physically moving electrical contacts intocontact with each other.

Relay (Solid State): A solid state switching device which completes orinterrupts a circuit electrically with no moving parts.

Remote: Not hard-wired; communicating via switched lines, such astelephone lines. Usually refers to peripheral devices that are locatedat a site away from the CPU.

Repeatability: The ability of a transducer to reproduce output readingswhen the same measurand value is applied to it consecutively,under the same conditions, and in the same direction. Repeatabilityis expressed as the maximum difference between output readings.

Resistance: The resistance to the flow of electric current measured inohms (Ω). For a conductor, resistance is a function of diameter,resistivity (an intrinsic property of the material) and length.


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Resistance Ratio Characteristic: For thermistors, the ratio of theresistance of the thermistor at 25°C to the resistance at 125°C.

Resistance Temperature Characteristic: A relationship between athermistor’s resistance and the temperature.

Resolution: The smallest detectable increment of measurement.Resolution is usually limited by the number of bits used to quantizethe input signal. For example, a 12-bit A/D can resolve to one part in4096 (2 to the 12 power equals 4096).

Resonant Frequency: The measurand frequency at which a transducerresponds with maximum amplitude.

Response Time: The length of time required for the output of atransducer to rise to a specified percentage of its final value as aresult of a step change of input.

Response Time (time constant): The time required by a sensor toreach 63.2% of a step change in temperature under a specified setof conditions. Five time constants are required for the sensor tostabilize at 100% of the step change value.

RFI: Radio frequency interference.Rheostat: A variable resistor.Rise Time: The time required for a sensor or system to respond to an

instantaneous step function, measured from the 10% to 90% pointson the response waveforms.

Room Conditions: Ambient environmental conditions under whichtransducers must commonly operate.

Root Mean Square (RMS): Square root of the mean of the square ofthe signal taken during one full cycle.

RTD: Resistance temperature detector.

SAMA: Scientific Apparatus Makers Association. An association thathas issued standards covering platinum, nickel, and copperresistance elements (RTD’s).

SCR: Silicon controlled rectifier.Scroll: To move all or part of the screen material up or down, left or

right, to allow new information to appear.Seebeck Coefficient: The derivative (rate of change) of thermal EMF with

respect to temperature, normally expressed as millivolts per degree.Seebeck Effect: When a circuit is formed by a junction of two

dissimilar metals and the junctions are held at differenttemperatures, a current will flow in the circuit caused by thedifference in temperature between the two junctions.

Seebeck EMF: The open circuit voltage caused by the difference intemperature between the hot and cold junctions of a circuit madefrom two dissimilar metals.

Self-Heating: Internal heating of a transducer as a result of powerdissipation.

Sensing Element: That part of a transducer which reacts directly inresponse to input.

Sensitivity: The minimum change in input signal to which aninstrument can respond.

Sensitivity Shift: A change in slope of the calibration curve due to achange in sensitivity.

Sequential Access: An access mode in which records are retrieved inthe same order in which they were written. Each successive accessto the file refers to the next record in the file.

Serial Transmission: Sending one bit at a time on a singletransmission line. Compare with Parallel Transmission.

Set Point: The temperature at which a controller is set to control asystem.

Settling Time: The time taken for the display to settle within one digitfinal value when a step is applied to the meter input.

SI: System Internationale. The name given to the standard metricsystem of units.

Signal: An electrical transmittance (either input or output) thatconveys information.

Signal Conditioner: A circuit module which offsets, attenuates,amplifies, linearizes and/or filters the signal for input to the A/Dconverter. The typical output signal conditioner is +2 V dc.

Signal Conditioning: To process the form or mode of a signal so as tomake it intelligible to, or compatible with, a given device, includingsuch manipulation as pulse shaping, pulse clipping, compensating,digitizing, and linearizing.

Single-Ended Input: A signal-input circuit where SIG LO (orsometimes SIG HI) is tied to METER GND. Ground loops arenormally not a problem in AC-powered meters, since METER GNDis transformer-isolated from AC GND.

Single Precision: The degree of numeric accuracy that requires theuse of one computer word. In single precision, seven digits arestored, and up to seven digits are printed. Contrast with DoublePrecision.

Software: Generally, programs loaded into a computer from externalmass storage but also extended to include operating systems anddocumentation.

Source Code: A non-executable program written in a high-levellanguage. A compiler or assembler must translate the source codeinto object code (machine language) that the computer canunderstand and process.

Span: The difference between the upper and lower limits of a rangeexpressed in the same units as the range.

Span Adjustment: The ability to adjust the gain of a process or strainmeter so that a specified display span in engineering unitscorresponds to a specified signal span. For instance, a display spanof 200°F may correspond to the 16 mA span of a 4–20 mAtransmitter signal.

Spare: A connector point reserved for options, specials, or otherconfigurations. The point is identified by an (E#) for location on theelectrical schematic.

Specific Gravity: The ratio of mass of any material to the mass of thesame volume of pure water at 4°C.

Specific Heat: The ratio of thermal energy required to raise thetemperature of a body 1° to the thermal energy required to raise anequal mass of water 1°.

Spectral Filter: A filter which allows only a specific band width of theelectromagnetic spectrum to pass, i.e., 4 to 8 micron infraredradiation.

Spectrum: The resolving of overall vibration into amplitudecomponents as a function of frequency.

Spectrum Analysis: Utilizing frequency components of a vibrationsignal to determine the source and cause of vibration.

Spot Size: The diameter of the circle formed by the cross section ofthe field of view of an optical instrument at a given distance.

Spurious Error: Random or erratic malfunction.SSR: Solid state relay. See Relay, Solid StateStability: The ability of an instrument or sensor to maintain a

consistent output when a constant input is applied.Stop Bit: A signal following a character or block that prepares the

receiving device to receive the next character or block.String: A sequence of characters.Super Cooling: The cooling of a liquid below its freezing temperature

without the formation of the solid phase.Super Heating: 1. The heating of a liquid above its boiling temperature

without the formation of the gaseous phase. 2. The heating of thegaseous phase considerably above the boiling-point temperature toimprove the thermodynamic efficiency of a system.

Surge Current: A current of short duration that occurs when power isfirst applied to capacitive loads or temperature dependent resistiveloads such as tungsten or molybdenum heaters—usually lastingnot more than several cycles.

Syntax: The rules governing the structure of a language.

Tape: A recording medium for data or computer programs. Tape canbe in permanent form, such as perforated paper tape, or erasable,such as magnetic tape. Generally, tape is used as a mass storagemedium, in magnetic form, and has a much higher storage capacitythan disk storage, but it takes much longer to write or recover datafrom tape than from a disk.

Teflon: A fluorocarbon polymer used for insulation of electrical wires(trademark of DuPont).

Telecommunication: Synonym for data communication. Thetransmission of information from one point to another.

TEMPCO: Abbreviation for “temperature coefficient”: the errorintroduced by a change in temperature. Normally expressed in %/°Cor ppm/°C.

Temperature Error: The maximum change in output, at any measurandvalue within a specified range, when the transducer temperature ischanged from room temperature to specified temperature extremes.

Temperature Range, Compensated: The range of ambienttemperatures within which all tolerances specified for Thermal ZeroShift and Thermal Sensitivity Shift are applicable (temperatureerror).

Temperature Range, Operable: The range of ambient temperatures,given by their extremes, within which a transducer may beoperated. Exceeding compensated range may require recalibration.


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Terminal: An input/output device used to enter data into a computerand record the output.

Thermal Coefficient of Resistance: The change in resistance of asemiconductor per unit change in temperature over a specific rangeof temperature.

Thermal Conductivity: The ability of a material to conduct heat in theform of thermal energy.

Thermal emf: See Seebeck emfThermal Expansion: An increase in size due to an increase in

temperature expressed in units of an increase in length or increasein size per degree, i.e. inches/inch/degree C.

Thermal Gradient: The distribution of a differential temperaturethrough a body or across a surface.

Thermal Sensitivity Shift: The sensitivity shift due to changes of theambient temperature from room temperature to the specified limitsof the compensated temperature range.

Thermal Zero Shift: An error due to changes in ambient temperaturein which the zero pressure output shifts. Thus, the entire calibrationcurve moves in a parallel displacement.

Thermistor: A temperature-sensing element composed of sinteredsemiconductor material which exhibits a large change in resistanceproportional to a small change in temperature. Thermistors usuallyhave negative temperature coefficients.

Thermocouple: The junction of two dissimilar metals which has avoltage output proportional to the difference in temperaturebetween the hot junction and the lead wires (cold junction) (refer toSeebeck emf).

Thermocouple Type Material(ANSI Symbol)

J Iron/ConstantanK CHROMEGA®/ALOMEGA®

T Copper/ConstantanE CHROMEGA/ConstantanR Platinum/Platinum 13% RhodiumS Platinum/Platinum 10% RhodiumB Platinum 6% Rhodium/Platinum

30% RhodiumG* Tungsten/Tungsten 26% RheniumC* Tungsten 5% Rhenium/Tungsten

26% RheniumD* Tungsten 3% Rhenium/Tungsten

25% Rhenium*Not ANSI symbols

Thermopile: An arrangement of thermocouples in series such thatalternate junctions are at the measuring temperature and thereference temperature. This arrangement amplifies thethermoelectric voltage. Thermopiles are usually used as infrareddetectors in radiation pyrometry.

Thermowell: A closed-end tube designed to protect temperaturesensors from harsh environments, high pressure, and flows. Theycan be installed into a system by pipe thread or welded flange andare usually made of corrosion-resistant metal or ceramic material,depending upon the application.

Thomson Effect: When current flows through a conductor within athermal gradient, a reversible absorption or evolution of heat willoccur in the conductor at the gradient boundaries.

Transducer: A device (or medium) that converts energy from one formto another. The term is generally applied to devices that takephysical phenomena (pressure, temperature, humidity, flow, etc.)and convert them to electrical signals.

Transmitter (Two-Wire): A device which is used to transmit temperaturedata from either a thermocouple or RTD via a two-wire current loop.The loop has an external power supply and the transmitter acts as avariable resistor with respect to its input signal.

Triac: A solid state switching device used to switch alternating currentwave forms.

Triple Point: The temperature and pressure at which solid, liquid, andgas phases of a given substance are all present simultaneously invarying amounts.

Triple Point (Water): The thermodynamic state where all three phases,solid, liquid, and gas, may all be present in equilibrium. The triplepoint of water is .01°C.

True RMS: The true root-mean-square value of an AC or AC-plus-DCsignal, often used to determine power of a signal. For a perfect sinewave, the RMS value is 1.11072 times the rectified average value,which is utilized for low-cost metering. For significantly non-sinusoidal signals, a true RMS converter is required.

TTL: Transistor-to-transistor logic. A form of solid state logic whichuses only transistors to form the logic gates.

TTL-Compatible: For digital input circuits, a logic 1 is obtained for inputsof 2.0 to 5.5 V which can source 40 µA, and a logic 0 is obtained forinputs of 0 to 0.8 V which can sink 1.6 mA. For digital output signals,a logic 1 is represented by 2.4 to 5.5 V with a current sourcecapability of at least 400 µA, and a logic 0 is represented by 0 to 0.6 Vwith a current sink capability of at least 16 mA.

TTL Unit Load: A load with TTL voltage levels, which will draw 40 µAfor a logic 1 and –1.6 mA for a logic 0.

Typical: Error within plus or minus one standard deviation (±1%) ofthe nominal specified value, as computed from the total population.

UL: Underwriters Laboratories, Inc. An independent laboratory thatestablishes standards for commercial and industrial products.

Ultraviolet: That portion of the electromagnetic spectrum below bluelight (380 nanometers).

Undershoot: The difference in temperature between the temperature aprocess goes to, below the set point, after the cooling cycle isturned off and the set point temperature.

Ungrounded Junction: A form of construction of a thermocoupleprobe where the hot or measuring junction is fully enclosed by andinsulated from the sheath material.

Union: A form of pipe fitting where two extension pipes are joined at aseparable coupling.

Vacuum: A pressure less than atmospheric pressure.Velocity: The time rate of change of displacement; dx/dt.Vibration Transducer: Generally, any device which converts

movement, either shock or steady state vibration, into an electricalsignal proportional to the movement; a sensor.

Volt: The (electrical) potential difference between two points in acircuit. The fundamental unit is derived as work per unit charge—(V = W/Q). One volt is the potential difference required to move onecoulomb of charge between two points in a circuit using one jouleof energy.

Voltage: An electrical potential which can be measured in volts.Voltmeter: An instrument used to measure voltage.

Watt Density: The watts emanating from each square inch of heatedsurface area of a heater. Expressed in units of watts per squareinch.

Wheatstone Bridge: A network of four resistances, an emf source, anda galvanometer connected such that when the four resistances arematched, the galvanometer will show a zero deflection or “null”reading.

Window: In computer graphics, a defined area in a system notbounded by any limits; unlimited “space” in graphics.

Word: Number of bits treated as a single unit by the CPU. In an 8-bitmachine, the word length is 8 bits; in a sixteen-bit machine, it is16 bits.

Working Standard: A standard of unit measurement calibrated fromeither a primary or secondary standard which is used to calibrateother devices or make comparison measurements.

Zero Adjustment: The ability to adjust the display of a process orstrain meter so that zero on the display corresponds to a non-zerosignal, such as 4 mA, 10 mA, or 1 V dc. The adjustment range isnormally expressed in counts.

Zero Offset: 1. The difference expressed in degrees between true zeroand an indication given by a measuring instrument. 2. See ZeroSuppression

Zero Power Resistance: The resistance of a thermistor or RTDelement with no power being dissipated.

Zero Suppression: The span of an indicator or chart recorder may beoffset from zero (zero suppressed) such that neither limit of thespan will be zero. For example, a temperature recorder whichrecords a 100° span from 400° to 500° is said to have 400° zerosuppression.

Zero Voltage Switching: The making or breaking of circuit timed suchthat the transition occurs when the voltage wave form crosses zerovoltage; typically only found in solid state switching devices.


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Practical Guidelines forTemperature MeasurementTemperature can be measured via adiverse array of sensors. All of theminfer temperature by sensing somechange in a physical characteristic.Six types with which the engineer islikely to come into contact are:thermocouples, resistancetemperature devices (RTD’s andthermistors), infrared radiators,bimetallic devices, liquid expansiondevices, and change-of-statedevices. It is well to begin with abrief review of each.

Thermocouples consist essentiallyof two strips or wires made ofdifferent metals and joined at oneend. As discussed later, changes inthe temperature at that junctureinduce a change in electromotiveforce (emf) between the other ends.As temperature goes up, this outputemf of the thermocouple rises,though not necessarily linearly.

Resistance temperature devicescapitalize on the fact that theelectrical resistance of a materialchanges as its temperaturechanges. Two key types are themetallic devices (commonly referredto as RTD’s), and thermistors. Astheir name indicates, RTD’s rely onresistance change in a metal, withthe resistance rising more or lesslinearly with temperature.Thermistors are based onresistance change in a ceramicsemiconductor; the resistance dropsnonlinearly with temperature rise.

Infrared sensors are noncontactingdevices. As discussed later, they infertemperature by measuring the thermalradiation emitted by a material.

Bimetallic devices take advantage ofthe difference in rate of thermalexpansion between different metals.Strips of two metals are bondedtogether. When heated, one side willexpand more than the other, and theresulting bending is translated into atemperature reading by mechanicallinkage to a pointer. These devicesare portable and they do not requirea power supply, but they are usuallynot as accurate as thermocouplesor RTD’s and they do not readilylend themselves to temperaturerecording.

Fluid-expansion devices, typified by the household thermometer,generally come in two main

classifications: the mercury type andthe organic-liquid type. Versionsemploying gas instead of liquid arealso available. Mercury isconsidered an environmentalhazard, so there are regulationsgoverning the shipment of devicesthat contain it. Fluid-expansionsensors do not require electricpower, do not pose explosionhazards, and are stable even afterrepeated cycling. On the other hand,they do not generate data that areeasily recorded or transmitted, andthey cannot make spot or pointmeasurements.

Change-of-state temperaturesensors consist of labels, pellets,crayons, lacquers or liquid crystalswhose appearance changes when acertain temperature is reached.They are used, for instance, withsteam traps – when a trap exceedsa certain temperature, a white doton a sensor label attached to thetrap will turn black.

Response time typically takesminutes, so these devices often do not respond to transienttemperature changes, and accuracyis lower than with other types ofsensors. Furthermore, the change instate is irreversible, except in thecase of liquid-crystal displays. Evenso, change-of-state sensors can behandy when one needs confirmationthat the temperature of a piece ofequipment or a material has notexceeded a certain level, forinstance for technical or legalreasons, during product shipment.

The workhorsesIn the chemical process industries,the most commonly used temperaturesensors are thermocouples, resistivedevices and infrared devices. Thereis widespread misunderstanding asto how these devices work and howthey should be used.

Thermocouples: Consider first thethermocouple, probably the most-often-used and least-understood ofthe three. Essentially, a thermocoupleconsists of two alloys joinedtogether at one end and open at theother. The emf at the output end (theopen end; V1 in Figure 1a) is afunction of the temperature T1 at theclosed end. As the temperaturerises, the emf goes up.

Often the thermocouple is locatedinside a metal or ceramic shield thatprotects it from a variety ofenvironments. Metal-sheathedthermocouples are also availablewith many types of outer coatings,such as polytetrafluoroethylene, fortrouble-free use in corrosivesolutions.

The open-end emf is a function ofnot only the closed-end temperature(i.e., the temperature at the point ofmeasurement) but also thetemperature at the open end (T2 inFigure 1a). Only by holding T2 at astandard temperature can themeasured emf be considered adirect function of the change in T1.The industrially accepted standardfor T2 is 0°C; therefore, most tablesand charts make the assumptionthat T2 is at that level. In industrialinstrumentation, the differencebetween the actual temperature atT2 and 0°C is usually corrected forelectronically, within theinstrumentation. This emfadjustment is referred to as thecold-junction, or CJ, correction.

Temperature changes in the wiringbetween the input and output endsdo not affect the output voltage,provided that the wiring is ofthermocouple alloy or athermoelectric equivalent (Figure1a). For example, if a thermocoupleis measuring temperature in afurnace and the instrument thatshows the reading is some distanceaway, the wiring between the twocould pass near another furnaceand not be affected by itstemperature, unless it becomes hotenough to melt the wire orpermanently change itselectrothermal behavior.

The composition of the junctionitself does not affect thethermocouple action in any way, solong as the temperature, T1, is keptconstant throughout the junctionand the junction material iselectrically conductive (Figure 1b).Similarly, the reading is not affectedby insertion of non-thermocouplealloys in either or both leads,provided that the temperature at theends of the “spurious” material is thesame (Figure 1c).

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This ability of the thermocouple towork with a spurious metal in thetransmission path enables the useof a number of specialized devices,such as thermocouple switches.Whereas the transmission wiringitself is normally the thermoelectricalequivalent of the thermocouple alloy,properly operating thermocoupleswitches must be made of gold-plated or silver-plated copper alloyelements with appropriate steelsprings to ensure good contact. Solong as the temperatures at theinput and output junctions of theswitch are equal, this change incomposition makes no difference.

It is important to be aware of whatmight be called the Law ofSuccessive Thermocouples. Of thetwo elements that are shown in theupper portion of Figure 1d, onethermocouple has T1 at the hot endand T2 at the open end. The secondthermocouple has its hot end at T2and its open end at T3. The emf levelfor the thermocouple that ismeasuring T1 is V1; that for the otherthermocouple is V2. The sum of thetwo emfs, V1 plus V2, equals the emfV3 that would be generated by thecombined thermocouple operatingbetween T1 and T3. By virtue of thislaw, a thermocouple designated forone open-end referencetemperature can be used with adifferent open-end temperature.

RTD’s: A typical RTD consists of afine platinum wire wrapped around amandrel and covered with a

protective coating. Usually, themandrel and coating are glass orceramic.

The mean slope of the resistancevs. temperature plot for the RTD isoften referred to as the alpha value(Figure 2), alpha standing for thetemperature coefficient. The slope ofthe curve for a given sensordepends somewhat on the purity ofthe platinum in it.

The most commonly used standardslope, pertaining to platinum of aparticular purity and composition,has a value of 0.00385 (assumingthat the resistance is measured inohms and the temperature indegrees Celsius). A resistance vs.temperature curve drawn with thisslope is a so-called European curve,because RTD’s of this compositionwere first used extensively on thatcontinent. Complicating the picture,there is also another standardslope, pertaining to a slightlydifferent platinum composition.Having a slightly higher alpha valueof 0.00392, it follows what is knownas the American curve.

If the alpha value for a given RTD isnot specified, it is usually 0.00385.However, it is prudent to make sureof this, especially if the temperaturesto be measured are high. This pointis brought out in Figure 2, whichshows both the European andAmerican curves for the most widelyused RTD, namely one that exhibits100 ohms resistance at 0°C.

Thermistors: The resistance-temperature relationship of athermistor is negative and highlynonlinear. This poses a seriousproblem for engineers who mustdesign their own circuitry. However,the difficulty can be eased by usingthermistors in matched pairs, in sucha way that the nonlinearities offseteach other. Furthermore, vendorsoffer panel meters and controllersthat compensate internally forthermistors’ lack of linearity.

Thermistors are usually designatedin accordance with their resistanceat 25°C. The most common of theseratings is 2252 ohms; among theothers are 5,000 and 10,000 ohms.If not specified to the contrary, mostinstruments will accept the 2252type of thermistor.

B

A

T1

T3

T2

V1

(a)

T1

T1

T2

V1

(b)

T1

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E

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T1

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(c)

T3

B

C C

(d)

T1B

A

T2

V1

T2E

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T3

V2

T1T2

V1 T3 = V1+ V2

T3

A

B

E

D

Figure 1. Assuming thatcertain conditions aremet (text), thermocoupleperformance is notaffected by temperaturechanges in wiring (a), thecomposition of the junction (b), nor the insertion ofnon-thermocouple alloysin the leads (c). As alsodiscussed in text,thermocouple readingscan be additive (d).

Figure 1a

Figure 1b

Figure 1c

Figure 1d

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Infrared sensors: These measurethe amount of radiation emitted by asurface. Electromagnetic energyradiates from all matter regardlessof its temperature. In many processsituations, the energy is in the infraredregion. As the temperature goes up,the amount of infrared radiation andits average frequency go up.

Different materials radiate atdifferent levels of efficiency. Thisefficiency is quantified as emissivity,a decimal number or percentageranging between 0 and 1 or 0% and100%. Most organic materials,including skin, are very efficient,frequently exhibiting emissivities of0.95. Most polished metals, on theother hand, tend to be inefficientradiators at room temperature, withemissivity or efficiency often 20% orless.

To function properly, an infraredmeasurement device must take intoaccount the emissivity of the surfacebeing measured. This can often belooked up in a reference table.However, bear in mind that tablescannot account for localizedconditions such as oxidation andsurface roughness. A sometimespractical way to measuretemperature with infrared when theemissivity level is not known is to

“force” the emissivity to a knownlevel, by covering the surface withmasking tape (emissivity of 95%) ora highly emissive paint.

Some of the sensor input may wellconsist of energy that is not emittedby the equipment or material whosesurface is being targeted, butinstead is being reflected by thatsurface from other equipment ormaterials. Emissivity pertains toenergy radiating from a surface,whereas “reflection” pertains toenergy reflected from anothersource. Emissivity of an opaquematerial is an inverse indicator of itsreflectivity – substances that aregood emitters do not reflect muchincident energy, and thus do notpose much of a problem to thesensor in determining surfacetemperatures. Conversely, when onemeasures a target surface with only,say, 20% emissivity, much of theenergy reaching the sensor mightbe due to reflection from, e.g., anearby furnace at some othertemperature. In short, be wary ofhot, spurious reflected targets.

An infrared device is like a camera,and thus covers a certain field ofview. It might, for instance, be ableto “see” a 1-degree visual cone or a100-degree cone. When measuring

Figure 2. A given RTD embodies either of two standard resistance-vs.-temperaturerelationships, often referred to as alpha values. The wise engineer will not use an RTD,especially for high-temperature measurements, without being aware of its alpha value

α = .00392(American Curve)

α = .00385(European Curve)

Temperature

100ohms

0°C

Res

ista

nce

a surface, be sure that the surfacecompletely fills the field of view. Ifthe target surface does not at first fillthe field of view, move closer, or usean instrument with a more narrowfield of view. Or, simply take thebackground temperature intoaccount (i.e., adjust for it) whenreading the instrument.

Selection guidesRTD’s are more stable thanthermocouples. On the other hand,as a class, their temperature range isnot as broad: RTD’s operate fromabout -250 to 850°C, whereasthermocouples range from about-270 to 2,300°C. Thermistors have amore restrictive span, beingcommonly used between -40 and150°C, but offer high accuracy in thatrange.

Thermistors and RTD’s share a veryimportant limitation. They areresistive devices, and accordinglythey function by passing a currentthrough a sensor. Even though only avery small current is generallyemployed, it creates a certainamount of heat and thus can throwoff the temperature reading. This self-heating in resistive sensors can besignificant when dealing with a stillfluid (i.e., one that is neither flowingnor agitated), because there is lesscarry-off of the heat generated. Thisproblem does not arise withthermocouples, which are essentiallyzero-current devices.

Infrared sensors, though relativelyexpensive, are appropriate when thetemperatures are extremely high.They are available for up to 3,000°C(5,400°F), far exceeding the range ofthermocouples or other contactdevices.

The infrared approach is alsoattractive when one does not wish tomake contact with the surface whosetemperature is to be measured.Thus, fragile or wet surfaces, such aspainted surfaces coming out of adrying oven, can be monitored in thisway. Substances that are chemicallyreactive or electrically noisy are idealcandidates for infraredmeasurement. The approach islikewise advantageous in measuringtemperature of very large surfaces,such as walls, that would require alarge array of thermocouples orRTD’s for measurement.

®

Practical Guidelines forTemperature Measurement Cont'd

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Property J J, C, T T K, E K N N R J R,E B BIron Constantan Copper Chromel Alumel Nicrosil Nisil Pt13% Rh Pt10% Rh Platinum Pt30% Rh Pt6% Rh

Melting point(solidus temp.)°C 1490 1220 1083 1427 1399 1420 1330 1860 1850 1769 1927 1826°F 2715 2228 1981 2600 2550 2590 2425 3380 3362 3216 3501 3319

ResistivityµΩ·cm 8.57 48.9 1.56 70 28.1 97.4 32.5 19.0 18.4 9.83

at 0°C 9.67 48.9 1.724 70.6 29.4 97.8 34.6 19.6 18.9 10.4 19.0 17.5at 20°C 51.5 294.2 9.38 421 169 114.3 110.7 59.1

Ω cmil/ft 58.2 294 10.37 425 177 117.7 114.0 62.4 114.5 106at 0°Cat 20°C

Temperaturecoefficient of 65 x 10-4 -0.1 x 10-4 4.3 x 10-4 4.1 x 10-4 23.9 x 10-4 13.3 x 10-4 12.1 x 10-4 15.6 x 10-4 16.6 x 10-4 39.2 x 10-4 13.3 x 10-4 20.6 x 10-4

resistance, Ω/Ω·°C (0 to 100°C)

Coefficient ofthermal expansion 11.7 x 10-6 14.9 x 10-6 16.6 x 10-6 13.1 x 10-6 12.0 x 10-6 9.0 x 10-6 9.0 x 10-6 9.0 x 10-6

in./in. °C(20 to 100°C)

Thermal conductivityat 100°C

Cal·cm/s·cm 2·°C 0.162 0.0506 0.901 0.046 0.071 0.0358 0.0664 0.088 0.090 0.171BTU·ft/h·ft 2·°F 39.2 12.2 218 11.1 17.2 8.67 16.07 21.3 21.8 41.4

Specific heat at20°C, cal/ 0.107 0.094 0.092 0.107 0.125 0.11 0.12 0.032g·°C 8.52 8.70

Density 8.73g/cm 3 7.86 8.92 8.92 0.315 8.60 0.3143 19.61 19.97 21.45 17.60 20.55lb/in 3 0.284 0.322 0.322 0.311 0.3078 0.708 0.721 0.775 0.636 0.743

Tensile strength(annealed) MPa 345 552 241 655 586 690 621 317 310 138 483 276

psi 50,000 80,000 35,000 95,000 85,000 100,000 90,000 46,000 45,000 20,000 70,000 40,000

Magnetic attraction strong none none none moderate none none none none none none none

Thermoelement Material

Physical Properties ofThermoelement Materials

aTypes JN, TN and EN thermoelements usually contain small amounts of various elements for control of thermal emf, with corresponding reductions in the nickel or copper content, or both.bThemoelectric iron ((JP) contains small but varying amounts of these elements.

Nominal Chemical Composition of Thermoelements

N=Neg JN,TN KP, RN,P=Pos JP ENa TP EP KN NP NN RP SP SN BP BNElementNominal Chemical Composition, %

Iron 99.5 … … … … … … … … … … …Carbon b … … … … … … … … … … …Manganese b … … … 2 … … … … … … …Sulfur b … … … … … … … … … … …Phosphorus b … … … … … … … … … … …Silicon b … … … 1 1.4 4.4 … … … … …Nickel b 45 … 90 95 84.4 95.5 … … … … …Copper b 55 100 … … … … … … … … …Chromium b … … 10 … 14.2 … … … … … …Aluminum … … … … 2 … … … … … … …Platinum … … … … … … … 87 90 100 70.4 93.9Rhodium … … … … … … … 13 10 … 29.6 6.1Magnesium … … … … … … 0.15 … … … … …

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The metallic sheath on the outsideof an OMEGACLAD® probe is usedto protect the internal thermocouplewires from chemically activeatmospheres. In some cases, evenhot air can damage thermocouplewires and cause them topermanently lose calibration.Selection of the best type of metalsheath to employ is based on ourcustomers’ intended use, theindustry in which they work, and thecountry where they are located. Forinstance, the most commonOMEGA® metal sheaths are 304stainless steel and Inconel 600.These are accepted in mostindustries, including foodprocessing. Stainless steel 304 is acommon alloy, readily available andlow in the cost of both materials andmanufacture. Some industries,however, such as petroleum,medical, nuclear, aircraft, and powergeneration, have their ownstandards and may require morecomplicated and expensive alloys.

Listed below are the sheath materialsthat OMEGA Engineering uses tomake OMEGACLAD®. Any materialsnot on this list must be customized;direct inquiries will have to made toOMEGA South for pricing, availabilityand size limitations.

304 Stainless SteelOMEGA Engineering uses a low-carbon version of 304 stainless,called 304L, mainly because it iseasier to weld. In general, it isinterchangeable with plain 304.

Applications:Food & beverage processingChemical processingDairyHospital equipmentPharmaceutical equipmentNuclear reactor equipmentContainers for mild corrosives

Temperature limitations: up to1,600°F for cyclic processes.Use Inconel 600 for extended usearound or above 1,650°F

Inconel 600This high nickel and chromiumcontent alloy is more expensivethan most stainless steels. It is goodfor extended use at hightemperatures and resists corrosionby most simple acids and very purewater.

Applications:Furnace componentsChemical & food processingNuclear power generationCaustic chemicals

Temperature limitations:up to 2,100°F

OMEGA SUPERCLAD™This alloy has excellent resistanceto air at high temperatures. It has analuminum oxide layer on the surfacethat prevents further oxidation. Thisoxidation resistance allowsthermocouple probes to operate forextended periods before EMF drift“decalibrates” the thermocouple. Itis also popular for its resistance tohydrogen gas and its high strengthat high temperatures. Because ofform limitations and difficulty inprocessing, it is more expensivethan any of the alloys discussedabove.

Applications:Furnace componentsGas turbine industryCatalytic converter componentsAerospace jet & rocket enginesRefractory anchorsWaste incinerators

Temperature limitations:Approx. 2,220°FAlso is acceptable in heated hydrogen, ≈ 2000°F

OMEGACLAD ® SHEATHSELECTION GUIDEAPPLICATIONSU Heat Treating Metal PartsU Gas or Oil Fired FurnacesU Fuel Fired Heat ExchangersU Ceramic Materials FiringU Powder Metal SinteringU Steel Carburizing FurnacesU Vacuum/Atmosphere

Melting & AnnealingU Solid Waste IncineratorsU Heat Process Fluidized BedsU R&D Tube or Box Furnaces

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310 Stainless SteelThis is commonly used at highertemperatures because it resistsscaling up to 1,900°F. It is strongerand resists air attack better than304SS at these highertemperatures. Also good in fossilfuel gases at elevatedtemperatures.

Applications: (Higher temperatures)Air heatersBaking equipmentChemical processing equipmentFurnace partsHeat exchangers and electricpower equipment (that does notcome in contact with sulphur)Petroleum refining


316 (& 316L) Stainless SteelBetter corrosion resistance to mostchemicals, salts, and acids thanmost stainless steels due to theaddition of molybdenum. It has goodresistance to sulphur- or chlorine-bearing liquids.

Applications:Marine trim exteriorsChemical and food processingPetroleum refining equipmentPharmaceutical equipmentPaper & pulpTextile finishing

Temperature limitations:up to 1,600°F continuously in air orin cyclic corrosive environments,slightly higher in air.

321 Stainless SteelThis alloy is similar to 304 stainlessexcept that it incorporates titanium.It is intended for weldedcomponents that are exposed tohigh temperatures, and is especiallywell suited to long exposure to airand combustion atmospheres ofaround 800°F.

Applications:Aircraft exhausts & manifoldsJet engine partsStack linersWelded equipmentChemical processing equipment


Hastelloy-XThis alloy is expensive due to theaddition of iron, chromium andmolybdenum. It has very good hightemperature strength and goodoxidation resistance. It is a relativelyold alloy, less costly and with betterperformance than some neweralloys.

Applications:Gas Turbines for powergenerationAerospace applicationsIndustrial furnacesBoiler & pressure vessels


SUPER OMEGACLAD ® SHEATH

CERAMICINSULATION

THERMOCOUPLEWIRE

Thermocouple Wire Stripper for OMEGACLAD® wire. See PST Series Strippers in Section H.

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Practical Temperature Measurements*

Self-powered Most stable High output Most linear Simple Most accurate Fast Highest output Rugged More linear than Two-wire ohms Inexpensive Inexpensive thermocouple measurement Wide variety Wide temperature

range

Non-linear Expensive Non-linear T<200°C Low voltage Current source re- Limited temperature Power supply re- Reference required quired range quired Least stable Small ∆ R Fragile Slow Least sensitive Low absolute Current source re- Self-heating

resistance quired Limited configurations Self-heating Self-heatingDi

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Adva

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TABLE OF CONTENTSAPPLICATION NOTES-PRACTICAL TEMPERATURE MEASUREMENTS

Figure 1

Page

Common Temperature Transducers ....................................................................................Z-19

Introduction ...........................................................................................................................Z-20Reference Temperatures ...................................................................................................Z-21

The Thermocouple ................................................................................................................Z-21Reference Junction............................................................................................................Z-22Reference Circuit ...............................................................................................................Z-23Hardware Compensation...................................................................................................Z-24Voltage-to-Temperature Conversion ..................................................................................Z-25

Practical Thermocouple Measurement ...............................................................................Z-27Noise Rejection .................................................................................................................Z-27Poor Junction Connection..................................................................................................Z-29Decalibration......................................................................................................................Z-29Shunt Impedance ..............................................................................................................Z-29Galvanic Action..................................................................................................................Z-30Thermal Shunting ..............................................................................................................Z-30Wire Calibration .................................................................................................................Z-30Diagnostics ........................................................................................................................Z-31Summary ...........................................................................................................................Z-32

The RTD .................................................................................................................................Z-33History ...............................................................................................................................Z-33Metal Film RTD's ...............................................................................................................Z-33Resistance Measurement..................................................................................................Z-343-Wire Bridge Measurement Errors...................................................................................Z-35Resistance to Temperature Conversion.............................................................................Z-35Practical Precautions.........................................................................................................Z-36

TEMPERATURE

RE

SIS

TAN

CE

R

T

V

TEMPERATURE

VO

LTA

GE

T TEMPERATURE

RE

SIS

TAN

CE

R

TTEMPERATURE

VO

LTA

GE

T

or C

UR

RE

NT

V or I

*Courtesy Hewlett Packard Company

Thermocouple RTD Thermistor I. C. Sensor

Z-20

Z

The Thermistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Z-36Linear Thermistors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Z-37Measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Z-37

Monolithic Linear Temperature Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Z-37Appendix A-The Empirical Laws of Thermocouples . . . . . . . . . . . . . . . . . . . . . . . . . . . . Z-37Appendix B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Z-38

Thermocouple Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Z-38Base Metal Thermocouples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Z-38

Standard Wire Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Z-39Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Z-40

TABLE OF CONTENTSAPPLICATION NOTES-PRACTICAL TEMPERATURE MEASUREMENTS

Synthetic fuel research, solar energy conversion andnew engine development are but a few of the burgeo-ning disciplines responding to the state of our dwindlingnatural resources. As all industries place new emphasison energy efficiency, the fundamental measurement oftemperature assumes new importance. The purpose of this application note is to explore the more commontemperature monitoring techniques and introduce procedures for improving their accuracy.

We will focus on the four most common tem-perature transducers: the thermocouple, the RTD, thethermistor and the integrated circuit sensor. Despite thewidespread popularity of the thermocouple, it is fre-quently misused. For this reason, we will concentrateprimarily on thermocouple measurement techniques.

Appendix A contains the empirical laws of ther-mocouples which are the basis for all derivations usedherein. Readers wishing a more thorough discussion ofthermocouple theory are invited to read REFERENCE 17 in the Bibliography.

For those with a specific thermocouple applica-tion, Appendix B may aid in choosing the best typeof thermocouple.

Throughout this application note, we will emphasizethe practical considerations of transducer placement,signal conditioning and instrumentation.

Early Measuring Devices - Galileo is credited withinventing the thermometer, circa 1592.1 In an opencontainer filled with colored alcohol he suspended along narrow-throated glass tube, at the upper end ofwhich was a hollow sphere. When heated, the air inthe sphere expanded and bubbled through the liquid.Cooling the sphere caused the liquid to move up the tube1 Fluctuations in the temperature of the sphere could then be observed by noting the position of the liquid inside the tube. This "upside-down" ther-mometer was a poor indicator since the level changedwith barometric pressure and the tube had no scale.Vast improvements were made in temperaturemeasurement accuracy with the development of the

1 Refer to Bibliography 1,2,3.

Florentine thermometer, which incorporated sealedconstruction and a graduated scale.

In the ensuing decades, many thermometric scaleswere conceived, all based on two or more fixed pointsOne scale, however, wasn't universally recognized un-til the early 1700's, when Gabriel Fahrenheit, a Dutchinstrument maker, produced accurate and repeatablemercury thermometers. For the fixed point on the lowend of his temperature scale, Fahrenheit used a mix-ture of ice water and salt (or ammonium chloride). Thiswas the lowest temperature he could reproduce, and helabeled it "zero degrees". For the high end of his scale,he chose human blood temperature and called it 96degrees.

Why 96 and not 100 degrees? Earlier scales hadbeen divided into twelve parts. Fahrenheit, in an ap-parent quest for more resolution divided his scale into24, then 48 and eventually 96 parts.

The Fahrenheit scale gained popularity primarilybecause of the repeatability and quality of the ther-mometers that Fahrenheit built.

Around 1742, Anders Celsius proposed that themelting point of ice and the boiling point of water beused for the two benchmarks. Celsius selected zerodegrees as the boiling point and 100 degrees as themelting point. Later, the end points were reversed andthe centigrade scale was born. In 1948 the name wasofficially changed to the Celsius scale.

In the early 1800's William Thomson (Lord Kelvin),developed a universal thermodynamic scale basedupon the coefficient of expansion of an ideal gas. Kelvinestablished the concept of absolute zero and his scaleremains the standard for modern thermometry.

The conversion equations for the four moderntemperature scales are:

°C = 5/9 (°F - 32) °F= 9/5 °C + 32

K = °C + 273.15 °R= °F + 459.67The Rankine Scale (ºR) is simply the Fahrenheit

equivalent of the Kelvin scale, and was named after anearly pioneer in the field of thermodynamics, W.J.M.Rankine.

INTRODUCTION

Z-21

We cannot build a temperature divider as we can avoltage divider, nor can we add temperatures as wewould add lengths to measure distance. We must relyupon temperatures established by physical phenomenawhich are easily observed and consistent in nature. TheInternational Practical Temperature Scale (IPTS) isbased on such phenomena. Revised in 1968, itestablishes eleven reference temperatures.

Since we have only these fixed temperatures to useas a reference, we must use instruments to interpolatebetween them. But accurately interpolating betweenthese temperatures can require some fairly exotictransducers, many of which are too complicated orexpensive to use in a practical situation. We shall limitour discussion to the four most common temperaturetransducers: thermocouples, resistance-temperaturedetector’s (RTD’s), thermistors, and integratedcircuit sensors.

IPTS-68 REFERENCE TEMPERATURESEQUILIBRIUM POINT K 0CTriple Point of Hydrogen 13.81 -259.34

Liquid/Vapor Phase of Hydrogen 17.042 -256.108

at 25/76 Std. Atmosphere

Boiling Point of Hydrogen 20.28 -252.87

Boiling Point of Neon 27.102 -246.048

Triple Point of Oxygen 54.361 -218.789

Boiling Point of Oxygen 90.188 -182.962

Triple Point of Water 273.16 .01

Boiling Point of Water 373.15 100

Freezing Point of Zinc 692.73 419.58

Freezing Point of Silver 1235.08 961.93

Freezing Point of Gold 1337.58 1064.43

Table 1

THE THERMOCOUPLEWhen two wires composed of dissimilar metals are

joined at both ends and one of the ends is heated, thereis a continuous current which flows in the thermoelectriccircuit. Thomas Seebeck made this discovery in 1821.

If this circuit is broken at the center, the net opencircuit voltage (the Seebeck voltage) is a function of thejunction temperature and the composition of the twometals.

All dissimilar metals exhibit this effect. The mostcommon combinations of two metals are listed inAppendix B of this application note, along with theirimportant characteristics. For small changes intemperature the Seebeck voltage is linearly proportionalto temperature:

∆eAB = α∆T Where α, the Seebeck coefficient, is the constant ofproportionality.

Measuring Thermocouple Voltage - We can’tmeasure the Seebeck voltage directly because we mustfirst connect a voltmeter to the thermocouple, and thevoltmeter leads themselves create a newthermoelectric circuit.

Let’s connect a voltmeter across a copper-constantan(Type T) thermocouple and look at the voltage output:

We would like the voltmeter to read only V1, but byconnecting the voltmeter in an attempt to measure theoutput of Junction J1, we have created two moremetallic junctions: J2 and J3. Since J3 is a copper-to-copper junction, it creates no thermal EMF (V3 = 0), butJ2 is a copper-to-constantan junction which will add anEMF (V2) in opposition to V1. The resultant voltmeterreading V will be proportional to the temperaturedifference between J1 and J2. This says that we can’tfind the temperature at J1 unless we first find thetemperature of J2.

Reference Temperatures

Metal A

Metal B

eAB

+

–

J1

–V2

+

–

+

–V1

+

J2

J1

+

–

Fe

v

Fe

Cu

Cu

Cu

C

J1

–V2

+

–V1

+

J2

EQUIVALENT CIRCUITS

–V3

+

J3

V3 = 0

Cu

Cu C

Cu

Cu C

Cu

J2

J3

V1

MEASURING JUNCTION VOLTAGE WITH A DVMFigure 4

eAB = SEEBECK VOLTAGEFigure 3

Metal A Metal C

Metal BTHE SEEBECK EFFECT

Figure 2

Z-22

Z

One way to determine the temperature of J2 is tophysically put the junction into an ice bath, forcing itstemperature to be 0ºC and establishing J2 as theReference Junction. Since both voltmeter terminaljunctions are now copper-copper, they create nothermal emf and the reading V on the voltmeter isproportional to the temperature difference between J1and J2.

Now the voltmeter reading is (see Figure 5):V = (V1 - V2) ≅ α (tJ1

- tJ2)

If we specify TJ1in degrees Celsius:

TJ1(ºC) + 273.15 = tJ1

then V becomes:V = V1 - V2 = α [(TJ1

+ 273.15) - (TJ2+ 273.15)]

= α (TJ1- TJ2

) = α (TJ1- 0)

V = αTJ1

We use this protracted derivation to emphasize thatthe ice bath junction output, V2, is not zero volts. It is afunction of absolute temperature.

By adding the voltage of the ice point referencejunction, we have now referenced the reading V to 0ºC.This method is very accurate because the ice pointtemperature can be precisely controlled. The ice point isused by the National Bureau of Standards (NBS) as thefundamental reference point for their thermocoupletables, so we can now look at the NBS tables anddirectly convert from voltage V to Temperature TJ1

.

The copper-constantan thermocouple shown inFigure 5 is a unique example because the copper wireis the same metal as the voltmeter terminals. Let’s usean iron-constantan (Type J) thermocouple instead of thecopper-constantan. The iron wire (Figure 6) increasesthe number of dissimilar metal junctions in the circuit, asboth voltmeter terminals become Cu-Fe thermocouplejunctions.

EXTERNAL REFERENCE JUNCTIONFigure 5

The Reference Junction

J1

+

–

J4

J3Fe

C

v

Ice Bath

Fe

Cu

Cu

J2

V1 = Vif V = Vi.e., ifTJ3

= TJ4

Voltmeter

+

–v V1

V3

V4

J3

J4

+-

+-

3 4

+

–T1

V2

Fev

Ice Bath

Cu

Cu

Voltmeter

C

TREF

Fe

J3

J4

Cu

Cu

Isothermal Block

J1

–V2

+

–

v

T=0°C

+

–V1

+ T

J2

–

+J1V1

V2

–+

+

–

Cu

C

v

Ice Bath

Cu

Cu

Cu

J2

Voltmeter

REMOVING JUNCTIONS FROM DVM TERMINALSFigure 8

IRON-CONSTANTAN COUPLEFigure 6

If both front panel terminals are not at the sametemperature, there will be an error. For a more precisemeasurement, the copper voltmeter leads should beextended so the copper-to-iron junctions are made onan isothermal (same temperature) block:

The isothermal block is an electrical insulator but agood heat conductor, and it serves to hold J3 and J4 atthe same temperature. The absolute block temperatureis unimportant because the two Cu-Fe junctions act inopposition. We still have

V = α (T1 - TREF)

JUNCTION VOLTAGE CANCELLATIONFigure 7

Let’s replace the ice bath with another isothermalblock

The new block is at Reference Temperature TREF, andbecause J3 and J4 are still at the same temperature, wecan again show that

V = α (T1-TREF)

This is still a rather inconvenient circuit because wehave to connect two thermocouples. Let’s eliminate theextra Fe wire in the negative (LO) lead by combining theCu-Fe junction (J4) and the Fe-C junction (JREF).

We can do this by first joining the two isothermalblocks (Figure 9b).

We haven’t changed the output voltage V. It is still

V = α (TJ1 - TJREF )

Now we call upon the law of intermediate metals (seeAppendix A) to eliminate the extra junction. Thisempirical “law” states that a third metal (in this case,iron) inserted between the two dissimilar metals of athermocouple junction will have no effect upon theoutput voltage as long as the two junctions formed bythe additional metal are at the same temperature:

This is a useful conclusion, as it completely eliminatesthe need for the iron (Fe) wire in the LO lead:

Again, V = α (TJ1 - TREF), where α is the Seebeckcoefficient for an Fe-C thermocouple.|

Junctions J3 and J4, take the place of the ice bath.These two junctions now become the ReferenceJunction.

Now we can proceed to the next logical step: Directlymeasure the temperature of the isothermal block (theReference Junction) and use that information tocompute the unknown temperature, TJ1.

A thermistor, whose resistance RT is a function oftemperature, provides us with a way to measure theabsolute temperature of the reference junction.Junctions J3 and J4 and the thermistor are all assumedto be at the same temperature, due to the design of theisothermal block. Using a digital multimeter undercomputer control, we simply:

1) Measure RT to find TREF and convert TREF

to its equivalent reference junction voltage, VREF , then

2) Measure V and subtract VREF to find V1,and convert V1 to temperature TJ1

.

This procedure is known as Software Compensationbecause it relies upon the software of a computer tocompensate for the effect of the reference junction. Theisothermal terminal block temperature sensor can beany device which has a characteristic proportional toabsolute temperature: an RTD, a thermistor, or anintegrated circuit sensor.

It seems logical to ask: If we already have a devicethat will measure absolute temperature (like an RTD orthermistor), why do we even bother with a thermocouplethat requires reference junction compensation? The

Z-23

Reference Circuit

J3

J4

Cu

CuJ1

C

T REF

Fe

–

+v

J3

J4

Cu

CuVoltmeter

HI

LO

Isothermal Block

J1

C

T REF Isothermal Block

J REF

Fe

Fe

J3

J4

Cu

Cu

J1

C

Isothermal Bloc k @ T REF

J REF

Fe

Fe

HI

LO +

–J1

+

–V1v

Voltmeter

C

FeJ3

RT

Cu

Cu

Block Temperature = TREF

J4

Isothermal Connection

T REF

T REF

Thus the low lead in Fig. 9b: Becomes:

Metal A Metal CMetal B =Metal CMetal A

Cu CFe =CCu

ELIMINATING THE ICE BATHFigure 9a

JOINING THE ISOTHERMAL BLOCKSFigure 9b

LAW OF INTERMEDIATE METALSFigure 10

EQUIVALENT CIRCUITFigure 11

EXTERNAL REFERENCE JUNCTION-NO ICE BATHFigure 12

Z-24

Z

single most important answer to this question is that thethermistor, the RTD, and the integrated circuittransducer are only useful over a certain temperaturerange. Thermocouples, on the other hand, can be usedover a range of temperatures, and optimized for variousatmospheres. They are much more rugged thanthermistors, as evidenced by the fact thatthermocouples are often welded to a metal part orclamped under a screw. They can be manufactured onthe spot, either by soldering or welding. In short,thermocouples are the most versatile temperaturetransducers available and, since the measurementsystem performs the entire task of referencecompensation and software voltage to-temperatureconversion, using a thermocouple becomes as easy asconnecting a pair of wires.

Thermocouple measurement becomes especiallyconvenient when we are required to monitor a largenumber of data points. This is accomplished by usingthe isothermal reference junction for more than onethermocouple element (see Figure 13).

A reed relay scanner connects the voltmeter to thevarious thermocouples in sequence. All of the voltmeterand scanner wires are copper, independent of the typeof thermocouple chosen. In fact, as long as we knowwhat each thermocouple is, we can mix thermocoupletypes on the same isothermal junction block (oftencalled a zone box) and make the appropriatemodifications in software. The junction blocktemperature sensor RT is located at the center of theblock to minimize errors due to thermal gradients.

Software compensation is the most versatiletechnique we have for measuring thermocouples. Manythermocouples are connected on the same block,copper leads are used throughout the scanner, and thetechnique is independent of the types of thermocoupleschosen. In addition, when using a data acquisitionsystem with a built-in zone box, we simply connect thethermocouple as we would a pair of test leads. All of theconversions are performed by the computer. The onedisadvantage is that the computer requires a smallamount of additional time to calculate the referencejunction temperature. For maximum speed we can usehardware compensation.

Hardware CompensationRather than measuring the temperature of the

reference junction and computing its equivalent voltageas we did with software compensation, we could inserta battery to cancel the offset voltage of the referencejunction. The combination of this hardwarecompensation voltage and the reference junctionvoltage is equal to that of a 0ºC junction.

The compensation voltage, e, is a function of thetemperature sensing resistor, RT. The voltage V is nowreferenced to 0ºC, and may be read directly andconverted to temperature by using the NBS tables.

Another name for this circuit is the electronic ice pointreference.

2 These circuits are commercially available for

use with any voltmeter and with a wide variety ofthermocouples. The major drawback is that a unique icepoint reference circuit is usually needed for eachindividual thermocouple type.

Figure 15 shows a practical ice point reference circuitthat can be used in conjunction with a reed relayscanner to compensate an entire block of thermocoupleinputs. All the thermocouples in the block must be of thesame type, but each block of inputs can accommodatea different thermocouple type by simply changing gainresistors.

Pt

Isothermal Block(Zone Box)

Fe

C

Pt - 10% Rh

RT

All Copper Wires

Voltmeter

HI

LO

+

–

T

Fe

Fe

C

T

Cu

Cu

Fe

C

RT

e

Cu

Cu+–

Cu

+Cu

-

–

+

–

+

v

Fe

Fe

C

T

Fe

+–

Cu

Cu

v

0°C

= =

2 Refer to Bibliography 6.

HARDWARE COMPENSATION CIRCUITFigure 14

ZONE BOX SWITCHINGFigure 13

The advantage of the hardware compensation circuitor electronic ice point reference is that we eliminate theneed to compute the reference temperature. This savesus two computation steps and makes a hardwarecompensation temperature measurement somewhatfaster than a software compensation measurement.

Voltage-To-Temperature ConversionWe have used hardware and software compensation

to synthesize an ice-point reference. Now all we have todo is to read the digital voltmeter and convert thevoltage reading to a temperature. Unfortunately, thetemperature-versus-voltage relationship of athermocouple is not linear. Output voltages for the morecommon thermocouples are plotted as a function oftemperature in Figure 16. If the slope of the curve (theSeebeck coefficient) is plotted vs. temperature, as inFigure 17, it becomes quite obvious that thethermocouple is a non-linear device.

A horizontal line in Figure 17 would indicate aconstant α, in other words, a linear device. We noticethat the slope of the type K thermocouple approaches aconstant over a temperature range from 0ºC to 1000ºC.Consequently, the type K can be used with a multiplyingvoltmeter and an external ice point reference to obtain amoderately accurate direct readout of temperature. Thatis, the temperature display involves only a scale factor.This procedure works with voltmeters.

By examining the variations in Seebeck coefficient,

we can easily see that using one constant scale factorwould limit the temperature range of the system andrestrict the system accuracy. Better conversion accuracycan be obtained by reading the voltmeter and consultingthe National Bureau of Standards ThermocoupleTables3 in Section T of the OMEGA TEMPERATUREMEASUREMENT HANDBOOK - see Table 3.

T = a0 +a1 x + a2x2 + a3x3 . . . +anxn

whereT = Temperaturex = Thermocouple EMF in Voltsa = Polynomial coefficients unique to each

thermocouplen = Maximum order of the polynomialAs n increases, the accuracy of the polynomial

improves. A representative number is n = 9 for ± 1ºCaccuracy. Lower order polynomials may be used over anarrow temperature range to obtain higher systemspeed.

Table 4 is an example of the polynomials used toconvert voltage to temperature. Data may be utilized inpackages for a data acquisition system. Rather thandirectly calculating the exponentials, the computer isprogrammed to use the nested polynomial form to saveexecution time. The polynomial fit rapidly degradesoutside the temperature range shown in Table 4 andshould not be extrapolated outside those limits.

Z-25

0°

Mill

ivo

lts

500° 2000°1500°1000°

Temperature °C

Type Metals+ –

E Chromel vs. ConstantanJ Iron vs. ConstantanK Chromel vs. AlumelR Platinum vs. Platinum

13% RhodiumS Platinum vs. Platinum

10% RhodiumT Copper vs. Constantan

20

40

60

80

R

S

E

J

K

THERMOCOUPLE TEMPERATUREvs.

VOLTAGE GRAPHFigure 16


OMEGA TAC-Electronic Ice Point andThermocouple Preamplifier/Linearizer Plugsinto Standard Connector

OMEGA Ice Point Reference Chamber.Electronic Refigeration Eliminates Ice Bath

PRACTICAL HARDWARE COMPENSATIONFigure 15

Integrated TemperatureSensor

Cu

Cu

RH

Fe

C

TABLE 2

HARDWARE COMPENSATION SOFTWARE COMPENSATION

Fast Requires more computer Restricted to one thermocouple manipulation time

type per card Versatile - accepts any thermocouple

OMEGA Electronic Ice Point Built into Thermocouple Connector -”MCJ”

NBS POLYNOMIAL COEFFICIENTSTable 4

TYPE E TYPE J TYPE K TYPE R TYPE S TYPE T

Nickel-10% Chromium(+) Iron(+) Nickel-10% Chromium(+) Platinum-13% Rhodium(+) Platinum-10% Rhodium(+) Copper(+)

Versus Versus Versus Versus Versus Versus

Constantan(-) Constantan(-) Nickel-5%(-) Platinum(-) Platinum(-) Constantan(-)(Aluminum Silicon)

-100ºC to 1000ºC 0ºC to 760ºC 0ºC to 1370ºC 0ºC to 1000ºC 0ºC to 1750ºC -160ºC to 400ºC± 0.5ºC ± 0.1ºC ± 0.7ºC ± 0.5ºC ± 1ºC ±0.5ºC

9th order 5th order 8th order 8th order 9th order 7th order

0.104967248 -0.048868252 0.226584602 0.263632917 0.927763167 0.100860910

17189.45282 19873.14503 24152.10900 179075.491 169526.5150 25727.94369

-282639. 0850 -218614.5353 67233.4248 -48840341.37 -31568363.94 -767345.8295

12695339.5 11569199.78 2210340.682 1.90002E + 10 8990730663 78025595.81

-448703084.6 -264917531.4 -860963914.9 -4.82704E + 12 -1.63565E + 12 -9247486589

1.10866E + 10 2018441314 4.83506E + 10 7.62091E + 14 1.88027E + 14 6.97688E + 11

-1. 76807E + 11 -1. 18452E + 12 -7.20026E + 16 -1.37241E + 16 -2.66192E + 13

1.71842E + 12 1.38690E + 13 3.71496E + 18 6.17501E + 17 3.94078E + 14

-9.19278E + 12 -6.33708E + 13 -8.03104E + 19 -1.56105E + 19

2.06132E + 13 1.69535E + 20

Z-26

Z

mV .00 .01 .02 .03 .04 .05 .06 .07 .08 .09 .10 mVTEMPERATURES IN DEGREES C (IPTS 1968)

0.00 0.00 0.17 0.34 0.51 0.68 0.85 1.02 1.19 1.36 1.53 1.70 0.000.10 1.70 1.87 2.04 2.21 2.38 2.55 2.72 2.89 3.06 3.23 3.40 0.100.20 3.40 3.57 3.74 3.91 4.08 4.25 4.42 4.58 4.75 4.92 5.09 0.200.30 5.09 5.26 5.43 5.60 5.77 5.94 6.11 6.27 6.44 6.61 6.78 0.300.40 6.78 6.95 7.12 7.29 7.46 7.62 7.79 7.96 8.13 8.30 8.47 0.400.50 8.47 8.63 8.80 8.97 9.14 9.31 9.47 9.64 9.81 9.98 10.15 0.500.60 10.15 10.31 10.48 10.65 10.82 10.98 11.15 11.32 11.49 11.65 11.82 0.600.70 11.82 11.99 12.16 12.32 12.49 12.66 12.83 12.99 13.16 13.33 13.49 0.700.80 13.49 13.66 13.83 13.99 14.16 14.33 14.49 14.66 14.83 14.99 15.16 0.800.90 15.16 15.33 15.49 15.66 15.83 15.99 16.16 16.33 16.49 16.66 16.83 0.901.00 16.83 16.99 17.16 17.32 17.49 17.66 17.82 17.99 18.15 18.32 18.48 1.001.10 18.48 18.65 18.82 18.98 19.15 19.31 19.48 19.64 19.81 19.97 20.14 1.101.20 20.14 20.31 20.47 20.64 20.80 20.97 21.13 21.30 21.46 21.63 21.79 1.201.30 21.79 21.96 22.12 22.29 22.45 22.62 22.78 22.94 23.11 23.27 23.44 1.301.40 23.44 23.60 23.77 23.93 24.10 24.26 24.42 24.59 24.75 24.92 25.08 1.40

The calculation of high-order polynomials is a time-consuming task for a computer. As we mentionedbefore, we can save time by using a lower orderpolynomial for a smaller temperature range. In thesoftware for one data acquisition system, thethermocouple characteristic curve is divided into eightsectors, and each sector is approximated by a third-order polynomial.*

All the foregoing procedures assume thethermocouple voltage can be measured accurately andeasily; however, a quick glance at Table 3 shows us thatthermocouple output voltages are very small indeed.Examine the requirements of the system voltmeter:

THERMOCOUPLE SEEBECK DVM SENSITIVITYTYPE COEFFICIENT FOR 0.1ºC

(µV/º C) @ 20º C (µV)E 62 6.2J 51 5.1K 40 4.0R 7 0.7S 7 0.7T 40 4.0

REQUIRED DVM SENSITIVITY

Table 5

Even for the common type K thermocouple, thevoltmeter must be able to resolve 4 µV to detect a0. 1ºC change. The magnitude of this signal is an openinvitation for noise to creep into any system. For thisreason, instrument designers utilize severalfundamental noise rejection techniques, including treeswitching, normal mode filtering, integration andguarding.

–500°

See

beck

Coe

ffici

ent m

V/°

C

0° 2000°1500°1000°500°Temperature °C

Linear Region(SeeText)

20

40

60

80

100

R

S

K

T J

E

* HEWLETT PACKARD 3054A.

TEMPERATURE CONVERSION EQUATION: T = a0 +a1 x + a2x2 + . . . +anxn

NESTED POLYNOMIAL FORM: T = a0 + x(a1 + x(a2 + x (a3 + x(a4 + a5x)))) (5th order)where x is in Volts, T is in °C

TYPE E THERMOCOUPLETable 3

SEEBECK COEFFICIENT vs. TEMPERATUREFigure 17

aVoltage

Tem

p.

T = bx + cx + dx 2 3

a

a0

a1

a2

a3

a4

a5

a6

a7

a8

a9

CURVE DIVIDED INTO SECTORSFigure 18

Z-27

PRACTICAL THERMOCOUPLE MEASUREMENTNoise Rejection

Tree Switching - Tree switching is a method oforganizing the channels of a scanner into groups, eachwith its own main switch.

Without tree switching, every channel can contributenoise directly through its stray capacitance. With treeswitching, groups of parallel channel capacitances arein series with a single tree switch capacitance. Theresult is greatly reduced crosstalk in a large dataacquisition system, due to the reduced interchannelcapacitance.

Analog Filter - A filter may be used directly at theinput of a voltmeter to reduce noise. It reducesinterference dramatically, but causes the voltmeter torespond more slowly to step inputs.

Integration - Integration is an A/D technique whichessentially averages noise over a full line cycle; thus,power line related noise and its harmonics are virtuallyeliminated. If the integration period is chosen to be lessthan an integer line cycle, its noise rejection propertiesare essentially negated.

Since thermocouple circuits that cover long distancesare especially susceptible to power line related noise, itis advisable to use an integrating analog-to-digitalconverter to measure the thermocouple voltage.Integration is an especially attractive A/D technique inlight of recent innovations which allow reading rates of48 samples per second with full cycle integration.

VIN

t

VOUT

t

Guarding - Guarding is a technique used to reduceinterference from any noise source that is common toboth high and low measurement leads, i.e., fromcommon mode noise sources.

Let’s assume a thermocouple wire has been pulledthrough the same conduit as a 220 Vac supply line. Thecapacitance between the power lines and thethermocouple lines will create an AC signal ofapproximately equal magnitude on both thermocouplewires. This common mode signal is not a problem in anideal circuit, but the voltmeter is not ideal. It has somecapacitance between its low terminal and safety ground(chassis). Current flows through this capacitance andthrough the thermocouple lead resistance, creating anormal mode noise signal. The guard, physically afloating metal box surrounding the entire voltmetercircuit, is connected to a shield surrounding thethermocouple wire, and serves to shunt the interferingcurrent.

= Signal+

–C

~

HI

DVM

NoiseSour ce

(20 Channels)

C

C

C

CTree

Switch1

TreeSwitch2

C

Next 20 Channels

Signal+

–

~

HI

DVM

Stray capacitance to noisesource is reduced nearly20:1 by leaving TreeSwitch 2 open.

NoiseSource

Signal+

–20 C C

~

HI

DVM =~

TREE SWITCHINGFigure 19

ANALOG FILTERFigure 20

Z-28

ZHI

LO

DVM

GuardWithout Guard

HI

LO

DVM

DistributedCapacitance

Without Guard

220 VAC Line

DistributedResistance

Each shielded thermocouple junction can directlycontact an interfering source with no adverse effects,since provision is made on the scanner to switch theguard terminal separately for each thermocouplechannel. This method of connecting the shield to guardserves to eliminate ground loops often created whenthe shields are connected to earth ground.

The dvm guard is especially useful in eliminatingnoise voltages created when the thermocouple junctioncomes into direct contact with a common mode noisesource.

In Figure 22 we want to measure the temperature atthe center of a molten metal bath that is being heatedby electric current. The potential at the center of thebath is 120 V RMS. The equivalent circuit is:

The stray capacitance from the dvm Lo terminal tochassis causes a current to flow in the low lead, whichin turn causes a noise voltage to be dropped across theseries resistance of the thermocouple, Rs. This voltageappears directly across the dvm Hi to Lo terminals andcauses a noisy measurement. If we use a guard leadconnected directly to the thermocouple, we drasticallyreduce the current flowing in the Lo lead. The noisecurrent now flows in the guard lead where it cannotaffect the reading:

Notice that we can also minimize the noise byminimizing Rs. We do this by using larger thermocouplewire that has a smaller series resistance.

To reduce the possibility of magnetically inducednoise, the thermocouple should be twisted in a uniformmanner. Thermocouple extension wires are availablecommercially in a twisted pair configuration.

Practical Precautions - We have discussed theconcepts of the reference junction, how to use apolynomial to extract absolute temperature data, andwhat to look for in a data acquisition system, tominimize the effects of noise. Now let’s look at thethermocouple wire itself. The polynomial curve fit reliesupon the thermocouple wire’s being perfect; that is, itmust not become decalibrated during the act of makinga temperature measurement. We shall now discusssome of the pitfalls of thermocouple thermometry.

Aside from the specified accuracies of the dataacquisition system and its zone box, most measurementerrors may be traced to one of these primary sources:

1. Poor junction connection

2. Decalibration of thermocouple wire

3. Shunt impedance and galvanic action

4. Thermal shunting

5. Noise and leakage currents

6. Thermocouple specifications

7. Documentation

GUARD SHUNTS INTERFERING WITH CURRENTFigure 21

Figure 22

Figure 23

Figure 24

240 VRMS

HI

Noise Current

LO

Guard

RS

120VRMS

Noise Current

LO

HIRS

Z-29

Poor Junction Connection There are a number of acceptable ways to connect

two thermocouple wires: soldering, silver-soldering,welding, etc. When the thermocouple wires aresoldered together, we introduce a third metal into thethermocouple circuit, but as long as the temperatureson both sides of the thermocouple are the same, thesolder should not introduce any error. The solder doeslimit the maximum temperature to which we can subjectthis junction. To reach a higher measurementtemperature, the joint must be welded. But welding isnot a process to be taken lightly.3 Overheating candegrade the wire, and the welding gas and theatmosphere in which the wire is welded can both diffuseinto the thermocouple metal, changing itscharacteristics. The difficulty is compounded by the verydifferent nature of the two metals being joined.Commercial thermocouples are welded on expensivemachinery using a capacitive-discharge technique toinsure uniformity.

A poor weld can, of course, result in an openconnection, which can be detected in a measurementsituation by performing an open thermocouple check.This is a common test function available withdataloggers. While the open thermocouple is theeasiest malfunction to detect, it is not necessarily themost common mode of failure.

Decalibration Decalibration is a far more serious fault condition than

the open thermocouple because it can result in atemperature reading that appears to be correct.Decalibration describes the process of unintentionallyaltering the physical makeup of the thermocouple wireso that it no longer conforms to the NBS polynomialwithin specified limits. Decalibration can result fromdiffusion of atmospheric particles into the metal causedby temperature extremes. It can be caused by hightemperature annealing or by cold-working the metal, aneffect that can occur when the wire is drawn through aconduit or strained by rough handling or vibration.Annealing can occur within the section of wire thatundergoes a temperature gradient.

Robert Moffat in his Gradient Approach toThermocouple Thermometry explains that thethermocouple voltage is actually generated by thesection of wire that contains the temperature gradient,and not necessarily by the junction.4 For example, if wehave a thermal probe located in a molten metal bath,there will be two regions that are virtually isothermaland one that has a large gradient.

In Figure 26, the thermocouple junction will notproduce any part of the output voltage. The shadedsection will be the one producing virtually the entirethermocouple output voltage. If, due to aging orannealing, the output of this thermocouple were found

to be drifting, then replacing the thermocouple junctionalone would not solve the problem. We would have toreplace the entire shaded section, since it is the sourceof the thermocouple voltage.

Thermocouple wire obviously can’t be manufacturedperfectly; there will be some defects which will causeoutput voltage errors. These inhomogeneities can beespecially disruptive if they occur in a region of steeptemperature gradient. Since we don’t know where animperfection will occur within a wire, the best thing wecan do is to avoid creating a steep gradient. Gradientscan be reduced by using metallic sleeving or by carefulplacement of the thermocouple wire.

Shunt ImpedanceHigh temperatures can also take their toll on

thermocouple wire insulators. Insulation resistancedecreases exponentially with increasing temperature,even to the point that it creates a virtual junction.5Assume we have a completely open thermocoupleoperating at a high temperature.

The leakage Resistance, RL, can be sufficiently low tocomplete the circuit path and give us an impropervoltage reading. Now let’s assume the thermocouple isnot open, but we are using a very long section of smalldiameter wire.3 Refer to Bibliography 5

4 Refer to Bibliography 9 5 Refer to Bibliography 7

500˚CMetal Bath

200300400500

100˚C25˚C

Solder (Pb, Sn)

Junction: Fe - Pb, Sn - C = Fe - C

Fe

C

SOLDERING A THERMOCOUPLEFigure 25

GRADIENT PRODUCES VOLTAGEFigure 26

Z-30

Z

If the thermocouple wire is small, its series resistance,RS, will be quite high and under extreme conditions RL

< < RS. This means that the thermocouple junction willappear to be at RL and the output will be proportional toT1 not T2.

High temperatures have other detrimental effects onthermocouple wire. The impurities and chemicals withinthe insulation can actually diffuse into the thermocouplemetal causing the temperature-voltage dependence todeviate from published values. When usingthermocouples at high temperatures, the insulationshould be chosen carefully. Atmospheric effects can beminimized by choosing the proper protective metallic orceramic sheath

Galvanic ActionThe dyes used in some thermocouple insulation will

form an electrolyte in the presence of water. Thiscreates a galvanic action, with a resultant outputhundreds of times greater than the Seebeck effect.Precautions should be taken to shield thermocouplewires from all harsh atmospheres and liquids.

Thermal Shunting No thermocouple can be made without mass. Since it

takes energy to heat any mass, the thermocouple willslightly alter the temperature it is meant to measure. Ifthe mass to be measured is small, the thermocouplemust naturally be small. But a thermocouple made withsmall wire is far more susceptible to the problems ofcontamination, annealing, strain, and shunt impedance.To minimize these effects, thermocouple extension wirecan be used. Extension wire is commercially availablewire primarily intended to cover long distances betweenthe measuring thermocouple and the voltmeter.

Extension wire is made of metals having Seebeckcoefficients very similar to a particular thermocoupletype. It is generally larger in size so that its seriesresistance does not become a factor when traversinglong distances. It can also be pulled more readilythrough a conduit than can very small thermocouple

R LTo DVM

R LTo DVM

R S R S

R S R ST 1

T 2

( )

wire. It generally is specified over a much lowertemperature range than premium grade thermocouplewire. In addition to offering a practical size advantage,extension wire is less expensive than standardthermocouple wire. This is especially true in the case ofplatinum-based thermocouples.

Since the extension wire is specified over a narrowertemperature range and it is more likely to receivemechanical stress, the temperature gradient across theextension wire should be kept to a minimum. This,according to the gradient theory, assures that virtuallynone of the output signal will be affected by theextension wire.

Noise - We have already discussed line-related noiseas it pertains to the data acquisition system. Thetechniques of integration, tree switching and guardingserve to cancel most line-related interference.Broadband noise can be rejected with the analog filter.

The one type of noise the data acquisition systemcannot reject is a dc offset caused by a dc leakagecurrent in the system. While it is less common to see dcleakage currents of sufficient magnitude to causeappreciable error, the possibility of their presenceshould be noted and prevented, especially if thethermocouple wire is very small and the related seriesimpedance is high.

Wire CalibrationThermocouple wire is manufactured to a certain

specification, signifying its conformance with the NBStables. The specification can sometimes be enhancedby calibrating the wire (testing it at knowntemperatures). Consecutive pieces of wire on acontinuous spool will generally track each other moreclosely than the specified tolerance, although theiroutput voltages may be slightly removed from the centerof the absolute specification.

If the wire is calibrated in an effort to improve itsfundamental specifications, it becomes even moreimperative that all of the aforementioned conditions beheeded in order to avoid decalibration.

LEAKAGE RESISTANCEFigure 27

VIRTUAL JUNCTIONFigure 28

Z-31

Documentation - It may seem incongruous to speakof documentation as being a source of voltagemeasurement error, but the fact is that thermocouplesystems, by their very ease of use, invite a large numberof data points. The sheer magnitude of the data canbecome quite unwieldy. When a large amount of data istaken, there is an increased probability of error due tomislabeling of lines, using the wrong NBS curve, etc.

Since channel numbers invariably change, datashould be categorized by measureand, not just channelnumber.6 Information about any given measureand,such as transducer type, output voltage, typical valueand location, can be maintained in a data file. This canbe done under computer control or simply by filling outa pre-printed form. No matter how the data ismaintained, the importance of a concise system shouldnot be underestimated, especially at the outset of acomplex data gathering project.

Diagnostics Most of the sources of error that we have mentioned

are aggravated by using the thermocouple near itstemperature limits. These conditions will beencountered infrequently in most applications. But whatabout the situation where we are using smallthermocouples in a harsh atmosphere at hightemperatures? How can we tell when the thermocoupleis producing erroneous results? We need to develop areliable set of diagnostic procedures.

Through the use of diagnostic techniques, R.P. Reedhas developed an excellent system for detecting faultythermocouples and data channels.6 Three componentsof this system are the event record, the zone box test,and the thermocouple resistance history.

Event Record - The first diagnostic is not a test at all,but a recording of all pertinent events that could evenremotely affect the measurements. An example would be:

MARCH 18 EVENT RECORD10:43 Power failure10:47 System power returned11:05 Changed M821 to type K thermocouple13:51 New data acquisition program16:07 M821 appears to be bad reading

Figure 29

We look at our program listing and find that measurand#M821 uses a type J thermocouple and that our new dataacquisition program interprets it as a type J. But from theevent record, apparently thermocouple M821 waschanged to a type K, and the change was not entered intothe program. While most anomalies are not discoveredthis easily, the event record can provide valuable insightinto the reason for an unexplained change in a systemmeasurement.This is especially true in a systemconfigured to measure hundreds of data points.

Zone Box Test - A zone box is an isothermal terminalblock of known temperature used in place of an ice bathreference. If we temporarily short-circuit thethermocouple directly at the zone box, the systemshould read a temperature very close to that of the zonebox, i.e., close to room temperature.

If the thermocouple lead resistance is much greaterthan the shunting resistance, the copper wire shuntforces V = 0. In the normal unshorted case, we want tomeasure TJ, and the system reads:

V ≅ α (TJ - TREF)

But, for the functional test, we have shorted the terminalsso that V=0.The indicated temperature T’J is thus:

0 = α (T’J - TREF)T’J = TREF

Thus, for a dvm reading of V = 0, the system willindicate the zone box temperature. First we observe thetemperature TJ (forced to be different from TREF), thenwe short the thermocouple with a copper wire andmake sure that the system indicates the zone boxtemperature instead of TJ.

This simple test verifies that the controller, scanner,voltmeter and zone box compensation are all operatingcorrectly. In fact, this simple procedure tests everythingbut the thermocouple wire itself.

Thermocouple Resistance - A sudden change in theresistance of a thermocouple circuit can act as awarning indicator. If we plot resistance vs. time for eachset of thermocouple wires, we can immediately spot asudden resistance change, which could be an indicationof an open wire, a wire shorted due to insulation failure,changes due to vibration fatigue, or one of many failuremechanisms.

For example, assume we have the thermocouplemeasurement shown in Figure 31.

We want to measure the temperature profile of anunderground seam of coal that has been ignited. Thewire passes through a high temperature region, into acooler region. Suddenly, the temperature we measurerises from 300°C to 1200°C. Has the burning section ofthe coal seam migrated to a different location, or hasthe thermocouple insulation failed, thus causing a shortcircuit between the two wires at the point of a hot spot?

6 Refer to Bibliography 10

TJ

oltmeter

C

FeCu

Cu

Zone BoxIsothermal Block

+

–

V

v

Cu

Cu

TREF

Copper Wire Short

SHORTING THE THERMOCOUPLE AT THE TERMINALSFigure 30

If we have a continuous history of the thermocouplewire resistance, we can deduce what has actuallyhappened.

The resistance of a thermocouple will naturallychange with time as the resistivity of the wire changesdue to varying temperature. But a sudden change inresistance is an indication that something is wrong. Inthis case, the resistance has dropped abruptly,indicating that the insulation has failed, effectivelyshortening the thermocouple loop.

The new junction will measure temperature Ts, not T1.The resistance measurement has given us additionalinformation to help interpret the physical phenomenondetected by a standard open thermocouple check.

Measuring Resistance - We have casuallymentioned checking the resistance of the thermocouplewire as if it were a straightforward measurement. Butkeep in mind that when the thermocouple is producing avoltage, this voltage can cause a large resistancemeasurement error. Measuring the resistance of athermocouple is akin to measuring the internalresistance of a battery. We can attack this problem witha technique known as offset compensated ohmsmeasurement.

As the name implies, the voltmeter first measures thethermocouple offset voltage without the ohms currentsource applied. Then the ohms current source is

Z-32

Z

Summary In summary, the integrity of a thermocouple system

can be improved by following these precautions:• Use the largest wire possible that will not

shunt heat away from the measurement area.• If small wire is required, use it only in the region

of the measurement and use extension wire for the region with no temperature gradient.

• Avoid mechanical stress and vibration which could strain the wires.

• When using long thermocouple wires, connect the wire shield to the dvm guard terminal and usetwisted pair extension wire.

• Avoid steep temperature gradients.• Try to use the thermocouple wire well within its

temperature rating.• Use a guarded integrating A/D converter.• Use the proper sheathing material in hostile

environments to protect the thermocouple wire.• Use extension wire only at low temperatures and

only in regions of small gradients.• Keep an event log and a continuous record of

thermocouple resistance.

switched on and the voltage across the resistance ismeasured again. The voltmeter software compensatesfor the offset voltage of the thermocouple andcalculates the actual thermocouple source resistance.

Special Thermocouples - Under extreme conditions,we can even use diagnostic thermocouple circuitconfigurations. Tip-branched and leg-branchedthermocouples are four-wire thermocouple circuits thatallow redundant measurement of temperature, noise,voltage and resistance for checking wire integrity. Theirrespective merits are discussed in detail in REF. 8.

Only severe thermocouple applications require suchextensive diagnostics, but it is comforting to know thatthere are procedures that can be used to verify theintegrity of an important thermocouple measurement.

T1

To Data AcquisitionSystem

T = 1200˚C T = 300˚C

t1 Time

R

T1

Short

TS

Leg-Branched Thermocouple

Tip-Branched Thermocouple

BURNING COAL SEAMFigure 31

THERMOCOUPLE RESISTANCE vs.TIMEFigure 32

CAUSE OF THE RESISTANCE CHANGEFigure 33

Figure 34

HistoryThe same year that Seebeck made his discovery

about thermoelectricity, Sir Humphrey Davy announcedthat the resistivity of metals showed a markedtemperature dependence. Fifty years later, Sir WilliamSiemens proffered the use of platinum as the element ina resistance thermometer. His choice proved mostpropitious, as platinum is used to this day as theprimary element in all high-accuracy resistancethermometers. In fact, the Platinum ResistanceTemperature Detector, or PRTD, is used today as aninterpolation standard from the oxygen point(-182.96°C) to the antimony point (630.74°C).

Platinum is especially suited to this purpose, as it canwithstand high temperatures while maintaining excellentstability. As a noble metal, it shows limited susceptibilityto contamination.

The classical resistance temperature detector (RTD)construction using platinum was proposed by C.H.Meyers in 1932.7 He wound a helical coil of platinum ona crossed mica web and mounted the assembly insidea glass tube. This construction minimized strain on thewire while maximizing resistance.

Although this construction produces a very stableelement, the thermal contact between the platinum andthe measured point is quite poor. This results in a slowthermal response time. The fragility of the structurelimits its use today primarily to that of a laboratorystandard.

Another laboratory standard has taken the place ofMeyers’ design. This is the bird-cage element proposedby Evans and Burns.8 The platinum element remainslargely unsupported, which allows it to move freelywhen expanded or contracted by temperaturevariations.

Strain-induced resistance changes over time andtemperature are thus minimized, and the bird-cagebecomes the ultimate laboratory standard. Due to theunsupported structure and subsequent susceptibility tovibration, this configuration is still a bit too fragile forindustrial environments.

Z-33

Metal Film RTD’sIn the newest construction technique, a platinum or

metal-glass slurry film is deposited or screened onto asmall flat ceramic substrate, etched with a laser-trimming system, and sealed. The film RTD offerssubstantial reduction in assembly time and has thefurther advantage of increased resistance for a givensize. Due to the manufacturing technology, the devicesize itself is small, which means it can respond quicklyto step changes in temperature. Film RTD’s arepresently less stable than their hand-madecounterparts, but they are becoming more popularbecause of their decided advantages in size andproduction cost. These advantages should provide theimpetus for future research needed to improve stability.

THE RTD

7 Refer to Bibliography 128 Refer to Bibliography 16

A more rugged construction technique is shown inFigure 37. The platinum wire is bifilar wound on a glassor ceramic bobbin. The bifilar winding reduces theeffective enclosed area of the coil to minimize magneticpickup and its related noise. Once the wire is woundonto the bobbin, the assembly is then sealed with acoating of molten glass. The sealing process assuresthat the RTD will maintain its integrity under extremevibration, but it also limits the expansion of the platinummetal at high temperatures. Unless the coefficients ofexpansion of the platinum and the bobbin matchperfectly, stress will be placed on the wire as thetemperature changes, resulting in a strain-inducedresistance change. This may result in a permanentchange in the resistance of the wire.

There are partially supported versions of the RTDwhich offer a compromise between the bird-cageapproach and the sealed helix. One such approachuses a platinum helix threaded through a ceramiccylinder and affixed via glass-frit. These devices willmaintain excellent stability in moderately ruggedvibrational applications.

Glass sealed Biflar Winding

Thick Film Omega Film Element

Typical RTD Probes

Thin Film Omega TFD Element

MYERS RTD CONSTRUCTIONFigure 35

TYPICAL RTD’sFIgures 36 and 37

Z-34

Z

Metals - All metals produce a positive change inresistance for a positive change in temperature. This, ofcourse, is the main function of an RTD. As we shallsoon see, system error is minimized when the nominalvalue of the RTD resistance is large. This implies ametal wire with a high resistivity. The lower the resistivityof the metal, the more material we will have to use.

Table 6 lists the resistivities of common RTDmaterials.

METAL RESISTIVITY OHM/CMF(cmf = circular mil foot)_________ ___________________

Gold Au 13.00Silver Ag 8.8Copper Cu 9.26Platinum Pt 59.00Tungsten w 30.00Nickel Ni 36.00

Table 6

Because of their lower resistivities, gold and silver arerarely used as RTD elements. Tungsten has a relativelyhigh resistivity, but is reserved for very high temperatureapplications because it is extremely brittle and difficultto work.

Copper is used occasionally as an RTD element. Itslow resistivity forces the element to be longer than aplatinum element, but its linearity and very low costmake it an economical alternative. Its uppertemperature limit is only about 120ºC.

The most common RTD’s are made of either platinum,nickel, or nickel alloys. The economical nickel derivativewires are used over a limited temperature range. Theyare quite non-linear and tend to drift with time. Formeasurement integrity, platinum is the obvious choice.

Resistance Measurement The common values of resistance for a platinum RTD

range from 10 ohms for the bird-cage model to severalthousand ohms for the film RTD. The single mostcommon value is 100 ohms at 0ºC. The DIN 43760standard temperature coefficient of platinum wire is α =.00385. For a 100 ohm wire, this corresponds to + 0.385ohms/ºC at 0ºC. This value for α is actually the averageslope from 0ºC to 100ºC. The more chemically pureplatinum wire used in platinum resistance standardshas an α of +.00392 ohms/ohm/ºC.

Both the slope and the absolute value are smallnumbers, especially when we consider the fact that themeasurement wires leading to the sensor may beseveral ohms or even tens of ohms. A small leadimpedance can contribute a significant error to our

temperature measurement.

A ten ohm lead impedance implies 10/.385 ≅ 26ºCerror in measurement. Even the temperature coefficientof the lead wire can contribute a measurable error. Theclassical method of avoiding this problem has been theuse of a bridge.

The bridge output voltage is an indirect indication ofthe RTD resistance. The bridge requires four connectionwires, an external source, and three resistors that havea zero temperature coefficient. To avoid subjecting thethree bridge-completion resistors to the sametemperature as the RTD, the RTD is separated from thebridge by a pair of extension wires:

These extension wires recreate the problem that wehad initially: The impedance of the extension wiresaffects the temperature reading. This effect can beminimized by using a three-wire bridge configuration:

If wires A and B are perfectly matched in length, theirimpedance effects will cancel because each is in anopposite leg of the bridge. The third wire, C, acts as asense lead and carries no current.

The Wheatstone bridge shown in Figure 41 creates anon-linear relationship between resistance change andbridge output voltage change. This compounds thealready non-linear temperature-resistance characteristicof the RTD by requiring an additional equation to convertbridge output voltage to equivalent RTD impedance.

Lead

Lead

R = 5 Ω

R = 5 Ω

100 Ω RTD

–

+ DVM

RTD

–

+ DVM

RTD

ADVM

C

B

EFFECT OF LEAD RESISTANCE

WHEATSTONE BRIDGE

3-WIRE BRIDGE

Figure 38

Figure 39

Figure 40

Figure 41

Z-35

4-Wire Ohms - The technique of using a currentsource along with a remotely sensed digital voltmeteralleviates many problems associated with the bridge.

The output voltage read by the dvm is directly portionalto RTD resistance, so only one conversion equation isnecessary. The three bridge-completion resistors arereplaced by one reference resistor. The digital voltmetermeasures only the voltage dropped across the RTD andis insensitive to the length of the lead wires.

The one disadvantage of using 4-wire ohms is that weneed one more extension wire than the 3-wire bridge.This is a small price to pay if we are at all concernedwith the accuracy of the temperature measurement.

3-Wire Bridge Measurement ErrorsIf we know VS and VO, we can find Rg and then solve fortemperature. The unbalance voltage Vo of a bridge built

with R1 = R2 is:

R3 1VO= VS ——— – VS —(R3 + Rg) (2)If Rg = R3, VO= 0 and the bridge is balanced. This can

be done manually, but if we don’t want to do a manualbridge balance, we can just solve for Rg in terms of VO:

VS - 2VORg = R3 ————(VS + 2VO)This expression assumes the lead resistance is zero. If

Rg is located some distance from the bridge in a 3-wireconfiguration, the lead resistance RL will appear inseries with both Rg and R3:

Again we solve for Rg:

Vs - 2Vo 4VoRg = R3 ———— - RL ————(VS + 2Vo) (Vs + 2Vo)

Resistance to TemperatureConversion

The RTD is a more linear device than thethermocouple, but it still requires curve-fitting. TheCallendar-Van Dusen equation has been used for yearsto approximate the RTD curve:9

T T T TRT=R0+R0 α T-δ- —— -1 —— -β —— -1 ——[ (100 )(100) (100 )(100)3 ]

Where:RT = Resistance at Temperature TRo = Resistance at T = 0ºCα = Temperature coefficient at T = 0ºC

(typically +0.00392Ω/Ω/ºC)δ = 1.49 (typical value for .00392 platinum)β = 0 T > 0

0. 11 (typical) T < 0

The exact values for coefficients α , β , and δ aredetermined by testing the RTD at four temperatures andsolving the resultant equations. This familiar equationwas replaced in 1968 by a 20th order polynomial inorder to provide a more accurate curve fit.

The plot of this equation shows the RTD to be a morelinear device than the thermocouple:

9 Refer to Bibliography 11 and 13.

–

+

DVM

= 0100 W RTD

= 0

ii

i

The error term will be small if Vo is small, i.e., thebridge is close to balance. This circuit works well withdevices like strain gauges, which change resistancevalue by only a few percent, but an RTD changesresistance dramatically with temperature. Assume theRTD resistance is 200 ohms and the bridge is designedfor 100 ohms:

Since we don’t know the value of RL, we must useequation (a), so we get:

6 - 1.9868Rg = 100 ————— = 199.01 ohms(6 + 1.9868)The correct answer is of course 200 ohms. That’s a

temperature error of about 2.5ºC.

Unless you can actually measure the resistance of RL

or balance the bridge, the basic 3-wire technique is notan accurate method for measuring absolutetemperature with an RTD. A better approach is to use a4-wire technique.

RTD = R

R3

VO

+-+-

VS

R2

R1

g

3V

1Ω

VO

+-+-

1Ω100Ω

200Ω6V

2.0066V

RL

Rg

RLR3

VO

+-+-

V3

2

Figure 43

4-WIRE OHMS MEASUREMENTFigure 42

Figure 44

Figure 45

Practical PrecautionsThe same practical precautions that apply to

thermocouples also apply to RTD’s, i.e., use shieldsand twisted-pair wire, use proper sheathing, avoidstress and steep gradients, use large extension wire,keep good documentation and use a guardedintegrating dvm. In addition, the following precautionsshould be observed.

Construction - Due to its construction, the RTD issomewhat more fragile than the thermocouple, andprecautions must be taken to protect it.

Self-Heating - Unlike the thermocouple, the RTD isnot self-powered. A current must be passed through thedevice to provide a voltage that can be measured. Thecurrent causes Joule (I2R) heating within the RTD,changing its temperature. This self-heating appears asa measurement error. Consequently, attention must bepaid to the magnitude of the measurement currentsupplied by the ohmmeter. A typical value for self-heating error is 1

2 ºC per milliwatt in free air. Obviously,an RTD immersed in a thermally conductive mediumwill distribute its Joule heat to the medium, and the errordue to self-heating will be smaller. The same RTD thatrises 1ºC per milliwatt in free air will rise only 1

10 ºC permilliwatt in air which is flowing at the rate of one meterper second.10

To reduce self-heating errors, use the minimum ohmsmeasurement current that will still give the resolutionyou require, and use the largest RTD you can that willstill give good response time. Obviously, there arecompromises to be considered.

Thermal Shunting - Thermal shunting is the act ofaltering the measurement temperature by inserting ameasurement transducer. Thermal shunting is more aproblem with RTD’s than with thermocouples, as thephysical bulk of an RTD is greater than that of athermocouple.

Thermal EMF - The platinum-to-copper connection thatis made when the RTD is measured can cause athermal offset voltage. The offset-compensated ohmstechnique can be used to eliminate this effect.

Z-36

Z

THE THERMISTORLike the RTD, the thermistor is also a temperature

sensitive resistor. While the thermocouple is the mostversatile temperature transducer and the PRTD is themost stable, the word that best describes the thermistoris sensitive. Of the three major categories of sensors,the thermistor exhibits by far the largest parameterchange with temperature.

Thermistors are generally composed ofsemiconductor materials. Although positive temperaturecoefficient units are available, most thermistors have anegative temperature coefficient (TC); that is, theirresistance decreases with increasing temperature. Thenegative T.C. can be as large as several percent perdegree Celsius, allowing the thermistor circuit to detectminute changes in temperature which could not beobserved with an RTD or thermocouple circuit.

The price we pay for this increased sensitivity is lossof linearity. The thermistor is an extremely non-lineardevice which is highly dependent upon processparameters. Consequently, manufacturers have notstandardized thermistor curves to the extent that RTDand thermocouple curves have been standardized.

An individual thermistor curve can be very closelyapproximated through use of the Steinhart-Hartequation:18

1T = A + BlnR + C (In R)3

where:

T = Degrees Kelvin

R = Resistance of the thermistor

A,B,C = Curve-fitting constants


Small RTD Large RTDFast Response Time Slow Response TimeLow Thermal Shunting Poor Thermal ShuntingHigh Self-Heating Error Low Self-Heating Error

16

12

8

4

0 200 400 600 800

Equivalent LinearitiesType S Thermocouple

vs.Platinum RTD

Temperature, °C

.390

.344

.293

Re

sist

an

ce T

em

pe

ratu

reC

oe

ffic

ien

t -

RT

D

Typ

e S

µv

/°C

Se

eb

eck

Co

eff

icie

nt

T

Thermistor

RTD

Thermocouple

v or

R

Figure 46

Figure 47

Z-37

APPENDIX AThe Empirical Laws of

Thermocouples 11

The following examples illustrate the empiricallyderived “laws” of thermocouples which are useful inunderstanding and diagnosing thermocouple circuits.

A, B, and C are found by selecting three data points onthe published data curve and solving the threesimultaneous equations. When the data points arechosen to span no more than 100ºC within the nominalcenter of the thermistor’s temperature range, thisequation approaches a rather remarkable ±.02°C curvefit.

Somewhat faster computer execution time is achievedthrough a simpler equation:

BT= ——— - CIn R-A

where A, B, and C are again found by selecting three(R,T) data points and solving the three resultantsimultaneous equations. This equation must be appliedover a narrower temperature range in order to approachthe accuracy of the Steinhart-Hart equation.

Linear ThermistorsA great deal of effort has gone into the development

of thermistors which approach a linear characteristic.These are typically 2- or 4-leaded devices requiringexternal matching resistors to linearize thecharacteristic curve. The modern data acquisitionsystem with its computing controller has made this kindof hardware linearization unnecessary.

MeasurementThe high resistivity of the thermistor affords it a

distinct measurement advantage. The four-wireresistance measurement is not required as it is withRTD’s. For example, a common thermistor value is 5000ohms at 25’C. With a typical T.C. of 4%/ºC, ameasurement lead resistance of 100 produces only a.05°C error. This error is a factor of 500 times less thanthe equivalent RTD error.

Disadvantages - Because they are semiconductors,thermistors are more susceptible to permanentdecalibration at high temperatures than are RTD’s orthermocouples. The use of thermistors is generallylimited to a few hundred degrees Celsius andmanufacturers warn that extended exposures even wellbelow maximum operating limits will cause thethermistor to drift out of its specified tolerance.

Thermistors can be made very small which meansthey will respond quickly to temperature changes. It alsomeans that their small thermal mass makes themespecially susceptible to self-heating errors.

Thermistors are a good deal more fragile than RTD’sor thermocouples and they must be carefully mountedto avoid crushing or bond separation.

MONOLITHIC LINEARTEMPERATURE SENSORA recent innovation in thermometry is the integrated

circuit temperature transducer. It is available in bothvoltage and current-output configurations. Both supplyan output that is linearily proportional to absolutetemperature. Typical values are 1 µA/K and 10 mV/K.

Except for the fact that they offer a very linear outputwith temperature, these devices share all thedisadvantages of thermistor devices and thus have alimited temperature range. The same problems of self-heating and fragility are evident, and they require anexternal power source.

These devices provide a convenient way to producean analog voltage proportional to temperature. Such aneed arises in a hardware thermocouple referencejunction compensation circuit (see Figure 15).


+

To DVM

A

= 1 A/Ki

10kΩ

To DVM10mv/ K

+

B

µ

CURRENT SENSOR VOLTAGE SENSOR

Figure 48

Z-38

Z

12 Refer to Bibliography 3

THE LAW OF INTERMEDIATE METALS

Inserting the copper lead between the iron andconstantan leads will not change the output voltage V,regardless of the temperature of the copper lead. Thevoltage V is that of an Fe-C thermocouple attemperature T1.

THE LAW OF INTERIOR TEMPERATURES

The output voltage V will be that of an Fe-C couple atTemperature T, regardless of the external heat sourceapplied to either measurement lead.

THE LAW OF INSERTED METALS

The voltage V will be that of an Fe-C thermocouple attemperature T, provided both ends of the platinum wireare at the same temperature. The two thermocouplescreated by the platinum wire (FePt and Pt -Fe) act inopposition.

All of the above examples assume the measurementwires are homogeneous; that is, free of defects andimpurities.

APPENDIX BThermocouple CharacteristicsOver the years, specific pairs of thermocouple alloys

have been developed to solve unique measurementproblems. Idiosyncrasies of the more commonthermocouples are discussed here.

We will use the term standard wire error to refer tothe common commercial specifications published in theAnnual Book of ASTM Standards. It represents theallowable deviation between the actual thermocoupleoutput voltage and the voltage predicted by the tables inNBS Monograph 125.

Noble Metal Thermocouples - The noble metalthermocouples, types B, R, and S, are all platinum orplatinum-rhodium thermocouples and hence sharemany of the same characteristics.

Diffusion - Metallic vapor diffusion at hightemperatures can readily change platinum wirecalibration; therefore, platinum wires should only beused inside a non-metallic sheath such as high-purityalumina. The one exception to this rule is a sheathmade of platinum, but this option is prohibitivelyexpensive.

Stability - The platinum-based couples are by far themost stable of all the common thermocouples. Type S isso stable that it is specified as the standard fortemperature calibration between the antimony point(630.74°C) and the gold point (1064.43ºC).

Type B - The B couple is the only commonthermocouple that exhibits a double-valued ambiguity.

Due to the double-valued curve and the extremely lowSeebeck coefficient at low temperatures, Type B isvirtually useless below 50°C. Since the output is nearlyzero from 0°C to 42°C, Type B has the uniqueadvantage that the reference junction temperature isalmost immaterial, as long as it is between 0º and40ºC. Of course, the measuring junction temperature istypically very high.

Base Metal Thermocouples Unlike the noble metal thermocouples, the base metal

couples have no specified chemical composition. Anycombination of metals can be used which results in avoltage vs. temperature curve fit that is within thestandard wire errors. This leads to some ratherinteresting metal combinations. Constantan, for example,is not a specific metal alloy at all, but a generic name fora whole series of copper-nickel alloys. Incredibly, theConstantan used in a type T (copper- Constantan)thermocouple is not the same as the Constantan used inthe type J (iron -Constantan) couple.12

C

v

+

--Fe

P

Fe

T1

t

T

Fe

C

T

Isothermal Block

Fe

C

v

+

--

T

Fe

C

T

C

T1

Isothermal Block

TlC

Fe

T

T

Cu

Cu

1

Isothermal Block

C

Fe

v

+

--

Double-Value Region

v

0 42 T, ˚C

Z-39

Type E - Although Type E standard wire errors are notspecified below 0°C, the type E thermocouple is ideallysuited for low temperature measurements because ofits high Seebeck coefficient (58 µV/°C), low thermalconductivity and corrosion resistance.

The Seebeck coefficient for Type E is greater than allother standard couples, which makes it useful fordetecting small temperature changes.

Type J - Iron, the positive element in a J couple, is aninexpensive metal rarely manufactured in pure form. Jthermocouples are subject to poor conformancecharacteristics because of impurities in the iron. Evenso, the J couple is popular because of its high Seebeckcoefficient and low price.

The J couple should never be used above 760°C dueto an abrupt magnetic transformation that can causedecalibration even after the instrument cools.

Type T - This is the only couple with publishedstandard wire errors for the temperature region below0°C; however, type E is actually more suitable at verylow temperatures because of its higher Seebeckcoefficient and lower thermal conductivity.

Type T has the unique distinction of having onecopper lead. This can be an advantage in a specializedmonitoring situation where a temperature difference isall that is desired.

The advantage is that the copper thermocouple leadsare the same metal as the dvm terminals, making leadcompensation unnecessary.

Types K & Nicrosil-Nisil - The Nicrosil-Nisilthermocouple, type N, is similar to type K, but it hasbeen designed to minimize some of the instabilities inthe conventional Chromel-Alumel combination.Changes in the alloy content have improved theorder/disorder transformations occurring at 500˚C, anda higher silicon content in the positive element improvesthe oxidation resistance at elevated temperatures. A fulldescription with characteristic curves is published inNBS Monograph 161.13

Tungsten - Tungsten-rhenium thermocouples arenormally used at high temperature in reducing orvacuum environments, but never in an oxidizingatmosphere because of the high reaction rates. Puretungsten becomes very brittle when heated above itsrecrystallization temperature (about 1200°C). To makethe wire easier to handle, rhenium alloys are used inboth thermocouple legs. Types G (tungsten vs. tungsten26% rhenium), C (tungsten 5% rhenium vs. tungsten26% rhenium) and D (tungsten 3% rhenium vs.tungsten 25% rhenium) thermocouples are available inbare wire forms as well as complete probe assemblies.All materials conform to published Limits of Error.

At high temperatures,small thermocouple wireis affected by diffusion,impurities, andinhomogeneity more sothan large wire.Thestandard wire errorsreflect this relationship.

Note that each NBS wire error specification carries with it awire size.The noble metal thermocouples (B, R, and S) arespecified with small (24 ga.) wire for obvious cost reasons.

13 Refer to Bibliography 14.14 Refer to Bibliography 3.

ASTM STANDARD WIREERRORS14

®

871 170 °C

± 8.5 °C± 4.4

1/2 % Slope

TYPE B 24 AWG

0 538 1482 °C

± 1.4± 3.7 °C

1/4 %

TYPE R,S 24 AWG

± 1.7

0 316 871 °C

± 4.4 °C

1/2 %

TYPE E 8 AWG

2%

± 1.2± .8

± 2.8 °C

3/4 %

_ 101 _ 59 93 371 °C

TYPE T 14 AWG

0 277 760 °C

± 5.7 °C

± 2.23/4 %

TYPE J 8 AWG

± 2.2

0 277 °C 1260

± 9.5

3/4 %

TYPE K 8 AWG

_

+Cu

Cu

Voltmeter

v = (T1 _ T2)

Cu

T1

T2

C

(Ambient Reference)

Cu

TYPE T

°CSTANDARD STANDARD NBS SPECIFIED

TYPE METAL COLOR CODE Ω/DOUBLE FOOT SEEBECK COEFFICIENT WIRE ERROR MATERIAL RANGE ††+ - + - 20 AWG S(µV/º C) @T (º C) (SEE APPENDIX B) (º C)Platinum - Platinum -

B 6% Rhodium 30% Rhodium – 0.2 6 600 4.4 to 8.6 0 to 1820*Nickel -

E 10% Chromium Constantan Violet Red 0.71 58.5 0 1.7 to 4.4 -270 to 1000J Iron Constantan White Red 0.36 50.2 0 1.1 to 2.9 - 210 to 760

Nickel -K I0% Chromium Nickel Yellow Red 0.59 39.4 0 1.1 to 2.9 -270 to 1372N (AWG Nicrosil Nisil – – 39 600 – 0 to 1300

14)N (AWG Nicrosil Nisil – – 26.2 0 – -270 to 400

28) Platinum-

R 13% Rhodium Platinum – 0.19 11.5 600 1.4 to 3.8 -50 to 1768Platinum -

S 10% Rhodium Platinum – 0.19 10.3 600 1.4 to 3.8 -50 to 1768T Copper Constantan Blue Red 0.30 38 0 0.8 to 2.9 -270 to 400

Tungsten - Tungsten -W-Re 5% Rheniurn 26% Rhenium – – 19.5 600 – 0 to 2320

Z-40

Z

AWG DIA, MILS DIA, mm8 128 3.3

10 102 2.612 81 2.114 64 1.616 51 1.318 40 120 32 0.822 25 0.624 20 0.526 16 0.428 13 0.3

* Hewlett Packard Company makes no warranty as to theaccuracy or completeness of the foregoing material anddisclaims any responsibility therefor. (Editor’s Note:Thermocouple data which conform to ITS-90 are given in“ITS-90 Thermocouple Direct and Inverse Polynomials.”)

* Type B double-valued below 42°C - curve fit specified only above 130°C † Material range is for 8 AWG wire; decreases with decreasing wire size

1. Charles Herzfeld, F.G. Brickwedde: Temperature - Its Measurement and Control in Science and Industry, Vol. 3, Part 1, Reinhold, New York, 1962.

2. Robert P. Benedict: Fundamentals of Temperature, Pressure and Flow Measurements, John Wiley & Sons, Inc., New York, 1969.

3. Manual on the Use of Thermocouples in Temperature Measurement, ASTM Special Publication 470A, Omega Press, Stamford, Connecticut 06907, 1974.

4. Thermocouple Reference Tables, NBS Monograph 125, National Bureau of Standards, Washington, D.C., 1979. Also, Temperature-Millivolt Reference Tables-Section T, Omega Temperature Measurement Handbook, Omega Press, Stamford Connecticut 06907,1983.

5. H. Dean Baker, E.A. Ryder, N.H. Baker: Temperature Measurement in Engineering, Omega Press, Stamford, Connecticut 06907, 1953.

6. Temperature Measurement Handbook, Omega Engineering, Inc., Stamford, Connecticut.

7. R.L. Anderson: Accuracy of Small Diameter Sheathed Thermocouples for the Core Flow Test Loop, Oak Ridge National Laboratories, ORNL-54011 (available from National Information Service), April, 1979.

8. R. R Reed: Branched Thermocouple Circuits in Underground Coal Gasification Experiments, Proceedings of the 22nd ISA International Instrumentation Symposium, Instrument Society of America, 1976.

9. R.J. Moffat: The Gradient Approach to Thermocouple Circuitry, from Temperature - Its Measurement and Control in Science and Industry, Reinhold, New York, 1962

10. R.P. Reed: A Diagnostics-Oriented System for Thermocouple Thermometry, Proceedings of 24th ISA International Instrumentation Symposium, Instrument Society of America, 1978.

11. Harry R. Norton: Handbook of Transducers for Electronic Measuring Systems, Prentice-Hall, Englewood Cliffs, New Jersey.

12. C.H. Meyers: Coiled Filament Resistance Thermometers, NBS Journal of Research, Vol. 9, 1932.

13. Bulletin 9612, Rev. B: Platinum Resistance Temperature Sensors, Rosemount Engineering Co., 1962.

14. Burley, Powell, Burns & Scroger: The Nicrosil vs. Nisil Thermocouple:Properties and Thermoelectric Reference Data, NBS Monograph 161, U.S. Dept. of Commerce, Washington, D.C., 1978

15. J.P Tavener: Platinum Resistance Temperature Detectors - State of the Art, Measurements & Control, Measurements & Data Corporation, Pittsburgh, PA., April, 1974.

16. J.P. Evans and G.W. Burns: A Study of Stability of High Temperature Platinum Resistance Thermometers, in Temperature - Its Measurement and Control in Science and Industry, Reinhold, New York, 1962.

17. D.D. Pollock: The Theory and Properties of Thermocouple Elements, ASTM STP 492, Omega Press, Stamford, Connecticut 06907, 1979.

18. YSI Precision Thermistors, Yellow Springs Instruments, Yellow Springs, Ohio, 1977.

TYPE K0

°C 27

7°C

±2.2°C

Wire Size AWG3 24

or28

%4

20 14

TEMPERATURE RANGE vs. WIRE SIZE vs. ERROR

887

1

982

1093

1260

±9.5

°C°C

Err

or

BIBLIOGRAPHYThermocouple Well: Lowergradient, protects wire and allowsuser to change thermocouplewithout interrupting process.

Exposed Junction: Wires unprotected, faster response.Ungrounded Junction: Best protection, electronically isolated.Grounded Junction: WIres protected, faster response.

Thermocouple Washers:Couple built into washer;convenient mounting.

Ungrounded GroundedExposed

Connector: Composed of same metals as thermocouple, forminimum connection error.

OMEGA ENGINEERING, INC. gratefully acknowledges theHEWLETT PACKARD COMPANY for permission to reproduceApplication Note 290-Practical Temperature Measurements .

Z-41

T he ANSI standard base-metal thermocouples,designated E, J, K and T (Ref. 1), show inherentthermoelectr ic instability related to time- and/ortemperature-dependent instabilities in several of theirphysical, chemical, nuclear, structural and electronicproperties. This paper reviews the major thermoelectricproperties of the new nickel-base thermocouple systemNicrosil versus Nisil (designated type N), in which veryhigh thermoelectric stability has been achieved by ajudicious choice of elemental componentconcentrations.

INSTABILITY OF CONVENTIONALBASE-METAL THERMOCOUPLES

There are three principal characteristic types andcauses of thermoelectric instability in the standardbase-metal thermoelement materials:

1. A gradual and generally cumulative drift in thermalEMF on long exposure at elevated temperatures. This isobserved in all base-metal thermoelement materialsand is majnly due to compositional changes caused byoxidation, in particular internal oxidation (Figures 1 and2), and to neutron irradiation which can producetransmutation in nuclear reactor environments.

2. A short-term cyclic change in thermal EMF onheating in the temperature range about 250º to 650ºC,which occurs in types KP (or EP) and JN (or TN andEN). This kind of EMF instability is thought to be due tosome form of structural change like magnetic short-range order (Figures 3 and 4).

3. A time-independent perturbation in thermal EMF inspecific temperature ranges. This is due to composition-dependent magnetic transformations which perturb thethermal EMF’s in type KN in the range of about 25º to225ºC (Figure 5), and in type JP above about 730ºC.

ULTRA-HIGH STABILITY OFNICROSILINISIL (TYPE N)THERMOCOUPLE

Nicrosil and Nisil thermocouple alloys (Ref. 2) showgreatly enhanced thermoelectric stability (Ref. 3)relative to the other standard base-metal thermocouplealloys because their compositions (Table 1) are such asto virtually eliminate or substantially reduce the causesof thermoelectric instability described above. This isachieved primarily by increasing component soluteconcentrations (chromium and silicon) in a base ofnickel above those required to cause a transition frominternal to external modes of oxidation, and by selectingsolutes (silicon and magnesium) which preferentiallyoxidize to form a diffusion-barrier, and hence oxidationinhibiting films.

The thermal EMF instabilities of the short-term cyclickind occurring in KP and JN alloys have virtually beeneliminated in nicrosil (NP) by setting the chromiumcontent at 14.2 weight-%.

The increase in the silicon content of nisil (NN) to 4.4weight-% has suppressed the magnetic transformationof this new alloy to below room temperature.

Virtual freedom from nuclear transmutation effects isachieved by eliminating such elements as manganese,cobalt and iron from the specified compositions of bothalloys.

The very high thermoelectr ic stabil i ty of theNicrosil/Nisil (type N) thermocouple is illustrated inFigures 1 and 2. The influence of thermoelementconductor cross-sectional area upon the thermal-EMFconstancy of Nicrosil/Nisil is shown in Figure 6.

Nicrosil/Nisil Type N ThermocouplesThe Nicrosil/Nisil Type N thermocouple offers betterstability than existent base-metal Types E, J, K and T.It is now available and in widespread use worldwide.

DR. NOEL A. BURLEY

Z-42

As Figure 2 shows, 8 AWG type K thermocouplesappear to be markedly more unstable as temperaturesprogressively exceed about 1050º C. In contrast, it isclear from Figure 6 that type N thermocouples, in arange of wire sizes finer than 8 AWG, can be usedreliably for extended periods of time at temperatures upto at least 1200º C. Indeed, it has recently been

demonstrated (Ref. 4) that, in oxidizing atmospheres,the thermoelectr ic stabil i ty of the Nicrosil/Nisi lthermocouple, in wire sizes not finer than 10 AWG, isabout the same as that of the noble-metalthermocouples of ANSI types R and S up to about1200ºC.

100

0

–200

–400

–600

–800

(KP/KN) #14K

#14 NIC/NIS

#14 E(KP/JN)

(KP/JN)

(JP/JN)

#8E

#8J

(JP/JN)

CALIBRATION TEMPERATURE 497°C

#14 J

250

0

–500

–1000

–1500

NIC/NIS #14 E

#8J

CALIBRATION TEMPERATURE 777°C

#14 J

#14

#8 E

3000 600 900 1200 1500

EXPOSURE TIME AT 777°C (h)

TH

ER

MA

L E

MF

DR

IFT

(uv)

FIGURE 1. Long-term thermal-EMF drifts in air,at two calibration temperatures, for 14 AWG (#14)Nicrosil/Nisil (N) and E, J and K T/Cs. Thermal-EMF drifts for 8 AWG (#8) E and J T/Cs are alsogiven. The drifts are changes from EMF outputvalues existent after 20 hrs of exposure at con-stant aging temperature of 777°C (Ref. 3).

4

2

0

200

100

0

#8K

#10 NIC/NIS

4

2

0

200

100

0

#8K

#12 NIC/NIS

4

2

0

200

100

0

#8K

#14 NIC/NIS

0

6

4

2

0

300

200

100

#8K(KP/KN)

#8K

#8 NIC/NIS

TH

ER

MA

L E

MF

DR

IFT

(uv)

DR

IFT

(°C

)

0

6

4

2

0

300

200

100

#8K

#16 NIC/NIS

200 400 600 800 1000 1200

EXPOSURE TIME (h)AT 1077°C, 1152°C, 1202°C

0

FIGURE 2. Long-term thermal-EMF drifts in air,at three constant aging (and calibration) tem-peratures for Nicrosil/Nisil T/Cs in five wiregauges (#). Corresponding thermal-EMF driftsfor 8 AWG (#8) type K T/Cs at two of thesetemperatures are also given. The drifts arechanges from EMF output values existent after80 hours of exposure at the constant aging tem-perature (Ref. 3).

Z

Z-43

0.6

FIGURE 3 (Left). Changes in the Seebeck coefficient(∆S) of a typical type KP thermoelement vs. platinum oninitial heating, as a function of constant aging tempera-ture for the indicated times (Ref. 3).

FIGURE 4 (Right). Similar changes of a type JN thermo-element (Ref. 3).

0.5

0.4

0.3

0.2

0.1

0

30 Days

3 Days

7 h

45 minground state

600400 800200

∆S (

uV/°

C)

0.2

200

0.1

0.05

0

–0.05

–0.1

–0.2

–0.3

400 600

5 min

45 min

3 Days30 Days

TEMPERATURE(°C)

Type N Thermocouples

PROMULGATION AS A STANDARDNo new thermocouple wil l survive for

universal adoption and use unless it is formallypromulgated by national standards authoritiesaround the world. It is for tunate that theNicrosil/Nisil thermocouple system is in vigorousprocess of being so promulgated.

The ASTM, through its Committee E-20 onTemperature Measurement, has shownconsiderable interest in Nicrosil versus Nisil, andhas kept matters relating to the development,availability and use of the new thermocoupleunder continual review.

Recently, relevant subcommittees of ASTME-20 have produced several publicationscontaining information on the properties andcharacteristics of the Nicrosil versus Nisilthermocouple. A document quoting several of theEMF-temperature tables from NBS Monograph161 (Ref. 2) was published (Ref. 6) forinformation. A formal ASTM Standard (E1223) ispromulgated, while Type N data is now includedin ASTM Standard E230. Again, in the recentlypublished third edition of the ASTM Manual onthe Use of Thermocouples (Ref. 8), variousproperties and characteristics of Nicrosil versusNisil are summarized.

Based mainly on the above information,several crucial actions now have been taken bythe supreme standardizing bodies in severalimportant countries:

1. The Instrument Society of America (ISA),in October 1983, promulgated the Nicrosil/Nisilsystem as a U.S. Standard Thermocouplebearing the letter-designation “type N.”

2. The British Standards Institute (BSI) hasrecently promulgated a standard on the type Nthermocouple identified as B.S.4937: Part 8.

3. The Japan Society for the Promotion ofScience, through its Committee TC19(Temperature), is nearing the conclusion of itsdeliberation on type N, leading to the issue of aJapan Industrial Standard (JIS).

These actions have ensured that the type Nthermocouple and its all ied pyrometr icinstrumentation and ancillary circuitry elementsare now commercially available in a number ofmajor countries around the world.

DISCUSSIONThe var ious types of thermoelectr ic

instability described in this paper can causesubstantial changes in thermoelectromotive forceand, hence, calibration in ANSI-standard letter-designated base-metal thermocouples types E,J, K and T. In the case of Nicrosil/Nisil, however,thermoelectric instability due to these causes is

TABLE.1- NOMINAL COMPOSITIONS OF ANSISTANDARD BASE-METAL THERMOELEMENTALLOYS, AND NICROSIL AND NISIL ALLOYS

ALLOY CHEMICAL COMPOSITION (WEIGHT-%)ANSI (1) Cr Si Mn Al Co Mg Cu Ni Fe

DESIGNATION

(+)KP, EP 9.5 0.4 bal(-)KN 1.0 3.0 2.0 0.4 0.015 bal

(+)JP 0.3 bal

(-)JN, EN, TN 1.0 0.5 54 44 0.5

(+)TP 100

(+)NP (nicrosil) 14.2 1.4 bal(-)NN (nisil) 4.4 0.10 bal

TABLE 2-VARIANTS OF TYPE KNALLOY CHEMICAL COMPOSITION (WEIGHT-%)

Mn Al Si co NiKN1 3.02 1.90 1.19 0.41 balanceKN2 1.67 1.25 1.56 0.72 balance KN3 - - 2.50 1.00 balanceKN4 0.43 - 2.39 0.23 balance

Z-44

Z

virtually eliminated or substantially attenuated over theentire temperature range up to 1230˚C. ANSI-standardbase-metal thermocouples types E, J, K and T can,therefore, be regarded as obsolescent. Theirreplacement by Nicrosil/Nisil thermocouples would lead,in most cases, to demonstrable technological andeconomic advantages for science and industry at large.Indeed, the enhanced calibration stability and longevityof the type N thermocouple, taken into account with itsability to operate at considerably higher upper operatingtemperatures than conventional base-metalthermocouples, make it ideally suited to scientific,technological and industr ial applications wheretemperature measurements are critical.

Use of type N thermocouples in several countrieshas already demonstrated a number of advantages:enhanced pyrometric accuracy, improved productquality and performance, lower reject rates, enhancedenergy utilization, lower pyrometric maintenance costs,and improved productivity.

REFERENCES1. American National Standards Institute (ANSI)

Standard MC96.1-1975, Instrument Society of America (1976), pp. vi and 1.

2. N.A. Burley, et al., U.S. National Bureau of Standards Monograph 161, NBS* Washington (1978).

3. N.A. Burley, et al., Temperature, Its Measurement and Control in Science and Industry, vol. 5, part 2, Instrument Society of America (1982),p. 1159.

4. N.A. Burley, Proc. 11th IMEKO Conference(Sensors), Houston, TX, 1988, p. 155.

5. R.L. Powell, et al., U.S. National Bureau ofStandards Monograph 125, NBS* Washington(1974).

6. American Society for Testing and Materials (ASTM), Annual Book of Standards, vol. 14.01 (1983), p. 859.

7. ASTM Standard E 1223-87.8. Manual on the Use of Thermocouples in

Temperature Measurement, ASTM Special Technical Publication 470 B (1981).

9. N.A. Burley, et al., “The Nicrosil versus Nisil Type N Thermocouple: A Commercial Reality,” Australian Department of Defence Report MRL-R-903 (1983).

*The NBS is now NIST (National Institute of Standards andTechnology).

Reproduced with permission of H.L. Daneman, Box 31056,Sante Fe, NM 87594

THE AUTHORDR. NOEL A. BURLEY, D.App.Sc., C. Eng., F.I.M., F.A.I.M.,is General Manager, Research and Development, for Bell-IRH Pty., Ltd., an Australian company specializing in themanufacture of electrical and electronic components,instruments and sensors. It has considerable expertise andestablished reputation in temperature control. Contact Dr.Burley at Bell-IRH Pty., Ltd., 32 Paramatta Rd., LidcombeNSW 2141, Sydney, Australia, phone: 02 648 5455.

60

FIGURE 5. Deviations of the measured valuesof the thermal EMFs of several type KN ther-moelements vs. platinum from reference tablevalues (Ref. 5). Variants of type KN are givenin Table 2.

280

DE

VIA

TIO

N (

uV)

TEMPERATURE (°C)

120

320 360 400 440 480 520

TEMPERATURE (K)

40

0

–40

–80

–120

8040 160 200 2400

TE

MP

ER

ATU

RE

DE

VIA

TIO

N (

K)

KN2

0

KN1

KN3

KN4

1

–1

–2

–3

FIGURE 6. Relationship between total thermal-EMF drift (after 1000 hrs of exposure in air ateach of three test temperatures) and cross-sectional area of Nicrosil/Nisil T/C wires. Thedrifts are changes from EMF output values ex-istent after 80 hours of exposure (Ref. 3).

200

1202°C

6

16

0.2

14 12 10 8

150

100

50

5

4

3

2

1

250

00.4 0.6 0.80 1.0

0

TH

ER

MA

L E

MF

DR

IFT

(uv)

DR

IFT

(°C

)

WIRE GAUGE (A W G)

LOG CROSS-SECTIONAL AREA

1152°C

1077°C

Z-45

INTRODUCTION The mineral-insulated integrally metal-sheathed (MIMS) form of thermocoupleconsists of matched thermocouple wiressurrounded by insulating material (typicallyMgO) compacted by rolling, drawing orswaging until the sheath is reduced indiameter. The advantages of MIMSthermocouples are:

• Chemical isolation of wires from the surrounding atmosphere.

• Shielding of thermoelements from sources of electrical interference.

• Protection of the wires and insulation from damage due to shock.

• Flexibility of the final assembly allowingbending.

For two decades, people have creditedMIMS construction with a greatercapability than deserved. Quite frequently,this form has shown less stability, lessdurability and lower temperature limitsthan corresponding unsheathed elements.The nickel bearing MIMS thermocouplesused above 400º C (750º F) are especiallyvulnerable to calibration instability andshortened lifetime - factors which bearheavily on thermocouple use andselection.

HYSTERESIS Thermoelectric hysteresis is onecontributor toward calibration instability.Hysteresis is a form of short-rangeorder/disorder phenomenon occurringbetween 200 and 600º C (peaking at ≈400º C) for Ni-Cr alloys such as Type K. Itis evidenced by a calibration change ofseveral degrees as the thermocoupletemperature is cycled within thistemperature band. Type N thermocouplesexhibit hysteresis of up to 5º C whenheated and cooled between 200 and1000º C (peaking around 750º C). At900º C hysteresis is 2 to 3º C. If the type Kthermocouple, for example, will be usedbelow 500º C, hysteresis can be reducedby annealing overnight at 450º C.

OXIDATIONAnother phenomenon affecting calibrationis oxidation. Ni-Cr-AI alloys (e.g.,Chromel*) have limited life in air above500º C because of oxidation. A specialform of oxidation is so-called “green rot”which is preferential oxidation of Cr inatmospheres with low oxygen content(e.g., sheaths in which the volume of air islimited and stagnant). Nicrosil resistsoxidation up to about 1,250º C (2,300º F)and does not exhibit green rot.

Several new sheath materials called“Nicrobell” (**) consist of Nicrosil with 1.5%or 3.0% niobium. Nicrobell “A” isparticularly formulated to be resistant tooxidation. Another new oxidation resistantsheath material called Nicrosil + (***)

consists of Nicrosil plus 0.15%magnesium. It is reported (ref. 4) to exhibitless spalling and probably have a longerlife than some Nicrobell version(s) tested.

Nicrosil, itself, does not have satisfactoryresistance to reducing atmospheres, suchas encountered in most combustion ormany heat treating processes. Otheradaptations of Nicrosil for use as sheathmaterial (such as Nicrobells B, C and D)can be expected to deal with typicalnonoxidizing atmospheres.

CONTAMINATION A third influence on calibration stability iscontamination. The idea behind themineral-insulated, integrally designed,metal-sheathed thermocouple is that theuniform compression of finely dividedmineral oxides (typically MgO) insulationsurrounding the wires and filling thesheath would seal the internal volume,thereby eliminating contamination. Thevolume of the insulation compressed byswaging, rolling or drawing is on the orderof 85% of solid material. This is useful,permitting the tubing to be bent and alsopermitting the manufacture of smallerdiameter assemblies. It does, however,permit the intrusion of gas such as watervapor or air. It also permits vapor diffusionof elements composing the wires orsheath. Bentley and Morgan determinedthat the vapor-phase diffusion of Mn(manganese) through the MgO insulationhas the greatest influence onthermocouple decalibration.

METAL FATIGUE Metal fatigue is another cause ofshortened thermocouple life. Differingtemperature coefficients of linearexpansion between sheaths and wirescauses strain during heating or cooling.These strains result in eventual fracture

due to metal fatigue. On heating to 900º C,the thermal expansion of Nisil differs fromSS 304 by 0.4% of length. Nicrosil hasonly 0.05% difference in thermalexpansion compared to Nisil (the leg mostlikely to fracture). A sheath of Nicrosil,Nicrosil + or Niobell would therefore induceless metal fatigue in either leg of the TypeN thermocouple than would stainlesssteel.

COMPOSITION Composition changes in SS sheathedcouples are generally greater than inInconel (****) sheathed couples. In testsperformed by Anderson, et al., the KN legshowed an increase in chromium but adecrease in aluminum. These changes incomposition contributed the major portionof the resulting change in calibration of thethermocouple.Most stainless steels have from 1 to 2% ofmanganese. Type 304 has ≈ 2%manganese. Others have manganeseconcentrations varying from 1% to 10%.Inconel has up to 1% Mn. As a rule ofthumb, each 1% of Mn in the sheathmaterial contributes -10º C calibration shiftfor 1,000 hours at 1,100º C. According toBentley, at 1,200º C, Type N in a 3 mmdiameter SS sheath drifted -24º C in 1,000hours.

HUMIDITY There is a multiple effect of water vaporwithin the sheath. It is rapidly absorbed inthe MgO, reducing the insulationresistance. Humidity intrusion can ruin aMIMS thermocouple assembly in as shorta time as a few minutes. In lesseramounts, it destroys a protective oxidecoating on Nickel-Chromium alloys,subjecting them to more rapiddeterioration. The changes due to water

The Choice Of Sheathing For MineraI Insulated ThermocouplesH.L. Daneman, P.E.

0

200

DR

IFT

(°C

)

–25

+25

–500 400 600 800 1000 1200

ElapsedTime (h)

Type K(310 SS)

Type N(310 SS)

Type K(Inconel)

Type N(Inconel)

Figure 1. Drift of 3 mm diameter stainless steel sheathed and Inconel 600 sheathed type K andNicrosil vs. Nisil thermocouples in 1200°C in vacuum. The dips in the drift curve are the result ofthe "in-place inhomogeneity test" where the samples were extracted from the furnace by 5 cm.

Z-46

Z

vapor can be sufficiently severe as tomake affected couples useless byreducing insulation resistance. Thisreduced resistance can result inmisleading temperature readings,premature failure or even erroneousreadings after open circuiting.

Water vapor can be introduced duringthermocouple fabrication or repair, or evenby changes in atmospheric pressureduring air shipment or during long periodsof storage (e.g., six months) atconstruction sites. Care must be taken ofhermetic seals during shipment andinstallation.

RECOMMENDATIONSAlthough not mentioned above , there issome relationship between the diameterof these thermocouple materials andstability and longevity at elevatedtemperatures. The surface of thebrickwork on which electrical heaters aresupported becomes conductive atelevated temperatures. This leads to flowof electrical currents throughthermocouple sheaths to ground, perhapsthrough the measuring instrument.

The temptation to use the finest sheathedthermocouples (as fine as 1 mm) shouldbe resisted for higher temperature orcorrosive industrial environments.

Stainless steel is a poorer sheath formineral-insulated, metal-sheathedthermocouples than either Inconel 600 ormodified Nicrosil when used with Ni-Crthermocouples such as Type K or Type N.The modified Nicrosil sheathedthermocouples offer improved oxidationresistance up to 1,100º C (1,200 to1,250º C for Type N), reduced failures dueto differential thermal expansion, improvedductility and the elimination of the drift

problems caused by the vapor diffusion ofmanganese from stainless steels orInconel.

Considering the current state of supply ofthe newer materials, one could wellchoose a low manganese (0.3% or less)Inconel sheathed Type K MIMSthermocouple until such time as modifiedNicrosil sheathed Type K or N andappropriate supporting data becomereadily available.

(*) CHROMEL is a trademark of the Hoskins Manufacturing Co.

(**) NICROBELL is a trademark of NICROBELL Pty. Ltd. NICROBELL sheath alloys are patented in a numberof countries including the USA

(***) NICROSIL + is a trademark of Pyrotenax Australia Pty. Ltd.

(****) INCONEL is a trademark of theInternational Nickel Co.

Reproduced with the permission of:H.L. DanemanP.O. Box 31056Sante Fe, NM 87594

REFERENCES1. Anderson, R. L., Ludwig, R.L.,FAILURE

OF SHEATHED THERMOCOUPLES DUE TO THERMAL CYCLING, Temperature, (1982) pp 939-951

2. Anderson, R. L., Lyons, J. D., Kollie, T G., Christie, W. H., Eby, R., DECALIBRATION OF SHEATHED THERMOCOUPLES, Temperature, (1982) pp 977-1007

3. Bentley, R. E., NEW-GENERATION TEMPERATURE PROBES, Materials Australasia, April (1987), pp. 10-13

4. Bentley, R. E., THEORY AND PRACTICE OF THERMOELECTRIC THERMOMETERY, 2nd Edition, CSIRODiv. of Applied Physics, (1990) 152 pages.

5. Bentley, R.E., private communication, 11/22/90

6. Burley, N. A., HIGHLY STABLE NICKEL-BASE ALLOYS FOR THERMOCOUPLES, J. of the Australian Institute of Metals, May (1972), pp 101-113

7. Burley, N. A., Burns, G. W., Powell, R. L., NICROSIL AND NISIL:THEIR DEVELOPMENT AND STANDARDIZATION, Inst. Physical Conf. Ser. No. 26, (1975), pp 162-171

8. Burley, N. A., Jones, T.P., PRACTICAL PERFORMANCE OF NICROSIL-NISIL THERMOCOUPLES,Inst. Physical Conf. Ser. No. 26, (1975),pp 172-180

9. Burley, N. A., Powell, R. L., Burns, G. W., Scroger, M. G., THE NICROSIL VS NISIL THERMOCOUPLE:PROPERTIES AND THERMOELECTRIC DATA, NBS Monograph 161, April (1978), pp 1-156

10.Burley, N. A., THE NICROSIL VS NISIL THERMOCOUPLE: THE FIRST TWO DECADES, (1986) private communication

11. Burley, N. A., N-CLAD-N: A NOVEL ADVANCED TYPE N INTEGRALLY-SHEATHED THERMOCOUPLE OF ULTRA-HIGH THERMOELECTRIC STABILITY, High Temperatures-High Pressures, (1986) pp 609-616

12.Burley, N. A., NICROSIL/NISIL TYPE NTHERMOCOUPLE, Measurements & Control, April (1989), pp 130-133

13.Burley, N. A., ADVANCED INTEGRALLY SHEATHED TYPE N THERMOCOUPLE OF ULTRA-HIGH THERMOELECTRIC STABILITY, Measurement, Jan-Mar 1990, pp 36-41

14.Daneman, H. L., THERMOCOUPLES, Measurements & Control, June (1988),pp 242-243

15.Frank, D.E., AS TEMPERATURES INCREASE, SO DO THE PROBLEMS!, Measurements & Control, June (1988), p 245

16.Hobson, J. W., THE INTRODUCTION OF THE NICROSIL/NISIL THERMOCOUPLES IN AUSTRALIA, Australian Journal of Instrumentation and Control, October (1982), pp 102-104

17.Hobson, J. W., THE K TO N TRANSITION - BUILDING ON SUCCESS, Australian Journal of Instrumentation and Control, (1985) pp12-15

18.Northover, E. W., Hitchcock, J. A., A NEW HIGH-STABILITY NICKEL ALLOY, Instrument Practice, September (1971), pp 529-531

19.Paine, A., TYPE N AND K MIMS T/C’S, fax LNA5195, 11/23/90

20.Wang, T P., Starr, C. D., NICROSIL-NISIL THERMOCOUPLES IN PRODUCTION FURNACES, ISA (1978) Annual conference, pp 235-254

21.Wang, T. P., Starr, C. D., EMF STABILITY OF NICROSIL-NISIL AT 500˚C, ISA (1978) Annual conference, pp 221-233

Insi

tu D

rift

(°C

)

20

10

1100°C

0

-10

-200 1000

Time (h)

2000 3000

NCR

SS

1.6 mm Bare Wire

3 mm OD Mineral InsulatedMetal Sheathed Thermocouple

Figure 2. The insitu drift in type N thermocouples with tips held at 1100°C. Curves refer tomineral insulated metal sheathed thermocouples with 3mm OD sheaths of 310 stainless steel(SS) or Nicrosil (NCR) and 1.6mm bare wire thermocouples in air. The range in drift for thelatter is also indicated.

Z-47

Material Selection Guide

Acetate Solvents Crude or Pure Monel or NickelAcetic Acid 10% - 70°F 304 Stainless Steel

" " 50% - 70°F 304 Stainless Steel" " 50% - 212°F 316 Stainless Steel" " 99% - 70°F 430 Stainless Steel" " 99% - 212°F 430 Stainless Steel

Acetic Anhydride MonelAcetone 212°F 304 Stainless SteelAcetylene 304, Monel, NickelAlcohol Ethyl 70°F 304 Stainless Steel

" " 212°F 304 Stainless SteelAlcohol Methyl 70°F 304 Stainless Steel

" " 212°F 304 Stainless SteelAluminum Molten Cast ironAluminum Acetate Saturated 304 Stainless SteelAluminum Sulphate 10% - 70°F 304 Stainless Steel

" " Saturated 70°F 304 Stainless Steel" " 10% - 212°F 316 Stainless Steel" " Saturated 212°F 316 Stainless Steel

Ammonia All concentrations 70°F 304 Stainless SteelAmmonium Chloride All concentrations 212°F 316 Stainless SteelAmmonium Nitrate All concentrations 70°F 304 Stainless Steel

" " All concentrations 212°F 304 Stainless SteelAmmonium Sulphate 5% - 70°F 304 Stainless Steel

" " 10% - 212°F 316 Stainless Steel" " Saturated 212°F 316 Stainless Steel

Aniline All concentrations 70°F 304 Stainless SteelAmylacetate MonelAsphalt Steel (C1018)

Phosphor Bronze,Monel, Nickel

Barium Carbonate 70°F 304 Stainless SteelBarium Chloride 5% - 70°F Monel

" " Saturated 70°F Monel" " Aqueous - Hot 316 Stainless Steel

Barium Hydroxide Steel (C1018)Barium Sulphite NichromeBenzaldehyde Steel (C1018)Benzene 70°F 304 Stainless SteelBenzine Steel (C1018),

Monel, InconelBenzol Hot 304 Stainless SteelBoracic Acid 5% Hot or Cold 304 Stainless SteelBromine 70°F TantalumButadiene Brass, 304Butane 70°F 304 Stainless SteelButylacetate MonelButyl Alcohol CopperButylenes Steel (C1018),

Phosphor BronzeButyric Acid 5% - 70°F 304 Stainless Steel

" " 5% - 150°F 304 Stainless SteelCalcium Bisulfite 70°F 316 Stainless SteelCalcium Chlorate Dilute 70°F 304 Stainless Steel

" " Dilute 150°F 304 Stainless SteelCalcium Hydroxide 10% - 212°F 304 Stainless Steel

" " 20% - 212°F 304 Stainless Steel" " 50% - 212°F 317 Stainless Steel

Carbolic Acid All 212°F 316 Stainless SteelCarbon Dioxide Dry Steel (C1018), Monel

" " Wet Aluminum,Monel,NickelCarbon Tetrachloride 10% - 70°F MonelChlorex Caustic 316SS, 317SSChlorine Gas Dry 70°F 317 Stainless Steel

" " Moist 70°F Hastelloy C" " Moist 212°F Hastelloy C

Chromic Acid 5% - 70°F 304 Stainless Steel" " 10% - 212°F 316 Stainless Steel" " 50% - 212°F 316 Stainless Steel

Citric Acid 15% - 70°F 304 Stainless Steel" " 15% - 212°F 316 Stainless Steel" " Concentrated 212°F 317 Stainless Steel

Coal Tar Hot 304 Stainless SteelCoke Oven Gas AluminumCopper Nitrate 304, 316Copper Sulphate 304, 316Core Oils 316 Stainless SteelCottonseed Oil Steel (C1018),

Monel, NickelCreosols 304 Stainless SteelCreosote Crude Steel (C 1018),

Monel, NickelCyanogen Gas 304 Stainless SteelDowtherm Steel (C1018)Epsom Salt Hot and Cold 304 Stainless SteelEther 70°F 304 Stainless Steel

Ethyl Acetate MonelEthyl Chloride 70°F 304 Stainless SteelEthylene Glycol Steel (C1018)Ethyl Sulphate 70°F MonelFerric Chloride 1% - 70°F 316 Stainless Steel

" " 5% - 70°F Tantalum" " 5% - Boiling Tantalum

Ferric Sulphate 5% - 70°F 304 Stainless SteelFerrous Sulphate Dilute 70°F 304 Stainless SteelFormaldehyde 304 Stainless SteelFreon Steel (C1018)Formic Acid 5% - 70°F 316 Stainless Steel

" " 5% - 150°F 316 Stainless SteelGallic Acid 5% - 70°F Monel

" " 5% - 150°F MonelGasoline 70°F 304 Stainless SteelGlucose 70°F 304 Stainless SteelGlycerine 70°F 304 Stainless SteelGlycerol 304 Stainless SteelHeat Treating 446 Stainless SteelHydrobromic Acid 48% - 212°F Hastelloy BHydrochloric Acid 1% - 70°F Hastelloy C

" " 1% - 212°F Hastelloy B" " 5% - 70°F Hastelloy C" " 5% - 212°F Hastelloy B" " 25% - 70°F Hastelloy B" " 25% - 212°F Hastelloy B

Hydrocyanic Acid 316 Stainless SteelHydrofluoric Acid Hastelloy CHydrogen Peroxide 70°F 316 Stainless Steel

" " 212°F 316 Stainless SteelHydrogen Sulphide Wet and dry 316 Stainless SteelIodine 70°F TantalumKerosene 70°F 304 Stainless SteelLactic Acid 5% - 70°F 304 Stainless Steel

" " 5% - 150°F 316 Stainless Steel" " 10% - 212°F Tantalum

Lacquer 70°F 316 Stainless SteelLatex Steel (C1018)Lime Sulphur Steel (C1018), 304,

MonelLinseed Oil 70°F 304 Stainless SteelMagnesium Chloride 5% - 70°F Monel

" " 5% - 212°F NickelMagnesium Sulphate Cold and Hot MonelMalic Acid Cold and Hot 316 Stainless SteelMercury Steel (C1018) , 304,

MonelMethane 70°F Steel (1020)Milk 304, NickelMixed Acids Carpenter #20

(Sulphuric and Nitric- all temp. and %)

Molasses Steel (C1018), 304,Monel, Nickel

Muriatic Acid 70°F TantalumNap 70°F 304 Stainless SteelNatural Gas 70°F 304 Stainless SteelNeon 70°F 304 Stainless SteelNickel Chloride 70°F 304 Stainless SteelNickel Sulphate Hot and Cold 304 Stainless SteelNitric Acid 5% - 70°F 304 Stainless Steel

" " 20% - 70°F 304 Stainless Steel" " 50% - 70°F 304 Stainless Steel" " 50% - 212°F 304 Stainless Steel" " 65% - 212°F 316 Stainless Steel" " Concentrated - 70°F 304 Stainless Steel" " Concentrated - 212°F Tantalum

Nitrobenzene 70°F 304 Stainless SteelNitrous Acid 304 Stainless SteelOleic Acid 70°F 316 Stainless SteelOleum 70°F 316 Stainless SteelOxalic Acid 5% - Hot and Cold 304 Stainless Steel

" " 10% - 212°F MonelOxygen 70°F Steel (C1018)

" Liquid 304 Stainless SteelPalmitic Acid 316 Stainless SteelPetroleum EtherPhenoI 304 Stainless SteelPentane 304 Stainless SteelPhosphoric Acid 1% - 70°F 304 Stainless Steel

" " 5% - 70°F 304 Stainless Steel" " 10% - 70°F 316 Stainless Steel" " 10% - 212°F Hastelloy C" " 30% - 70°F Hastelloy B

Picric Acid 70°F 304 Stainless SteelPotassium Bromide 70°F 316 Stainless SteelPotassium Carbonate 1% - 70°F 304 Stainless SteelPotassium Chlorate 70°F 304 Stainless SteelPotassium Chloride 5% - 70°*F 304 Stainless Steel

" " 5% - 212°F 304 Stainless SteelPotassium Hydroxide 5% - 70°F 304 Stainless Steel

" " 25% - 212°F 304 Stainless Steel" " 50% - 212°F 316 Stainless Steel

Potassium Nitrate 5% - 70°F 304 Stainless Steel" " 5% - 212°F 304 Stainless Steel

PotassiumPermanganate 5% - 70°F 304 Stainless SteelPotassium Sulphate 5% - 70°F 304 Stainless Steel

" " 5% - 212°F 304 Stainless SteelPotassium Sulphide 70°F 304 Stainless SteelPropane 304 Stainless SteelPyrogallic Acid 304 Stainless SteelQuinine Bisulphate Dry 316 Stainless SteelQuinine Sulphate Dry 304 Stainless SteelResin 304 Stainless SteelRosin Molten 304 Stainless SteelSea Water MonelSalommoniac MonelSalicylic Acid NickelShellac 304 Stainless SteelSoap 70°F 304 Stainless SteelSodium Bicarbonate All concentrations 70°F 304 Stainless Steel

" " 5% - 150°F 304 Stainless SteelSodium Bisulphate MonelSodium Carbonate 5% - 70°F 304 Stainless Steel

" " 5% - 150°F 304 Stainless SteelSodium Chloride 5% - 70°F 316 Stainless Steel

" " 5% - 150°F 316 Stainless Steel" " Saturated - 70°F 316 Stainless Steel" " Saturated - 212°F 316 Stainless Steel

Sodium Fluoride 5% - 70°F MonelSodium Hydroxide 304 Stainless SteelSodium Hypochlorite 5% still 316 Stainless SteelSodium Nitrate Fused 317 Stainless SteelSodium Peroxide 304 Stainless SteelSodium Phosphate Steel (C1018)Sodium Silicate Steel (C1018)Sodium Sulphate 70°F 304 Stainless SteelSodium Sulphide 70°F 316 Stainless SteelSodium Sulphite 150°F 304 Stainless SteelSteam 304 Stainless SteelStearic Acid 304 Stainless SteelSulphur Dioxide Moist Gas - 70°F 316 Stainless Steel

" " Gas - 575°F 304 Stainless SteelSulphur Dry - Molten 304 Stainless Steel

" Wet 316 Stainless SteelSulphuric Acid 5% - 70°F Carp. 20, Hastelloy B

" " 5% - 212°F Carp. 20, Hastelloy B" " 10% - 70°F Carp. 20, Hastelloy B" " 10% - 212°F Carp. 20, Hastelloy B" " 50% - 70°F Carp. 20, Hastelloy B" " 50% - 212°F Carp. 20, Hastelloy B" " 90% - 70°F Carp. 20, Hastelloy B" " 90% - 212°F Hastelloy D

Tannic Acid 70˚F 304 Stainless SteelTar Steel (C1018), 304,

Monel, NickelTartaric Acid 70°F 304 Stainless Steel

" " 150°F 316 Stainless SteelTin Molten Cast IronTolvene Aluminum, Phosphor

Bronze, MonelTrichloroethylene Steel (C1018)Turpentine 304 Stainless SteelVarnish 304 Stainless SteelVegetable Oils Steel (C1018), 304,

MonelVinegar 304 Stainless SteelWater Fresh Copper, Steel (C1018),

Monel" Salt Aluminum

Whiskey, Wine 304, NickelXylene CopperZinc Molten Cast IronZinc Chloride MonelZinc Sulphate 5% - 70°F 304 Stainless Steel

" " Saturated - 70°F 304 Stainless Steel" " 25% - 212°F 304 Stainless Steel

This chart is a guide to selection of thermocouple sheath and thermowell materials according to process fluid. It includes factors such as catalyticreaction, contamination and electrolysis. However, there are many instances where factors other than these must be considered. It is recommendedthat such special applications be submitted to OMEGA ENGINEERING for recommendations.These recommendations are only guides based on the most economical material selection. OMEGA ENGINEERING cannot be held responsible ifthese recommendations are not satisfactory for specific applications.

SUBSTANCE CONDITIONS RECOMMENDEDMETAL SUBSTANCE CONDITIONS RECOMMENDED

METAL SUBSTANCE CONDITIONS RECOMMENDEDMETAL

Sheath Rec. Melting Environmental ConditionsMaterial Useful Point

Temp. Oxidizing Hydrogen Inert Vacuum

Molybdenum 4000ºF 4730ºF Not Fair Fair GoodRec.

Tantalum 4500ºF 5425ºF Not Not Not GoodRec. Rec. Rec.

Platinum 3050ºF 3223ºF Very Poor Poor PoorGood

Z-48

Z

THERMOELECTRIC MELTING POINTS FROMFIXED POINT THE PRACTICAL INTERNATIONAL

TEMPERATURE SCALE IPTS-68

Boiling point of oxygen -183.0 ºC -297.3 ºFSublimation point of carbon dioxide - 78.5 -109.2Freezing point of mercury - 38.9 - 38Ice Point 0 32Triple point of water 0.01 32Boiling point of water 100.0 212Triple point of benzoic acid 122.4 252.3Boiling point of naphthalene 218 424.4Freezing point of tin 231.9 449.4Boiling point of benzophenone 305.9 582.6Freezing point of cadmium 321.1 610Freezing point of lead 327.5 621.5Freezing point of zinc 419.6 787.2Boiling point of sulfur 444.7 832.4Freezing point of antimony 630.7 1167.3Freezing point of aluminum 660.4 1220.7Freezing point of siIver 961.9 1763.5Freezing point of gold 1064.4 1948Freezing point of copper 1084.5 1984.1Freezing point of palladium 1554 2829Freezing point of platinum 1772 3222

Melting Temperaturesof Some ImportantMetalsApproximate melting points are given only as a guide formaterial selection since many factors includingatmosphere, type of process, mounting, etc., all affect theoperating maximum.

Very HighTemperatureSheath Materials

Thermometry Fixed Points

°FTungsten ............

Tantalum............

Molybdenum .......

Niobium ........... .(Columbium)

Chromium ....... ...Titanium ............ Zirconium ...........

Iron................... Cobalt ............... Nickel ...............

Beryllium ........... Manganese .........

Uranium ............Copper ..............

Silver ................

Brasses

Magnesium.........

Zinc................... Lead ................. Bismuth .............Tin....................

Indium ..............

Gallium .............

Mercury .............

6000..................... Rhenium

5000..................... Osmium..................... Iridium

4000..................... Rhodium..................... Platinum..................... Vanadium3000..................... Palladium

.................... Stainless

.................... Steels

....................

....................Cast Irons

2000................Gold (24 Karat)

18 Karat12 Karat Gold Alloys10 Karat

.........Aluminum SilverSolders1000

........ Cadmium

500Common

......................Solders

0º F

Extension Grade Wires for Platinumand Tungsten-Rhenium Alloys

+ Copper Pt/Rh

LeadJunctions

– Alloy No. 11 Pt.

HotJunction

Compensating alloys made into extensionwire for tungsten-rhenium thermocouplesand platinum-rhodium thermocouplesclosely match the emf of thethermocouples over limited range

• The alloy 405/426 combination is used withTungsten 5% Re vs Tungsten 26% Re.

• The alloy 200/226 combination is used withTungsten vs Tungsten 26% Re.

• The alloy 203/225 combination is used withTungsten 3% Re vs Tungsten 25%.

• The Combination copper/alloy #11 is usedwith platinum-rhodium alloys vs pure platinum.

Z-49

RESISTIVITY TEMP COEEF. TENSILEPERCENT PURITY Ω cmil/ft OF RESISTANCE STRENGTH ELONGATION Melting

ALLOY or or (at 0º C) (0-100º C) (psi x 1000) (percent) point DensityDESIGNATION Notes composition Hard Annld Hard Annld Hard Annld Hard Annld 0C (g/cm3)

Pure MetalsIron 99.9+% 66 60 .0062 .0065 90 34 2 40 1536 7.9Nickel 99.98% 39 37 .0064 .0068 100 48 2 36 1452 8.9Molybdenum 99.9+% 42 31 .0036 .0047 250 120 2 16 2610 10.2Aluminum (H-P) 99.99+% 17.4 15 .0038 .0044 16.3 6.8 5 60 660 2.71Copper 99.98% 9.44 9.24 .0041 .0043 76 32 1.5 46 1083 8.93Gold 99.999% 13.4 13.17 .0039 .0040 46 19 1.5 36 1063 19.30Silver 99.99% 9.3 8.83 .0038 .0041 52 24 1.5 46 960.8 10.5Tungsten 99.99% 42 33 .0036 .0048 285 80 - 3 3410 19.3Rhenium 99.99% - 117 - - 360 170 - 10 3170 20.0Platium Ref 99.999+% 61.2 59.13 .00386 .00393 60 24 2 38 1769 21.45Rhodium 99.99% 33.0 25.8 .0029 .0046 275 120 2 16 1966 12.42

PlatinumPt- 6%Rh 94%Pt- 6%Rh 101 95 .0019 .0020 85 37 1.5 34 1810 20.51Pt-10%Rh 90% Pt-10% Rh 114 111 .0016 .0017 95 46 1.5 32 1830 19.95Pt-13% Rh 87% Pt-13% Rh 119 114 .0015 .0016 105 48 1.5 32 1840 19.55Pt-20% Rh 80% Pt-20% Rh 124 116 .0013 .0014 140 72 1.5 32 1870 18.65Pt-30% Rh 70% Pt-30% Rh 116 112 .0013 .0014 160 74 1.5 26 1910 17.52Pt-40% Rh 60% Pt-40% Rh 108 101 .0013 .0014 190 78 1.5 26 1920 16.54

Nickel AlloysConstantan 55% Cu-45% Ni 315 294 .00003 .00002 150 80 2 32 1270 8.86CHROMEGA® P 90% Ni-10% Cr - 425 .00032 .00032 165 95 2 27 1430 8.73ALOMEGA® 95% Ni-2% Mn-2% Al - 177 .00188 .00188 170 85 2 32 1400 8.60

Tungsten AlloysTungsten-3% Re 97% W- 3% Re - 55 - - 320 180 - 10 3410 19.4Tungsten-5% Re 95% W- 5% Re - 70 - - 320 200 - 10 3350 19.4Tungsten-25% Re 75% W-25% Re - 165 - - 300 210 - 10 3130 19.7Tungsten-26% Re 74% W-26% Re - 170 - - 300 200 - 10 3120 19.7

CompensatingAlloysAlloy #11 (1) Pt alloys - 30 - .0014 105 50 2 30 1090 8.91Alloy #200 Tungsten - 470 - - - - - - 1430 8.73Alloy #203 Tungsten- 3% Re - 470 - .0003 - - - - 1400 8.60Alloy #205 Tungsten- 5% Re - 510 - - - - - - 1410 8.58Alloy #225 Tungsten-25% Re - 180 - .0012 - - - - 1370 8.88Alloy #226 Tungsten-26% Re - 160 - - - - - - 1450 8.85Alloy #260 Tungsten-26% Re - 750 - - - - - - 1520 7.42

ThermoelectricAlloy PropertyData

1. “Percent purity or composition” column refers tomatching thermocouple grade alloy.

N=Neg Ratio of Resistance at Temperature Indicated to Resistance at 0°C (32°F)

P=Pos 0°C 20°C 200°C 400°C 600°C 800°C 1000°C 1200°C 1400°C 1500°CThermoelements (32°F) (68°F) (392°F) (752°F) (1112°F) (1472°F) (1832°F) (2192°F) (2552°F) (2732°F)

JP 1.00 1.13 2.46 4.72 7.84 12.0 13.07 … … …JN, TN, EN 1.00 0.999 0.996 0.994 1.02 1.056 1.092 … … …TP 1.00 1.11 1.86 2.75 3.70 4.75 5.96 … … …KP, EP 1.00 1.01 1.09 1.19 1.25 1.30 1.37 1.43 … …KN 1.00 1.05 1.43 1.64 1.82 1.98 2.15 2.32 … …NP 1.00 1.01 1.02 1.07 1.08 1.08 1.10 … … …NN 1.00 1.07 1.13 1.27 1.39 1.55 1.68 … … …RP 1.00 1.03 1.31 1.60 1.89 2.16 2.41 2.66 2.90 3.01SP 1.00 1.03 1.33 1.65 1.95 2.23 2.50 2.76 3.01 3.13RN, SN 1.00 1.06 1.77 2.50 3.18 3.81 4.40 4.94 5.42 5.66BP 1.00 1.03 1.26 1.51 1.76 1.98 2.20 2.41 2.62 2.73BN 1.00 1.03 1.40 1.78 2.14 2.47 2.78 3.08 3.37 3.51

Changes inThermocoupleResistancewith IncreasingTemperature

N=Neg, P=Pos Resistance of Thermocouples, ohms per foot at 20°C ( 68°F)

Awg. DiameterNo. in. KN KP,EP TN,JN,EN TP JP NP NN RN, SN RP SP BP BN

16 0.0508 0.0683 0.164 0.1113 0.00402 0.0276 .2230 .08458 0.0247 0.0456 0.0445 0.0447 0.041420 0.0320 0.173 0.415 0.287 0.0102 0.0699 .5664 .2148 0.0624 0.1149 0.1125 0.1130 0.104624 0.0201 0.438 1.05 0.728 0.0257 0.1767 1.436 .5445 0.1578 0.4656 0.2847 0.2859 0.264730 0.0100 1.77 4.25 2.94 0.1032 0.710 5.800 2.20 0.6344 2.965 1.144 1.149 1.06436 0.0050 7.08 17.0 11.8 0.4148 2.86 23.20 8.800 2.550 12.25 4.600 4.620 4.277

ANSI DESIGNATION ALLOY (Generic or Trade Names)

JP IronJN, EN, or TN Constantan, Cupron, AdvanceKP or EP CHROMEGA®, Tophel, T1, Thermokanthal KPKN ALOMEGA®, Nial, T2, Thermokanthal KNTP CopperRN or SN Pure PlatinumRP Platinum 13% RhodiumSP Platinum 10% Rhodium

Z-50

Z

ThermocoupleTypesIron-Constantan (ANSI Symbol J) The Iron-Constantan“J” curve thermocouple with a positive iron wire and anegative Constantan wire is recommended for reducingatmospheres.The operating range for this alloycombination is 1600°F for the largest wire sizes. Smallersize wires should operate in correspondingly lowertemperatures.

Copper-Constantan (ANSI Symbol T) The Copper-Constantan “T” curve thermocouple, with a positive copperwire and a negative Constantan wire, is recommended foruse in mildly oxidizing and reducing atmospheres up to750°F.They are suitable for applications where moisture ispresent.This alloy is recommended for low temperaturework since the homogeneity of the component wires canbe maintained better than with other base metal wires.Therefore, errors due to inhomogeneity of wires in zones oftemperature gradients are greatly reduced.

CHROMEGA®-ALOMEGA ® (ANSI Symbol K) TheCHROMEGA®-ALOMEGA® “K” curve thermocouple with apositive CHROMEGA® wire and a negative ALOMEGA®

wire is recommended for use in clean oxidizingatmospheres, The operating range for this alloy is 2300°Ffor the largest wire sizes. Smaller wire sizes should operatein correspondingly lower temperatures.

CHROMEGA®-Constantan (ANSI Symbol E) TheCHROMEGA®-Constantan thermocouple may be used fortemperatures up to 1600°F in a vacuum or inert, mildlyoxidizing or reducing atmosphere. At sub-zerotemperatures, the thermocouple is not subject to corrosion.This thermocouple has the highest emf output of anystandard metallic thermocouple.

Platinum-Rhodium Alloys (ANSI Symbols S, R and B)Three types of “noble-metal” thermocouples are in commonuse; they are: 1) a positive wire of 90% platinum and 10%rhodium used with a negative wire of pure platinum, 2) apositive wire of 87% platinum and 13% rhodium used witha negative wire of pure platinum, and 3) a positive wire of70% platinum and 30% rhodium used with a negative wireof 94% platinum and 6% rhodium.They have a highresistance to oxidation and corrosion. However, hydrogen,carbon and many metal vapors can contaminate aplatinum-rhodium thermocouple.The recommendedoperating range for the platinum-rhodium alloys is 2800°F,although temperatures as high as 3270°F can bemeasured with the Pt-30% Rh vs. Pt-6% Rh alloycombination.

Tungsten-Rhenlum Alloys Three types of tungsten-rhenium thermocouples are in common use for measuringtemperatures up to 5000°F.These alloys have inherentlypoor oxidation resistance and should be used in vacuum,hydrogen or inert atmospheres.

Trade Names: Advance T - Driver Harris Co., CHROMEGA® and ALOMEGA® - OMEGA Engineering, Inc., Cupron, Nial andTrophel -Wilbur B. Driver Co., Thermokanthal KP and Thermokanthal KN -The Kanthal Corporation.

ANSI LETTER DESIGNATIONS -Currently thermocouple and extension wire is ordered and specified by an ANSI letterdesignation. Popular generic and trade name examples are CHROMEGA®/ALOMEGA® -ANSI Type K: Iron/Constantan -ANSI Type J: Copper/Constantan - ANSI Type T CHROMEGA®/Constantan -ANSI Type E: Platinum/Platinum 10% Rhodium- ANSI Type S: Platinum/Platinum 13% Rhodium -ANSI Type R.The positive and negative legs are identified by letter suffixesP and N, respectively, as listed in the tables.

ANSI SymbolT Copper vs. ConstantanE CHROMEGA® vs. ConstantanJ Iron vs. ConstantanK CHROMEGA® vs. ALOMEGA®

N* OMEGALLOY®

Nicrosil-NisilG* Tungsten vs. Tungsten 26%

RheniumC* Tungsten 5% Rhenium vs.

Tungsten 26% RheniumD* Tungsten 3% Rhenium vs.

Tungsten 25% RheniumR Platinum 13% Rhodium vs.

PlatinumS Platinum 10% Rhodium vs.

PlatinumB Platinum 30% Rhodium vs.

Platinum 6% Rhodium*Not an ANSI Symbol

Trade Names of Alloys

80

70

60

50

40

30

20

10

01000 2000 3000 4000 5000

Temperature (Fahrenheit)

Mill

ivol

ts

BS

G*C*

E

J

K

N*N*N*

RT

Type K Type J Type T Type E Type S Type R Type RX/SX Type C† Type CX Type G† Type D† Type BXAWG Diameter CHROMEGA ® Iron/ Copper/ CHROMEGA ® Pt/ Pt/ Copper W5%Re/ Alloy 405 W/ W3%Re/ Copper/No. inches ALOMEGA ® Constantan Constantan Constantan PT110%Rh PT113%Rh Alloy11** W26%Re Alloy 426 W26%Re W25%Re Copper*6 0.162 0.023 0.014 0.012 0.027 0.007 0.007 0.003 0.009 0.014 0.008 0.009 0.0007908 0.128 0.037 0.022 0.019 0.044 0.011 0.011 0.004 0.015 0.023 0.012 0.015 0.001256

10 0.102 0.058 0.034 0.029 0.069 0.018 0.018 0.007 0.023 0.037 0.020 0.022 0.00199812 0.081 0.091 0.054 0.046 0.109 0.028 0.029 0.011 0.037 0.058 0.031 0.035 0.0031814 0.064 0.146 0.087 0.074 0.175 0.045 0.047 0.018 0.058 0.093 0.049 0.055 0.0050516 0.051 0.230 0.137 0.117 0.276 0.071 0.073 0.028 0.092 0.146 0.078 0.088 0.0080318 0.040 0.374 0.222 0.190 0.448 0.116 0.119 0.045 0.148 0.238 0.126 0.138 0.0127720 0.032 0.586 0.357 0.298 0.707 0.185 0.190 0.071 0.235 0.371 0.200 0.220 0.0203024 0.0201 1.490 0.878 0.7526 1.78 0.464 0.478 0.180 0.594 0.941 0.560 0.560 0.0513426 0.0159 2.381 1.405 1.204 2.836 0.740 0.760 0.288 0.945 1.503 0.803 0.890 0.0816230 0.0100 5.984 3.551 3.043 7.169 1.85 1.91 0.727 2.38 3.800 2.03 2.26 0.206432 0.0080 9.524 5.599 4.758 11.31 1.96 3.04 1.136 3.8 5.94 3.22 3.60 0.328234 0.0063 15.17 8.946 7.66 18.09 4.66 4.82 1.832 6.04 9.57 5.10 5.70 0.521836 0.0050 24.08 14.20 12.17 28.76 7.40 7.64 2.908 9.6 15.20 8.16 9.10 0.829638 0.0039 38.20 23.35 19.99 45.41 11.6 11.95 4.780 15.3 24.98 12.9 15.3 1.319240 0.00315 60.88 37.01 31.64 73.57 18.6 19.3 7.327 24.4 38.30 20.6 23.0 2.09844 0.0020 149.6 88.78 76.09 179.20 74.0 76.5 18.18 60.2 95.00 51.1 56.9 5.13450 0.0010 598.4 355.1 304.3 716.9 185 191 72.7 240 380.0 204 227 20.6456 0.00049 2408 1420 1217 2816 740 764 302.8 1000 1583 850 945 86.38

Resistance Vs. Wire Diameter

*Increase the resistance by 19% for nickel plated, type RTD wire **Maximum Resistance of reviewed wire †Not ANSI symbol

Z-51Z-51

Comparison of Time Constant* vs. OverallOutside Diameter of Bare Thermocouple Wiresor Grounded Junction Thermocouples In AirTime constants calculated for air atroom temperature and atmosphericpressure moving with velocity of65 feet per second for thermocouplesshown in Figures #1 and #2.

For beaded-type and ungroundedjunctions (Figures #3 or #4), multiplytime constants by 1.5.

Time constant of thermocouple madewith exposed butt welded 0.001 inchdia. wire = .003 sec.

DD

BARE WIREButt Welded

Fig. #1

GROUNDEDJunctionFig. #2

D DBEADED-TYPEThermocouple

Fig. #3

UNGROUNDED-TYPE

ThermocoupleFig. #4

* The “Time Constant” or “Response TIme” is definedas the time required to reach 63.2% of an instantaneoustemperature change.

TIM

E C

ON

STA

NT

- S

EC

ON

DS

TIM

E C

ON

STA

NT

- S

EC

ON

DS

WIRE OR SHEATH DIAMETER - INCHES “D”

Time constant of thermocouple made withexposed, butt welded0.001 in. dia. wire= .003 sec.

.001.002 .004 .006 .008 .010 .012 .014 .016 .018 .020 .022 .024 .026 .028 .030 .032 .034

1.2

1.1

1.0

.9

.8

.7

.6

.5

.4

.3

.2

.1

0.0

2.1

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.01/64 in. 1/32 in.

TIM

E C

ON

STA

NT

- S

EC

ON

DS

TIM

E C

ON

STA

NT

- S

EC

ON

DS

WIRE OR SHEATH DIAMETER - INCHES “D”

.03125 .0625 .09375 .125 .15625 .1875 .21875 .250 .28125 .3125 .375

1/32 1/16 3/32 1/8 5/32 3/16 7/32 1/4 9/32 5/16 3/8

11.0

10.0

9.0

8.0

7.0

6.0

5.0

4.0

3.0

2.0

1.0

110

100

90

80

70

60

50

40

30

20

10

1.8 sec.

Figure M Sheath Diameter 1⁄32" to 3⁄8 "

Because of space limitations,time constant curve is dividedinto 4 separate curves.

Note:These comparisons apply to either bare “butt-welded” or “grounded” junction thermocouples. If the thermocouples are the “beaded” type or“ungrounded,” the time constant is longer. These times are only approximate and are provided for comparison purposes only. Multiply valuesfrom Time Constants by 1.5 for junctions shown in Fig. #3 and Fig. #4.

Z-52

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Metal SheathedThermocouple ProbeTime Response Study in Water

2.25

2.00

1.75

1.50

1.25

1.00

.75

.50

.25

.05 .10 .15 .20 .25

.040 .062

.125

.188

.250 Ungrounded

Grounded

Exposed

Probe Diameter in Inches

Tim

e in

Sec

onds

Z-53

Thermistors can be used in a variety of ways. Here are afew typical applications. If you have questions concerningthese or other thermistor uses, we will be happy todiscuss them.

TEMPERATURE MEASUREMENT-A thermistor in oneleg of a Wheatstone bridge circuit will provide precisetemperature information. Accuracy is limited in mostapplications only by the readout device. See Figure 1.

Since lead length between thermistor and bridge is notnormally a limiting factor, this basic system can beexpanded to measure temperature at several locationsfrom a central point. Thermistor interchangeability andlarge resistance change eliminate any significant errorfrom switches or lead length. See Figure 2.

METER COMPENSATION - The coil resistance of ameter movement changes with temperature, making themeter temperature dependent. Using the thermistor’sproperty of a high negative temperature coefficient, thecoil can be compensated so total resistance due totemperature rise is essentially constant, allowing themeter to be used over a wide temperature range withminimal error. See Figure 3.

DIFFERENTIAL THERMOMETERS -For accurateindication of temperature differential, two thermistors canbe used in a Wheatstone bridge circuit. Thermistorinterchangeability simplifies circuit design and reducesthe number of components. See Figure 4.

To measure heat loss in a piping network, thermistors

can be placed at various points and the differencebetween these temperatures and the originaltemperature monitored at a convenient location.

Measuring air temperature at different elevations withreference to ground temperature is useful for temperatureinversion data and geological studies. See Figure 5.

TEMPERATURE CONTROL-A system can be designedusing a thermistor with a known temperature/ resistancecurve to form one leg of an AC bridge and a variableresistor calibrated in temperature to form another leg.When the resistor is set to a desired temperature, bridgeunbalance occurs. This unbalance is fed into an amplifierwhich actuates a relay to provide a source of heat orcold. When the thermistor senses the desiredtemperature, the bridge is balanced, opening the relayand turning off the heat or cold. See Figure 6.

MASTER-SLAVE CONTROL -Occasionally there is aneed to control one temperature with respect to another,such as a product going through a series of baths. Thefirst bath acts as a master and uses a thermistor to sensetemperature. Succeeding baths, also using thermistors,are slaves. When these thermistors are placed in thecontroller bridge, the slave baths can be kept at atemperature relative to the master bath.

The master bath can be controlled with the systemdescribed earlier. The master-slave controller can beused for as many baths as necessary. See Figure 7.

OMEGA® InterchangeableThermistor Applications

®

referencethermistor

difference# 2

difference# 1

variableresistor

for batterycontrol

meter coil2150 ohms

at 25°C

at 25°C

thermistor

variableresistor

for batterycontrol

thermistor

thermistor

variableresistor

for batterycontrol

Fig. 1 Fig. 4 Fig. 6

Fig. 7Fig. 5Fig. 2

thermistor

high gainamplifier

variable resistorfor setting desired

temperature relay

thermistor

amplifier

for setting desiredtemperature relay

thermistormaster

thermistorslave

high gainamplifier

relay

amplifier

variable resistorfor adjusting slave

temperature slightlyabove or below

temperature

oven# 1

oven# 2

refrigeratorchamber

pressurechamber

roomtemperature

selectorswitch

variableresistor

for batterycontrol

thermistor1000 ohms at 25°C

resistor1000 ohms

INTRODUCTION Resistance elements come in manytypes conforming to different standards,capable of different temperatureranges, with various sizes andaccuracies available. But they allfunction in the same manner: each hasa pre-specified resistance value at aknown temperature which changes in apredictable fashion. In this way, bymeasuring the resistance of theelement, the temperature of theelement can be determined fromtables, calculations or instrumentation.These resistance elements are theheart of the RTD (ResistanceTemperature Detector). Generally, abare resistance element is too fragileand sensitive to be used in its raw form,so it must be protected by incorporatingit into an RTD. A

Resistance Temperature Detector isa general term for any device thatsenses temperature by measuring thechange in resistance of a material.RTD’s come in many forms, but usuallyappear in sheathed form. An RTDprobe is an assembly composed of aresistance element, a sheath, lead wireand a termination or connection. Thesheath, a closed end tube, immobilizesthe element, protecting it againstmoisture and the environment to bemeasured. The sheath also providesprotection and stability to the transitionlead wires from the fragile elementwires.

Some RTD probes can be combinedwith thermowells for additionalprotection. In this type of application,the thermowell may not only addprotection to the RTD, but will also sealwhatever system the RTD is tomeasure (a tank or boiler for instance)from actual contact with the RTD. Thisbecomes a great aid in replacing theRTD without draining the vessel orsystem.

Thermocouples are the old tried andtrue method of electrical temperaturemeasurement. They function verydifferently from RTD’s but generallyappear in the same configuration: oftensheathed and possibly in a thermowell.

Basically, they operate on the Seebeckeffect, which results in a change inthermoelectric emf induced by achange in temperature. Manyapplications lend themselves to eitherRTD’s or thermocouples.Thermocouples tend to be morerugged, free of self-heating errors andthey command a large assortment ofinstrumentation. However, RTD’s,especially platinum RTD’s, are morestable and accurate.

RESISTANCE ELEMENTCHARACTERISTICS

There are several very importantdetails that must be specified in orderto properly identify the characteristicsof the RTD:

1. Material of Resistance Element (Platinum, Nickel, etc.)

2. Temperature Coefficient 3. Nominal Resistance 4. Temperature Range of

Application 5. Physical Dimensions or

Size Restrictions 6. Accuracy

1. Material of Resistance ElementSeveral metals are quite common foruse in resistance elements and thepurity of the metal affects itscharacteristics. Platinum is by far themost popular due to its linearity withtemperature. Other common materialsare nickel and copper, although most ofthese are being replaced by platinumelements. Other metals used, thoughrarely, are Balco (an iron-nickel alloy),tungsten and iridium.

2.Temperature CoefficientThe temperature coefficient of anelement is a physical and electricalproperty of the material. This is a termthat describes the average resistancechange per unit of temperature from icepoint to the boiling point of water.Different organizations have adopteddifferent temperature coefficients astheir standard. In 1983, the IEC(International ElectrotechnicalCommission) adopted the DIN(Deutsche Institute for Normung)standard of Platinum 100 ohm at 0ºCwith a temperature coefficient of0.00385 ohms per ohm degreecentigrade. This is now the acceptedstandard of the industry in mostcountries, although other units arewidely used. A quick explanation ofhow the coefficient is derived is asfollows: Resistance at the boiling point(100ºC) =138.50 ohms. Resistance atice point (0ºC) = 100.00 ohms. Dividethe difference (38.5) by 100 degreesand then divide by the 100 ohm

nominal value of the element. Theresult is the mean temperaturecoefficient (alpha) of 0.00385 ohms perohm per ºC.

Some of the less common materialsand temperature coefficients are:

Pt TC = .003902 (U.S. IndustrialStandard)

Pt TC = .003920 (Old U.S.Standard)

Pt TC = .003923 (SAMA)Pt TC = .003916 (JIS)Copper TC = .0042Nickel TC = 0.00617 (DIN)Nickel TC = .00672 (Growing

Less Common in U.S.)Balco TC = .0052Tungsten TC = 0.0045

Please note that the temperaturecoefficients are the average valuesbetween 0 and 100ºC. This is not tosay that the resistance vs. temperaturecurves are truly linear over thespecified temperature range.

3. Nominal Resistance

Nominal Resistance is the pre-specified resistance value at a giventemperature. Most standards, includingIEC-751, use 0ºC as their referencepoint. The IEC standard is 100 ohms at0ºC, but other nominal resistances,such as 50, 200, 400, 500, 1000 and2000 ohm, are available.

4.Temperature Range of ApplicationDepending on the mechanicalconfiguration and manufacturingmethods, RTD’s may be used from-270ºC to 850ºC. Specifications fortemperature range will be different, forthin film, wire wound and glassencapsulated types, for example.

5. Physical Dimensions or SizeRestrictions The most critical dimension of theelement is outside diameter (O.D.),because the element must often fitwithin a protective sheath. The film typeelements have no O.D. dimension. Tocalculate an equivalent dimension, weneed to find the diagonal of an endcross section (this will be the widestdistance across the element as it isinserted into a sheath).

Z-54

Z

Resistance Elements and RTD’sDavid J. King

Permissible deviations from basicvalues

For example, using an element that is10 x 2 x 1.5 mm, the diagonal can befound by taking the square root of (22 +1.52).Thus, the element will fit into a2.5 mm (0.98") inside diameter hole. Forpractical purposes, remember that anyelement 2 mm wide or less will fit into a

1/8" O.D. sheath with 0.010" walls,generally speaking. Elements which are1.5 mm wide will typically fit into asheath with 0.084" bore. Refer to Figure1.

6. Accuracy

IEC 751 specifications for PlatinumResistance Thermometers haveadopted DIN 43760 requirements foraccuracy. DIN-IEC Class A and Class Belements are shown in the chart on thispage.

7. Response Time

50% Response is the time thethermometer element needs in order toreach 50% of its steady state value.90% Response is defined in a similarmanner.These response times ofelements are given for water flowingwith 0. 2 m/s velocity and air flowing at1 m/s.They can be calculated for anyother medium with known values ofthermal conductivity. In a 1/4" diametersheath immersed in water flowing at3 feet per second, response time to63% of a step change in temperature isless than 5.0 seconds.

8. Measurement Current and SelfHeating

Temperature measurement is carriedout almost exclusively with directcurrent. Unavoidably, the measuringcurrent generates heat in the RTD.Thepermissible measurement currents aredetermined by the location of theelement, the medium which is to bemeasured, and the velocity of movingmedia. A self-heating factor, “S”, givesthe measurement error for the elementin ºC per milliwatt (mW).With a givenvalue of measuring current, I, themilliwatt value P can be calculated fromP = I2R, where R is the RTD’sresistance value.The temperaturemeasurement error ∆T (ºC) can then becalculated from ∆T = P x S.

RESISTANCE ELEMENTSPECIFICATIONSStability: Better than 0.2ºC after

10,000 hours at maximum temperature(1 year, 51 days, 16 hours continuous).

Vibration Resistance: 50 g @ 500ºC;200 g @ 20ºC; at frequencies from 20to 1000 cps.

Temperature Shock Resistance: Inforced air: over entire temperaturerange. In a water quench: from 200 to20ºC.

Pressure Sensitivity: Less than 1.5 x10-4 C/PSI, reversible.

Self Heating Errors & ResponseTimes: Refer to specific TemperatureHandbook pages for the type ofelement selected.

Self Inductance From SensingCurrent: Can be considered negligiblefor thin film elements; typically less than0.02 microhenry for wire woundelements.

Capacitance: For wire wound elements:calculated to be less than 6 PicoFarads;for film-type elements: capacitance is toosmall to be measured and is affected bylead wire connection. Lead connectionswith element may indicate about 300 pFcapacitance.

LEAD WIRECONFIGURATIONSAs stated previously, a ResistanceTemperature Detector (RTD) elementgenerally appears in a sheathed form.Obviously, all of the criteria applicable toresistance elements also apply here,but rather than element size, theconstruction and dimensions of theentire RTD assembly must beconsidered. Since the lead wire usedbetween the resistance element and themeasuring instrument has a resistanceitself, we must also supply a means ofcompensating for this inaccuracy. Referto Figure 2 for the 2-wire configuration.

FIGURE 2. 2-WIRECONFIGURATION (STYLE 1)

The circle represents the resistanceelement boundaries to the point ofcalibration. 3- or 4-wire configurationmust be extended from the point ofcalibration so that all uncalibratedresistances are compensated.

Class ATemperature Deviation

º C ohms º C-200 ±0.24 ±0.55

-100 ±0.14 ±0.35

0 ±0.06 ±0.15

100 ±0.13 ±0.35

200 ±0.20 ±0.55

300 ±0.27 ±0.75

400 ±0.33 ±0.95

500 ±0.38 ±1.15

600 ±0.43 ±1.35

650 ±0.46 ±1.45

Class BTemperature Deviation

º C ohms º C-200 ±056 ±1.3

-100 ±0.32 ±0.8

0 ±0.12 ±0.3

100 ±0.30 ±0.8

200 ±0.48 ±1.3

300 ±0.64 ±1.8

400 ±0.79 ±2.3

500 ±0.93 ±2.8

600 ±1.06 ±3.3

650 ±1.13 ±3.6

700 ±1.17 ±3.8

800 ±1.28 ±4.3

850 ±1.34 ±4.6

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Resistance Elements and RTD’s Cont’d

BLACK

RED

ELEMENT

R E

R 1

R 2

THICKNESS OF ELEMENT

WALL THICKNESSDIAGONAL OF ELEMENT

ODW W = WIDTH OF ELEMENT

FIGURE 1. LOCATION OF THIN FILM ELEMENT IN CYLINDRICAL SHEATH

The resistance RE is taken from theresistance element and is the valuethat will supply us with an accuratetemperature measurement.Unfortunately, when we take ourresistance measurement, theinstrument will indicate RTOTAL:Where RT = R1 + R2 + RE

This will produce a temperaturereadout higher than that actuallybeing measured. Many systems canbe calibrated to eliminate this. MostRTD’s incorporate a third wire withresistance R3. This wire will beconnected to one side of theresistance element along with lead2 as shown in Figure 3.

This configuration provides oneconnection to one end and two tothe other end of the sensor.Connected to an instrumentdesigned to accept 3-wire input,compensation is achieved for leadresistance and temperature changein lead resistance. This is the mostcommonly used configuration.


If three identical type wires are usedand their lengths are equal, then R1= R2 = R3. By measuring theresistance through leads 1, 2 andthe resistance element, a totalsystem resistance is measured (R1+ R2 + RE ). If the resistance is alsomeasured through leads 2 and 3 (R2+ R3), we obtain the resistance ofjust the lead wires, and since alllead wire resistances are equal,subtracting this value (R2 + R3) fromthe total system resistance (R1 + R2+ RE) leaves us with just RE, and anaccurate temperature measurementhas been made. A 4-wireconfiguration is also used. (SeeFigure 4.) Two connections are

provided to each end of the sensor.This construction is used formeasurements of the highestprecision.


With the 4-wire configuration, theinstrument will pass a constantcurrent (I) through the outer leads, 1and 4.

The voltage drop is measuredacross the inner leads, 2 and 3. Sofrom V = IR we learn the resistanceof the element alone, with no effectfrom the lead wire resistance. Thisoffers an advantage over 3-wireconfigurations only if dissimilar leadwires are used, and this is rarely the

case.

Still another configuration, now rare,is a standard 2-wire configurationwith a closed loop of wire alongside(Figure 5). This functions the sameas the 3-wire configuration, but usesan extra wire to do so. A separatepair of wires is provided as a loop toprovide compensation for leadresistance and ambient changes inlead resistance.

FIGURE 5. 2-WIRECONFIGURATION PLUS LOOP(STYLE 4)

Z-56

ZR E

BLACK

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ELEMENT

BLACK

RED R 1

R 2

R 3

R 4

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®

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Why should I use an infrared pyrometer to measuretemperature in my application?Infrared pyrometers allow users to measure temperature inapplications where conventional sensors cannot be employed.Specifically, in cases dealing with moving objects (i.e., rollers,moving machinery, or a conveyer belt), or where non-contactmeasurements are required because of contamination orhazardous reasons (such as high voltage), where distancesare too great, or where the temperatures to be measured aretoo high for thermocouples or other contact sensors.

What should I consider about my application when selectingan infrared pyrometer?The critical considerations for any infrared pyrometer includefield of view (target size and distance), type of surface beingmeasured (emissivity considerations), spectral response (for atmospheric effects or transmission through surfaces),temperature range and mounting (handheld portable or fixed mount). Other considerations include response time,environment, mounting limitations, viewing port or windowapplications, and desired signal processing.

FIELD OF VIEWWhat is meant by Field of View, and why is it important?The field of view is the angle of vision at which the instrumentoperates, and is determined by the optics of the unit. Toobtain an accurate temperature reading, the target beingmeasured should completely fill the field of view of theinstrument. Since the infrared device determines the averagetemperature of all surfaces within the field of view, if thebackground temperature is different from the objecttemperature, a measurement error can occur (figure 1).

Most general purpose indicators have a focal distancebetween 20 and 60". The focal distance is the point at whichthe minimum measurement spot occurs. For example, a unitwith a distance-to-spot size ratio of 120:1, and a focal lengthof 60" will have a minimum spot size of 0.5" at 60" distance.Close-focus instruments have a typical 0.1 to 12" focal length,while long-range units can use focal distances on the order of 50'. Many instruments used for long distances or small spot sizes also include sighting scopes for improved focusing.Field of view diagrams are available for most instruments tohelp estimate spot size at specific distances.

EMISSIVITYWhat is emissivity, and how is it related to infraredtemperature measurements?Emissivity is defined as the ratio of the energy radiated by an object at a given temperature to the energy emitted by a perfect radiator, or blackbody, at the same temperature. The emissivity of a blackbody is 1.0. All values of emissivityfall between 0.0 and 1.0.

Emissivity (ε), a major but not uncontrollable factor in IRtemperature measurement, cannot be ignored. Related toemissivity are reflectivity (R), a measure of an object’s ability to reflect infrared energy, and transmissivity (T), a measure ofan object’s ability to pass or transmit IR energy. All radiationenergy must be either emitted (E) due to the temperature ofthe body, transmitted (T) or reflected (R). The total energy, thesum of emissivity, transmissivity and reflectivity is equal to 1:

E + T + R = 1.0

The ideal surface for infrared measurements is a perfectradiator, or a blackbody with an emissivity of 1.0. Most objects,however, are not perfect radiators, but will reflect and/ortransmit a portion of the energy. Most instruments have the ability to compensate for different emissivity values, for different materials. In general, the higher the emissivity of an object, the easier it is to obtain an accurate temperaturemeasurement using infrared. Objects with very low emissivities(below 0.2) can be difficult applications. Some polished, shinymetallic surfaces, such as aluminum, are so reflective in theinfrared that accurate temperature measurements are notalways possible.

Object A Object B

Wall

InfraredPyrometer

HotSource

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Introduction to Infrared Pyrometers

Figure 1: Field of view

Total infrared radiation reaching pyrometers

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Reflectivity is usually a more important consideration thantransmission except in a few special applications, such as thin film plastics. The emissivity of most organic substances(wood, cloth, plastics, etc.) is approximately 0.95. Most roughor painted surfaces also have fairly high emissivity values.

FIVE WAYS TO DETERMINE EMISSIVITYThere are five ways to determine the emissivity of thematerial, to ensure accurate temperature measurements:

1. Heat a sample of the material to a known temperature,using a precise sensor, and measure the temperature usingthe IR instrument. Then adjust the emissivity value to forcethe indicator to display the correct temperature.

2. For relatively low temperatures (up to 500°F), a piece ofmasking tape, with an emissivity of 0.95, can be measured.Then adjust the emissivity value to force the indicator todisplay the correct temperature of the material.

3. For high temperature measurements, a hole (depth of whichis at least 6 times the diameter) can be drilled into the object.This hole acts as a blackbody with emissivity of 1.0. Measurethe temperature in the hole, then adjust the emissivity to forcethe indicator to display the correct temperature of the material.

4. If the material, or a portion of it, can be coated, a dull black paint will have an emissivity of approx. 1.0. Measure the temperature of the paint, then adjust the emissivity toforce the indicator to display the correct temperature.

5. Standardized emissivity values for most materials areavailable (see pages 114-115). These can be entered into the instrument to estimate the material’s emissivity value.

SPECTRAL RESPONSEWhat is spectral response, and how will it affect my readings?

The spectral response of the unit is the width of the infraredspectrum covered. Most general purpose units (fortemperatures below 1000°F) use a wideband filter in the 8 to14 micron range. This range is preferred for mostmeasurements, as it will allow measurements to be takenwithout the atmospheric interference (where the atmospherictemperature affects the readings of the instrument). Someunits use wider filters such as 8 to 20 microns, which can beused for close measurements, but are ‘‘distance-sensitive’’against longer distances. For special purposes, very narrowbands may be chosen. These can be used for highertemperatures, and for penetrations of atmosphere, flames,and gases. Typical low band filters are at 2.2 or 3.8 microns.High temperatures above 1500°F are usually measured with2.1 to 2.3 micron filters. Other bandwidths that can be usedare 0.78 to 1.06 for high temperatures, 7.9 or 3.43 for limitedtransmissions through thin film plastics, and 3.8 microns topenetrate through clean flames with minimum interference.

TEMPERATURE MEASUREMENT THROUGH GLASSI want to measure the temperature through a glass or quartzwindow; what special considerations are there?

Transmission of the infrared energy through glass or quartz is an important factor to be considered. The pyrometer musthave a wavelength where the glass is somewhat transparent,which means they can only be used for high temperature.Otherwise, the instrument will have measurement errors due to averaging of the glass temperature with the desiredproduct temperature.

MOUNTINGHow can I mount the infrared pyrometer?

The pyrometer can be of two types, either fixed-mount orportable. Fixed mount units are generally installed in onelocation to continuously monitor a given process. They usually operate on line power, and are aimed at a single point. The output from this type of instrument can be a local or remote display, along with an analog output that can beused for another display or control loop.Battery powered, portable infrared ‘‘guns’’ are also available;these units have all the features of the fixed mount devices,usually without the analog output for control purposes.Generally these units are utilized in maintenance, diagnostics,quality control, and spot measurements of critical processes.

RESPONSE TIMEWhat else should I take into account when selecting andinstalling my infrared measurement system?

First, the instrument must respond quickly enough to processchanges for accurate temperature recording or control.Typical response times for infrared thermometers are in the 0.1 to 1 second range. Next, the unit must be able tofunction within the environment, at the ambient temperature.Other considerations include physical mounting limitations,viewing port/window applications (measuring through glass),and the desired signal processing to produce the desiredoutput for further analysis, display or control.

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Principles of InfraredThermometry W. R. Barron, Williamson Corporation

The fundamentals of IR thermometryare an important prerequisite forspecifying an accurate monitoringsystem. Unfortunately, many users do not take the time to understand the basic guidelines, and consequentlyreject the concept of noncontacttemperature measurement as inaccurate.

THEORY AND FUNDAMENTALSTemperature measurement can bedivided into two categories: contact andnoncontact. Contact thermocouples,RTDs, and thermometers are the mostprevalent in temperature measurementapplications. They must contact thetarget as they measure their owntemperature and they are relatively slowresponding, but they are inexpensive.Noncontact temperature sensorsmeasure IR energy emitted by thetarget, have fast response, and arecommonly used to measure moving andintermittent targets, targets in a vacuum,and targets that are inaccessible due to hostile environments, geometrylimitations, or safety hazards. The costis relatively high, although in somecases is comparable to contact devices.

Infrared radiation was discovered in1666 by Sir Isaac Newton, when heseparated the electromagnetic energyfrom sunlight by passing white lightthrough a glass prism that broke up thebeam into colors of the rainbow. In1800, Sir William Herschel took the nextstep by measuring the relative energy ofeach color. He also discovered energybeyond the visible. In the early 1900s,Planck, Stefan, Boltzmann, Wien, andKirchhoff further defined the activity of the electromagnetic spectrum anddeveloped quantitative data and equationsto identify IR energy.

This research makes it possible to defineIR energy using the basic blackbodyemittance curves (See Figure 1). Fromthis plot it can be seen that objects (of atemperature greater than -273°C) emitradiant energy in an amount proportionalto the fourth power of their temperature.The concept of blackbody emittance is the foundation for IR thermometry.There is, however, the term “emissivity”that adds a variable to the basic laws ofphysics. Emissivity is a measure of theratio of thermal radiation emitted by a

graybody (non-blackbody) to that of ablackbody at the same temperature. (A graybody refers to an object that hasthe same spectral emissivity at everywavelength; a non-graybody is an objectwhose emissivity changes withwavelength, e.g. aluminum.)

The law of conservation of energy statesthat the coefficient of transmission,reflection, and emission (absorption) of radiation must add up to 1:

tl + rl + al = 1

and the emissivity equals absorptivity:

El = al

Therefore:

El = 1 - tl - rl

This emissivity coefficient fits into Planck’sequation as a variable describing theobject surface characteristics relative to wavelength. The majority of targetsmeasured are opaque and the emissivitycoefficient can be simplified to:

El = 1 - rl

Exceptions are materials like glass,plastics, and silicon, but through properselective spectral filtering it is possibleto measure these objects in theiropaque IR region.

There is typically a lot of confusionregarding emissivity error, but the userneed remember only four things:– IR sensors are inherently colorblind.– If the target is visually reflective (like a

mirror), beware – you will measure notonly the emitted radiation, as desired,but also reflected radiation.

– If you can see through it, you need toselect IR filtering (e.g., glass isopaque at 5µm).

– Nine out of ten applications do not requireabsolute temperature measurement.Repeatability and drift-free operationyield close temperature control.

If the surface is shiny, there is anemissivity adjustment that can be madeeither manually or automatically to correctfor emissivity error. It is a simple fix for most applications. In cases whereemissivity varies and creates processingproblems, consider dual- or multiwave-length radiometry to eliminate theemissivity problem.

DESIGN ELEMENTSIR thermometers come in a wide varietyof configurations pertaining to optics,electronics, technology, size, andprotective enclosures. All, however,have a common chain of IR energy inand an electronic signal out. This basicchain consists of collecting optics, lenses,and/or fiber optics, spectral filtering, anda detector as the front end. Dynamicprocessing comes in many forms, butcan be summarized as amplification,thermal stability, linearization, andsignal conditioning. Normal window

LGBE =LBB

109876543210

600°F

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STEFAN-BOLTZMANN LAW Q = sT4

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Figure 1: As shown in curves representing thedistribution of energy emitted by blackbodiesranging in temperature from 600°F to 1200°F,the predominant radiation is in the IR regionof 0.5-14 µm, well beyond the visible region.

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Zglass is usable at the short wavelength,quartz for the midrange, and germaniumor zinc sulfide for the 8-14 µm range.Fiber optics are available to cover the0.5-5.0 µm region.

From an applications standpoint, theprimary characteristic of the optics is the field of view (FOV), i.e., what is thetarget size at a prescribed distance? A very common lens system, for example,would be a 1 in. dia. target size at a 15 in. working distance. Using the inversesquare law, by doubling the distance (30 in.) the target area theoreticallydoubles (2 in. dia.). The actual definitionof target size (area measured) will varydepending upon the supplier, and it is price dependent. Other opticalconfigurations vary from small spot(0.030 in dia.) for close-up pinpointmeasurement, to distant optics (3 in. at 30 ft) for distant aiming. It is importantto note that working distance should notaffect the accuracy if the FOV is filled bythe target. In one technique for measuringFOV, the variable is signal loss vs.diameter. A strict rule is a 1% energyreduction, although some data arepresented at half power, or 63.2%

Alignment (aiming) is another opticalfactor. Many sensors lack thatcapability; the lens is aligned to thesurface and measures surface temperature.This works with sizable targets, e.g.,paper web, where pinpoint accuracy is not required. For small targets that use small-spot optics, and for distantoptics used in remote monitoring, thereare options of visual aiming, aim lights,and laser alignment.

Selective spectral filtering typically uses short-wavelength filters for high-temperature applications (>1000°F, and long-wavelength filters for lowtemperatures –50°F). This obviously fits the blackbody distribution curves,and there are some technologicaladvantages. For example, hightemperature/short wavelength uses a very thermally stable silicon detector,and the short-wavelength designminimizes temperature error due toemissivity variations. Other selectivefiltering is used for plastic films (3.43 µmand 7.9 µm), glass (5.1 µm), and flameinsensitivity (3.8 µm).

A variety of detectors are used tomaximize the sensitivity of the sensor.As shown in Figure 2, PbS has thegreatest sensitivity, while the thermopilehas the least sensitivity. Most detectorsare either photovoltaic, putting out a voltage when energized, orphotoconductive, changing resistancewhen excited. These fast-responding,high sensitive detectors have a tradeoffthermal drift that can be overcome inmany ways, including temperaturecompensation (thermistors) circuitry,temperature regulation, auto nullcircuitry, chopping (AC vs. DC output),and isothermal protection. Drift-freeoperation is available in varying degreesand is price dependent.

In the IR thermometer’s electronicspackage, the detector’s nonlinear outputsignal, on the order of 100-1000 µV, is processed. The signal is amplified1000 x, regulated, and linearized, andthe ultimate output is a linear mV or mAsignal. The trend is toward 4-20 mAoutput to minimize environmentalelectrical noise interference.

This signal can also be transposed toRS 232 or fed to a PID controller, remotedisplay, or recorder. Additional signalconditioning options involve on/off alarms,adjustable peak hold for intermittenttargets, adjustable response time,and/or sample-and-hold circuitry.

On the average, IR thermometers havea response time on the order of 300 ms,although signal outputs on the order of 10 ms can be obtained with silicondetectors. In the real world, manyinstruments have an adjustable responsecapability that permits damping of noisyincoming signals and field adjustmenton sensitivity. It is not always necessaryto have the fastest response available.There are cases involving inductionheating and other types of applications,however, where response times on theorder of 10-50 ms are required, and theyare attainable through IR thermometry.

SINGLE-WAVELENGTHTHERMOMETRYThe basic single-wavelength designmeasures total energy emitted from asurface at a prescribed wavelength. The configurations range from handheldprobes with a simple remote meter tosophisticated portables with simultaneousviewing of target and temperature, plusmemory and/or printout capabilities. On-line, fixed-mount sensors range from simple small detectors with remoteelectronics (OEM designs) to ruggeddevices with remote PID control. Fiber optics, laser aiming, water cooling,CRT display, and scanning systems areamong the options for process monitoringand control applications. There aremany variations in size, performance,ruggedness, adaptability, and signalconditioning.

Process sensor configuration, IRspectral filtering, temperature range,optics, response time, and targetemissivity are important engineeringelements that affect performance andwhich must be given careful considerationduring the selection process.

The sensor configuration can be aportable, a simple two-wire transmitter,a sophisticated ruggedized sensing unit,or a scanning device. Visual aiming,laser alignment, non-aiming, fiberoptics, water cooling, output signals,and remote displays represent anoverview of the various options. Theseare somewhat subjective, but demandengineering review. In most cases, if it is a simple application, e.g., webtemperature, a simple low-cost sensorwould do the job; if the application is

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Figure 2: To optimize the respone of IR sensingsystems, the detector’s spectral response andmodulation characteristics must be considered.

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complicated, e.g., vacuum chamber orsmall target, then a more sophisticatedsensor is a better choice.

The selection of IR spectral responseand temperature range is related to aspecific application. Short wavelengthsare for high temperature and longwavelengths are for low temperature, tocoincide with the blackbody distributioncurves. If transparent-type targets are involved, e.g., plastics and glass,then selective narrow-band filtering isrequired. For example, polyethylene filmhas a CH absorption band of 3.43 µm,where it becomes opaque. By filtering in this region, the emissivity factor issimplified. Likewise, most glass-typematerials become opaque at 4.6 µm andnarrow-band filtering at 5.1 µm permitsaccurate measurement of glass surfacetemperature. On the other hand, to lookthrough a glass window, a sensor filteredin the 1-4 µm region would allow easyaccess via viewing ports into vacuumand pressure chambers. Another option,in the case of chambers, is to use afiber-optic cable with a vacuum orpressure bushing.

Optics and response time are twosensor characteristics that are, in mostapplications, nonissues, in that thestandard FOV of approximately 1 in. at15 in. is acceptable, and response timeof <1 s is adequate. If the applicationrequires a small target or a fast-movingintermittent target, however, then smallspot (0.125 in dia.) and very small spot(0.030 in. dia.) may be applicable at apremium. Likewise, distant sighting (10-1000 ft away from the target) willalso require an optical adjustment, asthe standard FOV will become very large.In some instances, dual-wavelengthradiometry is used for these applications,.e.g., wire and distant sighting. Thefiber-optic front-end offers engineeringflexibility by remoting the electronicsfrom hostile environments, eliminatingelectrical noise interference and resolvingaccessibility concerns. It is an intriguingengineering tool that helps solve someunique application problems.

Most sensors have adjustable responsein the 0.2-5.0 s range, and typicalsettings are in the midrange. Fastresponse can expose application noise,while slow response affects sensitivity.Induction heating requires fast response,while conveyor or web monitoringrequires a slower response to reduceapplication noise. A fast-respondingsensor requires a fast-respondingcontroller, SCR power pack, and otherregulators. Integrated system dynamicscan be defined by the following equation:

where:

T = total response

t1,t2= individual elements of the loop

Considering the element of time, thereare two types of process dynamics:steady state variations, where there is afast-moving product that requires closetemperature control due to the dynamicsof the process, e.g., induction heating of wire. Step changes or ramp responsepertains to the very quick heating of aproduct in a batch process, e.g., rapidthermal annealing of silicon wafers. In these dynamic applications, systemresponsivity and sensor FOV are criticalparameters.

In many cases, target emissivity is not a significant factor. With the properselection of narrow-band spectral filtering,most materials have a constant emissivityin the 0.90 ±0.05 range. Setting theemissivity at 0.9 µm, the sensor will tendto read within ±5° or 10° of absolutetemperature. This application errorrepresents an accuracy variation of about1% or 2% but, in the real world of IRthermometry, repeatability is critical for control. If, for example, a product isheated to 410°F and the sensor reads400°F, and you make quality productwhen the sensor indicates 390-410°F,use the 400 setpoint for control. Mostapplications do not require NIST calibrationstandards to produce quality product.

If an application requires accurate,absolute temperature measurement and documentation, the instruments canbe calibrated and certified to referencedNIST standards. In addition, there is theneed to fully define the application errordue to surface emissivity. If a shiny roll must be measured, e.g., the firstrecommendation is to measure theproduct passing on the shiny roll.Second, the emissivity adjustment can be made on the sensor using statictesting conditions to determine theproper setting. Third, dual-wavelengthradiometry may be a viable option.

Single-wavelength IR thermometryrepresents a very diversified, yet simple,selection technique used in thousandsof applications where product temperaturecontrol is vital for consistent, high-qualityproducts.

DUAL-WAVELENGTHTHERMOMETRYFor more sophisticated applicationswhere absolute accuracy is critical, and where the product is undergoing aphysical or chemical change, dual- andmulti-wavelength radiometry should beconsidered. The concept of the ratioingradiometer has been around since the early 1950s, but recent design and hardware changes are yieldinghigher performance, low-temperaturecapabilities, and reduced cost.

Dual-wavelength (ratio) thermometryinvolves measuring the spectral energyat two different wavelengths (spectralbands). The target temperature can beread directly from the instrument if theemissivity has the same value at bothwavelengths. This type of instrumentcan also indicate the correct temperatureof a target when the FOV is partiallyoccluded by relatively cold materialssuch as dust, wire screens, and graytranslucent windows in the sight path.

The theory of this design is quite simpleand straightforward, and is illustrated bythe following equations, where we takePlanck’s equation for one wavelengthand ratio it to the energy at a secondwavelength.

If el1 = el2, then T = Tr

where:

R = spectral radiance ratioTr = ratio temperature of the surfaceel= spectral emissivity

In this process, if the emissivity at bothwavelengths is equal (graybody condition),the emissivity factor cancels out of theequation and we find the ratio is directlyproportional to temperature.

1 = 1 + 1n (el1/el2)— — ——————–T Tr 1 1

C2 (– – )l1 - l2

[ l1]-5• e [- C2 (1-1)]

—– — – –R =l2 Tr l1l2

el1 • [ l1]-5 • e [- C2 (1-1)]

—– —– — – –R =el2 l2 T l1 l2

Ll1=el1 • C1 • l1

-5 • e-C2/l1TR =

Ll2 el2 • C1 • l2-5 • e-C2/l2T

T = 1.1 =+++++++t12 + t2

2 ....tn2

Infrared Thermometry Principles Cont’d

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The same concept can be viewed also ina graphic presentation by taking a smallsegment of the blackbody distributioncurve and measuring some ratios atvarious emissivities (see Figure 3).Using 0.7 µm and 0.8 µm as the narrow-band filters, the ratio factor remainsconstant at 1.428 for the range ofemissivities down to 0.1.

Similarly, any other changes that are gray in nature will not affect thetemperature determined by the dual-wavelength thermometer. Thesevariations include changes in target size such as a wire or a stream ofmolten glass whose diameters varyduring measurement, even in the caseof targets smaller than the thermometer’sFOV. For instance, suppose that ablackbody target fills only half thethermometer’s FOV; instead of a 50%reduction in emittance, this analysis isunchanged. Another example is a casewhere a target is obscured with smokeor dust, or where an intervening window(e.g., of a vacuum chamber) becomesclouded. As long as the obscuredmedium is not spectrally selective in its attenuation of radiation, at least inthe wavelength region used by thethermometer, the analysis remains thesame. The temperature inferred by thedual-wavelength radiometer remainsunaffected.

Nonetheless, there are always limitsthat must be recognized. The dual-wavelength does not perform on non-graybodies, e.g., aluminum; it has difficulty looking through non-graywindows or heated Pyrex; and it tends tomeasure background temperatures wherethe background is hotter than the target.

Dual-wavelength thermometers havemany applications throughout industryand research as simple, unique sensorthat can reduce application errorinvolving graybody surfaces. Figure 4illustrates examples of total emissivityfor a variety of products that havetemperature-related varying emissivity.For example, most users would considergraphite to have a high constant emissivity.The fact is, however, that graphite’semissivity varies from 0.4 to 0.65 over the temperature range of ambientto 2000°F. For accurate producttemperature measurement and control,dual-wavelength thermometers shouldbe used when these types of graybodymaterials are being processed at hightemperatures.

There are also multi-wavelengththermometers available for non-graybodymaterials where the emissivity varieswith wavelength. In these applicationsthere is a detailed analysis of the product’ssurface characteristics regarding emissivityvs. wavelength vs. temperature vs.surface chemistry. With these data,algorithms can be generated relatingspectral emittance at various wavelengthsto temperature.

SUMMARYA review of the basic applicationelements is outlined in Figure 5. Thesurface of a target to be measured isthe prime concern. When selecting theinstrument, the user must take intoaccount target size, temperature limits,emissivity, and process dynamics asthey relate to FOV, spectral response,and response time. It is also essential to characterize the surroundings, e.g.,flames, IR heaters, induction coils, andthe atmosphere (dust, dirty windows,flames, excessive heat) in order toselect the optimum instrument for

this application.

With regard to performance specifications,calibration accuracy will typically be inthe 0.5-0.1% range, while the repeatabilityof most sensors will be in the 0.25-0.75%range. Pricing on the basic sensor willstart at $500 and could go as high as$5000-$6000. In the majority of theapplications, price is not an issue; whenthe sensor is properly installed andused, payback typically is on the orderof one or two months.

Reproduced fromSensors Magazine with permission ofHELMERS PUBLISHING, INC. 174 Concord St. Peterborough, NH 03458

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RADIATIONTHERMOMETER

TARGET,TS, el

SURROUNDINGS, Tsur

ATMOSPHEREEMISSION ANDABSORPTION

Figure 5: When selecting noncontacttemperature measurement instruments, it is necessary to take into account not only the target and its emissivity, but also thesurroundings and the invtervening atmosphere.

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Infrared TemperatureMeasurement Theory and Application

Author and Presenter: John Merchant, Sales Manager, Mikron Instrument Company Inc.

ABSTRACTInfrared thermometers for non-contacttemperature measurement are highlydeveloped sensors which havewide-spread application in industrialprocessing and research. This paperdescribes, in non-mathematical terms,the theory upon which the measurementtechnology is based, and how thisis used to deal with the variety ofapplication parameters which confrontthe intending user.

INTRODUCTIONAn infrared thermometer measurestemperature by detecting the infraredenergy emitted by all materials whichare at temperatures above absolutezero, (0°Kelvin). The most basic designconsists of a lens to focus the infrared(IR) energy on to a detector, whichconverts the energy to an electricalsignal that can be displayed in units oftemperature after being compensatedfor ambient temperature variation. Thisconfiguration facilitates temperaturemeasurement from a distance withoutcontact with the object to be measured.As such, the infrared thermometer isuseful for measuring temperature undercircumstances where thermocouples or other probe type sensors cannot beused or do not produce accurate datafor a variety of reasons. Some typicalcircumstances are where the object tobe measured is moving; where theobject is surrounded by an EM field, asin induction heating; where the object is contained in a vacuum or othercontrolled atmosphere; or in applicationswhere a fast response is required.

Designs for an infrared thermometer(IRT), have existed since at least thelate nineteenth century, and variousconcepts by Féry were featured byCharles A. Darling (1) in his book“Pyrometry,” published in 1911.

However it was not until the 1930’s thatthe technology was available to turnthese concepts into practical measuringinstruments. Since that time there has been considerable evolution in the design and a large amount ofmeasurement and application expertisehas accrued. At the present time, thetechnique is well accepted and is widelyused in industry and in research.

MEASUREMENT PRINCIPLESAs previously stated IR energy is emittedby all materials above 0°K. Infraredradiation is part of the ElectromagneticSpectrum and occupies frequenciesbetween visible light and radio waves.The IR part of the spectrum spanswavelengths from 0.7 micrometers to1000 micrometers (microns). Figure 1.Within this wave band, only frequenciesof 0.7 microns to 20 microns are usedfor practical, everyday temperaturemeasurement. This is because the IRdetectors currently available to industryare not sensitive enough to detect thevery small amounts of energy availableat wavelengths beyond 20 microns.

Though IR radiation is not visible to thehuman eye, it is helpful to imagine it asbeing visible when dealing with theprinciples of measurement and whenconsidering applications, because inmany respects it behaves in the sameway as visible light. IR energy travels instraight lines from the source and canbe reflected and absorbed by materialsurfaces in its path. In the case of mostsolid objects which are opaque to thehuman eye, part of the IR energystriking the object’s surface will beabsorbed and part will be reflected. Ofthe energy absorbed by the object, aproportion will be re-emitted and partwill be reflected internally. This will alsoapply to materials which are transparentto the eye, such as glass, gases andthin, clear plastics, but in addition, someof the IR energy will also pass throughthe object. The foregoing is illustrated inFigure 2. These phenomena collectivelycontribute to what is referred to as theEmissivity of the object or material.

Materials which do not reflect ortransmit any IR energy are know asBlackbodies and are not known to existnaturally. However, for the purpose oftheoretical calculation, a true blackbodyis given a value of 1.0. The closestapproximation to a blackbody emissivityof 1.0, which can be achieved in real lifeis an IR opaque, spherical cavity with asmall tubular entry as shown in Figure 3.The inner surface of such a sphere willhave an emissivity of 0.998.

Different kinds of materials and gaseshave different emissivities, and willtherefore emit IR at different intensitiesfor a given temperature. The emissivityof a material or gas is a function of its molecular structure and surfacecharacteristics. It is not generally afunction of color unless the source of

Wavelength (meters)

Infrared spectrum 0.7 to 1000 micrometers (microns)ELECTROMAGNETIC SPECTRUM

10–12 10–10 10–8 10–6

gam

ma rays

x-ray

ultravio

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visible

infrared

radio

10–4 10–2 1 102 104

Figure 1

emission absorption reflection transmission

emitted

incident

hot coldreflected

RADIATIVE HEAT EXCHANGE

Figure 2

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the color is a radically different substanceto the main body of material. A practicalexample of this is metallic paints whichincorporate significant amounts ofaluminum. Most paints have the sameemissivity irrespective of color, butaluminum has a very different emissivitywhich will therefore modify the emissivityof metallized paints.

Just as is the case with visible light, the more highly polished some surfacesare, the more IR energy the surface willreflect. The surface characteristics of amaterial will therefore also influence itsemissivity. In temperature measurementthis is most significant in the case ofinfrared opaque materials which havean inherently low emissivity. Thus ahighly polished piece of stainless steelwill have a much lower emissivity thanthe same piece with a rough, machinedsurface. This is because the groovescreated by the machining prevent asmuch of the IR energy from beingreflected. In addition to molecularstructure and surface condition, a thirdfactor affecting the apparent emissivityof a material or gas is the wavelengthsensitivity of the sensor, known as thesensor’s spectral response. As statedearlier, only IR wavelengths between0.7 microns and 20 microns are used for practical temperature measurement.Within this overall band, individualsensors may operate in only a narrowpart of the band, such as 0.78 to 1.06,or 4.8 to 5.2 microns, for reasons whichwill be explained later.

THEORETICAL BASIS FOR IRTEMPERATURE MEASUREMENTThe formulas upon which infraredtemperature measurement is based areold, established and well proven. It isunlikely that most IRT users will need to make use of the formulas, but aknowledge of them will provide anappreciation of the interdependency of certain variables, and serve to clarifythe foregoing text. The importantformulas are as follows:

1. Kirchoff’s LawWhen an object is at thermalequilibrium, the amount of absorptionwill equal the amount of emission.

a = e

2. Stephan Boltzmann LawThe hotter an object becomes themore infrared energy it emits.

W = eoT4

3. Wien’s Displacement LawThe wavelength at which themaximum amount of energy isemitted becomes shorter as thetemperature increases.

lmax = 2.89 x 103mmK/T

4. Planck’s EquationDescribes the relationship betweenspectral emissivity, temperature andradiant energy.

C2Wl = C1el[l5(elT-1)]-1

INFRARED THERMOMETERDESIGN AND CONSTRUCTIONA basic infrared thermometer (IRT)design, comprises a lens to collect theenergy emitted by the target; a detectorto convert the energy to an electricalsignal; an emissivity adjustment tomatch the IRT calibration to the emittingcharacteristics of the object beingmeasured; and an ambient temperaturecompensation circuit to ensure thattemperature variations within the IRT,due to ambient changes, are nottransferred to the final output. For manyyears, the majority of commerciallyavailable IRT’s followed this concept.They were extremely limited inapplication, and in retrospect did not measure satisfactorily in most

circumstances, though they were verydurable and were adequate for thestandards of the time. Such a concept is illustrated in Figure 4.

The modern IRT is founded on thisconcept, but is more technologicallysophisticated to widen the scope of itsapplication. The major differences arefound in the use of a greater variety ofdetectors; selective filtering of the IRsignal; linearization and amplification of the detector output; and provision of standard, final outputs such as 4-20mA, 0-10Vdc, etc. Figure 5 shows a schematic representation of a typicalcontemporary IRT.

Probably the most important advance in infrared thermometry has been theintroduction of selective filtering of theincoming IR signal, which has beenmade possible by the availability ofmore sensitive detectors and morestable signal amplifiers. Whereas theearly IRT’s required a broad spectralband of IR to obtain a workable detectoroutput, modern IRT’s routinely havespectral responses of only 1 micron.The need to have selected and narrowspectral responses arises because it isoften necessary to either see throughsome form of atmospheric or otherinterference in the sight path, or in factto obtain a measurement of a gas orother substance which is transparent toa broad band of IR energy.

Some common examples of selectivespectral responses are 8-14 microns,which avoids interference fromatmospheric moisture over long pathmeasurements; 7.9 microns which isused for the measurement of some thinfilm plastics; and 3.86 microns whichavoids interference from CO2 and H2O

theoretical blackbody practical blackbody

EMISSIVITY

0

1

1

Figure 3

INFRARED TEMPERATURE MEASUREMENT

A.T.C.E

DET

Figure 4

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vapor in flames and combustion gases.The choice between a shorter, or longerwavelength spectral response is alsodictated by the temperature rangebecause, as Planck’s Equation shows,

the peak energy shifts towards shorterwavelengths as the temperatureincreases. The graph in Figure 6illustrates this phenomenon. Applicationswhich do not demand selective filtering

for the above stated reasons may oftenbenefit from a narrow spectral responseas close to 0.7 microns as possible.This is because the effective emissivityof a material is highest at shorterwavelengths and the accuracy ofsensors with narrow spectral responsesis less affected by changes in targetsurface emissivity.

It will be apparent from the foregoinginformation that emissivity is a veryimportant factor in infrared temperaturemeasurement. Unless the emissivity ofthe material being measured is known,and incorporated into the measurement,it is unlikely that accurate data will beobtained. There are two methods forobtaining the emissivity of a material: a) by referring to published tables andb) by comparing the IRT measurementwith a simultaneous measurementobtained by a thermocouple or resistancethermometer and adjusting the emissivitysetting until the IRT reads the same.Fortunately, the published data availablefrom the IRT manufacturers and someresearch organizations is extensive, so it is seldom necessary to experiment.As a rule of thumb, most opaque, non-metallic materials have a high and stable emissivity in the 0.85 to 9.0range; and most un-oxidized, metallicmaterials have a low to mediumemissivity from 0.2 to 0.5, with theexception of gold, silver and aluminumwhich have emissivities in the order of0.02 to 0.04 and are, as a result, verydifficult to measure with an IRT.

While it is almost always possible toestablish the emissivity of the basicmaterial being measured, a complicationarises in the case of materials which haveemissivities that change with temperaturesuch as most metals, and other materialssuch as silicon and high purity, singlecrystal ceramics. Some applicationswhich exhibit this phenomena can besolved using the two color, ratio method.

TWO COLOR-RATIOTHERMOMETRYGiven that emissivity plays such a vitalrole in obtaining accurate temperaturedata from infrared thermometers, it is not surprising that attempts havebeen made to design sensors whichwould measure independently of thisvariable. The best known and mostcommonly applied of these designs is the Two Color-Ratio Thermometer.This technique is not dissimilar to theinfrared thermometers described so far,but measures the ratio of infraredenergy emitted from the material at twowavelengths, rather than the absoluteenergy at one wavelength or waveband. The use of the word “color” in this

lens chopper

led opticalinterrupter

filter

thermistora.t.c. amp

signal ampprw. amp prw. amp

signal ground

power supply±12 vdc

±15 vdcphase control

d.c. motor

MODERN INFRARED THERMOMETER

motorcontrol

Figure 5

Infrared Temperature Cont’d

2 4 6 8 10 12 14 16 18Wavelength (microns)

Blackbody Spectral Distribution Curves

900°K

800°K

700°K

600°K

500°K

Spe

ctra

l rad

iant

em

ittan

ce (

W c

m–2

m–1

)

1

0.75

0.50

0.25

0

Figure 6

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context is somewhat outdated, butnevertheless has not been superseded.It originates in the old practice ofrelating visible color to temperature,hence “color temperature.”

The basis for the effectiveness of two-color thermometry is that any changesin either the emitting property of thematerial surface being measured, or inthe sight path between the sensor andthe material, will be “seen” identically bythe two detectors, and thus the ratio andtherefore the sensor output will notchange as a result. Figure 7 shows aschematic representation of a simplifiedtwo-color thermometer.

Because the ratio method will, underprescribed circumstances, avoidinaccuracies resulting from changing orunknown emissivity, obscuration in thesight path and the measurement ofobjects which do not fill the field of view,it is very useful for solving some difficultapplication problems. Among these arethe rapid induction heating of metals,cement kiln burning zone temperatureand measurements through windowswhich become progressively obscured,such as vacuum melting of metals. Itshould be noted however, that thesedynamic changes must be “seen”identically by the sensor at the twowavelengths used for the ratio, and thisis not always the case. The emissivity

of all materials does not change equallyat two different wavelengths. Thosematerials that do are called “Greybodies.”The ones that do not are called “Non-Greybodies.”

Not all forms of sight path obscurationattenuate the ratio wavelengths equallyeither. The predominance of particulatesin the sight path which are the samemicron size as one of the wavelengthsbeing used will obviously unbalance theratio. Phenomena which are non-dynamicin nature, such as the “non-greybodyness”of a material, can be dealt with bybiassing the ratio, an adjustmentreferred to as “Slope.” However, theappropriate slope setting must generallybe arrived at experimentally. Despitethese limitations, the ratio method workswell in a number of well establishedapplications, and in others is the best, if not the most preferred solution.

SUMMARYInfrared thermometry is a mature butdynamic technology that has gained the respect of many industries andinstitutions. It is an indispensabletechnique for many temperaturemeasurement applications, and thepreferred method for some others.When the technology is adequatelyunderstood by the user, and all therelevant application parameters areproperly considered, a successful

application will usually result, providingthe equipment is carefully installed.Careful installation means ensuring that the sensor is operated within itsspecified environmental limits, and that adequate measures are taken tokeep the optics clean and free fromobstructions. A factor in the selectionprocess, when choosing a manufacturer,should be the availability of protectiveand installation accessories, and alsothe extent to which these accessoriesallow rapid removal and replacement of the sensor for maintenance. If theseguidelines are followed, the moderninfrared thermometer will operate more reliably than thermocouples orresistance thermometers in many cases.

REFERENCES1. Darling, Charles R. ; “Pyrometry. APractical Treatise on the Measurementof High Temperatures.” Published byE.&F.N. Spon Ltd. London. 1911.

Reproduced with permission of the author, John Merchant, Sales Manager, MIKRONINSTRUMENT COMPANY, INC.

ratio

Dl1

Dl2

O/P

beamsplitter

colimator

target

TWO COLOR THERMOMETRY(ratio thermometry)

Figure 7

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Noncontact TemperatureMeasurement Theory and Application

Walter Glockmann, CapintecInstruments, Inc.

Noncontact temperature measurementis the preferred technique for small,moving, or inaccessible objects;dynamic processes that require fastresponse; and temperatures <1000°C(1832°F). To select the best noncontacttemperature measurement device for aparticular application, it is essential tounderstand the basics of temperaturemeasurement technology, temperaturemeasurement parameters, and the featuresoffered by the various measurementsystems currently available.

DEFINING THE TERMSTemperature. Temperature is oneexpression for the kinetic energy of the vibrating atoms and molecules ofmatter. This energy can be measuredby various secondary phenomena, e.g.,change of volume or pressure, electricalresistance, electromagnetic force,electron surface charge, or emission ofelectromagnetic radiation. The mostfrequently used temperature scales areCelsius and Fahrenheit, which dividethe difference between the freezing and boiling points of water into 100°and 180°, respectively.

The thermodynamic scale begins atabsolute zero, or 0 Kelvin, the point atwhich all atoms cease vibrating and no kinetic energy is dissipated.

0 K = –273.15°C = –459.67°F

IR Radiation. Infrared is that portion ofthe electromagnetic spectrum beyondthe visible (blue to red, 0.4-0.75 µm)response of the human eye. IRwavelengths extend from 0.75 µm to 1000 µm, where the shortestmicrowaves (radar) begin. Because IR radiation is predominantly generatedby heat, it is called thermal radiation.

For the purpose of radiation thermometry,only portions of the IR spectrum areimportant. The spectrum is frequentlydivided into “atmospheric windows” thatprovide maximum loss-free transmissionthrough water vapor in air:0.7-1.3 µm; 1.4-1.8 µm; 2.0-2.5 µm;3.2-4.3 µm; 4.8-5.3 µm; 8-14 µm

Thermometer. Most of the well-knownthermometers, e.g., glass bulb mercuryor alcohol, thermocouple, or resistancethermometer, must be placed in directcontact with the temperature source.Their useful measurement range is–100°C to 1500°C.

Radiation Thermometer. This noncontactthermometer determines the surface

temperature of an object by interceptingand measuring the thermal radiation itemits.

Emissivity. This quality defines thefraction of radiation emitted by an objectas compared to that emitted by a perfectradiator (blackbody) at the sametemperature. Emissivity is determined in part by the type of material and itssurface condition, and may vary fromclose to zero (for a highly reflectivemirror) to almost 1 (for a blackbodysimulator). Emissivity is used tocalculate the true temperature of anobject from the measured brightness or spectral radiance. Because anobject’s emissivity may also vary withwavelength, a radiation thermometerwith spectral response matching regionsof high emissivity should be selected for

a specific application. Emissivity valuesare listed in the literature for a variety ofmaterials and spectral bands, or thesevalues can be determined empirically.

Brightness/Single-Color Pyrometer.These devices measure and evaluatethe intensity, or brightness, of theintercepted thermal radiation. Intensity,or, more generally, spectral radiance, ismeasured in a narrow wavelength bandof the thermal spectrum. Band selectionis dictated by the temperature range andthe type of material to be measured.

The oldest brightness pyrometerscompared optical brightness in thevisible (red) spectrum at 0.65 µm bymatching the glowing object to a hot“disappearing” filament. The term“single-color” derives from the single

Table 1: On-Line Temperature Measurement Instruments

LOW TEMPERATURE

General Purpose0 to 500°C (30 to 1000°F)8-14 mm wide band radiation thermometers

• thermopile detector• optical resolution: 4 mm target

(15:1 D-ratio)• response time: 0.5 sec• emissivity adjustment• analog output (mv/°C, mV/°F)

Extended Temperature Ranges– 30°C to 800°C (–20°F to 1500°F)high-stability, 8-14 µm thermometers

• pyroelectric detector• chopper stabilized to compensate for

rapid changes in ambient temperature• optical resolution: 3 mm dia. (30:1 D-ratio)• response time: 50 msec• analog output 4-20 mA

High-Precision/Complex Applications50°C to 800°C (–60°F to 1500°F)narrow spectral band radiation thermometers

• for thin plastic films with CH absorptionbands (3.4 µm; 6.8 µm)

• for polyester/fluorocarbon films (8.0 µm)• for thin glass and ceramics (7.8 µm)• optical resolution: 1.5 mm dia.

(100:1 D-ratio)

Programmable/High-Performance–100°C to 2500°C (–150°F to 4500°F) with built-in signal conditioning and digitalcomputing, spectral band choices in wide or narrow bands between 2 µm and 20 µm

• digital RS 232 bidirectional interface• max./min./differential/hold functions• programmable ambient temperatures• choice of through-lens-sighting, LED,

or laser

HIGH TEMPERATURE

General Purpose400 to 2000°C (750 to 3600°F)narrow spectral band radiationthermometers (0.7-1.1 µm; 0.9-1.9 µm)

• solid-state photoelectric detectors (Si, Ge)• optical resolution 1 mm target

(60:1 D-ratio)• response time 3 msec• emissivity adjustment• analog output (mV°C, mV/°F)

High-Stability/Complex Applications300 to 2500°C (600 to 4500°F)narrow spectral band radiation thermometers

• for glass and/or through hot gas (3.9 µm)• for glass surfaces (5.0 µm)• for combustion gases (4.2, 4.5, 5.3 µm)• pyroelectric detector• chopper stabilized• optical resolution: 1 mm target

(100:1 D-ratio)• response time: 30 msec• analog output 4-20 mA

High-Speed, Two-Color Ratio150 to 2500°C (300 to 4500°F) narrowspectral bands (0.8/0.9 µm; 2.1/2.4 µm)

• greatly independent of emissivityfluctuations and/or sight pathdisturbances

• automatic compensation for moving targets• internal calibration check

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narrow wavelength band of red seen by the user. Instruments sensitized tomeasure in the IR region are also calledspectral radiation pyrometers or spectralradiation thermometers.

Ratio/Two-Color Pyrometer. Thisradiation thermometer measurestemperatures on the basis of two (or more) discrete wavelengths. Theratio of the brightnesses in separatewavelengths corresponds to color in the visible spectrum. The use of twodistinct, visible colors – typically red andgreen – has long been popular to infercolor temperatures. More recently, the term has broadened from its initial usage to include wavelengths in the infrared. The advantage of ratiomeasuring is that temperature readingsare greatly independent of emissivityfluctuations and/or sight path obscurations.The technique is generally used fortemperatures above incandescence(700°C,1300°F ), but measurements downto 200°C (400°F) are also possible.

MEASUREMENT PARAMETERSAdvanced optical and electronic signalprocessing modules greatly extend theaccuracy and performance capabilitiesof noncontact temperature measuring.For process control, standardizedinterfaces are available that provideconditioned signal outputs optimized for specific applications.

RADIATION DETECTIONEmissivity Adjustment. Temperaturereading accuracy depends on thecorrect adjustment of the instrument tothe target emissivity. Preset emissivityvalues can be used for on-line sensorsto monitor targets of constant emissivity.Measurements on those materials withchanging emissivities require anaccurate and reproducible emissivityadjustment.

Surrounding Area Temperature.Thermal target radiation alwayscontains stray radiation emitted by theenvironment surrounding the target areaand reflected by the target’s surface. Inpractice, the ambient temperature isfrequently presumed to be the same asthe temperature of the sensor. If thetarget is exposed to a different thermalenvironment, e.g., inside a heatedfurnace, inside a cooled chamber, oroutdoors facing the open sky, adjustmentsare necessary for accurate measurement.Separate sensors for the area surroundingthe target may be used for automatictemperature calculation.

Sight Path Obscuration. Gases, watervapor, dust, and other aerosols in thesight path of a sensor may affect thetemperature reading. Using one of the“atmospheric windows” in the IR regiongreatly reduces measurement errors.Since both optical channels are equally

attenuated, ratio pyrometers are generallyimmune to sight path obscuration, andthe signal color ratio remains unaffected.

Ambient Temperature Drift. By thenature of their design, radiationdetectors are strongly affected byambient temperature changes. Tomaintain high measurement accuracy,precise compensation of this temperaturedrift is required. Temperature drift isspecified in error/°C or error/°F ofambient temperature change.

OPTICAL SYSTEMSOptics. Reflective (mirror) andrefractive (lens) optics are used innoncontact temperature sensors toisolate and define radiation from themeasured target.

Field of View. The field of view (FOV) is expressed in degrees solid angle or in radians. The FOV allows easycalculation of the minimum target sizefor each working distance. A convenientmeasure is the distance-to-target ratio,e.g., 20:1, indicating a minimum targetof 1 in. at a 20 in. measuring distance.

Focusing on Target. Optics innoncontact temperature sensors are generally of the fixed-focus type.Focusing at longer measuring distancesis not required if the target area issmaller than the entrance aperture (lens diameter) of the instrument.

Small Targets. For miniature objects,fixed-focus close-up optics are used,and the minimum target size is

specified. Targets as small as 0.5 mmcan be isolated.

Fiber Optics. Fiber optics permits a physical separation of the lensassembly from the detector and signalprocessing electronics in restrictedspaces or hostile environments. Theuseful measuring range of fiber opticsstarts at 400°C (750°F). Minimum targetareas are as defined above.

Target Scanning. Reflective surfacemirrors are used to change the viewingangle of the measuring sensor if directviewing is difficult or impractical. Anoscillating mirror can be employed todeflect the intercepted radiation and toscan a predetermined temperatureprofile across a target area.

A sequence of scanned temperatureprofiles taken at preset spatial intervalsover the target can be displayed as athermal image or in the form of athermal map.

Aiming on Target. A variety of opticalaiming techniques are used withnoncontact temperature sensors:• Simple bead-and-groove gun sights• Integrated or detachable optical view

finders• Through-the-lens sighting• Integrated or detachable light beam

markers

SIGNAL PROCESSINGDirect Output. Noncontact temperaturesensors convert the intercepted thermalradiation into an electrical signal

Table 2: On-Line Temperature Measurement Instruments

General Purpose0 to 500°C (30 to 1000°F) 8-14 µm wide band

• thermopile detector• optical resolution: 4 mm dia.

(15:1 D-ratio)• emissivity adjustment• max./min. value

High Stability– 30 to 800°C (–30 to 1500°F) 8-14 µm

• pyroelectric detector• chopper stabilized• choice of optics

Extended Temperature Ranges–50 to 1400°C (–60 to 2550°F) 8-14µm with built-in signal conditioning

• optical resolution: 32 mm target (30:1 D-ratio)

• data collection• peak/valley/averaging functions• digital RS-232 output

Miniature Probe–50 to 500°C (–60 to 1000°F) 8-14 µm

with interchangeable probes for longdistance or small target applications

• large LCD information display• max./min./differential/hold signal

conditioning• optical resolution: 2.5 mm dia.

(7:1 D-ratio)• LED or laser aided target aiming

LOW TEMPERATURE

General Purpose250 to 2500°C (500 to 4500°F)narrow spectral band radiation thermometers(0.65 µm; 0.7-1.1 µm; 0.9-1.9 µm)

• solid-state photoelectric detectors (Si, Ge)• optical resolution 0.9 mm dia. (250:1

D-ratio)

High-Precision, Two-Color RatioPyrometer650 to 2500°C (1200 to 4500°F) spectralbands 0.8/0.9 µm

• greatly independent of emissivityfluctuations and/or sight pathdisturbances

• automatic compensation for movingtargets

HIGH TEMPERATURE

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proportional to the spectral radianceemitted from the target surface.

Linearized Output. An electronicnetwork converts the thermal radiancesignal into an electrical current/voltageproportional to temperature.

Sample and Hold. The momentarytemperature reading, selected by anexternal trigger is held (frozen) untilreplaced by a new value in the nextsampling cycle.

Maximum Value or Peak Hold. Thehighest temperature reading over thespecific measuring period is displayed.Reset is triggered by an external signal.

Minimum Value or Valley Hold. Thelowest temperature reading during aspecific measurement period isdisplayed. Rest is triggered by anexternal signal.

Peak to Peak. The difference betweenthe maximum and the minimumtemperature readings during a specificmeasurement period is displayed.

Speed of Response. Short responsetime is needed to follow rapidly changingdynamic temperature processes. Longresponse time integrates all signalvariations during a specific measurementperiod and enhances temperatureresolution in order to average changingvalues or to improve measurementprecision.

Automatic Trigger (Wave Function).The highest temperature reading isdetected and displayed. Reset istriggered automatically when the signalreaches an adjustable threshold, but thelast peak value is held on display until itis replaced by the following peak value.This technique is appropriate for rapidsampling and analysis of intermittenttarget values, without the use ofexternal trigger signals.

Alarms. An output signal (relay) isactivated when the signal reaches apreset temperature value. Twoindependent set points – HI/LO – aregenerally provided.

ACCESSORIESWater Coolable Jackets. Water cooling extends the sensor’s ambienttemperature range up to 400°C (752°F)or beyond.

Air Purge Fittings. Lens barrels orattachments with fittings for compressedair are designed to direct a clean airflow across the lens surface. They keepthe optical sight paths free of vapors,fumes, and dust.

BLACKBODY CALIBRATORSDeep cavities controlled at ahomogeneously distributed temperatureserve as blackbody simulators for thecalibration of radiation thermometers.To accommodate the variety ofinstruments, they provide an effectiveaperture of ~ 1 in. (25 mm) and are

Table 3: Temperature Measurement in Process Control

SUCCESSFUL APPLICATIONS ON-LINE PORTABLES

R H L R H L

Cement kilnburning zones, preheaters X X X X

Energy conservationinsulation and heat flow studies, thermal mapping X X

Filamentsannealing, drawing, heat treating X X

Foodbaking, candy-chocolate processing, canning, freezing, X Xfrying, mixing, packing, roasting

Furnacesflames, boiler tubes, catalytic crackers X X X X

Glassdrawing, manufacturing/processing bulbs, containers, X X X X X XTV tubes, fibers

Maintenanceappliances, bearings, current overloads, driving shafts, X Xinsulation, power lines, thermal leakage detection

Metals (ferrous and nonferrous)annealing, billet extrusion, brazing, carbonizing, casting, X X X Xforging, heat treating, inductive heating, rolling/strip mills,sintering, smelting

Quality controlprinted circuit boards, soldering, universal joints, welding, X X X X X Xmetrology

Paintcuring, drying X

Papercoating, ink drying, printing X Xphotographic emulsions, web profiles

Plasticblow-molding, RIM, film extrusion, X Xsheet thermoforming, casting

Remote sensing (thermal mapping)clouds, earth surfaces, lakes, rivers, roads, volcanic surveys X X X

Rubbercalendering, casting, molding, profile extrusion X Xtires, latex gloves

Siliconcrystal growing, strand/fiber, wafer annealing, X X X X

epitaxial deposition

Textilecuring, drying, fibers, spinning X X

Vacuum chambersrefining, processing, deposition X X

R=Ratio/Two-Color H=High-Temperature L=Low Temperature

optimized for their operatingtemperature range:• Stirred water bath: 30-100°C

(86-212°F)• Aluminum core: 50-400°C (122-752°F)• Stainless steel core: 350-1000°C

(662-1832°F )• Portable, battery operated field

calibrator: fixed temperature choicesfrom 40°C-100°C (104-212°F)

ON-LINE OR PORTABLE?On-Line Instruments. These devicesare generally used for continuousprocess monitoring and control. Theyare available in low- and high-temperature models, each with its own operating specs (see Table 1).

Portable Instruments. Portables aretypically favored for process checks,preventive/predictive maintenance,thermal surveys, R&D, and temporarytemperature monitoring. The low- andhigh-temperature versions differ inperformance, as shown in Table 2.

APPLICATIONSSuccessful applications of both on-lineand portable noncontact temperaturemeasurement instruments aresummarized in Table 3.

Reproduced with permission ofCapintec, Inc.

Noncontact Temperature Measurement Cont’d

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Fiber OpticsA New Approach to Monitor and ControlProcess Temperature

The coupling of optical fibers to infrareddetectors and signal processingelectronics represents the latestprogress in the field of non-contacttemperature measurement and control.

Only recently have fiber optics becomethe object of widespread interest thanksmainly to their ability to carry opticalinformation signals over long distancesand around unavoidable obstructions.

For years infrared detectors have beenused in conjunction with conventionaloptical elements (lenses, mirrors,prisms). Fiber optics were excludedfrom consideration since they are madeof either glass or plastics, both of whichare opaque throughout most of theinfrared spectral region. Thus, accordingto fundamental laws of physics, theirmarriage to infrared detectors couldnever work.

Months of painstaking developmentproved the reality and practicality oftransmitting IR with fiber optics. Andthus it happened that coupling fiberoptics with infrared detectors resulted inseveral new families of instrumentationand control systems endowed withsuperior performance characteristics.

Since most if not all of you are currentlyfamiliar with the theory of infraredradiation and the variety of methods for monitoring IR this discussion willdeal mainly with the application of fiberoptics in conjunction with IR detectors,i.e. their construction, advantages,disadvantages and applications.

A typical optical fiber is usuallyconstructed of a silicon (glass) material,however, plastic and quartz are also available but normally for datatransmission. Today most of all opticalfibers manufactured consist of a light-conducting glass core surrounded by athin layer of glass cladding with a lower refractive index. This claddingserves to protect the core finish.

All fibers used in infrared instrumentationare made of glasses especially chosenfor their ability to transmit the radiationcomprised in the chosen spectral region.

All rays entering the front surface thatacquire an inclination smaller than thecritical angle are totally reflected insidethe fiber core, and keep propagating inthis fashion until they reach the oppositeend or are totally absorbed, whichevercomes first. For a fiber having a criticalangle of X° means that all rays incidentonto the fiber's front surface at the sameangle or less with its axis are trappedinside the fiber by total internal reflection.

On the other hand, all incident raysentering the fiber with an inclinationlarger than the same angle will leave the first contact with its internal surface.This behavior is commonly called“spilling” (See Figure 1).

The value of the critical angle is a functionof the ratio between the refractive indexesof the glass of which the core is madeand of the medium surrounding it. Bycontrolling the ratio we can increase or decrease the acceptance angle offiber optics, thus obtaining specialperformance characteristics.

For most IR monitoring applications,optical fibers are assembled into fiberbundles consisting of many hundreds of individual fibers contained within a flexible or rigid sheathing of eithermetallic or nonmetallic material. Eachend of the bundle is held in place usinga high temperature epoxy. The endsurface is then highly polished to assurea clearly defined angle of acceptanceand diminish reflectance losses due toirregular surfaces. Using such a largenumber of narrow fibers in a bundleallows us to gather and transmit moresignal to the detector while retainingmechanical flexibility. Typically, theoutside diameter of a single fiber is 25m.

Generally speaking, in the majority of applications where optical fibers are used with infrared radiometers, the lengths are 1 or 2 meters long. On occasion fibers will be made up to approximately 10 meters in length. The determining factors in using fiberbundles to transmit IR, are MMT(minimum measurable temperature),target distance and spot size. Thehigher the temperature the longer the fiber, conversely low temperaturesrequire a shorter fiber due to the glassattenuation.

Unfocused fibers (those without aviewing lens) have a field of view or angleof acceptance of 60°. This is the targetarea viewed by the detector which isslightly larger than the distance betweenthe front end of the fiber and the targetsurface. This can be easily verified bybacklighting the target with visible lightwhich will project onto the target surface.Unfocused fibers are used when thetarget area is large and it is desirable tomeasure its average temperature.

Focused fibers (those with a viewinglens assembly attached to the front end)are used to measure targets as small as.01 cm from as far away as 4.5 metersor further. The determining factor aswith fiber length is the amount of energybeing collected. By backlighting we can be assured the lens is properlyfocused and aligned on the target. Insome applications, where vibration orother type movement may alter thelens's alignment, a bifurcated fiber ispreferable. One branch of the fiber is connected to a high intensity lightsource and activated by a momentary-on switch which will verify to the operatorthe correct alignment of the fiber. Theother branch will allow the infrareddetector to “see” the target at exactlythe same spot that was illuminated.

A A

AB

AB

Opaque coating

S "spilled" ray

23°35°

Light ray

Acceptanceangle(72°)

Cladding

67°

Figure 1

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FIBER ASSEMBLY VARIETIESThe wide selection of fibers and lensconfigurations available allows for asatisfying and endless number ofapplications.

Following are some of the manycomponents that make up a fiber opticsystem and allow for such versatility.

Sheathing– Single, bifurcated or trifurcated fiber

optic systems– Flexible stainless steel (standard)– Heavy duty S.S. wire braid– Heavy duty braided fiber Imperial

Eastman– Teflon (for use in high RF fields)– Protective tubingLenses– 1.27 cm, 1.90 cm, 2.54 cm x 8.59 cm

to 27.7 cm max.– Natural - black anodized aluminum– Angular lens configurations availableReplaceable Tips– Glass or quartz, 7.62 cm, 15.24 cm &

22.86 cm long– Ceramic or stainless steel jacketOptical Rods– Glass, 15.24 cm, 30.48 cm &

60.96 cm long– Ceramic or stainless steel jacketSpecials– Right angle prisms, high speed

scanners, angled bundle configurations

APPLICATIONSSince virtually every manufacturedproduct – from automobiles to the safetypin – requires the application of heattreatment in some form, the use for non-contact temperature monitoring andcontrol is virtually limitless.

INDUCTION HEATINGBecause of the strong RF inductiveenergy field needed to heat the metalparts being treated, conventionalmeasuring devices are of little valuesince they will be heated directly by the induction coil.

Figures 2 and 3 show typical applicationsof fiber optic systems used to monitorand control induction treatment of metalobjects either stationary in, or movingthrough induction furnaces.

Precise control of the temperatureneeded for perfect heat treatment ofmetal parts is essential to produce the crystal structure that will ensuremeeting or exceeding the mechanicalcharacteristic specifications.

This control function is achieved eitherby on/off or high speed proportionalcontrol incorporated in the fiber optic

and Thermal Monitoring System.

Using fiber optics vs. the conventionaldirect line of sight infrared detectionsystems allows placing the viewing endof the fiber optic in close proximity of thetarget. The tip of the fiber in many casesmay be positioned between the inductioncoils to view the processed material. Toeliminate the adverse effects of the RFfield a ceramic replaceable tip is utilized.In those instances where the designof the system won't allow room for the fibers, a lens system will then beprovided to view and monitor targetsfrom a distance.

The fiber and electronics normally arenot affected by induction energy fields,however, in unusual circumstanceswhen the electrical noise environment is excessively high, a synchronousdemodulation system is specified. The sync. demod, converts the 400 HzAC signal from the detector head to DC. This conversion differs fromconventional AC to DC converters inthat it selects only the signal componentat 400 Hz and discriminates againstnoise components of other frequencies.

CONTINUOUS CASTINGThese operations utilize fiber optic

assemblies up to thirty feet in length that are installed between the rollersthemselves to within one or two inchesof the slab surface. A remotely locatedautomatic multiplexing chassis monitorsseveral points on a time shared basis,achieving significant savings in terms of cost and space. Due to the shieldedpath of constant transmissivity providedby the optical fibers and the short wavelength 0.8 to 1 silicon detector, the system“watches” the target through smoke,fumes, vapors and water. (See Figure 4.)

Quite often in this type of applicationthe fibers are exposed to substantiallyelevated temperatures and mechanicalabuse necessitating the need for airpurging and special heavy duty protectivesheathing. The purge tube is designedto allow the air flow to exit the front end of the fibers at a right angle thuspreventing the build up of contaminants.

METAL FORGING, HOT STAMPING,PIPE BENDINGForging of metal parts includes bothrough shape as well as precision forging,which requires less material removaland waste. Pipe bending and shaping isalso included in this application. Theseoperations are carried out by heatingthe parts to be worked upon to theoptimum temperature with any of the several means available (ovens, flame, induction field, etc.) If the parttemperature is below the optimum,cracks and internal tensions will develop,while if it is above the optimum, droopingwill take place. The precise temperaturecontrol afforded by the use of infraredfiber optic controllers will:– Avoid the formation of defective

parts (from cracks or drooping), thuseliminating rejects and waste due tothese defects;

– Save thermal energy by ensuring thatno heat is wasted by heating the parts

Figure 2: Monitoring steel rod continuesinduction heating.

Figure 3: Controlling induction treating ofautomotive crankshafts.

Figure 4: Five-channel multiplexing, signal-processing and display system.

Fiber Optics Cont'd

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beyond the optimum level;– Speed up production by allowing a

faster rate of heating the parts withoutdanger of temperature overshoot.

METAL DIE CASTINGThe die temperature is of criticalimportance in die casting of metals.Thermal cycling of aluminum products,with reference to die temperature hasbeen successfully implemented with thehelp of optical fibers. Figure 5 showsschematically and in detail how the frontend of the fiber is inserted through themold frame and held in a corner of therunner plate, in contact with the aluminumflowing through it.

The major advantages offered by thissolution are:– Substantial savings of thermal energy,

by eliminating overheating anddrastically reducing production rejects.

– Increased production due to thespeedup of the casting cycle. Theoperation is automatically controlledby the temperature of the castingmaterial and not solely by time,resulting in faster operation.

– Improvement in the quality of thecasting due to the control of theprocess as a function of temperature,results in simpler operation andautomatic compensation for a cold die start-up or interrupted cycles.

Direct indication of the die and furnacepot temperature of the metal. Lowlevel and blocked water lines areeasily indicated several shots beforethe casting can display conditionsvisibly.

CONTROL OF METAL-WORKING LASERLasers, generally high-power CO2 lasers,are used for welding, surface treating andfinishing metals of various types. Theconventional approach is to periodicallysample the beam to keep its power atthe desired level. This approach, however,cannot automatically take into account

the emissivity variations of the targetsurface. These variations, in turn, affectthe amount of laser power absorbed bythe target, and consequently the target'stemperature, which is of paramountimportance for good operatingperformance.

This difficulty is overcome by the use ofan emissivity-independent infrared fiber

optics system (EITM) aimed at the spotof laser beam impact. (See Figure 6.)The infrared system is made blind to the laser wavelength, and in this way itmeasures precisely the target temperatureat the same spot and, via a feedbackloop, it controls the laser power toensure that the operation is carried outat the optimum temperature.

Among the advantages offered by thefiber optics infrared approach are thefollowing:

Figure 5

Figure 6

LensAssembly

Cutting Oxygen Preheating Gas

Cutting NozzleCutting Direction

Pre-heating FlameCutting Oxygen Jet

Reaction Zone

Base Metal

150

Figure 7

°

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– Non-contact temperaturemeasurement in real time.

– Fiber optics allow easy access to viewthe laser heating area because of theirrelatively small size.

– EITM compensates for variations inemissivity as the part is being heated.

– EITM response can be matched to theresponse speed of the laser.

Additional applications of interest:

FLAME CUTTINGAutomated flame cutting involves eitherpattern tracing or computer control torepetitively cut steel plates into a varietyof shapes. (See Figure 7.)

During start-up, a natural gas orpropane flame heats the metal plateuntil a “puddle” of molten metal isdetected by the operator; on multipleheat cutters the time may vary betweentorches. The puddle having beenformed, oxygen is injected into the gasstream and blows the molten metalthrough the plate at which time thecutting cycle begins.

If the oxygen is injected prematurely a defective cut is made leaving anobjectionable rough and wide pitlikedepression in the plate.

By positioning a fiber optic bundle with lens assembly to look through the “clean” flame at the plate surface,the temperature is monitored andcontrolled to maintain the necessarytemperature. By multiplexing and usinghi-lo logic with relays tied in series, theoxygen is not turned on until all setpointsand associated relays are closed, insuringhigh quality cuts.

FLAME HARDENING OF STEEL WHEELSHardening the surfaces of steel wheelsused on heavy construction equipmentsuch as drive & idler wheels forbulldozers, backhoes, and other tracktype equipment is presently beingaccomplished by flame hardening.

A flame head is positioned on eitherside of the wheel (Figure 8). As thewheel is rotated the flame impinges onthe surface elevating the temperature toapproximately 976°C. Within closeproximity to the flame the surface israpidly quenched with cooling water(Figure 9).

Because of the variations in the wheels,both in roundness and lateraldistortions, if the flame head were fixedthe hardening process would not beuniform throughout the critical areas.

By optically looking through the “clean”natural gas flame at the optimum pointon the wheel, Figure 10, the variationsin the temperature determined by theThermal Monitor provide a proportionalsignal which is fed to a pneumatictransducer which pneumo/mechanicallymoves the head to the correct position.

Substantial savings are realized byeliminating a previous costly process ofdestructive testing.

COKE GUIDE PYROMETERBy monitoring both level andtemperature, the Coke Guide Pyrometerassures the optimum efficiency in themanufacture of coke. The multiplexingof several detectors on a vertical planeallows the operator to measure bothheight and temperature of the coke inthe processing oven.

When desired parameters are met, acontroller signal activates the pusherto dump the processed coke into anawaiting transfer car, thus assuring a quality product and energyconservation.

The above are but a few of the manyand varied uses of fiber optics. Therange and applications for thesesystems is only limited by one'simagination. The technology isexpanding exponentially. Fiber opticsare no longer viewed with doubts andmisgivings. Like IC's, chips, bubblememories, RAM's, ROM's and PROM's,they are here to stay, they are thefuture.

Reproduced with permission of Vanzetti Instruments.

Flame Heads

Lens Assembly

Figure 8

OptimumMeasuring

Point

Figure 10

Flame

Quench

Figure 9

Fiber Optics Cont'd

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Handheld Infrared Thermometers for All Applications

The new OS520/OS530 series handheld infraredthermometers from OMEGA Engineeringadapt to virtually all remote temperaturemeasurement applications. Theseuniversal instruments combine the featuresfound in many specialized units into onehigh performance design. Ruggedassembly and state-of-the-artmeasurement techniques are an integralpart of these dependable and portabletemperature measuring tools.

IMPROVED MEASUREMENT ACCURACYSelect from models of the OS520/OS530 series withtemperature ranges from –18 to 2482°C (0 to 4500°F).Temperature readings are switchable from °F to °C via thekeypad. Reading accuracy is to 1%. This accuracy isobtained through a unique keypad emissivity adjustment. Theoperator sets the infrared gun to match target material emissivity(0.10 to 1.00 in 0.01 increments) thus eliminating targetemissivity error.

Units have standard “V” groove gun sights for proper aimingaccuracy. Laser sighting is an available option. Measurable targetdistances are from a few inches to approximately 200 feet (limited byline of sight and target size).

To assure the operator that the target fills the field of view, near andfar field-of-view diagrams are supplied with each unit and allinstruments are labeled with a distance versus spot size chart. Thedistance to spot size ratio is from 10:1 to 110:1 depending on the model.

VERSATILE DISPLAY AND PROGRAMMING FEATURESThe Custom backlit LCD display provides a dual parameter presentation.When the unit is turned on, the emissivity setting is displayed. Targettemperature is then displayed simultaneously with either minimum,maximum, differential, or average temperature as selectedby the operator.

Non-volatile memory assures that all set parameters,such as target material emissivity, alarm setpoints,etc., remain in memory until reset.

An electronic lock feature on the control panel keypad sets a triggermechanism for continuous measurements. With the triggerprogrammed in the lock position, the instrument reads and displaystemperature data up to 4 times per second. The electronic trigger is also used to enable/disable special functions like the audible/visual alarms.

ANALOG AND DIGITAL OUTPUTS FOR DATA PROCESSINGAnalog and digital outputs are available for data recording and processing. The analogoutput is 1 mV/°C or °F (0.5mV/degree for OS524); the digital output interface is RS-232.

High and low audible and visible alarms indicate preset temperature setpoints.

PATENT NOTICE

This product may be protected by one or more of the following patents:

U.S. PAT. D357, 194, 5,368,392, 5,524,984, 5,527,880, 5,465,838/Canada75811VOMEGA ENGINEERING, INC./Czech Republic 25372/France0378411 to 0378446/Germany M 94 06 478.4/Italy RM9400000913/Japan988.378/Netherlands 25009-00/Spain med. ut. 133292/Slovak Republic24565/U.K. Registered 2041153

Other U.S. and Foreign Patents Pending.

D

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THERMOCOUPLE INPUTFEATURE

The OS530 Series thermometers offerthermocouple input. This allowsmeasurement of target temperatureseither by contact or non-contact means.

RUGGED AND FUNCTIONALDESIGN EASES HANDLING

For safety and ease of carrying, a soft holster and wrist strap are suppliedwith each infrared thermometer. Rubberboots encapsulate the lens and thedisplay to ensure mechanical integrityduring rough handling or mechanicalshock.

The OS520/OS530 series features asealed keypad display. Uniquepackaging and styled design provideease of handling and convenient triggeroperation. The laser sighting optionensures added accuracy for targetacquisition and definition.

UNIVERSAL PROBLEM SOLVER

Handheld infrared thermometers are ideal for applications where non-contact temperature measurements are required. Typical examples include moving objects, materials in contaminated or hazardous areas, and locations of high voltage or veryhigh temperature. In each of theseenvironments, accurate and repeatablemeasurements are obtained at a safedistance using the OS520/OS530infrared thermometers.

DIVERSE APPLICATIONEXAMPLES

Example 1: Predict and Prevent Process FailureManufacturing and processing facilities,such as chemical and petrochemicalplants, utilize solenoid valves to controlcritical functions. The solenoids areoften inaccessible and difficult to test.Process engineers know that an upwardshift in solenoid temperature isindicative of a pending malfunction. Theportable OS520/OS530 thermometersare used to remotely sense thetemperature of the solenoid housings.Utilizing the instrument’s audible andvisual alarm system, a temperature shiftfrom a pre-set norm signals theoperator. The suspect solenoid valve isidentified and replaced before a criticalprocess failure occurs.

Example 2 :Perform Energy AuditingPlant and maintenance engineering are required to reduce building heatingcosts by locating wall insulation voids.Variations in wall temperatures indicateareas of improper insulation. TheOS520/OS530 series measures walltemperatures to identify areas of heatleakage. A unique target ambienttemperature compensation featureallows precise target (wall) temperaturemeasurement. Data is downloaded to acomputer for mapping of walltemperature gradients.

Example 3 :Identify Permanent Test SightsEngineering must determine if a processwarrants permanent temperaturemonitoring. Wide variations in processtemperature indicate the need for tightercontrols. The OS520/OS530 seriesmounts on a tripod for preliminaryevaluation of that process (integraltripod mount is standard). Temperaturesare measured and updatedautomatically using a unique trigger lockfeature. Data can be transmitted to arecorder or a computer for evaluation.The need for permanent temperaturemonitoring is evaluated using theanalyzed data.

Example 4:Prevent ContaminationMany processes in the food industry are sensitive to temperature limits andvariations. Maintaining tight temperaturecontrols of the processing, canning,packaging or freezing of food is criticalto prevent spoilage and to ensureelimination of contaminant’s. Placementof temperature measuring deviceswithin the food is discouraged due topossible introduction of impurities andcontaminant’s. A remote temperatureindicating instrument is required. TheOS520/OS530 handheld infraredthermometers take accuratetemperature readings without directcontact to food or packaging material.The instrument is adaptable to either atemporary or permanent installation.Intermittent measurements areperformed utilizing the handheldconfiguration. A permanent setup isestablished using the tripod mount andthe data downloading/ recordingcapabilities.

ENGINEERING SUPPORT

Unlimited applications and systemsupport are provided by the fullresources of OMEGA Engineering.Petrochemicals, pharmaceuticals, steelproduction, food processing, papermanufacturing and laboratory testingare just a few of the industries whereOMEGA applications and systemspersonnel are currently providing closecustomer support.

ALL-IN-ONE INDUSTRY LEADER

The OMEGA EngineeringOS520/OS530 series handheld infraredthermometers respond to the need for acomprehensive remote temperaturemeasuring instrument. Unique featuressuch as ambient target temperaturecompensation, electronic trigger lock,adjustable emissivity set, themocoupleinput and audible/visual alarms ensureaccurate and dependable readings. TheOS520/OS530 series are competitivelypriced, are manufactured and tested inthe United States and are CE approvedfor the European Market.

COMMON SPECIFICATIONSRepeatability: ±(1% of reading + 1 digit)Resolution: 1°F or 1°CResponse Time: 250 to 500 msecDisplay: Backlit LCD, displays currentand min., max., diff., or averagetemperature simultaneouslySpectral Response: 8 to 14 micronsEmissivity : 0.10 to 1.00 in 0.01incrementsDistance to Spot Size Ratio: From10:1 to 110:1 depending on the modelTemperature Range: –18 to 2482°C(0 to 4500°F)Operating Ambient: 0 to 50°C (32 to 122°F)Power: 4 “AA” size batteries or AC adaptorBattery Life: 60 hrs., alkaline;10 days, lithium under normal operation

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Principles of InfraredThermocouples

INTRODUCTIONIRt/c INFRAREDTHERMOCOUPLES –A REVOLUTIONARY NEWTEMPERATURE SENSINGTECHNOLOGYThe IRt/c product line represents adramatic breakthrough in temperaturesensing technology. The IRt/c sensorsare unpowered, low cost, and canmeasure surface temperatures ofmaterials without touching. They can be directly installed on conventionalthermocouple controllers, PLCs,transmitters, and other readout devices.

How do they measure temperature?

All IRt/c’s have a proprietary infrareddetection system which receives theheat energy radiated from objects thesensor is aimed at, and converts theheat passively to an electrical potential.A millivolt signal is produced, which isscaled to the desired thermocouplecharacteristics.

Since all IRt/c’s are self-powereddevices, and rely only on the incominginfrared radiation to produce the signalthrough thermoelectric effects, thesignal will follow the rules of radiationthermal physics, and be subject to thenon-linearities inherent in the process.

However, over a range of temperatures,the IRt/c output is sufficiently linear to produce a signal which can beinterchanged directly for a conventionalt/c signal. For example, specifying a 2% match to t/c linearity results in atemperature range in which the IRt/c will produce a signal within 2% of theconventional t/c operating over thatrange. Specifying 5% will produce asomewhat wider range, etc.

90.00

80.00

70.00

60.00

50.00

40.00

30.00

20.00

10.00

0.00

–10.00–50 50 150 250 350 450 550 650

mill

ivol

ts o

f sig

nal o

utpu

t

Actual Temperature (C)

The OS36-K-80 has its 2% linear rangecentered at 80°F (27°C), but produces arepeatable signal to 1200°F (650°C).

Target Temperature

Target Temperature

Sensor - Type - Temperature

Actual IR/tc Signal

millivoltoutput

Linear Range ***2% 5%

> 5%

Linear Range ***2% 5%

> 5%

0° 50°

100° 200° 300° 400° 500°

100° 150° 200° 250° 300° C

Special Biomedical Calibration ±0.2 C (35.5-39.4), ±0.3 C (25-40C)

0° 600° F

220C/440F 170C/340F 140C/280F 120C/240F

90C/180F 60C/140F 27C/80F 10C/50F

37C/98.6F

* - ** - * - ** - * - ** - * - ** - * - ** - * - ** - * - ** - * - ** - * - ** -

* Select OS36, OS36-2, or OS36-5** Select Type J, K, E, T

*** Temperature Range in which IRt/c output is linearcompared to conventional t/c, within stated % (of reading).

yyyyyyyyyy

yyyyyyyy yyyyy

yyyy

yyyy

yy

Temperature Selection Guide

Target Temperature

Target Temperature

Actual IR/tc Signal

millivoltoutput

Conventional thermocouple

millivoltoutput

The actual signal generated by the IRt/c can be approximated with a fourth order polynomial function of target temperature. This fourth power dependence is due to radiation physics, and not a limitation of the IRt/c.

The linear region matches the conventional t/c to a specified tolerance.

Linear region

OS36 Series

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Principles of Infrared Thermocouples Cont'd

Each IRt/c model is specificallydesigned for optimum performance in the region of best linear fit withconventional t/c’s, but can be usedoutside of those ranges by simplycalibrating the readout deviceappropriately. The output signal issmooth and continuous over its entirerated temperature range, and maintains1% repeatability over its entire range.

The Temperature Selection Guide is a summary of the linear rangeperformance of each IRt/c model. Theuser selects the IRt/c model and type,and the target temperature range for the application. The normal offsetadjustments on the thermocouplereadout device are used to calibrate the installation for emissivity andbackground effects.

How reliable are these new devices?

Of fundamental interest in temperaturecontrol is the ability of the measuringdevice to maintain its calibration underservice conditions, and over a longperiod of time. The IRt/c is rated at 1% (of reading) repeatability and tohave no measurable long termcalibration change, which makes it wellsuited for reliable temperature control.These attributes are inherent in thebasic design and construction of eachIRt/c.

Repeatability is defined as the ability of a measuring device to reproduce itscalibration under identical conditions.The IRt/c is a solid, hermetically sealed,fully potted system that does not changeeither mechanically or metallurgicallyduring service. There are no activeelectronic components and no powersource to produce the signal – only thethermoelectric effects that produce athermocouple signal. The 1% rating is a conservative value based on thepractical difficulty of demonstratingtighter tolerances under test conditions,rather than a true limitation of the device.

Long term accuracy is influenced by thesame things that influence repeatability:mechanical changes and metallurgicalchanges. It is well known thatthermocouples can change calibrationover time due to these effects.Mechanical changes occur becauseconventional thermocouples areconstructed generally as small and light as possible to enhance responsetime, thus making them vulnerable to deformations that can change the thermoelectric properties. Moreimportantly, the conventionalthermocouple must operate atelevated temperature since it merelymeasures its own temperature.

The metallurgical changes which affectthermoelectric properties are a strongfunction of temperature, being negligibleat room temperature, and of seriousconcern at high temperature.

The IRt/c solves both problems by its design and basic operation. Its solid fully potted construction in amechanically rigid stainless steelhousing, and operation at near roomtemperature conditions, essentiallyeliminates the classical drift problems ofconventional thermocouples. Every IRt/cis double annealed at temperaturesabove 100° C to ensure long termstability, and tested 5 times prior topackaging. Barring a very small

percentage of failure, the IRt/c hasessentially unlimited long termcalibration accuracy.

QUICK INSTALLATION GUIDEAll infrared-based sensing systemsmust be calibrated for specific materialsurface properties (for example, theamount of heat radiated from the targetsurface, environmental heat reflections,etc.). This calibration is performed bymeasuring the target surface temperaturewith a reliable independent surfacetemperature probe. The easiest andfastest method of accurately calibratingout these effects is to use an OMEGAOS91 hand-held Infrared Thermometerwith a patented Automatic EmissivityCompensation System to give a truereading regardless of emissivity.

The following procedure is recommended:

1. Install IRt/c as close as practical toview the target material to be measured.

2. Wire IRt/c to controller, PLCTransmitter, etc. in standard fashion(including shield). As in conventionalt/c’s, red wire is always (–).

3. Bring process up to normal operatingtemperature and measure actualtemperature of target material withOS90 Series Infrared Thermometer.

4. Adjust “input offset,” “zero,” “low cal,” on the readout device tomatch the OS91 reading.

Installation complete.

IRt/c at Room Temperature

Thermocouple Probe at Product Temperature

Conventional thermocouple operating at elevated temperature is subject to long-term drift, while the IRt/c operating at room temperature is stable.

3 1

2

4

+

–

Quick Installation Guide

The IRt/c gives repeatable static and dynamic readings.

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IRt/c SETUP WITH AUTO-TUNETEMPERATURE CONTROLLERS

In many applications, heating elementsare employed to heat a product in anoven, furnace, or with jets of hot air.Conventional control devices usingcontact thermocouples measure andcontrol the oven air temperature, IRheating element temperature, or air jettemperature in an effort to maintainproduct temperature and therefore,quality; often with less than satisfactoryresults.

Replacing the contact thermocouple,(for example measuring oventemperature) with a non-contact IRt/cmeasuring product temperature directly,will insure that product temperature ismaintained. Some readjustment of thecontroller parameters is requiredbecause of differences in sensorresponse times (an IRt/c is muchfaster), and time required to heat theproduct compared to the original sensor(slower). After installing the IRt/c andcalibrating the controller reading usingan OS91 Infrared Scanner (see QuickInstallation Guide below), initiate theself-tuning cycle of the controller andcheck to see that the control is stableand accurate. If it will not self tuneproperly, manually adjust the controlcoefficients to achieve stable control.Because the product temperature is likely to change temperature moreslowly than the original sensor, startwith slowly increasing the “D” of the PID coefficients.

IRt/c CAN BE USED WITHUP TO 1,000 FT (300 M) OFTHERMOCOUPLE EXTENSIONWIRE

With twisted shielded pair thermocoupleextension wire, an IRt/c can be mountedas far as 300 meters (1,000 ft) from the readout device, even in a very fierce electrical noise environment. Ademonstration test was performed witha 300 m (1000 ft) coil of twisted shieldedpair of extension wire, with 30 m (100 ft)unwound, connecting an IRt/c to a fast(100 msec. response) A/D conversionmodule to a computer. As a noisegenerator, a 60 Hz 10,000 volt transformerand spark generator was set up to sparkwithin 15 cm (6 inches) of the wire.

The test results showed less than 0.1°Cof noise at any relative position of thewire, spark, and transformer. Theextraordinary noise suppressioncharacteristics designed into the IRt/cmake it possible to locate it at very longdistances, without the necessity of atransmitter. The IRt/c housing is electricallyisolated from the signal leads and isconnected to the shielded ground of theextension cable. For long distances,twisted shielded extension cable shouldbe used, and the shield connected to agood electrical ground.

IRt/c’S ARE INTRINSICALLY SAFEWHEN USED WITH BARRIERS

“Field Apparatus having energy storingor generating characteristics of <1.2V,0.1A, 25 mW or 25 microJ shall beconsidered Simple Apparatus (non-energy storing). These general purposedevices may be used in a hazardous(classified) location without furtherapproval when connected to a certifiedintrinsically safe circuit.” – Quote from R. Stahl, Inc. Comprehensive ProductManual On Intrinsic Safety Barrier and Repeater Relays. Examples of non-energy storing Intrinsically SafeApparatus are:

• Thermocouples • RTD’s • LED’s• Dry Switch Contacts• NAMUR Inductive Proximity Switches• Non-inductive Strain Gage Devices

and Resistors

The IRt/c falls into the category ofthermocouples, since it generates itssignal by converting the radiated heatenergy to an electrical signal viaSeebeck effects, the basic driving force of thermocouples. Like allthermocouples, it requires no powersource and generates signals measuredin millivolts of voltage, microamps ofcurrent and nanowatts of power. IRt/c’shave a small capacitance, but at onemicroFarad, the energy storage ismeasured in nanojoules and is athousand times lower than the 25 microjoule criterion.

Accordingly, the IRt/c qualifies as aSimple Apparatus for use in hazardouslocations, and with the appropriatebarrier, qualifies as Intrinsically Safe.

Time

Product Temperature

Heat Input

10,000 V60 Hz

FastMeter

IRt/c

1000 ft (300 m)Twisted Shield Pair t/c Wire

Barrier

IRt/c

IRt/c’s are intrinsically safe when used with barriers

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IRt/c APPLICATION NOTESIRt/c MONITORS TIRE TEMPERATURES FORRACING PERFORMANCE

Tire temperature is of critical concern inautomotive racing for two reasons: thetire temperature directly affects itsadhesion and its wear characteristics;and tire temperature patterns providevaluable information on the set-up andperformance of the suspension. Forexample, excessive loading of a tirecaused by out-of-tune suspension willcause that tire to become considerablywarmer than the others.

The IRt/c is an ideal measuring devicefor on-board data acquisition, due to itssmall size, ruggedness, and low cost. It may be connected to standardthermocouple read-out systems.Installation should include connectingthe shield to a suitable ground in orderto avoid interference from theelectrically harsh environment of aracing automobile. Mechanicalinstallation should include attention toair flow patterns to minimize dirt buildingon the lens. The OS36-2 or OS36-5 arerecommended due to their narrowerfield of view, thus allowing you toposition it further away.

IRt/c RELATIVE HUMIDITYMEASUREMENTIRt/c’s can be used to measure actualrelative humidity in many situationswhere there is a convenient source of water and flowing air, and measure it accurately and reliably.

An IRt/c aimed at a wet porous surfacewith ambient air blowing across the wetsurface, can actually measure what iscalled “wet bulb” temperature for thatambient area. (More precisely, wet bulb temperature is the equilibriumtemperature of the air-water interfacewhen a water film is evaporated. Whenair is moved over a wet surface, thewater cools by evaporation until itreaches wet-bulb temperature, then the cooling stops, no matter how muchmore air is moved over the surface. Thetemperature at which the cooling stopsis the wet bulb temperature.)

The IRt/c measures the temperature of the air-water interface on a surfacedirectly. The quality of the water or ofthe absorbing material does not affectthe reading, since the IRt/c can directlyview the air-water interface, and the wetbulb equilibrium temperature is notmaterially affected by impurities.

The highest precision method is toemploy an IRt/c wired differentially with a conventional thermocouple to measure the quantity “wet bulbdepression”. The differential pairarrangement guarantees high accuracy, since RH is a strong functionof wet bulb depression and a weakfunction of dry bulb temperature.Standard psychrometric tables, charts, and software algorithms can be used with the data to obtainaccurate relative humidity for yourenvironmental measurements.

CONTROLLING WEB ROLLERTEMPERATUREThe IRt/c infrared thermocouples havequickly become the sensors of choicefor monitoring and controlling both weband roller temperatures. Tips on accurateroller temperature measurement:

1. Uncoated Metal or Chrome Rolls –Shiny, uncoated metal rolls are difficultfor any infrared sensor to properlysense the true temperature (the sensorwill see too many environmentalreflections). The solution to the problemis to simply: paint a small black stripe on an unused end of the roller. Aim theIRt/c sensor at the black paint stripe. It will then measure the temperatureaccurately and reliably regardless ofchanges in the surface conditions of therest of the roller.

If there is very little space on the edgeof the roller, move the sensor closer andpaint a very small black stripe. Theminimum spot size of the IRt/c is 8 mm(0.3 inches) and for the OS36-2 it is 4 mm (0.16 inches) when the sensor isbrought close to the surface.

2. Dull Metal Rollers – Dull metalrollers can provide a reliable signal. It is best to test the surface for reliability,though, as the surface emissiveproperties may shift via dirt, moisture,cleaning, etc. It is best, if in doubt, tosimply paint a stripe to eliminate thesevariations.

3. Non-metallic Surfaced Rollers –These will provide a reliable IR signal atany point the IRt/c is aimed. No paintedstripe is required.

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Principles of Infrared Thermocouples Cont'd

++

+

+

–

––

–

Air Flow

Wet BulbDepression

Temperature

Dry BulbTemperature

Relative Humidity Measurement

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CONTROLLING VACUUM FORMING ANDTHERMOFORMING PROCESSES For forming plastics, an excellentcombination of heating method andcontrol is radiant heat with an IRt/c forcontrol. They work extraordinarily welltogether, since both the heating andmeasuring occur right at the surface –where the plastic is located. The IRt/creading is unaffected by reflections fromthe heater, since the spectral responseof the 6-14 micron IRt/c lens filters outthe shorter wavelengths of the radiantheater energy.

The IRt/c may be mounted in betweenceramic heaters, or in the shroud orreflector of the radiant heater, such thatit can see in between the elements.Select the IRt/c standard, OS36-2 or OS36-5 model, depending on thefield-of-view required to see past theelements to the painted surface. Careshould be taken in mounting the IRt/c insuch a way as to keep its temperaturebelow 93°C (200°F) and to keep thelens clean. The OS36-2 is the preferredmodel for this application because of its small physical size with built-in airpurge. It can be used in temperatures to121°C (250°F) environments when theair purge system is used. Its narrowerfield-of-view allows more leeway inpositioning, and thus more flexibility ininstallation. For still narrower fields ofview, use the OS36-5 with its 5:1 FOV.

IRt/c CONTROLS PRINTEDCIRCUIT BOARD PREHEATDURING WAVE SOLDERINGAn excellent solution to the problem ofproper heater control for PC boardpreheat is an IRt/c. They workextraordinarily well together, since boththe heating and measuring occur right at the surface – where the solder mustflow. The IRt/c reading is unaffected byreflections from the heater, since thespectral response of the 6-14 micronIRt/c lens filters out any shorterwavelengths of the radiant heater energy.

For this application, the IRt/c may be mounted identically to VacuumForming/Thermoforming (above).

INDUCTION HEATER CONTROLThe induction heating process can bereadily controlled by the temperature of the part as measured by an IRt/c non-contact infrared thermocouple.Several issues should be considered in an installation.

1. The effect of the field on the IRt/c:since the measuring signal is electricallyisolated from the housing, the IRt/c willoperate in even a very strong field. The shield wire should be attached to a proper signal ground. If there isexcessive heating from the field,consider using the optional coolingjacket kit, with the same water sourceas is used to cool the coil.

2. The field-of-view: the preferredmethod is to view the part between the coil turns or from the end. Select the IRt/c model that best suits therequirements.

3. Part temperature: both the OS36-2and OS36-5 models can be used totarget temperatures of 1100°C (2000°F),and have linear ranges to 260°C (500°F).

ASPHALT TEMPERATUREMONITORINGAsphalt properties are particularlysensitive to temperature, and it isimportant that the asphalt is applied at the correct temperature in order to perform to its specifications.Accordingly, temperature monitoring is a common requirement, but thethermocouples normally used havesevere breakage problems due to theharsh abrasiveness of the material, andmust constantly be replaced at high costand interruption of production.

The IRt/c solves this problem directly,since the temperature is monitoredwithout contact. The normal thermocouplecontroller can be used – simply calibrateoffset if necessary. The OS36-2 andOS36-5 models are recommended dueto their built-in air purge, which will keepthe lens clean by preventing vaporsfrom condensing on the lens. TheOS36-2 can be mounted in the chute to view the asphalt through a small hole, while the OS36-5 can be mountedsome distance away due to its narrow5:1 field of view.

Reproduced with permission ofExergen Corp.

OS36-2Air

yyyyyyyy

OS36-2Air

Ceramic Heaters

OS36-5

OS36-2

IRt/c

Cooling Water

yyyyyy

Air

Air

OS36-5

OS36-2

OS36-2 and OS36-5models featurebuilt-in air purgeto keep these qualitythermocouples functioningefficiently and accurately,even in dirty environments

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Microcomputer Based IRTemperature TransducersCharles E. Everest, Everest Interscience, Inc.

Microcomputer based IR temperaturetransducers are superior to the readilyavailable analog types because in situcomputing can be used to correctdetector imperfections, provide three-figure emissivity compensation settings(including real-time control of emissivitycompensation during individualmeasurements), and process transducerdata, transmitting only salient informationand thereby reducing data load on the dataacquisition system (DAS) (see Figure 1).

The µC makes it possible also tocalibrate the transducer in real timewithout bothering the DAS unless afailure mode is detected. In situ datalogging and buffering for asynchronouspolling by the DAS is available. Thedata rate of the transducer can bematched to the data rate of the DAS.

CORRECTING DETECTORIMPERFECTIONS The thermal-type IR detectors used inmoderate-temperature IR thermometersall suffer from shortcomings, but thesecan be corrected by sophisticated dataprocessing techniques available withdigital computers. The sensitive area ofthe detector and its image spot on thetarget are conjugate images of eachother formed by the optics. Also, sincePlanck’s equation defines a spectralquantity, an increment of radiant power,dWT, for each micron of spectralbandwidth in the IR spectrum is radiatedfrom the target spot to the IR detectoraccording to the equation:

Furthermore, since the optical systemand its media are linear, bilateral

systems, an increment of radiant power dWD is transmitted from thedetector’s sensitive area to the targetspot according to the equation:

The net incremental radiant power flowfrom the target spot to the sensitive areais:

or:

where:

C1, C2 = absolute constantsf = optical gain of the IR focusing

opticsl = wavelength in micronseT = emissivity of the target surfaceeD = emissivity of the detector

surface

then:

From this basic energy balance equation,the target temperature is an exponentialfunction of the detector temperature TD.

The output signal from the IR detector is a minute voltage proportional to thedifference in temperature between thetarget and the detector body itself. Toobtain an accurate measurement of the target temperature, it is thereforenecessary to accurately measure thedetector body temperature and add the processed difference temperatureprovided by the IR detector.

If our embedded computer can improvethe accuracy of either of these componenttemperature measurements, the overalltarget temperature measurement isenhanced. In fact, the accuracy of both of these component temperaturemeasurements is significantly improvedusing computer enhancements, asexplained later.

Another troublesome detector errorsource that can be completely correctedwith the computer is DC drift caused by ambient temperature variations. The detector body temperature TD isprobably the most important variable the computer uses to improve overallsystem accuracy. The techniques bywhich the computer obtains this variablewith greatly enhanced accuracy areoutlined below.

TD spans the range of the naturalenvironment, from roughly -50 to 100°C.Over this range, the most precise andaccurate temperature measuringtransducer is the thermistor. It is rarelyused as the temperature referenceelement for IR thermometers, however,because its output signal is highly nonlinear, and, althoughextremely stable, its as-manufacturednominal values vary widely from unit to unit (production spread).

Most IR thermometer manufacturers are limited to simple analog correctiontechniques for their detector referenceelements and so must abandon themore accurate and stable thermistor for a less accurate but easier to useelement such as an integrated circuit,which outputs a linear current withtemperature.

Highly nonlinear transducer responsesare no problem for a computer,however, because they can becharacterized with a Taylor seriespolynomial of the form shown inEquation 6 with an order, n, high

eT eD[ - ]dleC2/lTT-1 eC2/lTD-1

l = l2C1fWnet = *l5 l = l1

C1f eTdWnet= [l5 eC2/lTT-1

- eD ] dleC2/lTD-1

dWnet = dWT-dWD

eDC1fdldWD =

l5 (eC2 /lTD-1)

eTC1fdldWT =

l5 (eC2/lTT-1)

OUTPUT CONNECTOR

MICRO–COMPUTER

ASCII

BCD

RS232-C

RS232-C

ADC

ANALOG

MUX

LOW NOISEREAMP

REFERENCETHERMISTOR

OPTICALCHOPPER

IRSENSOR

OPTICAL ASSY.

+9 VDC

A

Figure 1

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enough to give arbitrarily perfectlinearization correction for anytransducer’s curve:

A + BX + CX2 + DX3 + ... ZXn

An algorithm for a general solution ofthe equation is held as a subroutine inprogram memory, while the transducer-specific coefficients A,B,D,C ... Z areheld in firmware (EEPROM). Given the power of modern µC’s, complexmathematical operations like this arepractically free of hardware costs andcan be performed in real time quicklyenough not to affect the overall readingspeed. The bottom line is that actualdetector case temperature measurementsof 0.05°C absolute accuracy are routine.

The IR detector itself is anothertemperature transducer with a highlynonlinear and temperature-dependentresponse:

E0 = R • W

where:

E0 = detector output in voltsW = IR electromagnetic radiant power

in W/m2

R = responsivity (constant ofproportionality)

Responsivity is also a nonlinear functionof TD. It is typically grossly corrected inthe industry with a simple linear gaincorrection produced by a temperaturesensitive resistor in the preamplifierfeedback network. With an embeddedµC, a third-order Taylor series correctionusing the real-time values computed forTD will effect a complete error correctionfor less cost than the temperaturesensitive feedback resistor. Thesetechniques allow the price of newcomputer based digital IR temperaturetransducers to be no greater than that of their analog predecessors, even with greatly enhanced performance and accuracy.

WT, the net radiant target signal powerimpinging on the detector, is highlynonlinear with target temperature TT; forlow-temperature targets (TT<1000°F), itis also highly dependent on the detectortemperature itself (TD). WT is a spectralquantity that depends on the spectralwindow it passes through, as calculatedfrom Planck’s equation. For very wide

band IR thermometers measuring high-temperature targets, this characteristicapproaches the fourth order of theStefan-Boltzmann law:

W ; KoTT4

;

where:

TT = absolute target temperatureo = Stefan-Boltzmann constant K = a nonlinear function of TD

In present-day IR thermometers, K isusually combined with R of Equation 7 anda single linear compensation correctionis applied, even though they have differingslopes in TD. With Taylor series digitalcorrections, only three or four coefficientsneed to be stored for use with thegeneral purpose Taylor series algorithmto effect nearly perfect corrections ofboth coefficients independently.

The critical linearization of the TT4

term (in the equation above) is usually leftto linear approximation techniques. Theinstrument’s entire scale span is dividedinto a convenient number of curvedsections, usually between 6 and 12, and each section is approximated by astraight line that can be easily handledby analog techniques. Unfortunately,each section is accurately corrected at only two temperatures; othertemperatures in the section can be readout in error by as much as the entireaccuracy specification of the instrument,which was fixed at one of the accuratepoints of the highest section. Thus the ± linearity error specification is usuallyequal to, and in addition to, the spanaccuracy specification of the instrument.

In digital IR thermometers with embeddedµC’s, a Taylor series polynomial with as many as 7 terms, solved in real time,can effectively solve the fourth-powerrelationship between detector outputvoltage and target temperature.

Detector zero (or DC) drift is anotherimperfection that can be effectivelycorrected with an embedded µC.Thermal detectors usually havenegligible long-term zero drift understable ambient conditions but are quitesusceptible to thermal transients. Errorsof several degrees are common whentaking an instrument with a simple thermaldetector from one room to another witha different ambient temperature.

An effective way to correct this error is periodically to completely block theincoming IR radiation signal from thetarget with an optical chopper, whilemeasuring the remaining error signaland storing its value in computer memoryfor later subtraction from the measuredcomposite signal. This procedure canbe performed as often as necessary orconvenient under adaptive computercontrol. Whenever an inactive timeinterval can be identified by the computer,the procedure can be cycled withoutinterrupting the useful flow of information.If this asynchronous chopping is donefrequently as compared to the drift rateof the detector, nearly perfect DC zerorestoration can be achieved.

DIGITAL TARGET EMISSIVITYCOMPENSATION Extremely precise (three-figure) emissivitycorrections can be called up either fromas many as 10 values stored in residentEEPROM, or from complex, real-timeprograms dependent on target time-temperature relationships. An exampleof the latter is a program for compensationof the emissivity of an induction heatedsteel part, which oxidized as it heats to higher temperatures. The emissivitymay be quite low (;0.1) at lowtemperatures, but as it is rapidly heated,an oxide film forms on its surface, whichraises the emissivity according to itstime-temperature history. This time-temperature integral can be easilycalculated by the computer and thecorresponding emissivity value appliedto the temperature readout in real time.

EMBEDDED DATA PROCESSINGCHORES Transducer data can be preprocessedat the point of measurement to extractthe pertinent information for transmissionto the mainframe data processingsystem. For instance, only excess limitor out-of-range data may be desired. In this case, set point values can beprogrammed into the embedded computerfirmware so that only data above (orbelow) the set point will be transmitted,perhaps on a priority interrupt basis. On a serial digital interface bus, a priority interrupt hierarchy can bedefined that will maximize the number of drops (transducers) a single wire willaccommodate.

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AUTOMATIC CALIBRATION A smart transducer can be programmedto identify windows in data flow patternswhere a preprogrammed calibrationprocedure can be performed withoutaffecting useful data flow. For instance,if the IR thermometer is measuring thetemperature of cans proceeding down aconveyor belt, a gap between successivecans is sensed and the dead time duringthe gap is used to cycle the calibrationprocedure. The master DAS need notbe aware of the individual transducer’scalibration details unless an out-of-limitscondition occurs and the affectedtransducer initiates a priority interruptalarm.

INTEGRAL DATA LOGGING AND BUFFERINGBoth volatile and nonvolatile datalogging are built into the transducer.Volatile data logging with the residentRAM is used to assemble andtemporarily store on-line data either foruse in computations or to wait for buspolling. This ability to locally processand format data reduces the datatransfer time to the processor.Furthermore, because even fast IRthermometers are relatively slow (;ms)compared to electronic DASs (;µs),very little time is needed to service an individual digital IR thermometer on a data bus. The data can often becompressed into 50 µs/s, allowingdozens of drops (transducers) on asingle-wire pair (see section onInterface Management). Nonvolatiledata logging, via the embeddedEEPROM, is used to store significanthistorical data such as maximum,minimum, average, mean, and out-of-limit values for indefinite times.

IN SITU DIGITAL CONTROLINTELLIGENCEThe powerful integral microcontrollercan also be programmed to act on theincoming temperature data to performexternal control functions. There are 16multipurpose µC control ports availablefor command inputs from externalsignals such as simple switch closuresor photo-detector signals, or for controloutputs such as power relays. Each portcan directly drive an optically isolatedsolid-state relay capable of controlling a 10 kW load operating at 1600 Vdifferential from the transducer.

There are also four precision, low-levelanalog inputs available that can acceptauxiliary inputs from thermocouples,RTDs, or other IR detectors for supportfunctions. The simplest of these mightbe detection of temperatures above orbelow a preset threshold that has beenprogrammed into EEPROM. This setpoint could even be automaticallyprogrammed by the computer inresponse to input variable history. As many as four set points can bemonitored and controlled simultaneously.Among the more complex controlfunctions are complete local closed-loopPID control of a process temperatureentirely by the transducer with no externalhelp from other control electronics.

INTERFACE MANAGEMENT The computer’s data processing powerminimizes the hardware complexity ofthe transmission lines by managing bothelectrical power and data transmissionflow for the transducer. For example,the computer can function as a trafficcop to time share a single line amongseveral dozen transducers for bothpower and two-way data transmission.In addition, when the line is used forpower transmission, other transducerscan be connected to it and powered upat the same time. When the computerdisconnects line power, data can betransmitted so quickly that manyconnected transducers can be polledbefore the next power up. The bottomline is that inexpensive BNCs can beused with the transducers and a simple2-wire party line can service up to 16transducers over a distance of 1000 ft.

Another performance advantage accruesfrom the all-digital data transmission,which is far less susceptible to RFI/EMIthan is analog data transmission.Because the binary data transmission is serial in nature and is formatted forbilateral transmission on a single line, asingle fiber-optic line can be substitutedto provide complete immunity fromRFI/EMI, up to and including lightningstrikes. Finally, the savings on multipinconnectors and individual multiconductorcables is enough to pay for the µC, not to mention the greatly enhancedreliability from a single line system vs. six conductors.

SUMMARY The superiority of µC based IRtemperature sensing instruments over present generation analog IRthermometers is apparent. Thisstatement is supported by the enhancedaccuracy of temperature measurementsof the difference between the target anddetector body, and the measurement ofthe detector body itself. Also to be notedis the ability of the microcomputer basedinstrumentation to replace the linearapproximation techniques. Extremelyprecise emissivity correction is anotherplus, as are the automatic calibration,integral data logging, and in situ digitalcontrol intelligence capabilities. Thereduction in the cost of the interfacebetween the host computer and thetransducers can be substantial. Anextremely sophisticated IR temperaturemeasurement system can be providedat a cost that is equal to or less thanpreviously available analog systemswith limited capabilities.

Reproduced with permission ofEVEREST INTERSCIENCE, INC.

Microcomputer Based IRTemperature Transducers Cont'd

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Infrared thermocouples can be used with mostthermocouple meters or controller over a specifiedtemperature range. For example, the OS36-J-50Fwould have a 2% accuracy over the range of -18 to27°C (0 to 80°F).

The following table shows the series of equations thatpermit a determination of measured temperature bymeasuring the IR-TC’s output voltage. If desired, thecold junction (CJ) correction can be set at any knownconstant temperature, e.g., 25°C. If the CJ temperatureis not known and constant, it is suggested you use anOMEGA CJ connection device like a TRC IIIA or CJ-K.This will correct to 0°C and allow use of a standardvoltmeter without other cold junction compensation.The CJT term can then be dropped in the followingpolynomial table.

Infrared Thermocouples,Extended Temperature Ranges

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Polynomial Table for OS36, 37 and 38 Signal Output

A B C D E FOS36-J-50F/10C -6.14473E-09 2.08199E-06 -2.72953E-04 1.75317E-02 -5.84883E-01 1.53003E+01OS36-J-80F/27C -2.83996E-08 7.41635E-06 -7.54046E-04 3.79224E-02 -1.00406E+00 2.06592E+01OS36-J-140F/60C -4.31591E-08 1.06077E-05 -1.01002E-03 4.72155E-02 -1.14872E+00 2.20397E+01OS36-J-180F/90C -7.03138E-08 1.59337E-05 -1.39844E-03 6.02655E-02 -1.35167E+00 2.39075E+01OS36-J-240F/120C -1.05707E-07 2.23776E-05 -1.83521E-03 7.38926E-02 -1.54843E+00 2.55885E+01OS36-J-280F/140C -1.89514E-07 3.63996E-05 -2.70839E-03 9.89395E-02 -1.88106E+00 2.82034E+01OS36-J-340F/170C -2.99852E-07 5.33519E-05 -3.67751E-03 1.24452E-01 -2.19192E+00 3.04447E+01OS36-J-440F/220C -5.20472E-07 8.44263E-05 -5.30444E-03 1.63572E-01 -2.62438E+00 3.31770E+01OS36-K-50F/10C -1.59875E-08 4.63673E-06 -5.20959E-04 2.87368E-02 -8.24991E-01 1.86777E+01OS36-K-80F/27C -6.09875E-08 1.41502E-05 -1.27187E-03 5.61266E-02 -1.28905E+00 2.33472E+01OS36-K-140F/60C -1.42546E-07 2.87094E-05 -2.24003E-03 8.58077E-02 -1.71070E+00 2.68960E+01OS36-K-180F/90C -3.22615E-07 5.67063E-05 -3.86135E-03 1.29089E-01 -2.24604E+00 3.08183E+01OS36-K-240F/120C -5.08511E-07 8.28536E-05 -5.22978E-03 1.62069E-01 -2.61390E+00 3.32464E+01OS36-K-280F/140C -9.34497E-07 1.37576E-04 -7.84637E-03 2.19704E-01 -3.20171E+00 3.67952E+01OS36-K-340F/170C -1.62369E-06 2.18012E-04 -1.13401E-02 2.89601E-01 -3.84908E+00 4.03439E+01OS36-K-440F/220C -2.90564E-06 3.54076E-04 -1.67152E-02 3.87409E-01 -4.67308E+00 4.44530E+01OS37-K -7.13085E-08 2.30925E-05 -2.88585E-03 1.75033E-01 -5.35670E+00 8.58605E+01OS38-K -2.17588E+04 7.42505E+04 -9.73319E+04 6.14482E+04 -1.92711E+04 2.97242E+03OS38-K -3.01228E-08 9.50466E-06 -1.17636E-03 7.27752E-02 -2.41603E+00 4.88735E+01

OS38-K Alternative: Power Law Fit=298.0514(mV) 0 2864

TT = A·(mV)6 + B·(mV)5 + C·(mV)4 + D·(mV)3 + E·(mV)2 + F·(mV) + CJT

Maximum Minimum Test ConditionsRange Range

mV TT mV TT mV TT CJTOS36-J-50F/10C 70 466 -4 -47 5 89 25OS36-J-80F/27C 70 577 -3 -47 5 107 25OS36-J-140F/60C 70 634 -3 -47 5 112 25OS36-J-180F/90C 70 674 -3 -47 5 117 25OS36-J-240F/120C 65 671 -2 -46 5 122 25OS36-J-280F/140C 60 678 -2 -47 5 130 25OS36-J-340F/170C 55 674 -2 -46 5 136 25OS36-J-440F/220C 50 667 -2 -49 5 143 25OS36-K-50F/10C 70 551 -3 -47 5 101 25OS36-K-80F/27C 70 664 -3 -45 5 116 25OS36-K-140F/60C 65 685 -2 -47 5 126 25OS36-K-180F/90C 55 678 -2 -47 5 137 25OS36-K-240F/120C 50 671 -2 -49 5 143 25OS36-K-280F/140C 45 670 -2 -48 5 152 25OS36-K-340F/170C 45 681 -2 -45 5 160 25OS36-K-440F/220C 40 685 -1 -48 5 169 25OS37-K 70 957 0 0 5 341 25OS38-K 1 334 0 0 1 334 25OS38-K 80 1035 1 309 80 1035 262

OS38xxx-K Power Law 80 1046 0 0 5 473 25

Notes: TT = Target TemperatureCJT = Cold junction temperature at input added via the input Device (controller, indicator, PLC, etc.). A controlled constant 25°C is assumed here for most polynomials. It can be changed.mV = Signal produced by infrared thermocouple in millivolts.All temperatures in °C.Assumed target emissivity is 0.9 for all models except OS38 which has assumed emissivity 0.2.

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Infrared Window TransmissionRefractive Indexes for IR Windows

Transmission Range

Material n at wavelength µmBarium Fluoride 1.45 5Cesium Bromide 1.66251 10Cesium Iodide 1.73916 10Calcium Fluoride 1.399 5Germanium 4.003 10Lithium Fluoride 1.39 0.5Magnesium Fluoride No = 1.379 Ne = 1.391 0.5Potassium Bromide 1.526 10Potassium Chloride 1.454 10Sapphire 1.755 1Silicon 3.4179 10Silver Bromide 2.31 0.5Silver Chloride 1.980 10Sodium Chloride 1.49482 10Sodium Fluoride 1.238 10Strontium Fluoride 1.439 0.5Thallium Bromide 2.338 10Thallium Bromide-Chloride KRS6 2.1767 10Thallium Bromide-Iodide KRS5 2.37069 10Thallium Chloride 2.193 10Zinc Selenide 2.40 10Zinc Sulphide 2.2 10

Wavelength (µm)Reproduced with permission of Optovac Corporaton

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Infrared Quick HelpWhen to Use Infrared TemperatureMeasurement :

Surface Is:

Key Infrared ApplicationFactors

U Too Hot to Be MeasuredWith Thermocouples

U Too Large to BeMeasured Without aVery Large Number ofThermocouples

U Moving Too Much forThermocouple LeadWire to Accept WithoutBreaking

U At So High an ElectricalPotential That Use of aThermocouple Would BeDangerous

U So Low in Mass ThatThe Thermocouple ItselfWill Affect the UnknownSurface Temperature

U Too Fragile or Wet toAccommodateThermocouple Contact

U Too Active (Chemically)to Accept aThermocouple or ItsProbe

U In an Atmosphere That Is Hostile to aThermocouple

U Inaccessible to aThermocouple or ItsInstrumentation

U Near Noise ProducingElectric or MagneticFields

U Target Spot Size andDistance

U Target Material (forEmissivity)

U Fixed or Handheld UnitU Temperature Range

U Response TimeU Sighting SystemU EnvironmentU Viewing PortU Options Needed

Determination of InfraredEmissivity U Measure Surface

Temperature by SomeOther Means (AfterStopping Motion)

U Place Masking Tape onSurface (Emissivity 0.95)

U Drill Hole in Surface AtLeast Six Times as Deepas It Is Wide(Emissivity 0.95)

U Paint Surface Dull Black(M IR Region)

U Look up Emissivity inTable (Last Resort)

BB704 Series Blackbody CalibrationSource with Portable Design

OS520 Series Handheld InfraredThermometer

OS550 Sensor Head IndustrialNoncontact InfraredThermometer/Transmitter andOS550-MB Mounting Bracket

Z-88

Z

Alloys20-Ni, 24-CR, 55-FE, Oxid. 392 (200) .9020-Ni, 24-CR, 55-FE, Oxid. 932 (500) .9760-Ni , 12-CR, 28-FE, Oxid. 518 (270) .8960-Ni , 12-CR, 28-FE, Oxid. 1040 (560) .8280-Ni, 20-CR, Oxidized 212 (100) .8780-Ni, 20-CR, Oxidized 1112 (600) .8780-Ni, 20-CR, Oxidized 2372 (1300) .89AluminiumUnoxidized 77 (25) .02Unoxidized 212 (100) .03Unoxidized 932 (500) .06Oxidized 390 (199) .11Oxidized 1110 (599) .19Oxidized at 599°C (1110°F) 390 (199) .11Oxidized at 599°C (1110°F) 1110 (599) .19Heavily Oxidized 200 (93) .20Heavily Oxidized 940 (504) .31Highly Polished 212 (100) .09Roughly Polished 212 (100) .18Commercial Sheet 212 (100) .09Highly Polished Plate 440 (227) .04Highly Polished Plate 1070 (577) .06Bright Rolled Plate 338 (170) .04Bright Rolled Plate 932 (500) .05Alloy A3003, Oxidized 600 (316) .40Alloy A3003, Oxidized 900 (482) .40Alloy 1100-0 200-800 (93-427) .05Alloy 24ST 75 (24) .09Alloy 24ST, Polished 75 (24) .09Alloy 75ST 75 (24) .11Alloy 75ST, Polished 75 (24) .08Bismuth, Bright 176 (80) .34Bismuth, Unoxidized 77 (25) .05Bismuth, Unoxidized 212 (100) .06Brass73% Cu, 27% Zn, Polished 476 (247) .0373% Cu, 27% Zn, Polished 674 (357) .0362% Cu, 37% Zn, Polished 494 (257) .0362% Cu, 37% Zn, Polished 710 (377) .0483% Cu, 17% Zn, Polished 530 (277) .03Matte 68 (20) .07Burnished to Brown Colour 68 (20) .40Cu-Zn, Brass Oxidized 392 (200) .61Cu-Zn, Brass Oxidized 752 (400) .60Cu-Zn, Brass Oxidized 1112 (600) .61Unoxidized 77 (25) .04Unoxidized 212 (100) .04Cadmium 77 (25) .02CarbonLampblack 77 (25) .95Unoxidized 77 (25) .81Unoxidized 212 (100) .81Unoxidized 932 (500) .79Candle Soot 250 (121) .95Filament 500 (260) .95Graphitized 212 (100) .76Graphitized 572 (300) .75Graphitized 932 (500) .71Chromium 100 (38) .08Chromium 1000 (538) .26Chromium, Polished 302 (150) .06Cobalt, Unoxidized 932 (500) .13Cobalt, Unoxidized 1832 (1000) .23Columbium, Unoxidized 1500 (816) .19Columbium, Unoxidized 2000 (1093) .24CopperCuprous Oxide 100 (38) .87Cuprous Oxide 500 (260) .83Cuprous Oxide 1000 (538) .77Black, Oxidized 100 (38) .78Etched 100 (38) .09Matte 100 (38) .22Roughly Polished 100 (38) .07

Polished 100 (38) .03Highly Polished 100 (38) .02Rolled 100 (38) .64Rough 100 (38) .74Molten 1000 (538) .15Molten 1970 (1077) .16Molten 2230 (1221) .13Nickel Plated 100-500 (38-260) .37Dow Metal 0.4-600 (–18-316) .15GoldEnamel 212 (100) .37Plate (.0001)Plate on .0005 Silver 200-750 (93-399) .11-.14Plate on .0005 Nickel 200-750 (93-399) .07-.09Polished 100-500 (38-260) .02Polished 1000-2000 (538-1093) .03Haynes Alloy C, Oxidized 600-2000 (316-1093) .90-.96Haynes Alloy 25, Oxidized 600-2000 (316-1093) .86-.89Haynes Alloy X, Oxidized 600-2000 (316-1093) .85-.88Inconel Sheet 1000 (538) .28Inconel Sheet 1200 (649) .42Inconel Sheet 1400 (760) .58Inconel X, Polished 75 (24) .19Inconel B, Polished 75 (24) .21IronOxidized 212 (100) .74Oxidized 930 (499) .84Oxidized 2190 (1199) .89Unoxidized 212 (100) .05Red Rust 77 (25) .70Rusted 77 (25) .65Liquid 2760-3220 (1516-1771) .42-.45Cast IronOxidized 390 (199) .64Oxidized 1110 (599) .78Unoxidized 212 (100) .21Strong Oxidation 40 (104) .95Strong Oxidation 482 (250) .95Liquid 2795 (1535) .29Wrought IronDull 77 (25) .94Dull 660 (349) .94Smooth 100 (38) .35Polished 100 (38) .28LeadPolished 100-500 (38-260) .06-.08Rough 100 (38) .43Oxidized 100 (38) .43Oxidized at 1100°F 100 (38) .63Gray Oxidized 100 (38) .28Magnesium 100-500 (38-260) .07-.13Magnesium Oxide1880-3140 (1027-1727) .16-.20Mercury 32 (0) .09" 77 (25) .10" 100 (38) .10" 212 (100) .12Molybdenum 100 (38) .06" 500 (260) .08" 1000 (538) .11" 2000 (1093) .18" Oxidized at 1000°F 600 (316) .80" Oxidized at 1000°F 700 (371) .84" Oxidized at 1000°F 800 (427) .84" Oxidized at 1000°F 900 (482) .83" Oxidized at 1000°F 1000 (538) .82Monel, Ni-Cu 392 (200) .41Monel, Ni-Cu 752 (400) .44Monel, Ni-Cu 1112 (600) .46Monel, Ni-Cu Oxidized 68 (20) .43

Monel, Ni-Cu Oxid. at 1110°F1110 (599) .46NickelPolished 100 (38) .05Oxidized 100-500 (38-260) .31-.46Unoxidized 77 (25) .05Unoxidized 212 (100) .06Unoxidized 932 (500) .12Unoxidized 1832 (1000) .19Electrolytic 100 (38) .04Electrolytic 500 (260) .06Electrolytic 1000 (538) .10Electrolytic 2000 (1093) .16Nickel Oxide 1000-2000 (538-1093) .59-.86Palladium Plate (.00005on .0005 silver) 200-750 (93-399) .16-.17

Platinum 100 (38) .05" 500 (260) .05" 1000 (538) .10Platinum, Black 100 (38) .93" 500 (260) .96" 2000 (1093) .97" Oxidized at 1100°F 500 (260) .07" 1000 (538) .11Rhodium Flash (0.0002on 0.0005 Ni) 200-700 (93-371) .10-.18SilverPlate (0.0005 on Ni) 200-700 (93-371) .06-.07Polished 100 (38) .01" 500 (260) .02" 1000 (538) .03" 2000 (1093) .03SteelCold Rolled 200 (93) .75-.85Ground Sheet 1720-2010 (938-1099) .55-.61Polished Sheet 100 (38) .07" 500 (260) .10" 1000 (538) .14Mild Steel, Polished 75 (24) .10Mild Steel, Smooth 75 (24) .12Mild Steel,

Liquid 2910-3270 (1599-1793) .28Steel, Unoxidized 212 (100) .08Steel, Oxidized 77 (25) .80Steel AlloysType 301, Polished 75 (24) .27Type 301, Polished 450 (232) .57Type 301, Polished 1740 (949) .55Type 303, Oxidized 600-2000 (316-1093) .74-.87Type 310, Rolled 1500-2100 (816-1149) .56-.81Type 316, Polished 75 (24) .28Type 316, Polished 450 (232) .57Type 316, Polished 1740 (949) .66Type 321 200-800 (93-427) .27-.32Type 321 Polished 300-1500 (149-815) .18-.49Type 321 w/BK Oxide 200-800 (93-427) .66-.76Type 347, Oxidized 600-2000 (316-1093) .87-.91Type 350 200-800 (93-427) .18-.27Type 350 Polished 300-1800 (149-982) .11-.35Type 446, Polished 300-1500 (149-815) .15-.37Type 17-7 PH 200-600 (93-316) .44-.51Type 17-7 PH

Polished 300-1500 (149-815) .09-.16Type C1020,

Oxidized 600-2000 (316-1093) .87-.91Type PH-15-7 MO 300-1200 (149-649) .07-.19Stellite, Polished 68 (20) .18Tantalum, Unoxidized 1340 (727) .14" 2000 (1093) .19" 3600 (1982) .26" 5306 (2930) .30Tin, Unoxidized 77 (25) .04" 212 (100) .05Tinned Iron, Bright 76 (24) .05" 212 (100) .08

Material Temp °F (°C) ε–Emissivity Material Temp °F (°C) ε–Emissivity Material Temp °F (°C) ε–Emissivity

METALS

These tables are presented for use as a guide when makinginfrared temperature measurements with the OMEGASCOPE®

or other infrared pyrometers. The total emissivity (ε) for Metals,Non-metals and Common Building Materials are given.

Since the emissivity of a material will vary as a function oftemperature and surface finish, the values in these tables shouldbe used only as a guide for relative or delta measurements.The exact emissivity of a material should be determined whenabsolute measurements are required.

Table of Total Emissivity

Z-89

TitaniumAlloy C110M,

Polished 300-1200 (149-649) .08-.19" Oxidized at

538°C (1000°F) 200-800 (93-427) .51-.61Alloy Ti-95A,

Oxid. at 538°C (1000°F) 200-800 (93-427) .35-.48

Anodized onto SS 200-600 (93-316) .96-.82

TungstenUnoxidized 77 (25) .02Unoxidized 212 (100) .03Unoxidized 932 (500) .07Unoxidized 1832 (1000) .15Unoxidized 2732 (1500) .23Unoxidized 3632 (2000) .28Filament (Aged) 100 (38) .03Filament (Aged) 1000 (538) .11Filament (Aged) 5000 (2760) .35

Uranium Oxide 1880 (1027) .79ZincBright, Galvanized 100 (38) .23Commercial 99.1% 500 (260) .05Galvanized 100 (38) .28Oxidized 500-1000 (260-538) .11Polished 100 (38) .02Polished 500 (260) .03Polished 1000 (538) .04Polished 2000 (1093) .06


METALS

Adobe 68 (20) .90AsbestosBoard 100 (38) .96Cement 32-392 (0-200) .96Cement, Red 2500 (1371) .67Cement, White 2500 (1371) .65Cloth 199 (93) .90Paper 100-700 (38-371) .93Slate 68 (20) .97Asphalt, pavement 100 (38) .93Asphalt, tar paper 68 (20) .93Basalt 68 (20) .72BrickRed, rough 70 (21) .93Gault Cream 2500-5000 (1371-2760) .26-.30Fire Clay 2500 (1371) .75Light Buff 1000 (538) .80Lime Clay 2500 (1371) .43Fire Brick 1832 (1000) .75-.80Magnesite, Refractory 1832 (1000) .38Gray Brick 2012 (1100) .75Silica, Glazed 2000 (1093) .88Silica, Unglazed 2000 (1093) .80Sandlime 2500-5000 (1371-2760) .59-.63Carborundum 1850 (1010) .92CeramicAlumina on Inconel 800-2000 (427-1093) .69-.45Earthenware, Glazed 70 (21) .90Earthenware, Matte 70 (21) .93Greens No. 5210-2C 200-750 (93-399) .89-.82Coating No. C20A 200-750 (93-399) .73-.67Porcelain 72 (22) .92White Al2O3 200 (93) .90Zirconia on Inconel 800-2000 (427-1093) .62-.45Clay 68 (20) .39" Fired 158 (70) .91" Shale 68 (20) .69" Tiles, Light Red 2500-5000 (1371-2760) .32-.34" Tiles, Red 2500-5000 (1371-2760) .40-.51" Tiles,

Dark Purple 2500-5000 (1371-2760) .78ConcreteRough 32-2000 (0-1093) .94Tiles, Natural 2500-5000 (1371-2760) .63-.62" Brown 2500-5000 (1371-2760) .87-.83" Black 2500-5000 (1371-2760) .94-.91

Cotton Cloth 68 (20) .77Dolomite Lime 68 (20) .41Emery Corundum 176 (80) .86GlassConvex D 212 (100) .80Convex D 600 (316) .80Convex D 932 (500) .76Nonex 212 (100) .82Nonex 600 (316) .82Nonex 932 (500) .78Smooth 32-200 (0-93) .92-.94

Granite 70 (21) .45Gravel 100 (38) .28Gypsum 68 (20) .80-.90Ice, Smooth 32 (0) .97Ice, Rough 32 (0) .98LacquerBlack 200 (93) .96Blue, on Al Foil 100 (38) .78Clear, on Al Foil (2 coats) 200 (93) .08 (.09)Clear, on Bright Cu 200 (93) .66Clear, on Tarnished Cu 200 (93) .64Red, on Al Foil (2 coats) 100 (38) .61 (.74)White 200 (93) .95White, on Al Foil (2 coats) 100 (38) .69 (.88)Yellow, on Al Foil (2 coats) 100 (38) .57 (.79)Lime Mortar 100-500 (38-260) .90-.92Limestone 100 (38) .95Marble, White 100 (38) .95" Smooth, White 100 (38) .56" Polished Gray 100 (38) .75Mica 100 (38) .75Oil on Nickel0.001 Film 72 (22) .270.002 " 72 (22) .460.005 " 72 (22) .72Thick " 72 (22) .82Oil, LinseedOn Al Foil, uncoated 250 (121) .09On Al Foil, 1 coat 250 (121) .56On Al Foil, 2 coats 250 (121) .51On Polished Iron, .001 Film 100 (38) .22On Polished Iron, .002 Film 100 (38) .45On Polished Iron, .004 Film 100 (38) .65On Polished Iron, Thick Film 100 (38) .83PaintsBlue, Cu2O3 75 (24) .94Black, CuO 75 (24) .96Green, Cu2O3 75 (24) .92Red, Fe2O3 75 (24) .91White, Al2O3 75 (24) .94White, Y2O3 75 (24) .90White, ZnO 75 (24) .95White, MgCO3 75 (24) .91White, ZrO2 75 (24) .95White, ThO2 75 (24) .90White, MgO 75 (24) .91White, PbCO3 75 (24) .93Yellow, PbO 75 (24) .90Yellow, PbCrO4 75 (24) .93Paints, Aluminium 100 (38) .27-.6710% Al 100 (38) .5226% Al 100 (38) .30Dow XP-310 200 (93) .22Paints, Bronze Low .34-.80Gum Varnish (2 coats) 70 (21) .53Gum Varnish (3 coats) 70 (21) .50Cellulose Binder (2 coats) 70 (21) .34

Paints, OilAll colors 200 (93) .92-.96Black 200 (93) .92Black Gloss 70 (21) .90Camouflage Green 125 (52) .85Flat Black 80 (27) .88Flat White 80 (27) .91Gray-Green 70 (21) .95Green 200 (93) .95Lamp Black 209 (98) .96Red 200 (93) .95White 200 (93) .94Quartz, Rough, Fused 70 (21) .93Glass, 1.98 mm 540 (282) .90Glass, 1.98 mm 1540 (838) .41Glass, 6.88 mm 540 (282) .93Glass, 6.88 mm 1540 (838) .47Opaque 570 (299) .92Opaque 1540 (838) .68Red Lead 212 (100) .93Rubber, Hard 74 (23) .94Rubber, Soft, Gray 76 (24) .86Sand 68 (20) .76Sandstone 100 (38) .67Sandstone, Red 100 (38) .60-.83Sawdust 68 (20) .75Shale 68 (20) .69Silica,Glazed 1832 (1000) .85Silica, Unglazed 2012 (1100) .75Silicon Carbide 300-1200 (149-649) .83-.96Silk Cloth 68 (20) .78Slate 100 (38) .67-.80Snow, Fine Particles 20 (–7) .82Snow, Granular 18 (–8) .89SoilSurface 100 (38) .38Black Loam 68 (20) .66Plowed Field 68 (20) .38SootAcetylene 75 (24) .97Camphor 75 (24) .94Candle 250 (121) .95Coal 68 (20) .95Stonework 100 (38) .93Water 100 (38) .67Waterglass 68 (20) .96Wood Low .80-.90Beech P!aned 158 (70) .94Oak, Planed 100 (38) .91Spruce, Sanded 100 (38) .89


NON-METALS

Table of Total Emissivity Cont’d

Z-90

Z

The new CY7 Series Sensors from OMEGA representthe first truly new cryogenic sensor technologyintroduced in the last decade. The sensors incorporateuniform sensing elements that exhibit precise,repeatable, monotonic temperature response over awide range. The elements are mounted into rugged,hermetically sealed packages that have beenspecifically designed for proper behavior in a cryogenicenvironment.

The result is a family of sensors with temperatureresponses so predictable, tightly grouped, and stablethat the sensors can be routinely interchanged with oneanother.

A New Proprietary Silicon Diode Chip

The key to the sensor’s temperature response lies withthe basic sensing element itself. The small silicon chipin each sensor has a temperature characteristic that isso stable, so predictable, and conforms so well fromchip to chip, that the CY7’s sensors are the first mass-produced, interchangeable cryogenic sensors.

As shown on the graph on page Z-93, the temperatureresponse profile of a CY7 is comprised of two distinctelements. With their inherent dual sensitivity, CY7sensors can cover a wide temperature range (up to 475Kelvin) and at the same time exhibit high sensitivity forcritical low temperature measurement.

Precise thermal response of the sensing element itselfis of little benefit if thermal errors generated in installingand using the sensor swamp out its capability. It is inminimizing these frequently unsuspected errors that theCY7 excels.

A Sensor Package Designed for Cryogenics

Sensors for higher temperatures fall far short forcryogenic use. The complex thermal link between thesensing element and its entire environment must betaken into account, as must the effect of anymeasurement-induced self-heating of the sensor, if oneis to achieve accurate results. In addition, the packagemust also withstand repeated cycling to lowtemperatures without mechanical failure.

Cryogenic Temperature SensorsCY7 Series Silicon Diodes

USAMADE IN

Z-91

AverageSlope-2.3mV/K

AverageSlope-26mV/K

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.00 20 40 60 80 100 200 300 400

Temperature, K (kelvin)

Standard Temperature Response (Curve 10) for CY7 Series Sensors. All Sensors Track this Curve Within Specified Tolerance Bands.

Forw

ard

Volt

age

–– V

f (

volt

s)

0 10 20 30 40 50 60 70

The development of the CY7 Series has included thedesign of unique sensor packages to solve many of theproblems encountered in low temperature thermometry.For example, the CY7 hermetic package incorporates asapphire substrate for high electrical isolation yet goodthermal conductivity. The base bottom is metallized foreasy anchoring to a sample. Large strong leads form anintegral part of the package and are thermally sunk into thesubstrate. This simplifies making connections to the sensorand at the same time helps reduce measurement errorsthat could be caused by heat conduction along the leads.

10 Microampere Excitation CurrentKey to the achievement of error-free measurement is lowexcitation current. The lower the current, the less power isdissipated in the sensor and the less self-heating occurs.

One measure of the effectiveness of a cryogenic sensor’sthermal design is the variation in reading obtainedbetween operation in a vacuum at liquid heliumtemperature and immersion directly in the liquid. In a fieldwhere discrepancies of a degree or more have beenreported, OMEGA® CY7 sensors exhibit variations as lowas 5 millikelvin.

Cryogenic Temperature SensorsCY7 Series

2.0

1.5

1.0

0.5

0.00 50 100 150 200 250 300

Tolerance Bands for CY7 Series Sensors allow selection of appropriate (and economical) accuracy levels for a given application.

Tole

ranc

e, K

(kel

vin)

Temperature, K (kelvin)

BAND 4

BAND 2

BAND 1

CY7-SD The SD configuration is thesmallest package in this series, and is

designed primarily for bonding or clamping to a flatsurface. Since the sensing element is in best thermalcontact with the base (largest surface) of the package,the package should be mounted with that same surfacein good contact with the sample. Mounting materialsand methods which will not expose the sensor totemperatures above 200ºC are required. Lowtemperature indium-lead-tin based solder or lowtemperature epoxy is recommended. The SD packagestyle is usable at temperatures up to 475 K.

CY7-ET This convenientscrew-in package is formedby soldering a basic SD

configuration into a recess in one flat of a hexagonalcylinder. The cylinder terminates in a standard 6-32SAE thread. Thus the sensor can be threaded (fingertight only) into a mounting hole in the sample. A lightcoating of vacuum grease on the threads furtherenhances the thermal contact between the sensorpackage and the sample. The solder used in mountingthe SD package to this adaptor constrains the upperuseful temperature of this configuration to 325 K.

CY7-MT The MT packageis similar to the ET versionexcept the SD package is

mounted in a slot in the center of the cylinder and thestud is a 3 mm x 0.5 metric thread.

CY7-CO A spring-loadedclamp holds a standard SD sensorin contact with the surface of thesample in this configuration. Thisallows the sensor to be easilychanged or replaced. It also

enables the sensor to be used over its full operationaltemperature range of 1.4 to 475 K. Extra clamps areavailable to accommodate applications where frequentrelocation of the sensor is desirable. The 4-40 brassscrew used with this clamp has a formed shoulder sothat, once the screw is properly seated, the springapplies correct pressure to the clamp.

CY7-BO In addition to beingsoldered to the mounting block,the SD sensor in this design hasits leads thermally anchored(without epoxy) to the block viaa beryllium oxide insert. Sinceleads can be a significant heatpath to the sensing element, and

can lead to measurement errors when incorrectlyanchored, this configuration helps maintain the leadsat the same temperature as the sensor. Mounting ofthis block is accomplished with a 4-40 screw (notsupplied). Usable temperature range of the CY7-BOsensor is 1.4 to 325 K.

CY7-LR With a CY7-SD sensormounted on a slightly more than half-round cylinder, this package is

designed to be inserted into a 1/8 inch (3.2 mm) diameterhole. Low temperature epoxy can also be used to installthe sensor, although the mounting is much morepermanent in that case. As with other soldered downsensors, the temperature range of the CY7-LR extendsto 325 K.

CY7-CU In this configuration, the SD sensor isepoxied into a flat cylindrical disk and the sensor leadsare thermally anchored to that same disk. The unit canbe mounted to any flat surface with a 4-40 brass screw(not supplied). The CU style sensor is wired in a four-lead configuration with the leads comprised of a 36-inchlength of OMEGA’s color coded cryogenic wire.Temperature range is 1.4 to 325 K.

CY7-D1 This is a two-lead version of the the CY7-CU.

CY7-CY Some applications are best served by arelatively large, robust sensor, and the CY7-CY fills thatbill. It is very similar to the CU style except that the diskhas a larger center diameter with the mounting holedirectly in the center. The CY sensor has 36-inch heavyduty (30 AWG, PTFE coated) leads. Special attentionmust be paid to thermally anchoring the leads toprevent heat leak induced measurement error.

Probes The flexibility of the CY7 series sensorsmakes them ideal candidates for incorporation intovarious probes and thermowells. However, theindividualized nature of these applications usuallydemands customized designs.

Z-92

Z

®

Select the Sensor Configuration Best Suited to Your Application

Z-93

TABLE 1. Chebychev fit coefficients

2.0 to 12.0 KA(0) = 7.556358 VL = 1.32412A(1) = -5.917261 VU = 1.69812A(2) = 0.237238A(3) = 0.334636 A(4) = -0.058642A(5) = -0.019929A(6) = -0.020715A(7) = -0.014814A(8) = -0.008789A(9) = -0.008554

12.0 to 24.5 KA(0) = 17.304227 VL = 1. 11732A(1) = -7.894688 VU = 1.42013A(2) = 0.453442A(3) = 0.002243A(4) = 0.158036A(5) = -0.193093A(6) = 0.155717A(7) = -0.085185A(8) = 0.078550A(9) = -0.018312A(10) = 0.039255

24.5 to 100.0 KA(0) = 71.818025 VL = 0.923174A(1) = -53.799888 VU = 1.13935A(2) = 1.669931A(3) = 2.314228A(4) = 1.566635A(5) = 0.723026A(6) = -0.149503A(7) = 0.046876A(8) = -0.388555A(9) = 0.056889A(10) = -0.116823A(11) = 0.058580

100 to 475 KA(0) = 287.756797 VL = 0.079767A(1) = -194.144823 VU = 0.999614A(2) = -3.837903A(3) = -1.318325A(4) = -0.109120A(5) = -0.393265A(6) = 0.146911A(7) = -0.111192A(8) = 0.028877A(9) = -0.029286A(10) = 0.015619

PROGRAM 2. BASIC subroutine for evaluating thetemperature T from the Chebychev seriesequations (1) and (4). ACS is used to represent thearccosine function.

100 REM Evaluation of Chebychev series110 X = ((V-VL)-(VU-V))/(VU-VL)120 T = 0130 FOR I = 0 to Ndegree140 T = T + A(I)*COS(I*ACS(X))150 NEXT I160 RETURN

Cryogenic Temperature SensorsCY7 SeriesPolynomial Representation

Curve #10 can be represented by a polynomial equation basedon the Chebychev polynomials which are described below.Four separate ranges are required to accurately describe thecurve, with the parameters for these ranges given in Table 1.The polynomials represent Curve #10 on the preceding pagewith RMS deviations on the order of 10 mK.

The Chebychev equation is of the form

T(x) = Σ an tn (x) (1)n=0

where T(x) represents the temperature in kelvin, tn(x) is aChebychev polynomial, and an represents the Chebychevcoefficients. The parameter x is a normalized variable given by

x = (V-VL)-(VU-V) (2)(VU-VL)

where V is the voltage and VL and VU designate the lower andupper limits of the voltage over the fit range.

The Chebychev polynomials can be generated from therecursion relation

tn+1 (x)=2xtn(x)-tn-1(x), to(x)=1, t1(x)=x. (3)

Alternately, these polynomials are given by

tn(x)=cos[n*arccos(x)]. (4)

The use of Chebychev polynomials is no more complicatedthan the use of the regular power series, and they offersignificant advantages in the actual fitting process. The firststep is to transform the measured voltage into the normalizedvariable using equation (2). Equation (1) is then used incombination with equation (3) or (4) to calculate thetemperature. Programs 1 and 2 give sample BASICsubroutines which will take the voltage and return thetemperature T calculated from Chebychev fits.The subroutinesassume that the values VL and VU have been input along withthe degree of the fit, Ndegree. The Chebychev coefficients arealso assumed to be in an array A(0), A(1), ...,A(Ndegree).

An interesting property of the Chebychev fits is evident in theform of the Chebychev polynomial given in equation (4). Noterm in equation (1) will be greater than the absolute value ofthe coefficient. This property makes it easy to determine thecontribution of each term to the temperature calculation andwhere to truncate the series if the full accuracy is not required.

PROGRAM 1. BASIC subroutine for evaluating thetemperature T from the Chebychev series usingequations (1) and (3). An array Tc(Ndegree) shouldbe dimensioned.100 REM Evaluation of Chebychev series110 X= ((V-VL)-(VU-V))/(VU-VL)120 Tc(0) = 1130 Tc(1) = X140 T = A(0) + A(1) *X150 FOR I = 2 to Ndegree160 Tc(l) = 2*X*Tc(l-1)-Tc(l-2)170 T = T + A(l) *Tc(l)180 NEXT 1190 RETURN

®

Z-94

ZINTRODUCTION

Temperature resolution and accuracy are important, but arenot the only, considerations when choosing a temperaturesensor and its associated measurement system. Otherconsiderations include: sensor size or thermal mass, stabilityover time, response time, mechanical shock resistance,interchangeability, measurement system simplicity, cost,magnetic field effects, and resistance to ionizing radiation.The scope of this paper is limited to the estimation ofresolutions and accuracies possible when making cryogenictemperature measurements with commercially availabletemperature sensors.

Cryogenic temperature sensors have been developed basedon a variety of temperature-dependent properties (1).Common, commercially available sensors include resistors,capacitors, thermocouples, and semiconductor junctiondevices such as diodes or transistors. The temperature-dependent characteristics of such sensors are publishedelsewhere (2,3). Such sensors, suitable for use as asecondary or tertiary temperature standards, are of primaryconcern in this paper. Primary standards-grade sensors arevery sensitive to thermal and mechanical shock and aretherefore not suitable for ordinary laboratory or industrialtemperature measurements. Other temperature measurementtechniques such as gas, vapor pressure, acoustic, noise, andmagnetic susceptibility thermometry, are not covered by thispaper as they require much greater effort to implement or theyseverely constrain system design.

Temperature resolution is the smallest temperature changethat can be detected. The precision (or reproducibility orstability) is a measure of how closely the measured values aregrouped. Accuracy is indicated by the difference betweenmeasured and true values of a parameter. The accuracy of asingle measurement can be no better than the resolution, butis degraded by calibration and measurement errors. Therelevant equations for determining resolution and accuracydepend on whether the measurement is of the absolutetemperature or of a temperature change. In either case, theachievable resolution depends on 1) the sensorcharacteristics and 2) the measurement system resolution.The accuracy of a temperature measurement can beevaluated using error analysis.

ABSOLUTE TEMPERATURE RESOLUTIONThe temperature resolution εT of a thermometer measuring

a temperature T is limited by the measurement systemresolution εv according to the expression

εVεT = ———— (1)dV / dT

when the sensitivity dV/dT of the thermometer does notchange significantly within εT of the temperature, T. Themeasured parameter and the system resolution, V, areassumed to be voltages in Equation 1. The sensitivity dV/dTcan be written as I(dR/dT) in the case of a ohmic resistancethermometer excited with a constant current, I. Equation 1 canbe put in dimensionless form by dividing both sides by T anddividing the numerator and denominator of the right hand sideby V, yielding

εT εV / V εrel— = ——————— [ — (2)T (T / V) (dV /dT) S

The dimensionless group in the numerator is the relativemeasurement system resolution, εrel, consisting of themeasurement system resolution, εV, divided by the voltagemeasured. The denominator consists of S [ (T/V)(dV/dT),known as the specific sensitivity, giving the relative temperaturesensitivity of the thermometer at temperature T. The specificsensitivity is also equal to (d InV/d InT), the slope of theparameter versus temperature on a log-log plot. Note thatequations 1 and 2 can be made to apply to thermometers basedon other temperature-dependent properties (e.g., capacitance,resistance or pressure) by replacing V with C, R or P.

The dimensionless nature of Equation 2 makes somewhateasier the comparison of thermometers based on differenttemperature-dependent properties. Specific sensitivities ofsome representative cryogenic temperature sensors areplotted in Figure 1. Sensors of the same type made bydifferent manufacturers may have similar characteristics. Non-metallic sensors of the same type but different nominalresistances usually have different S versus T characteristics.Metallic resistance thermometers should all fall on the sameline with some exceptions: variations in residual resistancecause differences in specific sensitivity at lower temperatures,and the sensitivity of alloys such as Rh-Fe also depends onthe concentration of the active impurity.

A specific sensitivity in the 0.1 to 10 range is usually best fortemperature measurements over a wide range, although otherfactors can be much more important. A large specificsensitivity allows the resolution of small temperatures relativeto the temperature measured, but the temperature rangebecomes limited if the value of the property measuredbecomes too large or small to be determined accurately withthe measurement system.

The relative absolute temperature resolution is also afunction of the relative measurement system resolution, εrel =εv /V (εc/C for capacitance measurements). As an example, agermanium resistance sensor with a specific sensitivity of-2.14 and resistance of 1000 Ω at a temperature of 4.2 K, 1µA excitation current, and a measurement system with 1 µVresolution would provide an absolute temperature resolutionof about 2 mK. Note that the sensor excitation current affectsthe output voltage (V = IR), and thus the relativemeasurement system resolution, so the sensor and themeasurement system are not independent. Absolutetemperature resolutions calculated using Equation 2, thespecific sensitivities plotted in Figure 1, and sampleexcitations and system resolutions are plotted in Figure 2. Thetemperature resolutions plotted in Figure 2 were calculatedonly as a demonstration of how to calculate temperatureresolutions for a variety of different sensors; differentoperating conditions, sensor models, or measurementequipment can greatly affect the achievable resolution.

Optimization of the temperature resolution is dependent onboth the sensor properties and the measurement system. Theminimum resolvable temperature is not merely a matter offinding a sensor with the highest specific sensitivity. Someexamples of interactions between sensor properties andmeasurement system resolution follow.

Resolution and Accuracy of CryogenicTemperature MeasurementsD. Scott Holmes and S. Scott CourtsLake Shore Cryotronics, Inc., Westerville, Ohio 43081-2399

A procedure is outlined and typical data provided for calculation of achievable resolutions and accuracies using commerciallyavailable cryogenic temperature sensors suitable for use as secondary or tertiary standards. Differences between resolutionsachievable in absolute temperature measurements as opposed to measurements of temperature changes are discussed.Methods for estimating or determining errors are discussed and typical sensor calibration errors are given.

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1510

10 100 500

1

1

0.1

0.01

CGR

GR

CS-501

YSI

Rh-Fe

Au-FeThermocouple

GaAlAsDiode

Si Diode

ROPt

CLTS

As a first example, gold-iron versus chromel thermocoupleshave what appears to be a nearly ideal specific sensitivitynear unity across the entire 1 to 300 K temperature range. Unfortunately, thermocouplessuffer from very small signal output, which can decrease thetemperature resolution possible from a given measurementsystem. Thermocouples are also affected by nonuniformitiesin the wire and require a good understanding of thermocouplephysics for proper installation and operation (4).

A sensor with large specific sensitivity, such as agermanium resistor near 1 K, can be limited in resolution bypower dissipation constraints. The germanium crystal requiresstrain-free mounting for accurate temperature readings andlong term stability, but the strain-free mounting reduces thethermal contact between the sensor and the body whosetemperature is to be measured, making the sensor moresusceptible to self heating. The excitation current forgermanium and carbon-glass sensors is typically adjusted toproduce an output voltage in the 1 to 3 mV range, therebymaintaining a balance between signal level and powerdissipation. Other sensors such as platinum or thick filmresistors do not require strain-free mounting, so signal levelsof thin film or encapsulated platinum sensors can beincreased by operating with higher power dissipation. Thetrade off is that strain-free mounted platinum sensors aremore stable over time.

A diode is an example of a sensor that can have relativelylow specific sensitivity, but large signal level, typically on theorder of a volt. Potentials on the order of one volt can bemeasured with great resolution. Diodes, however, are non-ohmic and thus constrained to constant current operation,which can lead to self-heating problems at low temperatures.

Optimization of the absolute temperature resolution canrequire complex tradeoffs between sensor and measurementsystem costs and capabilities.

RELATIVE TEMPERATURE RESOLUTIONBetter resolution is possible with the same measurement

system when measuring temperature changes (relativetemperatures) smaller than the absolute temperature. Thereason for this fact is that only the change in the value, and notthe entire value, must be measured. In this case, Equation 2 isnot valid since the specific sensitivity is defined using the fullparameter value (e.g., V) whereas the relative system responserequires the change in the measured value (e.g., ∆V). Equation1 is valid, but provides little guidance for optimizing theresolution of relative temperature measurements. Equation 2can be modified to apply to relative temperature measurementsby multiplying the right hand side by (∆V/∆V), yielding theexpression

εT ∆V εV / ∆V ∆V εrel––– = –– –––––––––– [ –– —– (3)T V (T/V)(dV/dT) V S

The resolvable temperature is seen to be reduced by a factorof (∆V/V) if εrel remains the same as for an absolutetemperature measurement. In practice, the system resolution,εV, is ordinarily not reduced in proportion to the ratio (∆V/V) soless resolution gain is realized. Note that both equations 1and 3 implicitly or explicitly require knowledge of the absolutetemperature, T (the sensitivity dV/dT at temperature T isrequired in Equation 1). This problem can be avoided by usinga thermometer with a linear response to temperature.Alternately, the relative temperature can be measured withone thermometer while the absolute temperature is measuredwith a second thermometer, but the accuracy of the absolutetemperature measurement will affect the accuracy of therelative temperature measurement.

Temperature (K)Temperature (K)

Spe

cific

Sen

sitiv

ity (

S)

Abs

olut

e T

empe

ratu

re R

esol

utio

n, T

(K

)

Figure 1. Absolute values of specific sensitivities ofrepresentative commercial cryogenic temperature sensors.Model numbers refer to Lake Shore sensors except wherenoted. Au-Fe thermocouple: KP chromel vs. Au-0.07%Fe,CGR: CGR-1-1000 carbon-glass resistor, CLTS: VishayMicro-Measurements CLTS-2 metal foil gauge, CS-501: CS-501 capacitor, GaAlAs diode: TG-120P gallium-aluminum-arsenide @ 10 µA, GR: GR-200A-1000 germanium resistor,Pt: Pt-103 platinum resistor, Rh-Fe: RF-800-4 rhodium-ironresistor, RO: Scientific Instruments RO-600 ruthenium oxidesensor, Si diode: DT-470 @ 10 µA, YSI: Yellow SpringsInstruments 44003A thermistor.

Figure 2. Absolute temperature resolutions ofrepresentative commercial cryogenic temperature sensorsunder the following operating conditions: Au-Fethermocouple: versus KP chromel, CGR: 1-3 mV or I = 0.1µA minimum, CLTS: 10 µA, CS-501: 5 kHz charging current,GaAlAs diode: 10 µA, GR: 1-3 mV or I = 0.1 µA minimum,Pt: 100 µA, Rh-Fe: 300 µA, RO: 10 µA, Si diode: 10 µA, YSI:1 µW. Relative measurement system resolution: capacitance:εrel = 0.1 pF/C; voltage: εrel = 0.1 µV/V or 10-5, whichever islarger. Refer to Figure 1 for sensor identification.

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SOURCES OF MEASUREMENT ERROREquations 1 - 3 can be used to calculate the temperature

resolution (or error) once the measurement system resolution(or error) is specified. This section discusses the sources ofthe errors and how to determine their magnitudes. Errorsources include the sensor calibration, the applied excitation,measurement system calibration, thermal voltages, noise,sensor self-heating and poor thermal grounding of the sensor.

The total error arising from several independent errorsources is usually calculated in one of two ways. The worst-case error, εWC, can be estimated by direct summation of allerrors

εWC = ε1 + ε2 +···+ εi +···+ εn (4)

where εi is the i th of n total errors.

The most probable error, εMP, can be estimated byassuming a statistical distribution of errors, in which case theerrors are summed in quadrature according to

œßßßßßßßßßßεMP = ε12 + ε2

2 +···+εi2 +···εn

2 (5)

The worst-case and most probable errors must be computedfrom errors of the same dimensions. Dimensionless relativesystem errors can be summed using either Equations 4 or 5 andthen translated to temperature errors using Equations 2 or 3.

Getting statistical data suitable for addition by quadraturecan be a problem; instrument and sensor specificationscommonly give maximum rather than most probable or typicalvalues for errors. Two approaches may be taken to dealingwith maximum error specifications. The conservativeapproach is to use the specification limit value in worst caseor most probable error calculations. The less conservativeapproach is to assume a statistical distribution within thespecification limits and assume the limit is roughly threestandard deviations, in which case one-third of thespecification limit is used in error calculations. Themanufacturer may be able to supply additional information tohelp improve error estimates.

Voltage or Frequency Measurement ErrorsThe accuracy of instrumentation such as voltmeters and

frequency counters is subject to calibration uncertainty anddrift with time and operating temperature. Accuracies of suchinstruments should be available from the manufacturer.

Excitation Current ErrorThe temperature measurement error due to an error in the

excitation current can be calculated from Equation 2 byreplacing the quantity εV /V by the relative voltage change dueto the current error. The resulting expression is

εT (εI /I)(Rd/Rs)— = ————— (6)T S

where Rd and Rs are the dynamic and static resistances of thesensor. Note that the dynamic and static resistances of anohmic sensor are equal. Typical dynamic resistances of aLake Shore DT-470 silicon diode are 3000 Ω at 300 K, 1000Ω at 77 K, and 2800 Ω at 4.2 K, while the static resistancesare respectively 51.9 kΩ, 102 kΩ and 163 kΩ.

Thermal (Johnson) NoiseThermal energy produces random motions of the charged

particles within a body, giving rise to electrical noise. Theminimum rms noise power available is given by Pn = 4kT∆fn,where k is the Boltzmann constant and ∆fn is the noisebandwidth. Peak-to-peak noise is approximately five timesgreater than the rms noise. Metallic resistors approach thisfundamental minimum, but other materials produce somewhatgreater thermal noise. The noise power is related to current orvoltage noise by the relations: I = [Pn /R]1/2 and V = [PnR]1/2.The noise bandwidth is not necessarily the same as the signalbandwidth, but is approximately equal to the smallest of (5):

• π/2 times the upper 3 db frequency limit of the analog dcmeasuring circuitry, given as approximately 1/(4 Reff Cin)where Reff is the effective resistance across the measuringinstrument (including the instrument’s input impedance inparallel with the sensor resistance and wiring) and Cin is thetotal capacitance shunting the input; • 0.55/tr where tr is the instrument’s 10-90% rise time;• one Hz if an analog panel meter is used for readout; or• one-half the conversion rate (readings per second) of an

integrating digital voltmeter.

Thermoelectric Voltages and Zero OffsetsVoltages develop in electrical conductors with temperature

gradients when no current is allowed to flow (thermal EMF’s).Thermoelectric voltages appear when dissimilar metals arejoined and joints are held at different temperatures. Typicalthermoelectric voltages in cryogenic measurement systemsare on the order of microvolts.

A zero offset is the signal value measured with no input tothe measuring instrument. The zero offset can drift with timeor temperature and is usually included in the instrumentspecifications.

Thermoelectric voltages and zero offsets can be eliminatedfrom voltage measurements on ohmic resistors by reversal ofthe excitation current and use of the formula:

V = (V+ - V_)/2 (7)

where V+ and V_ are the voltages with respectively positiveand negative excitation currents. Alternating current (ac)excitation can also be used with ohmic sensors to eliminatezero offsets.

Measurements made in rapid succession might not allowtime for current switching and the required settling times. Theerror can be reduced by measuring the offset before and aftera series of rapid measurements and subtracting the offsetvoltage from the measured voltages. The sum of thethermoelectric voltages and zero offset can be calculated as

Vo = (V+ + V_)/2 (8)

Note that the resolution of Vo is practically limited by theresolution of the measurement system. The value of Vo can beexpected to vary little in a static system, but may changeduring a thermal transient under study. The value of Vo shouldbe rechecked as often as is practical.

The offset voltage Vo is best measured by reversing thecurrent through a resistor. Measurement of Vo with zeroexcitation current is also possible, but large resistances canproduce excessive time constants for discharge of anycapacitances in the circuit, requiring long waiting times beforeVo can be measured accurately.

Measurements on diodes do not allow current reversal. Thevalue of Vo can be estimated by shorting the leads at thediode and measuring the offset voltage with zero excitationcurrent at operating temperature.

Ground Loops and Electromagnetic NoiseImproper grounding of instruments or grounding at multiple

points can allow current flows which result in small voltageoffsets. One common problem is the grounding of cableshields at both ends. The current flow through ground loops isnot necessarily constant, resulting in a fluctuating errorvoltage.

Electromagnetic pickup is a source of additional noise.Alternating current noise is a serious problem in sensors withnonlinear current-voltage characteristics (6). Measurement ofthe ac noise across the terminals of the reading instrumentcan give a quick indication of the magnitude of this noisesource (thermal noise will be included in this measurement).Books on grounding and shielding can help to identify andeliminate both ground loops and electromagnetic noise (7,8).

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Self HeatingHeat dissipated within a temperature sensor causes its

temperature to rise, resulting in an error relative to thesensor’s surroundings. Self heating errors might not affectrelative temperature measurements. Attempting to correct forself heating errors by calculation or extrapolation is notconsidered good practice. An estimate of the self heating errorshould be included in the total error calculation instead. Aneasy way to check for self heating is to increase the powerdissipation and check for an indicated temperature rise.Unfortunately, this procedure will not work with diodes. Anindication of the self heating error can be made by reading thediode temperature in both a liquid bath and in a vacuum at thesame temperature, as measured by a second thermometer notdissipating enough power to self heat significantly.

Calibration UncertaintyCommercially calibrated temperature sensors should have

calibrations traceable to international standards. Calibrationuncertainties for sensors calibrated by Lake Shore areprovided later in this paper. The calibration uncertainty of thetemperature sensor must be included in accuracy calculations.

Interpolation ErrorsOnce a calibration has been performed, an interpolation

function is required for temperatures which lie betweencalibration points. The interpolation method must be chosenwith care since some fitting functions can be much worse thanothers. Common interpolation methods include linearinterpolation, cubic splines and Chebychev polynomials.Formulas based on the physics of the sensor material maygive the best fits when few fit parameters are used.

Use of an interpolation function adds to the temperaturemeasurement uncertainty. The additional uncertainty due to aninterpolation function can be gauged by the ability of theinterpolation function to reproduce the calibration pointtemperatures from the calibration point resistances. LakeShore calibration reports include the mean and largestdeviations. Fitting with Chebychev polynomials is standardpractice. Each calibration can be broken up into severalranges to decrease the fitting errors. Typical errors introducedby the interpolation function are on the order of one-tenth thecalibration uncertainty.

CALIBRATION SYSTEM EXAMPLEThe example to be discussed in detail is the cryogenic

temperature calibration facility operated by Lake Shore. Thisfacility is designed to calibrate a variety of resistance anddiode temperature sensors over the temperature range of 1.2 to 330 K.

Physical ConstructionCalibrations are performed by mounting sensors on a probe

to be inserted in a liquid helium cryostat (see Figure 3). Thesensors are mounted in a gold-plated OFHC coppercalibration block which provides an isothermal environment.Special adapters and a variety of calibration blocks allowcalibration of sensors with varying shapes and sizes. Theelectrical leads from the sensors are soldered to contactsthermally anchored to a second gold-plated OFHC copperblock directly above the calibration block. The thermalanchoring block is attached to a flange, on top of which is aliquid helium subpot. Surrounding the thermal anchoring andcalibration blocks is an isothermal OFHC copper shield. Theshield has a resistance wire heater wound around the outsidewith several layers of super-insulation overwrap to reducethermal radiation to or from the vacuum can. Thermoelectricvoltages are minimized by using continuous wire from thethermal anchoring block to the low thermal EMF connectors atthe top of the probe which is at room temperature.

OperationDuring cooldown, a small amount of helium gas is introduced

into the vacuum chamber to act as a transfer medium. Thecryostat is then filled with liquid helium and the calibration

block and surrounding chamber cool to a nominal temperatureof 4.2 K. The transfer gas is then pumped out. To obtaintemperatures below 4.2 K, the subpot is filled with liquidhelium and vacuum pumped. As the vapor pressure of thehelium liquid in the subpot decreases, the temperaturedecreases. The pumping is controlled by a high resolutionpumping valve. The subpot bath temperature is not activelycontrolled. Depending on the pumping speed and basepressure, temperatures as low as 1.05 K can be reached. Toobtain temperatures above 4.2 K, the subpot is pumped dryand the heater is energized by the temperature controller. Adiode monitors the nominal temperature of the isothermalshield and calibration block and the temperature is read bythe temperature controller. The heater is used to bring thetemperature to a point just below the desired temperature.The heater power is then reduced so that the temperature isincreasing on the order of a millikelvin per minute. Data aretaken when the drift rate is sufficiently small (typically about10 minutes).

Electronic EquipmentThe electronic equipment used in this facility consists of a

HP3456A voltmeter, a Keithley model 224 variable currentsource, five Lake Shore model 8085 scanners, a Lake ShoreDRC-82C temperature controller, five Guildline 9330 standardresistors (10 Ω, 100 Ω, 1 kΩ, 10 kΩ and 100 kΩ values), a1000 Ω germanium standard thermometer and a 100 Ωplatinum standard thermometer. Other electronic equipmentsuch as the computer used for system control has no effecton the accuracy of the system. A block diagram of theequipment connection scheme is shown in Figure 4. Dataacquisition is computer controlled. Two scanners are used toswitch between each of twenty unknown sensors, onescanner is used to place one of the standard resistors into thecircuit, one scanner chooses between the germanium andplatinum standard, and the last scanner chooses whether thevoltmeter measures the voltage drop across the unknownsensor or the standard resistor.

Figure 3. Calibration cryostat schematic

computer

current source

scanners

voltmeter

temperaturesensors

standardresistors

Figure 4. Thermometer calibration facility instrumentationblock diagram

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Resistance MeasurementsThe resistance of a sensor is measured by comparison with

a standard resistor. Long term stability of resistor standardstends to be somewhat better than the long term stability ofcurrent sources, so overall accuracy is improved overmethods relying on a calibrated current source.

The normal operating procedure is to place a resistorstandard in series with the sensor whose resistance is to bemeasured. A voltmeter reading is taken with current in boththe forward and reverse directions across the sensor.Voltmeter readings are then taken with current in both theforward and reverse directions across the standard resistor.The resistance of the sensor can be calculated using therelation

(V+ - V_)sensorRsensor = —————————— x Rstandard (9)(V+ - V_)standard

where V+ and V_ are the voltages measured with current in theforward and reverse directions respectively. Measuring andaveraging voltage for current in both forward and reversedirections serves two purposes: errors due to thermoelectricvoltages are eliminated and voltmeter offsets are canceledout. In this situation, the voltmeter transfer specification, ratherthan the absolute measurement specification, applies. Thegain in accuracy is about a factor of ten over using thevoltmeter as an absolute measurement device.

Diode MeasurementsDiode measurements are no more difficult to perform but

typically less accurate. The reduced accuracy is aconsequence of the nonlinear current-voltage characteristic ofdiodes. The voltage across the diode can be measured only inthe forward direction, so the voltmeter must now make anabsolute measurement. Without current reversal,thermoelectric voltages and voltmeter offsets may be presentand these directly affect the achievable accuracy. The long-term accuracy and stability of the current source is also afactor. Fortunately, the small dynamic resistance reduces theerror due to small current errors by a factor of 100 to 1000 (6).

CalibrationCalibration is accomplished by comparison calibration

against standard thermometers. Two standard thermometersare used: a germanium resistance thermometer for the 1 to 28K range and a platinum resistance thermometer for the 28 to330 K range. A standard sensor reading is taken before andafter every unknown sensor reading. The initial and finalreadings are averaged to compensate for temperature driftsbetween the time the standard and unknown are read.

Total System Accuracy CalculationThe attainable accuracy for a temperature measurement

system depends on a number of variables. Lake Shore basesits calibrations on a calibrated voltmeter and calibratedworking resistance standards to transfer a temperature scalefrom working temperature standards to unknown resistancetemperature sensors. Calculating the total system accuracyrequires information such as absolute and transferspecifications for equipment being used and a deratingschedule for the calibration of the equipment. Some of thisinformation is normally supplied with the equipment, but otherparts are not. The manufacturer is the best source for thisinformation. Keep in mind, however, that the degradation ofthe equipment is directly dependent upon its use andtreatment.

Our voltmeters are calibrated every six months to ensurethey meet their transfer specifications. Primary standardresistors are calibrated once per year. The working resistancestandards are calibrated every six months against the primarystandard resistors.The following table lists typical uncertaintiesfor the 10 Ω, 100 Ω, 1000 Ω and 10 kΩ working standard

Table I. Uncertainty estimates for calibrations of workingstandard resistors. Errors and uncertainties are expressed inparts per million (±ppm). Typical values are calculated byquadrature (MP) and worst case (WC) values by directsummation.

Nominal 1 Year Base Error From TotalValue of Uncertainty Possible UncertaintyWorking of Primary Voltmeter Room for WorkingStandard Standard Transfer Temperature StandardResistor Resistor Accuracy Fluctuations Resistor

R (Ω) A B C MP WC

- -100 15 6 5 17 26

1000 15 6 5 17 2610000 20 6 5 22 31

CGR-1-1000 GR-200A-1000 PT-103[mK] [mK] [mK]

T (K) MP WC MP WC MP WC

1.5 4 5 4 5 - -4.2 4 5 4 5 - -

10. 4 5 4 5 - -20. 10 20 8 15 15 2530. 20 35 12 25 10 2050. 30 55 20 35 10 20

100. 65 125 45 90 10 20300. 250 450 - - 20 35

T CGR-1-1000 GR-200A-1000 PT-103(K) (mK) (mK) (mK)1.5 1 1 -4.2 1 1 -

10. 3 2 -20. 10 6 1430. 19 10 550. 41 20 3

100. 110 76 6300. 425 - 16

T [K] <10 20 30 50 100 300εT [mK]: 5 10 15 15 15 20

Table II. Temperature measurement uncertainties inmillikelvin for carbon glass (CGR), germanium (GR) andplatinum (PT) sensors.

Table III. Uncertainties in realizing the ITS-90 temperaturescale at the Lake Shore calibration facility.

Table IV. Total temperature measurement uncertaintiesrelative to ITS-90 in millikelvin for carbon glass (CGR),germanium (GR) and platinum (PT) sensors.

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resistors. Uncertainties arise from shifts in the primarystandard resistances, limitations of the voltmeter as a transferdevice, and dependence of the voltmeter and standardresistors on variations in room temperature.

The total errors from the standard resistors due tocalibration shifts and operating temperature variations arelisted in Table I in terms of parts per million (ppm). Theuncertainty estimates can be converted into equivalenttemperature uncertainties given the temperature and specificsensitivity of the sensor measured using Equation 2.

Using the voltmeter as a transfer standard gives animproved accuracy over using it to make absolutemeasurements. The transfer accuracy of the voltmeter isroughly ±10 counts which translates to about ±1 µV on anabsolute scale in the millivolt range. Signals for carbon glassand germanium sensors are kept between 1 and 3 mV so thisis equivalent to a relative accuracy, εrel, of about 0.05%.Platinum sensors are read at a power somewhat less than 10 µW and produce voltage signals ranging from 3.5 mV at30 K (1 mA current) to 27.5 mV at 300 K (0.25 mA). Thevoltmeter relative accuracy for 100 Ω platinum sensors rangesfrom 0.03% at 30 K to about 0.0036% at 300 K. Higheraccuracy at higher temperatures is also observed in rhodium-iron sensors. Equivalent temperature uncertainties are givenin Table II for a typical carbon glass resistor (model CGR-1-1000), germanium resistor (model GR-200A-1000) and aplatinum resistor (model PT-103). The uncertainties due tocalibration transfer of the resistance standards and that of thevoltmeter transfer accuracies have been added together inthis table.

Another important source of error comes from the errorlimits assigned to the secondary temperature standardscalibrated by national standards laboratories. Based onestimates given in NBS Monograph 126 concerning theaccuracy of the fixed points maintained at NIST (NationalInstitute for Standards and Technology, formerly NBS) andthe variations observed in platinum thermometers, anuncertainty estimate of ±5 mK can be made. Added to thisuncertainty is the measurement uncertainty from Table II.Germanium standards (1000 Ω) are used below 28 K andplatinum standards (100 Ω) are used above 30 K. Themeasurement uncertainty added to the calibration uncertaintyof the secondary temperature standards gives the overalluncertainty in realizing the ITS-90 temperature scale. Theuncertainty of Lake Shore calibrations relative to ITS-90 isgiven in Table III at several temperatures. The temperatureresolution of the Lake Shore Calibration Facility is generally afactor of 10 or more better than our accuracy specification.

The total error of a given calibration is the combination ofthe first three tables. The total error is given in Table IV for thesame representative temperature sensors included in Table II.The total uncertainty is expressed as millikelvin deviation fromITS-90. Two columns are given for each sensor. The “MP”column is the estimated most probable error of a givencalibration computed using summation by quadrature. The“WC” column is the unlikely worst case error computed bydirect summation of all error sources.

CONCLUSIONThe accuracies stated apply only to the sensors as calibrated.

An end user must be careful to distinguish between the desiredmeasurement accuracy and the calibration accuracy of thesensor alone. Errors introduced by the user’s measurementsystem, rough handling and inadequate thermal contact will addto the calibration uncertainty.

An estimate of the accuracy of a temperature sensor can bemade by combining the errors due to calibration, interpolationand the measurement system. Errors can be added inquadrature to give the most probable error, or can be summeddirectly to give worst case error.

REFERENCES1. L.G. Rubin, B.L. Brandt and H.H. Sample, “Cryogenic

thermometry: a review of recent progress, II,” Cryogenics22 (1982) 491-503.

2. L.L. Sparks, “Temperature, strain and magnetic fieldmeasurements,” in Materials at Low Temperatures, R.P.Reed and A.F. Clark, eds., American Society for Metals,Ohio (1983) 515-571.

3. S.S. Courts, D.S. Holmes, P.R. Swinehart and B.C.Dodril l , “Cryogenic thermometry—an overview,”Applications of Cryogenic Technology, Vol. 10, PlenumPress, New York (1991) 55-69.

4. P.L. Walstrom, Spatial dependence of thermoelectric voltagesand reversible heats, Am. J. Phys. 56 (1988) 890-894.

5. Low Level Measurements, Keithly Instruments, Inc.,Cleveland, Ohio, U.S.A. (1984).

6. J.K. Krause and B.C. Dodrill, “Measurement systeminduced errors in diode thermometry, Rev. Sci. Instrum. 57(1986) 661-665.

7. H.W. Ott, Noise Reduction Techniques in ElectronicSystems, John Wiley & Sons, New York (1976).

8. R. Morrison, Grounding and Sheilding Techniques inInstrumentation, John Wiley & Sons, New York (1977).

Reproduced with permission of the American Institute of Physics andLake Shore Cryogenics.

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Heat Wave A National Problem

Heat kills by taxing the human body beyond its abilities.In a normal year, about 175 Americans succumb to thedemands of summer heat. Among the large continentalfamily of natural hazards, only the cold of winter–notlightning, hurricanes, tornadoes, floods orearthquakes–takes a greater toll. In the 40-year periodfrom 1936 through 1975, nearly 20,000 people werekilled in the United States by the effects of heat andsolar radiation. In the disastrous heat wave of 1980,more than 1,250 people died.

And these are the direct casualties. No one can knowhow many more deaths are advanced by heat waveweather - how many diseased or aging hearts surrenderthat under better conditions would have continuedfunctioning.

North American summers are hot; most summers seeheat waves in one section or another of the UnitedStates. East of the Rockies, they tend to combine bothhigh temperature and high humidity although some ofthe worst have been catastrophically dry.

NOAA’S National Weather Service HeatIndex ProgramConsidering this tragic death toll, the National WeatherService (NWS) has stepped up its efforts to alert moreeffectively the general public and appropriate authoritiesto the hazards of heat waves - those prolongedexcessive heat/humidity episodes.

Based on the latest research findings, the NWS hasdevised the “Heat Index” (HI), (sometimes referred to asthe “apparent temperature”). The HI, given in degreesF, is an accurate measure of how hot it really feelswhen relative humidity (RH) is added to the actual airtemperature.

To find the HI, look at the Heat Index Chart. As anexample, if the air temperature is 95°F (found on the leftside of the table) and the RH is 55% (found at the top ofthe table), the HI - or how hot it really feels - is 110°F.This is at the intersection of the 95° row and the 55%column.

IMPORTANT: Since HI values were devised for shady,light wind conditions, EXPOSURE TO FULLSUNSHINE CAN INCREASE HI VALUES BY UP TO15°F. ALSO, STRONG WINDS, PARTICULARLY WITHVERY HOT, DRY AIR, CAN BE EXTREMELYHAZARDOUS.

Note on the HI chart the shaded zone above 105°F.This corresponds to a level of HI that may causeincreasingly severe heat disorders with continuedexposure and/or physical activity.

The “Heat Index vs. Heat Disorder” table (next to the HIchart) relates ranges of HI with specific disorders,particularly for people in higher risk groups.

Summary of NWS’s Alert ProceduresThe NWS will initiate alert procedures when the HI isexpected to exceed 105°-110°F (depending on localclimate) for at least two consecutive days. Theprocedures are:

• Include HI values in zone and city forecasts.

• Issue Special Weather Statements and/or PublicInformation Statements presenting a detaileddiscussion of (1) the extent of the hazard including HIvalues, (2) who is most at risk, (3) safety rules forreducing the risk.

• Assist state/local health officials in preparing CivilEmergency Messages in severe heat waves.Meteorological information from Special WeatherStatements will be included as well as more detailedmedical information, advice, and names andtelephone numbers of health officials.

• Release to the media and over NOAA’s own WeatherRadio all of the above information.

How Heat Affects the BodyHuman bodies dissipate heat by varying the rate anddepth of blood circulation, by losing water through theskin and sweat glands, and - as the last extremity isreached - by panting, when blood is heated above 98.6degrees. The heart begins to pump more blood, bloodvessels dilate to accommodate the increased flow, andthe bundles of tiny capillaries are threading through theupper layers of skin are put into operation. The body’sblood is circulated closer to the skin’s surface, andexcess heat drains off into the cooler atmosphere. Atthe same time, water diffuses through the skin asperspiration. The skin handles about 90 percent of thebody’s heat dissipating function.

Heat Index/Heat DisordersHeat Possible Heat Disorders forIndex People in Higher Risk Groups130° or Heatstroke/sunstroke highlyHigher likely with continued exposure105° to Sunstroke, heat cramps or 130° heat exhaustion likely, with

heatstroke possible withprolonged exposure and / orphysical activity

90° to Sunstroke, heat cramps and105° heat exhaustion possible with

prolonged exposure and / orphysical activity

80° to Fatigue possible with90° prolonged exposure and / or

physical activity

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Sweating, by itself, does nothing to cool the body,unless the water is removed by evaporation–and highrelative humidity retards evaporation. The evaporationprocess itself works this way: the heat energy requiredto evaporate the sweat is extracted from the body,thereby cooling it. Under conditions of high temperature(above 90 degrees) and high relative humidity, the bodyis doing everything it can to maintain 98.6 degreesinside. The heart is pumping a torrent of blood throughdilated circulatory vessels; the sweat glands are pouringliquid–including essential dissolved chemicals, likesodium and chloride–onto the surface of the skin.

Too Much HeatHeat disorders generally have to do with a reduction orcollapse of the body’s ability to shed heat by circulatorychanges and sweating, or a chemical (salt) imbalancecaused by too much sweating. When heat gain exceedsthe level the body can remove, or when the bodycannot compensate for fluids and salt lost throughperspiration, the temperature of the body’s inner corebegins to rise, and heat-related illness may develop.

Ranging in severity, heat disorders share one commonfeature: the individual has overexposed or overexercised for his age and physical condition in theexisting thermal environment.

Sunburn, with its ultraviolet radiation burns, cansignificantly retard the skin’s ability to shed excess heat.

Studies indicate that, other things being equal, theseverity of heat disorders tend to increase withage–heat cramps in a 17-year old may be heatexhaustion in someone 40, and heat stroke in a personover 60.

Acclimatization has to do with adjusting sweat-saltconcentrations, among other things. The idea is to loseenough water to regulate body temperature, with theleast possible chemical disturbance.

Reprinted with permission of National Weather Service.

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10810597 99

138 144130

143 150142 149

122

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Heat Index(or ApparentTemperature)

RELATIVE HUMIDITY (%)

AIR

TE

MP

ER

ATU

RE

(°F

)

Heat Index ChartAir Temperature and Relative Humidity Versus Apparent Temperature

Heat Wave Cont’d

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130

120

110

100

90

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40

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10 20 30 40 50 60 70 80 90 100 110120130140150160

DEWPOINT TEMPERATURE (°F)

AIR

TE

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30 905040 1008060

70

% HUMIDITY

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°C)

25

1020

3040

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7080

90100

% HUMIDITY

To determine the dewpointtemperature: After measuring the airtemperature and relative humidity, usethe graph by drawing a horizontal linefrom the air temperature (Y-axis) to theappropriate relative humidity line. Thendraw a vertical line from thatintersection down to the dewpointtemperature (X-axis).

Dew Point

®

Charts based on:

td - ta17.5 –––––––––(td + 240.97)H =100«

where H = relative humidity (%)td = dewpoint temperature (°C)ta = air temperature (°C)

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Relative Humidity (%RH)Temperature Lithium Potassium Magnesium

°C Chloride Acetate Chloride0 11.23 ± 0.54 33.66 ± 0.335 11.26 ± 0.47 33.60 ± 0.28

10 11.29 ± 0.41 23.28 ± 0.53 33.47 ± 0.2415 11.30 ± 0.35 23.40 ± 0.32 33.30 ± 0.2120 11.31 ± 0.31 23.11 ± 0.25 33.07 ± 0.1825 11.30 ± 0.27 22.51 ± 0.32 32.78 ± 0.1630 11.28 ± 0.24 21.61 ± 0.53 32.44 ± 0.1435 11.25 ± 0.22 32.05 ± 0.1340 11.21 ± 0.21 31.60 ± 0.1345 11.16 ± 0.21 31.10 ± 0.1350 11.10 ± 0.22 30.54 ± 0.1355 11.03 ± 0.23 29.93 ± 0.1660 10.95 ± 0.26 29.26 ± 0.1865 10.86 ± 0.29 28.54 ± 0.2170 10.75 ± 0.33 27.77 ± 0.2575 10.64 ± 0.38 26.94 ± 0.2980 10.51 ± 0.44 26.05 ± 0.3485 10.38 ± 0.51 25.11 ± 0.3990 10.23 ± 0.59 24.12 ± 0.4695 10.07 ± 0.67 23.07 ± 0.52

100 9.90 ± 0.77 21.97 ± 0.60

Saturated Salt SolutionsA very convenient method tocalibrate humidity sensors is the useof saturated salt solutions. At anytemperature, the concentration of asaturated solution is fixed and doesnot have to be determined. Byproviding excess solute, the solutionwill remain saturated even in thepresence of modest moisturesources and sinks. When the soluteis a solid in the pure phase, it is easyto determine that there is saturation.

The saturated salt solution, made upas a slushy mixture with distilledwater and chemically pure salt, isenclosed in a sealed metal or a glasschamber. Wexler and Hasegawameasured the humidity in theatmosphere above eight saturatedsalt solutions for ambienttemperatures 0 to 50°C using a dew-point hygrometer. Later, Greenspancompiled, from the literature, data on28 saturated salt solutions to coverthe entire range of relative humidity.Using a data base from 21 separateinvestigations comprising 1106individual measurements, fits weremade by the method of least squaresto regular polynomial equations toobtain the “best” value of relativehumidity in air as a function oftemperature. These values aresummarized in the table shown.

Equilibrium ReIative HumiditySaturated SaIt Solutions

Relative Humidity (%RH)Temperature Potassium Magnesium Sodium Potassium Potassium Potassium

°C Carbonate Nitrate Chloride Chloride Nitrate Sulfate0 43.13 ± 0.66 60.35 ± 0.55 75.51 ± 0.34 88.61 ± 0.53 96.33 ± 2.9 98.77 ± 1.15 43.13 ± 0.50 58.86 ± 0.43 75.65 ± 0.27 87.67 ± 0.45 96.27 ± 2.1 98.48 ± 0.9110 43.14 ± 0.39 57.36 ± 0.33 75.67 ± 0.22 86.77 ± 0.39 95.96 ± 1.4 98.18 ± 0.7615 43.15 ± 0.33 55.87 ± 0.27 75.61 ± 0.18 85.92 ± 0.33 95.41 ± 0.96 97.89 ± 0.6320 43.16 ± 0.33 54.38 ± 0.23 75.47 ± 0.14 85.11 ± 0.29 94.62 ± 0.66 97.59 ± 0.5325 43.16 ± 0.39 52.89 ± 0.22 75.29 ± 0.12 84.34 ± 0.26 93.58 ± 0.55 97.30 ± 0.4530 43.17 ± 0.50 51.40 ± 0.24 75.09 ± 0.11 83.62 ± 0.25 92.31 ± 0.60 97.00 ± 0.4035 49.91 ± 0.29 74.87 ± 0.12 82.95 ± 0.25 90.79 ± 0.83 96.71 ± 0.3840 48.42 ± 0.37 74.68 ± 0.13 82.32 ± 0.25 89.03 ± 1.2 96.41 ± 0.3845 46.93 ± 0.47 74.52 ± 0.16 81.74 ± 0.28 87.03 ± 1.8 96.12 ± 0.4050 45.44 ± 0.60 74.43 ± 0.19 81.20 ± 0.31 84.78 ± 2.5 95.82 ± 0.4555 74.41 ± 0.24 80.70 ± 0.3560 74.50 ± 0.30 80.25 ± 0.4165 74.71 ± 0.37 79.85 ± 0.4870 75.06 ± 0.45 79.49 ± 0.5775 75.58 ± 0.55 79.17 ± 0.6680 76.29 ± 0.65 78.90 ± 0.7785 78.68 ± 0.8990 78.50 ± 1.095100

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Z

A two-wire transmitter is an idealsolution for many remotetemperature measurementapplications. Transmitters havedefinite advantages overconventional temperaturemeasuring devices, but must beselected with caution in order toavoid “ground loop” problems.

PURPOSEIn many cases, the temperature of aremote process must be monitored.Common temperature sensingdevices such as thermocouples andRTD’s produce very small “signals.”These sensors can be connected toa two-wire transmitter that willamplify and condition the smallsignal. Once conditioned to a usablelevel, this signal can be transmittedthrough ordinary copper wire andused to drive other equipment suchas meters, dataloggers, chartrecorders, computers or controllers.

OPERATIONA two-wire transmitter draws currentfrom a remote dc power supply inproportion to its sensor input. Theactual signal is transmitted as achange in the power supply current.

Specifically, a thermocouple inputtransmitter will draw 4 mA of currentfrom a dc power supply whenmeasuring the lowest temperatureof the process. Then, as thetemperature rises, the two-wiretransmitter will draw proportionallymore current, until it reaches 20 mA.This 20 mA signal corresponds tothe thermocouple’s highest sensedtemperature. The transmitter’sinternal signal-conditioning circuitry(powered by a portion of the 4-20 mA current) determines thetemperature range that the outputcurrent signal will represent.

Physically, only two copper wiresare necessary to connect thetransmitter output signal in a seriescircuit with the remote power supplyand the process equipment. This ismade possible since the signal andthe power supply line are combined(one circuit serves a dual function).

ADVANTAGESTwo-wire transmitters offernumerous advantages over themore traditional ways of measuringtemperature.

1.ac power is not needed at theremote location to operate a two-wire transmitter. Since transmittersare powered by a low level 4-20 mAoutput current signal, no additionalpower has to be supplied at theremote location. In addition, theusual 24 Vdc signal necessary foroperation is standard in plants thathave large amounts ofinstrumentation.

2.Electrical noise and signaldegradation are not a problem fortwo-wire transmitter users. Thetransmitter's current output signallends itself to a high immunity whenit comes to ambient electrical noise.Any noise that does appear in theoutput current is usually eliminatedby the common-mode rejection ofthe receiving device. In addition, thecurrent output signal will not change(diminish) with distance as mostvoltage signals do.

3.Wire costs drop significantlywhen using two-wiretransmitters. Low voltage signalsproduced by thermocouples almostalways require the use of shieldedcable when they are sent anysignificant distance. Ambientelectrical noise from arcing electricalrelays, motors and ac power linescan raise havoc with these signalsthat are transmitted in anunshielded cable. In addition,expensive, heavy gage wire is ofteninstalled in applications that call forlong cable runs (since it reduceserrors from signal voltage dropscaused by line resistance).

Ordinary copper wire can be used toconnect all the pertinent equipment ina two-wire transmitter system. The4-20 mA current output signal isrelatively immune to ambient electricalnoise and is not degraded by longdistance transmission, even over asmall diameter wire. Adding atwo-wire transmitter to a systemeliminates the problem of having toprovide long runs of costly wire and anextensive amount of shielding.

GROUND LOOP PROBLEMSIf a grounding rod was driven into theearth at two different points and avoltmeter was connected betweenthem, a voltage difference would bedetected between the two. Thisdifference in potential exists between

practically any two points along theearth’s surface. When one tries tomeasure a process that is at a remotelocation, this voltage difference willinduce an error current along the line,which is referred to as a “ground loop”signal. Its result will be an error at thedisplay.

To prevent “ground loop” errors of thistype, select an isolating two-wiretransmitter for your system. This typeof transmitter will optoelectronicallyisolate the sensor signal from theoutput current loop. This will allow theuser to ground both the sensor andone side of the current loop.

TRANSMITTER FEATURESTransmitters provide a two-wire outputwith the same wiring used for powerand output. The load resistance isconnected in series with a dc powersupply, and the current drawn fromthe supply is a 4-20 mA or outputsignal which is proportional to theinput signal.

Two-wire transmission permits remotemounting of the transmitter near thesensor to minimize the effects of noiseand signal degradation to which lowlevel sensor outputs are susceptible.

A rugged metal enclosure, suitable forfield mounting, offers environmentalprotection and screw terminal inputand output connections. Thisenclosure may be either surface orstandard relay track mounted.

Most two-wire transmitters arelinearized to the voltage signalproduced by the thermocouple orRTD, although there are new modelsnow available that are linearized to theactual temperature.

The two-wire transmitters convert thethermocouple or RTD signal to a 4-20 mA output signal. Some modelswill convert to an RS-232C output.Transmitters are available with dipswitch selection for severalthermocouple types per model, aswell as thermocouple and RTDselection on a single model. Two-wiretransmitters are available in eitherisolating or non-isolating models, andthey also feature output rangingadjustments with zero and spanadjustments over 80 to 100%(depending on model) of the sensorrange.

Two-Wire TransmittersFor Temperature Applications

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HILO

GNDAC POWER

SIGNAL

N

Technical InformationHow to Use Ferrite Cores with Instrumentation

Omega’s policy is to make running changes, not model changes, whenever an improvement is possible. This affords our customers the latest in technology and engineering.

Ferrite Beads supplied standardwith all DP40 and DP25 meters.

OMEGA® Panel Meters and Controllers1) OMEGA® Panel Meters and Controllers are intended for installation in

metal panels which should be connected to Earth Ground. (Standardrack panels are available from OMEGA Engineering. In environments with extreme electromagnetic radiation, shielded EMI cabinets offer additional protection.)

2) NEVER run signal wires and power in the same conduit.

3) Whenever electromagnetic compatibility is an issue, always use SHIELDED CABLES for all inputs and outputs. (A vast selection of shielded signal cable is available from OMEGA Engineering.) Connect the shield to the analog signal ground if appropriate or to earth ground.

4) Install one (or more) FERRITE BEADS on each signal input wire close to the meter.

Patent applications pending in various countries

OMEGA’s thermocouple and RTD connectors with built-in nickel-zinc ferrite cores are used where it is desired to suppress electro-magnetic,interference commonly known as EMI. Suppression of EMI has become a major concern in the instrumentation and control field. It is particularly important in handling and transmitting electronic data, as well as signalsfrom transducers, such as thermocouples, thermistors and RTD’s. This is because lead wires, extension wires, and signal wires often actas antennae. OMEGA offers a family of nickel-zinc ferrites in our newOMEGA® ferrite connectors. This allows the user to reduce the “antennaeffect”, which allows undesired signals to enter the instrumentation and controls.

Ferrite Connectors

The effectiveness of any ferrite core is based upon the material selection,number of wire turns around the core, and overall wire length. OMEGA’s ferrite connectors listed here have been developed for a multitude of general applications. The use of additional ferrite cores, as well as a specific selection of ferrite material, will provide a significant improvementin EMI suppression. While the OMEGA® ferrite connectors are designedfor a multitude of applications, the amount of EMI suppression will varyfrom application to application.

Please consult the factory for those applications where the standard OMEGA’s ferrite connectors may not be sufficient.

Note: Built-in ferrite cores are available in male miniature connectors andboth male and female standard size connectors.

Z-106

Z

Electromagnetic Compatibility

Electromagnetic Compatibility (EMC)may be a new term to some.However, it has been important formany years and actually predatesWorld War II. For several decades,three agencies have been drivingforces behind EMC: the U.S. Military;Europe’s Special InternationalCommittee on Radio Perturbations(Interference), CISPR; and the U.S.Federal CommunicationsCommissions (F.C.C.).

History

EMC first began to be an issue inthe military environment particularlyon broad ships where many types ofelectronic equipment had tosuccessfully operate in closeproximity to each other. In such anenvironment, communication,navigation and data processingelectronics all need to functionsimultaneously in the presence ofstrong radio frequency (RF) fields.Such RF fields are produced bytwo-way communicationsequipment, radar transmitters andmicroprocessor controlled devices.Added to this “mix,” on board amilitary ship is the presence ofordinance or explosives and aircraftfuel. In such an environment itbecomes transparently clear thateach device needs to beElectromagnetically Compatible withits environment and not be renderedinoperative or unsafe by thisenvironment. Also each deviceadded to this milieu must notunnecessarily or unintentionallycontribute spurious emissions thatdo not perform any particularfunction. From the preceding, theorigin of the two major aspects ofEMC, emissions and immunity, canbe seen.

Due to the global proliferation ofelectronic devices in non-militaryliving, it is becoming increasinglyimportant that EMC be maintained incivilian settings as well. Residentialand commercial environments maycontain dozens of appliances thatare controlled by microprocessors,i.e., kitchen stoves, video cassetterecorders, TV’s, breadmakers,personal computers, etc. Allelectronic devices utilizingmicroprocessor technologygenerate radio frequencies.

For example, a 100 MHz computercontains an electronic clock thatsteps the microprocessor through itsprogram. In this case, the clockfrequency falls within the frequencyspectrum allocated in the U.S. forFM radio broadcasting. Ifprecautions were not taken by PCmanufacturers, interference tonearby radio receivers would result.Harmonics or multiples of thisfrequency could, if not subdued,cause interference to other radioreceivers; such as those used byemergency medical personnel andto television receivers. It is thereforeincumbent upon manufacturers ofdigital electronic devices toguarantee their products will not beincompatible with or a nuisance toother electronic devices.

EMC and the USA

Because of the proliferation ofInformation Technology Equipment(ITE) and other microprocessor-controlled electronic equipment, inthe 1970’s the F.C.C. (as theauthority having jurisdiction in theU.S.) implemented limits on RFemissions from digital devices.Digital devices that are intended tobe used in residential environmentsare classified as Class “B” devices.All such Class “B” devices mustcomply with limits set forth in part 15of the F.C.C. rules for radiated and

conducted emissions. Before Class“B” devices may be sold in the U.S.,it must conform to the requirementsof the F.C.C. rules. Currently thereare no U.S. requirements forimmunity testing. Products destinedfor use in the U.S. industrial,scientific and medical fields have, tothis point, been exempt fromcompliance with these limits. Suchdevices are classified as Class “A”devices and may not be used inresidential environments.

EMC and the European Union

Products sold in the EuropeanUnion must carry the “CE” mark thatconstitutes a declaration by themanufacturer of the products’compliance with all applicableHarmonized Directives andStandards. Electronic devices aresubject to EMC Directive,89/392/EEC. Article 4 of thisdocument states: “Theapparatus...shall be so constructedthat (a) the EMC disturbance itgenerates does not exceed a levelallowing radio andtelecommunications equipment andother apparatus to operate asintended; (b) the apparatus has anadequate level of intrinsic immunityof EMC disturbance to enable it tooperate as intended.” Clearly,complying with the essentialrequirements of the European EMC

From analab1.com™ On-Line Publications

Open Area Test Site (O.A.T.S.). Used for 3- and 10-meter testing. It is F.C.C. listedand NVLAP accredited. In addition, the site was assessed by ACEMARK Europe,LTD which is recognized by numerous European competent bodies.

Z-107

Directive requires evaluation of aproduct’s emission and immunitycharacteristics. Notably, productsused in commercial, light industrialand heavy industrial environmentsare not exempt from compliance.

The Intrinsic Immunity requirementdictates that an electronic apparatusbe so constructed that itsperformance will not be degradedby its normal electromagneticenvironment. For example, aconsumer in Europe has a right toexpect that the digital securitysystem monitoring his home will notmalfunction if a nearby ambulancecrew talks to their local dispatchervia two-way radio communicationsequipment. The directive impliesthat manufacturers will designproducts to possess immunity notonly to radiated RF fields, but toother electromagnetic phenomenaas well.

Specific immunity tests are itemizedby generic and product-specificEuropean norms or standards.Minimally, this means that adevice’s performance will not beadversely effected by: (1) RF fields,such as radio and TV broadcaststations, and licensed two-way radioequipment; (2) ElectrostaticDischarge events (ESD); (3) andElectrical Fast Transients (EFT).Testing of products for immunity insimulation of real-worldenvironments allows manufacturersto demonstrate compliance withArticle 4, clause (b) of the EMCDirective. Additional immunitytesting is required by certain specificstandards and the new 1997generic immunity standard. Theseadditional tests include: ConductedRF Immunity; Surge Immunity;Power Frequency Magnetic FieldsImmunity; Voltage Dips andInterrupts Immunity; and Pulsed RFFields Immunity.

CE Conformity

Conformity to the essentialrequirements of the EMC Directivemust be declared by themanufacturer or his authorizedrepresentative. This is done byissuing a document called a“Declaration of Conformity” (DOC).It is the manufacturer’sresponsibility to procure and

Biconical Antenna

Anechoic Chamber

maintain technical evidencesupporting all claims of product“conformity”. This supportingevidence is assembled in aTechnical Construction File (TCF).A TCF will exist for each productsold in the European Union.Verification of compliance (testing)may be performed by themanufacturer or a third-party testhouse. In all cases though, testsmust be performed in harmony withInternational IEC Test Standards.Results of EMC testing, such as theTest Report issued by a testinglaboratory, shall be included inthe TCF.

A product that meets therequirements of an appropriate“product specific standard,” or in lieuof a “product specific standard” thegeneric standard, is presumed tomeet the essential requirements ofthe EMC Directive. In addition to theEMC Directive, other directives maybe applicable to an electronicdevice. Conformity with allapplicable directives must beverified and documented. Having

met all requirements, the “CE” markmay then be applied. For a period often years after being placed on theEuropean Market, the supportingtechnical documentation (TCF) mustbe kept on file and be accessible byan authorized representative withinthe European Union.

Benefits

Compliance with the EuropeanUnion’s EMC Directive leads toincreasingly robust products,improvements in quality andincreased customer satisfaction. Forexample, ESD (electrostaticdischarge) Immunity Testing quicklyreveals any latent vulnerability aproduct might have to suchstandards and promotes correctivemeasures that render the productimmune to such real worldoccurrences. The result is improvedcustomer satisfaction realized fromreliable, solid products that provideyears of trouble free service.

C.R.S. 26-Jan-98

OMEGA’s innovative Low NoiseThermocouple System provides stable and accurate temperaturemeasurements by neutralizing theeffects of ambient electrical noise. Thislow cost and versatile system is used formeasuring temperatures of sensitivecircuits and equipment where preciseand stable readings are critical. It is alsoused throughout industry as a noiserejecting standard.

The low noise thermocouple systemconsists of three interrelated elements:a probe assembly, a connector andthermocouple wire. Each of these three components has distinct andcoordinated noise neutralizing featuresand together they provide a path fordiverting electrical noise. The system,which uses universal two-terminalconnections, shunts noise signals and preserves the integrity of thetemperature-measuring circuit (see Figure 1).

ELECTRICAL NOISENEUTRALIZEDElectrical noise, typically generated bypower equipment, rotating machinery,line processing conveyors, mobile units,welding machines and cleaningappliances, introduces spurious signalsthat destabilize sensitive temperaturemeasurements. The system’s uniquepositive ground path, from thethermocouple probe to thetemperature indicating instrument,fully neutralizes the effects of electrical noise. Precisetemperature control for dataacquisition, data logging andcomputer interface circuits is now possible with the addedassurance that noise is beingrejected.

BALANCED SYSTEMELEMENTSThe thermocouple system’sthree building blocks –probe, connector and wire – are integrated into abalanced and easilyassembled unit. Theprobe and connector areavailable in bothstandard and miniatureconfigurations (see Figure 2).

(1) The thermocouple probe is shapedto ease handling and improve viewing of the test object. Probe types areinterchangeable to suit manyapplications. The probe sheath (outer jacket) connects to a groundthrough an internal ground strap link.

(2) The connector, which joins the probe and thermocouple wire, is astandard two-terminal quick disconnecttype (miniature or standard size). The external metal ground strap,attached to the connector, provides the continued noise shunting circuit and adds mechanical strength to the assembly.

(3) The twisted/shielded thermocouplewire contains an integral drain wirewhich provides the noise grounding linkbetween the probe assembly and themeasuring instrument.

CONVENIENT FEATURESThe probe assembly is designed toease handling, improve mechanicalintegrity and allow the user to view thesubject under test without obstruction. A 30 degree profile, found only inOMEGA’s patented design, allows forimproved user performance (see Figure 2). The probe assemblies arecolor coded to identify thermocouplematerials and a full selection of probe sheath diameters and lengths are available.

Probe lengths are 6", 12", 18", and 24";diameters are from .040" to .250". Theprobe sheath is 304SS or Inconel.

The connector provides continuity of ground from the probe to thethermocouple wire through an externalground strap. Polarized connector pins allow for quick connection ordisconnection to the probe assembly.Connectors include removable write-onpads. This feature, unique in theindustry, allows positive identification of thermocouple assemblies in multiplemeasurement applications.

PROBLEM SOLVERThe user often cannot forecast whatelectrical noise sources will be presentduring temperature readings. Typicaltemperature measurements areperformed in electrically noisyenvironments.

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Z-108

Low NoiseThermocoupleSystem

U.S. and ForeignPatents

The “Noise Is Off” withThis Thermocouple System

Z-109

In a laboratory, where processes arebeing controlled at precise temperaturetransition points, electrical noise may be introduced from sources such asmixers, ovens, heating elements andpower supplies. Grounding of this noiseis essential for precise temperaturesensing. This thermocouple systemgrounds the destabilizing noise signals.

Precise control of solder bathtemperatures, during an automated flow soldering process, is required toensure that proper soldering takesplace and that no damage occurs tosensitive components on a printedcircuit board. Typically, the thermalsensing system is in the presence ofequipment which generates electricalnoise such as motors and weldingequipment. The system’s unique andpositive noise grounding pathneutralizes the effects of generated noise.

In high noise applications such asenvironmental control, air conditioning,heat treating and foundry operations,noise neutralization during criticaltemperature measurements is requiredfor accurate and stable control. Byshunting electrical noise harmlessly to ground, the OMEGA® thermocouplesystem provides the required stablereadings.

The noisy environments encounteredin industrial, mobile, field and

laboratory applications are no match for this easily assembled and handy-to-use system.

Figure 2. Balanced system elements include: thermocouple probe, connector, and thermocouple wire. The thermocouple probe has a 30° profile, an exclusive OMEGA feature, and comes with the mating female connector and cable clamp

SM

CONNECTOR

METAL STRAP

(1)(2)

(3)

INTERNALDRAIN WIRE

TWISTED SHIELDED

T/C WIREPROBE

Figure 1. Continuous ground from probe to test instrument

To order probesStandard quick disconnectprobes and miniature quickdisconnect probes are soldin Section A of this catalog.

To order connectorsStandard connectors andminiature connectors aresold in Section G of thiscatalog.

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How Can I Control My Process Temperature Accuratelyand Reliably?

To accurately control process temperature withoutextensive operator involvement, a temperature controlsystem relies upon a controller, which accepts atemperature sensor such as a thermocouple or RTD asinput. It compares the actual temperature to the desiredcontrol temperature, or setpoint, and provides an outputto a control element.

The controller is one part of the entire control system,and the whole system should be analyzed in selectingthe proper controller. The following items should beconsidered when selecting a controller:

1. Type of input sensor (thermocouple, RTD) and temperature range

2. Type of output required (electromechanical relay, SSR, analog output)

3 Control algorithm needed (on/off, proportional, PID)

4 Number and type of outputs (heat, cool, alarm, limit)

What Are the Different Types of Controllers, and HowDo They Work?

There are three basic types of controllers: on-off,proportional and PID. Depending upon the system to becontrolled, the operator will be able to use one type oranother to control the process.

On/Off

An on-off controller is the simplest form of temperaturecontrol device. The output from the device is either onor off, with no middle state. An on-off controller willswitch the output only when the temperature crossesthe setpoint. For heating control, the output is on whenthe temperature is below the setpoint, and off abovesetpoint.

Since the temperature crosses the setpoint to changethe output state, the process temperature will be cyclingcontinually, going from below setpoint to above, andback below. In cases where this cycling occurs rapidly,and to prevent damage to contactors and valves, an on-off differential, or “hysteresis,“ is added to the controlleroperations. This differential requires that thetemperature exceed setpoint by a certain amountbefore the output will turn off or on again. On-offdifferential prevents the output from “chattering” (that is,engaging in fast, continual switching if thetemperature’s cycling above and below the setpointoccurs very rapidly).

On-off control is usually used where a precise control isnot necessary, in systems which cannot handle theenergy’s being turned on and off frequently, where themass of the system is so great that temperatureschange extremely slowly, or for a temperature alarm.

One special type of on-off control used for alarm is alimit controller. This controller uses a latching relay,which must be manually reset, and is used to shut downa process when a certain temperature is reached.

Heater

Temperature

ON ON ON ON

OFF OFF OFF OFF

Setpoint

Time

ON/Off Temperature Control Action

On-OffDifferential(Deadband)

Introduction To TemperatureControllers

The Miniature CN77000 is a full featured microprocessor-based controller in a 1/16 DIN package.

Introduction To TemperatureControllers

Time Proportional 4-20 mAProportional

Percent On Time Off Time Temp Output PercentOn Seconds Seconds (ºF) Level Output

0.0 0.0 20.0 over 540 4 mA 0.00.0 0.0 20.0 540.0 4 mA 0.0

12.5 2.5 17.5 530.0 6 mA 12.525.0 5.0 15.0 520.0 8 mA 25.037.5 7.5 12.5 510.0 10 mA 37.550.0 10.0 10.0 500.0 12 mA 50.062.5 12.5 7.5 490.0 14 mA 62.575.0 15.0 5.0 480.0 16 mA 75.087.5 17.5 2.5 470.0 18 mA 87.5

100.0 20.0 0.0 460.0 20 mA 100.0100.0 20.0 0.0 under 460 20 mA 100.0

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Systems that are subject to wide temperature cyclingwill also need proportional controllers. Depending uponthe process and the precision required, either a simpleproportional control or one with PID may be required.

Processes with long time lags and large maximum rateof rise (e.g., a heat exchanger), require wideproportional bands to eliminate oscillation. The wideband can result in large offsets with changes in theload. To eliminate these offsets, automatic reset(integral) can be used. Derivative (rate) action can beused on processes with long time delays, to speedrecovery after a process disturbance.

Proportional

Proportional controls are designed to eliminate thecycling associated with on-off control. A proportionalcontroller decreases the average power being suppliedto the heater as the temperature approaches setpoint.This has the effect of slowing down the heater, so that itwill not overshoot the setpoint but will approach thesetpoint and maintain a stable temperature. Thisproportioning action can be accomplished by turning theoutput on and off for short intervals. This “timeproportioning “ varies the ratio of ‘on’ time to ‘off‘ time tocontrol the temperature. The proportioning actionoccurs within a “proportional band” around the setpointtemperature. Outside this band, the controller functionsas an on-off unit, with the output either fully on (belowthe band) or fully off (above the band). However, withinthe band, the output is turned on and off in the ratio ofthe measurement difference from the setpoint. At thesetpoint (the midpoint of the proportional band), theoutput on:off ratio is 1:1; that is, the on-time and off-timeare equal. If the temperature is further from the setpoint,the on- and off-times vary in proportion to the

temperature difference. If the temperature is belowsetpoint, the output will be on longer; if the temperatureis too high, the output will be off longer.

The proportional band is usually expressed as apercent of full scale, or degrees. It may also be referredto as gain, which is the reciprocal of the band. Note,that in time proportioning control, full power is applied tothe heater, but is cycled on and off, so the average timeis varied. In most units, the cycle time and/orproportional band are adjustable, so that the controllermay better match a particular process.

In addition to electromechanical and solid state relayoutputs, proportional controllers are also available withproportional analog outputs, such as 4 to 20 mA or 0 to5 Vdc. With these outputs, the actual output level isvaried, rather than the on and off times, as with a relayoutput controller.

One of the advantages of proportional control issimplicity of operation. It may require an operator tomake a small adjustment (manual reset) to bring thetemperature to setpoint on initial startup, or if theprocess conditions change significantly.

Proportional BandwithExample: heatingSetpoint: 500˚FProportional Band: 80˚F

(±40˚F)

Repetitive

20 sec. CycleTime

15 Sec. On 5 Off

Time Proportioning at 75% Output Level

The CN2010 controller features ramp and soak, the abilityto control temperature over time.

Introduction To Temperature Controllers Cont’d

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The output from the controller may take one of severalforms. The most common forms are time proportionaland analog proportional. A time proportional outputapplies power to the load for a percentage of a fixedcycle time. For example, with a 10 second cycle time, ifthe controller output were set for 60%, the relay wouldbe energized (closed, power applied) for 6 seconds,and de-energized (open, no power applied) for 4seconds. Time proportional outputs are available inthree different forms: electromechanical relay, triac orac solid state relay, or a dc voltage pulse (to drive anexternal solid state relay). The electromechanical relayis generally the most economical type, and is usuallychosen on systems with cycle times greater than 10seconds, and relatively small loads.

An ac solid state relay or dc voltage pulse are chosenfor reliability, since they contain no moving parts.Recommended for processes requiring short cycletimes, they need an additional relay, external to thecontroller, to handle the typical load required by aheating element. These external solid state relays areusually used with an ac control signal for ac solid staterelay output controllers, or with a dc control signal for dcvoltage pulse output controllers.

An analog proportional output is usually an analogvoltage (0 to 5 Vdc) or current (4 to 20 mA). The outputlevel from this output type is also set by the controller; ifthe output were set at 60%, the output level would be60% of 5 V, or 3 V. With a 4 to 20 mA output (a 16 mAspan), 60% is equal to (0.6 x 16) + 4, or 13.6 mA.These controllers are usually used with proportioningvalves or power controllers.

What Should I Consider When Selecting a Controller forMy Application?

When you choose a controller, the main considerationsinclude the precision of control that is necessary, andhow difficult the process is to control. For easiest tuningand lowest initial cost, the simplest controller which willproduce the desired results should be selected.

Simple processes with a well matched heater (not over-or undersized) and without rapid cycling can possiblyuse on-off controllers. For those systems subject tocycling, or with an unmatched heater (either over- orundersized), a proportional controller is needed.

There are also other features to consider whenselecting a controller. These include auto- or self-tuning, where the instrument will automatically calculatethe proper proportional band, rate and reset values forprecise control; serial communications, where the unitcan “talk” to a host computer for data storage, analysis,and tuning; alarms, that can be latching (manual reset)or non-latching (automatic reset), set to trigger on highor low process temperatures or if a deviation fromsetpoint is observed; timers/event indicators which canmark elapsed time or the end/beginning of an event. Inaddition, relay or triac output units can be used withexternal switches, such as SSR solid state relays ormagnetic contactors, in order to switch large loads up to75 A.

PID The third controller type provides proportional withintegral and derivative control, or PID. This controllercombines proportional control with two additionaladjustments, which helps the unit automaticallycompensate for changes in the system. Theseadjustments, integral and derivative, are expressed in

time-based units; they are also referred to by theirreciprocals, RESET and RATE, respectively.

The proportional, integral and derivative terms must beindividually adjusted or “tuned” to a particular system,using a “trial and error” method. It provides the mostaccurate and stable control of the three controller types,and is best used in systems which have a relativelysmall mass, those which react quickly to changes inenergy added to the process. It is recommended insystems where the load changes often, and thecontroller is expected to compensate automatically dueto frequent changes in setpoint, the amount of energyavailable, or the mass to be controlled.

What Do Rate and Reset Do, and How Do They Work?

Rate and reset are methods used by controllers tocompensate for offsets and shifts in temperature. Whenusing a proportional controller, it is very rare that theheat input to maintain the setpoint temperature will be50%; the temperature will either increase or decreasefrom the setpoint, until a stable temperature is obtained.The difference between this stable temperature and thesetpoint is called offset. This offset can becompensated for manually or automatically. Usingmanual reset, the user will shift the proportional band sothat the process will stabilize at the setpointtemperature. Automatic reset, also known as integral,will integrate the deviation signal with respect to time,and the integral is summed with the deviation signal toshift the proportional band. The output power is thusautomatically increased or decreased to bring the

Time

Process with Temperature Offset

OffsetSPPB

Tem

p.

®

process temperature back to setpoint,

The rate or derivative function provides the controllerwith the ability to shift the proportional band, tocompensate for rapidly changing temperature. Theamount of shift is proportional to the rate of temperaturechange.

A PID, or three-mode controller, combines theproportional, integral (reset) and derivative (rate)actions, and is usually required to control difficultprocesses. These controllers can also be made withtwo proportional outputs, one for heating and anotherfor cooling. This type of controller is required forprocesses which may require heat to start up, but thengenerate excess heat at some time during operation.

What are the Different Output Types That Are Availablefor Controllers?

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Temperature ControllersSelection Considerations

CONTROLLABILITY OF ELECTRIC HEATThe basic function of a controller is tocompare the actual temperature with itssetpoint and produce an output which willmaintain that setpoint.The controller is one part of the entirecontrol system, and the whole systemshould be analyzed in selecting theproper controller. The following itemsshould be considered when selecting acontroller.1. Type of input sensor (thermocouple,

RTD, card and temperature range).2. Placement of sensor3. Control algorithm needed (on/off,

proportional, PID, autotune PID)4. Type of output hardware required

(electromechanical relay, SSR, analogoutput signal)

5. Additional outputs or requirements ofsystem (display required oftemperature and/or setpoint, coolingoutputs, alarms, limit, computercommunication, etc.)

TYPE OF INPUTThe type of input sensor will depend onthe temperature range required, theresolution and accuracy of themeasurement required, and how andwhere the sensor is to be mounted.PLACEMENT OF THE SENSORThe correct placement of the sensingelement with respect to the work andheat source is of the utmost importancefor good control. If all three can belocated in close proximity, a high degreeof accuracy, up to the limit of thecontroller, is relatively easy to achieve.However, if the heat source is locatedsome distance from the work, widelydifferent accuracies can be obtained justby locating the sensing element atvarious places between the heater andthe work.Before selecting the location for thesensing element, determine whether theheat demand will be predominantlysteady or variable. If the heat demand isrelatively steady, placement of thesensing element near the heat sourcewill hold the temperature change at thework to a minimum.On the other hand, placing the sensingelement near the work, when heatdemand is variable, will enable it to morequickly sense a change in heatrequirements. However, because of theincrease in thermal lag between theheater and the sensing elements, moreovershoot and undershoot can occur,causing a greater spread betweenmaximum and minimum temperature.This spread can be reduced by selectinga PID controller.

CONTROL ALGORITHM (MODE)This refers to the method in which thecontroller attempts to restore systemtemperature to the desired level. The twomost common methods are two-position(on-off) and proportioning (throttling)controls.ON/OFF CONTROLOn/Off control has the simplest of controlmodes. It has a deadband (differential)expressed as a percentage of the inputspan. The setpoint is usually in thecenter of the deadband. Therefore, if theinput is 0-1000°F, the deadband is 5%and the setpoint is set at 500°F, theoutput will be full on when thetemperature is 495°F or below and willstay full on until the temperature reaches505°F, at which time the output will befull off. It will stay full off until thetemperature drops to 495°F.If the process has a fast rate ofresponse, the cycling between 495 and505°F will be fast. The faster the rate ofresponse of the process, the greater theovershoot and undershoot and the fasterthe cycling of the contactor when used asa final control element.On-off control is usually used where aprecise control is not necessary, forexample, in systems which cannothandle having the energy turned on andoff frequently, where the mass of thesystem is so great that the temperaturechanges extremely slowly, or for atemperature alarm.One special type of on-off control usedfor alarm is a limit controller. Thiscontroller uses a latching relay, whichmust be manually reset, and is used toshut down a process when a certaintemperature is reached.PROPORTIONALProportional controls are designed toeliminate the cycling associated with on-off control. A proportional controllerdecreases the average power beingsupplied to the heater as the temperatureapproaches setpoint. This has the effectof slowing down the heater so that it willnot overshoot the setpoint, but willapproach the setpoint and maintain astable temperature. This proportioningaction can be accomplished by turningthe output on and off for short intervals.This “time proportioning” varies the ratioof “on” time to “off ” time to control thetemperature.The time period between two successiveturn-ons is known as the “cycle time” or“duty cycle”. The proportioning actionoccurs within a “proportional band”around the setpoint temperature. Outsidethis band, the controller functions as anon-off unit, with the output either fully on(below the band) or fully off (above theband). However, within the band, the

output is turned on and off in the ratio ofthe measurement difference from thesetpoint. At the setpoint (the midpoint ofthe proportional band), the output on-offratio is 1:1 that is, the on-time and off-time are equal. If the temperature isfurther from the setpoint, the on- and off-times vary in proportion to thetemperature difference. If thetemperature is below setpoint, the outputwill be on longer. If the temperature is toohigh, the output will be off longer.

The proportional band is usuallyexpressed as a percentage of full inputrange scale, or in degrees. It may also bereferred to as gain, which is thereciprocal of the band. In many units, thecycle time and/or proportional bandwidthare adjustable, so that the controller maybe better matched to a particularprocess.Proportional controllers have a manualreset (trim) adjustment, which may beused to adjust for an offset between thesteady state temperature and thesetpoint.In addition to electromechanical and solidstate relay outputs, proportionalcontrollers are also available withproportional analog signal outputs, suchas 4 to 20 mA or 0 to 5 Vdc. With theseoutputs, the actual output level amplitudeis varied, rather than the proportion of onand off times.PROPORTIONAL PLUS INTEGRALPLUS DERIVATIVE CONTROL MODE(PID):This controller operates the same way aproportional controller does, except thatthe function of the trim adjustment isperformed automatically by the integralfunction (automatic reset). Thus, loadchanges are compensated forautomatically and the temperatureagrees with the setpoint under alloperating conditions. Offset is eliminated.

AboveTemp.

At SetPointTemp.

BelowTemp.

OnTime

OffTime

Figure 1: Proportional control

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Temperature ControllersSelection Considerations

The derivative function (rate action)compensates for load changes whichtake place rapidly. An example is atraveling belt oven where the product isfed intermittently. When the productenters the oven, there is a sharp rise inthe demand for heat, and when it stops,there is an excess of heat. Derivativeaction reduces the undershoot andovershoot of temperature under theseconditions and prevents bad product due

to over or under curing.PID control provides more accurate andstable control than on/off or proportionalcontroller types. It is best used insystems that have a relatively smallmass and which react quickly to changesin energy added to the process. It isrecommended in systems where the loadchanges often. The controller is expectedto automatically compensate the amountof energy available or the mass to becontrolled, due to frequent changes insetpoint.The proportional, integral and derivative

terms must be “tuned,” i.e., adjusted to aparticular process. This is done by trialand error. Some controllers calledAutotune controllers attempt to adjust thePID parameters automatically.TYPE OF CONTROL OUTPUTHARDWAREThe output hardware in a temperaturecontroller may take one of several forms.Deciding on the type of control hardwareto be used depends on the heater usedand power available, the controlalgorithm chosen, and the hardwareexternal to the controller available tohandle the heater load. The mostcommonly used controller outputhardware is as follows:Time Proportional or On/Off

1)Mechanical Relay2)Triac (ac solid state relay)3)dc Solid State Relay Driver (pulse)

Analog Proportional1) 4-20 mA dc2) 0-5 Vdc or 0-10 Vdc

A time proportional output applies powerto the load for a percentage of a fixedcycle time. For example, with a 10second cycle time, if the controller outputwere set for 60%, the relay would beenergized (closed, power applied) for 6seconds, and de-energized (open, nopower applied) for 4 seconds.The electromechanical relay is generallythe most economical output type, and isusually chosen on systems with cycletimes greater than 10 seconds andrelatively small loads.Choose an ac solid state relay or dcvoltage pulse to drive an external SSRwith reliability, since they contain nomoving parts. They are alsorecommended for processes requiringshort cycle times. External solid staterelays may require an ac or dc controlsignal.An amplitude proportional output isusually an analog voltage (0 to 5 Vdc) orcurrent (4 to 20 mA). The output levelfrom this output type is also set by thecontroller. If the output were set at 60%,the output level would be 60% of 5 V, or3 V. With a 4 to 20 mA output (a 16 mAspan), 60% is equal to (0.6 x 16) + 4, or13.6 mA. These controllers are usuallyused with SCR power controllers orproportioning valves.The power used by an electricalresistance heater will usually be given inwatts. The capacity of a relay is given inamps. A common formula to determinethe safe relay rating requirements is:W = V(A)(1.5) or A = W/(V)(1.5)Where A = relay rating in ampsW = heater capacity in wattsV = voltage used1.5 = safety factor

The types of hardware available, externalto the controller, to allow it to handle theload, are as follows:1) Mechanical Contactor2) ac controlled solid state relay 3) dc controlled solid state relay 4) Zero crossover SCR power controller5) Phase angle fired SCR power controllerMechanical contactors are externalrelays, which can be used when a higheramperage than can be handled by therelay in the controller is required, or forsome three-phase systems. They are notrecommended for cycle times shorterthan 15 seconds.Solid state relays have the advantageover mechanical contactors, in that theyhave no moving parts, and thus can beused with short cycle times. The shorterthe cycle time, the less dead lag and thebetter the control. The “switching” takesplace at the zero voltage crossover pointof the alternating current cycle; thus, noappreciable electrical noise is generated.An ac controlled solid state relay is usedwith either a mechanical relay or triacoutput from the controller, and isavailable for currents up to 90 amps atvoltages of up to 480 Vac. DC solid staterelays are used with dc solid state driver(pulse) outputs. The “turn on” signal canbe from 3 to 32 Vdc and models areavailable to control up to 90 amps at upto 480 Vac.Zero crossover SCR power controllersare used to control single or three-phasepower for even larger loads. They can beused for currents up to 200 amps at480 volts. A 4-20 mA dc control signal isusually required from the controller. Thezero crossover SCR power controllersconvert the analog output signal to a timeproportional signal with a cycle time ofabout two seconds or less, and alsoprovide switching at the zero crossoverpoint to avoid generating electrical noise.Phase angle SCR power controllers alsoare operated by a 4-20 mA dc controlleroutput. Power to the load is controlled bygoverning the point of turn on (firing) ofeach half cycle of a full ac sine wave.This has the effect of varying the voltagewithin a single 0.0167 second period. Bycomparison, time proportional controllersvary the average power over the cycletime, usually more than 1 second, andoften more than 15 seconds. Phaseangle SCR’s are only recommended forlow mass heating elements such asinfrared lamps or hot wire heaters.

Rate SetProperly

Low RateSetting

SetPoint

Figure 2: Rate function compensates for rapidchanges.

SetPoint

Offset

Figure 3: Reset fuction eliminates offset.

®

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Temperature ControlTuning a PID (Three Mode) Controller

Tuning a temperature controller involves setting the proportional,integral, and derivative values to get the best possible control fora particular process. If the controller does not include an autotunealgorithm, or if the autotune algorithm does not provide adequatecontrol for the particular application, then the unit must be tunedusing trial and error.

The following is a tuning procedure for the OMEGA CN2000controller. It can be applied to other controllers as well. There areother tuning procedures which can also be used, but they all usea similar trial and error method. Note that if the controller uses amechanical relay (rather than a solid state relay), a longer cycletime (20 seconds) should be used when starting out.

The following definitions may be needed:

1) Cycle time - Also known as duty cycle; the total length of timefor the controller to complete one on/off cycle. Example: with a20 second cycle time, an on time of 10 seconds and an offtime of 10 seconds represents a 50 percent power output. Thecontroller will cycle on and off while within the proportionalband.

2) Proportional band - A temperature band expressed in % of fullscale or degrees within which the controller‘s proportioningaction takes place. The wider the proportional band, thegreater the area around the setpoint in which the proportionalaction takes place. This is sometimes referred to as gain,which is the reciprocal of proportional band.

3) Integral, also known as reset, is a function which adjusts theproportional bandwidth with respect to the setpoint tocompensate for offset (droop) from setpoint; that is, it adjuststhe controlled temperature to setpoint after the systemstabilizes.

4) Derivative, also known as rate, senses the rate of rise or fall ofsystem temperature and automatically adjusts the proportionalband to minimize overshoot or undershoot.

A PID (three mode) controller is capable of exceptional controlstability when properly tuned and used. The operator can achievethe fastest response time and smallest overshoot by followingthese instructions carefully. The information for tuning this threemode controller may be different from other controller tuningprocedures. Normally a SELF TUNE feature will eliminate theneed to use this manual tuning procedure for the primary output;however, adjustments to the SELF TUNE values may be made ifdesired.

After the controller is installed and wired:

1. Apply power to the controller.

2. Disable the control outputs if possible.

3. For time proportional primary output, set the cycle time. Enterthe following value:

CYCLE TIME 1

5 SEC (Only appears if output is a time proportional output. Asmaller cycle time may be required for systems with an extremelyfast response time.)

Then select the following parameters:

PR BAND 1 _______5% (PB)

RESET 1 _________0 R/M (TURNS OFF RESET FUNCTION)

RESET 2 _________0 R/M

RATE 1 __________0 MIN (TURNS OFF RATE FUNCTION)

RATE 2 __________0 MIN

NOTE

On units with dual three mode outputs, the primary andsecondary tuning parameters are independently set and must betuned separately. The procedure used in this section is for aHEATING primary output. A similar procedure may be used for aprimary COOLING output or a secondary COOLING output.

A. TUNING OUTPUTS FOR HEATING CONTROL

1. Enable the OUTPUT(S) and start the process.

2. The process should be run at a setpoint that will allow thetemperature to stabilize with heat input required.

3. With RATE and RESET turned OFF, the temperature willstabilize with a steady state deviation, or droop, between thesetpoint and the actual temperature. Carefully note whether ornot there are regular cycles or oscillations in this temperatureby observing the measurement on the display. (An oscillationmay be as long as 30 minutes.)

The tuning procedure is easier to follow if you use a recorderto monitor the process temperature.

Figure 1. Temperature Oscillations

PRIMARYSETPOINT

PRIMARYSETPOINT

PRIMARYSETPOINT

TE

MP.

TE

MP. TE

MP.

TIMEDivide PB by 2 ifyou observe this.

TIMEThis is close toperfect tuning.

TIMEMultiply PB by 2 ifyou observe this.

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Z

4. If there are no regular oscillations in the temperature, dividethe PB by 2 (see Figure 1). Allow the process to stabilizeand check for temperature oscillations. If there are still nooscillations, divide the PB by 2 again. Repeat until cycles oroscillations are obtained. Proceed to Step 5.

If oscillations are observed immediately, multiply the PB by2. Observe the resulting temperature for several minutes. Ifthe oscillations continue, increase the PB by factors of 2until the oscillations stop.

5. The PB is now very near its critical setting. Carefullyincrease or decrease the PB setting until cycles oroscillations just appear in the temperature recording.

If no oscillations occur in the process temperature even atthe minimum PB setting of 1%, skip Steps 6 through 11below and proceed to paragraph B.

6. Read the steady-state deviation, or droop, between setpointand actual temperature with the “critical” PB setting youhave achieved. (Because the temperature is cycling a bit,use the average temperature.)

7 Measure the oscillation time, in minutes, betweenneighboring peaks or valleys (see Figure 2). This is mosteasily accomplished with a chart recorder, but ameasurement can be read at one minute intervals to obtainthe timing.

8. Now, increase the PB setting until the temperaturedeviation, or droop, increases 65%.

The desired final temperature deviation can be calculated bymultiplying the initial temperature deviation achieved withthe CRITICAL PB setting by 1.65 (see Figure 3) or by use ofthe convenient Nomogram I (see Figure 4). Try several trial-and-error settings of the PB control until the desired finaltemperature deviation is achieved.

9. You have now completed all the measurements necessaryto obtain optimum performance from the Controller. Onlytwo more adjustments are required - RATE and RESET.

10.Using the oscillation time measured in Step 7, calculate thevalue for RESET in repeats per minutes as follows:RESET = 8 x 1__ __

5 TO

Where TO = Oscillation Time in Minutes.OR Use Nomogram II (see Figure 5):

Enter the value for RESET 1.

11.Again using the oscillation time measured in Step 7,calculate the value for RATE in minutes as follows:RESET = TO__

10

Where TO = Oscillation TimeOR Use Nomogram III (see Figure 6)

Enter this value for Rate 1.

12.If overshoot occurred, it can be eliminated by decreasing theRESET time. When changes are made in the RESET value,a corresponding change should also be made in the RATEadjustment so that the RATE value is equal to:RATE = 1______________

6 x Reset Value

i.e., if reset = 2 R/M, theRATE = 0.08 min.

13.Several setpoint changes and consequent RESET andRATE time adjustments may be required to obtain theproper balance between “RESPONSE TIME” to a systemupset and “SETTLING TIME.” In general, fast response isaccompanied by larger overshoot and consequently shortertime for the process to “SETTLE OUT.” Conversely, if theresponse is slower, the process tends to slide into the finalvalue with little or no overshoot. The requirements of thesystem dictate which action is desired.

14.When satisfactory tuning has been achieved, the cycle timeshould be increased to save contactor life (applies to unitswith time proportioning outputs only (TPRI)). Increase thecycle time as much as possible without causing oscillationsin the measurement due to load cycling.

15.Proceed to Section C.

STARTUP

DECREASEPB

PRIMARY SETPOINT

INCREASEPB

CRITICALPB

TIME

TE

MP.

MEASURE THIS TEMP

MEASURE THISTIME

PRIMARY SETPOINT

CRITICAL PBTIME WITH PB

DEVIATIONTEMP WITH PB

1.65 · TEMPDEVIATION WITHPB

TIMESTARTUP

TE

MP

EXAMPLE3° DEVIATION WITHPB SET PB TOOBTAIN 5° FINALDEVIATION

1 2 3 4 5 10

2 3 5 10 15 20 30 40 50

15 20 30 40 50 70 100

150100

FINAL TEMPERATURE DEVIATION = 1.65DEVIATION WITH CRITICAL PBC. SETTING.

TEMPERATURE DEVIATION WITHCRITICAL PBC. SETTING

TEMPERATURE CYCLE TIME IN MINUTES

CORRECT RESET SETTING IN REPEATS PER MINUTE

0.1

20 10

0.2 0.3

5 3 2

1

1

2 3

0.50 0.30 0.20

10 20

0.10 0.05

30

0.03 0.02

100

TRMPERATURE CYCLE TIME IN MINUTES

CORRECT RATE SETTING IN MINUTES

54

40 5030

32

20

1

10

0.3

3

0.2

2

0.1

1

0.03

0.3

0.02

0.2

0.01

0.1

Figure 2. Oscillation Time

Figure 3. Calculating Final Temperature Deviation

Figure 4. Nomogram I

Figure 6. Nomogram III

Figure 5. Nomogram II

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B. TUNING PROCEDURE WHEN NO OSCILLATIONSARE OBSERVED

1. Measure the steady-state deviation, or droop, betweensetpoint and actual temperature with minimum PB setting.

2. Increase the PB setting until the temperature deviation(droop) increases 65%. Nomogram I (see Figure 4)provides a convenient method of calculating the desiredfinal temperature deviation.

3. Set the RESET 1 to a high value (10 R/M). Set the RATE1 to a corresponding value (0.02 MIN). At this point, themeasurement should stabilize at the setpointtemperature due to reset action.

4. Since we were not able to determine a critical oscillationtime, the optimum settings of the reset and rateadjustments must be determined by trial and error. Afterthe temperature has stabilized at setpoint, increase thesetpoint temperature setting by 10 degrees. Observe theovershoot associated with the rise in actual temperature.Then return the setpoint setting to its original value andagain observe the overshoot associated with the actualtemperature change.

Excessive overshoot implies that the RESET and/orRATE values are set too high. Overdamped response(no overshoot) implies that the RESET and/or RATEvalues are set too low. Refer to Figure 7. Whereimproved performance is required, change one tuningparameter at a time and observe its effect onperformance when the setpoint is changed. Makeincremental changes in the parameters until theperformance is optimized.

5. When satisfactory tuning has been achieved, the cycletime should be increased to save contactor life (applies tounits with time proportioning outputs only (TPRI)). Increasethe cycle time as much as possible without causingoscillations in the measurement due to load cycling.

C. TUNING THE PRIMARY OUTPUT FOR COOLINGCONTROL

The same procedure is used as for heating. The processshould be run at a setpoint that requires cooling controlbefore the temperature will stabilize.

D. SIMPLIFIED TUNING PROCEDURE FOR PIDCONTROLLERS

The following procedure is a graphical technique ofanalyzing a process response curve to a step input. It ismuch easier with a strip chart recorder reading the processvariable (PV).

1. Starting from a cold start (PV at ambient), apply fullpower to the process without the controller in the loop,i.e., with an open loop. Record this starting time.

2. After some delay (for heat to reach the sensor), the PVwill start to rise. After more delay, the PV will reach amaximum rate of change (slope). Record the time atwhich this maximum slope occurs and the PV at which itoccurs. Record the maximum slope in degrees perminute. Turn off system power.

3. Draw a line from the point of maximum slope back to theambient temperature axis to obtain the lumped systemtime delay Td (see Figure 8). The time delay may alsobe obtained by the equation:

Td = time to max. slope-(PV at max. slope - Ambient)/max. slope

4. Apply the following equations to yield the PIDparameters:

Pr. Band = Td x max. slope x 100/span = % of spanReset= 0.4 / Td = resets/minuteRate = 0.4 x Td = minutes

5. Restart the system and bring the process to setpoint withthe controller in the loop and observe response. If theresponse has too much overshoot, or is oscillating, thenthe PID parameters can be changed (slightly, one at atime, and observing process response) in the followingdirections:

Widen the proportional band, lower the Reset value, andincrease the Rate value.

Example: The chart recording in Figure 8 was obtained byapplying full power to an oven. The chart scales are10°F/cm, and 5 min/cm. The controller range is 100 to600°F, or a span of 500°F.

Maximum slope = 18°F/5 minutes= 3.6˚F/minute

Time delay = Td = approximately 7 minutes.

Proportional Band = 7 minutes x3.6°F/minutes x 100/500°F = 5%.

Reset = 0.4/7 minutes = 0.06 resets/minute

Rate = 0.4 x 7 minutes = 2.8 minute

Tuning a PID Controller Cont'd

RESET OR RATE TOO HIGH RESET OR RATE TOO LOW

Td

o

O TIME

PV

18

5 mins

T

F

®

Figure 7. Setting RESET and/or RATE

Figure 8. System Time Delay

Z-118

Z

There are three basic types of controllers: on-off,proportional and PID. Depending upon the system to becontrolled, the operator will be able to use one type or theother to control the process.

On/Off An on-off controller is the simplest form of temperaturecontrol device. The output from the device is either on oroff, with no middle state. An on-off controller will switch theoutput only when the temperature crosses the setpoint.For heating control, the output is on when the temperatureis below the setpoint, and off above setpoint.

Since the temperature crosses the setpoint to change theoutput state, the process temperature will be cyclingcontinually, going from below setpoint to above, and backbelow. In cases where this cycling occurs rapidly, and toprevent damage to contactors and valves, an on-offdifferential, or “hysteresis,” is added to the controlleroperations. This differential requires that the temperatureexceed setpoint by a certain amount before the output willturn off or on again. On-off differential prevents the outputfrom “chattering” or making fast, continual switches if thecycling above and below the setpoint occurs very rapidly.

On-off control is usually used where a precise control isnot necessary, in systems which cannot handle having theenergy turned on and off frequently, where the mass of thesystem is so great that temperatures change extremelyslowly, or for a temperature alarm.

One special type of on-off control used for alarm is a limitcontroller. This controller uses a latching relay, which mustbe manually reset, and is used to shut down a processwhen a certain temperature is reached.

ProportionalProportional controls are designed to eliminate the cyclingassociated with on-off control. A proportional controllerdecreases the average power supplied to the heater asthe temperature approaches setpoint. This has the effectof slowing down the heater so that it will not overshoot thesetpoint, but will approach the setpoint and maintain astable temperature. This proportioning action can beaccomplished by turning the output on and off for shortintervals. This “time proportioning” varies the ratio of “on”time to “off” time to control the temperature. Theproportioning action occurs within a “proportional band”around the setpoint temperature. Outside this band, thecontroller functions as an on-off unit, with the output eitherfully on (below the band) or fully off (above the band).However, within the band, the output is turned on and offin the ratio of the measurement difference from thesetpoint. At the setpoint (the midpoint of the proportionalband), the output on:off ratio is 1:1; that is, the on-time andoff-time are equal. if the temperature is further from thesetpoint, the on- and off-times vary in proportion to thetemperature difference. If the temperature is belowsetpoint, the output will be on longer; if the temperature istoo high, the output will be off longer.

The proportional band is usually expressed as apercentage of full scale, or degrees. It may also bereferred to as gain, which is the reciprocal of the band.Note that in time proportioning control, full power is appliedto the heater, but cycled on and off, so the average time is

varied. In most units, the cycle time and/or proportionalband are adjustable, so that the controller may bettermatch a particular process.

In addition to electromechanical and solid state relayoutputs, proportional controllers are also available withproportional analog outputs, such as 4 to 20 mA or 0 to5 Vdc. With these outputs, the actual output level is varied,rather than the on and off times, as with a relay outputcontroller.

One of the advantages of proportional control is thesimplicity of operation. It may require an operator to makea small adjustment (manual reset) to bring the temperatureto setpoint on initial startup, or if the process conditionschange significantly.

Systems that are subject to wide temperature cycling willalso need proportional controllers. Depending upon theprocess and the precision required, either a simpleproportional control or one with PID may be required.

Processes with long time lags and large maximum rates ofrise (e.g., a heat exchanger), require wide proportionalbands to eliminate oscillation. The wide band can result inlarge offsets with changes in the load. To eliminate theseoffsets, automatic reset (integral) can be used. Derivative(rate) action can be used on processes with long timedelays, to speed recovery after a process disturbance.

PIDThe third controller type provides proportional with integraland derivative control, or PID. This controller combinesproportional control with two additional adjustments, whichhelps the unit automatically compensate for changes in thesystem. These adjustments, integral and derivative, areexpressed in time-based units; they are also referred to bytheir reciprocals, RESET and RATE, respectively.

The proportional, integral and derivative terms must beindividually adjusted or “tuned” to a particular system usingtrial and error. It provides the most accurate and stablecontrol of the three controller types, and is best used insystems which have a relatively small mass, those whichreact quickly to changes in the energy added to theprocess. It is recommended in systems where the loadchanges often and the controller is expected tocompensate automatically due to frequent changes insetpoint, the amount of energy available, or the mass to becontrolled.

There are also other features to consider when selecting acontroller. These include auto- or self-tuning, where theinstrument will automatically calculate the properproportional band, rate and reset values for precisecontrol; serial communications, where the unit can “talk” toa host computer for data storage, analysis, and tuning;alarms, that can be latching (manual reset) or non-latching(automatic reset), set to trigger on high or low processtemperatures or if a deviation from setpoint is observed;timers/event indicators which can mark elapsed time or theend/beginning of an event. In addition, relay or triac outputunits can be used with external switches, such as SSRsolid state relays or magnetic contactors, in order to switchlarge loads up to 75 A.

Controller Operation

®

Z-119

SSR Thermal Considerations

One of the major considerationswhen using a SSR, which cannot bestressed too strongly, is that aneffective method of removing heatfrom the SSR package must beemployed. The most commonmethod is to employ a heat sink.SSR’s have a relatively high“contact” dissipation, in excess of 1 watt per amp.

With loads of less than 5 amps,cooling by free flowing air or forcedair current around the SSR isusually sufficient. At higher currentsit will become necessary to makesure the radiating surface is in goodcontact with a heat sink. Essentiallythis involves mounting the baseplate of the SSR onto a good heatconductor, usually aluminum. Goodthermal transfer between the SSRand the heat sink can be achievedwith thermal grease or heat sinkcompound. Using this technique,the SSR case to heat sink thermalresistance (RΘCS) is reduced to anegligible value of 0.1°C/W (celsiusper watt) or less. This is usuallypresumed and included in thethermal data. The simplifiedthermal model in Fig. 18 indicatesthe basic elements to be consideredin the thermal design. The valuesthat are determinable by the userare the case to heat sink interface(RΘCS), as previously mentioned,and the heat sink to ambientinterface (RΘSA).

Thermal CalculationsFig. 18 illustrates the thermalrelationships between the outputsemiconductor junction and thesurrounding ambient. TJ - TA is thetemperature gradient or drop fromjunction to ambient, which is thesum of the thermal resistancesmultiplied by the junction powerdissipation (P watts). Hence

TJ - TA = P(RΘJC + RΘCS + RΘSA)

where

TJ = Junction temperature, °C

TA = Ambient temperature, °C

P = Power dissipation (ILOAD x EDROP) watts

RΘJC = Thermal resistance,junction to case °C/W

RΘCS = Thermal resistance,case to sink. °C/W

RΘSA = Thermal resistance,sink to ambient °C/W

To use the equation, the maximumjunction temperature must beknown, typically 125°C, togetherwith the actual power dissipation,say 12 watts for a 10 amp SSR,assuming a 1.2 volt effective (notactual) voltage drop across theoutput semiconductor. The powerdissipation (P watts) is determinedby multiplying the effective voltagedrop (EDROP)

Assuming a thermal resistance fromjunction to case (RΘJC) of, say,1.3°C/W and inserting the abovetypical values into the equation,solutions can be found for unknownparameters, such as maximum loadcurrent, maximum operatingtemperature, and the appropriateheat sink thermal resistance.Where two of these parameters areknown the third can be found asshown in the following examples:

(a) To determine the maximumallowable ambient temperaturefor 1°C/W heat sink and 10 ampload (12 watts) with a maximumallowable T3 of 100°C:

TJ - TA = P(RΘJC + RΘCS + RΘSA)

= 12 (1.3 + 0.1 + 1.0)

= 28.8

hence,

TA = TJ - 28.8

= 100 - 28.8

= 71.2°C

(b) To determine required heat sinkthermal resistance, for 71.2Cmaximum ambient temperatureand a 10 amp load (12 watts):

TJ - TARΘSA = ––––– - (RΘJC + RΘCS)P

100 - 71.2= –––––––– -(1.3 + 0.1)

12

= 1°C/W

(c). To determine maximum loadcurrent, for 1°C/W heat sink and71.2°C ambient temperature:

TJ - TAP = ––––––––––––––––RΘJC + RΘCS + RΘSA

100 - 7.2= ––––––––––––

1.3 + 0.1 + 1.0

=12 watts

hence,

PILOAD = ––––––

EDROP

12= ––

1.2

= 10 amperes

Regardless of whether the SSR isused on a heat sink or the case iscooled by other means, it is possibleto confirm proper operatingconditions by making a direct baseplate temperature measurementwhen certain parameters areknown. The same basic equation isused except that base platetemperature (TC) is substituted forambient temperature (TA) and RΘCSand RΘSA are deleted. Thetemperature gradient now becomesTJ - TC that is the thermal resistance(RΘJC) multiplied by the junctionpower dissipation (P watts). Hence:

TJ - TC = P(RΘJC)

Parameter relationships are similarin that solutions can be found formaximum allowable casetemperature, maximum load current,and required junction to case (RΘJC)thermal resistance. Again, wheretwo parameters are known, the thirdcan be found as shown in thefollowing examples (using previousvalues).

(d). To determine maximumallowable case temperature, for

TJ

RΘJC RΘCA

RΘJC RΘCS RΘSA

NO HEAT SINK

WITH HEAT SINK

CASETEMPERATUE

HEAT SINKTEMPERATUE

HEAT FLOW

OUTPUTSEMICONDUCTOR

(JUNCTIONTEMPERATURE)

AMBIENT(AIR TEMPERATURE)

TJ TC TS TA

TC TA

Fig. 18 A simplified thermal model

Z-120

Z

RΘJC = 1.3°C/W and 10 amp load(12 watts):

TJ - TC = P (RΘJC)

= 12 x 1.3

= 15.6

hence,

TC = TJ - 15.6

= 100 - 15.6

= 84.4°C

(e). To determine maximum loadcurrent for RΘJC = 1.3°C/W and84.4°C case temperature:

TJ - TCP = ––––––RΘJC

100 - 84.4= ––––––––

1.3

= 12 watts

hence,

PILOAD = ––––––

EDROP

12= ––

1.2

= 10 amperes

(f). To determine required thermalresistance (RΘJC) for 84.4°C casetemperature and 10 amp load (12watts):

TJ - TCRΘJC = –––––P

100 - 84.4= ––––––––

12

= 1.3°C/W

In examples (a) through (c) SSRoperating conditions are determinedas they relate to ambient airtemperature using a heat sink.Similarly, conditions can bedetermined for an SSR operating infree air without a heat sink, providedthat a value is given for the radiatingcharacteristics of the package(RΘCA). This value is rarely given

and when it is, it is more commonlycombined with (RΘJC) and stated as(RΘJA) The equation would appearas follows:

TJ - TA = P(RΘJC + RΘCA )

Or

TJ - TA = P(RΘJA)

Where

RΘCA = Thermal resistance, caseto ambient, °C/W

RΘJA = Thermal resistance,junction to ambient, °C/W

The equation can be used tocalculate maximum load current andmaximum ambient temperature asbefore. However, the resultantvalues are inclined to be lessprecise due to the many variablesthat affect the case to airrelationship (i.e... positioning,mounting, stacking, air movement,etc).

Generally, free air performance isassociated with PCB or plug-inSSR’s of 5 amps or less, whichhave no metallic base to measure.The question is often raised as towhere the air temperature ismeasured. There is no clear-cutanswer for this. Measurement ismade more difficult when the SSR’sare closely stacked, each creating afalse environment for its neighbor.One suggested approach is to placea temperature probe orthermocouple in the horizontal planeapproximately 1 inch away from thesubject SSR. This technique isreasonably accurate and permitsrepeatability.

RatingsThe free air performance of lowerpowered SSR’s is usually defined inthe catalogue by means of a singlederating curve, current versusambient temperature based on theforegoing formulas, which isadequate for most situations

Heat SinkingUnder worst case conditions theSSR case temperature should notexceed the maximum allowableshown in the right hand verticalscales of Fig. 19.

A typical finned section of extrudedaluminum heat sink material isshown in outline form in Fig. 20. A2 inch length of this material wouldapproximate the same thermalcharacteristics as curve (a) in Fig.21, likewise, a 4 inch length wouldapproximate curve (b). This isassuming the heat sink is positionedwith the fins in the vertical plane,with an unimpeded air flow.

As a general rule, a heat sink withthe proportions of the 2 inch lengthof extrusion (curve (a)) is suitable

PO

WE

R D

ISS

IPAT

ION

(W

)

LOAD CURRENT (ARMS)

RΘCS+ RΘSA=

3.0C/W 2.0C/W

1.0C/W

0.5C/W

B

L

F

J

I A

MAX AMBIENT TEMPERATURE (°C)

NO HEAT SINK

MA

X A

LLO

WA

BLE

CA

SE

TE

MP

ER

ATU

RE

(°C

)

35

30

25

20

15

10

5

80

85

90

95

100

105

110

0 5 10 15 20 25/0 10 20 30 40 50 60 70 80

E

K H

C

DG

Fig. 19 Thermal operating curves (25 A SSR)

SSR

1.5INCHES

2.3INCHES

0.15INCH

Fig. 20 Typical light duty aluminum heatsink extrusion (end view)

Z-121

for SSR’s rated up to 10 amps,while the 4 inch length (curve (b))will serve SSR’s rated up to 20amps. For power SSR’s withratings greater than 20 amps, heavyduty heat sink of the type shown inFig. 22 become necessary. Theperformance of a 5.5 inch length ofthe extrusion would approximate thecharacteristics shown in Fig. 23.

Not all heat sink manufacturersshow their characteristics in termsof degrees C per watt (°C/W). Someshow them as a temperature riseabove ambient as shown in Fig. 23.In this case, a value for RΘSA isfound by dividing power dissipation(watts) into the temperature rise(°C). For example, taking the 60watt point on the dissipation scalethe free air curve would indicate a40 degree rise. Hence:

TRISERΘSA = ––––P

40= ––

60

= 0.66°C/W

In many applications, the SSR ismounted to a panel or base platewhich may also be more than

adequate as a heat sink. Byensuring flatness, using thermalcompound, and removing paint tomaximize effectiveness, a baseplate (SSR) temperaturemeasurement at maximum ambientmay be all that is necessary toconfirm proper operation aspreviously mentioned.

If an SSR installation does notprovide an adequate heat sink, aselection is made from the widevariety of commercial heat sinktypes that are available. Eachconfiguration has its own uniquethermal characteristics and areusually well documented withmanufacturers’ performance curvesand application data.

STILL AIR(NATURAL CONVECTION)

FINS VERTICAL

POWER DISSIPATED (WATTS)

TE

MP

ER

ATU

RE

RIS

E A

BO

VE

AM

BIE

NT

(°C

)

300 LFM

500 LFM

1000 LFM

100

80

60

40

20

0

0 20 40 60 80 100 120 140 160

Fig. 23 Typical free-moving air characteristics of a heavy duty heat sink,temperature rise versus power dissipated

SSR

2.62INCHES

4.75INCHES

1.44INCHES

Fig. 22 An end view of a typical heavyduty aluminum heat sink extrusion

A

TH

ER

MA

L R

ES

ISTA

NC

E (

RΘ

SA)°

C/W

B

0 5 10 15 20 25 30 35

3.0

2.5

2.0

1.5

1.0

DISSIPATION (WATTS)

Fig. 21 Typical heat sink characteristics

SSR Thermal Considerations Cont’d

Z-122

Z

Model PT41 aprecision clock/timer,controller, combinesthe features of manydedicated metersinto onemultipurpose design.See Figure 1.Challenge thisuniversal andeconomical,programmabletimer/controller toany level task, fromvariable cycle timingin complex patternsto elementarystop watch and resetoperations.

Timing modes andpatterns are virtuallyunlimited and the four independentlycontrolled outputs are easilyprogrammed using front panelpushbuttons or remote serial link.Connected by a common bus toother DP41 series test instruments,the PT41 timer/ controller is capableof requesting readings from allmeters and recording the data ona common printer.

Special FeaturesThe features of this precisioninstrument allow variations oftiming patterns through simplifiedprogramming and processmonitoring. There are fourindependent outputs with eightprogrammable setpoints and fivecontrolled output modes allowingfor extensive combinations of loadcontrol patterns. For the often usedtiming sequences, the instrumentcan store up to 64 preset patterns.Operations may be timed inintervals as short as 0.01 second oras long as 24 hours and will repeatany cycle up to a million times.The meter may be configured touse any one of eight built-in timebases (such as time-of-day or onehour resolution).

The user can view the setup andtiming configuration any time themeter is functioning. Depress thefront panel REVIEW button oractivate the remote serial link andthis feature will display the timingsequence without disturbing thetiming function.

If power is interrupted, themicroprocessor-based nonvolatilememory retains all timer settings. Ifretention of day and date is required,a battery backup option is available.

Programming Made SimpleThe PT41 is fully programmablefrom the front panel or remotely viaan RS-232 or RS-485 serial link.Front panel programming isaccomplished with five pushbuttons.The programmer is prompted withkey words (such as START, TIMSET,UNITS, ELAPSE) on the six positionalphanumeric LED display.

The remote programming optionhas more than forty commandswhich allows full control by apersonal computer or work station.Programming and timing status isfed back to the personal computerfor program verification. The remoteprogramming feature comes with itsown directive software.

Automated Data LoggingA unique feature of the PT41 isfound in its controller mode. Amaximum of 32 DP41 seriesinstruments (such as voltmeters,temperature indicators, batchcontrollers) equipped with RS-485serial interface boards, can bebussed together using thisinstrument as a timer/controller. Itcan sequence through all meters onthe bus and request readings fromall devices. An RS-485 printer, alsolocated on the bus, is then directed

to record the readings, with orwithout a time and date stamp.The PT41 can be programmed tomonitor remote devices in intervalsof up to eleven days. Figure 2illustrates a typical configurationusing the PT41 to connect threeDP41 instruments and a printer.

Manages Any Time ProblemThe flexible timing and output loadcontrol of this meter provide thetools needed to manage any timingproblem. Applications such aslife testing, burn-in, reliabilityevaluation, process control, andrepeat cycle timing are typical.

Example 1 Time and control ofintermittent burn-in, where a productis to be energized for ten secondsand deenergized for 50, with theprocess cycled 10,000 times;voltage readings logged every hour.

Example 2 Time and control offour production processes runningconcurrently, each requiring differentstart-stop sequencing with an alarmto signal key steps in each process.

Example 3 Control the openingand closing time periods for a setof doors in a facility for securityreasons.

Example 4 Record readingsfrom five remote unattended testinstruments once a day and repeatthe process for ten days.

Figure 1 PT41 timer/controller

No Time Out for ThisProgrammable Timer/Controller

Z-123

RS-485RS-485

RS-485 RS-485

DP41-EPROCESS METER

DPF400RATE TOTALIZER

DP41-TTEMPERATURE INDICATOR PRINTER

PTC41TIMER/

CONTROLLER

12

34

SETPTS REVIEW STOP MENU RESET

12

34

12

34

12

34

SETPTS MAX MIN MENU RESET

SETPTS DISPLAY STOP MENU RESET

SETPTS MAX DEV MENU RESET

A B C D E F G H I J K L M N OP Q R S T U V W X Y Z [ / ] ^ _

A B C D E F G H I J K L M N OP Q R S T U V W X Y Z [ / ] ^ _

A B C D E F G H I J K L M N O

Adaptable DesignThe six position, 14 segment red orgreen LED display operates at100% and 50% brightness levels.Additional indicator lights showalarm settings, AM/PM referenceand timer status. The clock timebase is derived from the 50 or 60 Hzline frequency and from an internalcrystal oscillator with an accuracy of±50 PPM over the full operatingtemperature range of +32°F to

+140°F (0°C to +60°C). The ACpower is 115V or 230V ±10 % withpower consumption 9 Wattsmaximum.

The UL-rated polycarbonate case isdimensioned 1.89" H x 3.78" W x5.86" D (48 x 96 x 149 mm).

Universal InstrumentThe PT41 is a full functioninstrument capable of timing,controlling and directing datalogging. The functions and featuresincluded in this one low costinstrument are normally attained bycombining several individual meters.PT41 functions in a panel mount ortable configuration and is the “all inone” solution for automated test,operation and process control.

Figure 2 A typical configuration demonstrating the PT41 linked to three DP41 instruments and a printer.

Controller Mode Operation

No Time Out for This Programmable Timer/Controller

U.S. and Int’l Patents.Used Under License.

CONTROLSIGNAL

REEDRELAY TRIAC

OPTIONALPREAMPLIFIER

TRIGGERCIRCUIT

AC POWER

LOAD

Z-124

Z

SSR Defined. A solid-state relay is an ON-OFF controldevice in which the load current is conducted by one ormore semiconductors - e.g., a power transistor, an SCR,or a TRIAC. (The SCR and TRIAC are often called“thyristors,” a term derived by combining thyratron andtransistor, since thyristors are triggered semiconductorswitches.)

Like all relays, the SSR requires relatively low control-circuit energy to switch the output state from OFF to ON,or vice versa. Since this control energy is very much lowerthan the output power controllable by the relay at full load,"power gain" in an SSR is substantial--frequently muchhigher than in an electromagnetic relay of comparableoutput rating. To put it another way, the sensitivity of anSSR is often significantly higher than that of an EMR ofcomparable output rating.

Types of SSR's. It is convenient to classify SSR's by thenature of the input circuit, with particular reference to themeans by which input-output isolation is achieved. Threemajor categories are recognized:

• Reed-Relay-Coupled SSR's (see figure 1), in which thecontrol signal is applied (directly, or through apreamplifier) to the coil of a reed relay. The closure ofthe reed switch then activates appropriate circuitry thattriggers the thyristor switch. Clearly, the input-outputisolation achieved is that of the reed relay, which isusually excellent.

• Transformer-Coupled SSR's (see figure 2), in whichthe control signal is applied (through a DC-ACconverter, if it is DC, or directly, if It is AC) to the primaryof a small, low-power transformer, and the secondaryvoltage that results from the primary excitation is used(with or without rectification, amplification, or othermodification) to trigger the thyristor switch. In this type,the degree of input-output isolation depends on thedesign of the transformer.

• Photo-coupled SSR's (see figure 3), in which thecontrol signal is applied to a light or infrared source(usually, a light-emitting diode, or LED), and theradiation from that source is detected in a photo-sensitive semi-conductor (i.e., a photosensitive diode, aphoto-sensitive transistor, or a photo-sensitive thyristor).The output of the photo-sensitive device is then used totrigger (gate) the TRIAC or the SCR's that switch theload current. Clearly, the only significant “coupling path”between input and output is the beam of light or infra-red radiation, and electrical isolation is excellent. TheseSSR's are also referred to as “optically coupled” or“photo-isolated”.

In addition to the major types of SSR's described above,there are some special-purpose designs that should bementioned:

• Direct-control AC types (see figure 4), in which externalcontacts, operating in a circuit energized by the sameAC power line as is used for the load circuit, trigger aTRIAC (or back-to-back-connected SCR's). This type isalso referred to as having a “switch closure” input.Clearly, this type of relay, while simpler and inherentlyless expensive than more sophisticated designs, has thegreat disadvantage (for most applications) of having noisolation between the control and load circuits.

• Direct-control DC types (see figure 5) in which externalcontacts, operating in a circuit energized by the sameDC power line as is used for the load circuit, control theconduction of a transistor. This type of relay, which isperhaps the simplest of all, and inherently the leastexpensive, also has the great disadvantage (for mostapplications) of having no isolation between the controland load circuits.

• SCR types designed for DC, in which the load-current-carrying SCR is made to turn off by means of a second

Solid StateReIays

Defined and Described

TRIAC LOAD

TRIGGERCIRCUIT

AC POWER

CONTROL DC-ACCONVERTER

ISOLATINGTRANSFORMER

LED

PHOTO-TRANSISTOR

TRIAC

TRIGGERCIRCUIT

AC POWER

LOADCONTROLSIGNAL

Figure 2. Transformer-Coupled SSR

Figure 3. Photo-Coupled SSR

Figure 1. Hybrid SSR

CONTROLCONTACTS

AC POWER

LOADTRIGGERCIRCUIT

DC POWER

LOADCONTROLSIGNAL

ISOLATINGCIRCUIT

(SEE FIGS. 1-3)

COMMUTATINGCAPACITOR

R

SCR-2 SCR-1A

B

CONTROLCONTACTS

DC POWER

LOAD

Z-125

SCR, connected in a “commutating circuit” (such as that offigure 6), which is capable of turning off the first SCR bymomentarily reducing its current to zero.

• Designs using special isolating means, such as. . .

...the Hall effect in which the motion of a magnetexternal to, but in proximity to, the SSR causes achange in resistance in a field -sensitive material,thereby triggering on-off behavior.

...oscillator tuning, in which the external signal shifts thefrequency of an oscillator, thereby causing a closelycoupled resonant circuit to trigger on-off behavior.

...saturable reactors or magnetic amplifiers, in which aDC control current in one winding controls the inducedvoltage (from an AC source) in another winding. Theinduced voltage is then used to trigger on-off behavior.

It is safe to say that well over 95% of all SSRrequirements are best satisfied by one of the three majortypes described earlier (i.e., figures 1-3).

Input Circuit Performance. The sensitivity of isolatedSSR’s (that is, the minimum control voltage and current atwhich the SSR turns on) depends on the characteristics ofthe isolating component or circuit:

• In hybrid (reed-relay isolated) designs, the SSR’ssensitivity is established by the operating-powerrequirement of the reed relay, which ranges from as lowas 40 milliwatts (e.g., 5 volts dc at 8 mA) to as high asseveral hundred milliwatts. Note that the low-voltage,low-power designs are compatible with standard digital-computer “logic levels,” and that the standard “high-fan-out” TTL logic-level output from a digital computer ordigital controller can drive two or more hybrid SSR’s inparallel.

• In transformer-coupled SSR’s, the sensitivity is usuallyconsiderably higher than that of the hybrid type,

because all the input signal must do is to gate on theAC-DC converter (see figure 2) that drives thetransformer, and that requires, typically, less than10 milliwatts (e.g., 4.5 v dc at 2 mA) and rarely morethan 50 milliwatts. This sensitivity is better than requiredby any single-TTL digital output, and a high-fan-out TTLoutput can drive from 3 to 10 such SSR’s in parallel.

• In optically coupled SSR’s, the sensitivity ranges fromabout 6 milliwatts (e.g., 3 volts dc at 2 mA) to 100milliwatts. Using an appropriate series resistor or currentregulator, this type of input circuit is also compatible withTTL logic levels, and several optically coupled SSR’scan be driven in parallel by high-fan-out logic lines.

• The sensitivity of most “direct-control“ SSR’s (figures 4and 5) is significantly lower than that of the isolateddesigns, but that fact is of little importance because thecontrol power required is almost always well within thecapability of even the smallest control contacts.

The maximum turn-off level (voltage and/or current) of anSSR is about 50% of the minimum level at which it turnson. This characteristic provides an adequate margin ofsafety between the ON and OFF states, therebyeliminating erratic behavior due to small changes in thecontrol signal.

In many SSR designs, the control-voltage range is muchgreater than that implied by the minimum turn-on voltage.In designs optimized for wide input voltage range, it is notuncommon for the SSR to be rated for use over more thana 6-to-1 range of control voltages (e.g., 3.0 V to 32 V). Inhybrid designs, the coil of the reed relay may be wound foralmost any useful control voltage, from as low as 3 voltsnominal, to 50 volts, or even higher, but the range of inputvoltage tolerated by a hybrid SSR is limited by dissipationin the relay coil. Generally, a range of 1.5 to 1 isacceptable. On the other hand, series resistance, or a“constant-current” active input circuit, may be used toaccommodate a hybrid relay to higher input voltages.

Solid State Relays Cont’d

Figure 4. Direct-Control AC SSR

Figure 5. Direct-Control DC SSR

Figure 6. SSRusing SCR switch

Z-126

Z

Input Characteristics. Beyond consideration of thesensitivity characteristics (page Z-120), we must alsodescribe the input-circuit isolation characteristics of anSSR, which requires consideration of many differentparameters, including:

• Dielectric strength, rated in terms of minimumbreakdown voltage from control circuit to both theSSR case and the output (load) circuit. A typicalrating is 1500 volts ac (RMS), for either control tocase or control to output.

• Insulation Resistance, from control circuit to boththe case and the output circuit. Typical ratings rangefrom 10 megohms to 100,000 megohms fortransformer and hybrid designs. For optically isolatedSSR’s, typical insulation resistances range from 1000to 1 million megohms.

• Stray Capacitance from control circuit to both caseand the output circuit. Capacitance to case is rarelysignificant, but capacitance to the output circuit maycouple ac and transients back to the sensitive controlcircuit, and even further back, into the control-signalsources. Fortunately, in well designed SSR’s, thiscapacitance is rarely large enough to causeinteraction. Typical stray capacitance ranges from 1to 10 picofarads.

The speed of response of the SSR to the application ofcontrol voltage is covered later in this section.

Output Circuit Performance. Clearly, the mostsignificant output-circuit parameters are the maximumload-circuit voltage that may be impressed across therelay output circuit in the OFF condition without causingit to break down into conduction or failure, and themaximum current that can flow through the outputcircuit and load in ON condition.

Note that these parameters are (at least at first glance)analogous to the usual voltage and current ratings of thecontacts on an electro-magnetic relay. There are,however, differences between EMR output ratings andSSR output ratings--differences that will be examined indetail as this exposition proceeds.

In the most general approach, one may say that the“contact ratings” of an SSR are determined almostentirely by the characteristics of the load-currentswitching device. Perhaps this fact is most apparentfrom an examination of the simplest type of ac SSR - adirect-control (non-isolated) design, such as thatoriginally shown in figure 4, and redrawn above in figure7, with its equivalent circuit for both the ON and OFFstates. In the ON state (figure 7b), the TRIAC exhibits anearly constant voltage drop (i.e., almost independent ofload current) approximately equal to that of two silicondiodes - less than 2 volts. The passage of load currentthrough this voltage drop causes power dissipation(Pd = Vd x Iload), and this power will cause atemperature rise in the TRIAC junction. If proper “heat-sinking” is provided - i.e., thermal conduction from theTRIAC case to the outside air or to a heat-conductivemetal structure that can in turn dissipate the power tothe surrounding air without significant temperature rise -then the TRIAC temperature will not rise above the ratedmaximum value for reliable operation (typically, 100°C).With generous heat sinking, the current rating of theSSR may be determined, not by power dissipation, butby the current rating of the TRIAC.

Figure 7c shows the equivalent circuit of this very simpleSSR in the OFF state. Note that even when the TRIACis turned off, a very small amount of leakage current canflow. This current path, represented by a resistance inthe equivalent circuit, is actually a non-linear function ofthe load-circuit voltage. The normal practice, in rating

LOAD

AC POWER

TRIGGERCIRCUIT

(a)

VSUPPLY

lLOAD

VdR

L

(b)

(c)

RL

l L E A K A G E

VOFF R L E A K A G E

VSUPPLY

VSUPPLYlLOAD

VLOAD

(≈ VSUPPLY)VSSR (X50)

Figure 8a. ON-Mode Waveforms(VSSR is greatly exaggerated)

Figure 7. Simplified Circuit of anSSR (a), and equivalent circuits forthe ON state (b) and theOFF state. (c)

Z-127

TRIAC’s, is to specify a worst case maximum value forthis “OFF-state leakage” and a typical value is 0.001 Amax. for a 5-ampere load-current rating. The load circuitvoltage rating is simply that determined by the blockingvoltage rating of the thyristor.

The output-circuit ratings of the more common isolatedSSR’s, most of which are designed to control ac loadcircuits, are very similar to those described above,except that OFF-state leakage is usually higher---on theorder of 5 mA at 140 V for a 5-ampere device---still onlyabout one-thousandth of the load current rating. Figure7 shows the equivalent circuit of a TRIAC-switch SSRdesign, and figure 8 shows the voltage and currentwaveforms in the load circuit, for both OFF and ONstates. Note that the ON-state voltage-drop curves aredrawn to a much expanded scale compared with theOFF state and load voltage curves.

Even at this early stage in our examination of SSRperformance, it is necessary to consider the timerelationships between the control signal and the acload-circuit voltage and current.

With respect to timing, there are two classes ofswitching SSR’s. In one, no particular effort is made toachieve synchronism between the alternations of theload circuit-power line and the turning on of the thyristorswitch. In this “non-synchronous” class, then, theresponse delay between the application of controlvoltage and the beginning of load-circuit conduction isvery short...typically from 20 to 200 microseconds inoptically coupled and transformer types, and less thanone millisecond in hybrids (longer due to the reed relayoperation time). The current waveform on turn-on innon-synchronous designs is clearly a function of whenin the ac cycle the control signal is applied, asillustrated in figure 9a.

In synchronous (zero-voltage turn-on) designs, theeffect of the application of a control signal is delayed (ifnecessary) until the power-line voltage is passingthrough zero (see figure 9b). (This is done by internalgating circuitry that senses the magnitude of the linevoltage, and prevents triggering the thyristor until thenext zero crossing occurs.) Thus, if the control signalhappens to be applied immediately after a zerocrossing, the SSR would not actually begin conductinguntil almost a full half-cycle later. On the other hand, ifthe control signal happens to be applied just before azero-crossing is about to occur, the SSR would begin toconduct almost immediately, with only the very smallturn-on delays described above for non-synchronousdesigns. Clearly, then, the turn-on delay of asynchronous SSR can have any value from less than amillisecond to a full half-cycle of the power line (about8.3 milliseconds for a 60-Hz power line). Usually, for 60Hz service, the rating is given as 8.3 millisecondsmaximum for all-solid-state designs, and 1.5milliseconds maximum for hybrid designs.

The final major characteristic of the AC-switching SSRis its turn-off behavior. Because a thyristor, oncetriggered, will not stop conducting until the load currentflowing through it falls to zero, there is a maximumpossible turn-off delay (between the removal of thecontrol signal and the cessation of load current) of onehalf cycle. As in the case of turn-on, the minimum turn-off delay is close to zero. Thus, a typical 60-Hz ratingfor turn-off time is 9 milliseconds maximum. ®

lL E A K A G E

( ≈ 1/1000 X lL O A D

)

V S S R ≈ V S U P P LY

V S U P P LY

VSUPPLY

CURRENTCONTINUESTO HERE

lLOAD

CONTROLSIGNAL OFF

ON

OFF

VSUPPLY

lLOAD

CONTROLSIGNAL OFF

ON

OFF

STARTDELAY

TURN OFFHERE

CURRENTSTARTS ATNEXTCROSSING

Figure 9a. Non-Synchronous SSRwaveforms for resistive load

Figure 8b. OFF-Mode Waveforms (Ileakage is greatly exaggerated)

Figure 9b. Synchronous SSRwaveforms for resistive load

Reproduced with permission of Crydom Corporation

Solid State Relays Cont’d

Z-128

Z

How are Hazardous Locations Defined?Answer: According to the National Electrical Code,Article 500, hazardous locations are defined by Class,Group and Division. Differentiation by Class and Groupis in accordance with the laws of physics, while Divisionclassification is based on environmental and physicalplant conditions.

Relative to the application of Intrinsic Safety, it isimportant to define the actual Class, Group and Divisioninto which any proposed Intrinsically Safe electricalcircuits are to be installed. As shown by the ignitioncurves, all flammable mixtures do not require the sameenergy levels to ignite. Because Intrinsic Safetyrequires maintaining an energy level lower than thatrequired to ignite a specific hazardous mixture, it isimportant to know what the energy allowances are foroperational and safety considerations.

Typical Resistance Circuit Ignition Currents IdentifyOnly Four Hazardous Substances: Hydrogen,Ethylene, Propane and Methane. Aren’t There MoreFlammable or Combustible Materials Than That?Answer: Yes, but those four hazardous mixturesrepresent the basis for all flammable or combustiblemixtures subject to ignition from electrical sources. Allare found, as shown in the Hazardous (Classified)Locations chart following, in Class I, with Hydrogenidentified as Group B; Ethylene identified as Group C;Propane being Group D and, as a separate curve withinGroup D, Methane.

Acetylene: Group A and Hydrogen: Group B share thesame required energy levels relative to ignition. Theyrequire less energy for ignition than does Group C,which requires less energy for ignition than Group D.Within Class II Group E, metal or electrically conductivedusts, Group F, Coal Dust and Group G, electricallynonconductive dusts, generally grain or agriculturaldusts are identified. As Groups A and B share the sameignition curve, Group C, Ethylene, and Group E, metalor electrically conductive dusts, share the same ignitioncurve. Groups D, Propane, F, Coal Dust, and G,electrically nonconductive dusts, share the sameignition curve.

A complete listing of hazardous mixtures defined byGroup can be found in National Fire ProtectionAssociation document NFPA 497 M.

The Definition of Intrinsic Safety Identifies BothElectrical and Thermal Energy as Potential Causesof Ignition. How Does Thermal Energy Relate to theIgnition of a Specific Flammable or CombustibleMixture?

Answer: There are temperatures at which a flammableor combustible mixture will ignite. The minimumtemperature at which ignition takes place is called the“Auto-Ignition Temperature.” Intrinsically Safe systemswill not allow thermal energy to reach levels at which aspecific flammable or combustible mixture will auto-ignite.

Figure 1 identifies common hazardous mixtures andtheir auto-ignition temperatures.

Intrinsic Safety

AutoignitionHazardous Temperature

Mixture °C °FAcetone 540 1004

Acetylene 305 581Ammonia 630 1166Benzene 220 428Benzol 555 1031Butane 365 689

Butylalchohol 340 644Carbon Disulphide 95 203

Carbon Oxide 605 1121Cyclohexane 430 806Diesel Fuel 220 to 300 428 to 572

Ethane 515 959Ethylacetate 460 860Ethylalchohol 425 797Ethylchloride 510 950

Ethylene 425 797Ethylether 180 356

Ethyl Glycol 235 455Fuel Oil 220 to 300 428 to 572Hexane 240 464

Hydrogen aeroxide 560 1040Hydrogen disulphide 270 518

Methane 595 1103Methanol 455 851

Methyl chloride 625 1157Naphthalene 520 968

Phenol 595 1103Propane 470 878Tetraline 425 797

Toluol 535 995

Figure 1: Autoignition temperatures of some hazardous mixtures.

Reproduced with permission of R. Stahl.

Z-129

Class IFlammable Gases or Vapors

Division 1•Exists under normal conditions•May exist because of:- repair conditions- maintenance operations- leakage

•Released concentrationbecause of:- breakdown of equipment- breakdown of process- faulty operation of equipment- faulty operation of process

which causes simultaneousfailure of electrical equipment

Group A: Atmospheres containing Acetylene

Group B: Atmospheres such as Butadiene, ethylene oxide,Propylene Oxide, Acrolein, or Hydrogen (or gasesor vapors equivalent in hazard to hydrogen suchas manufactured gas)

Group C: Atmospheres such as Cyclopropane, Ethyl Ether,Ethylene, or gases or vapors equivalent in hazard

Group D: Atmospheres such as Acetone, Alcohol,Ammonia, Benzene, Benzol, Butane, Gasoline,Hexane, Lacquer Solvent vapors, Naphtha,Natural Gas, Propane or gases or vaporsequivalent in hazard

Division 2•Liquids and gases in closedcontainers or the systems are:- handled- processed- used

•Concentrations are normallyprevented by positivemechanical ventilation.

•Adjacent to a Class I, Division 1location

Intrinsic Safety Cont’d

Hazardous (Classified) Locations in Accordance with Article 500, National Electric Code-1990

Z-130

Z

Class IICombustible Dusts

Division 1•Exists under normal conditions•Combustible mixtureproduced by:- mechanical failure of

equipment or machinery- abnormal operation of

equipment and providesource of ignition from:

- simultaneous failure ofelectrical equipment

- simultaneous failure ofoperation of protection devices

- other causes•Electrically conductive dustsmay be present

Group E: Atmospheres containing combustible metal dusts(regardless of resistivity), dusts of similarlyhazardous characteristics ( < 100 kΩ/cm) orelectrically conductive dusts

Group G: Atmospheres containing combustible dusts havinga resistivity > 100 kΩ/cm or electricallynonconductive dusts

Division 2•Not normally in the air•Accumulations normallysufficient to interfere withnormal operation of electricalequipment or other apparatus.

• In the air as a result ofinfrequent malfunctioning of:- handling equipment- process equipment

•Accumulations are sufficient tointerfere with the safedissipation of heat fromelectrical equipment

•Accumulations may be ignitibleby abnormal or failure ofelectrical equipment

Division 1•Fibers or materials producingcombustible flyings aremanufactured, stored orhandled

Not Grouped•Manufacturers such as textilemills, cotton-related mills orclothing plants

•Fibers and flyings includingRayon, Cotton, Sisal, Hemp,Jute and Spanish Moss

Division 2•Fibers are handled exceptduring the process ofmanufacture or are storedexcept during the process ofmanufacture

Class IIIIgnitable Fibers or Flyings

Group F: Atmospheres containing combustible CarbonBlack, Charcoal or Coke Dusts which have > 8%total volatile material or if these dusts are sensitizedso that they present an explosion hazard andhaving a resistivity > 100 kΩ/cm but ≤ 100 MΩ/cm

Making instrumentsintrinsically safe need notseem like a nightmare. Here,the basics of intrinsic safetycircuit design are discussed.

Paul S. Babiarz

Intrinsic safety prevents instrumentsand other low-voltage circuits inhazardous areas from releasingsufficient energy to ignite volatilegases. Although it is used widely inEurope to safely install and operateinstrumentation circuits inhazardous areas, it has causedmuch confusion in North Americanmarkets. Many users have heard ofit and want to know more; however,most feel uncomfortable applyingintrinsically safe products. Onereason is that intrinsic safety hasbeen a part of Section 504 of theNational Electric Code only since1990. In addition, the number ofdifferent products on the market andseemingly endless calculationsmake applying intrinsic safety seemlike an engineer’s nightmare.

This is the first of a series of shortarticles that explain how to makethe most common field devices(thermocouples, RTDs, contacts,solenoid valves, transmitters, anddisplays) intrinsically safe. We willbegin with an introduction to thepractical side of intrinsic safetycircuit design.

Start With The Field DeviceAll intrinsically safe circuits havethree components: the field device,referred to as the intrinsically safeapparatus; the energy-limiting

device, also known as a barrier orintrinsically safe associatedapparatus; and the field wiring.When designing an intrinsically safecircuit, begin the analysis with thefield device. This will determine thetype of barrier that can be used sothat the circuit functions properlyunder normal operating conditionsbut still is safe under fault conditions.

More than 85% of all intrinsicallysafe circuits involve commonlyknown instruments. Figure 1 showsthe approximate use of intrinsicallysafe apparatus in hazardous areas.

An intrinsically safe apparatus (fielddevice) is classified either as asimple or nonsimple device. Simpleapparatus is defined in paragraph

3.12 of the ANSI/ISA-RP 12.6-1987as any device which will neithergenerate nor store more than 1.2volts, 0.1 amps, 25 mW or 20 µJ.Examples are simple contacts,thermocouples, RTDs, LEDs,noninductive potentiometers, andresistors. These simple devices donot need to be approved asintrinsically safe. If they areconnected to an approvedintrinsically safe associatedapparatus (barrier), the circuit isconsidered intrinsically safe.

A nonsimple device can create orstore levels of energy that exceedthose listed above. Typical examplesare transmitters, transducers,solenoid valves, and relays. Whenthese devices are approved asintrinsically safe, under the entityconcept, they have the followingentity parameters: Vmax (maximumvoltage allowed); Imax (maximumcurrent allowed); Ci (internalcapacitance); and Li (internalinductance).

The Vmax and Imax values arestraightforward. Under a faultcondition, excess voltage or currentcould be transferred to theintrinsically safe apparatus (fielddevice). If the voltage or currentexceeds the apparatus’ Vmax orImax, the device can heat up orspark and ignite the gases in thehazardous area. The Ci and Livalues describe the device‘s abilityto store energy in the form ofinternal capacitance and internalinductance.

Figure 1. Current use of intrinsically safeapparatus in hazardous areas.

Figure 2. Barrier circuit

Safe Area Intrinsically Safe Barrier Hazardous Area

FuseCurrent Limiting

Resistor

ZenerDiodes

InputVoltage

FieldDevice

Instrinsically SafeGround

Z-131

Intrinsic Safety CircuitDesign

Intrinsically Safe Intrinsically SafeApparatus Applications(% )

Switching 32.0%mechanical switches 85.0%proximity switches 15.0%

2-wire transmitters 22.0%Thermocouples & RTDs 13.0%Load cells 8.5%Solenoid valves 4.5%Potentiometers 2.5%LEDs 2.0%I/P transducers 2.0%Other devices 13.5%

Total field devices 100.0%

Limiting Energy To The FieldDeviceTo protect the intrinsically safeapparatus in a hazardous area, anenergy-limiting device must beinstalled. This is commonly referredto as an intrinsically safe associatedapparatus or barrier. Under normalconditions, the device is passiveand allows the intrinsically safeapparatus to function properly.Under fault conditions, it protectsthe field circuit by preventing excessvoltage and current from reachingthe hazardous area. The basiccircuit diagram for an intrinsicallysafe barrier is shown in Figure 2.

There are three components to abarrier that limit current and voltage:a resistor, at least two zener diodes,and a fuse. The resistor limits thecurrent to a specific value known asthe short circuit current, Isc. Thezener diode limits the voltage to avalue referred to as open circuitvoltage, Voc. The fuse will blowwhen the diode conducts. Thisinterrupts the circuit, which preventsthe diode from burning and allowingexcess voltage to reach thehazardous area. There always are atleast two zener diodes in parallel ineach intrinsically safe barrier. If onediode should fail, the other willoperate providing completeprotection.

A simple analogy is a restriction in awater pipe with an overpressureshut-off valve. The restrictionprevents too much water fromflowing through the point, just likethe resistor in the barrier limitscurrent. If too much pressure buildsup behind the restriction, theoverpressure shutoff valve turns offall the flow in the pipe. This is similarto what the zener diode and fuse dowith excess voltage. If the inputvoltage exceeds the allowable limit,the diode shorts the input voltage to

ground and the fuse blows, shuttingoff electrical power to the hazardousarea.

When conducting the safetyanalysis of the circuit, it is importantto compare the entity values of theintrinsically safe apparatus againstthe associated apparatus. Theseparameters usually are found on theproduct or in the control wiringdiagram from the manufacturer (seeFigure 3).

Will The Circuit Work?It also is important to make surethat the intrinsically safe circuit willwork under normal conditions. Withthe current-limiting resistor, avoltage drop will occur between theinput and output of the barrier. Thishas to be accounted for in yourcircuit design. In the subsequentarticles in this series, a step-by-stepexplanation will be given on how tocalculate these voltage drops andmake sure that the circuit is safe.

Determining Safe EnergyLevelsVoltage and current limitations areascertained by ignition curves, asseen in Figure 4. A circuit with acombination of 30 V and 150 mAwould fall on the ignition level ofgases in Group A. This combinationof voltage and current could createa spark large enough to ignite themixture of gases and oxygen.Intrinsically safe applications alwaysstay below these curves where theoperating level of energy is about1 watt or less. There are alsocapacitance and inductance curveswhich must be examined inintrinsically safe circuits.

The purpose of this series ofarticles is to simplify the applicationof intrinsic safety. Consider theignition curves to demonstrate apoint about thermocouples.

Z

Associated Apparatus Apparatus(barrier) (field device)

Open circuit voltage Voc ≤ VmaxShort circuit current Isc ≤ ImaxAllowed capacitance Ca ≥ CiAllowed inductance La ≥ Li

Figure 3. Comparison of the entity values ofan intrinsically safe apparatus andassociated apparatus

Figure 4. Ignition curves – resistance

Ign

itio

n C

urr

ent

(A)

Open Circuit Voltage (V)

Groups C and DMethanePropaneEthylene

Groups A and BHydrogen

1010 mA

20 mA

50 mA

100 mA

200 mA

500 mA

1A

2A

5A

20 30 40 50 100 200

Z-132

A thermocouple is classified as asimple device. It will not create orstore enough energy to ignite anymixture of volatile gases. If the energylevel of a typical thermocouplecircuit were plotted on the ignitioncurve in Figure 4, it would not beclose to the ignition levels of themost volatile gases in Group A.

Is the thermocouple which isinstalled in a hazardous area(Figure 5) intrinsically safe? Theanswer is no, because a fault could

occur on the recorder which couldcause excess energy to reach thehazardous area, as seen in Figure 6.To make sure that the circuitremains intrinsically safe, a barrierto limit the energy must be inserted(Figure 7).

The next installment in this serieswill explain how the selection ismade for thermocouples and RTDs,which comprise about 13% of allintrinsically safe applications.

BEHIND THE BYLINEPaul B. Babiarz is marketing managerof intrinsically safe products for Crouse-Hinds. He holds a B.S. from theUniversity of Rochester, an M.S. fromthe University of Michigan, and anM.B.A. from Syracuse University. Hehas more than 13 years of experiencein working in hazardous areas and hasspecialized in intrinsic safety.Copyright Instrument Society ofAmerica. Intech, October, 1992.All Rights Reserved.

NON-HAZARDOUS SIDE HAZARDOUS SIDE

Recorder


Recorder

110 V FAULT explosionpossible

Z-133

Maximum 0.1 volt produced by thermocouple

Intrinsic Safety Circuit Design Cont’d

Figure 7. Thermocouple with barrier

Figure 6. Thermocouple with fault

Figure 5. Thermocouple installed in a hazardous area


RecorderInstrinsically

Safe Barrier

Z

GRD

+

–

ControlRoom

NON-HAZARDOUS SIDE HAZARDOUS SIDECLASS I,II, IIIDIVISION 1GROUPS A-G

Thermocouples are simple devices.Do not need approval

Use same type of wire

Use same type of wire

Note: Use consistent wiring

Safety BarrierParameters

VN: 2.5 V Ri: 71 Ω

V

V

RTD

Voltmeter

+-

Figure 1. Current use of intrinsically safe apparatus in hazardous areas.

Intrinsic Safety CircuitDesign–Part 2

Paul S. Babiarz

When thermocouples and RTD’s(resistance temperature devices)are installed in hazardous areas,barriers are required to make theircircuits intrinsically safe. Theseintrinsic safety barriers preventexcess energy from possible faultson the safe side from reaching thehazardous area. Without thebarriers, excessive heat or sparksproduced by the fault conditioncould ignite volatile gases orcombustible dusts.

Hundreds of different barriers areavailable from North Americansuppliers. The multitude of productscan give control engineersnightmares as they try to select theproper barrier for commoninstrumentation loops. The searchcan be simplified, however. Onetype of barrier can be selected tomake all thermocouples and RTD’sintrinsically safe so that polarityproblems are avoided andcalculations are not necessary.

Normally, the design of allintrinsically safe circuits centers onone of two approaches: theuniversal approach, which uses auniversal device that often isisolated so that a ground for safetyis not required; or the engineeredapproach, which uses groundedsafety barriers.

Isolated temperatureconverters. These universaldevices measure temperature inhazardous areas, but at a highercost. (Dispensing with the need for aground is a convenience that maycost two to three times as much asgrounded safety barriers.) Isolatedtemperature converters accept alow-level DC signal from athermocouple or 3-wire RTD andconvert it into a proportional 4-20 mA signal in the safe area.•They also are available with setpoints that trip an on-off signal to

Fault conditions in hazardous-area temperature sensors can be explosive without the properprotection.You can safeguard all of the devices in your application with one type of intrinsicsafety barrier.

Figure 2. Typical values of barrier in thermocouple circuit.

Z-134

the safe side when the temperaturereaches a designated level.These units must be approved asintrinsically safe.

Advantages of isolated temperatureconverters as compared togrounded safety barriers include:• Good signal response• No ground required for safety

• More versatile application• One product for all applications

Disadvantages include:• Larger in size• Requires calibration• More expensive• May not work with all

thermocouples and RTD’s

Intrinsic Safety Barrier

Grounded safety barriers.These are passive devices thatprevent all excess energy from afault occurring on the safe side fromreaching the hazardous area.Under normal conditions, thebarriers allow the circuit to functionproperly by allowing the signals topass between the field device andthe control room. In a faultcondition, the barriers limit voltageand current to levels that are notsufficient enough to ignite gases.For a more detailed explanation,refer to Part 1 of this series.

Advantages of grounded safetybarriers as compared to isolatedtemperature converters include:• Less expensive• Precise signal response• Very small (less than 1⁄2 in. wide)• Simple application • One barrier for all types of

thermocouples and RTD’sDisadvantages include:• Requires ground• Requires some engineering

Examine The BarrierParametersArticles in this series will focus onmethods to select the proper groundedsafety barriers. Before we analyzethermocouple and RTD circuits, weshould examine the functionalparameters necessary to select theproper barrier. These parametersare: polarity of circuit; rated voltageof barrier; and resistance of barrier.

Polarity. The circuit’s polaritymust be known in order to choosethe correct type of barrier. DCbarriers are rated either as positiveor negative. AC barriers can beconnected to circuits with either apositive or negative supply.SIGNAL & RETURN barriers areused for transmitter and switchingapplications. All of these barriersare available in single- ordouble-channel versions. However,because double-channel barrierssave space and money by beingconnected to two legs of a loop,they are becoming the standard.

V

V Voltmeter

A

B

C

Figure 3. 3-wire RTD bridge

V Voltmeter

A

C

BV

Intrinsic Safety Barrier

R1

R2

Note: When R1 = R2, bridge remains balanced

Figure 4. 3-wire RTD bridge with barrier

Rated voltage. Like anyelectrical device, safety barriershave a rated nominal voltage, Vn,referred to as working voltage. Thebarrier’s Vn should be greater thanor equal to the supply to the barrier,much like the rated voltage of alamp must be equal to or greaterthan the supply to it. If the voltagesupply to the barrier is much greaterthan its Vn, the barrier will sense afault. The protective zener diodeswill conduct, causing leakagecurrents and inaccurate signals onthe loop. Most barriers have a ratedworking voltage that guarantees aminimal leakage current from 1 to10 micro amps if it is not exceeded.If the supply voltage to the barrierbecomes too high, the zener diodewill conduct. The resulting highcurrent through the fuse will causethe fuse to blow. Excess supplyvoltage is the main reason whygrounded barriers fail.

Internal resistance. Every safetybarrier has an internal resistance,Ri, that limits the current under faultconditions. Ri also creates a voltagedrop across the barrier.This drop canbe calculated by applying Ohm’slaw, V=IR. Not accounting for thevoltage drop produces the mostproblems in the proper functioningof intrinsically safe systems.

Thermocouple SystemDesign Pointers Polarity. A thermocouple has twowires, each with a positive andnegative polarity. Two single-channelbarriers, each with the properpolarity, could be used. Problemswould occur if the positive leg to thethermocouple were connected tothe negative terminal of the barrier orvice versa. There are two possiblebarrier choices for thermocouplecircuits:

Thermocouple circuit with one positive and one negative lead

1 standard DC barrier, positive polarityand

1 standard DC barrier, negative polarityOR

1 double AC barrier

When barriers and thermocouplesare being installed, the technicianmay forget which wire is positive andwhich is negative. To avoid polarityproblems on the terminals, a doubleAC barrier should be used. Thewires can be connected to eitherterminal and the circuit will functionproperly as long as thermocouplepolarity is maintained throughout.

Rated voltage. A thermocoupleproduces a very small voltage (lessthan 0.1 V). It is connected to avoltmeter which has a high impedanceand which requires a very smallcurrent. Since the thermocoupleproduces such a small voltage,choose a double AC barrier with ahigher rated nominal voltage (Vn). Asurvey of most double AC barriers onthe market shows that they are ratedat low nominal voltages from 1 V andhigher.Select one between 1 and 10 V.

Internal resistance. Since themV signal has a very small currentand is going to a high-impedancevoltmeter, the resistance of thebarrier will not influence circuitfunction. A simple rule of thumb isthat when a signal is going to ahigh-impedance voltmeter, aninternal barrier resistance of lessthan 1000 ohms will not affect themV signal. It usually is goodpractice, however, to select a barrierwith a low resistance in case thecircuit is modified later.

Barrier selection. For properoperation of thermocouples inhazardous areas, select safetybarriers based on the followingparameters:• Barrier type: double-channel AC

barrier to avoid polarity problems• Rated voltage: Barrier Vn > 1V• Internal resistance: barrier with lowest

resistance (less than 110 ohms)

Safety and installation check.Since the thermocouple is a simpledevice, it does not need third-partyapproval. Make sure that the barrierhas the proper approvals forhazardous area locations. Thethermocouple wires will be different

Z-135

Z

from terminal connections on thebarrier. Always use consistent wiringfrom the thermocouple to the barrierand then to the control room. Thiswill cancel any thermocouple effectcaused by the dissimilar metals onthe barrier connection.

RTD System DesignPointersRTD’s come in 2-, 3-, and 4-wireversions. The 3-wire RTD is used inmore than 80% of all applications.The 2-wire version is not asaccurate and is used mostly in theheating, ventilation, and airconditioning industry for set-pointtemperature measurements. The4-wire RTD provides the mostaccurate signal, but is moreexpensive and requires one moreextension wire to the process area.

Understanding RTD accuracy isessential in selecting the correctbarrier. Many RTD measurementsare in the form of a Wheatstonebridge, whose output voltage is afunction of the RTD resistance. Thebridge requires four connectionwires, an external source, and threeresistors that have a balancedtemperature coefficient. The RTDnormally is separated from thebridge by a pair of extension wires.

With a 2-wire RTD, the impedanceof the barrier in series with the RTDwill cause an imbalance on thebridge and will affect the accuracyof the temperature reading. This

GRD

Currentloop

signal

NON-HAZARDOUS SIDE

Item 1

Item 2

HAZARDOUS SIDECLASS I,II, IIIDIVISION 1GROUPS A-G

RTD’s are simple devices.Do not need approval.

RTD

This channel can be used to serve part of loop #2.

Safety BarrierParameters

VN: 2.5 V Rj: 71 Ω

GRD

effect can be minimized by using athird wire to measure the voltage(refer to Figure 3 for this discussion).If wires A and B are perfectlymatched and if the resistance inboth channels of the barrier is thesame, the impedance effects willcancel because each is in anopposite leg of the bridge. The thirdwire, C, acts as a sense lead to thevoltmeter.

Current loop A & B: Polarity. Thecurrent loop to the RTD has apositive and a negative polarity.Possible solutions are similar to thethermocouple:1 standard DC barrier, positive polarity

and1 standard DC barrier, negative polarity

OR1 double AC barrier

Select the double AC barrier toavoid polarity problems. Because itis smaller, it is also less expensive.

Current loop A & B: Ratedvoltage. The constant currentamperage sent to the RTD typicallyis in the micro amp (10-6) level. Themaximum resistance of the mostcommonly used RTD, Pt100 is390 ohms at 1560°C. The voltagedrop across the RTD will be in mV,so the Vn of the RTD loop is similarto the thermocouple. To be safe,select a barrier with a Vn greaterthan 1 V, similar to the Vn of thethermocouple barrier.

Current loop A & B: Internalresistance. The constant currentsource will have a rated maximumload or burden (resistance load itcan drive). Assume that thismaximum load is 500 ohms and themaximum resistance of the RTD atthe highest temperature is 390ohms. Knowing this information, theRi of the barrier can be calculated:

control room ≤ barrier + RTDresistance resistance resistance500 ohms < Ri ohms + 390 ohmsRi < 110 ohms

Current loop A & B: Barrierselection. Use the same barrier thatwas used for the thermocouplecircuit.

Leg C to the voltmeter: Barrierselection. The RTD leg going to thevoltmeter (C) is a millivolt signalsimilar to the thermocouple circuit.The rated voltage, Vn, and internalresistance, Ri, of the barrier willhave the same parameters as thebarriers used in the thermocoupleand current loop of the RTD.Selecting the correct barrier tomake all thermocouples and RTD’sintrinsically safe is not difficult. Usea double-channel AC barrier with arated voltage greater than 1 voltwith the lowest internal resistance.The double-channel barrier is thelowest cost solution. The AC versionwill avoid any polarity problems. Abarrier with a rated voltage between1 and 10 volts will provide a wideselection which have a lowresistance and are approved for thehazardous areas where thetemperature sensors are located.This single barrier can then be usedto make all thermocouples andRTDs intrinsically safe. And don’tforget, all thermocouples and RTD’sare simple devices, so they do notneed third party approval to beintrinsically safe. When they areconnected to an approvedintrinsically safe barrier, the circuitsare intrinsically safe.

Many temperature sensors areattached to 4-20 mA temperaturetransmitters, which comprise 22%of all intrinsically safe applications.The next article in this series willshow how to make thesetransmitters intrinsically safe.

Copyright Instrument Society ofAmerica. Intech, December, 1992.All Rights Reserved.

Z-136

Paul S. Babiarz

The 80/20 Rule actually is five rulesthat are based on the fact thatcertain practices prevail 80% of thetime, and 20% of applications aremore difficult. This article focuses onhow to choose intrinsically safebarriers when the transmitters areinstalled in hazardous areas for boththe 80% standard category and theremaining 20% more difficultapplications.

The most common way to processand send analog signals in theinstrumentation industry is via4-20 mA transmitters. Transmitterscan be one of the simplest devicesinvolving barriers. However,improper selection of intrinsicallysafe barriers in loops with 4-20 mAtransmitters can introduce too muchimpedance on the circuit and causethe transmitters to functionimproperly at the high end near the 20 mA reading.

Before selecting barriers, examinehow 4-20 mA analog circuitsfunction. Transmitters convert aphysical measurement such astemperature or pressure into anelectrical signal that can be sentwithout signal modification to a

control system over a long distance.The brains of the system, the DCS,interprets the electrical signal intothe physical measurement. Becausethese analog signals are sent to aDCS, 4-20 mA circuits are calledanalog inputs or A/I. Usingtemperature as an example,examine the function of thetransmitter (Fig. 1).

A power source in the DCS usuallysupplies 24 VDC to the transmitter.The transmitter converts thephysical measurement into anelectrical current signal. Transmittercurrent ranging from 4-20 mA issent back to the DCS. Currentsignals are used to avoid potentialvoltage drops or electricalinterference associated with voltagesignals. However, because the

controller reads a voltage signal, aconversion resistor (most commonly250 ohms) converts the 4-20 mAcurrent range into a voltage signalon the DCS input channel. ApplyingOhm’s Law of V = IR, the controllerhas a 1-to-5 V signal (Table 1).

Assume the temperature span to bemeasured is from 0°C to 100°C. Thetransmitter is calibrated so that a 4mA signal equals the low reading of0° and a 20 mA signal equals thehigh reading of 100°. The DCS thenruns the signal through a conversionresistor which can be placed eitheron the supply (+) or return (-) leadof the circuit, converting the signalback to a voltage reading.

There are three types of barriers forintrinsically safe transmitterapplications: ungrounded repeaters,grounded repeaters, or groundedsafety barriers. Each has itsadvantages and disadvantages(Table 2).

Ungrounded repeater barriers, alsoknown as galvanically isolated ortransformer-isolated barriers, areused more frequently in Europe

Z-137

Temperature → converted to x multiplied by = converted to mA signal ohm resistor a voltage reading

in the DCS

0°C (min) → 4 mA (0.004 A) x 250 = 1 V

100°C (max) → 20 mA (0.020 A) x 250 = 5 V

Use The 80/20 Rule In Intrinsic Safety Circuit Design

Part 3 of this series on intrinsic safety circuit design describes how to select barriers forintrinsically safe 4-20 mA transmitters. Use the 80/20 Rule to simplify this process.

+24V

250 Ω

DistributedControlSystem

4 – 20 mA2-Wire

Transmitter

SENSOR

4 – 20 mA

Conversion

+

–

+

–

Figure 1. 4-20 mA 2-wire transmitter.

Table 1. Conversion of physical measurement to electrical signals.

than in North America. Repeaterssuit most transmitter applications,but at a higher cost. Grounded orungrounded repeaters supply aconstant regulated voltage of 15 to17 V to the transmitter from a 24 Vsource. The return channel is thenrun through the barrier, whichrepeats it without any appreciableloss in signal. For example, if atransmitter sends 19.6 mA throughthe barrier, it is repeated in thebarrier without any loss so that19.6 mA reaches the control room.Repeaters act like mirrors byretransmitting, or repeating, theanalog signals.

When budget constraints or controlpanel space are importantconsiderations, grounded safetybarriers may be a better choice.

80/20 Rule #1: In North America,most analog circuits areprotected by grounded safetybarriers because of lower costs.

Define the hazardous areawhere the transmitter is located.In North America, these areas aredefined by the National ElectricCode as classes, divisions, andgroups. The class defines the typeof materials that are in thehazardous area. Class I —flammable gases and vapors; ClassII — combustible dusts; Class III —fibers and flyings. Hazardous areasare further broken down into twodivisions. Division 1 means normallyhazardous; Division 2 means notnormally hazardous. The group

designates the type of vapor or dustin the area. Group A — acetylene;Group B — hydrogen; Group C —ethylene; Group D — propane;Group E — metal dust; Group F —coal dust; Group G — grain dust.

Complex devices. Becausetransmitters can store energy, theyare considered complex devices,and must be approved asintrinsically safe. If they arethird-party approved, they haveentity parameters such as Vmax,

Imax, Ci, and Li (see Part 1 of thisseries).

Selection of safety barriers. Theproper barrier must be selected bytwo separate evaluations: one todetermine that the analog circuitfunctions properly at 20 mA, andone to determine that the circuit issafe under fault conditions.

Functional parameters:Type ofsafety barrier, voltage input (Vn),and internal resistance (Ri). Thetype of safety barrier is largelydetermined by the placement of theconversion resistor. If the resistor isplaced on the supply leg of thecircuit, a simple DC positive barriercan be used (Fig. 2).

80/20 Rule #2: Most transmittercircuits have the conversionresistor on the return channel.Use the double channel supplyand return barrier.

The supply channel is constructedlike the positive DC barrier; itprevents a fault on the safe sidefrom transferring excess energy tothe transmitter. The return channelhas two diodes in series which allowthe signal to pass only in onedirection back to the DCS, andprevent any excess fault energyfrom being transferred to thetransmitter. These diodes and thesupply channel have voltage dropswhich must be accounted for in theanalog circuit (Fig. 3).

Z-138

Z

Advantages Disadvantages

Grounded Safety Least expensive Requires ground

Barrier Precise signal response Requires engineering

Very small size

(<1⁄2 in. wide)

Grounded One product can be used More expensive

Repeater Can use transmitters with Requires ground

higher operating voltage Larger in size

Consumes more power

Ungrounded One product can be used Most expensive

Repeater No ground required Larger in size (1 in. wide)

Can use transmitters with Possible radio frequency

higher operating voltage interference

Isolation, if good ground May not be compatible

not available with smart transmitters

Table 2. Advantages and disadvantages of grounded safety barriers, grounded andungrounded repeaters.

+24V250 Ω


ConversionResistor

GRD


+ + + +

––––

IntrinsicallySafe

Transmitter

SENSOR

+

Figure 2. Positive DC barrier.

GRD


+24V

250 Ω


IntrinsicallySafe

Transmitter

SENSOR

ConversionResistor

+ + +

–––

+

–

Figure 3. Supply and return barrier.

Z-139

80/20 Rule #3:The supplyvoltage normally is 24 VDC.

Select the voltage input, Vn.One of the reasons that barriersfail is because the voltage supplyis too high. Use a regulated supplysource with a high end of tolerancethat does not exceed the barrierrating and a low end that is enoughto drive the circuit. A 24 Vdcsource ±1% usually is a goodchoice.

Determine the internalresistance, Ri (also referred toas end-to-end resistance) of thebarrier best suited for yourcircuit. The most criticalcomponent of the barrier selectionis the barrier’s internal resistance.If the resistance is too high, thetransmitter will not work near20 mA. As seen in Table 1 and thefollowing discussion, at 20 mA thevoltage drops across the barrierand the conversion resistor will bethe highest. If the internalresistance is too low, the barrier’sshort circuit current, Isc, mayexceed the transmitter’s entityparameter, Imax.

The easiest way to determine thebarrier’s permitted resistance is tocalculate the total voltage drop onthe circuit. To select the propertransmitter barrier, determine thefollowing:• Hazardous area Groups A-G or

C-G• Placement of the conversion

resistor on either the supply orreturn leg of the circuit

• Size of the conversion resistor(250 ohms is most common)

• Minimum operating voltage of thetransmitter (This figure, alsoreferred to as lift-off voltage, is inthe transmitter data sheet. Mostoperate at a minimum of 12 V orlower.)

• Entity parameters of approvedtransmitter

Case 1. Assume that conditionsare as follows:• Groups A-G• Supply• 250 ohms• 12 V• Vmax = 30 V, Imax = 150 mA, Ci = 0 µF, Li = 0 mHCalculate the maximum allowableresistance of the barrier underworst-case conditions when thetransmitter is sending a 20 mAsignal. The supply is 24 Vdc; thetransmitter requires a minimum of12 V; and the 250 ohm conversion

resistor requires 5 V at 20 mA.Simple subtraction leaves amaximum allowable voltage drop of7 V. Using Ohm’s Law, thisconverts to an internal resistanceof 350 ohms. Allow for a cableresistance of about 10 ohms. Thus,the circuit functions properly with abarrier having an internalresistance of 340 ohms.

Next, to make sure the circuit issafe, verify that the barrier’s entityparameters match the transmitter’sentity parameters. This designoffers the lowest cost solutionwhere two transmitters can beconnected to one double channelbarrier. This circuit arrangementallows one common barrier to beused for most circuits (Fig. 4).

Case 2. Use the sameconditions as in Case 1, exceptchange the placement of theconversion resistor to the returnside, and use the supply andreturn barrier. Voltage drop onthe barrier occurs on both the

supply and return side. Voltagedrop on the return side diodes isabout 0.7 V. This leaves amaximum drop of 6.3 V on thesupply side or a maximumresistance of 305 ohms (allowing10 ohms for cable resistance).Again, verify the entityparameters of the barrier andtransmitter.

80/20 Rule #4:The two solutionsabove cover 80% of alltransmitter applications.

But what happens if the circuit fallsinto the 20% category? Groundedsafety barriers may not work inconditions where a loop-poweredindicator is connected, or wherethe transmitter requires a minimumvoltage greater than 12 V. In thesecases, the easiest solution is touse a repeater barrier. Repeatersprovide a regulated power supplyof 15-17 V to the transmitters andcan drive a conversion resistorload of 750 to 1000 ohms (Fig. 5)

GRD


+24V

250 Ω


IntrinsicallySafe

Transmitter

SENSOR

5 volt loss maximum7 volt loss

12 volt loss

VOLTAGE BALANCE:Transmitter = 12 volts

Resistor = 5 volts Barrier(+ line loss) = 7 volts

Total Supply = 24 volts

24 Supply

+

–

+

–

+

–

+

–

Figure 4. Voltage balance.

+24V

750 - 1000 Ωmax


IntrinsicallySafe

Transmitter

SENSOR

4 – 20 mA

+

–

+

–


RepeaterBarrier

15 - 17V

4 – 20 mA

+

–

+

–

Repeated

ConversionResistor

Figure 5. Repeater barriers.

Z-140

Z

If repeaters still are not the bestsolution, there may be other ways touse grounded safety barriers. Eitherthe impedance in the circuit must bereduced or the voltage must beincreased. If these alternatives areused, recheck the barrier andtransmitter entity parameters tomake sure the circuit is safe.

Reducing Impedance Case 1. Reduce the conversionresistor. As seen in Fig. 2, only twofixed sources of impedance can bereduced: the conversion resistor orthe barrier. One solution is to reducethe conversion resistor to 100 or50 ohms to obtain maximum voltagereadings of 2.0 to 1.0 V respectively.(Example: 20 mA (0.02 A) x100 ohms = 2 V.) This may bepractical for new installations, but itmay not be possible for cases whereadditions are being made to anexisting control system.

Case 2. Select a barrier withlower resistance.

80/20 Rule #5: Many hazardouslocations are classified asGroups C-G.

Ignition curves in Groups C-G allowhigher rated voltages and currentbefore gases ignite (see Part 1 ofthis series, October 1992). Barriersdesigned for hydrogen and othergases classified as Group A or Brequire higher series resistancethan barriers designed for only themore common gases in Groups Cand D. Thus, most intrinsically safeinstruments should have entityparameters (Imax, maximum shortcircuit current) that are higher forGroups C-G. (As a practical matter,most instrument manufacturershave not taken advantage of thisfact.) With the Group C-G ratinghigh-current barriers can be used,which have a lower internalresistance. These barriers havecorresponding lower voltage dropsbut higher Isc (Table 3).

Increasing Voltage SupplyIf the voltage supply is increasedtoo much, the barrier may sense afault and the fuse could blow,interrupting the circuit. Someallowance can be tolerated forincreasing the voltage supply onbarriers with a nominal ratedvoltage of 24 VDC.

Case 1: Resistor on the supplyside. When transmitters are firstenergized, they transmit 4 mA forcalibrating zero readings. Therealways is at least a 1 V drop acrossthe resistor before the supplyreaches the barrier. The voltagesupply could be increased to 25 to26 V without the barrier sensing afault condition. This would allow 1 to2 additional volts on the circuit.

Case 2: Resistor on the returnside. Since the resistor is on thereturn side, the barriers receive thetotal voltage supply. Since thiscircuit is more sensitive to voltageincreases, be careful aboutincreasing the supply above thebarrier's nominal rated voltage, Vn.

Before the zener diodes in thebarriers reach their rated voltage,there may be some leakage currentthat could affect the transmittersignals. Diode leakage currentvalues ranging from 1 to 10µA arelisted by the barrier manufacturers.In Case 1, this could mean that thecurrent signal could be deformed bya maximum of 0.025% at 4 mA(1 µA/4 mA).

When the resistor is placed on thereturn side, leakage current is onthe supply side and does not affectthe transmitter’s 4-20 mA signal.

Transmitters comprise 22% of allintrinsically safe circuits. The nextarticle will feature discrete inputs,also referred to as switching. Theserepresent 32% or almost one-thirdof all intrinsically safe circuits.

See SIB Series of Intrinsically Safe Transmitters

Copyright Instrument Society ofAmerica. Intech, March, 1993.All Rights Reserved.

Groups Internal Resistance Voltage Drop Short Circuit Open Circuit

(Ri) at 20 mA Current, Isc Voltage, Voc

Barrier #1 A-G 340 ohms 6.8 V 93 mA 28 V

Barrier #2 C-G 140 ohms 2.8 V 213 mA 28 V

Table 3. Typical values of barriers rated for different groups.

Z-141

Making Digital InputsIntrinsically Safe

Part 4 of this series describes how to make a switch intrinsically safe by using a switchamplifier or a grounded safety barrier.

Paul S. Babiarz

Digital inputs constitute almost one-third of all process signals. Theyalso are known as binary, on-off,0/1, or simple switching signalswhere a switch is either opened orclosed. The most commonexamples of these are mechanicalor reed contacts, transistors, limit,float, on-off, and pushbuttonswitches. As defined in paragraph3.12 of the ANSI/ISA-RP12.6-1987,switches are simple devices thatneither generate nor store morethan 1.2 V, 0.1 A, 25 mW, or 20µJ.Since switches are simple devices,they do not have to be approved asintrinsically safe. If they areconnected to an approvedintrinsically safe associatedapparatus (barrier), the circuit isdeemed to be intrinsically safe.

To make a switch intrinsically safe,the user may select a switchamplifier or a safety barrier. A switchamplifier is an intrinsically safe relaythat solves virtually all switchingapplications. However, if power isnot available in the control panel orif panel space is an importantconsideration, a grounded safetybarrier may be a better choice. Thereis not a significant cost savings ofone alternative over the other. Eachhas its own advantages anddisadvantages, as shown in Table 1.

Switch AmplifiersThe most common application isswitching through an intrinsicallysafe relay (Fig. 1). Relays, whichnormally are powered by 110 VACor 24 VDC, have a low voltage andcurrent which are safe at the contactin the hazardous area. When thiscontact is closed, the relay transfersthe signal from the hazardous

location to the non-hazardous side.A closed switch on the hazardousside operates a relay or optocoupleroutput on the non-hazardous side.The signals are electrically isolatedso that grounding is not required.

When proximity switches became apopular means of sensing thepresence of objects and materials,the NAMUR-style sensor wasdeveloped. Contrary to popularopinion, NAMUR is not an approvalstandard. It was organized by theGerman chemical industry todevelop operating standards forproximity switches. A NAMUR-styleproximity switch is a 2-wire DCsensor that operates at 8.2 V withswitch points operating between 1.2to 2.1 mA. This NAMUR standardlater was superseded by theGerman Standard DIN 199234,Measurement And Control:

No

n-I

ntr

insi

cally

Saf

e W

irin

g

INTRINSICALLY SAFE WIRING

To Field Circuits

IntrinsicSafety Barrier








Figure 1. Switch amplifier — 2 channels.

Electrical Sensors Used ForIntrinsically Safe 2-Wire DCSystems. Because these switchesrequired a remote amplifier foroperation, most switch amplifiersstandardized on an intrinsically safevoltage of 8.2 V and current of 8 mAat the contacts in hazardous areas.This provided enough power tooperate NAMUR-style proximityswitches safely.

The amplifiers are sensitive enoughto detect closed contacts incorrosive or abusive areas. Despitethe fact that the intrinsically safevoltage and current at the contactsare very low, most modern switchamplifiers will detect a closedcontact when the resistance of thecircuit is less than 3000 ohms.Intrinsically safe switches can belocated a long distance from theswitch amplifiers and still functionproperly.

Switch amplifiers are available withtwo different output contacts to thesafe side, relays and optocouplers.The more commonly used relayversions are applied in slow speedswitching to operate smaller pumps,motors, or other electrical devices.Optocouplers are transistorsoperated by photo diodes to closethe output contacts. These outputshave lower contact ratings but analmost infinite switching capability.Optocouplers are used for switchingback to a DCS or for high-speedcounting operations up to thousandsof times per second (KHz).

Switching Through SafetyBarriersWhen a 110 V supply is notavailable in the control panel, safetybarriers frequently are used fordigital inputs back to a DCS. Thereare two methods of switching:current sourcing or current sinking.Both of these methods can use thesame types of barriers that were

used for transmitters (see Part 3 ofthis series).

The current sourcing method ofswitching in Fig. 2 could use thesame signal and return barrier thatwas used for 4-20 mA transmitters.The voltage to the switch is suppliedthrough the supply channel. Thesecond channel is used for signalreturn. A closed switch will close thecontact in the DCS. Most digitalinput signals operate with 24 V and10 mA. If the same barrier is usedfor switching as 4-20 mAtransmitters, there will be about a 3to 4 V drop across the barrier.

The barrier used for current sinkingswitching can be a single-channelDC barrier as seen in Fig. 3. Whenthe switch is open, the DCS inputwill sense 24 V. When the switch isclosed, the DCS will recognize alower voltage. This lower voltage iscalculated as a voltage dividercircuit.

Make sure the rated voltage of thebarrier, Vn, is equal to or greater

than the voltage supply. Since mostswitching uses 24 VDC, select abarrier rated at 24 V. The internalresistance of the barrier is not ascritical since the current in digitalinputs usually is very small.However, it always is good practiceto select a barrier with lowresistance. Check the approvals ofthe barriers to make sure that theyare rated for the proper hazardousarea group location.

Intrinsically safe relays, also referredto as switch amplifiers, can beapplied universally for all digitalinputs. However, if safety barriersare used, the same barriers used tomake analog inputs intrinsically safecan be used for either currentsourcing or current sinkingswitching.

The next article in this series willexplain how to make digital outputsintrinsically safe.

Z-142

Z


Simple application Needs power supplyNo ground required Larger in sizeNo internal resistanceLEDs to indicate power and monitor operationsSensitive to detect closed contacts in corrosive areas


Smaller size Requires groundingDoes not require power supply Has internal resistance

Switch Amplifiers

Safety Barriers


ONLY THESE WIRESAREINTRINSICALLYSAFE

IntrinsicSafetyBarrier

Potential ofGround Loops



IntrinsicallySafe

Apparatus

DistributedControl

System

Figure 2. Current sourcing switching. Figure 3. Current sinking switching.

Table 1. Advantages and disadvantages of switch amplifiers and safety barriers.

Copyright Instrument Society of America.Intech, April, 1993. All Rights Reserved.

Paul S. Babiarz

Digital outputs refer to closedcontacts in a distributed controlsystem (DCS). They transfer avoltage to a process area to operatea field device. The two mostcommonly used digital output fielddevices, solenoid valves and LEDdisplays, can easily be madeintrinsically safe. For solenoidvalves, the same types of barriersare used that make analog anddigital inputs (transmitters andswitch contacts) intrinsically safe.LED’s may require a different barrier.

There is good news and bad newsfor making circuits (or loops)containing solenoid valvesintrinsically safe. The bad news isthat unlike transmitters which haveminimum operating voltages, valvemanufacturers often describe theirvalves with a nominal operatingcurrent or voltage. To select theproper barrier one needs to knowthe minimum operating characteristicsunder the most extreme conditions.Without these characteristics it canbe quite difficult to select a barrierthat will allow the circuit to functionproperly and still meet the entityparameters of the valves. Conditionsthat may affect the operatingcharacteristics are high ambienttemperatures, position of theactuator, and length of cable runs.

The good news is that there are onlya handful of approved intrinsicallysafe solenoid valves to choose from.For this article, manufacturers testedtheir intrinsically safe valves with themost common barrier used in analogand digital input circuits — the 24 Vdcbarrier with a resistance equal to orless than 350 ohms (Fig. 1).

To determine the correct barrier, startwith the basics. Since most digitaloutput circuits operate with 24 Vdcswitched on the positive side, use apositive DC barrier rated at 24 Vdc.Knowing the minimum operatingcurrent of the valve and the internalimpedance of the coil, you cancalculate the maximum allowableimpedance for the barrier and thecable.

Z-143

Intrinsically Safe OutputsMade Easy

Part 5 of this series explains how to make solenoid valves, LED’s, and I/P transducers intrinsically safe.

+

–

SolenoidValve

+

–

NON-HAZARDOUS SIDE HAZARDOUS SIDECLASS I, II, IIIDIVISION 1GROUPS A-G

GRD

+

–

Solenoid valves needentity approval

+

DigitalOutput

D/O

24 V

Typical Safety BarrierParameters

VN: 24 V Ri:≤ 350

VN = Rated voltageRi = Internal resistance

Typical Safety BarrierTypical Safety BarrierParameters Parameters

VVNN: 24 V R: 24 V Rii::≤≤ 350 350

VVNN = Rated voltage = Rated voltageRRi i = Internal resistance= Internal resistance

For example, assume a valve has aminimum operating current of 28 mAand a coil impedance of 400 ohms.The maximum allowable impedanceof the circuit is 857 ohms (24/.028 =857).If the internal impedance of thesolenoid coil is 400 ohms, theallowable impedance of the barrierand cable would be 457 ohms(857-400 = 457). The resistance ofone mile of #18 AWG wire at 60°Cis about 40 ohms (resistance of#18 AWG wire at 60°C is 0.00737ohms/ft.). This makes the maximumresistance of the barrier 457-40 =417 ohms.Selecting the barrier now is simple:1. Select a simple DC positive barrier.

(The rated voltage should be 24 V.)2. Calculate the maximum allowable

resistance of the barrier as in theexample.

3.Confirm that the entity parameters of the solenoid valve match thoseof the barrier (refer to Part 1 of this series).

Associated Apparatus Apparatus(barrier) (field device)

Open circuit voltage Voc ≤ VmaxShort circuit current Isc ≤ ImaxAllowed capacitance Ca ≥ CiAllowed inductance La ≥ Li

LED’sLED’s (light emitting diodes) aresimple devices since they do notstore energy (capacitance orinductance); therefore, they do notneed to be approved. However, theystill must be used with safetybarriers to make circuits intrinsicallysafe. Typical LED’s are rated at 24,18, 12, or 6 V and operate at about

25 mA. Since there will always be avoltage drop across the barrier, thebest application is to choose anLED rated at less than 24 VDC. Usea barrier rated at 24 V, then subtractthe rated voltage of the LED. Thisdifference is the allowable voltagedrop on the barrier at the ratedcurrent. Use Ohm’s Law (V = IR) tocalculate the internal impedance ofthe barrier. Example:• LED rated at 12 V at 25 mA• Allowable voltage drop 12 V

(24-12 = 12)• Internal impedance of the barrier

= 480 ohms (12/.025 = 480)Choose a 24 V positive DC barrierwith an internal impedance of about480 ohms (Fig. 2).

Analog OutputsAnalog outputs refer to I/Ptransducers, also known as I/P’s(pronounced “Ida Pease”). An I/Ptransducer produces a pneumaticoutput proportional to the electricalcurrent input that it receives. Themore current that is applied to thetransducer, the more air pressure isallowed into the system to drive adevice. As opposed to a solenoidvalve which is either in an opened orclosed position, a transducer is aproportional valve. I/P transducersare referred to as analog outputsbecause a variable output, thecurrent signal, is sent from the DCSto the transducer.

I/P transducers need entityapproval. They act like resistors inthe circuit, so three facts must beknown to select the correct barrier:transducer impedance; maximumburden of the driver that sends thecurrent signal; and transducer entityvalues. Burden, rated in ohms,measures the maximum load theDCS can drive. To select the barrier,use the following characteristics:• Transducer impedance is 150 ohms• Burden of the drive is 1000 ohms

The barrier must have an internalresistance less than 850 ohms(1000-150 = 850). Verify the ratedvoltage of the barrier by calculatingthe voltage drop of the circuit. Forexample, use the same barrier andcable values as in the solenoid valveexample. The total impedance(impedance of barrier + transducer+ cable) of the circuit would be

Z-144

Z

+

–

LED Pilot Light


GRD

+

–

25 mA

12 volt drop across barrier(480 x .025)

12 V

LED pilot light is a simpledevice; does not need

approval

+

DigitalOutput

D/O

24 V

VN: 24 V Ri: 480 Ω


VN = Rated voltageRi = Internal resistance

VVNN: 24 V R: 24 V Rii: 480 : 480 ΩΩ

Typical Safety BarrierTypical Safety BarrierParametersParameters

VVNN = Rated voltage = Rated voltageRRii = Internal resistance= Internal resistance

Figure 2. LED pilot light.

+

–

VN ≥ 12 V Ri ≥150 Ω


VN = Rated voltageRi= Internal resistance

VVN N ≥≥ 12 V R 12 V Ri i ≥≥150 150 ΩΩ

Typical Safety BarrierTypical Safety BarrierParameters Parameters

VVNN = Rated voltage = Rated voltageRRii= Internal resistance= Internal resistance

I/PTransducer

+

–


GRD

+

–

+ 4-20 mA

I/P transducers needentity approval

AnalogOutput

A/O

Single Channel DC Barrier

Figure 3. 4-20 mA I/P transducer.

540 ohms (350 + 150 + 40). At themaximum current of 20 mA, thevoltage drop would be 10.8 V(540 x 0.20 = 10.8). Select abarrier rated equal to or higherthan 10.8 V. A barrier rated at 12 Vor higher with an internalresistance of 150 ohms also wouldbe a good choice (Fig. 3). Confirmthat the entity parameters of thebarrier correspond with those ofthe transducer.

This series of articles has shownhow the most commonapplications of temperaturemeasurements and analog ordigital inputs/outputs can be madeintrinsically safe with a few intrinsicsafety barriers. Selection is simple:

1. Determine if the field device is asimple or nonsimple (energy

storing) device that needsapproval and has entityparameters.

2. Select the type of barrierneeded to protect the individualungrounded lines of the circuit.Normally, temperature sensorsuse an AC barrier. For analoginputs and current sourcingswitching, use the supply andreturn barrier. The remainder(analog and digital outputs andsome switching circuits) requireDC barriers.

3. Select a barrier with a ratedvoltage equal to or greater thanthe voltage of the circuit.

4. Confirm that the internalresistance of the barrier willallow enough voltage for the fielddevice to operate properly.

5. Confirm that the entityparameters of the barrier matchthose of the field device.

Use Table 1 as a guide in selectinggrounded safety barriers. Therewill always be exceptions to theseguidelines, so verify your selectionwith the manufacturer of thebarriers or field devices.

The last installment in this serieswill discuss the general rules ofgrounding, installation, andmaintenance of intrinsically safesystems.

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Device Barrier Rated Internal NotesType Voltage Resistance (IT = INTECH)

Thermocouples AC >1 V <1000* Thermocouples are simple devices; do not need approval.

RTD’s AC >1 V <1000* RTD’s are simple devices; do not need approval.

Digital inputs switch Dry contacts are simple amplifiers devices; do not need approval.

D/I - current supply & 24 350** Dry contacts are simple sourcing return devices; do not need approval.

D/I - current DC 24 350** Dry contacts are simplesinking devices; do not need approval.

A/I supply & 24 350 Transmitters need approval.transmitters return Check entity parameters.

Conversion resistor of 250 ohms is on negative side.Minimum lift-off voltage of transmitter is 12 or less.

A/I transmitters DC 24 350 Same, except conversionresistor is on + side.

D/O solenoid DC 24 350 Solenoid valves need approval.valves Check entity parameters.

A/O transducers DC >12 >150 Transducers need approval.Check entity parameters andDCS burden.

* Select a barrier with a low resistance.

** Other barriers with a different resistance can be used. However, these barriers match those of the analog inputs.

Table 1. Guide to selecting grounded safety barriers.

Copyright Instrument Society of America.Intech, September, 1993. All RightsReserved.

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Installing Intrinsically SafeSystems

Part 6 of this series summarizes the major points of barrier replacement, wiring, installation,grounding, sealing, maintenance, and troubleshooting of intrinsically safe systems.

Paul S. Babiarz

We have shown how an intrinsicallysafe circuit is designed for mostcommon applications. Now theintrinsically safe system must beproperly installed and provisionsmust be made to maintain andtroubleshoot it. These proceduresare discussed in detail in Article 504of the National Electrical Code(NEC) and the ANSI/ISARP 12.6-1987 RecommendedPractice — Installation ofIntrinsically Safe Systems ForHazardous (Classified) Locations.

WiringIntrinsically safe circuits may bewired in the same manner ascomparable circuits installed forunclassified locations with twoexceptions summarized asseparation and identification. Thesewiring practices are simple andclear; however, they often areoverlooked and are the source ofpotential problems.

The intrinsically safe conductorsmust be separated from all otherwiring by placing them in separateconduits or by a separation of2 inches of air space. Within anenclosure the conductors can beseparated by a grounded metal orinsulated partition (Fig. 1).

No

n-I

ntr

insi

cally

Saf

e W

irin

g

INTRINSICALLY SAFE WIRING

To ControlRoom Circuits

To Field Circuits









Figure 2 . Barrier installation.

Figure 1. Suggested panel arrangement using separate wireways.


ONLY THESE WIRESAREINTRINSICALLYSAFE


Intrinsically safe wiring may be lightblue when no other conductorscolored light blue are used. Theraceways, cable trays, open wiring,and terminal boxes must be labeledIntrinsically Safe Wiring to preventunintentional interference with thecircuits. The spacing between thelabels should not exceed 25 ft.

Barrier InstallationThe barriers normally are installedin a dust- and moisture-free NEMA4 or 12 enclosure located in thenonhazardous area. Only the barrieroutputs are intrinsically safe.Conductive dust or moisture couldlessen the required distance of 2 in.between intrinsically safe andnonintrinsically safe conductors(Fig. 2). The enclosure should be asclose as possible to the hazardousarea to minimize cable runs andincreased capacitance of the circuit.If they are installed in a hazardousarea, they must be in the properenclosure suited for that area.

GroundingFirst determine if the intrinsicallysafe barriers used in the system aregrounded or isolated. The isolatedbarriers normally are larger, moreexpensive, and do not require aground for safety. The groundedsafety barriers are smaller and lessexpensive, but require a ground todivert the excess energy. The mainrules of grounding intrinsically safesystems are:• The ground path must have less

than 1 ohm of resistance from thefurthest barrier to the maingrounding electrode.

• The grounding conductor must bea minimum 12 AWG.

• All ground path connections mustbe secure, permanent, visible, andaccessible for routine inspection.

• A separate isolated groundconductor normally is requiredsince the normal protectiveground conductor (green oryellow/green wire) may not be atthe same ground potentialbecause of the voltage drop fromfault currents in other equipment.

• For installations designed toCanadian standards, theCanadian Electrical Code(Appendix F) recommendsredundant grounding conductors.

A poor grounding system can

influence the function of the systemby creating noise on the circuit ormodifying the signals. Fig. 3 showsan improperly grounded system.The numerous grounding pointscreate ground loops which canmodify the signals and induce strayvoltages into the intrinsically safecircuits. The correct method ofgrounding is shown in Fig. 4 whereall the grounds are tied together atone single point in the system.

SealingThe requirements for sealingintrinsically safe circuits have beendiscussed by a panel of experts andpublished in “Seals for IntrinsicallySafe Circuits,” EC&M, September1992, pp. 48-49. The panel’sconclusion is that seals are requiredto prevent the transmission of gasesand vapors from the hazardous areato the nonhazardous area, not toprevent passage of flames fromexplosions. Explosion-proof sealsare not required as long as there issome other mechanical means ofpreventing the passage of gasessuch as positive pressure in thecontrol room and/or application ofan approved mastic at cableterminations and between the cableand raceway. Many expertsgenerally agree that a commerciallyavailable silicon caulk is a suitablemastic which would minimize thepassage of gases. This must,however, be acceptable to theauthority having jurisdiction.

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Potential ofGround Loops



Main Earth Ground

IntrinsicallySafe

Apparatus

DistributedControl

System

Figure 3. Unacceptable grounding.

Figure 4. Acceptable grounding.

Single Ground Point



Main Earth Ground

Distributed Control System Intrinsically

SafeApparatus

When barriers are installed inexplosion-proof enclosures, whichare located in the hazardous area,explosion-proof seals are requiredon the enclosure (Fig. 5). Sinceother conduits containingnonintrinsically safe conductorsbetween the hazardous andnonhazardous areas requireexplosion-proof seals, it is goodpractice to maintain consistency andinstall explosion-proof seals on theconduits containing intrinsically safeconductors also. The exception tothis would be where multiconductorshielded cable is used. This cablemay be difficult to seal in someexplosion-proof fittings. However, itwill be necessary to seal both thecable terminations and between thecable and raceway to minimize thepassage of gases, vapors, or dust.

MaintenanceNo special maintenance ofintrinsically safe systems is

required. Once a year the barriersshould be checked to ensure thatthe connections are tight, the ground wiring has less than oneohm of resistance, and the barriersare free from moisture and dirt.Check the panel and conduits forseparation and identification of theintrinsically safe wiring. Never testthe barrier with an ohmmeter orother test instrument while it isconnected in the circuit (Fig. 6). This bypasses the barrierand could induce voltages into theintrinsically safe wiring.

TroubleshootingIf the intrinsic safety circuit does notoperate properly once it iscompleted and energized, followthese troubleshooting guidelines:• Make sure the connections are

tight.• Check the wiring to the

appropriate terminals against thecontrol wiring diagram. A control

wiring diagram is defined by theNEC as “a drawing or otherdocument provided by themanufacturer of the intrinsicallysafe or associated apparatus thatdetails the allowedinterconnections between theintrinsically safe and associatedapparatus.” These diagrams areeasier to obtain than in the past.Make sure that one of themanufacturers provides not onlydiagrams which show theinterconnections between the fielddevice and barriers, but alsowiring diagrams whichdemonstrate that the circuitfunctions properly and is safe bycomparing the safety parametersof the field device and the barriers.

• Make sure the circuit is powered.• Check to see if the resistance in

the barrier is too high for thecircuit. As stated in the previousarticles in this series, circuits areanalyzed for the proper loopresistance (barrier and cable) andsupply voltages. If the circuit doesnot operate properly, check thecircuit against the design in thecontrol wiring diagram.

• Check for a blown barrier fuse.This is accomplished bydisconnecting the barrier from thecircuit and measuring theend-to-end resistance of thebarrier. If the ohmmeter registersan infinite resistance, the fuse inthe barrier is blown. The fuse hasopened because of a fault in thecircuit, so reevaluate the entirecircuit before reinstalling a newbarrier.

Barrier ReplacementIf the barrier’s fuse has opened, itusually is the result of excessivevoltage being applied to the barrier.This causes the diode to conduct,which results in high current in thefuse. After determining the cause ofthe excess voltage, the barrier mustbe replaced. The procedure is todisconnect the wiring from thesafety barriers in the proper order ofnonhazardous terminal first,hazardous terminals next, and theground last. Cover the bare wireends with tape, replace the barrier,and then reverse the procedure tomount the new barrier. Always installthe ground first and disconnect theground last.

Copyright Instrument Society of America.Intech, October, 1993. All Rights Reserved.

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IntrinsicallySafe Seal

Explosion Proof Seal


DistributedControl

System

IntrinsicallySafe

Apparatus

Explosion ProofEnclosure


Testmeter

NEVER DO THIS!

Figure 5. Mounting in a hazardous area.

Figure 6. The barrier should never be tested with an ohmmeter or other instrument while it isconnected in circuit.

GETTING STARTED-A CHECKLIST How many inputs need to be recorded?What types of inputs need to berecorded?Voltage and sensitivityThermocouples RTD’s

Do different input types need to berecorded in the same unit?

What type of recording is required?Continuous

Multiplex scanning (what minimumscan cycle is required?)

Is a communciation interface required?To transmit measured data to acomputer

For remote setup of recorderTo connect to an external printer

Is recorder to be bench style or panelmounting?What type of instrument power isavailable?Is log-type recording desirable instead

of/in addition to trend recording?

Is color differentiation available fortrend lines? Is message printing required? Is the recorder to perform alarmfunctions? How many setpoints per channel?What types of alarms: threshold, ratedelta? Are physical relay contacts availablefor external alarm output? Number required

SIGNAL INPUTSAvailable input types Typical process recorders acceptanalog dc voltage inputs,thermocouple, or RTD temperatureinputs or dry contact status input.

Signal processing Linear scaling (conversion toengineering units) Thermocouple characterizationDifference calculation Square root calculation

HIGHER-LEVEL FUNCTIONSIntelligenceMath functions: +, -, x, ÷, square root,absolute value, logarithm, exponentialfunctions, max, min, time average,group average, summantion, (max-min), standard deviation, andintegration.

Programming methodFront panelRemote (downloaded)

Communications RS-232C: serial point to point, 50 feetcable length maximum at 9600 baud;GPIB (IEEE-488): parallel (20 metersystem cable length maximum, 2 meter

distance between devices, up to 14devices per controller); RS-422A/RS-485:Balanced/unbalanced, serial, up to 32devices per system, cable length canextend to 1.2 km at 9600 baud.

HARD COPY AND DISPLAYRecording methodGalvanometer movementServoStepper-drivenFixed arrayWriting methodCapillary ink

Disposable felt-tip ink cartridges

Dot printing: ink ribbon cassette orpressure-sensitive paper Thermal-moving head or stationarylinear array Rotating ink wheel

The most popular methods havebecome disposable ink cartridges forcontinuous (drag pen) recording, andmulticolor ink ribbon cassette for dot-printing multipoint recording. Thesewriting methods use an economicaltype of paper which is not sensitive toroutine handling and does not requirespecial storage considerations.

Chart types For process recorders there arebasically two types of charts, Z-fold orroll. Z-fold has become a predominantchoice for process applications due tothe ease of review of past traceswithout disrupting active recording.Chart speeds Fixed or programmable

Features Continuous Writing Multipoint Printing method Wet ink Thermal Mechanical ThermalMarking element Felt-tip or capillary Thermal array with High-speed wire Impact dot matrix Thermal matrix with

drag pen heat-sensitive paper dot with multicolor with pressure- heat-sensitive paperribbon sensitive paper

Multicolor trending Multicolor trending Single color trending Multicolor trending Single color Single color trendingenhances chart makes readability enhances chart trending makes makes readabilityreadability difficult when trend readability readability difficult difficult when trend

lines cross or are in when trend lines lines cross or are inclose proximity cross or are in close proximity

close proximityAbility to capture fast- Yes Yes No No Nochanging signalsSpecial chart paper No Temperature-sensitive No Pressure-sensitive Temperature-sensitiverequired nature of paper can nature of paper nature of paper can

cause problems in can create cause problems inapplication of problems in application of recorderrecorder and storage handling and and storage of chartsof charts storage of charts

Z-149

Selecting A Recorder

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Z

Chart annotation Tag printingDigital printingList printing Alarm printing Prints in engineering units Message printing Scale printing Channel identifier (numeric oralphanumeric) Date and time Chart speed Snapshot digital measured values

For continuous writing recorders, theannotation is accomplished by aseparate writing pen so that traceinformation is not lost.

For dot-printing recorders, theannotation is done by the dot-printer,with either single-dot or full characterprinting with each traverse of theprinthead, depending on whether theinstrument is performing analogtrending or log reporting.

Chart widths100 mm180 mm250 mm

Visual indicators Analog bargraph indication (% of fullscale) Analog scale indication (% of fullscale) Digital channel number andmeasured value Alarm statusEngineering units

Recorder setup Until the advent of themicroprocessor, recorders werededicated to measuring only the typeof input signal and only the spanspecified at the time of order. Tochange input signal type and/ormeasuring span, hardware changeswere required. Presently, recordersare available in which input signaltype, measuring span, tag and unitdesignators can conveniently be setin by the user. The recorder setup isdone by a keypad or, if theinstrument has a communicationinterface, by means of a computerkeyboard or downloading of acomputer file.

Modes Normal: Monitoring at set scaninterval and trending at set chartspeed, or logging at set intervals

Print on alarm: Monitoring at setscan interval but not trending orlogging until an alarm conditionoccurs

Change on alarm: Trending orlogging at a base chart speed or log

internal when no alarm conditionexists, automactically switching toalternate chart speed or log intervalwhen an alarm condition exists

RECORDER DEFINITIONS Hybrid recorder: A recorder thatcombines analog trendrepresentation and digital measuredvalue printing on the same chartpaper, without disruption of trend

printing.

Servo balancing: A means ofpositioning the pen of a drag penrecorder. Null-balance operation hasno current flow at balance, nullifyingthe effect of lead resistance.Conventional servo balancingrecorders use contact mechanismsin the feedback loop and brushes inthe servo motor. New technologyallows the use of a noncontact penpositioning transducer and abrushless dc servo motor.

Scanning recorder: A multi-pointrecorder that scans all of its inputs toobtain new measured data every settime period (usually 2 to 6 seconds).Printing for all points is often

performed during each cycle of theprinting mechanism.

Multi-color printing: A recorder thatrecords trend traces in more thanone color to make traces easier todifferentiate. Drag pen recorders usea different color for each pen (usuallyfour pens maximum). Mulit-pointrecorders typically record in sixcolors.

Linear scaling: Recording of avoltage input in terms of theengineering variable, such astemperature, that the voltagerepresents. Transformation is Y(variable to be recorded) = mX (slopex input signal) + b (Y intercept).

Pen offset compensation: Intraditional multiple input drag penrecorders, each pen can travel thefull width of the recording chart. Inorder to do so, the pens must bephysically offset from one another.This puts the different pen traces ondifferent time lines of the chart. Byplacing the measured data of thefront-most pen(s) into a buffer anddelaying their printing, the traces canbe synchronized to the same timeline, thereby compensating for theiroffset.

Accuracy: The closeness to theactual signal that the measuredvalue or trend position takes, statedas either a percentage of full scale orpercent of reading. Separateaccuracy statements are typicallyprovided for measuring andrecording functions.

Tag ID: A means of designating atrace or digital measured value by analphanumeric identifier instead of anumeric identifier. Typically availablewith up to seven characters.

Digital printing: Printing of theprecise measured numerical valuesfor the various channels, along withtheir channel identifiers. Digitalprinting usually occurs in a margin ofthe chart so as not to interrupt trendrecording.

Log report: A printout of precisemeasured numerical values for thevarious channels, along with theirchannel identifiers. Typically prints infull character height per print cycle.During trending, prints on demand,resuming trending automatically.When trending is not being used,

prints at a preselected time interval.May also include alarm statusindication.

Courtesy of Johnson YokogawaCorporation. ®

Z-151

INTRODUCTIONIEEE-488 refers to the Institute of Electrical andElectronics Engineers (IEEE) Standard number 488.This standard was first established in 1978, 13 yearsafter Hewlett-Packard (HP) of Palo Alto, CA, beganwork to enable its broad range of instruments tocommunicate with one another and with “host”computers.

At the time of its development, IEEE-488 wasparticularly well-suited for instrument applications whencompared with the alternatives. In essence, IEEE-488comprises a “bus on a cable,” providing both a paralleldata transfer path on eight lines and eight dedicatedcontrol lines. Given the demands of the times, itsnominal 1 Mbyte/sec maximum data transfer rateseemed quite adequate; even today, IEEE-488 issufficiently powerful for many highly sophisticated anddemanding applications.

However, IEEE-488, as originally defined, left someambiguities in the specifics of controller-instrumentinteraction and communication. While these openissues were likely intended to give instrument andcontroller designers some latitude, the result wasconfusion and compatibility problems amonginstruments from different manufacturers.

During the 1980’s, a new layer was added to the IEEE-488 standard, IEEE-488.2. The original standard wasre-designated IEEE-488.1. IEEE-488.2 provides for aminimum set of capabilities among “controllers” and“devices,” as well as for more specific content andstructure of messages and communications protocols.

IEEE-488.2 is fully backward compatible with IEEE-488.1; the use of a “488.2”-compliant controller affordsthe ability to use the new protocols available with“488.2” instruments while retaining the ability tocommunicate with and control “488.1”-compliantinstruments and associated vendor idiosyncrasies.

Today, IEEE-488 is the most widely recognized andused method for communication among scientific andengineering instruments. Major stand-alone generalpurpose instrument vendors include IEEE-488interfaces in their products. Many vertical marketinstrument makers also rely on IEEE-488 for datacommunications and control.

IEEE-488 controllers support a variety of personalcomputers, from the IBM PC/XT/AT and PS/2 andcompatibles to the multifaceted Macintosh family. Someof these controllers are plug-in cards; others areprotocol converters (e.g., SCSI-to-IEEE-488). Allprovide at least IEEE-488.1 in compliance, and agrowing number adhere to “488.2.”

GENERAL INFORMATIONThe IEEE-488 interface, sometimes called the GeneralPurpose Interface Bus (GPIB), is a general purposedigital interface system that can be used to transferdata between two or more devices. It is particularly well-suited for interconnecting computers and instruments.

Some of its key features are:

• Up to 15 devices may be connected to one bus• Total bus length may be up to 20 m and the distance

between devices may be up to 2 m• Communication is digital (as opposed to analog) and

messages are sent one byte (8 bits) at a time• Message transactions are hardware handshaked• Data rates may be up to 1 Mbyte/sec

Mechanical SpecificationsCONNECTORThe IEEE-488 connector is a 24-pin connector. Deviceson the IEEE-488 bus have female receptacles;interconnecting cables have the mating maleconnectors. Connecting cables will typically have maleand female receptacles wired in parallel at eachconnecting head to allow parallel connection of cablesat a device and/or to allow daisychaining betweendevices.

INTERCONNECTION CABLINGAny individual IEEE-488 bus is limited to 15 devicesincluding the controller. However, the IEEE-488specification limits the total length of all cabling used tointerconnect devices on a common bus to 20 m, or 2 mtimes the number of interconnected devices (up to 20 m).Cable lengths between devices may vary, as long astotal cable length does not exceed these restrictions.Devices may be interconnected in a star or lineartopology, or in a combination of the two, as long as thedistance limits are observed. For maximum datatransfer rates, the total cable length should be reducedto 15 m, with the average interdevice cable 1 m or less.

Electrical SpecificationsBUS LINESThe IEEE-488 bus is a multidrop interface in which allconnected devices have access to the bus lines. The 24bus lines group into four categories:

• Data Lines - Eight lines (DIO1 through DIO8) used totransfer information (data and commands) betweendevices on the bus, one byte at a time.

• Handshake Lines - Three lines used to handshakethe transfer of information across the data lines:

DAV: Data ValidNDAC: Not Data AcceptedNRFD: Not Ready for Data

• Bus Management Lines - Five lines used for generalcontrol and coordination of bus activities:

ATN: AttentionI FC: Interface ClearREN: Remote EnableSRQ: Service RequestEOI: End or Identify

• Ground Lines - Eight lines used for shielding andsignal returns:

One ShieldOne General Signal GroundSix logic ground lines paired off with ATN, SRQ,IFC, NDAC, NRFD and DAV

Overview of IEEE-488

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Z

HANDSHAKINGThe IEEE-488 bus uses three handshake lines in a“We're ready - Here's the data - We've got it” sequenceto transfer information across the data bus. Thehandshake protocol assures reliable data transfer at therate determined by the slowest Listener. Thehandshake lines, like all other IEEE-488 lines, areactive low. DAV is controlled by the Active Talker.Before sending any data, the Talker verifies that NDACis asserted (low) which indicates that all Listeners haveaccepted the previous data byte. The Talker thenplaces a byte onto the data lines and waits until NRFDis unasserted (high), indicating that all AddressedListeners are ready to accept the information. WhenNRFD and NDAC are in the proper state, the Talkerasserts DAV (active low) to indicate that the data on thebus is valid. NRFD is used by the Listeners to informthe Talker that they are ready to accept the new data.The Talker must wait for each Listener to unassert thisline (high), which they do at their own rates when theyare ready for more data. This assures that all devicesaccepting the information are ready to receive it. NDAC,also controlled by the Listeners, indicates to the Talkerthat each device addressed to listen has accepted theinformation. Each device releases NDAC (high) at itsown rate, but NDAC does not go high until the slowestListener has accepted the data byte. This type ofhandshaking permits multiple devices to receive datafrom a single data transmitter on the bus. All activereceiving devices participate in the data handshakingon a byte-by-byte basis and operate the NDAC andNRFD lines in a “wired-or” scheme so that the slowestactive device determines the rate at which the datatransfers take place.

IEEE-488 FUNCTIONSWhen information is placed on the data lines, it canrepresent either a data byte or a command. If theAttention bus management line (ATN) is asserted whilethe data is transferred, then the data lines are carryinga multiline command to be received by every busdevice. If ATN is not asserted, then a data byte is beingtransferred, and only the Active Listeners receive thatbyte.

The IEEE-488 bus also has a number of unilinecommands that are carried on a single busmanagement line. For example, the Interface Clear(IFC) line, when asserted, sends the Interface Clearcommand to every bus device, causing each to reset itsIEEE-488 bus interface.

ADDRESSINGThe IEEE-488 standard normally permits up to 15devices to be configured within one system. Each ofthese devices has a unique bus address, a numberfrom 0 to 30. Address limits can be circumventeddirectly by the use of bus expanders or indirectlythrough the use of an isolator or an extender.

A device becomes Addressed to Talk when it receives aTalk Address Group (TAG) multiline command (a bytetransferred with ATN asserted) specifying its own

address from the Active Controller. Similarly, itbecomes Addressed to Listen when it receives a ListenAddress Group (LAG) multiline command. Otheraddress commands include My Talk Address (MTA)and My Listen Address (MLA), which are the TAG andLAG commands of the Active Controller. The secondaryCommand Group (SCG) is used to refer tosubaddresses or subfunctions within a particular device.This permits direct access and control of thesubdevices or subinstruments embedded withincomplex devices or instruments.

THE SYSTEM CONTROLLERThe System Controller, usually a computer with an IEEE-488 board installed, always retains ultimate control of thebus. When the system is first powered up, the SystemController is the Active Controller and controls all bustransactions. The System Controller may Pass Control toa device, making it the New Active Controller, which maythen Pass Control to yet another device. Even if it is notthe Active Controller, the System Controller maintainsexclusive control of the Interface Clear (IFC) and RemoteEnable (REN) bus management lines and can takecontrol of the bus whenever it desires.

IEEE-488.2The IEEE-488.2 standard was developed to simplify thebasic process of communicating with instruments.IEEE488.2 extends the 488 standard with code, formatand protocol standardization and serves to resolveissues left open in 488.1.

IEEE-488.2 details preferred implementation of many ofthe issues that were either optional or unspecified on thefirst standard. IEEE-488.1 covers the key physical issues(connector type, bus length, maximum number ofinstruments, etc.), electrical issues (open collector TTL,tristate) and low-level protocols (device addressing,control passing and data handshaking/timing). Four basicdevice functions (Talker, Listener, Controller and SystemController) are specified, as are capability subsets foreach type of device.

A number of items not covered by 488.1 can causeproblems for the test engineer, particularly regardingequipment compatibility and data corruption.

For example, 488.1 does not cover these specifications:

• Minimum Device Capability RequirementsNo minimum set of requirements is mandated in IEEE-488.1 for Talkers, Listeners, Controllers or SystemControllers. Hence, a device may implement all, or onlysome, of the capability sets set forth in 488.1, givingrise to systems containing devices with varying levelsof abilities.

The Controller, in such a situation, has no guarantee ofa basic communication subset among system devices.This can lead to confusion for the system operator andmiscommunication between devices.

• Data Coding, Formats and Message ProtocolUnder 488.1, the messages transferred between theController and a device are entirely at the discretion of

Z-153

Overview of IEEE-488 Cont’d

the device manufacturer. The use of ASCII, binary orsome other form of data code and the choice ofterminators such as carriage-return or EOI is arbitrary.Also, the sequence of the sending of commands andthe reading of their responses is unspecified and variesfrom instrument to instrument.

• Definition of the Status Byte488.1 defines a status byte and one bit within, but themeaning of the other seven bits is at the discretion ofthe device designer. This forces the user to provide aunique interpretation of each bit of the status byte.Also, the relationship between the status byte and thedevice's other internal status registers is unspecified.

DRIVER SOFTWARE FOR IBM PCGreat variety is found in the software required tocomplete the interface between the user's program andthe IEEE instruments. Two fundamental techniques areused: the DOS device driver and the subroutine library.These are not mutually exclusive, as subroutine librariescan be implemented via a DOS device driver.

DOS DEVICE DRIVERA popular form of device driver used by several IEEE-488 controller providers is the Terminate and StayResident (TSR) DOS device driver approach. In thismethod, the driver code is stored in memory as a TSRand waits for access by an application program, much asBorland’s Sidekick waits for user “hot key” input.OMEGA’s 488 driver establishes a file I/O link with DOS,just as DOS provides file I/O links for system devicessuch as the keyboard/screen, printer or serial port.

These DOS I/O files may be accessed directly fromDOS, from programs with file I/O capability, includingspreadsheets such as Lotus 1-2-3 and Borland's Quattro,and from most programming languages. These filesprovide a direct link to the IEEE-488 bus using HP-styleEnglish language commands. This style of ApplicationsProgram Interface (API) is often referred to as CharacterCommand Language (CCL), as the IEEE commands aresent as ASCII strings to the driver via the API’s file I/Olinks through DOS.

Controlling Instruments from Any LanguageJust as DOS and spreadsheets can access IEEEinstruments directly using the file I/O services providedby DOS for device drivers, most programming languagesalso can use file I/O to quickly and easily access theIEEE-488 bus.

SUBROUTINE IEEE-488 DRIVER INTERFACEAn alternative means of controlling the IEEE-488hardware is via subroutine calls from high levellanguages. This method has the advantage of minimizingthe overhead of DOS device driver services and theASCII message (CCL) parser and interpreter.Disadvantages include the loss of the convenience andeffectiveness of accessing the IEEE-488 bus from a widevariety of applications programs, as well as from DOS.Also, the use of subroutines, even those with easy-to-useHP-style commands, typically requires compiling andlinking to run even simple test codes.

Some IEEE controller implementations on the IBM PCgive the user the choice of subroutine calls or CCL.

IEEE-488 SUBROUTINE CONTROL LIBRARIESThe logical complement to subroutine interfaces for aTSR DOS device driver are subroutine libraries thatdirectly access the IEEE-488 hardware from a high-levellanguage with code that is compiled and linked directlyinto the user’s program. This approach eliminates theDOS device driver, integrating the IEEE-488 controlfunctions directly into the applications program code.This method has the potential for the highestperformance, as it eliminates possible DOS effects onthe speed of commands and data.

MICROSOFT WINDOWS COMPATIBILITYThe growing popularity of the Windows 3.0 GraphicalUser Interface (GUI) is rapidly spreading to test andmeasurement applications. Until 1991, few tools wereavailable for the end user to build Windows applications.Now, tools such as Microsoft's Visual Basic andBorland’s C++ provide GUI development interfaces thatallow users to draw windows and fill them with buttons,scroll bars and dialog boxes. Soon, these tools (and thetools, libraries and utilities that follow) will be widely usedby developers of IEEE-488 test programs. IEEE-488controller package vendors will adapt their offerings to becompatible with Windows, so users will be able to applyWindows solutions to their measurement problems. Asthese new Windows-oriented drivers and packagesdebut, there will undoubtedly be a broad range ofsolutions offered to the end user. It is important to knowand understand what makes Windows and Windowsapplications different from DOS, and what features anIEEE-488 driver should have in order to make the mostof the Windows environment. Users should keep thefollowing issues in mind when reviewing new offerings:

• Is the software written as a Windows application, or is itmerely a port of DOS software?

Windows performs its own memory managementfunctions; typical DOS ports to Windows do not permitWindows to dynamically allocate memory use, which canlead to “Unrecoverable Application Errors.”

As Windows is an event-based system, it providesextensive event handling facilities; Windows applicationsshould take advantage of them.

Windows has no equivalent of the TSR concept usedwith DOS. Although some DOS TSR’s will function whileWindows is running, their operation can be erratic andunpredictable.

• Will the driver support concurrent access of differentperipherals on a single interface by multiple Windowsapplications? Windows’ pseudo muItitasking is one ofits reasons for being.

• Will the driver service multiple bus adaptor boards?

• Is the driver IEEE-488.2 compliant?

®

000 0 (NUL)001 1 A002 2 B003 3 ♥004 4 ♦005 5 ♣006 6 ♠007 7 (BEEP)008 8009 9 (TAB)010 A (LF)011 B (HOME)012 C (FF)013 D (CR)014 E015 F -016 10 I017 11 J018 12 K019 13 L020 14 M021 15 N022 16 O023 17 P024 18 Q025 19 R026 1A S027 1B (ESC)028 1C (RIGHT)029 1D (LEFT)030 1E (UP)031 1F (DOWN)032 20 (SPACE)033 21 !034 22 “035 23 #036 24 $037 25 %038 26 &039 27 ‘040 28 (041 29 )042 2A *043 2B +044 2C ,045 2D -046 2E .047 2F /048 30 0049 31 1

Z-154

Z

050 32 2051 33 3052 34 4053 35 5054 36 6055 37 7056 38 8057 39 9058 3A :059 3B ;060 3C <061 3D =062 3E >063 3F ?064 40 @065 41 A066 42 B067 43 C068 44 D069 45 E070 46 F071 47 G072 48 H073 49 I074 4A J075 4B K076 4C L077 4D M078 4E N079 4F O080 50 P081 51 Q082 52 R083 53 S084 54 T085 55 U086 56 V087 57 W088 58 X089 59 Y090 5A Z091 5B [092 5C \093 5D ]094 5E ^095 5F _096 60 `097 61 A098 62 B099 63 C

ASCII Code Values

ASCII HexValue Value Character


Z-155

150 96 U151 97 U152 98 ò153 99 î154 9A ö155 9B õ156 9C ú157 9D õ158 9E û159 9F ü160 A0 A161 Al I162 A2 O163 A3 U164 A4 §165 A5 §166 A6 ¶167 A7 ß168 A8 ®169 A9 ©170 AA ™171 AB ´172 AC ¨173 AD ≠174 AE Æ175 AF Ø176 B0177 Bl178 B2179 B3180 B4181 B5182 B6183 B7184 B8185 B9186 BA187 BB188 BC189 BD190 BE191 BF192 C0193 C1194 C2195 C3196 C4197 C5198 C6199 C7

100 64 D101 65 E102 66 F103 67 G104 68 H105 69 I106 6A J107 6B K108 6C L109 6D M110 6E N111 6F O112 70 P113 71 Q114 72 R115 73 S116 74 T117 75 U118 76 V119 77 W120 78 X121 79 Y122 7A Z123 7B 124 7C |125 7D 126 7E ~127 7F T128 80 á129 81 ö130 82 E131 83 A132 84 é133 85 A134 86 è135 87 á136 88 E137 89 E138 8A E139 8B I140 8C I141 8D I142 8E é143 8F Å144 90 E145 91 í146 92 í147 93 O148 94 î149 95 O

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ASCII Code Values Cont’d



Hex Binary Decimal Decimal Decimal DecimalNumber Number Digit 000X Digit 00X0 Digit 0X00 Digit X000

0 0000 1 0 0 01 0001 2 16 256 4,0982 0010 3 32 512 8,1923 0011 4 48 768 12,2884 0100 5 64 1,024 16,3845 0101 6 80 1,280 20,4806 0110 7 96 1,536 24,5767 0111 8 112 1,792 28,6728 1000 9 128 2,048 32,7689 1001 10 144 2,304 36,864A 1010 11 160 2,560 40,960B 1011 12 176 2,816 45,056C 1100 13 192 3,072 49,152D 1101 14 208 3,328 53,248E 1110 15 224 3,584 57,344F 1111 16 240 3,840 61,440

Z-156

Z

200 C8201 C9202 CA203 CB204 CC205 CD206 CE207 CF208 D0209 Dl210 D2211 D3212 D4213 D5214 D6215 D7216 D8217 D9218 DA219 DB220 DC221 DD222 DE223 DF224 E0225 El226 E2227 E3

228 E4229 E5230 E6231 E7232 E8233 E9234 EA235 EB236 EC237 ED238 EE239 EF240 F0241 Fl242 F2243 F3244 F4245 F5246 F6247 F7248 F8249 F9250 FA251 FB252 FC253 FD254 FE255 FF (BLANK)

»…GÀÃÕŒœ–—“”‘’÷◊ÿ Ÿ⁄¤‹›fifl‡·‚„

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Hexadecimal Conversion Chart

Z-157

Information being transferredbetween data processing equipmentand peripherals is in the form ofdigital data which is transmitted ineither a serial or parallel mode.Parallel communications are usedmainly for connections between testinstruments or computers andprinters, while serial is often usedbetween computers and otherperipherals.

Serial transmission involves thesending of data one bit at a time,over a single communications line.In contrast, parallel communicationsrequire at least as many lines asthere are bits in a word beingtransmitted (for an 8-bit word, aminimum of 8 lines are needed).Serial transmission is beneficial forlong distance communications,whereas parallel is designed forshort distances or when very hightransmission rates are required.

Standards One of the advantages of a serialsystem is that it lends itself totransmission over telephone lines.The serial digital data can beconverted by modem, placed onto astandard voice-grade telephoneline, and converted back to serialdigital data at the receiving end ofthe line by another modem.

Officially, RS-232 is defined as the“Interface between data terminalequipment and datacommunications equipment usingserial binary data exchange.” Thisdefinition defines data terminalequipment (DTE) as the computer,while data communicationsequipment (DCE) is the modem. Amodem cable has pin-to-pinconnections, and is designed toconnect a DTE device to a DCEdevice.

InterfacesIn addition to communicationsbetween computer equipment overtelephone lines, RS-232 is nowwidely used for connectionsbetween data acquisition devicesand computer systems. As in thedefinition of RS232, the computer isdata transmission equipment (DTE).However, many interface productsare not data communicationsequipment (DCE). Null modemcables are designed for thissituation; rather than having the pin-to-pin connections of modemcables, null modem cables havedifferent internal wiring to allow DTEdevices to communicate with oneanother.

Cabling OptionsRS-232 cables are commonlyavailable with either 4, 9 or 25-pinwiring. The 25-pin cable connectsevery pin; the 9-pin cables do notinclude many of the uncommonlyused connections; 4-pin cablesprovide the bare minimumconnections, and have jumpers toprovide “handshaking” for thosedevices that require it. Thesejumpers connect pins 4, 5 and 8,and also pins 6 and 20.

The advent of the IBM PC AT hascreated a new wrinkle in RS-232communications. Rather thanhaving the standard 25-pinconnector, this computer and manynew expansion boards for pc’sfeature a 9-pin serial port. Toconnect this port to a standard 25-pin port, a 9- to 25-pin adaptor cablemay be utilized, or the user maycreate his own cable specifically forthat purpose.

Selecting a CableThe major considerations inchoosing an RS-232 cable arebased upon the devices to beconnected. First, are you connectingtwo DTE devices (null modemcable) or a DTE device to a DCEdevice (modem cable)? Second,what connectors are required oneach end, male or female, and 25 or9-pin (AT style)? Usually, it isrecommended that the user obtainthe two devices to be connected,and then determine which cable isrequired.

RS-232 SpecificationsTRANSMITTED SIGNAL VOLTAGE LEVELS:

Binary 0: +5 to +15 Vdc (called a“ space” or “on”)Binary 1: -5 to -15 Vdc (called a “mark” or “off”)

RECEIVED SIGNAL VOLTAGE LEVELS:

Binary 0: +3 to +13 VdcBinary 1: -3 to -13 Vdc

DATA FORMAT:Start bit: Binary 0Data: 5, 6, 7 or 8 bitsParity: Odd, even, mark or space(not used with 8-bit data)Stop bit: Binary 1, one or two bits

1 Data Carrier Detect

2 Received Data

3 Transmitted Data

4 Data Terminal Ready

5 Signal Ground

PIN NUMBER

PINNUMBER

PINNUMBER

9-Pin “AT” Style

Pin Assignments 25-Pin Style

Data Set Ready 6

Request to Send 7

Clear to Send 8

Ring Indicator 9

1 Protective Ground 2 Transmitted Data 3 Received Data 4 Request to Send 5 Clear to Send 6 Data Set Ready 7 Signal Ground/Common Return 8 Received Line Signal Detector 9 +Voltage10 -Voltage11 12 Secondary Received Line Signal Detector13 Secondary Clear to Send

Secondary Transmitted Data 14DCE Transmitter Signal Element Timing 15

Secondary Received Data 16Receiver Signal Element Timing 17

18Secondary Request to Send 19

Data Terminal Ready 20Signal Quality Detector 21

Ring Indicator 22Data Signal Rate Selector 23

DTE Transmitter Signal Element Timing 24 25

The RS-232 Standard

Transmission Example

Data Flow

1 1 1 1 1 0 1 1 0 0 0 0 1 0 1 1 1 1

TRAILING IDLEBITS

STOP BIT

CHARACTER“A”

PARITY BIT

LEADINGIDLE BITS

START BIT

®

Z-158

Z

Guidelines for Realizing the

International Temperature Scale of 1990 (ITS-90)

B. W. MangumNational Institute of Standards and Technology

Gaithersburg, MD 20899

and

G. T. FurukawaGuest Scientist

National Institute of Standards and TechnologyGaithersburg, MD 20899

1. INTRODUCTION

The Comité Consultatif de Thermométrie (CCT) is one of eight specialized technical subcommittees of the Comité International des Poids et Mesures (CIPM).The CIPM is a committee of the Conférence Générale des Poids et Mesures (CGPM).These eight subcommittees are:

1 The Comité Consultatif d’Électricité (CCE), established in 1927,2 The Comité Consultatif de Photométrie et Radiométrie (CCPR),

assigned this name in 1971; the previous name was the Comité Consultatif de Photométrie, established in 1933,

3. The Comité Consultatif de Thermométrie (CCT), established in 1937,4. The Comité Consultatif pour la Définition du Métre (CCDM),

established in 1952,5. The Comité Consultatif pour la Définition de la Seconde (CCDS),

established in 1956,6. The Comité Consultatif pour les Étalons de Mesure des Rayonnements

Ionisants (CCEMRI), established in 1958,7. The Comité Consultatif des Unités (CCU), established in 1964, and8. The Comité Consultatif pour la Masse et les grandeurs apparentées

(CCM), established in 1980.

The CCT is composed presently of members from the following laboratories:

1 Amt für Standardisierung, Messwesen und Warenprufung [ASMW], Berlin, DDR,

2. Bureau National de Metrologie, Paris, France: Institut National deMetrologie [INM], du Conservatoire National des Arts et Métiers,

3. Ceskoslovensky Metrologicky Ustav [CSMU], Bratislava Czechoslovakia,

4. National Research Council [NRC], Ottawa, Canada,5. CSIRO, Division of Applied Physics [CSIRO], Lindfield, Australia,6. D.I. Mendeleyev Institute for Metrology [VNIIM), Leningrad, USSR;

Physico-Technical and Radio-Technical Measurements Institute [PRMI], Moscow, USSR,

7. National Institute of Metrology [NIM], Beijing, PRC, 8. Istituto di Metrologia G. Colonnetti [IMGC], Turin, Italy,9. Kamerlingh Onnes Laboratorium [KOL], Leiden, The Netherlands,10. Korea Standards Research Institute [KSRI], Seoul, Korea,

11. National Institute of Standards and Technology [NIST], Gaithersburg, MD, USA,

12. National Physical Laboratory [NPLj, Teddington, UK,13. National Research Laboratory of Metrology [NRLM), Ibaraki, Japan,14. Physikalisch-Technische Bundesanstalt [PTB], Braunschweig, FRG,15. Van Swinden Laboratorium [VSL], Delft, The Netherlands,16. Iowa State University, Ames, Iowa, USA, and17. Bureau International des Poids et Mesures [BIPM], Sevres, France.

Shortly after the adoption of the International Practical Temperature Scale of1968 (IPTS-68) [100], it was realized that the scale had many deficiencies andlimitations. These included its lower limit of 13.81 K, its inaccuracy relativeto thermodynamic temperatures, and its non-uniqueness and irreproducibility,especially in the temperature region from T 68 - 903.89 K (630.74 ˚C) toT68 - 1337.58 K (1064.43 ˚C, the region in which the Pt-10%Rh/Pt thermocouplewas the standard interpolating instrument. Consequently, the CCT undertook thedevelopment of a new scale, and completed it in accordance with Resolution 7 ofthe 18th Conference Generale des Poid et Mesures [29], which met in October 1987(see appendices).

The CCT met 12-14 September 1989 at the Bureau International des Poids et Mesures(BIPM) in its 17th Session [14] and completed the final details of the newtemperature scale, the International Temperature Scale of 1990 (ITS-90) [66,83].The CCT then recommended to the CIPM, which met [84] on 26-28 September 1989 atthe BIPM, that the ITS-90 be adopted and made the official scale (seeappendices). Upon considering this recommendation, the CIPM adopted the newtemperature scale (see appendices), and the ITS-90 became the officialinternational temperature scale on 1 January 1990, the same date on which changesaffecting certain electrical reference standards were implemented [12]. TheITS-90 supersedes the IPTS-68, the International Practical Temperature Scale of1968, Amended Edition of 1975 [IPTS - 68 (75)][101], and the 1976 Provisional 0.5K to 30 K Temperature Scale (EPT-76) [99].

The ITS-90 was implemented at the NIST on 1 January 1990. The purpose of thisdocument is to describe the new scale, to give some guidelines for itsrealization and use, to facilitate its implementation, to give the differencesbetween temperatures on it and those on the IPTS-68(75) and on the EPT-76, andto describe how the NIST realizes the scale.

The ITS-90 extends upward from 0.65 K and temperatures on this scale are in muchbetter agreement with thermodynamic values than are those on the IPTS-68(75) andthe EPT-76. The new scale has subranges and alternative definitions in certainranges that greatly facilitate its use. Furthermore, its continuity, non-uniqueness and reproducibility throughout its ranges are much improved over thecorresponding characteristics of the previous scales. The biggest improvementin reproducibility results from the replacement of thermocouple thermometry withplatinum resistance thermometry in the range 630 ˚C to the freezing-pointtemperature of silver, and with radiation thermometry in the range from thefreezing-point temperature of silver to that of gold.

The change in the temperature scale affects not only technical interests involveddirectly in thermometry but also those involved with other reference standards,

Guidelines for Realizing the ITS-90

Figure 1. The temperature difference (t 90 - t 68)/°C in the range between the triple point ofequilibrium hydrogen (-259.3467 °C) and the freezing point of gold (1064.18°C) [83, 85].

0.4

Tem

per

atu

re d

iffe

ren

ce (

t 90-

t 68)

/°C

t90/°C

-200

-0.2

0

-0.04

-0.02

0

0.02

0

0

-0.01

-0.02

100

200 400

-200 0 200 400

600 800 1000

0.2

0

-0.2

* Reproduced with permission of National Institute of Standards and Technology

Z-159

Guidelines for Realizing the ITS-90 Cont’d

such as electrical standards, that are sensitive to temperature. As examples,standard resistors and standard cells are sensitive to temperature and generallyare maintained in constant-temperature environments, at least in nationalstandards laboratories,. At the present time, the temperatures of thoseenvironments are normally determined with thermometers that were calibrated onthe IPTS-68(75). A given thermodynamic temperature expressed on the ITS-90,however, has a value that is different from that expressed on the IPTS-68(75),except at absolute zero (0 K), at the triple-point temperature of water(273.16 K), and at a few other points at which the temperatures on the two scalesare fortuitously the same . This difference is shown in figure 1 [83]. A tableof differences between temperatures on the ITS-90, i.e., T 90 or T 90,and those onthe IPTS-68(75), i.e. , T 68 or t 68 and those on the EPT-76, T 76, is given in thetext of the ITS-90 and is presented here in table 1. Although temperature valuesexpressed on the two scales are different, the change is only in the expressionof the value of temperature and not in the temperature itself . That is to say,the Kelvin thermodynamic temperature (the hotness) of a material at any givenpoint is independent of the use of any of the ‘practical’ temperature scales.The better the ‘practical’ scale is, the closer the values of temperature on thatscale are to the thermodynamic temperature values. Needless to say, the Kelvinthermodynamic temperature values are experimentally determined, and they may havesignificant error. Since temperature values expressed on the thermodynamic and‘practical’ scales are different, if the temperature of the environment of areference standard is adjusted so that its value when expressed on the ITS-90 hasthe same value as had been used on the IPTS-68(75), there will have been a changeof the thermodynamic temperature and the value of the reference standard willusually change. Of course, one may not want to change the thermodynamictemperature of the reference standard. In that case, the thermodynamictemperature, as expressed an the IPTS-68(75), can simply be expressed on the ITS-90 (a numerical value different from that on the IPTS-68(75)) and the referencestandards will be unaffected. For more details on the effects of the change ofthe temperature scale on electrical standards, see National Institute ofStandards and Technology (NIST) Technical Note 1263 [12].

In addition to the effect on reference standards for measurements, alltemperature-sensitive properties, e.g., tables of thermodynamic properties,that are presently expressed on the IPTS-68(75) may require changes in values.

2. DEFINITION OF THE ITS-90

The ITS-90 was designed by the CCT in such a manner that temperature valuesobtained on it do not deviate from the Kelvin thermodynamic temperature values bymore than the uncertainties of the latter values at the time the ITS-90 wasadopted. Thermodynamic temperature is indicated by the symbol T and has the unitknown as the kelvin, symbol K. The size of the kelvin is defined to be 1/273.16of the thermodynamic temperature of the triple point of water. This definition ofthe Kelvin Thermodynamic Temperature Scale (KTTS) that is based on the value of asingle finite temperature is not new; the CCT proposed it in 1954, the CIPMrecommended it, and the Tenth CGPM adopted it that same year [30].

Because temperatures on previous temperature scales were expressed relative tothe ice point (271.15 K), temperature, symbol t , on the Celsius Temperature Scaleis defined by:

0.10.1 0.30.3 0.50.5 1 3 55 10 30 50 100100 300 500 1000 3000

CalibrationPoints

Bounds of Helium VaporPressure Calibration

Bounds of Helium VaporPressure Thermometry

4HePoint

4He

3He CVGT

CVGT

4He VPEQN

3He VPEQN

SPRT

e-H TP, VP2

e-H 2TP

e-H 2

e-H 2

17K

20.3K

Ne TP

TPO2

Ar TP

H2OTP

HgTP

GaMP

InFP

SnFP

ZnFP

AlFP

AgFP

Au FP

Cu FP

SPRT

Planck'sRadiation Equation

Temperature, K (ITS-90)

5000 10000

Figure 2. A schematic representation of the ITS-90 showing the temperatures of the defining fixed points (or phaseequilibrium states) on the scale and temperature ranges defined by interpolation instruments and equations.

Table 1. Differences between T90 and T68 (and t90 and t68), and between T90 and T76

(T90 - T76) /mK

T90 /K 0 1 2 3 4 5 6 7 8 9

0 -0.1 -0.2 -0.3 -0.4 -0.510 -0.6 -0.7 -0.8 -1.0 -1.1 -1.3 -1.4 -1.6 -1.8 -2.020 -2.2 -2.5 -2.7 -3.0 -3.2 -3.5 -3.8 -4.1

(T90 - T68) /K

T90 / K 0 1 2 3 4 5 6 7 8 9

10 -0.006 -0.003 -0.004 -0.006 -0.008 -0.00920 -0.009 -0.008 -0.007 -0.007 -0.006 -0.005 -0.004 -0.004 -0.005 -0.00630 -0.006 -0.007 -0.008 -0.008 -0.008 -0.007 -0.007 -0.007 -0.006 -0.00640 -0.006 -0.006 -0.006 -0.006 -0.006 -0.007 -0.007 -0.007 -0.006 -0.00650 -0.006 -0.005 -0.005 -0.004 -0.003 -0.002 -0.001 0.000 0.001 0.00260 0.003 0.003 0.004 0.004 0.005 0.005 0.006 0.006 0.007 0.00770 0.007 0.007 0.007 0.007 0.007 0.008 0.008 0.008 0.008 0.00880 0.008 0.008 0.008 0.008 0.008 0.608 0.008 0.008 0.008 0.00890 0.008 0.008 0.008 0.008 0.008 0.008 0.008 0.009 0.009 0.009

T90 /K 0 10 20 30 40 50 60 70 80 90

100 0.009 0.011 0.013 0.014 0.014 0.014 0.014 0.013 0.012 0.012200 0.011 0.010 0.009 0.008 0.007 0.005 0.003 0.001

(T90 - T68) / °C

T90 / °C 0 -10 -20 -30 -40 -50 -60 -70 -80 -90

-100 0.013 0.013 0.014 0.014 0.014 0.013 0.012 0.010 0.008 0.0080 0.000 0.002 0.004 0.006 0.008 0.009 0.010 0.011 0.012 0.012

T90 / °C 0 10 20 30 40 50 60 70 80 90

0 0.000 -0.002 -0.005 -0.007 -0.010 -0.013 -0.016 -0.018 -0.021 -0.024100 -0.026 -0.028 -0.030 -0.032 -0.034 -0.036 -0.037 -0.038 -0.039 -0.039200 -0.040 -0.040 -0.040 -0.040 -0.040 -0.040 -0.040 -0.039 -0.039 -0.039300 -0.039 -0.039 -0.039 -0.040 -0.040 -0.041 -0.042 -0.443 -0.045 -0.046400 -0.048 -0.051 -0.053 -0.056 -0.059 -0.062 -0.065 -0-068 -0.072 -0.075500 -0.079 -0.083 - 0. 087 -0.090 -0.094 -0.098 -0.101 -0.105 -0.106 -0.112600 -0.115 -0.118 -0.122 -0.125 -0.08 -0.03 0.02 0.06 0.11 0.16700 0.20 0.24 0.28 0.31 0.33 0.35 0.36 0.36 0.36 0.35800 0.34 0.32 0.29 0.25 0.22 0.18 0.14 0.10 0.06 0.03900 -0.01 -0.03 -0.06 -0.08 -0.10 -0.12 -0.14 -0.16 -0.17 -0.18

1000 -0.19 -0.20 -0.21 -0.22 -0.23 -0.24 -0.25 -0.25 -0.26 -0.26

T90 / ° C 0 100 200 300 400 500 600 700 800 900

1000 -0.26 -0.30 -0.35 -0.39 -0.44 -0.49 -0.54 -0.60 -0.662000 -0.72 -0.79 -0.85 -0.93 -1.00 -1.07 -1.15 -1.24 -1.32 -1.413000 -1.50 -1.59 -1.69 -1.78 -1.89 -1.99 -2.10 -2.21 -2.32 -2.43

Z-160

Z

t / ˚ C = T/K - 273.15. (1)

The unit of temperature t is the degree Celsius, symbol ˚ C, and it is by definition the same size as the kelvin. A difference of temperature may beexpressed either in kelvins or in degrees Celsius.

Temperatures on the ITS-90 are expressed, in terms of the International KelvinTemperatures, with the symbol, T90, or, in terms of the International Celsius Temperatures, with the symbol t 90. The unit of the temperature T90 is the kelvin,symbol K, and the unit of the temperature t 90 is the degree Celsius, symbol ˚C.The relation between T90 and t 90 is:

t 90/˚C = T90/K - 273.15. (2)

The ITS-90 extends upward from 0.65 K. There are alternative definitions of T90in certain temperature ranges and they have equal status. In measurements of thehighest precision made at the same temperature, the alternative definitions willyield detectable temperature differences. Also, at any given temperature betweendefining f ixed points, dif ferent interpolat ing thermometers that meetthe specifications of the ITS-90 will indicate different temperature values.These latter differences are referred to as the non-uniqueness in the definitionof the ITS-90, The magnitude of the differences that result from these twosources is sufficiently small to be negligible for all practical purposes.

Temperatures on the ITS-90 are defined in terms of equilibrium phase states ofpure substances (defining fixed points), interpolating instruments, and equationsthat relate the measured property of the instruments to T90. The equilibriumphase states of the pure substances and the assigned temperatures used asdefining fixed points of the ITS-90 are listed in table 2. Figure 2 showsschematically the defining phase states and temperature ranges defined by thevarious interpolating instruments and equations. For comparison purposes, wegive in table 3 the defining fixed points, and their assigned temperatures, ofthe ITS-90 and of all the previous internationally agreed-upon scales.

2.1 BETWEEN 0.65 K AND 5.0 K: 3He and 4He VAPOR PRESSURE THERMOMETRY

The ITS-90 is defined between 0.65 K and 3.2 K by the vapor-pressure-temperature relation of 3He, and between 1.25 K and 2.1768 K (the λ point) and between2.1768 K and 5.0 K by the vapor-pressure-temperature relations of 4He. T90 isdefined by the vapor-pressure equations of the form:

9T90/K = A 0 + ∑ Ai [ δn( p/Pa) - B] /C) 1. (3)

i=1

The values of the coefficients A i and of the constants A 0, B and C of the vapor-pressure equations for 3He and 4He are given in table 4.

a e-H 2 indicates equil ibr ium hydrogen, that is, hydrogen with theequilibrium distribution of its ortho and para states at the correspondingtemperatures. Normal hydrogen at room temperature contains 25% para and75% ortho hydrogen.

b VP indicates vapor pressure point or equation; CVGT indicates constantvolume gas thermometer point; TP indicates tr iple point (equi l ibr iumtemperature at which the sol id, l iquid and vapor phases coexist); FPindicates freezing point and MP indicates melting point (the equilibriumtemperatures at which the solid and liquid phases coexist under a pressureof 101,325 Pa, one standard atmosphere). The isotopic composition is thatnaturally occurring.

c Previously, these were secondary fixed points.

d Previously, these were alternative fixed points.

e From reference functions, equations (14) and (22).

Material a Equilibrium State b Temperature W r ( T90) e

T90(K) t 90 (˚C)

He VP 3 to 5 - 270.15 to- 268.15

e-H 2 TP 13.8033 - 259.3467 0.00119007e-H 2 (or He) VP (or CVGT) ≈ 17 ≈- 256.15e-H 2 (or He) VP (or CVGT) ≈ 20.3 ≈- 252.85

Nec TP 24.5561 - 248.5939 0.00844974O2 TP 54.3584 - 218.7916 0.09171804Ar d TP 83.8058 - 189.3442 0.21585975Hgc TP 234.3156 38.8344 0.84414211H2O TP 273.16 0.01 1.00000000Gac MP 302.9146 29.7646 1.11813889In c FP 429.7485 156.5985 1.60980185Snd FP 505.078 231.928 1.89279768Zn FP 692.677 419.527 2.56891730 Al c FP 933.473 660.323 3.37600860Ag FP 1234.93 961.78 4.28642053Au FP 1337.33 1064.18Cuc FP 1357.77 1084.62

Table 3. Comparison of temperatures of fixed points assigned on variousscales. Temperatures are expressed in kelvins on the KTTS or eqviivalent scales

Point NHS a ITS-27 b ITS-48 b IPTS-48 b IPTS-68 IPTS-68(75) EPT-76 ITS-90

Au FP c - 1336.15 1336.15 1336.15 1337.58 1337.58 - 1337.33

Ag FP - 1233.65 1233.95 1233.95 1235.08 1235.08 - 1234.93

Al FP - - - - - - - 933.473

S BP d - 717.75 717.75 717.75 - - - -

Zn FP - - - (692.655) 692.73 692.73 - 692.677

Sn FP - - - - (505.1181) (505.1181) - 505.078

In FP - - - - - - - 429.7485

H2O BP 373 373.15 373.15 373.15 373.15 373.15 - -

Ga TP - - - - - - - 302.9146

H2O TPe - - - (273.16) 273.16 273.16 - 273.16

H2O FP 273 273.15 273.15 - - - - -

Hg TP - - - - - - - 234.3156

02 BPf - 90.18 90.18 90.18 90.188 90.188 - -

Ar TP - - - - - (83.798) - 83.8058O2 TP - - - - 54.361 54.361 - 54.3584

Ne BP - - - - 27.102 27.102 21.102 -24.5561

Ne TP - - - - - - 24.5591

H2 BP - - - - 20.28 20.28 20.2734 20.3

H2 BPg - - - - 17.042 17.042 17.0373 17.0

H2 TP - - - - 13.81 13.81 13.8044 13.8033

Pb SP h - - - - - - 7.1999 -4He BP - - - - - - 4.2221 4.2

In SP - - - - - - 3.4145 -3He BP - - - - - - - 3.2

Al SP - - - - - - 1.1796 -

Zn SP - - - - - - 0.851 -

Cd SP - - - - - - 0.519 -

a NHS = Normal hydrogen scale [25].b For a time, the ice point Was taken to be 273.16 K. Here, the value 273.15 K

was used to convert temperature values in degrees Centigrade or Celsius tokelvins in order to be as consistent as possible throughout the table.

c FP = Freezing point.d BP = Boiling point at 101,325 Pa.e TP = Triple point.f Changed in 1975 to the condensation point.g Reduced-pressure boiling point, at P = 33,330.6 Pa.h SP = Superconductive transition point.

2.2 BETWEEN 3.0 K AND 24.5561 K (THE TRIPLE POINT OF Ne): 3He and 4He CONSTANT VOLUME GAS THERMOMETRY

Between 3.0 K and 24.5561 K, the ITS-90 is defined in terms of the 3He or 4Heconstant volume gas thermometer(CVGT). The thermometer is calibrated at threetemperatures - at the triple point of neon (24.556,1 K), at the triple point ofequilibrium hydrogen (13.8033 K), and at a temperature between 3.0 K and 5.0 K, thevalue of which is determined by using either a 3He or a 4He vapor-pressurethermometer as described in section 2.1.

For a 4He CVGT that is used between 4.2 K and the triple point of neon(24.5561 K), T90 is defined by the equation:

T90 = a + b p + c p2 (4)

where p is the CVGT pressure and a, b, and c are coefficients that are determinedfrom calibrations at the three specified temperatures, but with the additionalrequirement that the calibration with the vapor-pressure thermometer be made ata temperature between 4.2 K and 5.0 K

For a 4He CVGT that is used between 3.0 K and 4.2 K, and for a 3He CVGT that is usedbetween 3.0 K and 24.5561 K, the non-ideality of the gas must be accounted for,using the respective second virial coefficients, B4( T90) or B3( T90). T90 is definedin this range by the equation:

a + b p + cp 2 (5)T90 =

1 + B x ( T90) N/ V

Table 4. Values of the coefficients A 1 and of the constants B and C for the 3He and 4Hevapor-pressure equations and the temperature range for which each equation is valid

Coef. or 3He 4He 5HeConstant 0.65 K to 3.2 K 1.25 K to 2.1768 K 2.1768 K to 5.0 K

A0 1.053 447 1.392 408 3.146 631A1 0.980 106 0.527 153 1.357 655A2 0.676 380 0.166 756 0.413 923

A3 0.372 692 0.050 988 0.091 159A4 0.151 656 0.026 514 0.016 349A5 -0.002 263 0.001 975 0.001 826

A6 0.006 596 -0.017 976 -0.004 325A7 0.088 966 0.005 409 -0.004 973A8 -0.004 770 0.013 259 0

A9 -0.054 943 0 0B 7.3 5.6 10.3C 4.3 2.9 1.9

Table 2. Defining fixed points of the ITS-90

Z-161


where p is the CVGT pressure; a, b, and c are coefficients that are determinedfrom calibrations at the three defining temperatures; Bx( T90) refers to B3( T90) orB4( T90), and N/V is the gas density, in moles per cubic meter, in the CVGT bulb.The values of the second virial coefficients are given by the followingequations:

for 3He,

B3( T90)/m 3mol -1 = [16.69 - 336.98 ( T90/K) -1

+ 91.04 ( T9O/K) -2 - 13.82 ( T90/K) -3 ] 10 -6 , (6)

and for 4He,

B4( T90)/m 3mol -1 = [16.708 - 374.05 ( T90/K) -1 - 383.53 ( T90/K) -2

+ 1799.2 ( T90/K) -3 - 4033.2 ( T90/K) -4 + 3252.8 ( T90/K) -5 ] 10 -6 . (7)

The accuracy of realization of T90 by using a CVGT is dependent upon the CVGTdesign and the gas density used.

2.3 BETWEEN 13.8033 K (THE TRIPLE POINT OF EQUILIBRIUM HYDROGEN) AND 1234.93 K(THE FREEZING POINT OF SILVER): PLATINUM RESISTANCE THERMOMETRY

Between 13.8033 K (-259.3467 ˚C) and l234.93 K (961.78 ˚C),the ITS-90 is defined interms of specified fixed points to which temperature values have been assigned,by resistance ratios of platinum resistance thermometers obtained by calibrationat specified sets of the fixed points, and by reference functions and deviationfunctions of resistance ratios which relate to T90 between the fixed points.(Henceforth, for convenience, the standards type platinum resistancethermometers will be referred to by the acronym SPRT.)

2.3.1 GENERAL RELATION BETWEEN RESISTANCE RATIOS AND T90

Temperatures on the ITS-90 in the above-indicated range are expressed in terms ofthe ratio of the resistance R( T90) at temperature T90 and the resistance R(273.16 K) at the triple-point temperature of water. (Hereinafter, forconvenience, the terms triple-point temperature, freezing-point temperature andmelting-point temperature will be expressed as triple point, freezing point andmelting point, respectively.) The resistance ratio W( T90) is:

W( T90) = R( T90)/ R(273.16 K). (8)

The temperature T90 is calculated from the resistance ratio relation:

W( T90) - W r ( T90) = ∆W( T90) (9)

where W( T90) is the observed value, Wr ( T90) is the value calculated from thereference functions, and ∆W( T90) is the deviation of the observed W( T90) value of theparticular SPRT from the reference function value. The official version of theITS-90 [83] does not indicate the difference [ W( T90) - Wr ( T90)] by ∆W( T90).

Note that in the earlier international scales, W( T) was defined with reference tothe SPRT resistance 273.15K, not 273.16 K .

There are two reference functions Wr ( T90), one for the range 13.8033 K to273.16 K and another for the range 273.15 K to 1234.93 K. These referencefunctions will be described in the discussion of the two ranges (secs. 2.3.3 and2 3 4).

The deviation ∆W( T90) is obtained as a function of T90 for various ranges andsubranges by calibration at specified fixed points. The form of the deviationfunction depends upon the temperature range of calibration.

A schematic representation of the ITS-90 in the range of temperature specifiedfor SPRT’s is given in figure 3. Shown in figure 3 are the temperatures of thedefining fixed points in this region of the scale and the various subrangesspecified by the scale.

2.3.2 SPRT SPECIFICATIONS

The SPRT sensing element must be made from pure platinum and be strain-free. Thefinished SPRT must meet one of the following criteria:

W(302.9146 K) ≥ 1.118 07, or (10)

W(234.3156 K) ≤ 0.844 235. (11)

These criteria are equivalent to a requirement on the slope, namely,

[d W( T90)/d T90] ≥ 3.986 x 10 -3 K-1 at 273.16 K. (12)

An SPRT that is acceptable for use to the freezing point of silver must meet thefollowing additional criterion:

W(1234.93 K) ≥ 4.2844. (13)

The temperature range over which an SPRT can be used depends upon the thermometer design,but no single design of SPRT can be used over the whole temperature range with highaccuracy. For measurements at temperatures from 13.8033 K (-259.3467 ˚C) to429.7485 K (156.5985 ˚C), or perhaps to as high as 505.078 K (231.928 ˚C) ,capsule-type SPRT’s that have a nominal resistance of 25.5 Ω at 273.16 K may beused. Long-stem type SPRT’s of the same nominal resistance may be used in therange from about 77 K to 933.473 K (660.323 ˚C) . For temperatures above about 660˚C and to as high as 1234.93 K (961.78 ˚C), long-stem type SPRT’s having anominal resistance of 0.25 Ω (or possibly 2.5 Ω) at 273.16 K should be used. WhenSPRT’s are used at the highest temperatures, leakage currents through theinsulation supports of the platinum wire become significant and these result Inshunting of the resistor. The effect of this shunting is reduced by using lowvoltages with low resistance SPRT’s.

If the sheath of the long-stem type SPRT is borosilicate glass or stainlesssteel, the SPRT should not be used above the upper calibration temperature limitof 42˚C. If the sheath is Inconel, the upper temperature limit becomes about

10 100Temperature, K (ITS-90)

13.8

033,

e-H

2 T

P

17, e

-H2

VP

20.3

, e-H

2 V

P

24.5

561,

Ne

TP

54.3

584,

O2

TP

83.8

058,

Ar T

P

234.

3156

, Hg

TP

302.

9146

, Ga

MP

429.

7485

, In

FP

505.

078,

Sn

FP

692.

677,

Zn

FP

933.

473,

Al F

P

1234

.93,

Ag

FP

273.16H2O TP

Calibration Points

Interpolation Range

1000 10000

Figure 3. A schematic representation of the ITS-90 in the range specified for the platinumresistance thermometer, showing the various defined subranges and the temperatures of the defining

Constant or Value Constant or ValueCoefficient Coefficient

A0 -2.135 347 29 B 0 0.183 324 722A1 3.183 247 20 B 1 0.240 975 303A2 -1.801 435 97 B 2 0.209 108 771A3 0.717 272 04 B 3 0.190 439 972

A4 0.503 440 27 B 4 0.142 648 498A5 -0.618 993 95 B 5 0.077 993 465A6 -0.053 323 22 B 6 0.012 475 611A7 0.280 213 62 B 7 -0.032 267 127

A8 0.107 152 24 B 8 -0.075 291 522A9 -0.293 028 65 B 9 -0.056 470 670A10 0.044 598 72 B 10 0.076 201 285A11 0.118 686 32 B 11 0.123 893 204

A12 -0.052 481 34 B 12 -0.029 201 193B13 -0.091 173 542B14 0.001 317 696B15 0.026 025 526

C0 2.781 572 54 D 0 439.932 854C1 1.646 509 16 D 1 472.418 020C2 -0.137 143 90 D 2 37.684, 494C3 -0.006 497 67 D 3 7.472 018

C4 -0.002 344 44 D 4 2.920 828C5 0.005 118 68 D 5 0.005, 184C6 0.001 879 82 D 6 -0.963 864C7 -0.002 044 72 D 7 -0.188 732

C8 -0.000 461 22 D 8 0.191 203C9 0.000 457 24 D 9 0.049 025

Z-162

Z

660 ˚ C. If the sheath is fused silica, temperature measurements can be made up to962˚ C.

For measurements up to about 630 ˚ C, mica is just barely adequate as an electricalinsulator for the temperature sensing element and leads of SPRT’s. Starting atabout 500˚C, muscovite mica begins to decompose, evolving water thatelectrically shunts the thermometer resistor, Phlogopite mica is adequatelystable to 630˚C. For measurements up to 962˚C, refractory materials such as fusedsilica and sapphire are used for electrical insulation.

2.3.3 RANGE 13.8033 K TO 273.16 K

In the range 13.8033 K to 273.16 K, the reference function W r (T 90) is given by:

12,n[Wr (T 90)] = A 0 + ∑ Ai ([, n(T 90/273.16 K) + 1.5]/1.5) i (14)

i=I

A specified,, approximate inverse [83] of this equation, equivalent to within± 0.000 1 K, is:

12T90/273.16 K = B 0 + ∑ Bi ([W r (T 90)] 1/6 - 0.65)/0.35 i (15)

i=I

The values of the constants A 0 and B 0, and of the coefficients A i and B i ofequations (14) and (15) are listed in table 5.

If an SPRT is to be used throughout the range from 13.8033 K to 273.16 K, it mustbe calibrated at the triple points of equilibrium hydrogen (13.8033 K), neon(24.5561 K), oxygen (54.3584 K) argon (83.8058 K), mercury (234.3156 k), andwater (273.16 K), and at two additional temperatures close to 17.0 K and 20.3 K.The temperatures of calibration near 17.0 K and 20.3 K maybe determined by usingeither a CVGT as defined in section 2.2 or the specified vapor - pressure -temperature relation of equilibrium hydrogen.

When the CVGT is used, the two temperatures must be within the ranges 16.9 K to17.1 K and 20.2 K to 20.4 K, respectively. When the equilibrium hydrogen vapor-pressure thermometer is used, the two temperatures must be within the ranges17.025 K to 17.045 K and 20.26 K to 20.28 K, respectively. The temperatures ofthe equilibrium hydrogen vapor-pressure thermometer are determined from thevalues of the hydrogen vapor pressure, p, and the equations:

T90/K - 17.035 = (p/kPa - 33.3213)/13.32 (16)

T90/K - 20.27 = (p/kPa - 101.292)/30. (17)

where 13.32 and 30 are, values of -(dp/dT 90)/(kPa/K) at 17.035 K and 20.27 K,respectively.

Depending upon the’ temperature range of use, the SPRT may be calibrated from273.16 K down to 13.8033 K (the triple point of equilibrium hydrogen), down to

24.5561 K (the triple point of neon), down. to 54.3584 K (the triple point ofoxygen), or down to 83.8058 K (the triple point of argon).

The deviation function for calibration over the range 13,8033 K to 273.16 K isgiven by the relation:

5

∆W1(T90) = a 1[W(T 90) - 1] + b 1[W(T 90) - 1] 2 + ∑ c1[, nW(T90)] i+n , (18)

i=I

with n = 2. The coefficients a 1, b 1, and the five c 1 ‘s are obtained by

calibration at all eight of the above temperatures, including that at the triplepoint of water, The values of Wr ,( T90) are obtained from the reference function

[eq (14)].

The official version of the ITS-90 [83] does not indicate the difference[ W( T90) - Wr ( T90)] by ∆ W,( T90), does not use the subscript m, where in eq (18),

m = 1, nor does it label the coefficients a and b with subscript m. However, weadopt this subscript notation to identify the subranges. Additionally, thisnotation is useful when reporting calibration results.

If an SPRT is not to be used over the entire 13.8033 K to 273.16 K range, but itsuse restricted to one of the subranges, the deviation functions and thecalibration points are as follows.

2.3.3.1 SUBRANGE 24.5561 K TO 273.16 K

The deviation function for calibration in the subrange 24.5561 K to 273.16 K isgiven by the relation:

3∆W2 (T 90) a 2[W(T 90) - 1] + b 2[W(T 90) - 1] 2 + ∑ c i [, n[W(T 90)] i+n , (19)

i=I

with n = 0. The coefficients a 2, b 2, and the three, c 1’s are obtained by

calibrating,the SPRT at the triple points of equilibrium hydrogen (13.8033 K),neon (24.5561 K), oxygen (54.35 84 K), argon (81.8058 K), mercury (234.3156 K)and water (273.16 K). The, values of Wr ( T90), are obtained from the reference

function [eq (14)]. Note that for this subrange, temperatures are measured onlydown to the triple point of neon, although the-thermometer must be calibratedat the triple point of equilibrium hydrogen.

2.3.3.2 SUBRANGE 54.3584 K TO 273.16 K

The deviation function for calibration in the subrange 54.3584 K to 273 16 K isgiven by the relation:

∆ W2 ( T90) a 3[ W( T90) - 1] + b 3[ W( T90) - 1] 2 + c i [, nW( T90)] i+n , (20)

with n - 1. The coefficients a 3, b 3, and c 1 are obtained by calibrating the SPRTat the triple points of oxygen (54.3584 K), argon (83.8058 K), mercury(234.3156 K), and water (273.16 K). The values of W r ( T90) are obtained from the

reference function [eq (14)].

2.3.3.3 SUBRANGE 83.8058 K TO 273.16 K

The deviation function for calibration in the subrange 83.8058 K to 273.16 K isgiven-by the relation:

∆ W4 ( T90) a 4[ W( T90) - 1] + b 4[ W( T90) - 1]l nW( T90). (21)

The coefficients a 4 and b 4 are obtained by calibrating the SPRT at the triple

points of argon (83.8058 K), mercury (234.3156 K), and water (273.16 K). Thevalues of W r ( T90) are obtained from the reference function [eq (14)].

2.3.4 RANGE 273.15 K (O˚C) TO 1234.93 K (961.78 ˚C)

In the range 273.15. K. to 12341.93 K, the equation for the reference functionWr ( T90) is given by:

9Wr (T 90) = C 0 + ∑ C1[(T 90/K - 754.15)/481] i (22)

i=I

A specified, approximate inverse [83] of this equation, equivalent to within± 0.000 13 K, is:

9T90/K - 273.15 = D 0 + ∑ Di ([W r (T 90) - 2.64]/1.64] i (23)

i=I

The values of the constants C 0 and D 0 and of the coefficients C i and D i of eqs

(22) and (23) are, listed in table 5.

If the SPRT is to be used over the entire range 273.15 K to 1234.93 K, it must becalibrated at the triple point of water (273.16 K) and at the freezing points oftin (505.078 K), zinc (692.677 K), aluminum (933.473 K), and silver, (1234.93 K).

The deviation function is given by the relation:

∆ W6( T90) = a 6[ W( T90) - 1] + b 6[ W( T90) - 1] 2

+ c 6[ W( T90) - 1] 3 + d[ W( T90) - W(933.473 K)] 2 (24)

The values of a 6, b 6, and c 6 are determined from the measured deviations ∆ W( T90)

of W( T90) from the reference values W,( T90) [obtained from eq (22)] at the

freezing points :of tin (505.078 K), zinc (692.677 K), and aluminum, (933.473 K),ignoring the term involving d. Then, d is determined-from these values of a 6, b 6,

c 6 and the deviation ∆ W6( T90) of W( T90) from the reference value Wi ( T90) at the

freezing point of silver (1234.93 K). The coefficient d is, used only fortemperature measurements in the range from the freezing point of aluminum to thefreezing point of silver. For temperature measurements below the freezing point ofaluminum, d = 0.

SPRT’s may be calibrated for use throughout the whole range 273.15 K to 1234.93 Kor for shorter subranges by calibrations at fixed points between 273.15 K andthe upper limit of 933.473 K (freezing point of aluminum,. 660.323 ˚C), of692.677 K (freezing point of zinc, 419.527 °C), of 505.078 K (freezing point oftin, 231.928 ˚C) of 429.7485 K (freezing point of indium, 156.5985 °C), or of302.9146 K (melting point of gallium, 29.7646 °C).

The deviat ion function ∆ W5( T90 ) wi l l be discussed l i ter in the text.

Table 5. Values of the coefficients, A i , B i , C i and D i , and of the constants A 0,B0, C 0, and D 0 in the reference functions, eqs (14) and (22), and in thefunctions approximating them, given by eqs (15) and (23)

Z-163

If an SPRT is not to be used over the entire 273.15 K to 1234.93 K range, but itsuse restricted to one of the subranges, the deviation functions and thecalibration points are as follows.

2.3.4.1 SUBRANGE 273.15 K (0 ° C) TO 933.473 K (660.323 -C. FREEZING POINT OFALUMINUM)

For an SPRT used throughout the subrange 273.15 K to 933.473 K, the thermometer iscalibrated at the triple point of water (273.6 K) and at the freezing points of tin(505.078 K) zinc (692.677 K), and aluminum (9 33.473 K). The devi ation function isgiven by the relation:

∆W7(T 90) - a 7[W(T 90) - 1] + b 7(W(T 90) _ 1] 2 + C 7(WT90) - 1] 3. (25)

The coefficients a 7, b 7, and C 7, are identical to a 6, b 6, and C 6, respectively, aredetermined from the deviations ∆W(T90) of W(T 90) from the reference values W I ,(T 90) [eq(22)] at the freezing points of tin (505.078 K), zinc (692.677 K), and aluminum(933 . 473 K).

2.3.4.2 SUBRANGE 273.15 K (0 °C) TO 692.677 K (419.527 °C, FREEZING POINT OF ZINC)

For an SPRT used throughout the subrange 273.15 K to 692.677 K, the thermometer iscalibrated at the triple point of water (273.16 K); and at the freezing points of tin(505.078 K) and zinc (692.677 K). The deviation function is given by the relation:

∆W8(T 90) - a 8[W(T 90) - 1]+ b 8[W(T 90) - 1] 2 (26)

The coefficients a 8 and b a are determined from the deviations ∆W(T90) of W(T 90)from the reference values W r (T 90) [eq (22)] at the freezing points of tin (505.078K) and zinc (692.677 K).

2.3.4.3 SUBRANGE 273.15 K (0 °C) TO 505.078 K (231.928 °C. FREEZING POINT OF TIN)

For an SPRT used throughout the subrange 273.15 K to 505.078 K. the thermome ter iscalibrated at the triple point of.water)(273.16 K) , and at the freezing points ofindium (429.7485 K) and tin (505 078 K). The form of the deviation func tion is thesame as that for the subrange 273.15 K to 692.677 K, i.e.,

∆W9(T 90) - a 9[W(T 90) - 1] + b 9(W(T 90) - 1] 2. (27)

The coefficients a 8 and b 8 are determined from the deviations ∆W(T90) of W(T 90) fromthe reference values W r (T 90) [eq (22)] at the freezing points of indium (429.7485 K)and tin (505.078 K).

2.3.4.4 SUBRANGE 273.15 K (0 °C) To 429.7485 K (156.5985 °C, FREEZING POINT OFINDIUM)

For an SPRT used throughout the subrange 273.15 K to 429.7485 K. the thermom eter iscalibrated at the triple point of water (273.16 K) and at the freezing point ofindium (429.7485 K). The deviation function is:

∆W10(T 90) - a 9[W(T 90) -1] (28)

The coefficient a 10 is determined from the deviation ∆W(T90) of W(T 90) from thereference value W r (T 90) [eq (22)] at the freezing point of indium (429.7485 K).

2.3.4.5 SUBRANGE 273.15 K (0 °C) TO 302.9146 K (29.7646 °C. MELTING POINT OFGALLIUM)

For an SPRT used throughout the subrange 273.15 K to 302.9146 K, the the rmometer iscalibrated at the triple point of water (273.16 K) and at the melting point ofgallium (302.9146 K). The deviation function is:

∆W11(T 90) - a 11W(T90) - 1]. (29)

The coefficient a 11 is determined from the deviation ∆W(T90) of W(T 90) from thereference value W r (T 90) [eq (22)] at the melting point of gallium (302.9146 K)

2.3.5 SUBRANGE 234.3156 K (-38.8344 °C. TRIPLE POINT OF MERCURY) TO 302.9146 K(29.7646 THE MELTING POINT OF GALLIUM)

For an SPRT used throughout the subrange 234. 3156 K to 302.9146 K, the thermometeris calibrated at the triple points of mercury (234.3156 K) and water (273.16 K),and at the melting point of gallium (302.9146 K). The form of the deviationfunction is the sameas that for the subrange 273.15 K to 692.677 K, i.e.,

∆W5(T 90) - a 5[W(T 90) - 1] + b 5[W(T 90) -1.] (30)

The coefficients a 5 and b 5 are determined from the deviations ∆W(T90) of W(T 90)from the reference values W r (T 90) at the triple point of mercury (234.3156 K) and atthe melting point of gallium (302.9146 K) The reference values W r (T 90) must becalculated from the appropriate reference function [either eq (14) or eq ( 22)b o t h r e f e r e n c e f u n c t i o n s b e i n g r e q u i r e d t o c o v e r t h i s r a n g e .

2.4 ABOVE 1234.93 K (961.78 °C. FREEZING POINT OF SILVER): RADIATION THER MOMETRYRASED ON PLANCK’S LAW OF RADIATION

At temperatures above 1234.93 K, T 90 is defined by the relation:

Lλ (T 90) exp[c 2/ λT90(X)]-1——————————— - —————————————————Lλ [T 90(X)] exp[c 2/ λT90-1

in which L λ(T 90) and L λ[T 90(X)] are the spectral concentrations of the radiance of ablackbody at wavelength (in vacuum) at T 90 and at T 90(X), respectively. T 90(X)refers to either the silver freezing point [T 90(Ag) - 1234.93 K] , the gold freezingpoint (T 90 (Au) - 1337.33 K], or the copper freezing point [T 90 (Cu) -1357.77 K]. The second radiation constant, C 2 (-hc/k), of Planck’s radiationformula has the value C 2 - 0.0143 88 m-K. Although the freezing-point

temperature of silver is the Junction point of platinum resistance thermometry andradiation thermometry, it is believed that the T 90 values of the freezing pointsof silver, gold and copper are sufficiently self-consistent that the use of any oneof them as the reference temperature T 90(X) will not result in any significantdifference in the measured values of T 90 from what would be obtained if only thesilver freezing point were used.

3. REALIZATION OF THE ITS-90

3.1 VAPOR PRESSURE THERMOMETRY AND GAS THERMOMETRY

3.1.1 REALIZATION OF THE ITS-90 BELOW 273.16 K

The calibration of thermometers below the triple point of argon on the ITS -90, asdefined, is relatively complex It is expected that capsule-type SPRT’s, rhodium-iron resistance thermometers (RIRT’s), and other stable encapsulated resistancethermometers will be calibrated in terms of the defined ITS-90 and then used asreference thermometers to maintain the ITS-90 below about 84 K and used tocalibrate other resistance thermometers by the comparison method. The referencethermometers will be calibrated periodically in terms of the defined ITS-90.

By use of the term "realization of the ITS-90," reference is made to obtai ning theequilibrium states as defined by the scale, to having thermometers in thermalequilibrium with those equilibrium states, and to making accurate measurements andinterpretations of the requisite properties of those thermometers in terms of theITS-90.

Considerable effort has been expended to develop and realize the EPT-76, a scalewhich covered the range 0.5 K to 30 K. This scale has been widely dissem inated amonglow temperature scientists. At NIST, the EPT-76 has been maintained on reference-standard RIRT’s for use in calibrating customer thermometers. Upon introduction ofthe ITS-90, NIST converted the EPT-76 on the reference-standard RIRT’s to the ITS-90using the specified differences [83] between T 90 and T 76, This converted scale isbeing used to calibrate other thermometers until such time that NIST realizes theITS-90 in this temperature region directly as defined. It is recommended thatthose laboratories that have thermometers with calibrations on the EPT-76 adjusttheir T 76 values to conform to T 90 values. When NIST realizes the ITS-90 as definedin this range, the difference between the converted scale on the reference-standard RIRT’s (and, where appropriate, on capsule SPRT’s) and the realizedscale will be determined.

3.1.2 VAPOR PRESSURE THERMOMETRY AND THE CVGT RANGE

For most measurements below about 100 K, better precision can be obtained withcapsule-type SPRT’s than with the long-stem type. In the calibration of SPRT’s,however, long-stem type SPRT’s (immersion-type SPRT’s) can be calibrated easily bya direct immersion process down to the triple point of argon (83.8058 K) by moving theSPRT’s from one fixed-point device to another. Unless capsule-type SPRT’s andother capsule-type thermometers are installed inside long stem-like holders,however, they will require re-installation, and re-wiring whenever differentfixed-point apparatuses are used. (In this document, the phrase “capsule-typethermometers” means encapsulated resistance thermometers of small overal ldimensions.) It is desirable, therefore, to be able to calibrate capsule-typeSPRT’s and other capsule-type thermometers at the argon triple point and below (or,if possible, even at the triple point of water and below since calibrations ofSPRT’s require measurements at the triple point of water) in an integrated"multi-task" (multi- fixed-point) apparatus. Such a multi-task appa ratusrequires, in addition to wells for capsule thermometers (in thermal equilibriumin a "single cryostat block"), means for calibration using 3He, 4He, and e-H 2 vaporpressure thermometry, 3He and 4He CVGT’s, and triple points of e-H 2 Ne, O 2, Ar, Hg,and H 2O - A total of 11 chambers is required if all of the overlappingdefinitions of the ITS-90 are to be evaluated and if a "continuous calibration,"without re-installation and re-wiring of the SPRT’s, is desired from 0.65 K to273.16 K. In addition, unless high pressure sealed cells of the reference gasesare used, tubes to each of the chambers, except those for Hg and H 20, are required.

Since 3He and 4He vapor-pressure and CVGT ranges overlap to a large extentchambers for 4He vapor-pressure measurements and for 4He CVGT measurements could beeliminated and the ITS-90 could still be realized. Also, chambers for e-H 2 vapor-pressure and the e-H 2 triple-point realizations could be combined. The number ofchambers could be reduced further if the cryostat block could be allowed to warmto ambient temperature or higher for exchanging certain of the fixed-pointsubstances, or if it were permissible to perform the calibrations of the capsulethermometers at the triple points of argon, mercury, and water in otherapparatuses, using a long-stem type holder. This procedure, however, wouldrequire a longer time for calibration.

The number of chambers can also be reduced if suitable, highly stable capsulethermometers are available for correlating the scales; for this purpose, thecapsule SPRT’s would be calibrated in another, simpler, fixed-point apparatus. Itis expected that such a set of reference-standard resistance thermometers would becalibrated, and that routine calibrations of customer thermometers on the ITS-90would be by comparison with these reference thermometers. The referencethermometers would be checked occasionally against the defined ITS-90. It is hopedthat resistance thermometer devices will be more reproducible than the ability torealize the defined ITS-90. Depending upon the design of the cryostat, the definedITS-90 may lack the desired reproducibility when real ized in a multi-taskapparatus of high complexity. In order to achieve the best real ization of theITS-90, it may be more practical to limit the number of defining fixed pointsin a single cryostat block.

The greatest problem in realization of the fixed points and in calibrations ofcapsule thermometers is ensuring that the multi-task or a "single-task" cry ostatblock is isothermal. Depending upon the design, a thermal gradient can persist. Thepresence 3He, 4He, e-H 2, Ne, 0 2, and/or Ar gases in their respect ivechambers are expected to be beneficial in making the apparatus isothermal, but, thegases may be a source of thermal oscillation. (In designing an apparatus for lowtemperature gases, provisions should be made to avoid thermal oscillationsin the gas.) The vapor pressures of Ne and Ar are high at their respective triple-point temperatures so that thermal equilibrium should be easily attained at theirtriple points.


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For a practical cryostat block, the 3He and 4He CVGT’s must connect thermally the 3Heand 4He vapor-pressure scales and the fixed points of e-H 2 and Ne. Such a cryostatblock will require six chambers (separate 3He and 4He vapor-pressure chambers,separate 3He and 4He CVGT chambers, e-H 2 vapor-pressure and e-H 2 triple- point chamber,and a Ne chamber) to realize the ITS-90 in the most satisfa ctory manner at and belowthe Ne triple point. This arrangement will permit a direct comparison of thedifferent parts of the scale and/or calibration of thermometers. Since thecombination of 4He vapor-pressure thermometry and 4He constant volume gasthermometry are redundant with 3He vapor-pressure thermo metry and 3He constant volumegas thermometry, the 4He systems are not required. Hence, the number of chambersrequired could be reduced to four and the ITS-90 could still be realized. It shouldbe noted, however, that, depending upon the CVGT filling pressure, the dp/dT of a3He CVGT may be less sensitive than 4He vapor-pressure thermometry. Since SPRT’Scan be calibrated only down to the argon triple-point temperature using the long-stem SPRT apparatus, it would be most practical and useful to include an oxygentriple-point chamber in the low -temperature system, thereby increasing the numberof chambers,to five. Also, since it is highly desirable to overlap calibrationsobtained in a long-stem type SPRT apparatus with those obtained in a low-temperature apparatus, an argon triple-point chamber should be included. Thisincreases the number of chambers for the low temperature apparatus to six.

Although it is desirable to have as few tubes as possible going to the cryo statblock in order to minimize temperature gradients in the block, one must build intothe system enough redundant components to be able to check the system for properand accurate operation. For example, although the CVGT is calibrated at only thetriple-point temperatures of neon and hydrogen and at one point in the 3He or 4He vaporpressure range between 3.0 K and 5.,0 K, the system should have the capability forthe measurement of hydrogen vapor pressures at about 17 K and 20.3 K so thattemperatures measured by means of vapor pressures and by the CVGT may b ec o m p a r e d . O f c o u r s e , i f t h e s y s t e m i s o p e r a t i n g p r o p e r l y , t h etemperatures measured by the two techniques should agree. Similarly, there shouldbe the capability to measure the vapor pressures of both 3He and 4He so thattemperatures measured with the CVGT in the range from 3 K to 5 K and by means of3He and 4He vapor pressures may be compared for agreement. Also, it is desirable todesign the CVGT for absolute gas thermometry measurements; the CVGT can check theconsistency of the ITS-90 from about 3 K to 90 K.

3.1.3 REALIZATION OF THE VAPOR PRESSURE AND CVGT SCALES AT TEMPERATURES BELOW THENEON TRIPLE POINT

Since measurement of pressure is common to both vapor pressure and CVGTmeasurements, it will be discussed later in this section (see sec. 3.1.3.5).

In vapor pressure measurements, it is important that cold spots be absent along thegas-pressure transmitting tube. If cold spots are present, the observed vaporpressure will reflect the temperature of the condensation at the cold spot instead ofthat of the bulk bath. A separate vacuum jacket around the tube will maintain acontinuous heat flux to the sample bulb or bath and should free the tube of anycondensation [24]. The vacuum jacket should also reduce the occurrence ofthermal oscillation in the gas-pressure, sensing tube. If the rmal oscillations dooccur, they may be suppressed by either one or a combination of the following:increasing,the volume of the external gas-pressure space at the ambienttemperature, or by inserting a wad of wool or glass fiber or a piece of yarn in thegas-pressure sensing tube. The thermal oscillations may be suppressed alsoby “tuning” a variable volume device [36]. Thermocouples should be placed along thegas-pressure sensing tube in order to determine temperatures along that tube, thedistribution of those temperatures being required to determine the aerostatichead correction.

The vapor pressure may be determined over the bath of bulk liquid 3He, 4He, or e-H 2

with which the thermometer to be calibrated is in thermal equilibrium. Themeasurement can be made also by using a separate, small sample bulb with which thethermometer is in good thermal contact. The latter method is preferred with therather expensive 3He and with e-H 2 which requires a catalyst for theequilibrium ortho-para conversion of the sample [2,58,91].

3.1.3.1 3He Vapor-Pressure Measurements

Because of the relatively high cost of the sample, vapor-pressure measurements aremade with 3He contained in a small volume of about 5 cm . Likewise, the gas -pressure volume to the manometer should be kept relatively small, but large enoughto avoid large thermomolecular pressure effects and thermal oscillations.Thermomolecular-pressure-effect corrections depend on the sensing tube diameter,surface condition of the tube, temperature difference, and pressure [49,71,102].As mentioned above, thermal oscillations can be reduced by varying the gas-pressure volume at the ambient temperature or by introducing a wad of fiber oryarn (cotton, wool, or glass) in the gas-pressure tube.

In the past, 3He contained significant amounts of 4He and the observed vaporpressures of 3He required corrections for its presence. In recent years,however, 3He samples of 99.9995% purity have become available, eliminating therequirement for such corrections. At 0.65 K, the vapor pressure and thetemperature derivative of the vapor pressure are 115.9 Pa and 1.08 Pa/mK,respectively. At the upper limit of 3.2 K, the vapor pressure and the temperature derivative of the vapor pressure are 101,662.1 Pa and 106.83 Pa/mK,respectively. The required pressure resolution that corresponds to 0.1 mK ofvapor-pressure measurements varies from 0.108 Pa at 0.65 K to 10.7 Pa at 3.2 K.

Since the amount of 3He in the cryostat is small, and since the amount of 4He usedin cool ing is relat ively large, every effort should be made to avoidcontamination of the sample of 3He by the 4He through diffusion, particularlythrough any glass parts of the apparatus.

The sample bulb should contain enough 3He that the liquid surface temperature andthe cryostat block temperature can be correlated with the observed vapor pressure.The temperature of the cryostat block must be checked for consistency with theobserved dp/dT of the vapor pressure at the temperature of measurement.

Aerostatic-head corrections depend upon the density of the gas in the pressure-transmitting gas tube. Thermocouples must be distributed along the tube in order tomeasure the temperatures required for calculation of these corrections.

3.1.3.2 4He Vapor-Pressure Measurements

Since liquid 4He can be obtained easily, the vapor pressure can be determinedabove a bath of the liquid in which an apparatus containing the thermometer is immersed. or a technique using a smal l bulb of 4He sample, wi th thethermometer in good thermal contact, can be employed. The lower end of the gas-pressure tube should have a small orifice in order to reduce superfluid 4He filmflow at temperatures below 2.1768 K [61,91]. The 4He sample bulb must be inthermal equilibrium with the cryostat block. The cryostat block temperatureshould be checked for consistency with the observed dp/,dT of the va por pressureat the temperature of measurement.

At the lower temperature limit of 1.25 K, the vapor pressure of 4He is 114.7 Paand the temperature derivative of the vapor pressure is 0.76 Pa/.K. At theupper limit of 5 K, the vapor pressure and, the temperature derivative of thevapor pressure of 4He are 1946.29.7 Pa and 146.53 Pa/mK, respectively. Therequired pressure resolutions of the vapor pressure that corresponds to 0.1 mKare 0.076 Pa at 1.25 K and 14.7 Pa at 5.0 K [37,38].

3.1.3.3 e-H 2. Vapor Pressure Measurements

The equilibrium composition of the two molecular states of hydrogen (ortho andpara) is temperature dependent. The room temperature composition, about 75% orthoand 25% -para, is referred to as normal hydrogen (n-H 2). On liquefaction, thecomposition slowly changes toward the equilibrium composition corresponding toits temperature. ~ In the process, the heat of transition is released, resultingin the evaporation of some hydrogen. A catalyst, such as activated ferrichydroxide, hastens the equilibration. The catalyst must be placed in the samplechamber in order to ensure that the hydrogen has the appropriate equilibrium composition. Most of the conversion must be made before collectingthe liquid in the sample chamber since the heat of conversion (1664 J/mol) fromthe ortho to the -para,molecular state is larger than the heat of vaporization(900 J/mol) of normal hydrogen. The normal boiling point of e-H 2 (equilibriumcomposition: 0.21% ortho and 99.79% -para) is about 0.12 K lower than that ofn-H 2. The temperatures near 17.035 K and 20.27 K are determined from vapor-pressure measurements near 33,,321.3 Pa and 101,292 Pa, respectively [2,31,58].

3.1.3.4 Constant Volume Gas Thermometry

Some of the following precautions and corrections that are applicable to absoluteconstant-volume gas thermometry should be included in the calibration of the CVGTat the three specified temperatures of calibration:

1. The volume of the gas bulb should be sufficiently large relative to the gas-pressure-line volume to minimize the error in correcting for the "dead space."On the other hand, the diameter of the gas-pressure line should not be so smallas to cause large thermomolecular pressure corrections.

2. The temperature coefficient of volume expansion and the pressure expansion ofthe gas bulb should be known accurately. (It is desirable to check the calibration by using the,CVGT ih the absolute mode.)

Material T90 Pressure Effect of Fixed Point

K Pa - 1 mK/(meter of liquid)x108*

e-H2 TP 13.8033 34 0.25Ne TP 24.5561 16 1.9O2 TP 54.3584 12 1.5Ar TP 83.8058 25 3.3Hg TP 234.3156 5.4 7.1H2O TP 273.16 -7.5 -0.73Ga HP 302.9146 -2.0 -1.2In FP 429.7485 4.9 3.3Sn FP 505.078 3.3 2.2Zn FP 692.677 4.3 2.7Al FP 933.473 7.0 1.6Ag FP 1234.93 6.0 5.4Au FP 1337.33 6.1 10.Cu FP 1357.77 3.3 2.6

*Equivalent to millikelvins per standard atmosphere.

3. In order to be able to calculate the aerostatic head correction, thetemperature distribution along the connecting gas-presure transmitting tube(capillary) must be known. That temperature distribution may be determined by placing thermocouples along the tube.

4. The gas-bulb filling pressure should be sufficiently high to give anadequate dp/dT for measurement, but not so high as to require large correctionsfor non-ideality of the gas.

5. Higher pressures reduce the thermomolecular pressure gradients in the connecting gas-pressure tube.

6. The effect of adsorption can be reduced by designing the gas bulb so thatthe volume is large relative to the surface and by polishing the inside surfaceof the bulb.

For opt imiz ing the CVGT design, the ideal gas law may be appl ied.Differentiating the ideal gas relation,

Table 6. The effect of pressure on the temperatures of the defining fixed points.The reference pressure for the equil ibr ium states of freezing and melting points is one standard atmosphere (101,325 Pa). Triple points have thevapor pressure of the material when the solid, liquid and vapor phases are presentin equilibrium.

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pV = nRT, (32)

yields

dp/dT R n/ V, (33)

where p is the pressure of n moles of gas contained in a volume of V m 3.

Equation (33) shows that the d p/d T sensitivity of the CVGT is directly related tothe gas density n/V . Expressing the gas constant R as 8.31441 Nm/mol • K or8.31441 Nm 3/(M 2•mol•K), the sensitivity d p/d T can be expressed in the units Pa/K.Thus,

dp/d T = 8.31441( n/V ) Pa/K, (34)

where n/V is given in mol/m 3. If a gas bulb of 1000 cm 3 is filled to fouratmospheres at 273.16 K, n/V would be approximately 178 mol/m 3, and dp/dTbecomes 1484 Pa/K. Since the resolution of many high quality mercury-manometersystems is about 0.03 Pa to 0.2 Pa, the temperature resolution is about 0.03 mKto 0.1 mK. It is to be noted that since

p/T = Rn/ V, (35)

the sensitivity d p/d T is “constant,: independent of the gas bulb volume, as longas the gas density at the filling temperature is constant. Hence, the gas-bulbvolume and the gas filling pressure should be chosen so that errors from theeffect of dead space, gas non-ideality effects and other effects are negligiblysmall. See references [6,13,49,60].

3.1.3.5 Pressure Measurements

Efforts have been made to minimize the requirement of highly precise andaccurate pressure measurements in the realization of the defining fixed pointsof the ITS-90 . The fixed points involving freezing and melting requireknowledge of the pressure only within the significance of the relative ly smallpressure effect ( cf. table 6). Accurate pressure measurements are required,however, to realize the vapor-pressure-temperature scales of 3He and 4He in therange 0.65 K to 5.0 K, and to realize the vapor-pressure-temperature scale of e-H2 close to 17.035 K and 20.27 K. To realize the CVGT scale using 3He or 4He gasin the range 3.0 K to the triple point of neon (24.5561 K), only accuratepressure-ratio measurements are required.

3.1.3.5.1 Mercury Manometry

Mercury manometry requires precise determination of the difference in height ofthe two mercury surfaces in a U-tube manometer. Traditionally, cathetometers havebeen used with a smallest imprecision of ab t 2 Pa. In recent years , the levelshave been sensed, in conjunction with length standards, by capacitive andinterferome tric. methods . The resolution of such mercury manometry systems isabout 0.05 Pa [19,50, 5 2,81] . (Note : the NIST manometry resolution has beenreported [50] to be about 0.0013 Pa.) For accurate pressure measurements, it isnecessary to know the density of mercury (which is pressure and temperaturedependent), the capillary depression at the mercury meniscus, the vapor pressureof mercury, the aerostatic head difference of the pressure transmitting gas orgases, and the local acceleration due to gravity. At one standard atmosphere,uncertainties as of absolute pressure measurements of about 3 ppm and pressureratios of about 1 ppm have been reported. See references [19,50,52,81].

3.1.3.5.2 Oil Manometry

The techniques and the requirements of oil manometry are similar to those ofmercury manometry.

3.1.3.5.3 Piston Gauges (Pressure Balances)

The pressure balanced by a dead-weight piston gauge is obtained from the mass ofthe piston and the applied weights, and the effective area of the freely rotatingpiston inside a closely-fitting cylinder. For determination of the absolutepressure, the gauge must be enclosed and evacuated by a high capacity pumpingsystem to minimize the back pressure from the gas leaking between the piston andthe cylinder [13,60,81,96]. The local acceleration due to gravity must be knownaccurately. Corrections must be applied for the effect of the streaming gas andfor any back pressure. It is advisable to check the readings of the piston gaugeagainst a primary mercury manometer. Also, the variation of the effective areawith pressure must be determined with a mercury manometer. The aerostatic head ofthe manometry system will change as gas leaks between the piston and the cylindercausing the piston to sink deeper into the cylinder. The position of the pistonmay be maintained by automatically pumping more gas into the system. Aresolution of 1 ppm [13] and an certainty of about 15 ppm have been reported inthe pressure range 2 kPa to 200 kPa [63,81].

3.1.3.5.4 D iaphragm Pressure Detector

The diaphragm pressure detector consists of a thin metal disk clamped undertension between two flat electrodes which form two capacitors, with the diskcommon to both capacitors. Any pressure differential across the metal diskcauses the disk to deflect , increasing the capacitance on one side whiledecreasing the capacitance on the other side. This change is detected bycapacitance bridge techniques. Instruments for absolute pressure measurements areavai lable; however, they require periodic recal ibrat ions to achieveuncertainties of 1 to 5 parts in 10 4 of the readings.

The diaphragm pressure detector is used in high precision manometry as pressurebalance detectors, i.e. , with the pressures equal on both sides of thediaphragm. The diaphragm pressure balance detector separates the gas of theapparatus (vapor pressure apparatus or GVGT) from the counter-balancing gas ofwhich the pressure is determined.

The resolution of diaphragm gauges has been reported [13] to be about 0.002 Pa.Instability due to different pressures, hysteresis temperature effects,andother causes may decrease the resolution ion to 0.02 Pa in actual pressuremeasurements [13].

3.1.3.5.5 Thermolecular Pressure Difference

Thermolecular pressure differences occur at low gas pressures in tubes withtemperature gradients when the tube diameter is not much larger than the meanfree path of the gas. The pressure difference depends upon the gas, thetemperature of the gas, the diameter of the tube, the tube material, and thesurface condit ion of the tube. The best procedure is either to use asufficiently large tube to minimize the thermomolecular pressure difference orto experimentally determine the difference by comparing the pressures between thesmall diameter tube being used in the cryostat and a large diameter tube[49,71,102]

3.2 REALIZATION OF THE FIXED POINTS OF THE ITS-90

3.2.1 EFFECT OF IMPURITIES

Except for the vapor-pressure-temperature points of helium and equilibriumhydrogen, the fixed points of the ITS-90 are freezing points. melting points,or triple points. The vapor-pressure measurements with 3He, 4He, and e-Hz must be performed with sufficiently pure samples to minimize the effect ofimpurities. The principal components of air impurity would be frozen. Neon inhydrogen, however, causes positive deviations from ideal behavior [93,97). In thevapor pressure measurements of 4He, it is very likely that the He will bepure but 3He may contain some 4He. For such a circumstance, Roberts, Sherman andSydoriak described a procedure for correcting for the presence of 4He in 3He[90].

The temperatures of freezing points (liquid-solid or liquid-solid-vaporequilibrium points) of substances are usually lowered by the presence of animpurity. This sometimes, however, is not the case when that impurity issoluble in both the liquid and the solid phases of the major component. If agiven impurity is known to be present or is suspected, one must consult the literature on the heterogeneous phase data of metal and non-metal systems toestimate the possible effect of that impurity on the freezing point [39,51,88].(Note: often in the analysis of the effect of impurities on freezing points,the impurity is assumed to be nonvolatile.)

Assuming that the ideal solution law holds and that the impurities remain inliquid solution, with no concentration gradients, then as the major componentslowly freezes, the depression in the freezing point, relative to the freezingpoint of the 100% pure material, is directly proportional to the overallimpurity concentration divided by the "first cryoscopic constant." This is expressed as:

T(pure) - T(obs) = x 2/A. (36)

In eq (36), T(obs) is the observed freezing point of the particular sample beinginvestigated, T(pure) is the freezing point of the 100% pure material, x 2 is the

mole fraction impurity concentration, and A is the first cryoscopic constant.A is given by the relation:

A = L/R[ T(pure)] 2, (37)

where L is the molar heat of fusion and R is the molar gas constant. (Note:eq (36) is an approximation. A more complete expression includes secondarycryoscopic constants. The term "first cryoscopic constant" is used here fordistinction. Also, in some cases, the term "cryoscopic constant" refers to thereciprocal of eq (37) and in other cases, to the effect of impurities per literor kilogram of solvent.) The first cryoscopic constants of metals are relativelysmaller than those of molecular substances and of the "cryogenic" gases ( 3He,4He, e-H 2, Ne, O 2, and Ar). Referring to eq (36), zinc, which has a firstcryoscopic constant of 0.0018/K, requires an overal l impurityconcentration of approximately 2 parts in 10 7 for the temperature of the half-frozen sample to be depressed by 0.0001 K, relative to the liquidus point. Onthe other hand, argon, with a first cryoscopic constant of 0.0203/K, requiresan impurity concentration close to 2 parts in 106 for the same temperaturedepression. Table 7 lists the heats of fusion and the first cryoscopic constants of substances specified for the defining fixed points. It is theusual practice at NIST to calibrate SPRT’s during the first 50% of the freeze.

3.2.2 TRIPLE POINTS OF e- H2, Ne, O 2. AND Ar

3.2.2.1 GENERAL CONSIDERATION OF APPARATUS DESIGN

The cryogenic fixed points (triple-points of pure gases equilibrium hydrogen,natural neon, oxygen, and argon) are best real ed in a calorimetric typeapparatus designed for calibrating capsule-type thermometer (SPRT’s, RIRT’s,germanium resistance thermometers (GRT’s), and others)[1, 2, 17, 18,20, 21,41,47, 58, 59, 78, 79, 80] . During calibration of the thermometers,

Substance Fixed Point Latent Heat First Cryoscopic ConstantTemperature of Fusion

T/K kJ/mole K -1

e-H 2 13.8033 0.117 0.0739Ne 24.5561 0.335 0.0668O2 54.3584 0.444 0.0181Ar 83.8058 1.188 0.0203Hg 234.3156 2.292 0.00502H2O 273.16 6.008 0.00968Ga 302.9146 5.585 0.00732In 429.7485 3.264 0.00213Sn 505.078 6.987 0.00329Zn 692.677 7.385 0.00185Al 933.473 10.79 0.00149Ag 1234.93 11.30 0.000891Au 1337.33 12.364 0.000831Cu 1357.77 13.14 0.000857

Table 7. Latent heats of fusion and first cryoscopic constants of definingfixed-point materials

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Figure 4. A schematic drawing of the NIST argon triple-point apparatus for calibrating sevenlong-stem SPRT’s and six capsule SPRT’s. Six long-stem SPRT wells surround a central SPRT well,which is large enough to accommodate a holder for calibrating a capsule SPRT. At the bottom of thesample cell, six capsule SPRT wells are circularly arranged between the long-stem SPRT wells.

LIQUID NITROGEN

67 cm

56 cm

SUPER INSULATEDDEWAR

VACUUM CAN

CAPSULE SPRTWELLS (6)

BAFFLES

SAMPLE CELL

SAMPLE CELL SHIELD

PASSIVE SHIELD

TEMPERATURECONTROLLED SHIELD

HE GAS MANIFOLDTO SPRT WELLS

LONG STEM SPRTWELLS (7)

PORT FOR FILLINGLIQUID NITROGEN

TO HIGH VACUUMAND ELECTRICALLEAD TERMINALS

TO SAMPLERESERVOIR

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Figure 5. A sealed cell suitable for containing cryogenic gases at high pressures. This cell of20 cm 3 volume was filled to 100 atmospheres with pure oxygen and used to realize the triple pointof oxygen. Another cell of the same outer dimensions, but of 16 cm 3 volume and with wells forthree capsule SPRT’s, was filled to 163 atmospheres with oxygen and also used to realize thetriple point of oxygen [47].

COPPERCAPILLARY

AUXILIARY ISOTHERMALSHELL, HELD WITH NUT

CELL HEATER

COPPER TEMPERINGSTRIPS

SAMPLE CELL

COPPER TUBES

HELICALLY GROOVEDCOPPER SLEEVE

PLATINUMRESISTANCETHERMOMETER

THERMOCOUPLECLIPS25.4

mm

94mm

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Z

the calorimeter system thermally isolates the vessel containing the pure gassample and the thermometers. The capsule thermometers should be installed inclose-fitting wells of the sample vessel, using stopcock grease to enhance thethermal contact. The wells should be vented for easy installation andsubsequent removal of the thermometers since such thermometers are sensitive toshock. The wells can be vented by designing the well tubes to extend completelythrough the sample cell or by machining a small groove along the length of thewell wall. The number of wells in.the vessel is limited only by the practicalsize of the vessel and of the calorimeter system. On the other hand, for largevessels, larger temperature gradients should be expected. The leads to thethermometers should be tempered on the sample vessel. (Note: the term "temper"refers to a process whereby sections of the leads or of the protective sheaths oflong-stem SPRT’s are placed in "steady-state thermal equilibrium" withselected parts of the apparatus.)

Since the triple point of argon is about 6 K above the normal boiling point ( NBP)of ni trogen and since l iquid ni trogen is readi ly avai lable in largequantities, long-stem type SPRT’s can be calibrated at the argon triple point inan apparatus cooled by liquid nitrogen. The apparatus should be designed tocool the upper part of the protective sheath of the long-stem SPRT’s to liquidnitrogen temperatures, and then to heat the intermediate section of the sheathabove the sensing element to the argon triple point so that the sensing coil willbe in thermal equilibrium with the argon at its triple point [42]. See figure 4for a schematic of such an apparatus presently in use at the NIST.

Sample vessels for the cryogenic fixed points could be ruggedly constructed forhigh pressures and sealed with a suitable amount of the pure gas [41,79]. These"sealed-sample vessels can be easily installed and removed from the calorimeter forreplacement of thermometers and also to be transported to other laboratories forcomparison (see fig.5).The amount of gas that can be sealed in suchvessels however,is rather limited and, hence,the calorimetric system must beoperated with sufficient adiabatic control that the small amount of heat offusion of the sample is adequate to realize the triple point and then calibratethe thermometers. Also, since the amount of sample gas is small, extra care must be taken to clean the vessel thoroughly before filling. The recommendedprocedure is to bake the vessel at high vacuum and then purge many times with thesample gas before finally filling and sealing the cell [41,47,79].

The vessel for a cryogenic fixed point can be installed in the calorimeter andconnected by a small diameter tube to a source of pure gas 1,2,31,32,44,58,59.In this design, enough condensed liquid could be used to nearly fill the vesseland thus, to provide an abundant supply of heat of fusion for calibration ofthermometers. The tube from the vessel must be connected to an "externalexpansion volume" of appropriate size so that when the system is at ambienttemperature the pressure is not excessive. The vessel could also be connected toan external rugged container into which all or nearly all of the sample can betransferred by cooling, and then contained bye high-pressure valve. Since underthese condit ions the "sample vessel" would not be subjected to highpressures, it can be constructed of thin copper parts. With appropriate gashandling and cleaning provisions, the same vessel could be used with all of thereference gases, stored in separate external rugged containers, and thethermometers calibrated at the fixed points of the gases without the necessity ofhaving to remove the thermometers from the vessel between fixed-point can have separate chambers for each of the gases. In the latter design,separate tubes for the gases must enter the calorimeter system. Although each ofthe chambers of a "multi-chamber sample vessel" would be relatively small, theamount of sample that could be condensed inside each chamber would still be morethan that which is normally used with the high pressure "sealed-sample vessel"Similar to the procedure used in filling sealed-sample vessels, a thoroughbaking, pumping, and purging procedure before filling should be followed withpermanently installed vessels.

3.2.2.2 REALIZATIONS OF THE TRIPLE POINTS AND THEIR APPLICATION TO CALIBRATION

The procedure for realizing a triple point of the cryogenic gases is to firstcompletely freeze the sample. If the triple point is being realized for the firsttime with the apparatus, the sample should be cooled sufficiently below thetriple point to determine the heat capacity of the system (sample, vessel, andthermometers) from about 5 K to 20 K below (depending on the gas) to about 20 Kabove the triple point, and to determine the heat of fusion of the sample duringthe same series of measurements [41,47]. (Note: check thermometers must becalibrated along with the test thermometers. The measurements on the checkthermometers will serve to guide the heating process during the calibration, aswell as to provide measurement statistics.)

After cooling to the required low temperature the vessel should be thermallyisolated by placing it under continuous adiabatic control. Then the followingseries of measurements should be performed:

1. the equilibrium temperature should be observed with the checkthermometer,

2. a measured amount of electrical energy should be added to thesystem.

3. a new equilibrium temperature should be established and measured4. steps 2 and 3 should be repeated until three heat capacity points

are obtained below the triple point.5. then,the sample should be completely melted by introducing a

measured amount of heat,6. next, the equilibrium temperature just above the triple point should

be measured7. then, three additional heat capacity points should be obtained above

the triple point in accordance with steps 2 and 3.

From the knowledge of the eight equilibrium temperatures (four below the triplepoint and four above the triple point) and the measured amounts of electricalenergies added, the heat capacities of the system below and above the triplepoint, and the heat of fusion, are calculated. If Q joules are added to thesystem from an initial equilibrium temperature Ti just below the triple point toheat the system to a final equilibrium temperature Tf Just above the triplepoint, the heat of fusion L is:

L=Q - C S( TO - T1) - C ,( Tf - TO), (38)

where C s and C t are the mean heat capacities in the temperature intervals in thesolid and liquid phases, respectively, and To is the triple-point temperature.

For calibration of SPRT’s, the sample should be completely frozen for the secondtime and the temperature set at about 1 K below the triple point, the samplethermally isolated, and the equilibrium temperature measured. From the knowledge of the previously determined heat capacity of the system below thetriple point and of the heat of fusion, add enough electrical energy to meltabout 10% of the sample. If T 1 is the initial equilibrium temperature just belowthe triple point, the required amount of electrical energy Q, to melt 10% of the sample is:

Q1= 0.1L. + C 8( T0 - T1). (39)

Once the system comes to equilibrium, measure the resistances of all of thethermometers. Repeat the measurements at 20%, 40%, 60%, 70%, and 80% melted. Ifthe sample is about 99.9999% pure, all measurements on each thermometerthroughout this melted range should agree to within 0.1 mK to 0.2 mK.

In using a temperature fixed point, one must make corrections for the hydrostatic head of the liquid and for the gas pressure on the defined equilibrium state. Table 6 gives the dT/dp for the defining fixed points of theITS-90, both in terms of the external gas pressure to which the fixed-pointmaterial is exposed and in terms of the column of liquid.

3.2.2.2.1 TRIPLE POINT OF EQUILIBRIUM HYDROGEN, 13,8033 K (-259.3467 °C)

Hydrogen gas samples of 99.9999% and higher purity are readily available. [Thef i rst cryoscopic constant of hydrogen is re lat ively high (0.040/K).Consequently, the liquidus point of an ideal hydrogen solution of 99.9999% puritywould be approximately 0.01 mK lower than that of 100% pure hydrogen. Except forhelium and deuterium, all other impurities would be either frozen or in solutionin very small amounts.] The commonly used catalyst for converting ortho hydrogento para hydrogen is hydrated ferr ic oxide (Fe 2O3+H2O or FeO+OH)Other oxides of magnetic elements, either pure or mixed-metal, such as those ofchromium, nickel, cobalt, and neodymium, also have been used as catalysts forortho to para hydrogen conversion. The hydrated ferric oxide catalyst is prepared by mixing at about 30°C relatively dilute solutions (about 2 molal) of ferric chloride and sodium hydroxide, with only a slight excess of sodiumhydroxide, washing the resulting gelatinous Fe(OH) 3 precipitate thoroughly with

distilled water, air drying at 140°C for 24 hours, vacuum baking at 110°C for 16to 20 hours, and back-filling with hydrogen while the catalyst is still hot[7,104). The catalyst is activated by flowing hydrogen through it for about 4hours while the catalyst is maintained at a temperature of about 150°C. The sample vessel and ancillary components should be designed to permit the whole of the hydrogen sample to come into contact with the catalyst at the equilibriumtemperature. See references [2,31,58].

3.2.2.2.2 TRIPLE POINT OF NATURAL NEON. 24,5561 K (-248,5939,˚C)

Neon gas samples of 99.999% purity are commercially available. Samples of higherpuri ty may be obtained by special arrangement with the suppl ier. The

Figure 6. Two types of triple point of water cells with wells for platinumresistance thermometers. The cel ls contain pure air-free water. Thethermometer wells are made of precision-bore tubing.

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principal impurities are CO, H 2, He, and N 2. The CO and the N 2 impurities can befrozen out by slowly flowing the sample through a coiled tube immersed in liquidneon; the H 2 and the He impurities can be removed by freezing the neon sample inliquid hydrogen and pumping, with care so that the lighter iso topes of neon are notpreferentially removed. [The first cryoscopic constant of neon is 0.0668/K.Consequently, the liquidus point of an ideal neon solution of 99.999% purity wouldbe approximately 0.1 mK lower than that of 100% pure neon.] The purified sampleshould be collected in a clean stainless-steel cylinder by cooling the cylinderin liquid hydrogen (or cooled with liquid helium). If desired, the purifiedsample can be collected directly in the cooled sample vessel. See references[1,79].

3.2.2.2.3 TRIPLE POINT OF OXYGEN. 54 .3584 K (-218,7916 ˚ C)

Oxygen gas samples of 99.999% purity are commercially available. Accuratechemical analysis of oxygen is difficult and, therefore, the claimed purity may notbe correct. Unknown or undetected impurities are chemically less reactive thanoxygen, e.g, the noble gases, and, in particular, argon, which forms a peritecticwith oxygen. Samples of purity greater than 99.999% may be obtained by specialarrangement with the supplier. [The first cryoscopic constant of oxygen is0.0181/K. Consequently, the liquidus point of an ideal oxygen solution of99.999% purity would be approximately 0.6 mK lower than that of 100% pure oxygen.]Careful preparation by thermal decomposition of potassium permanganate canyield samples of 99.99992% purity or better [47]. The oxygen sample should bestored in clean stainless-steel cylinders. See references [32,47,59,79,80].

3.2.2.2.4 TRIPLE POINT OF ARGON. 83,8058 K (-189.3442 ˚ C)

Argon gas samples of 99.9999% purity or better are readily available. The usualimpurities are the components of air, moisture, and hydrocarbons. [The firstcryoscopic constant of argon is 0.0203/K. Consequently, the liquidus point of anideal argon solution of 99.9999% purity would be approximately 0.05 mK lower thanthat of 100% pure argon.] To fill the sample vessel, the gas may be used directly orit may be dried first by slowly passing it through a coiled tube immersed ineither liquid oxygen or a Dry Ice/ethyl alcohol mixture. See references[17,41,42,59,79,80].

3.2.3 TRIPLE POINT OF WATER. 273.16.K (0.01 ˚ C)

The triple-point temperature of water is assigned the value 273.16 K on theKelvin Thermodynamic Temperature Scale and also on the ITS-90. It is thereference temperature for resistance ratios in platinum resistance thermometry.The water used in preparing triple point of water cells is pure water ofnaturally-occurring isotopic composition. Figure 6 shows two commonly usedtypes of triple point of water cells.

Triple point of water cells are usually prepared from river water that has beenpurified by chemical treatment and distillation. River water is expected to haveconcentrations of deuterium and the heavier isotopes of oxygen that are lowerthan that of ocean water. The extreme difference in the triple points ofnatu rally occurring water, including polar water, is given as 0.25 mK [100].

It is expected that differences among water triple-point cells of river waterwould be much smaller than 0.25 mK. (The isotopic composition differencebetween river water and ocean water [100] has been estimated to cause no morethan a 0.050 mK difference in the triple-point temperature.) While the basicmaterial is plentifully available, preparation of water triple-point cellsrequires a special effort [5,40]. Although the effect on the triple-pointtemperature is negligible, a trace of air always remains in most sealed triplepoint of water cells. When a cell at room temperature is gently inverted from oneend to the other and a sharp "click" is produced through the water hammer action,the amount of gas in the cell wi11 have negligible influence on the triple-pointtemperature.

3.2.3.1 REALIZATION AND APPLICATION OF THE TRIPLE POINT OF WATER

In preparation for producing an ice mantle that is required for realizing thetriple-point temperature of water, the thermometer well of the cell is wipedthoroughly dry, sealed with a rubber stopper, and the cell placed in an ice bath tocool to a few degrees above the ice point. When the cell has been cooled in thismanner, an ice mantle of fairly uniform thickness can be obtained. Withdrawthe cell from the ice bath, set it upright on a stand, and place one drop ofethyl alcohol at the bottom of the well. Introduce small amounts of crushed DryIce into the bottom of the well and continue to do so until a thick mantle is formedat the bottom. Then, fill the well with crushed Dry Ice to the water level of thecell. Continue to add crushed Dry Ice to the well so as to maintain the level ofDry Ice at the water level. If the Dry Ice level becomes low before more is added,the ice mantle may crack. If the cell were pre cooled as indicated above, a solidice bridge may form at the water level. If such a bridge forms, melt it immediatelywith heat from the hands while gently sha king the cell. The solid ice bridge cancompletely seal the cell at the top and any subsequent formation of ice couldproduce enough pressure to rupture the glass ce l l . When a mant le o fapproximately the desired thickness (4 to 8 mm) is formed, stop adding Dry Ice,replace the cell in the ice bath with the well opening slightly above the watersurface of the ice bath, and leave the cell there until all of the Dry Iceevaporates. Then, fill the well with ice water and store the cell in an ice bathor ice pack for a day before using it. When the ice mantle is frozen by using DryIce, a process that usually requires less than one hour, the strains in the icecause the "triple-point temperature" to be about 0.2 mK low. These are removed byletting the mantle anneal for one day.

Other methods can be used also to prepare the ice mantle. With ethyl alcohol inthe thermometer well, any "cold finger" technique can be used. This tec hniqueincludes successively insert ing l iquid nitrogen cooled rods, using aclosed-end tube containing crushed Dry Ice, or using a heat-pipe cooler. Thesemethods require more time to freeze the mantle,,but the strain produced in the icewill be less than those produced by the Dry Ice technique.

After the strains in the ice mantle have been relieved by storing the cell in anice bath for at least one day, insert momentarily a glass rod into the well inorder to melt a thin layer of ice next to the well. This forms an ice-w aterinterface immediately adjacent to the thermometer well. The test for this "innermelt" is made by giving the cell a rotatory impulse to determine whether

Figure 7. An SPRT in a Type A triple point of water cell immersed in an ice bath.

A - platinum resistance thermometer, B - heavy black felt to shield againstambient radiation, C - polyethylene tube for guiding the SPRT into thethermometer well (the tube has a small hole near the top of the thermometer well toallow water, but not ice, to enter the tube.), D - water vapor, E -borosilicate glass cell, F - water from the ice bath, G - thermometer well(precision bore glass), H – ice mantle I - air-free water, J - aluminumbushing with internal taper,at the upper end to guide the SPRT into its closefitting inner bore, K – polyurethane sponge for cushioning the SPRT, L –finely divided ice and water.

the ice mantle rotates freely about the axis of the thermometer well. The outer icewater in ter face guards and thermal ly s tabi l izes the inner ice-waterinterface temperature that is measured with the SPRT.

Figure 7 shows a triple point of water cell immersed in an ice bath with an SPRTinserted into the thermometer well. An SPRT should be precooled in a glass tube ofwater in an ice bath before it is inserted into the triple-point well so that thethickness of the water layer next to the thermometer well will not becomeexcessive. Also, the time required for the SPRT to come into thermalequilibrium will be shortened. Heavy felt cloth should be used to cover the ice bathin order to prevent ambient radiation from entering the bath and reaching thethermometer element, which otherwise would cause the thermometer to give aslightly high (erroneous) reading. A plastic foam cushion should be placed at thebottom of the thermometer well to protect the well and the SPRT. Since water is apoor thermal conductor, a close fitting aluminum sleeve should be used to enhancethe thermal conduction.

The thermometer current should be imposed immediately after insertion of the SPRTinto the cell so that readings can be made under conditions of steady-state selfheating. Five to ten minutes or longer may be required before steady-stateconditions are reached. To avoid errors due to variations in the self heatingthat arise from variations in the thermal contact of the ther mometer withits surroundings, it is best to read the SPRT at two cu rrents and extrapolate thereadings to zero power in the SPRT.

3.2.4 FREEZING. MELTING. OR TRIPLE POINTS OF METALS: Hg Ga. In. Sn. Zn. Al. AgAu. or Cu

The realization of metal fixed points requires the continuous presence ofliquid-solid or liquid-solid-vapor phases in thermal equilibrium. With SPRT’s, theliquid-solid interface, i.e., the equilibrium whose temperature is meas ured, mustsurround and must be as close to the temperature sensing element as possible.Since the first cryoscopic constants of metals are relatively low, the fixed-pointmetal samples should be at least 99.9999% pure. Figure 8 shows idealizedliquid/solid equilibrium conditions inside fixed point cells used in freezing andmelting experiments. Figure 9 shows a representative arrang ement of an SPRT insertedinside a metal fixed point cell. Ideally, and similar to the water triple-pointcell, an outer liquid-solid interface, which completely surrounds the innerinterface, exists close to the container wall. This outer interface, which has atemperature very close to that of the inner interface, thermally protects andthermally stabilizes the inner interface. In freezing experiments, a layer ofsolid is first formed at the crucible wall, then a thin layer of solid is inducedon the thermometer well by inserting cooling rods. As freezing advances, the outerinterface approaches the inner interface until all of the material is solid. Inmelting experiments, a layer of liquid is first formed next to the crucible, thena thin layer of liquid is formed next to the thermometer well by inserting awarming rod or a long heater. As mel ting advances, the outer liquid/solidinterface approaches the inner interface.

Since different furnace or bath designs are required for fixed-point cellsoperated at different temperatures, they will1 be discussed along with each ofthe f ixed points , or references wi l l be made to appropr ia te sources of

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In radiation thermometry, the liquid-solid phase of the metal fixed point mustcompletely surround the blackbody radiator capacity

3.2.4.1 CONTAINER MATERIAL

Containers for the fixed-point metals must not contaminate the metal sample, and thecontainer material must be rugged enough to retain its integrity under thermalcycling between the temperature of use and ambient temperature. The containermaterial preferably should be inert to air at temperatures of use;if not, e.g.,graphite above about 200 °C, the container plus the fixed-point material must beprotectively enclosed in an inert gas such as nitrogen, argon, or helium, usingeither a borosilicate or fused silica glass envelope. It should be assumed thatthe fixed-point material itself will react chemically with air and, thus, thematerial must be protected.*

3.2.4.2 METAL FIXED POINT DEVICES FOR CALIBRATING SPRT’s

Figure 9 shows a representative fixed-point cell that can be used forcali brating long-stem type SPRT’s. In the following sections, individual typeswill be described.

3.2.4.2.1 MERCURY TRIPLE POINT

3.2.4.2.1.1 MERCURY SAMPLE

On the ITS-90, the triple point of mercury (equilibrium phase state of mercurysolid, liquid, and vapor phases) is assigned the value 234.3156 K (-38.8344°C).Depending upon the choice of container material and operating procedure, it may bemore practical to real ize the mercury freezing point at one standardatmosphere, the value being 234.3210 K (-38.8290 °C). Mercury samples withimpurity content of 1 part in 10 8 or less can be prepared by potassium hydroxide andnitric acid washings, followed by triple distillation [48]. The alkali and acidwashings can be carried out by vigorously bubbling clean filtered air, throughthe mixture of mercury and the alkali or the acid. To remove any remainingoxidizable impurities, the first two distillations should be carried out underreduced pressures with a fine stream of clean filtered air bubbling into themercury in the distillation container. The third distillation should be doneunder high vacuum to remove the noble metals. With the high-purity mercury(99.999999%), both freezing and melting techniques give triple-point temperaturesthat agree to within ± 0.1 mK over most of the liquid-solid range. [The firstcryoscopic constant of mercury is 0.00503/K. Consequently, the liquidus pointof an ideal mercury solution of 99.999999% purity would be approximately 0.002mK lower than that of 100% pure mercury.]

3.2.4.2.1.2 CONTAINERS FOR MERCURY

Any container material can be used with mercury that is sufficiently rigid anddoes not dissolve in, or chemically react with, mercury in the temperature range ofstorage and application. The choice will depend upon whether the mercury fixed-point cell is to be used at its triple point, at its freezing point, or

Figure 9. An SPRT in a metal freezing-point cell.A - platinum resistance thermometer, B - to helium gas supply and pressuregauge, C - thermometer gas seal with silicone rubber, D - silicone rubberstopper, E - thermal insulation (washed Fiberfrax),F - thermometer guide tube[precision bore tube, ground (matt finish) to uniform outside diameter], G -heat shunt (graphite) in close contact with F and with H, H - borosilicateglass cell [precision bore tube ground (matt finish ) to uniform outsidediameter], I - graphite cap (lid) for the graphite crucible, J - graphitethermometer well, K - metal sample, L - graphite crucible, M - thermalinsu la t ion (F iber f rax paper) between the graph i te cruc ib le and theborosilicate glass cell.

Figure 10. Two mercury triple-point cells, one constructed of borosilicateglass and one of Type 304 stainless steel. The two small-diameter tubes at thetop facilitate the cleaning of the cells before filling and sealing. The glasscell is sealed by melting the small-diameter tubes, but the stainless steel cellis sealed by pinching flat the small-diameter tubes and electric-arc weldingthem, thereby serving them at the middle of the flat.

Figure 8. Idealized liquid/solid equilibrium conditions inside fixed pointcells used in freezing and melting experiments. In freezing experiments, alayer of solid is first formed at the crucible wall, then a thin layer of solidis induced on the thermometer well by inserting cooling rods. In meltingexperiments, a layer of liquid is first formed next to the crucible, then athin layer of liquid is formed next to the thermometer well by inserting awarming rod or a long heater, As melting advances, the outer liquid/solidinterface approaches the inner interface.

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3.2.4.2.1.3 METAL CONTAINERS

Mercury is capable of dissolving most metals, at least at the low levels ofimpurity content (<l ppm) that are the permitted maxima for metal fixed points Iron,nickel, chromium, and tantalum have been reported to be soluble at only 1 ppm orless; hence, stainless steel is an adequate container for mercury in mosttemperature standard applications [53,103). (Note: the solubility of nicke1 inmercury may be close to the limit of 1 ppm.) Mercury triple-point cells can beprepared by pinching and welding the small diameter tubes used for cleaning,evacuating, and filling (see fig. 10).

3.2.4.2.1.4 CONTAINERS OF GLASS

It is expected that some metal impurities in glasses [single metal oxide(e.g., fused silica glass) or mixed metal oxide (e.g., borosilicate glass)] or"ceramics" can be leached out by mercury when the mercury is stored in them for manyyears. Traditionally, "soft glass" has been considered suitable for storingmercury [48]; however, soft glass, without special treatment, may be sus ceptibleto breakage when thermally shocked. Borosilicate glass and fused silica glassare more practical choices for mercury containers. Figure 11 shows a borosilicateglass mercury triple-point cell inside a stainless steel holder.

3.2.4.2.1.5 CONTAINERS OF PLASTIC

Organic plastics, such as polyethylene polytetrafluoroethylene (Teflon), orpolytrifluorochloroethylene (Kel-F), all of which are free of metals, can be usedto contain mercury and be used at the mercury freezing point. A stainless steelholder similar to that used for the glass mercury cell and for the stainlesssteel mercury cell (see fig.11) or similar to the holder used for the indium cell(see fig. 12) could be used as the external holder for a plastic mercury cell.Although plastic cells have not been used yet in preparing mercury fixed pointcells, it would be practical and desirable to use pla stic cells for realizing themercury fixed point. Since the vapor pressure of mercury at room temperature issufficiently high that mercury vapors can be transported under vacuumconditions, the vapors should be confined by an atmosphere of helium or otherinert gases.

3.2.4.2.1.6 ASSEMBLY OF MERCURY CELLS

A purified mercury sample can be vacuum distilled into glass containers, with theglass filling tube then sealed under vacuum with a flame [43]. The merc ury samplemay be vacuum distilled into stainless steel containers and the fil ling tubepinched, and then cut and sealed using electric-arc welding techniques [43].

3.2.4.2.1.7 REALIZATION AND APPLICATION

When the total impurity content of a mercury sample is about one part in 10 8, bothfreezing and melting techniques yield triple-point temperatures agreeing towithin ± 0.1 mK over most of the liquid-solid range. A dual-stage refrigeratorcan yield a temperature near -40°C and, hence, could be used for freezing mercury,but a much simpler stainless steel vacuum enclosure placed in a Dry Ice/ethylalcohol mixture (-78 °C) can reduce the freezing rate of mer cury to give a freezeduration of about 10 hours or more with 2.2 kg of mercury, and that is perfectlyadequate. Figure 11 shows such a stainless steel enclosure that has been usedwith a borosilicate-glass mercury cell at the NIST.

To start a freeze, fill the stainless steel enclosure that contains the me rcurytriple-point cell with dry air and immerse it in a Dry Ice/ethyl alcohol bath.Fill the themometer well with ethyl alcohol and insert therein an SPRT formonitoring the temperature of the cell. Usually, mercury supercools about 6 °C ina borosilicate glass cell but only about 3 °C in a stainless steel cell. Whenrecilescence is observed, evacuate the stainless steel holder. Remove themonitoring SPRT from the well and replace it with a thin-wall stainless steeltube that contains ethyl alcohol and that has been cooled in a tube of ethylalcohol immersed in a Dry Ice/ethyl alcohol bath. Insert successively into thestainless steel tube two or three liquid-nitrogen cooled glass rods, for about5 minutes each, in order to freeze a thin layer of mercury around the the rmometerwell. The purpose of the stainless steel tube is to collect the frost that forms onthe rods when they are removed from the liquid nitrogen. Remove the stain less steeltube and replace it with the monitoring SPRT, which has been cooling in the tubeof cold ethyl alcohol. Switch on the thermometer measuring current. (Note: it maybe necessary to refill the thermometer well with a small amount of cold ethylalcohol from the Dry-ice cooled tube before the monitoring SPRT is inserted intothe well. The well should be completely filled with ethyl alcohol when the SPRT isin the well.) With the induced inner freeze around the thermometer well,temperature equilibrium is reached in about 5 minutes. After the resistance ofthe monitoring SPRT is read, other cooled SPRT’s are successively insertedinto the mercury cell and calibrated. The final reading in a cell is made with themonitoring SPRT in order to check the extent of the freeze. This final reading ofthe monitoring SPRT must agree with the initial reading to within ± 0.1 mK.See reference 43 for more details on the calibration procedure at themercury triple point.

3.2.4.2.2 MELTING POINT OF GALLIU M

The melting point of gallium is assigned a temperature of 302.9146 K (29.7646°C) onthe ITS-90. Gallium of 99.99999% purity can be obtained commercially. At such highpurity, both freezing and melting techniques should yield liquid-solidequi librium temperatures that agree to within ± 0.1 mK. Since the metal expandsabout 3% on freezing, plastic containers, such as polyethylene, polypropylene,or polytetrafluoroethylene, are the most suitable. These are sufficientlyflexible at around 30 °C to accommodate the volume change in the gallium. Inassembling the gallium fixed-point cell, the supercooled metal can be poureddirectly into the container. A second more rugged container of Nylon, glass, orstainless steel should enclose the flexible container so that the pressure of theinert gas over the metal can be controlled at one atmosphere or be evacuated toobserve the triple point. A gallium fixed-point cell, consisting of an all plasticcontainer, that is used at the NIST is shown in f igure 13. Since gallium supercools as much as 25 °C to 70 °C, depending upon the plastic material that is in contact with it, the most convenient method of observingits liquid-solid equilibrium temperature is the melting technique. [The first

Figure 11. A borosilicate glass, mercury triple point cell in a stainless steelcontainer. A stainless-steel, mercury triple-point cell may also be mounted insidethe stainless steel container. With the high-purity mercury sample, both freezingand melting techniques yield triple-point values agreeing to within ±0.1 mK overmost of the liquid-solid range.


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Figure 13. An all-plastic gallium melting/triple-point cell. The triple-point isrealized by using the melting technique. The cell is periodically evacuated throughthe valve.

A - valve (Zytel), B - bath lid (Plexiglass), C - support rod (Nylon), D - pumpingtube (polyethylene), E - cap (Nylon), F - sample container (Teflon), G - case(Nylon), H - thermometer well (Nylon), I - gallium metal, J - base of the case

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Figure 12. Photograph of an all-plastic indium cell and its stainless steel container

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cryoscopic constant of gallium is 0.00732/K. Consequently, the liquidus pointof an ideal gallium solution of 99.99999% purity would be approximately 0.01 mKlower than that of 100% pure gallium.]


In order to solidify the gallium metal in a fixed-point cell, initially in thesupercooled state (e.g., at room temperature), first insert successively two orthree liquid-nitrogen-cooled copper rods into the thermometer well of the cellto induce nucleation, and then place the cell in an ice bath for about one houror longer. The cell with the solidified gallium may then be placed in an oilbath at a temperature of about 40 *C to partially melt the sample to form anouter liquid-solid interface. To form a liquid-solid interface next to thethermometer well (an inner melt), the bath oil may be circ ulated thro ugh thethermometer well by pumping the oil through a tube placed in the well. Afterabout 20 minutes in the hot oil bath, about 25% of the gallium will be melted.The inner liquid-solid interface can also be prepared by using an electric heaterin the well. The amount of electric energy required, e.g., to form about a 7 mmshell of liquid around the thermometer well, can be calculated from the outerdimensions of the thermometer well and the heat of fusion of gallium (see table7). The gallium cell is then securely mounted, completely immersed so that thethermometer well will be filled with the bath oil, in a stirred oil bath,controlled at a temperature about 10 mK above the liquid-solid equilibriumtemperature (melting point or the triple point). Also, the cell can immersed ina fairly close-fitting, oil-filled aluminum or copper block, controlled at atemperature about 10 mK above the equilibrium temperature. The monitoring PRTis heated and then inserted into the thermometer well of the gallium cell.Readings are taken after about 20 minutes of equilibration in the cell. Themonitoring SPRT is replaced in the cell with a preheated test SPRT andmeasurements on it are made after about 20 minutes. A number of SPRT’s can besuccessively calibrated in the same "melt". When all of the test SPRT’s havebeen calibrated, a final measurement in the cell is made on the monitoring SPRT.This reading of the monitoring SPRT should agree with the initial reading towithin ± 0.1 mK. Also, measurements with different melts should agree to within0.1 mK. See references [16,26,65,68,94].

3.2.4.2.3 FREEZING POINT OF INDIUM

The freezing point of indium is assigned the value 429.7485 K (156.5985 ˚C) onthe ITS-90. Metal samples of 99.9999% purity and higher are commerciallyavailable. The freezing point of indium is at a sufficiently low temperatureto permi t the use of conta iners of h igh temperature p last ics[Polytetrafluoroethylene (Teflon), polyimide/amide, and others), borosilicateglass, and stainless steel (4,69,14,92). See figure 14 for an example of aTeflon container used for indium at the NIST. As used with metals that freezeat higher temperatures, graphite can also be used with indium. The metal isavailable in the form of small pellets, wire, and rods. Suitable amounts fora sample can be easily weighed into the container. (The first cryoscopicconstant of indium is 0.00212/K. Consequently, the liquidus point of an idealindium solution of 99.9999% purity would be approximately 0.5 mK lower than thatof 100% pure indium.]

Figure 14. An all-plastic indium freezing-point cell to be used in a stainlesssteel container, such as that shown in figure 12. The argon gas pressure insidethe stainless steel container is adjusted to one atmosphere at the freezing point.A similar all-plastic cell and stainless steel container may be used to realizethe mercury freezing point or meIting point at one atmosphere.


A tube furnace containing the indium-point cell is controlled about 5 ˚ C abovethe freezing point of indium until the metal is completely melted. (It isconvenient to control the furnace temperature automatically and melt the metalsample overnight so that the freezing of the metal may be s started in themorning.) Insert the check SPRT into the cel1 well and when the SPRT indicatesthat the sample is about 5 above the freezing temperature, change the furnacetemperature control settings to control at 5 ˚ C below the freezing point. Whenthe check SPRT indicate. recalescence, change the furnace temperature controlsettings to control at 1 ˚ C to 0.5 ˚ C below the freezing point. Withdraw thecheck SPRT from the cell well and insert successively in the well two fusedsilica glass rods, each initially at room temperature, for about 5 minutes each and then insert the cool check SPRT in order to freeze a thin mantle around thethermometer well. (To avoid the consequence of inserting borosilicate glassrods into the aluminum or silver point cell to form the mantle around thethermometer well, all glass rods used for this purpose in the laboratory shouldbe fused silica glass.) Within 20 to 30 minutes, the readings on the check SPRTshould indicate that the cell is at temperature equilibrium. After the readingson the check SPRT are completed, test SPRT’s, that have been heated in anauxiliary furnace, are successively inserted into the cell well and calibrated.After all of the test SPRT’s have been calibrated the preheated check SPRT isinserted again into the cell well and read. This second reading should agreewith the first to within ± 0.1 mK. See references (4,69,74,92].

3.2.4.2.4 FREEZING POINT OF TIN

The freezing point of tin is assigned the value 505.078 K (231.928 ˚C) Metalsamples of 99.9999% purity are commercially available. Graphite containers arecommonly and successfully used for tin. Although the use of materials such asboron nitride (BN) has not been reported, it could be a suitable container fortin. High purity tin has been found to supercool 25 ˚ C or more [73,76]; hence,the freeze is nucleated by rapid cooling outside the furnace. The metal isavailable in the form of small pellets and in rods suitable for filling thegraphite container. A method for filling graphite containers and installing thegraphite thermometer wells is described in reference [46]. [The first cryoscopicconstant of tin is 0.00329/K. Consequently, the liquidus point of an ideal tinsolution of 99.9999% purity would be approximately 0.3 mK lower than that of 100%pure tin.]


A tube furnace [46] containing the tin freezing-point cell is controlled about5 ˚C above the freezing-point temperature until the metal is completely melted.(It is convenient to control the furnace temperature automatically and melt themetal overnight so that freezing of the metal can be started early in themorning.) Insert the check SPRT into the cell well and, when the SPRT indicatesthat the sample temperature is about 5 ˚C above the freezing point, change thefurnace temperature control settings to control at 1 ˚C to 0.5 ˚C below thefreezing point. When the check SPRT indicates that the cell temperature isclose to the freezing-point value, withdraw the cell and the SPRT from thefurnace. The cell will then cool rapidly and when the SPRT detects recalescence,replace the cell in the furnace. Withdraw the check SPRT from the cell well.Insert successively in the well two fused silica glass rods, each initially atroom temperature, for about, 5 minutes each, and then the cool check SPRT inorder to freeze a thin mantle around the thermometer well. Within about 20 to 30minutes the readings on the check SPRT, should indicate that the cell is attemperature equilibrium. After the readings on the check SPRT are completed,test SPRT’s, that have been heated in an auxiliary furnace, are successivelyinserted into the cell well and calibrated. After all of the test SPRT’s havebeen calibrated, the check SPRT is heated and inserted again into the cell welland read. This reading should agree with the initial reading to within ±0.1 mK.See references [43,46,73,76].

3.2.4.2.5 FREEZING POINT OF ZINC

The freezing point of zinc is assigned the value 692.677 K (419.527 ˚C) Metalsamples of 99.9999% purity are commercially available. High purity liquid zinchas been found to supercool about 0.02 ˚C to 0.06 ˚C; hence, unlike the freezingprocedure used with the tin-point cell, its freeze can be initiated in thefurnace without withdrawing the cell from the furnace. Graphite containers arecommonly and successfully used for zinc. Although the use of materials such asboron nitride (BN) has not been reported, it could be a suitable container forzinc. The metal is available in the form of small pellets and in rods suitablefor filling graphite containers. [The first cryoscopic constant of zinc is0.00185/K. Consequently, the liquidus point of an ideal zinc solution of 99.9999%purity would be approximately 0.5 mK lower than that of 100% pure zinc.]


A tube furnace containing the zinc-point cell is controlled about 5 ˚C above thefreezing point until the metal is completely melted. If the furnace temperatureis maintained at a higher temperature, the zinc will melt faster, but the zincshould never be heated by more than about 5 ˚C above its melting point. (It isconvenient to control the furnace temperature automatically and melt the zincsample overnight so that the freezing of the metal can be started early in themorning and the calibration of six or more test SPRT’s can be completed duringthe same day.) Insert the zinc-point check SPRT into the cell well. When theSPRT indicates that the melt is about 5 ˚C above the freezing point, change thefurnace temperature control settings to control at 5 ˚C below the freezing pointin order to initiate rapid cooling for nucleation. When the check SPRT indicatesrecalescence, change the furnace temperature control settings to control at 1 ˚Cto 0.5 ˚C below the freezing point. Withdraw the check SPRT from the cell welland insert successively into the well two fused silica glass rods, each initiallyat room temperature, for about 5 minutes each, and then insert again the coolcheck SPRT. This freezes a thin mantle around the thermometer well. Withinabout 20 to 30 minutes, the readings on the check SPRT should indicate that thecell is at temperature equilibrium. After the readings on the check SPRT arecompleted, test SPRT’s, that have been heated in an auxiliary furnace, aresuccessively inserted into the cell well and calibrated. After all of the testSPRT’s are calibrated, the preheated check SPRT is inserted again into the cellwell and measurements made on it. This second reading should agree with thefirst to within ± 0.1 mK. references [41,73,75].

5 mm DIA. HOLETHROUGH CAP

34.34 mm ID44.34 mm OD

18.70 mm OD

CAP (TEFLON)9 mm

1 mm

2 mm

240 mm

25mm

115mm

15mm

5 mm

CONTAINER (TEFLON®)

THERMOMETER WELL (TEFLON®)

5 mm

36.34 mm ID 40.34 mm OD

12.70 mm (0.500in.) ID14.70 mm OD

111mm

1 mm 25mm

10 mm

5 mm3 mm

10 mm ID 14 mm OD

3 mm

30 mm OD FUSEDSILICA TUBE

0.005" SPIRAL GROOVE ALONGINSIDE OF THERMOMETER WELL(1 OR 2 THREADS/in.)

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A - connection to high vacuum, purified argon source, and pressure gauge, B –fused-silica-to-Kovar graded seal, C - fused-silica connecting tube, outersurface matte finished to minimize radiation piping, D - thermometer guidetube, E - heat shunts (Inconel disks), F - thermal insulation (Fiberfrax), G -fused-silica outer envelope, H - graphite lid, I - graphite thermometerwell, J - fused-silica thermometer well, K - fused-silica fiber-woven tape forcushioning the graphite freezing-point cell inside the fused-silica enclosure,L - metal sample, M - graphite crucible, N - fused-silica fiber pad forcushioning the thermometer, 0 - Fiberfrax paper liner.

3.2.4.2.6 FREEZING POINT OF ALUMINUM

The freezing point of aluminum is assigned the value 933.473 K (660.323 ˚C).Metal samples of 99.9999% purity are commercially available. High puritygraphite containers have been used successfully with aluminum. High purityliquid aluminum has been found to supercool about 1 ˚C to 2 ˚C; hence, its freezecan be initiated in the furnace without withdrawing the cell from the furnace.Aluminum is highly reactive, particularly at elevated temperatures; liquidaluminum is capable of dissolving many metals. Liquid aluminum reacts withmoisture, forming the oxide and dissolving the hydrogen. The compounds Al 4C3 and

aluminum oxycarbide have been found in aluminum samples cast in graphite at1000 ˚C. Because of the high chemical reactivity of aluminum, the graphite cellcontaining the metal must be completely protected by enclosing the cell in afused silica envelope (see fig. 15). The argon or helium gas that is used topressurize the freezing metal at one atmosphere must be thoroughly devoid ofmoisture, hydrogen, oxygen, hydrocarbons, and other substances that would reactwith liquid aluminum. The cell must not be heated more than 5 ˚C above thealuminum freezing point. [The first cryoscopic constant of aluminum is0.00149/K. Consequently, the liquidus point of an ideal aluminum solution of99.9999% purity would be approximately 0.7 K lower than that of 100% purealuminum.]

3.2.4.2.6.1 ASSEMBLY OF AN ALUMINUM-POINT CELL

High purity aluminum can be obtained in the form of shots or rods. Determine.the internal volume of the graphite container, taking into account thethermometer well. Determine the mass of liquid aluminum required to fill thecell to within 0.5 cm of the graphite lid. Weight out aluminum shots or cut andclean aluminum rods that correspond to this mass. The rods should be cut witha carbide tipped tool and cleaned by etching in a hot (about 200 ˚C) solutionconsisting (by volume) of reagent grade phosphoric acid (15 parts, sulfuricacid (5 parts), and nitric acid (7 part), and then carefully rinsing many timesin distilled water. Load the graphite crucible with the aluminum sample andthen slide it into an extra-long fused-silica test tube such as that shown infigure 16. Insert the test tube into the tube furnace and evacuate it. Whilecontinuing to evacuate the tube, set the furnace temperature to control at about5 ˚C above the melting point of aluminum. When the sample has completely melted,cool it to room temperature, while continuing to pump the tube. If aluminumshot, or rods of odd sizes, are used, the graphite cell will require severalloadings and meltings before the desired amount of total sample has been loadedinto the cell. When the graphite crucible is appropriately loaded with thesample, replace the silicone rubber stopper at the mouth of the extra-long testtube of figure 16 with the device for inserting the graphite thermometer welland lid (see reference [45] or fig. 17). Insert the test tube into the tubefurnace, evacuate it, and then fill it with high purity argon to a pressureslightly above ambient. Melt the aluminum sample and push the graphite well andlid into the cell. Cool the sample to room temperature, while maintaining theargon pressure in the test tube slightly above the ambient pressure. Finally,assemble the graphite cel1 containing the aluminum sample into the desiredfreezing - point cell configuration (see references [43,45,701] or fig. 15).

Figure 16. A method for filling a graphite freezing-point cell by melting themetal sample in the graphite crucible. The required amount of sample is placedin the graphite crucible and the crucible is inserted into the fused silicatube. To protect the sample, the fused silica tube is evacuated or filled withan inert gas (e.g., purified argon) before melting the metal in a tube furnace.Depending upon the geometry of the sample, the melting of two or more batches of sample may be required.

A - Silicone rubber stopper, B - fused silica tube, C - graphite crucible,D - metal sample.

Figure 17. An apparatus for installing a graphite thermometer well and lid in agraphite crucible containing a molten metal sample.

A - stainless steel pusher rod, B - silicone rubber gas seal (permits linearmotion of the pusher rod A), C - inlet for purified argon gas that is used inpurging and maintaining positive pressure of the gas during the assembly process,D - silicone rubber stopper, E - stainless steel flange attached to the pusherrod for pressing against the graphite lid and thermometer well during assembly.F - graphite lid for the crucible, G - slit on the pusher rod (the two halvesspring outward to hold the graphite thermometer well and lid while melting themetal sample), H - graphite thermometer well, I - fused-silica tube, J - a partof the fused-silica tube where its I.D. matches closely with the O.D. of thecrucible and its lid so that the lid can be easily guided onto the opening ofthe crucible, K - graphite crucible, L - molten metal sample.

Figure 15. A graphite freezing point cell enclosed inside a fused silica tubewith tube connection to high vacuum, purified argon gas source, and pressuregauge.

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SPRT’s that are to be calibrated at the aluminum point and higher musthave fused silica, sapphire, or ceramic insulation for the resistanceelement and its extension leads. Such high temperature SPRT’s should behandled by procedures that avoid thermally shocking them.

A tube furnace containing the aluminum point cell is controlled about 5°Cabove the freezing point of aluminum until the metal is completely melted.It is convenient to control the furnace temperature automatically and meltthe metal overnight so that the freezing of the metal can be started earlyin the morning and the calibration of two or three test SPRT’s completedduring the same day. Insert the aluminum point check SPRT stepwise intothe cell well. Since the SPRT will cool considerably between the time itis withdrawn from any auxiliary preheat furnace and inserted into thealuminum point cell, the SPRT is heated in the section of the thermometerguide tube that is maintained close to the furnace temperature. The SPRTis inserted initially to a location where its tip is about 3 cm above thegraphite cell lid. After about 5 minutes, the SPRT is inserted anadditional 5 cm and after another 5 minutes, another 5 cm, and so on untilthe tip of the SPRT is at the bottom of the thermometer well. When theSPRT indicates that the sample is about 5°C above the freezing point,change the furnace temperature control settings to control at 5°C belowthe freezing point in order to initiate rapid cooling for nucleation. Whenthe check SPRT indicates recalescence, change the furnace temperaturecontrol settings to control at 1°C to 0.5°C below the freezing point.Withdraw the check SPRT stepwise from the cell, first to a location about3 cm above the graphite cell lid. After about 5 minutes, withdraw the SPRTanother 5 cm,and after another 5 minutes, another 5 cm, and so on untilthe SPRT is completely out of the thermometer guide tube. Next, insertsuccessively into the cell well two fused silica glass rods, eachinitially at room temperature, for about 5 minutes each to freeze a thinmantle of solid aluminum around the thermometer well. Again insert thecheck SPRT stepwise, as described above, into the cell. Within 20 to 30minutes, the readings on the check SPRT should indicate that the cell isat temperature equilibrium. After the readings on the check SPRT arecompleted, the SPRT is removed from the cell stepwise, as described above.The test SPRT’s are then successively inserted stepwise, calibrated, andremoved stepwise as described for the check SPRT. After all of the testSPRT’S have been calibrated, the check SPRT is inserted again into thecell well and measurements made. This second reading at temperatureequilibrium should agree with the first to within ± 0.1 mK.

When SPRT’s are cooled rapidly from the aluminum point to ambienttemperature, lattice vacancies are quenched in and these must be removedbefore the SPRT’s are calibrated at the triple point of water. To relieveany quenched in lattice vacancies, the SPRT’s that have been calibrated atthe aluminum point should be heated in an auxiliary furnace at about 660°Cfor about 30 minutes and then gradually cooled to about 500°C over 3 hoursor more before withdrawing from the furnace to cool at ambienttemperature. See references (43, 45, 70).

3.2.4.2.7 FREEZING POINT OF SILVER

The freezing point of silver is assigned the value 1234.93 K (961,78°C).Metal samples of 99.9999% purity are commercially available in the form ofpellets.

High purity graphite containers have been used successfully with silver.Liquid silver has been found to supercool not more than 0.5°C; hence, itsfreeze can be initiated in the furnace without withdrawing the cell fromthe furnace. See references [3,15,72,98].

Oxygen is known to “dissolve” in liquid silver and lower the freezingpoint. Although the dissociation pressure of Ag 20 is expected to be quitehigh at the freezing point of silver, the lowering of the freezing pointmay be a combination of the solution of Ag 20 and of oxygen in liquidsilver. (The dissociation pressure of Ag 20 is given as 414 atmospheres at507°C.) In a graphite environment at the freezing point of silver, a smallamount of the oxygen will eventually react with the graphite; however, anewly prepared cell should be pumped at high vacuum at about 1000°C for aweek before back filling to one atmosphere with purified argon, nitrogen,or helium. [The first cryoscopic constant of silver is very small(0.000891/K). Consequently, the liquidus point of an ideal silver solutionof 99.9999% purity would be approximately 1.1 mK lower than that of 100%pure silver.]


The freezing-point cell of silver may be assembled by a procedure similarto that used with aluminum. See section 3.2.4.2.6.1.

SPRT’s that are to be calibrated at the silver freezing point must havefused silica, sapphire, or ceramic insulation for the resistance coil andits extension leads. Such high temperature SPRT’s should be handled byprocedures that avoid thermally shocking them.

A tube furnace containing the silver freezing point cell is controlled atabout 5°C above the freezing point until the metal is completely melted.(It is convenient to control the furnace temperature automatically andmelt the metal overnight so that the freezing of the metal can be startedearly in the morning and the calibration of two or three test SPRT’scompleted during the same day.) Insert the silver point check SPRTstepwise into the cell well. Since the SPRT will cool considerably betweenthe time it is withdrawn from any auxiliary preheat furnace and insertedinto the silver point cell, the SPRT is heated in the section of thethermometer guide tube that is maintained close to the furnacetemperature. The SPRT is inserted initially to a location where its tip isabout 3 cm above the graphite cell lid. After about 5 minutes, the SPRT isinserted an additional 5 cm, and after another 5 minutes, another 5 cm,and so on until the tip of the SPRT is at the bottom of the thermometerwell. When the SPRT indicates that the temperature of the sample is about5°C above the freezing point, change the furnace temperature controlsettings to control at 5°C below the freezing point in order to initiaterapid cooling for nucleation. When the check SPRT indicates recalescence,change the furnace temperature control settings to control at 1°C to 0.5°Cbelow the freezing point. Withdraw the check SPRT stepwise from the cellwell, first to a location about 3 cm above the graphite cell lid. Afterabout 5 minutes, withdraw the SPRT an additional 5 cm, and after another 5minutes, another 5 cm, and so on until the SPRT is completely out of thethermometer guide tube. Next, insert successively into the cell well twofused-silica glass rods, each initially at room temperature, for about 5minutes each in order to freeze a thin mantle of solid silver around the

thermometer well. Then, insert again the check SPRT stepwise, as describedabove, into the cell. Within about 20 to 30 minutes, the readings on thecheck SPRT should indicate that the cell is at temperature equilibrium.After the readings on the check SPRT are completed, it is removed from thecell stepwise, as described above. The test SPRT’s are then successivelyinserted stepwise, calibrated, and removed stepwise as described for the-check SPRT. After all of the test SPRT’s have been calibrated, the checkSPRT is inserted again into the cell well and read. This second readingshould agree with the first to within ±0.2 mK.

When SPRT’s are cooled rapidly from the silver point to ambienttemperature, lattice vacancies are quenched in and these must be removedbefore the SPRT’s are measured at the triple point of water. To relieveany quenched in lattice vacancies, the SPRT’s that have been calibrated atthe silver point are heated in an auxiliary furnace at about 960°C for30 minutes or so and then gradually cooled to about 500 ˚C over 3.5 hoursor more before withdrawing from the furnace to cool at ambienttemperature. In order to protect the plat inum of the SPRT fromcontamination by diffusion of metals at high temperatures (above 660°C,the SPRT’s should be enclosed in a platinum tube or other protectivedevice.

3.2.5 CONTROL CHARTS OF CHECK THERMOMETERS

Control charts should be kept for all of the check thermometers associatedwith the various fixed points. Each of these charts will usually consistof a chronological graph of the check thermometer resistance value, R(X),obtained from measurements in the fixed-point cell X, and of the ratio,W(X) = R(X)/R(TPW), of the resistance value R(X) to the resistance value,R(TPW), obtained from measurements in a triple point of water cell.Presumably, such charts have been kept by those involved in precisionthermometry. Entries on such control charts are made each time theparticular fixed point cell is used. Since those involved in precisionthermometry would have used triple point of water cells for their workbased on the IPTS-68 and they would have used W(X), the same control chartcan be continued with the ITS-90. The reason, of course, is that thebehavior of the fixed point cells is independent of the scale. Not all ofthe fixed points of the ITS-90, however, are the same as those of theIPTS-68. The ITS-90 uses some of the IPTS-68 fixed points but it also usesother fixed points. See reference (64).

Some metrologists may not have used W(X) as defined above, but may haveused the W(t) of the IPTS-68. In that case, there will be a discontinuityin their control charts involving W when they implement the ITS-90 andbegin using W(X). The magnitude of the discontinuity will simply be theratio R(273.16 K)/R(273.15 K).

Control charts involving only R(X) as a function of time will not have anydiscontinuity due to the change in the scale. Depending on the temperatureof interest, of course, there may be need to start additional controlcharts.

3.3 RADIATION THERMOMETRY

Above the freezing point of silver (1234.93 K), the ITS-90 is defined interms of Planck’s radiation law. The values of temperatures T 90 on theITS-90 are obtained from the observed ratios of the spectral concentrationsof the radiance L λ of a blackbody at the wavelength (in vacuum) λ at T 90 andat the reference temperature T 90(X) according to eq. (31).

Inside a closed cavity, the radiation densities at different wavelengths λdepend only upon the temperature of the cavity walls. When a practicalradiator is designed with a small hole in the wall to observe theradiation density at λ, there arises the question of how much the observedradiation departs from the blackbody radiation for a radiator design of agiven geometry and material of construction. There are numerous papers onthe theoretical analysis of the emissivities, associated with cavitygeometry and construction materials and descriptions of radiator designsthat have been used in radiation thermometry (8, 9, 34, 35, 54, 77, 87, 89, 95).The emissivities of cavities constructed of specular reflectors anddiffuse reflectors have been analyzed (87). It is expected that at hightemperatures many materials become oxidized and, consequently, becomediffuse reflectors. Although it is difficult to determine the actualtemperature gradients in a cavity, the effect of temperature gradients hasalso been treated (10, 11). The effective emissivity of a graphiteblackbody cavity has been computed to be 0.99997 ± 0.00003 (77).

For radiation thermometer calibrations at the silver, gold, or copperfixed point, the blackbody cavity should be constructed of graphite andsurrounded by the freezing or melting metal contained in graphite toretain the high purity of the metal that is used. [The first cryoscopicconstants of all three of these metals are extremely low (silver:0.000891/K; gold: 0.000831/K; Cu: 0.000857/K). Consequently, the ideal-solution liquidus points of these metals of 99.9999% purity would beapproximately 1.1 mK to 1.2 mK lower than that of 100% pure metals.]

References [27, 55, 56, 57, 62, 77] give some details of construction ofsuitable graphite fixed point blackbody cavities. The metal should beprotected from air using an inert gas, such as argon, nitrogen, or helium,at a pressure slightly above ambient. The graphite container or auxiliarygraphite scavengers can remove small amounts of oxygen impurities. For theblackbody cavity at the platinum point, pure alumina has been used in anoxidizing atmosphere to avoid the reaction between platinum metal andalumina in which oxygen gas is formed and metallic aluminum is dissolvedin the platinum [33,86].

Usually, optical pyrometers or photoelectric pyrometers are used todetermine the ratio of the radiances of a source of unknown temperature withthat of the reference source. The optical system of the instrument isdesigned to focus a nearly monochromatic image of the radiation source ontoa photodetector, which until about the mid 1950’s was only the human eye;now the eye has been replaced in high precision measurements byphotoelectric detectors because of their greater accuracy and theirsuitability for automation of the measurements. Two methods are commonlyused to determine the ratios of spectral radiances. Either the photoelectricpyrometer is designed for comparing the two radiation sources by nulldetection operation, similar in principle to the disappearing filament


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Z

optical pyrometers using suitable neutral filters or sectored discs forattenuating the radiation of one source, or for measuring directly the radiationdensity in terms of the detector output, e.g., photocell current. The latterrequires high stability and linearity of signal processing [34,77). The optics ofthe system may comprise refract ing components ( lenses) or ref lect ingcomponents (mirrors) [28,34,54,57,87].

Equation (31) requires the rat io of monochromatic radiances. Usually,interference filters are used for this purpose. The bandwidth should be narrowwith high transmittance while completely blocking out wavelengths outside thedesired band. The temperature error is smaller the narrower the bandwidth. Thetemperature of the filters should be controlled, since they are sensitive totemperature changes. The photoelectric detector should be protected fromundesired radiations from outside the solid angle defined by the aperture of theblackbody cavity. Where the output of the photocell is used to determine theratio of the radiances, the linearity of the detector should be carefully checkedor calibrated.

For details of optical pyrometer operation and attendant sources of error, seereferences [28,34,54,57,77,87].

4. CALIBRATION OF THERMOMETERS ON THE ITS-90 AT VARIOUS LEVELS OF UNCERTAINTY ANDSOME APPROXIMATIONS OF THE SCALE

In a standards laboratory, the design of apparatus and equipment for calibrationof thermometers on the ITS-90 should be based on the desired accuracy, the number ofthermometers and thermometric instruments that must be calibrated per year, thecost of real izing the ITS-90 (the f ixed points and the measurementequipment), the cost of applying and maintaining the ITS-90, and the cost ofresearch to maintain and make necessary improvements on the realization of theITS-90. In a national standards laboratory, the efforts are directed toward theaccurate realization of the ITS-90.

On 1 January 1990, no laboratory was able to calibrate thermometers over thecomplete range of the ITS-90 in accordance with the strict definition of thescale. Also, it is thought that on that date there was no immediate, widespreadrequirement for “experimental calibration conversion” from the IPTS-68(75) toITS-90 over the complete range. Since the differences between IPTS-68(75) andITS-90 were known, “arithmetical conversions” should have met most of theimmediate requirements. Also, where stable thermometers have been used tomaintain the EPT-76 or parts of the IPTS-68(75), the scales on those referencethermometers could be converted to ITS-90, using the published approximatedifferences between the scales, and then those thermometers can be used tocalibrate other thermometers on the ITS-90. To realize the ITS-90 as definedand for international traceability, however, it is essential for the nationalcalibration laboratory to have all of the fixed-point apparatus and measurementequipment. Furthermore, without continued research and comparison with otherstandards laboratories, the question regarding the accuracy of the realizationof the scale will remain. The ITS-90 temperature calibrations are based on thethermal equilibrium states (vapor-liquid or liquid-solid equilibrium at knownpressures, or vapor-liquid-solid triple points) of pure substances. Substances,however, have some impurity content; the amount must be small enough to havenegligible effect on the measurement of temperature. Obviously, the fixed-pointdevice and the experimental procedure must be designed so that duringcal ibrat ion, the thermometer wi l l be in thermal equi l ibr ium with theequilibrium state of the defining fixed point. A method for checking whether ornot the thermometer is in thermal equilibrium with a metal fixed-point standarddevice is to reduce the immersion in the device a known amount or vary theexperimental conditions. The observed temperature change of the thermometermust correspond with the hydrostatic head effect of the liquid metal in thedevice, or there must be no observed temperature change with experimentalconditions (such as changing furnace temperatures of metal fixed-point cells).

In order to determine the precision of the calibration process, it is essentialto use check thermometers with every calibration. The results of the checkthermometers will show whether the calibration process is “under statisticalcontrol” or not. The accumulated results show the precision of the “gross”calibration process.

Since some parts of this section deal with approximations of the ITS-90, andwill make reference to the scale differences given in table 1, the methods bywhich the table was constructed will be described. The differences ( T90 - T76)between 5 K and 27 K were obtained using the same relation [99] as that used for(T NPL-75 - T 90). namely,

(T 90 - T 76)/mK = - 0.00.56(T 90/K) 2. (40)

The differences (T 90 - T 90) between 14 K and 100 K were obtained by Working Group 4of the CCT by graphical interpolation of data from the published literature. Thedifferences (T 90 - T 68), or (t 90 - t 68), between -200 ˚C and 630 ˚C wereobtained by Working Group 4 of the CCT from published data on two SPRT’s, oneSPRT covering the range, below 0 ˚C, and the other covering the range from 0 ˚Cto 630 ˚C. A polynomial of the form:

8(t 90 - t 68)/˚C = ∑ ai (t 90/630) i (41)

i=1

was fitted to the data from -200 ˚C to 630 ˚C and the coefficients are:a1 = -0.148759 a 5 = -4.089591a2 = -0.267408 a 6 = -1.871251a3 = 1.080760 a 7 = 7.438081a4 = 1.269056 a 8 = -3.536296

The polynomial with these coefficients reproduces the tabulated differences [83]to within 1 mK above 0˚C and to within 1.5 mK below 0˚C. The differences(T 90 - T 68) between 630˚C and 1064˚C were obtained by Working Group 4 bygraphical interpolation from published data [14). The differences (T 90 - T 68)above 1064 ˚C were obtained from the equation:

(t 90 - t 68)/˚C - 0.25 [(t 90/˚C + 273.15)/(1337.33)] 2. (42)

In section 3, we discussed the direct realization of the ITS-90, using thestandard instruments of the scale, i.e. , the realization of the scale at thelowest level of uncertainty. Of course, even the standard interpolatinginstruments used at the same thermodynamic temperature will indicate temperaturesthat differ slightly due to the devices having nonideal behavior and the scale’sbeing expressed in as simple a form as possible. The differences in indicatedtemperatures, however, are negligible for all practical purposes, being of theorder of ≤ ± 0.5 mK for temperatures above about 5 K (i.e., assuming no errors incalibration). The realization of the ITS-90 in the liquid helium range oftemperatures (0.65 K to 5.0 K) through helium vapor pressure- temperaturerelations can be accurate to about ± 0.1 mK or ± 0.2 mK.

For nonstandard types of thermometers used to approximate the ITS-90, the level of

uncertainty is higher than the numbers just given because of the inherent

instability of these thermometers. In all cases, these types of thermometers are

calibrated by comparison with one or more standard instruments of the scale, e.g.,

vapor-pressure thermometry; vapor-pressure thermometry and gas thermometry; vapor-

pressure thermometry, gas thermometry, and platinum resistance thermometry; gas

thermometry and plat inum resistance :thermometry; plat inum resistance

thermometry; or pyrometers or spectral radiometers.

The NIST offers calibration services for various thermometers and pyrometers

covering the range from 0.65 K to 4200 ˚C (see NIST SP 250). Of this range, the

Chemical Process Metrology Division offers calibrations for contact thermometers

covering the range from 0.65 K to 2400 K, and the Radiometric Physics Division

offers calibrations for non-contact thermometers (radiation pyrometers) covering

the range from 1234.93 K (961.78 ˚Q to 4200 ˚C. Calibrations of only contact-

type. thermometers will be discussed here. The types of contact thermometers

calibrated include rhodium-iron resistance thermometers (RIRT’s), germanium

resistance thermometers (GRT’s), standard platinum resistance thermometers

(SPRT’S), thermocouples (t/c), l iquid-in-glass thermometers, thermistor

thermometers, industrial platinum resistance thermometers (IPRT’s), digital

thermometers, and other special thermometers that are compatible with the NIST

calibration equipment.

4.1 RHODIUM-IRON RESISTANCE THERMOMETERS

At temperatures below 13.8033 K, RIRT’s and GRT’s are, at the present time, the

only thermometers that are suitable for precision temperature measurements. Also,

RIRT’s (and to a lesser extent GRT’s) are suitable for use at temperatures up to

the triple point of neon (24.5561 K). In the range from 0.65 K to about 25 K,

RIRTs have -reproducibilities of about ± 0.2 mK. Consequently, RIRT’s don’t

degrade the realization of the ITS-90 significantly.

When the ITS-90 is realized, as defined, at NIST, some NIST RIRT’s will be

calibrated at many temperatures through the Use of vapor-pressure thermometry and

gas thermometry to produce reference-standard RIRT’s, which wil l be

periodically recalibrated. The resistance temperature data of these RIRT’s will

be represented by a polynomial.

Customer RIRT’s are calibrated by comparison with reference-standard RIRT’s. A

polynomial is fitted by the method of least squares to the RIRT resistance-

temperature data so obtained and the results are reported in terms of the

polynomial that is selected.

Until the NIST completes the development of the CVGT and vapor-pressure

thermometry apparatus with which the reference-standard RIRT’s will be calibrated,

calibrations of customer RIM are performed by comparison against reference-

standard RIRT’s that have been calibrated on the NPL-75 Scale [13) or on the

EPT-76 and converted to the ITS-90.

To convert a calibration of an RIRT on the EPT-76 to an approximate calibration

on the ITS-90, use the EPT-76 calibration res instance temperature data change

the T 76 values to T 90 values Using the (T 90 - T 76) differences given in table 1, or

calculated with eq (40), to produce a new set of. resistance-temperature values,

and then fit a polynomial of the required degree to these data. Using the

coefficients of the polynomial so determined, produce the desired calibration table.

A typical calibration report on the EPT-76 and one on the ITS-90 are given in

appendix 3, sections 6.3.6 and 6.3.7, respectively.

4.2 GERMANIUM RESISTANCE THERMOMETERS

GRT’s are comparable with, but not quite as stable as RIRT ’ s. They are calibrated

in a manner similar to that of the RIRT’s and their results similarly reported.

At NIST, customer GRT’s are calibrated by comparison with reference to standard

RIRT’s.

Anyone with a calibration on the EPT-76 may convert it to an approximate ITS-90

calibration by the same procedure as just outlined for RIRT’s.

4.3 STANDARD PLATINUM RESISTANCE THERMOMETERS

Both capsule and long-stem type SPRT’s are calibrated at the NIST. They will be

discussed separately.

4.3.1 CAPSULE SPRT’S (13.8033 K TO 429.7485 K OR 505.078 K)

For temperatures in the range from 13.8033 K to 273.16 K, capsule SPRT’s are the

most suitable thermometers. NIST has reference capsule SPRT’s that have been,

or will have been, calibrated at the defining fixed points in this range. Those

SPRT’s are used in calibrating customer thermometers by the comparison technique

over the range from about 13 K to 84 K. The temperatures at which comparisons

are made are at, or within a few mK of, the defining fixed-point temperatures

of the ITS-90 and at temperatures approximately mid-way between the fixed-point,

values. Data at the temperatures intermediate to the fixed-point values are

incorporated as a check on the calibration process. At and above the argon

triple point (83.8058 K), customer capsule SPRT’s are calibrated by the fixed-

point method. See section 6.3 for an example of how to calculate the

coefficients of the deviation functions.

4.3.2 LONG-STEM TYPE SPRT’S (83.8058 TO 1234.93 K)

Long-stem type SPRT’s are used in the range from 83.8058 K to 1234.93 K. Two

different long-stem type SPRT’s are required to cover this whole range, one type

being the customary SPRT having a nominal 25.5 0 resistance at 0 *C and used in


the range from 83.8058 K to 692.677 K or to 933.473 K, and the second type havinga somewhat longer stem and having a nominal 0.25 Ω or 2.5 Ω resistance and usedin the range from 273.15 K to 1234.93 K. Such thermometers are very stable ifhandled carefully, In this range of temperature, SPRT’s are calibrated by thefixed-point method, different sets of fixed points being required for differenttemperature subranges. The required fixed points for the different subrangeswere specified in section 2 of this document. In the fixed-point method,corrections for hydrostatic heads and gas pressure over the metals, of thefreezing point and melting-point cells are made (see table 6). Similarly,corrections for hydrostatic heads present in metal and in gas triple-point cellsare made. As a check on the accuracy of the calibration, measurements are madeat one or more “redundant” defining fixed points lying within the temperaturerange of calibration or at a well characterized secondary fixed point, such asthe cadmium freezing point, that l ies within the temperature range ofcalibration. The value of the temperature of a check point calculated from thecalibration constants should agree closely with the accepted value of thatpoint. If not, then either an error was made in the calibration, one or morefixed point cells are defective, or the thermometer is defective.

The procedures indicated in section 3.2 for realizing the various fixed-pointtemperatures and for handling SPRT’s are followed lowed care fully duringcalibration of platinum thermometers, especially so for calibration at thealuminum and silver freezing points (see sec. 3.2.4.2.7.1 for a discussion oflattice defects). See section 6.3 for an example of how the coefficients of thedeviation functions are calculated from the data for the two sets of fixedpoints.

4.3.3 C O N V E R S I O N O F T H E I P T S - 6 8 C O N S T A N T S A N D W( T 6 8 ) T A B L E S T OAPPROXIMATE ITS - 90 CONSTANTS AND W( T90) TABLES

For SPRT’s that have been calibrated recently on the IPTS-68(75), theircalibrations may be. converted to approximate, calibrations on the ITS-90 attemperatures between the triple point of equilibrium hydrogen (13.8033 K) andthe freezing point of zinc (692.677 K).

To make the conversion, first obtain values of W( T68), i.e. R( T68)/ R(O˚C), fromthe, IPTS-68(75) calibrations, at values of T 68 corresponding to the temperaturesof the relevant fixed points of the ITS-90 in the appropriate range in which theconversion is desired. [Note : for a fixed point, the temperature values T68 andT90 are different, but the “hotness“ is the same and so the resistance of a givenSPRT remains unchanged. The temperature values on the two scales are defined tobe the same only at the triple point of water and at the absolute zero of thetemperature scales. Due to the nature of the scales, however., there are othertemperature values of these scales that are also the same, which are fortuitous.See fig. 1, which shows the difference of t 90 and t 68 as a function of t 90. ] Usingthese values of W( T68) at the appropriate ITS-90 fixed-point temperatures,calculate values of W( T90), i.e., R( T90)/R(273.16 K), by dividing the values ofW( T68) at the appropriate fixed-point temperatures by the value of W(273.16 K),i.e., the, value of W( T68) at the triple point of water. Table 8 shows samples ofsuch conversions for a capsule-type SPRT and for a long-stem type SPRTcalibrated on the IPTS-68(75). The calibration constants of the IPTS-68(75)equations for the two SPRT’s are given also in table 8. The values of W( T90) so

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Difference Between ITS-90 Calibration and IPTS-68 CalibrationConverted to ITS-90, Chino RS8YA-5, 25.5 ohm

0.5

0.4

0.3

0.2

0.1

0.0

-0.1

50 100

T90-T90(68)mK

150 200 250 300

Temperature, K

350 400 450 500 550 600 650 700

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

Figure 18. Differences between T90 and (T90) as calculated from IPTS-68 calibration for the long-

Capsule SPRT (S/N 1812284)

Fixed Point T68/K W(T68) meas.. T90/K W( T90) calc.* W(T 90) meas..

e-H 2 TP 13.81 0.00119822 ** 13.8033 0.00119817 0.00119721e-H 2 BP 17.04200 0.00231120 ** 17.0357 0.00231111 0.00231049e-H 2 BP 20.280 0.00425962 ** 20.2711 0.00425945 0.00425815

Ne TP 24.5616 0.00848337 ** 24.5561 0.00848303 0.00848391o2 TP 54.361 0.09182547 ** 54.3584 0.09182180 0.09182102Ar TP 83.79723 0.21598575 ** 83.8058 0.21597714 0.21597795Hg TP 234.3086 0.84421212 ** 234.3156 0.84417846 0.84417781

H2O TP 273.16 1.00003987 ** 273.16 1.00000000 1.00000000Ga MP 302.9218 1.11815352 ** 302.9146 1.11810895 1.11810896I n FP 429.7848 1.60970773 ** 429.7485 1.60964355 1.60964566Sn FP 505.1181 1.89263856 ** 505.078 1.89256311 1.89256311

Long-Stem SPRT (S/N RS8YA-5):

Ar TP 83.79723 0.21592943 ** 83.8058 0.21592084 0.21592281Hg TP 234.3086 0.84418993 ** 234.3156 0.84415637 0.84415625

H2O TP 273.16 1.00003976 273.16 1.00000000 1.00000000Ga MP 302.9218 1.11817175 *** 302.9146 1.11812729 1.11812699I n FP 429.7848 1.60980450 *** 429.7485 1.60974050 1.60974062Sn FP 505.1181 1.89278557 505.078 1.89271033 1.89271033Zn FP 692.73 2.56885786 692.677 2.56875573 2.56875573

* Values of W( T90) calc. were obtained by conversion of corresponding values ofW( T68) meas.

** These values were calculated from NBS-IPTS-68 calibration constants, based onthe NBS wire scale and calibration at the triple point of water and the freezingpoint of tin (and the freezing point of zinc for the long-stem SPRT).

*** These values were calculated from IPTS-68 calibration constants determinedfrom fixed points.

Table 9. Values of W( T68) and W( T0) for various fixed-point temperatures T68 and

Table 8. Example of conversion of calibrations of SPRT’s on the IPTS-68 toapproximate calibrations on the ITS-90

Capsule SPRT, S/N 1812284 : e-H 2 TP to Sn FP

IPTS-68 CALIBRATION CONSTANTS

R(0 ˚C) = 25.4964808 a = 3.9262754x10 -3 d = 1.4964667A1 = 1.6314209x10 -4 B1 = -8.7377446x10 -7 C1 = 4.0321350x10 -7

D1 = 1.4525327x10 -4

A2 = 2.1616630x10 -4 B2 = -1.7113512x10 -7 C2 = 6.6163769x10 -8

D2 = 2.2572375x10 -10

A3 = 4.5449999x10 -7 B3 = -7.7242433x10 -6 C3 = 3.9028516x10 -8

A4 = 3.0860000xl0 -7 C4 = 1.0880791x10 -4

ITS-90 CALIBRATION CONSTANTS CONVERTED FROM THE IPTS-68 CONSTANTS

R(273.16) = 25.4974973

a1 = -2.5239001x10 -4 b1 = 1.2277862x10 -4 C1 = -2.3783015x10 -6

ag = -2.5287142x10 -4 bg = 1.1130131x10 -5 C2 = -4.3892024x10 -6

C3 = -1.5608728x10 -6

C4 = -2.1374663x10 -7

C5 = -1.0344171x10 -8

Long-Stem SPRT. SIN RS8YA-5 : Ar TP to Zn FP

IPTS-68 CALIBRATION CONSTANTS

R(0 ˚C) = 25.5086208 A = 3.9856609x10 -3 B = -5.8762238x10 -6

a = 3.9268986x10 -3 d = 1.49640322A4 = 2.6581418x10 -14 C4 = 9.3183900x10 -7

ITS-90 CALIBRATION CONSTANTS CONVERTED FROM THE IPTS-68 CONSTANTS

R(273.16 K) = 25.5096386a4 = -9.3225823x10 -5 b4 = -9.9914440x10 -6

a8 = -9.1058813x10 -5 b8 = -7.6061559x10 -6

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4.3.4 UNCERTAINTIES OF CALIBRATIONS AND THEIR PROPAGATION

Both systematic and random errors of measurements introduced in a calibrationare propagated throughout the temperature range of the calibration. It is thetotal uncertainty arising from both of these types of errors, however, that isof interest to the customer and user of a calibrated thermometer. Internationalcomparisons of fixed-point cells below 90 K [79] and other data suggest that theuncertainties (at the 10 level) in the realizations of the defining fixed pointsof the ITS-90 are about ± 0.2 mK for the triple points 0f hydrogen and neon, ±0.1 mK for the triple point of oxygen through the melting point of gallium, ±0.7 K at the freezing point of indium, ± 1 mK from the freezing point of tinthrough the freezing point of aluminum, and ± 2 mK for the freezing point ofsilver.

The uncertainty of temperature measurements in the liquid helium range (0.65 Kto 5.0 K) resul ts f rom the uncerta inty of the hel ium vapor-pressuremeasurements. The uncertainty (at the 1 o level) throughout this range oftemperature is estimated to be approximately ± 0.1 mK to ± 0.2 mK.

For the CVGT, the uncertainty in the measured temperature over its temperaturerange (3.0 K to 24. 5561 K) arises from uncertainties of realizations of thetriple points of neon and of equilibrium hydrogen, of the measurement of theCVGT gas pressure and of the measurement of the vapor pressure of helium. Theuncertainty (at the 1 o level) throughout this range of temperature is estimatedto be approximately ± 0.1 mK to ± 0.2 mK. Uncertainties introduced by aparticular CVGT design may add to these uncertainties.

In the calibration of SPRT’s over any given subrange, the possible error in therealization of each of the fixed points and any error of measurement must beconsidered and they will be propagated independently of that incurred at theother fixed points involved. The total uncertainty of measurements at a giventemperature is then the root-mean-square of the appropriate contributinguncertainties. Curve, showing the propagation of a ± (unit error ) incurred ateach of the defining fixed points of the two major ranges are shown in figures19 and 20. Figure 19 shows the propagation of errors associated with the fixedpoint, below 213.16 K; and figure 20 shows curves for the fixed points used inthe calibration of SPRT’s in the range from 273.15 K to 1234.93 K. The labelson the various curves indicate the fixed-point in which there is the unit errorin its temperature, and the other fixed points without error. As an example,consider the curve labelled Sn(Ag, Al, Zn) of figure 20. The symbol Sn indicatesthat the unit error occurs in the Sn freezing-point temperature; that is clearlyindicated by a unit offset of the curve at that point. The symbols inparenthesis,i.e., (Ag, Al, Zn), indicate that the Ag, Al, and Zn freezing pointswere made at those fixed-point temperatures without error. Also, it is assumedthat the measurements at the triple point of water were without error. The otherlabelled curves are similarly interpreted. The straight lines labelled TPW showthe errors propagated for an error of ± 0.1 mK made by the user in the triplepoint of water.

4.3.5 ESTIMATES OF POSSIBLE ERRORS INTRODUCED BY EXTRAPOLATIONS BEYOND THERANGE OF CALIBRATION

It is unwise and is poor practice to use any thermometer beyond the temperaturerange over which it was calibrated. Nevertheless, some users persist in doingjust that. In some cases, especially if the extrapolation is for only a fewkelvins, the error introduced may be rather small. The errors of some typicalextrapolations calculated and depicted for NIST SPRT’s, are shown in figures21, 22, 23, 24, and 25.

The curve in figure 21 shows the error introduced for a NIST SPRT byextrapolating the deviation function, determined from calibration over the rangefrom the triple point of argon to the triple point of water, downward from theargon triple point to 54 K. Extrapolating downward to about the boiling pointof nitrogen (77 K) results in a fairly insignificant error in this case and,thus, can be done with the usual caution that some thermometers may not be asgood as that of figure 21.

Figure 22 depicts the results for another NIST SPRT. The curve shows the errorintroduced by extrapolating the deviation function, determined from calibrationover the range from the triple point of mercury to the melting point of gallium,downward from the mercury triple point to 84 K.

Figure 23 displays the results for the same NIST SPRT as used for figure 22, butthe curve in this case shows the error introduced by extrapolating the deviationfunction, determined from calibration over the range from the triple point ofmercury to the melting point of gallium, downward from the mercury triple pointto only 200 K. A sizable error is shown for observations that would be made atDry Ice temperatures (-78 ˚C).

Figure 24 depicts the results for several NIST SPRT’s, but the curves in thiscase show the errors introduced by extrapolating their deviation functions,determined from calibration over the range from the triple point of water to thefreezing point of zinc, downward from the triple point of water to -50 ˚C.

Figure 25 displays the results for several NIST SPRT’s, but in this case thecurves show the errors introduced by extrapolating their deviation functions,determined from calibration over the range from the triple point of water to thefreezing point of zinc, upward from the freezing point of zinc to 934 K (660 ˚C).

As a general rule and good practice, one should never extrapolate any of theITS-90 deviation functions beyond their range of application. If however, theestimated uncertainty introduced by extrapolating a deviation function beyondthe range of calibration is acceptable, then the user may do so, but with theknowledge that his thermometer may yield results with a larger uncertainty thanthat estimated. The user that makes such extrapolations should realize that notall SPRT’s wi1l behave as indicated in figures 21 through 25. The resultsdepicted in these figures are examples only and are valid for only those SPRT’sindicated. Other SPRT’s may be better or worse.

obtained may then be used with the appropriate relations described in section 2to obtain the constants of the ITS-90 deviation equations for the SPRT’s. Intab1e 8 we list the value of the deviation constants that were calculated from thesample data presented there. For comparison, values of the conversion from W( T68) to

W(T90) as well as measured values of W( T90), for the various relevant fixed-point

temperatures T68 and T90, respectively, are given in table 9. The deviations in the

values of the last two columns of table 9 for the capsule SPRT reflect theinconsistency between the NBS-IPTS-68(75) wire scale and the difference betweenthe IPTS-68(75) and the ITS-90 as given in table 1. Note that for the long-stemSPRT, the zero deviations for tin and zinc are a consequence of those fixedpoints having been used in both cases and the

conversion process having been consistent. The deviations for the other fixedpoints (Ar, Hg, Ga, and In) reflect the non-uniqueness of this SPRT and possibleerrors incurred in measurements at those fixed points.

The results of tables 8 and 9 for the long-stem SPRT, with regard to thedifferences between temperatures determined from an actual ITS-90 calibrationand those deterimined from an IPTS-68 calibration but then calculated forapproximate ITS-90 values, are shown in figure 18. Note that at temperaturesabove 273.16 K. the zero deviation of figure 18 is a consequence of the fact thatthe same fixed points (tin and zinc ) have been used in both cases and theconversion process having been consistent.

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1.5

1.0

0.5

0.0

-0.5

-1.0

-1.5

1.5

1.0

0.5

0.0

-0.5

-1.0

-1.5

250 350 450 550 650 750 850 950 1050 1150 1250

Temperature, K

Error in degreesper degree error in calibration

ITS-90 Propagation of Calibration Errorsin Platinum Resistance Thermometry

Sn(Ag,Al,Zn)Zn(Ag,Al,Sn)

Al(Ag,Zn,Sn)

Ag(Al,Zn,Sn)

TPW


Figure 19. Propagation of errors from errors of calibration of SPRT’s between 13.8033 K and273.16 K. The curves show the error in the temperature values caused by a unit positive or unitnegative error of calibration at each of the fixed points in the range, namely, the triple pointsof equilibrium hydrogen, neon, oxygen, argon, and mercury. The calibration at the triple point ofwater is assumed to have been made without error. The curves are identified by the fixed point

ITS-90 Propagation of Calibration Errors in Platinum Resistance Thermometry

errorin mK

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

-1.5

-2.0

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

-1.5

-2.0

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

-1.5

-2.0

Temperature, K

0 25 50 75 100 125 150 175 200 225 250 275

20.3(e-H2, 17, Ne, O2, Ar, Hg)

17(e-H2, 17, Ne, O2, Ar, Hg)Ar(e-H2, 17, 20.3, Ne, O2, Hg)

Hg(e-H2, 17, 20.3, Ne, O2, Ar)

e-H2(17, 20.3, Ne, O2, Ar, Hg)

O2(e-H2, 17, 20.3, Ne, Hg, Ar)

Ne(e-H2, 17, 20.3, O2, Ar, Hg)

Figure 20. Propagation of errors from errors of calibration of SPRT’s between 273.15 K and1234.93 K. The curves show the error in the temperature values caused by a unit positive or unitnegative error of calibration at each of the fixed points in the range, namely, gallium, indium,tin, zinc, aluminum, and silver points. The calibration at the triple point of water is assumed tohave been made without error. The curves are identified by the fixed point with error outside theparenthesis and the three fixed points without error inside the parenthesis. Also included in thisfigure are error curves for errors made by the user at the triple point of water; these curves

Z-180

Z

Figure 21. Error curve for a NIST SPRT; the curve shows the error introduced by extrapolating itsdeviation function, determined from calibration over the range from the triple point of argon tothe triple point of water, downward from the triple point of argon to 54K.

ITS-90, 25.2 ohm Capsule PRT 1812284Oxygen Subrange - Extrapolated Argon Subrange

0.1

0.0

-0.1

-0.2

-0.3

-0.4errorin mK

-0.5

-0.6

-0.7

-0.8

-0.9

-1.0

50 75 100 125 150

Temperature, K

175 200 225 250 275

-1.0

-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

ITS-90, Chino Model R800-2, RS8YA-5, 25.5 ohmAr to T3 Subrange - Extrapolated Hg to Ga Subrange

20

15

10

errorin mK

5

0

-5

275250225200175150

Temperature, K

12510075

50

15

10

5

0

-5

Figure 22. Curve for a NIST SPRT that shows the error introduced by extrapolating its deviationfunction, determined from calibration over the range from the triple point of mercury to themelting point of gallium, downward from the triple point of mercury to 84K

Z-181

ITS-90, Chino Model R800-2, RS8YA-5, 25.5 ohmAr to T3 Subrange - Extrapolated Hg to Ga Subrange

1.5

1.0

0.5errorin mK

0.0

-0.5

200 205 210 215 220 225 230 235 245

Temperature, K

250 255 260 265 270 275

-0.5

0.0

0.5

1.0

1.5

240


Figure 23. Curve for the NIST SPRT of figure 22 that shows the error introduced by extrapolatingits deviation function, determined from calibration over the range from the triple point ofmercury to the melting point of gallium, downward from the triple point of mercury to only 200 K.

Figure 25. Curves for several NIST SPRT’s that show the errors introduced by extrapolating theirdeviation functions, determined from calibration over the range from the triple point of water tothe freezing point of zinc, downward to the triple point of water to -50˚C.

0.0

-0.5

-1.0

-1.5

-2.0

-2.5

-3.0

Temperature, °C

errorin m°C

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

ITS-90, 25.5 ohm PRTsAr Subrange - Extrapolated Zn Subrange

-50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0

30

31

32

34

35

Z-182

Z

4.4 THERMOCOUPLES (77 K TO 2400 K)

There are numerous letter-designated types of thermocouples. The Type Sthermocouple was the standard instrument of the IPTS-68(75) in the range from630.74 ˚C to 1064.43 ˚C, but it is not a standard instrument of the ITS-90.Customer thermocouples are calibrated at NIST by using a set of temperaturefixed points, by comparison with SPRT’s, or by comparison with reference-standard thermocouples that have been calibrated either by comparison with anSPRT or a radiation pyrometer, or through the use of fixed points. For detailsof the calibration procedures and of the uncertainties involved, see NIST SP250-35 [22] and NIST Monograph 175 (23] (or Monograph 125 (82]).

Usually, the calibration data for most types of thermocouples are analyzedrelative to reference tables, such as those given in NBS Monograph 125 [82].Monograph 125, of course, has reference tables for thermocouples based on theIPTS-68(75). This monograph has been revised and updated to give referencetables for all letter-designated thermocouples based on the ITS-90. The revisedversion of Monograph 125 is Monograph 175 (23) and it supersedes Monograph 125.

The electromotive-force-temperature data for a thermocouple calibrated on theIPTS-68(75) can be converted to an approximate ITS-90 calibration through theuse of the differences ( t 90 - t 68,) given in table 1 of this document and the Svalues in mV/˚C for the relevant thermocouple given in Monograph 175 orMonograph 125. An example of this conversion is given in table 10. A typicalcalibration report is presented in appendix 3 (see sec. 6.3.8).

4.5 LIQUID-IN-GLASS THERMOMETERS

Liquid-in-glass thermometers have uncertainties of realization as small as ± 30mK in the temperature range from 0˚C to about 100 ˚C, but deteriorates atlower and higher temperaures. Liquid-in-glass (primarily,Mercury-in-glass)thermometers are calibrated at NIST by comparison with SPRT’s in liquid baths ofvarious kinds that cover different temperature ranges. For details of thecalibration procedures and of the uncertainties involved, see NIST SP 250-23(105]. An example of a calibration report, based on the IPTS-68(75), of aliquid-in-glass thermometer is given in appendix 3 (see sec. 6.3.9). Acalibration report for the same thermometer, with the IPTS-68(75) calibrationconverted to an approximate ITS-90 calibration through the use of (t 90 - t 68)differences given in table 7 is given also in appendix 3 (see sec. 6.3.10).

4.6 INDUSTRIAL PLATINUM RESISTANCE THERMOMETERS

Industrial platinum resistance thermometers (IPRT’s) are designed primarily foruse in the temperature range from about 77 K (approximate liquid nitrogenboiling point) to 500 ˚C. Typically, the manufacturer of IPRT’s quotes minimuminstabi l i t ies of the IPRTs at the ± 0. 1 K level over this range oftemperatures. Some IPRT’s may be somewhat better than this but others may beconsiderably worse. As seen from table 1, the maximum difference of (T 9o - T 68)below 500˚C is about 0.08 K, and therefore the difference in temperature due to the change in temperature scales is within theinstability of many IPRT’s. Continued use of the IPTS-68(75) and of equationsand standards [American Society for Test ing and Mater ia ls (ASTM)Standard,E1137,and International ElectrotechnicalCommission (IEC) Standard,Publication 751] referenced to the IPTS-68(75),therefore, would result in anincrease in uncertainty of temperature of only about 0.1 K if the temperature

Figure 25. Curves for several NIST SPRT’s that show the errors introduced by extrapolating theirdeviation functions, determined from calibration over the range from the triple point of water tothe freezing point of zinc, upward from the freezing point of zinc to 934 K (660˚C). Also shown aresubrange inconsistencies for the subrange triple point of water to zinc, relative to the subrange

Table 10. Example of a conversion of calibration values of a type K thermocoupleon the IPTS-68 to an approximate calibration on the ITS-90

were expressed as being on the ITS-90. (Note: the ASTM and the IEC areconverting their respective IPRT tables from the IPTS-68(75) to the ITS-90. ASTMCommittee E-20 on Temperature Measurements is responsible for this conversionfor the ASTM).

When IPRT’s are calibrated on the ITS-90, of course, they may be calibrated inthe same manner as is used for SPRT’s. A better method of calibrating IPRT’s,however, is to obtain resistance-temperature data by comparison with acalibrated SPRT at numerous temperatures the range of interest and then fit apolynomial in t 9o to R( t 90 ) /R(0˚C),or to R( t 90 ) /R(0.0l ˚C) data by a least squares technique.

4.7 THERMISTOR THERMOMETERS, DIGITAL THERMOMETERS, AND OTHER TYPES OFTHERMOMETERS.

Thermistor thermometers, digital thermometers (with resistance, thermocouple, ordiode sensors), and other types of thermometers are calibrated at NIST bycomparison with SPRT’s in liquid baths. The calibration procedures followed aresimilar to those used with liquid-in-glass thermometers. The uncertainties ofcalibration range from as small as ± 2 mk for thermistor thermometers to tenths

Calibration Values Calibration Valueson IPTS-68 on IPTS-90

t 68 emf68 S t 90- t 68 ∆ t 90 emf90a

(˚C) (mV) (mV/˚C) (˚C) [-S•( t 90- t 68)] (˚C) (mV)Monograph Table 1 (mV)

1250.0 0.000 0.0395 0.000 0.000 0.0 0.000

100.0 4.092 0.414 -0.026 -0.001 100.0 4.093200.0 8.130 0.0400 -0.040 -0.002 200.0 8.132300.0 12.195 0.0415 -0.039 -0.002 300.0 12.197400.0 16.383 0.0422 -0.048 -0.002 400.0 16.385500.0 20.633 0.0426 -0.079 -0.003 500.0 20.636600.0 24.904 0.0425 -0.115 -0.005 600.0 24.909700.0 29.136 0.0419 0.20 0.008 700.0 29.128800.0 33.288 0.0410 0.34 0.014 800.0 29.128900.0 37.338 0.0400 -0.01 0.000 900.0 37.338

1000.0 41.281 0.0389 -0.19 -0.007 1000.0 41.2881100.0 45.118 0.0378 -0.26 -0.010 1100.0 45.128

a emf90 - emf68 - ∆

3 . 0

2 . 0

1 . 0

0 . 0

1 . 0--

2 . 0--

3 . 0--

4 . 0--

5 . 0--

3 . 0

2 . 0

1 . 0

0 . 0

1 . 0--

2 . 0--

3 . 0--

4 . 0--

5 . 0--

32

35

34

33

31

30

errorin mK

ITS-90, 25.5 ohm PRT’sAl Subrange - Extrapolated Zn Subrange

Temperature, K

250 350 450 550 650 750 850 950

Z-183


5. REFERENCES

[1] Ancsin, J., Vapour Pressures and Triple Point of Neon and the Influenceof Impurities on these Properties, Metrologia 14 , 1-7 (1978)

[2] Ancsin, J., Thermometric Fixed Points of Hydrogen, Metrologia 13 , 79-86(1977)

[3] Ancsin, J., A Study of the Realization of the Melting and Freezing Points ofsilver, Metrologia 26 , 167-174 (1989).

[4] Ancsin, J., Melting Curves and Heat of Fusion of Indium , Metrologia 21, 7-9(19 85).

[5] Barber, C. R., Handley, R. and Herington, E . F. G. The Preparation and Useof Cells for the Realization of the Triple Point of Water , Brit. J. Appl Phys..2, 41-44 (1954).

[6] Barber, C. R. , A Proposal for a Practical Scale of Temperature Below 20 K,Temperature , . Its Measurement and Control in Science and Industry , Edited by H.H. Plumb, Vol. 4, Part 1, pp. 99-103 (Instrument Society of America, Pittsburgh,1972).

[7] Barrick, P. L., Brown, L. F., Hutchinson, H. L., and Cruse, R. L.,ImprovedFerric Oxide Gel Catalysts for Ortho-Parahydrogen Conversion, Edited by K. D.Timmerhaus, Vol. 10, paper D-1, 131-189 (Plenum Press, New York, NY, 1965).

[8] Bauer, G., and Bischoff, K., Evaluation of the Emissivity of a Cavity Sourceby Reflection Measurements, Applied Optics 10 , 2639-2643 (1971).

[9] Bedford, R.E. , Effective Emissivities of Blackbod Cavities – A Review,Temperature , Its Measurement and Control in Science and Industry , Edited by H. H.Plumb, Vol. 4, Part 1, pp. 425-434 (Instrument Society of America, Pittsburgh,PA, 1972).

[10] Bedford , R. E . and Ma, C. K., Emissivities of Diffuse Cavities, II:Isothermal and Nonisothermal Cylindro-cones, J. Opt. Soc. Am. 65, 565-572 (1974).

[11] Bedford , R. E. and Ma, C. K., Emissivities of Diffuse Cavities: Isothermaland Nonisothermal Cones and Cylinders, J. Opt. Soc. Am. 64, 339-349 (1974).

[12] Belecki, N. B., Dziuba R. F., Field, B.F., and Taylor, B. N., Guidelines forImplementing the New Representations of the Volt and Ohm Effective January 1,1990, NIST Technical Note 1263 (June 1989).

[13] Berry , K. H. NPL- 75: A Low Temperature Gas Thermometry Scale from 2. 6 Kto 27 . 1 K, Metrologia 15 89 -115 (1979).

[14] BIPM Com. Cons. Thermometrie, 17, 1989, in press.

[15] Bongiovanni, G., Crovini, L. and Marcarino P., Effects of Dissolved Oxygenand Freezing Techniques on the Silver Point, Metrologia 11, 125-132 (1975).

[16] Bonhoure, J. and Pello, R., Temperature du Point Triple du Gallium,Metrologia 19 15-20 (1983).

[17] Bonhoure, J. and Pello, R. , Points Triples de l’Argon et du Methane:Utilisation de Cellules Scellees, Metrologia 16 95-99 (1980).

[18] Bonhoure, J. and Pello, R., Temperature of the Triple Point of Methane,Metrologia 14 1 75-177 (1978).

[19] Bonhoure, J. and Terrien, J. , The New Manobarometer of the BureauInternational des Poids et Mesures, Metrologia A, 59-68 (1968).

[20] Bonnier, G. and Hermier, Y. , Thermal behavior of thermometric sealed cellsand of a multi-compartment cell, Temperature , Its Measurement and Control inScience and Industry , Edited by J . F . Schooley, Vol. 5, Part 1, pp. 231-237(American Institute of Physics, New York, 1982).

[21] Bonnier, G. and Moser, A., Development at the Institut National deMetrologie of sealed cells as IPTS fixed points, Measurement (IMEKO) 1 143-151(1983).

[22] Burns , G. W. and Scroger, M. G., The Calibration of Thermocouples andThermocouple Materials, NIST Special Publication 250-35 (April 1989).

[23] Burns, G. W. and Scroger, M. G. , Temperature-electromotive Force ReferenceFunctions and Tables for Letter-designated Thermocouple Types Based on the ITS-90, NI ST Monograph 175 (1990).

[24] Cataland, G., Edlow, M. H., and Plumb, H. H., Recent Experiments on LiquidHelium Vapor Pressure Measurements from 2 ˚K to 4 ˚K, Temperature , ItsMeasurement and Control in Science and Industry , Edited by F. G. Brickwedde, Vol.3, Part 1, pp. 413-417 (Reinhold Publishing Corporation, New York, 1962).

[25] Chappuis, P., Etudes sur le Thermometre a Gaz et Comparison des Thermometresa Mercure avec le Thermometre a Ga., Trav. et Mem. BIPM 6 1-125 plus 187 pages ofobservations (1888).

[26] Chattle , M. V., Rusby , R. L., Bonnier, G., Moser, A., Renaot, E.,Marcarino, P., Bongiovanni, G., and Frassineti, G., An intercomparison of galliumfixed point cells Temperature , Its Measurement and Control in Science andIndustry , Edited by J. F. Schooley, Vol. 5, Part 1, pp. 311-316 (AmericanInstitute of Physics, New York, 1982).

(27] Coates . B. and Andrews , J. W., A precise determination of the freezingpoint of copper, J. Phys. F: Metal Phys., a, 277-285 (1978).

[28] Coates, P. B. , The NPL photon-counting pyrometer, Temperature Measurement,1975 , The Institute of Physics Conference Series Number 26, Edited by B. F.Billing and T. J. Quinn, Chapter 5, pp. 238-243 (The Institute of Physics,London, 1975).

of kelvins for the others. The temperatures of calibration for these typesofthermometers usually lie somewhere within the range from about 77 K to 850 KBead-in-glass probe type thermistors used in the moderate temperature range arequite stable and they may be used to approximate the ITS-90 at a level of about± 1 . 5mK to ± 2.0 mK [67] . In their case , a polynomial, the degree of whichdepends on the temperature range of the calibration, is fitted to resistance-temperature data and the results reported in terms of that polynomial. Acalibration on the IPTS-68 (75) may be converted to an approximate ITS-90calibration by the same procedure as outlined for RIRT’s .

4.8 THE LOGO OF THE NATIONAL CONFERENCE OF STANDARDS LABORATORIES FOR THE ITS-90

The National Conference of Standards Laboratories (NCSL) formed an Ad HocCommittee on the Change of the Temperature Scale at the beginning of l988 inorder to publicize the new temperature scale (ITS-90) and to facilitate itsimplementation. At the NCSL meeting in July 1989, the Ad Hoc Committee adopted alogo available from the NCSL [1800 30th Street, Suite 305B , Boulder, CO 80301,Tel. (303) 440-3339 ] , that may be affixed to thermometers that have beencalibrated on the ITS-90. The purpose of the logo, illustrated in figure 26, isto indicate at a glance, without having to refer to documentation, thosethermometers in a laboratory that have been calibrated on the new scale. This isparticularly useful for those laboratories that have their various thermometerscalibrated on a prescribed schedule, with different thermometers being

Figure 26. The NCSL ITS-90 logo.

Z-184

Z

[29] Comptes Rendus des Seances de la Dix-huitieme Conference Generale des Poidset Mesures, Resolution 7, p. 101 (1987).

[30] Comptes Rendus des Seances de la Dixieme Conference Generale des Poids etMesures, Resolution 3, p. 79 (1954).

[31) Compton,J. P., The Realization of Low Temperature Fixed Points,Temperature, Its Measurement And Control in Science and Industry , Edited by H.H. Plumb, Vol. 4, Part 1, pp. 195-209 (Instrument Society of America, Pittsburgh,PA, 1972).

[32] Compton,J. P. and Ward,S. D., Realization of the Boiling and Triple Pointsof Oxygen, Metrologia 12 , 101-113 (1976).

[33] Darling, A. S. and Selman, G. L., Some Effects of Environment on thePerformance of Noble Metal Thermometers, Temperature, Its Measurement andcontrol in Science and Industry , Edited by H. H. Plumb, Vol. 4, Part 3, pp. 1633-1644 (Instrument Society of America, Pittsburgh, PA, 1972).

[34] DeWitt, D. P. and Nutter, G. D., Theory and Practice of RadiationThermometry (John Wiley and Sons, Inc., New York, NY, 1988).

[35] DeWitt, D. P. and Hernicz, R. S., Theory and Measurement of EmittanceProperties for Radiation Thermometry Applications, Temperature, Its Measurementand Control in Science and Industry , Edited by H. H. Plumb, Vol. 4, Part 1, pp.459-482 (Instrument Society of America, Pittsburgh, PA, 1972).

[36] Ditmars, D. A. and G. T. Furukawa, Detection and Damping of Thermal-acoustic Oscillations in Low-temperature Measurements, J. Res. Natl. Bur. Stands.69C, 35-38 (1965).

[37] Durieux, M., and Rusby, R. L., Helium Vapour Pressure Equations on theEPT-76, Metrologia 19 , 67-72, (1983).

[38] Durieux, M., van Dijk, J. E., ter Harmsel, H., Rem, P. C., and Rusby, R.L., Helium Vapor Pressure Equations on the EPT-76, Temperature, Its Measurementand Control In Science and Industry , Edited by J. F. Schooley, Vol. 5, Part 1,pp. 145-154 (American Institute of Physics, New York, 1982).

[39] Elliott, R. P., Constitution of Binary Alloys, First Supplement (McGraw-Hill Book Company, New York, NY, 1965).

[40) Ferguson, J. A., Realization of the Triple Point of Water, J. Phys. E: Sci.Instrum. 3 , 447-451 (1970).

[41] Furukawa, G. T., Reproducibility of the Triple Point of Argon in SealedTransportable Cells, Temperature. Its Measurement and Control in Science andIndustry , Edited by J. F. Schooley, Vol. 5, Part 1, pp. 239-248 (AmericanInstitute of Physics, New York, NY, 1982).

[42] Furukawa, G. T., Bigge, W. R., And Riddle, J. L., Triple Point of Argon,Temperature. Its Measurement and Co control in Science and Industry, Edited by H.H. Plumb, Vol. 4, Part 1, pp. 231-243 (Instrument Society of America, Pittsburgh,PA, 1972).

[43] Furukawa, G. T., Riddle, J. L., Bigge. W. R., and Pfeiffer, E. R.,Application of Some Metal SRM’s as Thermometric Fixed Points, NBS SpecialPublication 260-77, 140 pages, August 1982.

[44) Furukawa, G. T., Piccirelli, J. H., Reilly, M. L., Cryoscopic Determinationof the Purity of Benzene by Calorimetry, Purity Determinations by the ThermalMethods , Edited by R. L. Blaine and C. K. Schoff, pp. 90-106 (American Societyfor Testing and Materials, Philadelphia, PA, 1984).

[45] Furukawa, G. T., Investigation of Freezing Temperatures of National Bureauof Standards Aluminum Standards, J. Res. Natl. Bur. Stand. (U.S.) 78A 477-495(1974).

[46] Furukawa, G. T., Riddle, R. L., and Bigge, W. R., Investigation of freezingtemperatures of National Bureau of Standards tin standards, Temperature, ItsMeasurement and Control in Science and Industry , Edited by H. H. Plumb, Vol. 4,Part 1,pp. 247-263 (Instrument Society of America, Pittsburgh, PA, 1972).

[47] Furukawa, G. T., The Triple Point of Oxygen in Sealed Transportable Cells,J. Res. Natl. Bur. Stands. (U.S.) 91 , 255-275 (1986).

[48] Gordon, C. L. and Wichers, E., Purification of Mercury and Its PhysicalProperties, Ann. New York Acad. Sci. 65 369-387 (1957).

[49] Guildner, L. A. and Edsinger, R. E., Deviation of International PracticalTemperatures from Thermodynamic Temperatures in the Temperature Range from273.16 K to 730 K, J. Res. Bur. Stands. 80A , 703-738 (1976).

[50] Guildner, L. A., Stimson, H. F., Edsinger, R. E., and Anderson, R. L., AnAccurate Mercury Manometer for NBS Gas The Thermometer, Metrologia 6 1-18 (1970).

[51] Hansen,. M. , Constitution of Binary Alloys (McGraw-Hill Book Company, Inc.New York, NY, 1958).

[52] Harrison, E. R., Hatt, D. J. Prowse, D. B., and Wilbur-Ham, J., A NewInterferometric Manometer, Metrologia 12 115-122 (1976).

[53] Jangg, G. and Palman, H., Die Loslichkeit verschiedener Metalle in,Quecksilber, Zeit. Metallkde, 54 , 364-369 (1963).

[54] Jones, T. P. and Tapping, J., A photoelectric pyrometer temperature scalebelow 1064.43 *C and its use to measure the silver point, Temperature, ItsMeasurement and Control in Science and Industry , Edited by J. F. Schooley, Vol.5, Part 1, pp. 169-174 (American Institute of Physics, New York, 1982).

[55] Jones, T. P. and Tapping, J., The Determination of the ThermodynamicTemperatures of Thermometry Fixed Points in the Range 660 ˚C to 1064 ˚C,Metrologia 25 , 41-47 (1988).

[56] Jung, J. J., Determination of the difference between the thermodynamicfixed-point temperatures of gold and silver by radiation thermometry, TemperatureMeasurement. 1975 , The Institute of Physics Conference Series Number 26, Editedby B. F. Billing and T. J. Quinn, Chapter 5, pp. 278-286 (The Institute ofPhysics, London, 1975).

[57] Jung H J A Measurement of Thermodynamic Temperatures Between 683 K and 933 Kby an Infrared Pyrometer, Metrologia 23 , 19-31 (1986).

[58] Kemp,R. C. and Kemp, W. R. G., The Triple Point, Boiling Point and 17 KPoint of Equilibrium Hydrogen, Metrologia 15 , 155-159 (1979).

[59] Kemp,R. C., Kemp, W. R. C., and Cowan, J. A., The Boiling Points andTriple Points of Oxygen and Argon, Metrologia 12 93-100 (1976).

[60] Kemp, R. C., Kemp, W. R. G., and Besley, L. M., A Determination ofThermodynamic Temperatures and Measurements of the Second Virial Coefficient of4He Between 13.81 K and 287 K Using a Constant-Volume Gas Thermometer, Metrologia23, 61-86 (1986/87)

[61] Klein, H. H., Klempt, G., and Storm, L., Measurement of the ThermodynamicTemperature of 4He at Various Vapour Pressures by a Noise Thermometer, Metrologia15, 143-154 (1979).

[62] Lee, R. D., Construction and Operation of a Simple High-Precision Copper-Point Blackbody and Furnace, NBS Technical Note 483, May 1969.

[63] Maghenzani, R., Molinar, G. F., Marzola, L., and Kulshrestha, R. K.,Pressure Metrology up to 5 MPa in Different Gas Media, J. Phys. E: Sci. Instrum.20, 1173-1179 (1987).

[64] Mangum, B. W., Platinum Resistance Thermometer Calibrations, NBS SpecialPublication 250-22 (October 1987).

[65) Mangum, B. W., Triple point of gallium as a temperature fixed point,Temperature, Its Measurement and Control in Science and Industry , Edited by J.F. Schooley, Vol. 5, Part 1, pp. 299-309 (American Institute of Physic, NewYork, 1982).

[66] Mangum, B. W., Special Report on the international Temperature Scale of1990; Report on the l7th Session of the Consultative Committee on Thermometry, J.Res. Natl. Inst. Stand. Technol. 95, 69-77 (1990).

[67] Mangum, B. W., Triple point of succinonitrile and its use in thecalibration of thermistor thermometers, Rev. Sci. Instrum. 54, 1687-1692 (1983).

[68] Mangum B., W. and Thornton, D. D., Determination of the Triple-PointTemperature of Gallium, Meirologia 15 , 201-215 (1979).

[69] Mangum. A. W. Determination of the Indium Freezing-point, and Triple-pointTemperature., Netrologia 26 211-217 (1989).

[70] McAllan, J. V. and Ammar, M. M., Comparison of the freezing points ofaluminum and antimony, Temperature, Its Measurement and Control in Science andIndustry , Edited by H. 14. Plumb Vol. 4, Part 1, pp. 273-285 (Instrument Societyof America, Pittsburgh, PA, 1972).

[71] McConvil le, G. T., The Effect of the Measuring Tube Surface onThermomolecular Pressure Corrections in Vapor Pressure Thermometry, Temperature,Its Measurement and Control in Science and Industry , Edited by H. H. Plumb, Vol.4, Part 1, pp. 159-165 (Instrument Society of America, Pittsburgh, PA, 1972).

[72] McLachlan, A. D., Uchiyama, H., Saino, T., and Nakaya, S., The Stabilityof the Freezing Point of Copper as a Temperature Standard, Temperature , ItsMeasurement and Control in Science and Industry , Edited by H. H. Plumb, Vol. 4,Part 1, pp. 287-293 (Instrument Society of America, Pittsburgh, PA, 1972).

[73] McLaren, E. H., The Freezing Points of High Purity Metals as PrecisionTemperature Standards. II. An I Investigation of the Freezing Temperatures ofZinc, Cadmium, and Tin, Can. J. Phys. 35, 1086-1106 (1957).

[74] McLaren, E. H., The Freezing Points of High Purity Metals as PrecisionTemperature Standards. IV. Indium: Thermal Analyses on Three Grades ofCadmium, Can. J. Phys. 36 , 1131-1147 (1958).

[75] McLaren, E. H., The Freezing Points of High Purity Metals as PrecisionTemperature Standards. III. Thermal Analysis on Eight Grades of Zinc withPurities Greater than 99.99+%, Can. J. Phys. 36 , 585-598 (1958).

[76] McLaren, E. H. and Murdock, E. G., The Freezing Points of High PurityMetals as Precision Temperature Standards. V. Thermal Analyses on 10 Samplesof Tin with Purities Greater than 99.99+%, Can. J. Phys. 38 , 100-118 (1960).

[77] Ohtsuka, M. and Bedford, It. E., Measurement of the thermodynamictemperature interval between the freezing points of silver and copper,Temperature , Its Measurement and Control in Science and Industry , Edited by J.F. Schooley, Vol. 5, Part 1, pp. 175-181 (American Institute of Physics, NewYork, 1982).

[78] Orlova, M. P., Astrov, D. N., Shareskaya, D. I., Belyanskii, L. B.,Razhba, Ya. E., and Khnykov, V. M., Primary State Standard for the Unit ofTemperature, in the Range of 13.81-273.15 K, Measurement Techniques 16 477-482(1973).

[79] Pavese, F., Ancsin, J., Astrov, D. N., Bonhoure, J., Bonnier, G., Furukawa,G. T. , Kemp, R. C. , Maas, H. , Rusby, R. L. , Sakurai, H. , and Ling Shan-Kang,An International Intercomparison of Fixed Points by Means of Sealed Cells in theRanae 13.81 K - 90.686 K, Metrologia 20 , 127-144 (1984).

Z-185


[80] Pavese.F., The Triple Points of Argon and Oxygen, Metrologia 14 , 93-103,(1978).

[81] Peggs, G., N., Elliott, K. W. T., and Lewis, S., An Intercomparison Betweena Primary Standard Mercury Barometer and a Gas-operated Pressure BalanceStandard, Metrologia 15 , 77-85 (1979).

[82] Powell, R. L., Hall, W. J., Hyink, H. Jr., Sparks, L. L., Burn., G. W.,Scroger M. G., and Plumb, H. H., Thermocouple Reference Tables Based on theIPTS-68, NBS Monograph 125 (March 1974).

[83] Preston-Thomas, H., The International Temperature Scale of 1990 (ITS-90),Metrologia 27, 3-10 (1990).

[84] Proces-Verbaux des Seances du Comite International des Poid. et Mesures,(78 • session, octobre 1989), in press.

[85] Quinn, T. J., News from the BIPM, Metrologia 26, 69-74 (1989).

[86] Quinn, T. J. and Chandler, T. R. D., The Freezing Point of PlatinumDetermined by the NPL Photoelectric Pyrometer, Temperature, Its Measurement andControl in Science and Industry . Edited by H. H . Plumb, Vol. 4, Part 1, pp.295- 309 (Instrument Society of America, Pittsburgh, PA, 1972).

1871 Quinn, T. J., Temperature (Academic Press, Inc., New York, N. Y. (1983).

[88] Ricci, J. E., The Phase Rule and Heterogeneous Equilibrium, (DoverPublications, Inc., New York, NY, 1966).

[89] Righini, F., Rosso, A., and Ruffino, G., Temperature Dependence ofEffective Wavelength in Optical Pyrometry, Temperature. Its, Measurement andControl in Science and Industry , Edited by H. H. Plumb, Vol. 4, Part 1, pp. 413-421 (Instrument Society of America, Pittsburgh, PA, 1972).

[90] Roberts, T. R., Sherman, R. H., and Sydoriak, S. G., The 1962 The Scale ofTemperatures III. Evaluation and Status, J. Res. Natl. Bur. Stands. 68A, 567-578(1964).

[91] Rusby, R. L. and Swenson, C. A., A New Determination of the Helium VapourPressure Scales Using a CMN Magnetic Thermometer and the NPL-75 Gas ThermometerScale, Metrologia-16, 73-87 (1980).

[92] Sawada, S., Realization of the triple point of Indium in a sealed glasscell, Temperature Its Measurement and Control in Science and Industry , Edited byJ. F. Schooley, Vol. 5, Part 1, pp. 343-346 (American Institute of Physics, NewYork 1982).

[93] . Simon,M ., On the Phase Separation in the Liquid System Ne-pH 2, Phys.Letters, 5, 319 (1963).

[94] Sostman, H. E., Melting point of gallium as a temperature calibrationstandard, Rev. Sci. Instrum . 41, 127-130 (1977).

[95] Sparrow, E. M., Albers, L. U., and Eckert, E. R. G., Thermal RadiationCharacteristics of Cylindrical Enclosures, J. Heat Transfer 04, 73-81 (1962).

[96] Steur, P. P. M. and Durieux, M., Constant-Volume Gas Thermometry Between 4 Kand 100 K, Metrologia 21, 1-18 (1986).

[97] Streett, W. B. and D. H. Jones, Liquid Phase Separation and Liquid-vaporEquilibrium in the System Neon-Hydrogen, J. Chem. Phys. 42, 3989-3994 (1965).

[98] Takiya, M., Precise Measurement of the Freezing Point of Silver with aPlatinum Resistance Thermometer, Comitee Consultatif de Thermometrie. 12thSession, Annexe T30, T154-T159 (1978).

[99] The 1976 Provisional 0.5.K to 30 K Temperature Scale, Metrologia 15, 65-68(1979).

[100] The International Practical Temperature Scale of 1968, Metrologia 5,35-44 (1969).

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[102] Weber,S. and Schmidt,G., Experimentel le Untersuchungen Ober dieThermomolekulare Druckdifferenz in der Nahe der Grenzbedingung P l /P 2 = (T 1/T 2) 1/2

und Vergleichung nit der Theorie, Leiden Communication 246C, 1-13 (1936).

[103] Weeks. J. R., Liquidus Curves and Corrosion of Fe, Cr , Ni, Co, V, Cb, Ta,Ti, Zr, in 500-750 ˚C Mercury, Corrosion 23, 98-106 (1967).

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Reproduced with permission of National Institute of Standards and Technology

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Z

The International Temperature Scale of 1990The International Temperature Scale of 1990 wasadopted by the International Committee of Weights andMeasures at its meeting in 1989, in accordance with therequest embodied in Resolution 7 of the 18th GeneralConference of Weights and Measures of 1987. Thisscale supersedes the International Practical TemperatureScale of 1968 (amended edition of 1975) and the 1976Provisional 0.5 K to 30 K Temperature Scale.

1. Units of TemperatureThe unit of the fundamental physical quantity known asthermodynamic temperature, symbol T, is th kelvinsymbol K, defined as the fraction 1/273.16 of thethermodynamic temperature of the triple point of water 1.Because of the way earlier temperature scales weredefined, it remains common practice to express atemperature in terms of its difference from 273.15 K,the ice point. A thermodynamic temperature, T,expressed in this way is known as a Celsiustemperature, symbol t, defined by:t / °C=T/K —273.15 . (1)The unit of Celsius temperature is the degree Celsius,symbol °C, which is by definition equal in magnitude tothe kelvin. A difference of temperature may beexpressed in kelvins or degrees Celsius.The International Temperature Scale of 1990 (ITS-90)defines both International Kelvin Temperatures, symbolT90, and International Celsius Temperatures, symbolt 90. The relation between T90 and t 90 is the same asthat between T and t, i.e.:t90/°C = T90/K —273.15 . (2)The unit of the physical quantity T90 is the kelvin,symbol K, and the unit of the physical quantity t90 is thedegree Celsius, symbol °C, as is the case for thethermodynamic temperature T and the Celsiustemperature t.

2. Principles of the InternationalTemperature Scale of 1990 (ITS-90)The ITS-90 extends upwards from 0.65 K to thehighest temperature practicably measurable in terms of the Planck radiation law using monochromaticradiation. The ITS-90 comprises a number of rangesand sub-ranges throughout each of whichtemperatures T90 are defined. Several of these rangesor sub-ranges overlap, and where such overlappingoccurs, differing definitions of T90 exist: these differingdefinitions have equal status. For measurements of thevery highest precision there may be detectablenumerical differences between measurements made atthe same temperature but in accordance with differingdefinitions. Similarly, even using one definition, at atemperature between defining fixed points twoacceptable interpolating instruments (e.g. resistancethermometers) may give detectably differing numericalvalues of T90. In virtually all cases these differencesare of negligible practical importance and are at theminimum level consistent with a scale of no more thanreasonable complexity; for further information on thispoint see “Supplementary information for the ITS-90”(BIPM-1990).The ITS-90 has been constructed in such a way that,throughout its range, for any given temperature thenumerical value of T90 is a close approximation to thenumerical value of T according to best estimates at thetime the scale was adopted. By comparison with directmeasurements of thermodynamic temperatures,measurements of T90 are more easily made, are moreprecise and are highly reproducible.There are significant numerical differences betweenthe values of T90 and the corresponding values of T90measured on the International Practical TemperatureScale of 1968 (IPTS-68), see Fig. 1 and Table 6.Similarly there were differences between the IPTS-68and the International Practical Temperature Scale of1948 (IPTS-48), and between the InternationalTemperature Scale of 1948 (ITS-48) and theInternational Temperature Scale of 1927 (ITS-27). See the Appendix, and, for more detailed information,“Supplementary Information for the ITS-90”.

The International Temperature Scale of 1990

1 Comptes Rendux des Séances de la Treizième ConférenceGénérale des Poids et Mesures (1967-1968). Resolutions 3 and 4, p. 104

Reprinted with permission of Bureau International des Poids et Mesures.

H. Preston-ThomasPresident of the Comité Consultatif de Thermométrie and Vice-President of the ComitéInternational des Poids et Mesures Division of Physics,National Research Council of Canada, Ottawa, K1AOS1 CanadaReceived: October 24, 1989

Introductory NoteThe official French text of the ITS-90 is published bythe BIPM as part of the Prochès-verbaux of the ComitéInternational des Poids et Mesures (CIPM). However,the English version of the text reproduced here hasbeen authorized by the Comité Consultatif deThermométrie (CCT) and approved by the CIPM.

metrologia ©Springer-Verlag 1990 This copy incorporates textual corrections detailed in Metrologia 27, 107 (1990)

The International Temperature Scale of 1990 (ITS-90)

Z- 187

3. Definition of the InternationalTemperature Scale of 1990Between 0.65 K and 5.0 K T90 is defined in terms of thevapour-pressure temperature relations 3He and 4He.Between 3.0 K and the triple point of neon (24.5561 K)T90 is defined by means of a helium gas thermometercalibrated at three experimentally realizable temperatureshaving assigned numerical values (defining fixed points)and using specified interpolation procedures.Between the triple point of equilibrium hydrogen(13.8033 K) and the freezing point of silver (961.78 °C)T90 is defined by means of platinum resistancethermometers calibrated at specified sets of definingfixed points and using specified interpolationprocedures.Above the freezing point of silver (961.78°C) T90 isdefined in terms of a defining fixed point and thePlanck radiation law.The defining fixed points of the ITS-90 are listed inTable 1. The effects of pressure, arising fromsignificant depths of immersion of the sensor or fromother causes, on the temperature of most of thesepoints are given in Table 2.

3.1. From 0.65 K: Helium Vapour-PressureTemperature EquationsIn this range T90 is defined in terms of the vapourpressure p of 3He and 4He using equations of the form:

9

T90/K = A0 + ∑ Ai [(ln (p /Pa) — B)/C)i . (3)i = 1

The values of the constants A0, Ai, B and C are givenin Table 3 for 3He in the range of 0.65 K to 3.2 K, andfor 4He in the ranges 1.25 K to 2.1768 K (the l point)and 2.1768 K to 5.0 K.3.2 From 3.0 K to the Triple Point of Neon (24.5561 K):Gas ThermometerIn this range T90 is defined in terms of a 3He or a 4Hegas thermometer of the constant-volume type that hasbeen calibrated at three temperatures. These are thetriple point of neon (24.5561 K), the triple point ofequilibrium hydrogen (13.8033 K), and a temperatureis between 3.0 K and 5.0 K. This last temperature isdetermined using a 3He or a 4He vapour pressurethermometer as specified in Sect. 3.1.

The International Temperature Scale of 1990 Cont’d

0.4

Tem

per

atu

re d

iffe

ren

ce (

t 90-

t 68)

/°C

t90/°C

-200

-0.2

0

-0.04

-0.02

0

0.02

0

0

-0.01

-0.02

100

200 400

-200 0 200 400

600 800 1000

0.2

0

-0.2

FIG. 1. The differences ( t 90 — t 68) as a function of Celsius temperatue t 90

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Z

Table 1. Defining fixed points of the ITS-90

Number Temperature Sub- Stateb Wr(T90)—————————— stancea

T90/K t90/°C

1 3 to 5 — 270.15 to He V— 268.15

2 13.8033 — 259.3467 e-H2 T 0.0001 190 073 ≈ 17 ≈ — 256.15 e-H2 V

(or He) (or G)4 ≈ 20.3 ≈ — 252.85 e-H2 V

(or He) (or G)5 24.5561 — 248.5939 Ne T 0.008 449 746 54.3584 — 218.7916 O2 T 0.091 718 047 83.8058 — 189.3442 Ar T 0.215 859 758 234.3156 — 38.8344 Hg T 0.844 142 11

9 273.16 0.01 H2O T 1.000 000 0010 302.9146 29.7646 Ga M 1.118 138 8911 429.7485 156.5985 In F 1.609 801 8512 505.078 231.928 Sn F 1.892 797 68

13 692.677 419.527 Zn F 2.568 917 3014 933.473 660.323 Al F 3.376 008 6015 1234.93 961.78 Ag F 4.286 420 5316 1337.33 1064.18 Au F17 1357.77 1084.62 Cu F

a All substances except 3He are of natural isotopic composition. e-H2is hydrogen at the equilibrium concentration of the ortho- and para-molecular formsb For complete definitions and advice on the realization of thesevarious states, see “Supplementary Information for the ITS-90”. Thesymbols have the following meanings: V: vapour pressure point; T:triple point (temperature at which the solid liquid and vapour phases arein equilibrium); G: gas thermometer point; M, F: melting point, freezingpoint (temperature, at a pressure of 101 325 Pa, at which the solid andliquid phases are in equilibrium)

Table 2. Effect of pressure on the temperatures of some defining fixed points ‡

Substance Assignment Temperature Variationvalue of with pressure, p with depth, lequilibrium (dT/dp)/ (dT/dl)/temperature (10-8 K · Pa -1)* (10-3K · m-1)**T90/K

e-Hydrogen (T) 13.8033 34 0.25Neon (T) 24.5561 16 1.9Oxygen (T) 54.3584 12 1.5Argon (T) 83.8058 25 3.3

Mercury (T) 234.3156 5.4 7.1Water (T) 273.16 — 7.5 — 0.73Gallium 302.9146 — 2.0 — 1.2Indium 429.7485 4.9 3.3

Tin 505.078 3.3 2.2Zinc 692.677 4.3 2.7Aluminium 933.473 7.0 1.6Silver 1234.93 6.0 5.4

Gold 1337.33 6.1 10Copper 1357.77 3.3 2.6

* Equivalent to millikelvins per standard atmosphere** Equivalent to millikelvins per metre of liquid

‡ The Reference pressure for melting and freezing points is thestandard atmosphere (p0=101 325 Pa). For triple points (T) thepressure effect is a consequence only of the hydrostatic head of liquidin the cell

Table 3. Values of the constants for the helium vapourpressure Eqs. (3), and the temperature range for whicheach equation, identified by its set of constants, is valid

3He 4He 4He0,65 K to 3,2 K 1,25 K to 2,1768 K 2,1768 K to 5,0 K

A0 1.053 447 1.392 408 3.146 631A1 0.980 106 0.527 153 1.357 655A2 0.676 380 0.166 756 0.413 923A3 0.372 692 0.050 988 0.091 159A4 0.151 656 0.026 514 0.016 349A5 — 0.002 263 0.001 975 0.001 826

A6 0.006 596 — 0.017 976 — 0.00 4325A7 0.088 966 0.005 409 — 0.00 4973A8 — 0.004 770 0.013 259 0

A9 — 0.054 943 0 0B 7.3 5.6 10.3C 4.3 2.9 1.9

3.2.1. From 4.2 K to the Triple Point of Neon (24.5561K) with 4He as the Thermometric Gas. In this range T90is defined by the relation:T90 = a + bp + cp2 , (4)where p is the pressure in the gas thermometer and a, band c are coefficients the numerical values of which areobtained from measurements made at the three definingfixed points given in Sect. 3.2. but with the furtherrestriction that the lowest one of these points liesbetween 4.2 K and 5.0 K.3.2.2. From 3.0 K to the Triple Point of Neon (24.5561 K) with 3He or 4He as the Thermometric Gas.For a 3He gas thermometer, and for a 4He gasthermometer used below 4.2 K, the non-ideality of thegas must be accounted for explicitly, using theappropriate second virial coefficient B3 (T90) or B4 (T90).In this range T90 is defined by the relation:

a + bp + cp2

T90 = ————————— , (5)1 + BX (T90) N/V

where p is the pressure in the gas thermometer, a, band c are coefficients the numerical values of whichare obtained from measurements at three definingtemperatures as given in Sect. 3.2, N/V is the gasdensity with N being the quantity of gas and V thevolume of the bulb, X is 3 or 4 according to the isotopeused, and the values of the second virial coefficientsare given by the relations:For 3He,B (T90)/m

3 mol — 1 = 16.69 — 336.98 (T90/K) — 1 (6a)+ 91.04 (T90/K) — 2 — 13.82 (T90/K) — 3 10 — 6 .

For 4He,B4 (T90)/m

3 mol-1 = 16.708 — 374.05 (T90/K) — 1 (6b)— 383.53 (T90/K) — 2 + 1799.2 (T90/K) — 3

— 4033.2 (T90/K) — 4 + 3252.8 (T90/K) — 3 10 — 6 .

Z- 189

Table 4. The constants A0, A i; B o, B i; C0, C i; D0 andD i in the reference functions of equations (9a); (9b);(10a); and (10b), respectively

A0 — 2.135 347 29 B0 0.183 324 722 B13 — 0.091 173 542A1 3.183 247 20 B1 0.240 975 303 B14 0.001 317 696A2 — 1.801 435 97 B2 0.209 108 771 B15 0.026 025 526A3 0.717 272 04 B3 0.190 439 972

A4 0.503 440 27 B4 0.142 648 498A5 — 0.618 993 95 B5 0.077 993 465A6 — 0.053 323 22 B6 0.012 475 611A7 0.280 213 62 B7 — 0.032 267 127

A8 0.107 152 24 B8 — 0.075 291 522A9 — 0.293 028 65 B9 — 0.056 470 670A10 0.044 598 72 B10 0.076 201 285A11 0.118 686 32 B11 — 0.123 893 204A12 — 0.052 481 34 B12 — 0.029 201 193

C0 2.781 572 54 D0 439.932 854C1 1.646 509 16 D1 472.418 020C2 — 0.137 143 90 D2 37.684 494C3 — 0.006 497 67 D3 7.472 018

C4 — 0.002 344 44 D4 2.920 828C5 0.005 118 68 D5 0.005 184C6 0.001 879 82 D6 — 0.963 864C7 — 0.002 044 72 D7 — 0.188 732

C8 — 0.000 461 22 D8 0.191 203C9 0.000 457 24 D9 0.049 025

The accuracy with which T90 can be realized usingEqs. (4) and (5) depends on the design of the gasthermometer and the gas density used. Design criteriaand current good practice required to achieve aselected accuracy are given in “SupplementaryInformation for the ITS-90”.3.3. The Triple Point of Equilibrium Hydrogen (13.8033 K) to the Freezing Point of Silver (961.78 °C):Platinum Resistance ThermometerIn this range T90 is defined by means of a platinumresistance thermometer calibrated at specified sets of defining fixed points, and using specified referenceand deviation functions for interpolation at interveningtemperatures.No single platinum resistance thermometer can providehigh accuracy, or is even likely to be usable, over all ofthe temperature range 13.8033 K to 961.78 °C. Thechoice of temperature range, or ranges, from amongthose listed below for which a particular thermometercan be used is normally limited by its construction.For practical details and current good practice, inparticular concerning types of thermometer available,their acceptable operating ranges, probableaccuracies, permissible leakage resistance, resistancevalues, and thermal treatment, see “SupplementaryInformation for ITS-90”. It is particularly important totake account of the appropriate heat treatments thatshould be followed each time a platinum resistancethermometer is subjected to a temperature aboveabout 420°C.

Temperatures are determined in terms of the ratio ofthe resistance R (T90) at a temperature T90 and theresistance R (273.16 K) at the triple point of water. This ratio, W (T90), is 2:W (T90) = R (T90)/R (273.16 K) . (7)An acceptable platinum resistance thermometer mustbe made from pure, strain-free platinum, and it mustsatisfy at least one of the following two relations:W (29.7646 °C) ≥ 1.118 07 , (8a)W (— 38.8344 °C) ≥ 0.844 235 . (8b)An acceptable platinum resistance thermometer that isto be used up to the freezing point of silver must alsosatisfy the relation:W (961.78 °C) ≥ 4.2844 . (8c)In each of the resistance thermometer ranges, T90is obtained from W (T90) as given by the appropriatereference function Eqs. (9b) or (10b), and thedeviation W (T90) — Wr (T90). At the defining fixedpoints this deviation is obtained directly from thecalibration of the thermometer: at intermediatetemperatures it is obtained by means of theappropriate deviation function Eqs. (12), (13) and (14).(i) — For the range 13.8033 K to 273.16 K thefollowing reference function is defined:

12 In (T90)/273.16 K) + 1,5 i

In [Wr (T90)] = A0 + ∑ A i[ —————————— ] .(9a)i = 1 1,5

An inverse function, equivalent to Eq. (9a) to within 0,1mK, is:

15 Wr (T90)1/6 — 0.65 i

T90/273.16 K = B0 + ∑ B i[ ———————— ] .(9b)i = 1 0.35

The values of the constants A0, A i, B0 and B i are givenin Table 4.A thermometer may be calibrated for use throughoutthis range or, using progressively fewer calibrationpoints, for ranges with low temperature limits of24.5561 K, 54.3584 K and 83.8058 K, all having anupper limit of 273.16 K.(ii) — For the range 0 °C to 961.78 °C the followingreference function is defined:

9 T90/K — 754.15 i

Wr (T90) = C0 + ∑ Ci[ ——————— ] . (10a)i = 1 481

An inverse function, equivalent to equation (10a) towithin 0,13 mK is:

9 Wr (T90) — 2.64 i

T90/K — 273.15 = D0 + ∑ Di[ ——————— ] .(10b)i = 1 1.64

The values of the constants C0, C i, D0 and D i aregiven in Table 4.—————2 Note that this definition of W (T90) differs from the correspondingdefinition used in the ITS-27, ITS-48, IPTS-48, and IPTS-68: for all ofthese earlier scales W (T) was defined in terms of reference temperatureof 0°C, which since 1954 has itself been defined as 273.15 K


Z- 190

Z

A thermometer may be calibrated for use throughoutthis range or, using fewer calibration points, for rangeswith upper limits of 660.323 °C, 419.527 °C, 231.928°C, 156.5985 °C or 29.7646 °C, all having a lower limitof 0°C.(iii) — A thermometer may be calibrated for use in therange 234.3156 K ( — 38.8344 °C) to 29.7646 °C, thecalibration being made at these temperatures and atthe triple point of water. Both reference functions Eqs.(9) and (10) are required to cover this range.The defining fixed points and deviation functions for thevarious ranges are given below, and in summary fromin Table 5.3.3.1. The Triple Point of Equilibrium Hydrogen(13.8033 K) to the Triple Point of Water (273.16 K).The thermometer is calibrated at the triple points ofequilibrium hydrogen (13.8033 K), neon (24.5561 K),oxygen (54.3584 K), argon (83.8058 K), mercury(234.3156 K), and water (273.16 K), and at twoadditional temperatures close to 17.0 K and 20.3 K.These last two may be determined either: by using agas thermometer as described in Sect. 3.2, in whichcase the two temperatures must lie within the ranges16.9 K to 17.1 K and 20.2 K to 20.4 K respectively; orby using the vapour pressure-temperature relation ofequilibrium hydrogen, in which case the towtemperatures must lie within the ranges 17.025 K to17.045 K and 20.26 K to 20.28 K respectively, with theprecise values being determined from Eqs. (11a) and(11b) respectively:T90/K — 17.035 = (p/kPa — 33.3213)/13.32 (11a)T90/K — 20.27 = (p/kPa — 101.292)/30 . (11b)The deviation function is 3:W (T90) — Wr (T90) = a [W (T90)—1] + b [W (T90)—1]2

5

+ ∑ c i [ln W (T90)]i + n (12)

i = 1

with values for the coefficients a, b and ci beingobtained from measurements at the defining fixedpoints and with n = 2.For this range and for the sub-ranges 3.3.1.1 to 3.3.1.3the required values Wr (T90) are obtained from Eq. (9a)or from Table 1.3.3.1.1. The Triple Point of Neon (24.5561 K) to theTriple Point of Water (273.16 K). The thermometer iscalibrated at the triple points of equilibrium hydrogen(13.8033 K), neon (24.5561 K), oxygen (54.3584 K),argon (83.8058 K), mercury (234.3156 K) and water(273.16 K).The deviation function is given by Eq. (12) with valuesfor the coefficients a, b, c1, c2 and c3 being obtainedfrom measurements at the defining fixed points andwith c4 = c5 = n = 0.3.3.1.2 The Triple Point of Oxygen (54.3584 K) to theTriple Point of Water (273.16 K). The thermometer is

3 This deviation function and also those of Eqs. (13) and (14) may be expressed in terms of Wr rather than W; for this procedure see“Supplementary Information for ITS-90”

Table 5. Deviation functions and calibration points forplatinum resistance thermometers in the variousranges in which they define T90

a Ranges with an upper limit of 273,16 K

Sec- Lower Deviation functions Calibrationtion temper- points (see

ature limit Table 1)T/K

3.3.1 13.8033 a[W (T90) — 1]+b[W (T90) — 1]2 2-95

+ ∑ ci [ln W (T90)] i + n, n = 2i = 1

3.3.1.1 24.5561 As for 3.3.1 with c4 = c5 = n = 0 2, 5-93.3.1.2 54.3584 As for 3.3.1 with 6-9

c2 = c3 =c4 = c5 = 0, n = 1

3.3.1.3 83.8058 a[W (T90) — 1] 7-9+b[W (T90) — 1] ln W (T90)

b Ranges with a lower limit of 0°C

Sec- Upper Deviation functions Calibrationtion temper- points (see

ature limit Table 1)t/°C

3.3.2* 961.78 a[W (T90) — 1]+b[W (T90) — 1]2 9, 12-15+ c [W (T90) — 1]3, + d [W (T90)— W (660.323 °C)]2

3.3.2.1 660.323 As for 3.3.2 with d = 0 9, 12 - 143.3.2.2 419.527 As for 3.3.2 with c = d = 0 9, 12, 133.3.2.3 231.928 As for 3.3.2 with c = d = 0 9, 11, 123.3.2.4 156.5982 As for 3.3.2 with b = c = d = 0 9, 113.3.2.5 29.7646 As for 3.3.2 with b = c = d = 0 9, 10

c Range from 234.3156 K ( — 38.8344 °C) to 29.7646°C

3.3.3 As for 3.3.2 with c = d = 0 8-10

* Calibration points 9, 12-14 are used with d = 0 for t90 ≤ 660.323 °C;the values of a, b and c thus obtained are retained for t90 > 660.323 °Cwith d being determined from calibration point 15

calibrated at the triple points of oxygen (54.3584 K),argon (83.8058 K), mercury (234.3156 K) and water(273.16 K).The deviation function is given by Eq. (12) with valuesfor the coefficients a, b and c1 being obtained frommeasurements at the defining fixed points, with c2 = c3= c4 = c5 = 0 and with n = 1.3.3.1.3. The Triple Point of Argon (83.8058 K) to theTriple Point of Water (273.16 K). The thermometer iscalibrated at the triple points of argon (83.8058 K),mercury (234.3156 K) and water (273.16 K).The deviation function is:W (T90) — Wr (T90) = a [W (T90)—1]

+ b [W (T90)—1] In W (T90) (13)with the values of a and b being obtained frommeasurements at the defining fixed points.3.3.2. From 0 °C to the Freezing Point of Silver(961.78 °C). The thermometer is calibrated at the triple

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point of water (0.01 °C), and at the freezing points of t in (231.928 °C), zinc (419.527 °C), aluminium(660.323 °C) and silver (961.78 °C).The deviation function is:W (T90) — Wr (T90) = a [W (T90)—1] + b [W (T90)—1]2(14)

+ c [W (T90)—1]3 + d [W (T90)—W (660.323 °C)]2 .For temperatures below the freezing point of aluminiumd = 0, with the values of a, b and c being determinedfrom the measured deviations from Wr (T90) at thefreezing points of tin, zinc and aluminium. From thefreezing point of aluminium to the freezing point ofsilver the above values of a, b and c are retained andthe value of d is determined from the measureddeviation from Wr (T90) at the freezing point of silver.For this range and for the sub-ranges 3.3.2.1 to 3.3.2.5the required values for Wr (T90) are obtained from Eq.(10a) or from Table 1.3.3.2.1. From 0 °C to the Freezing Point of Aluminium(660.323 °C). The thermometer is calibrated at thetriple point of water (0.01 °C), and at the freezingpoints of tin (231.928 °C), zinc (419.527 °C) andaluminium (660.323 °C).The deviation function is given by Eq. (14), with the valuesof a, b and c being determined from measurements at thedefining fixed points and with d = 0.3.3.2.2. From 0 °C to the Freezing Point of Zinc(419.527 °C). The thermometer is calibrated at thetriple point of water (0.0 °C), and at the freezing pointsof tin (231.928 °C) and zinc (419.527 °C).The deviation function is given by Eq. (14), with thevalues of a and b being obtained from measurementsat the defining fixed points and with c = d = 0.3.3.2.3. From 0 °C to the Freezing Point of Tin(231.928 °C). The thermometer is calibrated at thetriple point of water (0.01 °C), and at the freezingpoints of indium (156.5985 °C) and tin (231.928 °C).The deviation function is given by Eq. (14), with thevalues of a and b being obtained from measurementsat the defining fixed points and with c = d = 0.3.3.2.4.From 0 °C to the Freezing Point of Indium(156.5985 °C). The thermometer is calibrated at thetriple point of water (0.01 °C), and at the freezing pointof indium (156.5985 °C).The deviation function is given by Eq. (14) with thevalue of a being obtained from measurements at thedefining fixed points and with b = c = d = 0.3.3.2.5. From 0 °C to the Melting Point of Gallium(29.7646 °C). The thermometer is calibrated at thetriple point of water (0.01 °C), and the melting point ofgallium (29.7646 °C).The deviation function is given by Eq. (14) with thevalue of a being obtained from measurements at thedefining fixed points and with b = c = d = 0.

3.3.3. The Triple Point of Mercury (—38.8344 °C) tothe Melting Point of Gallium (29.7646 °C). Thethermometer is calibrated at the triple points of mercury(— 38.8344 °C), and water (0.01 °C), and at themelting point of gallium (29.7646 °C).The deviation function is given by Eq. (14) with thevalues of a and b being obtained from measurementsat the defining fixed points and with c = d = 0.The required values of Wr (T90) are obtained from Eqs.(9a) and (10a) for measurements below and above273.16 K respectively, or from Table 1.

3.4. The Range Above the Freezing Point of Silver(961.78 °C): Planck Radiation LawAbove the freezing point of silver the temperature T90is defined by the equation:

Ll(T90) exp (c2[lT90(X)]—1)—1—————— = ——————————— . (15)

Ll [(T90(X)] exp (c2[lT90]—1)—1where T90(X) refers to any one of the silver T90(Ag) =1234.93 K, the gold T90(Au) = 1337.33 K or thecopper T90(Cu) = 1357.77 K freezing points4 and inwhich Ll(T90) and Ll[T90(X)] are the spectralconcentrations of the radiance of a blackbody at thewavelength (in vacuo) l at T90 and at T90(X)respectively, and c2 = 0.014388 m · K.For practical details and current good practice foroptical pyrometry, see “Supplementary Information forthe ITS-90” (BIPM-1990).

4. Supplementary Information and Differences from Earlier ScalesThe apparatus, methods and procedures that will serveto realize the ITS-90 are given in “SupplementaryInformation for the ITS-90”. This document also givesan account of the earlier International TemperatureScales and the numerical differences betweensuccessive scales that include, where practicable,mathematical functions for differences T90 — T68. Anumber of useful approximations to the ITS-90 aregiven in “Techniques for Approximating the ITS-90”.These two documents have been prepared by theComité Consultatif de Thermométrie and are published by the BIPM; they are revised and updated periodically.The differences T90 — T68 are shown in Fig. 1 andTable 6. The number of significant figures given inTable 6 allows smooth interpolations to be made.However, the reproducibility of the IPTS-68 is, in many areas, substantially worse than is implied by this number.

4 The T90 values of the freezing points of silver, gold and copper arebelieved to be self consistent to such a degree that the substitution ofany one of them in place of one of the other two as the referencetemperature T90 (X) will not result in significant differences in themeasured values of T90.


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Appendix


The International Temperature Scale of 1927 was adopted bythe seventh General Conference of Weights and Measures toovercome the practical difficulties of the direct realization ofthermodynamic temperatures by gas thermometry, and as auniversally acceptable replacement for the differing existingnational temperature scales. The ITS-27 was formulated so asto allow measurements of temperature to be made preciselyand reproducibly, with as close an approximation tothermodynamic temperatures as could be determined at thattime. Between the oxygen boiling point and the gold freezingpoint it was based upon a number of reproducible

temperatures, or fixed points, to which numerical values wereassigned, and two standard interpolating instruments. Each ofthese interpolating instruments was calibrated at several of thefixed points, this giving the constants for the interpolatingformula in the appropriate temperature range. A platinumresistance thermometer was used for the low part and aplatinum rhodium/platinum thermocouple for temperaturesabove 660 °C. For the region above the gold freezing point,temperatures were defined in terms of the Wien radiation law:in practice, this invariably resulted in the selection of an opticalpyrometer as the realizing instrument.


The International Temperature Scale of 1948 was adopted by

Table 6. Differences between ITS-90 and EPT-76, and between ITS-90 and IPTS-68 for specified values of T90and t 90

(T90 — T76)/mKT90/K 0 1 2 3 4 5 6 7 8 9

0 — 0.1 —0.2 — 0.3 — 0.4 — 0.510 — 0.6 — 0.7 — 0.8 — 1.0 —1.1 —1.3 — 1.4 — 1.6 — 1.8 — 2.020 — 2.2 — 2.5 — 2.7 — 3.0 — 3.2 — 3.5 — 3.8 — 4.1

(T90 — T68)/KT90/K 0 1 2 3 4 5 6 7 8 9

10 — 0.006 — 0.003 —0.004 — 0.006 — 0.008 — 0.00920 — 0.009 — 0.008 —0.007 — 0.007 — 0.006 — 0.005 —0.004 — 0.004 — 0.005 — 0.00630 — 0.006 — 0.007 —0.008 — 0.008 — 0.008 — 0.007 —0.007 — 0.007 — 0.006 — 0.00640 — 0.006 — 0.006 —0.006 — 0.006 — 0.006 — 0.007 —0.007 — 0.007 — 0.006 — 0.00650 — 0.006 — 0.005 —0.004 — 0.004 — 0.003 — 0.002 —0.001 0.000 0.001 0.00260 0.003 0.003 0.004 0.004 0.005 0.005 0.006 0.006 0.007 0.00770 0.007 0.007 0.007 0.007 0.007 0.008 0.008 0.008 0.008 0.00880 0.008 0.008 0.008 0.008 0.008 0.008 0.008 0.008 0.008 0.00890 0.008 0.008 0.008 0.008 0.008 0.008 0.008 0.009 0.009 0.009

T90/K 0 10 20 30 40 50 60 70 80 90100 0.009 0.011 0.013 0.014 0.014 0.014 0.014 0.013 0.012 0.012200 0.011 0.010 0.009 0.008 0.007 0.005 0.003 0.001

(t90 — t68)/°Ct90/°C 0 — 10 — 20 — 30 — 40 — 50 — 60 — 70 — 80 — 90— 100 0.013 0.013 0.014 0.014 0.014 0.013 0.012 0.010 0.008 0.008

0 0.000 0.002 0.004 0.006 0.008 0.009 0.010 0.011 0.012 0.012t90/°C 0 10 20 30 40 50 60 70 80 90

0 0.000 — 0.002 — 0.005 — 0.007 — 0.010 — 0.013 — 0.016 — 0.018 — 0.021 — 0.024100 — 0.026 — 0.028 — 0.030 — 0.032 — 0.034 — 0.036 — 0.037 — 0.038 — 0.039 — 0.039200 — 0.040 — 0.040 — 0.040 — 0.040 — 0.040 — 0.040 — 0.040 — 0.039 — 0.039 — 0.039300 — 0.039 — 0.039 — 0.039 — 0.040 — 0.040 — 0.041 — 0.042 — 0.043 — 0.045 — 0.046400 — 0.048 — 0.051 — 0.053 — 0.056 — 0.059 — 0.062 — 0.065 — 0.068 — 0.072 — 0.075500 — 0.079 — 0.083 — 0.087 — 0.090 — 0.094 — 0.098 — 0.101 — 0.105 — 0.108 — 0.112600 — 0.115 — 0.118 — 0.122 — 0.125* — 0.08 — 0.03 0.02 0.06 0.11 0.16700 0.20 0.24 0.28 0.31 0.33 0.35 0.36 0.36 0.36 0.35800 0.34 0.32 0.29 0.25 0.22 0.18 0.14 0.10 0.06 0.03900 — 0.01 — 0.03 — 0.06 — 0.08 — 0.10 — 0.12 — 0.14 — 0.16 — 0.17 — 0.18

1000 — 0.19 — 0.20 — 0.21 — 0.22 — 0.23 — 0.24 — 0.25 — 0.25 — 0.26 — 0.26t90/°C 0 100 200 300 400 500 600 700 800 9001000 — 0.26 — 0.30 — 0.35 — 0.39 — 0.44 — 0.49 — 0.54 — 0.60 — 0.662000 — 0.72 — 0.79 — 0.85 — 0.93 — 1.00 — 1.07 — 1.15 — 1.24 — 1.32 — 1.413000 — 1.50 — 1.59 — 1.69 — 1.78 — 1.89 — 1.99 — 2.10 — 2.21 — 2.32 — 2.43

* A discontinuity in the first derivative of (t90 — t68) occurs at a temperature of t90 = 630.6 °C, at which (t90 — t68) = — 0.125 °C

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the ninth General Conference. Changes from the ITS-27 were:the lower limit of platinum resistance thermometer range waschanged from —190 °C to the defined oxygen boiling point of—182.97 °C, and the junction of the platinum resistancethermometer range and the thermocouple range became themeasured antimony freezing point (about 630 °C) in place 660 °C; the silver freezing point was defined as being 960.8 °Cinstead of 960.5 °C; the gold freezing point replaced the goldmelting point (1063 °C); the Planck radiation law replaced theWien law; the value assigned to the second radiation constantbecame 1.438 x 10—2 m · K in place of 1.432 x 10—2 m · K; thepermitted ranges for the constants of the interpolation formulafor the standard resistance thermometer and thermocouplewere modified; the limitation on lT for optical pyrometry(lT<3x10—3 m · K) was changed on the requirement that“visible” radiation be used.

The International Practical Temperature Scale of 1948 (Amended Edition of 1960) (IPTS-48)

The International Practical Temperature Scale of 1948,amended edition of 1960, was adopted by the eleventh GeneralConference: the tenth General Conference had alreadyadopted the triple point of water as the sole point defining thekelvin, the unit of thermodynamic temperature. In addition to theintroduction of the word “Practical”, the modifications to the ITS-48 were: the triple point of water, defined as being 0,01 °C,replaced the freezing point of zinc, defined as being419.505 °C, became a preferred alternative to the sulphurboiling point (444.6 °C) as a calibration point; the permittedranges for the constants of the interpolation formulae for thestandard resistance thermometer and the thermocouple werefurther modified; the restriction to “visible” radiation for opticalpyrometry was removed.Inasmuch as the numerical values of temperature on the IPTS-48 were the same as on the ITS-48, the former was not arevision of the scale of 1948 but merely an amended form of it.

The International Practical Temperature Scale of 1968 (IPTS-68)

In 1968 the International Committee of Weights and Measurespromulgated the International Practical Temperature Scale of1968, having been empowered to do so by the thirteenthGeneral Conference of 1967 — 1968. The IPTS-68incorporated very extensive changes from the IPTS-48. Theseincluded numerical changes, designed to bring to more nearlyin accord with thermodynamic temperatures, that weresufficiently large to be apparent to many users. Other changeswere as follows: the lower limit of the scale was extended downto 13.81 K; at even lower temperatures (0.5 K to 5.2 K), the useof two helium vapour pressure scales was recommended; sixnew defining fixed points were introduced — the triple point ofequilibrium hydrogen (13.81 K), an intermediate equilibriumhydrogen point (17.042 K), the normal boiling point ofequilibrium hydrogen (20.28 K), the boiling point of neon

(27.102 K), the triple point of oxygen (54.361 K), and thefreezing point of tin (231.9681 °C) which became a permittedalternative to the boiling point of water; the boiling point ofsulphur was deleted; the values assigned to four fixed pointswere changed — the boiling point of oxygen (90.188 K), thefreezing point of zinc (419.58 °C), the freezing point of silver(961.93 °C), and the freezing point of gold (1064.43 °C): theinterpolating formulae for the resistance thermometer rangebecame much more complex; the value assigned to thesecond radiation constant c2 became 1.4388 x 10—2 m · K; the permitted ranges of the constants for the interpolationformulae for the resistance thermometer and thermocouplewere again modified.

The International Practical Temperature Scale of 1968(Amended Edition of 1975) (IPTS-68)

The International Practical Temperature Scale of 1968,amended edition of 1975, was adopted by the fifteenth GeneralConference in 1975. As was the case for the IPTS-48 withrespect to the ITS-48, the IPTS-68 (75) introduced nonumerical changes. Most of the extensive textural changeswere; the oxygen point was defined as the condensation pointrather than the boiling point; the triple point of argon (83.798 K)was introduced as a permitted alternative to the condensationpoint of oxygen; new values of the isotopic composition ofnaturally occurring neon were adopted; the recommendation touse values of T given by the 1958 4He and 1962 3He vapor-pressure scales was rescinded.

The 1976 Provisional 0,5 K to 30 K Temperature Scale (EPT-76)

The 1976 Provisional 0.5 K to 30 K Temperature Scale wasintroduced to meet two important requirements: these were toprovide means of substantially reducing the errors (with respectto corresponding thermodynamic values) below 27 K that werethen known to exist in the IPTS-68 and throughout thetemperature ranges of the 4He and 3He vapour pressure scalesof 1958 and 1962 respectively, and to bridge the gap between5.2 K and 13.81 K in which there had not previously been aninternational scale. Other objectives in devising the ETP-76were “that it should be thermodynamically smooth, that it shouldbe continuous with the IPTS-68 at 27.1 K, and that is shouldagree with thermodynamic temperature T as closely as thesetwo conditions allow”. In contrast with the IPTS-68, and toensure its rapid adoption, several methods of realizing the ETP-76 were approved. These included: using athermodynamic interpolation instrument and one or more ofeleven assigned reference points; taking differences from theIPTS-68 above 13.81 K; taking differences from certain well-established laboratory scales. Because there was a certain“lack of internal consistency” it was admitted that “slightambiguities between realizations” might be introduced.However the advantages gained by adopting the EPT-76 as aworking scale until such time as the IPTS-68 should be revisedand extended were considered to outweigh the disadvantages.


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Z

International Standards AgenciesArgentina

Australia

Austria

Belgium

Canada

Denmark

Egypt

Finland

France

Germany

Hungary

India

Indonesia

Iran

Ireland

Israel

Italy

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Mexico

Netherlands

New Zealand

Norway

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Poland

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International Power Plugsand SocketsContinentalEurope

Europlug(ungrounded)

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UnitedKingdom

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Switzerland

IEC 906-1

1st Protection fromDigit Solid Objects

0 No Protection

1 Protected against solid objectsgreater than 50 mm

2 Protected against solid objects greater than 12 mm

3 Protected against solid objectsgreater than 2.5 mm

4 Protected against solid objectsgreater than 1.0 mm

5 Dust Protected

6 Dust Tight

IP Codes(Ingress Protection)

IEC 529 outlines an internationalclassification system for the sealingeffectiveness of enclosures ofelectrical equipment against theintrusion into the equipment offoreign bodies (i.e., tools, dust,fingers) and moisture.Thisclassification system utilises theletters ‘IP’ (Ingress Protection)followed by two digits. An ‘X’ is usedfor one of the digits if there is onlyone class of protection; i.e., IPX4,which addressed moistureresistance only.

Degrees of Protection – First DigitThe first digit of the IP codeindicates the degree that personsare protected against contact withmoving parts (other than rotatingshafts, etc.) and the degree thatequipment is protected against solidbodies intruding into a enclosure.

Degrees of Protection –Second DigitThe second digit indicates thedegree of protection of theequipment inside the enclosureagainst the harmful entry of variousforms of moisture (e.g., dripping,spraying, submersion, etc.).

Reproduced with permission of PanelComponents Corp.

2nd Protection fromDigit Moisture

0 No Protection

1 Protected against verticallydripping water

2 Protected against dripping water whentilted up to 15°

3 Protected against spraying water @ up to60° from vertical

4 Protected against splashing waterfrom all directions

5 Protected againstwater jets

6 Protected againstheavy seas & streamingwater

7 Protected againsteffects of short-termimmersion

8 Protected againstsubmersion

19 3

5

18.5

International Standards

®

Z-195

StandardsNEMA, UL and CSA RatingsWhat’s in a rating?As a way of standardizing enclosureperformance, organizations like NEMA, UL,CSA, IEC, VDE and TUV use rating systemsto identify an enclosure’s ability to resistexternal environmental influences.Resistance to everything from dripping liquidto hose-down to total submersion is definedby the ratings systems. While these ratingssystems are all intended to provideinformation to help you make a safer, moreinformed product choice, there aredifferences among them.

North American enclosure ratings systemsalso include a 4X rating that indicatesresistance to corrosion. This rating is basedon the enclosure’s ability to withstandprolonged exposure to salt water spray.While a 4X rating is a good indicator that anenclosure can resist corrosion, it does notprovide information on how a specificcorrosive agent will affect a given enclosurematerial. It is best to conduct a full analysis ofthe specific application and environment todetermine the best enclosure choice.

NEMA, UL and CSA RatingsNEMA, UL and CSA are standard-writingorganizations commonly recognized in NorthAmerica. Their ratings are based on similarapplication descriptions and expectedperformance. UL and CSA both requireenclosure testing by qualified evaluators. Theyalso send site inspectors to make sure amanufacturer adheres to prescribedmanufacturing methods and materialspecifications. NEMA, on the other hand, doesnot require independent testing and leavescompliance completely up to the manufacturer.

National Electrical Underwriters CanadianManufacturers Laboratories Inc. StandardsAssociation (UL 50 and UL508) Association(NEMA Standard 250) (Standard C22.2 No.94)and Electrical and Electronic Mfg.

Enclosure Association ofRating Canada (EEMAC)

Enclosures are intended for indoor Indoor use primarily to provide General purpose enclosure.use primarily to provide a degree of protection against contact with Protects against accidental contact

Type 1 protection against contact with the the enclosed equipment and with live parts.enclosed equipment or locations where against a limited amount ofunusual service conditions do not exist falling dirt.

Enclosures are intended for indoor Indoor use to provide a degree Indoor use to provide a degreeuse primarily to provide a degree of of protection against limited of protection against dripping and

Type 2 protection against limited amounts amounts of falling water and light splashing of non-corrosiveof falling water and dirt. dirt. liquids and falling dirt.

Enclosures are intended for Outdoor use to provide a Indoor or outdoor use; providesoutdoor use primarily to provide degree of protection against a degree of protection against

Type 3 a degree of protection against windblown dust and windblown rain, snow, and windblown dust;windblown dust, rain and sleet; rain; undamaged by the undamaged by the externalundamaged by the formation formation of ice on the formation of ice on the enclosure.of ice on the enclosure. enclosure.

Enclosures are intended for outdoor Outdoor use to provide a Indoor or outdoor use; providesuse primarily to provide a degree of degree of protection against a degree of protection against

Type 3R protection against falling rain and falling rain; undamaged by the rain and snow; undamaged by thesleet; undamaged by the formation formation of ice on the external formation of ice on theof ice on the enclosure. enclosure. enclosure.

Enclosures are intended for Either indoor or outdoor use to Indoor or outdoor use; providesindoor or outdoor use primarily provide a degree of protection a degree of protection againstto provide a degree of protection against falling rain, splashing rain, snow, windblown dust,

Type 4 against windblown dust and rain. water, and hose-directed water; splashing and hose-directed water; splashing water, and hose- undamaged by the formation undamaged by the external formation directed water; undamaged by of ice on the enclosure. of ice on the enclosure.the formation of ice on the enclosure.

Enclosures are intended for indoor Either indoor or outdoor use to Indoor or outdoor use; providesor outdoor use primarily to provide provide a degree of protection a degree of protection againsta degree of protection against against falling rain, splashing rain, snow, windblown dust, corrosion,windblown dust and water, and hose-directed water; splashing and hose-directed water;

Type 4X rain, splashing water, and hose- undamaged by the formation undamaged by the external formation directed water; undamaged by the of ice on the enclosure; of ice on the enclosure; resists corrosion.formation of ice on the enclosure. resists corrosion.

Enclosures are intended for Indoor or outdoor use to provide Indoor or outdoor use; providesuse indoors or outdoors where a degree of protection against a degree of protection against

Type 6 occasional submersion is entry of water during temporary the entry of water during temporaryencountered; limited depth; submersion at a limited depth; submersion.undamaged by the formation of ice undamaged by the formation ofon the enclosure; resists corrosion. ice on the enclosure.

Enclosures are intended for Indoor use to provide a degree of Indoor use; provides a degree ofindoor use primarily to provide protection against dust, dirt, fiber protection against circulating dust, lint,

Type 12 a degree of protection against flyings, dripping water, and fibers and flyings; dripping and lightdust, falling dirt, and dripping external condensation of splashing of non-corrosive liquids; notnon-corrosive liquids. non-corrosive liquids. provided with knockouts.

Enclosures are intended for Indoor use to provide a degree of Indoor use; provides a degree ofindoor use primarily to provide protection against lint, dust seepage, protection against circulating dust, lint,

Type 13 a degree of protection against external condensation and spraying of fibers and flyings, seepage and spraying ofdust, spraying of water, oil, and water, oil, and non-corrosive liquids. non-corrosive liquids, including oils and non-corrosive coolant. coolants.

This material is reproduced with permissionfrom NEMA. The preceding descriptions,however, are not intended to be completerepresentations of National ElectricalManufacturers Association standards forenclosures nor those of the Electrical andElectronic Manufacturers Association ofCanada

This material is reproduced with permission fromUnderwriters Laboratories Inc. Enclosures forElectrical Equipment, UL 50.Copyright 1995;and Industrial Control Equipment, 508, Copyright1996 by Underwriters Laboratories, Inc.

Underwriters Laboratories Inc.(UL) shall not beresponsible for the use of or reliance upon a ULStandard by anyone. UL shall not incur anyobligation or liability for damages, includingconsequential damages, arising out of or inconnection with, interpretation of, or relianceupon a UL Standard.

This material is reproduced with permission fromCanadian Standards Association.

®

LISTED

NEMA

Exposure type non-hazardous location

Z-196

Z

StandardsCE and IEC ClassificationsCEThe CE Mark is a European Union (EU)compliance symbol and acronym forConformité Européenne. The CE Markindicates that a product complies with allEuropean directives and essentialHarmonized Standards for health, safety,

environment, andconsumer protectionthat may apply to thatproduct. In addition,the CE Mark promotesfree trade movementfrom outside and withinthe EU.

For industrial control equipment, the CEMark is not intended to be applied toempty enclosures because suchenclosures are inactive components of afinal assembly. The responsibility forinsuring compliance to all applicable EUDirectives and Harmonized Standardsbelongs with the final equipmentmanufacturer.

Hoffman enclosures are designed incompliance with European standardsand are eligible to receive aManufacturer’s Declaration ofConformity. The certificate assists thefinal equipment manufacturer inobtaining the CE Mark. ContactApplications Engineering at (612) 422-2868 for further information.

Hoffman enclosures meet therequirements of the applicableEuropean standards specified below.

Applicable European Directives73/23/EEC Low Voltage Directive forElectrical Equipment within CertainVoltage Limits

89/336/EEC EMC Directive Relating toElectromagnetic Compatibility

Note: The EMC Directive is onlysecondarily applicable since an emptyenclosure does not produceelectromagnetic interference.

Applicable European StandardsEN60529-1 (IEC529-1) Degrees ofProtection Provided by Enclosures

EN60204-1 (IEC204-1) ElectricalEquipment of Industrial Machines

International Standards’ IPProtection ClassificationIEC Publication 529, Classification ofDegrees of Protection by Enclosures,provides a system for specifyingenclosures of electrical equipment onthe basis of the degree of protection

required. IEC 529 doesnot specify degrees ofprotection against riskof explosions orconditions such asmoisture (produced, forexample, bycondensation),

corrosive vapors, fungus, or vermin.NEMA Standards Publication 250 does

not test for environmental conditionssuch as corrosion, rust, icing, oil, andcoolants. For this reason, and becausethe tests and evaluations for othercharacteristics are not identical, the IECenclosure classification designationscannot be exactly equated with NEMAenclosure Type numbers.

The table on below provides a cross-reference from NEMA enclosure Typenumbers to IEC enclosure classificationdesignations. This cross-reference is aHoffman approximation based on themost current available information onenclosure test performance and is notsanctioned by NEMA, IEC, VDE, or anyaffiliated agency.

To use the table, first find theappropriate NEMA rating along thevertical axis and then read across thehorizontal axis for the corresponding IPrating. Do not use this table to convertIEC classification designations to NEMAType numbers.

In Europe, IEC ratings are based on performance criteria similar to NEMA. Nevertheless, there are differences in how enclosure performance isinterpreted. For example, UL and CSA test requirements specify that an enclosure fails the watertight test if even a single drop of water entersthe enclosure. In the IEC standards for each protection level (IP), a certain amount of water is allowed to enter the enclosure. IEC does notspecify degrees of protection against risk of explosions or conditions such as moisture or corrosive vapors. NEMA, on the other hand, doesspecify for most environmental conditions. For this reason, and because the tests and evaluations for other characteristics are not identical, theIEC enclosure classification designations cannot be exactly equated with NEMA enclosure Type numbers.

EnclosureRating IP23 IP30 IP32 IP55 IP64 IP65 IP66 IP67Type 1 •Type 2 •Type 3 •Type 3R •Type 3S •Type 4 •Type 4X •Type 6 •Type 12 •Type 13 •

Cross Reference (Approximate) NEMA, UL, CSA, vs. IEC Enclosure Type(Cannot be used to convert IEC Classifications to NEMA Type numbers)

IEC 529 has no equivalents to NEMA enclosure Types 7, 8, 9, 10, or 11.•Indicates compliance

Z-197

Application NotesLow Cost Non-Electronic Temperature Gages

When the need arises for measuringtemperatures in various industrialsituations, most engineers think in termsof expensive electronic temperaturemeasuring equipment. In many cases,though, you can do the job with lesscostly and much simpler methods. Whenthe need is only for an indication that apre-determined temperature has or hasnot been reached, heat-sensitivematerials in the form of crayons, paints,pellets, or labels can do the job readily,inexpensively, and accurately enough formost industrial applications.

WHAT ARE THESE NON-ELECTRONICTEMPERATURE INDICATINGDEVICES?These heat-sensitive, fusible materialsconsist of crystalline solids. When heated,a temperature will be reached in whichthe solids change sharply to a liquid. Themelting point is reproducible and isvirtually unaffected by ambient conditionsthat may cause errors with othertemperature-sensing methods. Forexample, electrical means of measuringtemperatures often function erratically inthe presence of static electricity, electrical“noise” or ionized air near electricalequipment.

ADVANTAGES OVER ELECTRONICDEVICESThis family of fusible temperatureindicators has several advantages overother methods of determining surfacetemperature. First, the temperatureindications obtained are unquestionablythose of the surface being tested. Thetemperature sensitive material is applieddirectly to the surface, and thereforechanges state in direct response to thatsurface, and only that surface.

A second advantage of using fusibletemperature indicators is the fact thatthere is no delay in obtaining a signal.Since a mark left by a crayon or a lacquerhas an extremely small mass, it attainsrapid equilibrium with the surface. Theuse of a “massive” probe tends to prolongresponse time and could result in anerroneously low reading. With the use offusible temperature indicators, there is noconduction of heat away from thesurface. Nor is there any dependence onthe duration of heating.

The third advantage of fusible indicatorsis that the technique for using them issimple and economical. Determiningsurface temperatures by most othermeans requires some technicalcompetence and skill and, in many cases,sophisticated instrumentation. Surfacetemperature readings can be obtainedfrom fusible indicators with little effort,training, and expense.

WHAT FORMS DO THESETEMPERATURE INDICATORS TAKE?1. Crayons: The most commonly used ofall the fusible indicators is thetemperature sensitive stick, or crayon.Each crayon has a calibrated meltingpoint. These indicators are manufacturedin 100 different temperature ratings andrange from 100˚F to 2500˚F. Each has atemperature indicating accuracy within1% of its temperature rating.Using the crayons is simple. Theworkpiece to be tested is marked with acrayon. When the pre-determined meltingpoint of the crayon mark is attained, themark instantly liquifies, notifying theobserver that the workpiece has reachedthat temperature.However, under some circumstances,premarking with a crayon is not practical.This can be the case if a prolongedheating period is involved (the crayonmark may evaporate), if the surface ishighly polished and does not readilyaccept a crayon mark, or if the materialbeing marked is such that it absorbs theliquid phase of the crayon. In suchinstances, the operator can repeatedlystroke the workpiece with the crayon. Thepoint at which the surface reaches thedesired temperature is determined bynoting when the crayon ceases to makedry marks and instead leaves a liquidsmear.2. Lacquers: Another form of heatsensitive material is a dull lacquer-typeliquid that turns glossy and transparent ata predetermined temperature. This phasechanging liquid is a fusible coatingmaterial that offers greater flexibility thancrayons as to the types of surfaces onwhich it can be applied.Chemically, this lacquer-type fluidcontains a solid material that has acalibrated melting point. These solids aresuspended in an inert, volatile, but non-flammable vehicle. Upon reaching itsrated temperature, the dull lacquer markliquifies. On subsequent cooling,however, the fluid does not revert to itsoriginal dull appearance, but rather to aglossy or crystalline coating. This shinystate of appearance is evidence that thelacquer has reached the ratedtemperature.Due to their physical properties, theselacquers are often used instead ofcrayons on very smooth surfaces (glass,plastic film, laminated plastic), softsurfaces (paper, cloth), or on surfaces notreadily accessible for application of acrayon mark during heating. Withinseconds after application, the lacquerdries to a dull matte finish. Response isonly a fraction of a second when thetemperature to be indicated is reached.This time can be reduced to millisecondsby applying a mark of minimal thickness.

These fluids are available in over 100different temperature ratings, covering therange from 100˚F to 2500˚F. As with thecrayon type indicators, accuracy is within±1%. The temperature ratings availablerange from 100˚F to 350˚F in6 increments, from 350˚F to 500˚F in12 increments, from 500˚F to 750˚F in25 increments, and from 750˚F to 2500˚Fin 50 increments.The temperature-sensitive lacquers aresupplied in the proper consistency forbrushing. If spraying or dipping ispreferred, a special thinner is added toalter the viscosity without impairing thetemperature indicating performance.3. Pellets: The first commercial form ofthe fusible indicator was the pellet, whichcontinues to be useful in certainapplications. Pellets are most frequentlyemployed when extended heating periodsare involved or when oxidation of a metalworkpiece might obscure a crayon mark.Pellets are also ideal when a relativelylarge bulk of indicator material isnecessary because observations must bemade from a distance. Another major useof pellet-type indicators is for determiningspecific air-space temperatures. A typicalapplication is the monitoring of heatzones in industrial ovens and furnaces.Phase change temperature indicatingpellets are available in flat tablets, 7⁄16” indiameter and 1⁄8” thick. For specialapplications, smaller 1⁄8” by 1⁄8” thick pelletsare also available. One application forthese miniature pellets is that of thermalfuses. The solid pellet acts as a circuitbreaker as it melts and releases tensionon a spring which, in relaxing, opens acontact, in turn, cutting off electricalcontinuity.Pellets come in the extended range from100˚F to 3000˚F. For temperaturemeasurements in hydrogen, carbonmonoxide, or other reducingenvironments, a special series of pelletsis also available.4. Labels: Another variation of thephase-change indicators is thetemperature sensitive label. Theseadhesive backed monitors consist of oneor more heat sensitive indicators sealedunder transparent, heat-resistantwindows. The centers of these indicatorsturn from white to black at thetemperature ratings as shown on thelabel face. This color change, caused bythe temperature-sensitive substancebeing absorbed into its backing material,is irreversible. After registering thetemperature history of the workpiece, theexposed monitor label can then beremoved and affixed to a service report toremain part of a permanent record.

Reproduced with permision of PentonPublishing

Z-198

Z

Temperature -210 760

Range: to to760°C 1,200°C

c0 = 0.000 000 000 0 .... 2.964 562 568 1 x 105

c1 = 5.038 118 781 5 x101 -1.497 612 778 6 x 103

c2 = 3.047 583 693 0 x 10-2 3.178 710 392 4 c3 = -8.568 106 572 0 x 10-5 -3.184 768 670 1 x 10-3

c4 = 1.322 819 529 5 x 10-7 1.572 081 900 4 x 10-6

c5 = -1.705 295 833 7 x 10-10 -3.069 136 905 6 x 10-10

c6 = 2.094 809 069 7 x 10-13

c7 = -1.253 839 533 6 x 10-16

c8 = 1.563 172 569 7 x 10-20

Type J Thermocouples - coefficients, ci, of referenceequations giving the thermoelectric voltage, E, as afunction of temperature t90, for the indicated temperatureranges. The equations are of the form:

n

E = ( ci (t90)i

i = 0

where E is in microvolts and t90 is in degrees Celsius.Temperature -210 0 760

Range: to to to0°C 760°C 1,200°C

Voltage -8,095 0 42,919

Range: to to to0 µV 42,919 µV 69,553 µV

c0 = 0.000 000 0 .... 0.000 000 .... -3.113 581 87 x 103

c1 = 1.952 826 8 x 10-2 1.978 425 x 10-2 3.005 436 84 x 10-1

c2 = -1.228 618 5 x 10-6 -2.001 204 x 10-7 -9.947 732 30 x 10-6

c3 = -1.075 217 8 x 10-9 1.036 969 x 10-11 1.702 766 30 x 10-10

c4 = -5.908 693 3 x 10-13 -2.549 687 x 10-16 -1.430 334 68 x 10-15

c5 = -1.725 671 3 x 10-16 3.585 153 x 10-21 4.738 860 84 x 10-21

c6 = -2.813 151 3 x 10-20 -5.344 285 x 10-26

c7 = -2.396 337 0 x 10-24 5.099 890 x 10-31

c8 = -8.382 332 1 x 10-29

Error 0.03 0.04 0.03Range: to to to

-0.05°C -0.04°C -0.04°C

Temperature -200 0 500

Range: to to to0°C 500°C 1,372°C

Voltage -5891 0 20,644

Range: to to to0 µV 20,644 µV 54,886 µV

c0 = 0.000 000 0 .... 0.000 000 .... -1.318 058 x 102

c1 = 2.517 346 2 x 10-2 2.508 355 x 10-2 4.830 222 x 10-2

c2 = -1.166 287 8 x 10-6 7.860 106 x 10-8 -1.646 031 x 10-6

c3 = -1.083 363 8 x 10-9 -2.503 131 x 10-10 5.464 731 x 10-11

c4 = -8.977 354 0 x 10-13 8.315 270 x 10-14 -9.650 715 x 10-16

c5 = -3.734 237 7 x 10-16 -1.228 034 x 10-17 8.802 193 x 10-21

c6 = -8.663 264 3 x 10-20 9.804 036 x 10-22 -3.110 810 x 10-26

c7 = -1.045 059 8 x 10-23 -4.413 030 x 10-26

c8 = -5.192 057 7 x 10-28 1.057 734 x 10-30

c9 = -1.052 755 x 10-35

Error 0.04°C 0.04°C 0.06°CRange: to to to

-0.02°C -0.05°C -0.05°C

Type J Thermocouples - coefficients of approximateinverse functions giving temperature, t90, as a function ofthe thermoelectric voltage, E, in selected temperature andvoltage ranges. The functions are of the form:

t90 = c0 + c1E + c2E 2+…ciE i

where E is in microvolts and t90 is in degrees Celsius.

Type K Thermocouples - coefficients α0, α1 and αi, ofreference equations giving the thermoelectric voltage, E, asa function of temperature, t90 for the indicated temperatureranges. The equation below 0°C is of the form:

n

E =( c1 (t90) i

i = 0

the equation above 0°C is of the form:n

E =( ci (t90)i + α0eα1 (t90 - 126.9686)2

i = 0

where E is the natural logarithm constant, E is inmicrovolts and t90 is in degrees Celsius.

Temperature Range: Coefficients

c0 = 0.000 000 000 0 ....c1 = 3.945 012 802 5 x 101

c2 = 2.362 237 359 8 x 10-2

c3 = -3.285 890 678 4 x 10-4

c4 = -4.990 482 877 7 x 10-6

270 to 0°C c5 = -6.750 905 917 3 x 10-8

c6 = -5.741 032 742 8 x 10-10

c7 = -3.108 887 289 4 x 10-12

c8 = -1.045 160 936 5 x 10-14

c9 = -1.988 926 687 8 x 10-17

c10 = -1.632 269 748 6 x 10-20

c0 = 1.760 041 368 6 x 101

c1 = 3.892 120 497 5 x 101

c2 = 1.855 877 003 2 x 10-2

c3 = -9.945 759 287 4 x 10-5

c4 = 3.184 094 571 9 x 10-7

0 to 1372°C c5 = -5.607 284 488 9 x 10-10

c6 = 5.607 505 905 9 x 10-13

c7 = -3.202 072 000 3 x 10-16

c8 = 9.715 114 715 2 x 10-20

c9 = -1.210 472 127 5 x 10-23

α 0 = 1.185 976 x 102

α 1 = -1.183 432 x 10-4

Type K Thermocouples - coefficients of approximateinverse functions giving temperature, t90, as a function ofthe thermoelectric voltage, E, in selected temperature andvoltage ranges. The functions are of the form:

t90 = co + c1E + c2E2 ciE i


ITS-90 Thermocouple Direct &Inverse PolynomialsDirect Polynomials provide the thermoelectric voltage (µV) from a known temperature (°C); Inverse Polynomialsprovide the temperature (°C) from a known thermoelectric voltage (µV).

Z-199

Temperature -270 0Range: to to

0°C 400°

c0 = 0.000 000 000 0.... 0.000 000 000 0....c1 = 3.874 810 636 4 x101 3.874 810 636 4 x101

c2 = 4.419 443 434 7 x 10-2 3.329 222 788 0 x10-2

c3 = 1.184 432 310 5 x 10-4 2.061 824 340 4 x 10-4

c4 = 2.003 297 355 4 x 10-5 -2.188 225 684 6 x 10-6

c5 = 9.013 801 955 9 x 10-7 1.099 688 092 8 x 10-8

c6 = 2.265 115 659 3 x 10-8 -3.081 575 877 2 x 10-11

c7 = 3.607 115 420 5 x 10-10 4.547 913 529 0 x 10-14

c8 = 3.849 393 988 3 x 10-12 -2.751 290 167 3 x 10-17

c9 = 2.821 352 192 5 x 10-14

c10 = 1.425 159 477 9 x 10-16

c11 = 4.876 866 228 6 x 10-19

c12 = 1.079 553 927 0 x 10-21

c13 = 1.394 502 706 2 x 10-24

c14 = 7.979 515 392 7 x 10-28

Type T Thermocouples - coefficients, ci, of referenceequations giving the thermoelectric voltage, E, as afunction of temperature, t90, for the indicatedtemperature ranges. The equations are of the form:

n

E =(ci (t90)i

i=0



0°C 400°C

Voltage: -5,603 0Range: to to

0 µV 20,872 µV

c0 = 0.000 000 0.... 0.000 000 ....c1 = 2.592 919 2 x 10-2 2.592 800 x 10

-2

c2 = -2.131 696 7 x 10-7 -7.602 961 x 10-7

c3 = 7.901 869 2 x 10-10 4.637 791 x 10-11

c4 = 4.252 777 7 x 10-13 -2.165 394 x 10-15

c5 = 1.330 447 3 x 10-16 6.048 144 x 10-20

c6 = 2.024 144 6 x 10-20 -7.293 422 x 10-25

c7 = 1.266 817 1 x 10-24

Error 0.04 0.03Range: to to

-0.02°C -0.03°C

Type T Thermocouples - coefficients of approximateinverse functions giving temperature, t90, as a functionof the thermoelectric voltage, E, in selected temperatureand voltage ranges. The functions are of the form:

t90 = c0 + c1E + c2E 2+…ciE i



0°C 1,000°C

Voltage -8,825 0Range: to to

0 µV 76,373 µV

c0 = 0.000 000 0 .... 0.000 000 0 ....c1 = 1.697 728 8 x 10-2 1.705 703 5 x 10-2

c2 = -4.351 497 0 x 10-7 -2.330 175 9 x 10-7

c3 = -1.585 969 7 x 10-10 6.543 558 5 x 10-12

c4 = -9.250 287 1 x 10-14 -7.356 274 9 x 10-17

c5 = -2.608 431 4 x 10-17 -1.789 600 1 x 10-21

c6 = -4.136 019 9 x 10-21 8.403 616 5 x 10-26

c7 = -3.403 403 0 x 10-25 -1.373 587 9 x 10-30

c8 = -1.156 489 0 x 10-29 1.062 982 3 x 10-35

c9 = -3.244 708 7 x 10-41


-0.01°C -0.02°C

Type E Thermocouples - coefficients of approximateinverse functions giving temperature, t90, as a functionof the thermoelectric voltage, E, in selected temperatureand voltage ranges. The functions are of the form:

t90 = c0 + c1E + c2E2+… ciE i



0°C 400°C

c0 = 0.000 000 000 0 .... 0.000 000 000 0 ....c1 = 5.866 550 870 8 x101 5.866 550 871 0 x101

c2 = 4.541 097 712 4 x 10-2 4.503 227 558 2 x10-2

c3 = -7.799 804 868 6 x 10-4 2.890 840 721 2 x 10-5

c4 = -2.580 016 084 3 x 10-5 -3.305 689 665 2 x 10-7

c5 = -5.945 258 305 7 x 10-7 6.502 440 327 0 x 10-10

c6 = -9.321 405 866 7 x 10-9 -1.919 749 550 4 x 10-1

c7 = -1.028 760 553 4 x 10-10 -1.253 660 049 7 x 10-15

c8 = -8.037 012 362 1 x 10-13 2.148 921 756 9 x 10-18

c9 = -4.397 949 739 1 x 10-15 -1.438 804 178 2 x 10-21

c10 = -1.641 477 635 5 x 10-17 3.596 089 948 1 x 10-25

c11 = -3.967 361 951 6 x 10-20

c12 = -5.582 732 872 1 x 10-23

c13 = -3.465 784 201 3 x 10-26

Type E Thermocouples - coefficients, ci, of referenceequations giving the thermoelectric voltage, E, as afunction of temperature, t90, for the indicatedtemperature ranges. The equations are of the form:

n

E = ( ci (t90)i

i=0


ITS-90 Thermocouple Direct & InversePolynomials Cont’d

Z-200

Z


0°C 1,300°C

c0 = 0.000 000 000 0.... 0.000 000 000 0....c1 = 2.615 910 596 2 x101 2.592 939 460 1 x 101

c2 = 1.095 748 422 8 x 10-2 1.571 014 188 0 x 10-2

c3 = -9.384 111 155 4 x 10-5 4.382 562 723 7 x 10-5

c4 = -4.641 203 975 9 x 10-8 -2.526 116 979 4 x 10-7

c5 = -2.630 335 771 6 x 10-9 6.431 181 933 9 x 10-10

c6 = -2.265 343 800 3 x 10-11 -1.006 347 151 9 x 10-12

c7 = -7.608 930 079 1 x 10-14 9.974 533 899 2 x 10-16

c8 = -9.341 966 783 5 x 10-17 -6.086 324 560 7 x 10-19

c9 = 2.084 922 933 9 x 10-22

c10 = -3.068 219 615 1 x 10-26

Type N Thermocouples - coefficients, ci, of referenceequations giving the thermoelectric voltage, E, as afunction of temperature, t90, for the indicatedtemperature ranges. The equations are of the form:

n

E = ( ci (t90)i

i=0


Type N Thermocouples -coefficients of approximate inversefunctions giving temperature, t90, asa function of the thermoelectricvoltage, E, in selected temperatureand voltage ranges. The functionsare of the form:

t90 = c0 + c1E + c2E2+… ciEi

where E is in microvolts and t90 is indegrees Celsius.

Temperature -200 0 600 0Range: to to to to

0°C 600°C 1,300°C 1,300°C

Voltage -3,990 0 20,613 0Range: to to to

0 µV 20,613 µV 47,513 µV 47,513 µV

c0 = 0.000 000 0 .... 0.000 00 .... 1.972 485 x 101 0.000 000 0 ....c1 = 3.843 684 7 x 10-2 3.868 96 x 10-2 3.300 943 x 10-2 3.878 327 7 x 10-2

c2 = 1.101 048 5 x 10-6 -1.082 67 x 10-6 -3.915 159 x 10-7 -1.161 234 4 x 10-6

c3 = 5.222 931 2 x 10-9 4.702 05 x 10-11 9.855 391 x 10-12 6.952 565 5 x 10-11

c4 = 7.206 052 5 x 10-12 -2.121 69 x 10-18 -1.274 371 x 10-16 -3.009 007 7 x 10-15

c5 = 5.848 858 6 x 10-15 -1.172 72 x 10-19 7.767 022 x 10-22 8.831 158 4 x 10-20

c6 = 2.775 491 6 x 10-18 5.392 80 x 10-24 -1.621 383 9 x 10-24

c7 = 7.707.516 6 x 10-22 -7.981 56 x 10-29 1.669 336 2 x 10-29

c8 = 1.158 266 5 x 10-25 -7.311 754 0 x 10-35

c9 = 7.313 886 8 x 10-30

Error 0.03 0.03 0.02 0.06Range: to to to to

-0.02°C -0.02°C -0.04°C -0.06°C

Temperature 0 630.615Range: to to

630.615°C 1,820°C

c0 = 0.000 000 000 0 .... -3.893 816 862 1 x 103

c1 = -2.465 081 834 6 x10-1 2.857 174 747 0 x 101

c2 = 5.904 042 117 1 x 10-3 -8.488 510 478 5 x 10-2

c3 = -1.325 793 163 6 x 10-6 1.578 528 016 4 x 10-4

c4 = 1.566 829 190 1 x 10-9 -1.683 534 486 4 x 10-7

c5 = -1.694 452 924 0 x 10-12 1.110 979 401 3 x 10-10

c6 = 6.229 034 709 4 x 10-16 -4.451 543 103 3 x 10-14

c7 = 9.897 564 082 1 x 10-18

c8 = -9.379 133 028 9 x 10-22

Type B Thermocouples - coefficients, ci , of referenceequations giving the thermoelectric voltage, E, as afunction of temperature, t90, for the indicatedtemperature ranges. The equations are of the form:

n

E = ( ci (t90)i

i=0

where E is in microvolts and t90 is in degrees Celsius. Temperature 250 700Range: to to

700°C 1,820°C

Voltage 291 2,431Range: to to

2,431 µV 13,820 µV

c0 = 9.842 332 1 x 101 -2.131 507 1 x 102

c1 = 6.997 150 0 x 10-1 2.851 050 4 x 10-1

c2 = -8.476 530 4 x 10-4 -5.274 288 7 x 10-5

c3 = 1.005 264 4 x 10-6 9.916 080 4 x 10-9

c4 = -8.334 595 2 x 10-10 -1.296 530 3 x 10-12

c5 = 4.550 854 2 x 10-13 1.119 587 0 x 10-16

c6 = -1.552 303 7 x 10-16 -6.062 519 9 x 10-21

c7 = 2.988 675 0 x 10-20 1.866 169 6 x 10-25

c8 = -2.474 286 0 x 10-24 -2.487 858 5 x 10-30


-0.02°C -0.01°C

Type B Thermocouples - coefficients of approximateinverse functions giving temperature, t90, as a functionof the thermoelectric voltage, E, in selected temperatureand voltage ranges. The functions are of the form:

t90 = c0 + c1E + c2E2+… ciEi


Z-201

Temperature -50 1,064.18 1,664.5Range: to to to

1,064.18°C 1,664.5°C 1,768.1°C

c0 = 0.000 000 000 0 .... 2.951 579 253 16 x 103 1.522 321 182 09 x 105

c1 = 5.289 617 297 65 .... -2.520 612 513 32 .... -2.688 198 885 45 x 102

c2 = 1.391 665 897 82 x 10-2 1.595 645 018 65 x 10-2 1.712 802 804 71 x 10-1

c3 = -2.388 556 930 17 x 10-5 -7.640 859 475 76 x 10-6 -3.458 957 064 53 x 10-5

c4 = 3.569 160 010 63 x 10-8 2.053 052 910 24 x 10-9 -9.346 339 710 46 x 10-12

c5 = -4.623 476 662 98 x 10-11 -2.933 596 681 73 x 10-13

c6 = 5.007 774 410 34 x 10-14

c7 = -3.731 058 861 91 x 10-17

c8 = 1.577 164 823 67 x 10-20

c9 = -2.810 386 252 51 x 10-24

Type R Thermocouples -coefficients, ci , of reference equationsgiving the thermoelectric voltage, E, asa function of temperature, t90, for theindicated temperature ranges. Theequations are of the for:

n

E = ( ci (t90)i

i=0


Type R Thermocouples -coefficients of approximateinverse functions givingtemperature, t90, as afunction of thethermoelectric voltage, E, inselected temperature andvoltage ranges. Thefunctions are of the form:

t90 = c0 + c1E + c2E2+…ciEi

where E is in microvolts andt90 is in degrees Celsius.

Temperature -50°C 2,500 1,064 1,664.5Range: to to to to

250°C 1,200°C 1,664.5°C 1,768.1°C

Voltage -226 1,923 11,361 19,739Range: to to to to

1,923 µV 13,228 µV 19,739 µV 21,103 µV

c0 = 0.000 000 0 .... 1.334 584 505 x 101 -8.199 599 416 x 101 3.406 177 836 x 104

c1 = 1.889 138 0 x 10-1 1.472 644 573 x 10-1 1.553 962 042 x 10-1 -7.023 729 171 ....c3 = 1.306 861 9 x 10-7 4.031 129 x 726 10-9 4.279 433 549 x 10-10 -5.582 903 813 x 10-4

c4 = -2.270 358 0 x 10-10 -6.249 428 360 x 10-13 -1.191 577 910 x 10-14 -1.952 394 635 x 10-8

c5 = 3.514 565 9 x 10-13 6.468 412 046 x 10-17 1.492 290 091 x 10-19 2.560 740 231 x 10-13

c6 = -3.895 390 0 x 10-16 -4.458 750 426 x 10-21

c7 = 2.823.947 1 x 10-19 1.994 710 146 x 10-25

c8 = -1.260 728 1 x 10-22 -5.313 401 790 x 10-30

c9 = 3.135 361 1 x 10-26 6.481 976 217 x 10-35

c10 = -3.318 776 9 x 10-30

Error 0.02 0.005 0.001 0.002Range: to to to to

-0.02°C -0.005°C -0.0005°C -0.001°C

Type S Thermocouples -coefficients of approximateinverse functions givingtemperature, t90, as afunction of thethermoelectric voltage, E, inselected temperature andvoltage ranges. Thefunctions are of the form:

t90 = c0 + c1E + c2E2+…ciE i

where E is in microvolts andt90 is in degrees Celsius.

Temperature -50 250 1,064 1,664.5Range: to to to to

250°C 1,200°C 1,664.5°C 1,768.1°CVoltage -235 1,874 10,332 17,536Range: to to to to

1,874 µV 11,950 µV 17,536 µV 18,693 µVc0 = 0.000 000 0 .... 1.291 507 177 x 101 -8.087 801 117 x 101 5.333 875 126 x 104

c1 = 1.849 494 60 x 10-1 1.466 298 863 x 10-1 1.621 573 104 x 10-1 -1.235 892 298 x 101

c2 = -8.005 040 62 x 10-5 -1.534 713 402 x 10-5 -8.536 869 453 x 10-6 1.092 657 613 x 10-3

c3 = 1.022 374 30 x 10-7 3.145 945 973 x 10-9 4.719 686 976 x 10-10 -4.265 693 686 x 10-8

c4 = -1.522 485 92 x 10-10 -4.163 257 839 x 10-13 -1.441 693 666 x 10-14 6.247 205 420 x 10-13

c5 = 1.888 213 43 x 10-13 3.187 963 771 x 10-17 2.081 618 890 x 10-19

c6 = -1.590 859 41 x 10-16 -1.291 637 500 x 10-21

c7 = 8.230 278 80 x 10-20 2.183 475 087 x 10-26

c8 = -2.341 819 44 x 10-23 -1.447 379 511 x 10-31

c9 = 2.797 862 60 x 10-27 8.211 272 125 x 10-36

0.02 0.01 0.0002 0.002Error to to to toRange: -0.02°C -0.01°C -0.0002°C -0.002°C

Temperature -50 1,064.18 1,664.5Range: to to to

1,064.18°C 1,664.5°C 1,768.1°C

c0 = 0.000 000 000 0 .... 1.329 004 450 85 x 103 1.466 282 326 36 x 105

c1 = 5.403 133 086 31.... 3.345 093 113 44 .... -2.584 305 167 52 x 102

c2 = 1.259 342 897 40 x 10-2 6.548 051 928 18 x 10-3 1.636 935 746 41 x 10-1

c3 = -2.324 779 686 89 x 10-5 -1.648 562 592 09 x 10-6 -3.304 390 469 87 x 10-5

c4 = 3.220 288 230 36 x 10-8 1.299 896 051 74 x 10-11 -9.432 236 906 12 x 10-12

c5 = -3.314 651 963 89 x 10-11

c6 = 2.557 442 517 86 x 10-14

c7 = -1.250 688 713 93 x 10-17

c8 = 2.714 431 761 45 x 10-21

Type S Thermocouples -coefficients, ci , of reference equationsgiving the thermoelectric voltage, E, asa function of temperature, t90, for theindicated temperature ranges. Theequations are of the for:

n

E = ( ci (t90)i

i=0


ITS-90 Thermocouple Direct & InversePolynomials Cont’d

Coefficients T<783˚C T ≥ 783 ˚CA 9.5685256 x 10-3 9.9109462 x 10-3

B 2.0592621 x 10-5 1.8666488 x 10-5

C -1.8464573 x 10-8 -1.4935266 x 10-8

D 7.9498033 x 10-12 5.3743821 x 10-12

E -1.4240735 x 10-15 -7.9026726 x 10-16

Z-202

®

Tungsten-RheniumThermocouples Calibration Equivalents

CALIBRATION DA similar equation is used to generate emf versustemperature values for W3ReM25Re thermocouples.For this combination, however, the curve is broken intotwo functions and the temperature is expressed inCelsius degrees.

CALIBRATIONS G AND CThe nominal emf versus temperature values forWM26Re (type G) and W5ReM26Re (type C)thermocouples are defined by fifth degreepolynominals. The emf in absolute millivolts (IPTS68)is determined, using the equation and coefficientsshown below, from the temperature in Fahrenheitdegrees.

Gen. Form: EMF = AT + BT2 + CT3 + DT4 + ET5 + K Gen. Form: EMF = AT + BT2 + CT3 + DT4 + ET5

Temp. Range: 32˚F to 4200˚F (0 to 2315˚C) Temp. Range: 32 to 4208˚F (0 to 2320˚C)

THERMOCOUPLE WIRE IDENTIFICATION GUIDE

Reprinted with Permission, from the Annual Book of ASTM Standards, CopyrightAmerican Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103

Coefficients W/W26Re W5Re/W26ReA 0.2883146 x 10-3 0.7190027 x 10-2

B 0.6783829 x 10-5 0.3956443 x 10-5

C -0.1795965 x 10-8 -0.1842722 x 10-8

D 0.2125270 x 10-12 0.3471851 x 10-12

E -0.1176051 x 10-16 -0.2616792 x 10-16

K -0.1580014 x 10-1 -0.234471

Alloy Combination Color EMF(mV)Letter +Lead -Lead Coding Maximum Useful Over Useful Standard CommentsCode Ext. Grade Temperature Range Temperature Limits of Error Environment

Range Bare WIre

TUNGSTEN TUNGSTEN 32 TO 4208˚F 0 TO 38.564 4.5˚C TO 425˚C Vacuum Inert Hydrogen.W 26% RHENIUM 0 TO 2320˚C 1.0% TO 2320˚C Beware of Embrittlement.

W-26% Re Thermocouple Grade Not Practical Below 750˚F32 to 500˚F Not for Oxidizing0 to 260˚C Atmosphere

Extension Grade

TUNGSTEN TUNGSTEN 32 TO 4208˚F 0 TO 37.066 4.5˚C TO 425˚C Vacuum Inert Hydrogen.5% RHENIUM 26% RHENIUM 0 TO 2320˚C 1.0% TO 2320˚C Beware of Embrittlement.

W-5% Re W-26% Re Thermocouple Grade Not Practical Below 750˚F32 to 1600˚F Not for Oxidizing0 to 870˚C Atmosphere

Extension Grade

TUNGSTEN TUNGSTEN 32 TO 4208˚F 0 TO 39.506 4.5˚C TO 425˚C Vacuum Inert Hydrogen.3% RHENIUM 25% RHENIUM 0 TO 2320˚C 1.0% TO 2320˚C Beware of Embrittlement.

W-3% Re W-56% Re Thermocouple Grade Not Practical Below 750˚F32 to 5000˚F Not for Oxidizing0 to 260˚C Atmosphere

Extension Grade

+–

+ WHITE

-REDWHITE -

BLUE TRACE

+–

+ WHITE

-REDWHITE -

RED TRACE

+–

+ WHITE

-REDWHITE -

YELLOW TRACE

CCC

DDD

GG

THERMOCOUPLE WIRE IDENTIFICATION GUIDE

GGGGG

+–

TYPEReferenceTablesN.I.S.T.Monograph 175Revised toITS-90

Z-203

Revised ThermocoupleReference Tables

°C -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

-200 -8.095 -8.076 -8.057 -8.037 -8.017 -7.996 -7.976 -7.955 -7.934 -7.912 -7.890 -200

-190 -7.890 -7.868 -7.846 -7.824 -7.801 -7.778 -7.755 -7.731 -7.707 -7.683 -7.659 -190-180 -7.659 -7.634 -7.610 -7.585 -7.559 -7.534 -7.508 -7.482 -7.456 -7.429 -7.403 -180-170 -7.403 -7.376 -7.348 -7.321 -7.293 -7.265 -7.237 -7.209 -7.181 -7.152 -7.123 -170-160 -7.123 -7.094 -7.064 -7.035 -7.005 -6.975 -6.944 -6.914 -6.883 -6.853 -6.821 -160-150 -6.821 -6.790 -6.759 -6.727 -6.695 -6.663 -6.631 -6.598 -6.566 -6.533 -6.500 -150

-140 -6.500 -6.467 -6.433 -6.400 -6.366 -6.332 -6.298 -6.263 -6.229 -6.194 -6.159 -140-130 -6.159 -6.124 -6.089 -6.054 -6.018 -5.982 -5.946 -5.910 -5.874 -5.838 -5.801 -130-120 -5.801 -5.764 -5.727 -5.690 -5.653 -5.616 -5.578 -5.541 -5.503 -5.465 -5.426 -120-110 -5.426 -5.388 -5.350 -5.311 -5.272 -5.233 -5.194 -5.155 -5.116 -5.076 -5.037 -110-100 -5.037 -4.997 -4.957 -4.917 -4.877 -4.836 -4.796 -4.755 -4.714 -4.674 -4.633 -100

-90 -4.633 -4.591 -4.550 -4.509 -4.467 -4.425 -4.384 -4.342 -4.300 -4.257 -4.215 -90-80 -4.215 -4.173 -4.130 -4.088 -4.045 -4.002 -3.959 -3.916 -3.872 -3.829 -3.786 -80-70 -3.786 -3.742 -3.698 -3.654 -3.610 -3.566 -3.522 -3.478 -3.434 -3.389 -3.344 -70-60 -3.344 -3.300 -3.255 -3.210 -3.165 -3.120 -3.075 -3.029 -2.984 -2.938 -2.893 -60-50 -2.893 -2.847 -2.801 -2.755 -2.709 -2.663 -2.617 -2.571 -2.524 -2.478 -2.431 -50

-40 -2.431 -2.385 -2.338 -2.291 -2.244 -2.197 -2.150 -2.103 -2.055 -2.008 -1.961 -40-30 -1.961 -1.913 -1.865 -1.818 -1.770 -1.722 -1.674 -1.626 -1.578 -1.530 -1.482 -30-20 -1.482 -1.433 -1.385 -1.336 -1.288 -1.239 -1.190 -1.142 -1.093 -1.044 -0.995 -20-10 -0.995 -0.946 -0.896 -0.847 -0.798 -0.749 -0.699 -0.650 -0.600 -0.550 -0.501 -10

0 -0.501 -0.451 -0.401 -0.351 -0.301 -0.251 -0.201 -0.151 -0.101 -0.050 0.000 0

0 0.000 0.050 0.101 0.151 0.202 0.253 0.303 0.354 0.405 0.456 0.507 010 0.507 0.558 0.609 0.660 0.711 0.762 0.814 0.865 0.916 0.968 1.019 1020 1.019 1.071 1.122 1.174 1.226 1.277 1.329 1.381 1.433 1.485 1.537 2030 1.537 1.589 1.641 1.693 1.745 1.797 1.849 1.902 1.954 2.006 2.059 3040 2.059 2.111 2.164 2.216 2.269 2.322 2.374 2.427 2.480 2.532 2.585 40

50 2.585 2.638 2.691 2.744 2.797 2.850 2.903 2.956 3.009 3.062 3.116 5060 3.116 3.169 3.222 3.275 3.329 3.382 3.436 3.489 3.543 3.596 3.650 6070 3.650 3.703 3.757 3.810 3.864 3.918 3.971 4.025 4.079 4.133 4.187 7080 4.187 4.240 4.294 4.348 4.402 4.456 4.510 4.564 4.618 4.672 4.726 8090 4.726 4.781 4.835 4.889 4.943 4.997 5.052 5.106 5.160 5.215 5.269 90

100 5.269 5.323 5.378 5.432 5.487 5.541 5.595 5.650 5.705 5.759 5.814 100110 5.814 5.868 5.923 5.977 6.032 6.087 6.141 6.196 6.251 6.306 6.360 110120 6.360 6.415 6.470 6.525 6.579 6.634 6.689 6.744 6.799 6.854 6.909 120130 6.909 6.964 7.019 7.074 7.129 7.184 7.239 7.294 7.349 7.404 7.459 130140 7.459 7.514 7.569 7.624 7.679 7.734 7.789 7.844 7.900 7.955 8.010 140

150 8.010 8.065 8.120 8.175 8.231 8.286 8.341 8.396 8.452 8.507 8.562 150160 8.562 8.618 8.673 8.728 8.783 8.839 8.894 8.949 9.005 9.060 9.115 160170 9.115 9.171 9.226 9.282 9.337 9.392 9.448 9.503 9.559 9.614 9.669 170180 9.669 9.725 9.780 9.836 9.891 9.947 10.002 10.057 10.113 10.168 10.224 180190 10.224 10.279 10.335 10.390 10.446 10.501 10.557 10.612 10.668 10.723 10.779 190

200 10.779 10.834 10.890 10.945 11.001 11.056 11.112 11.167 11.223 11.278 11.334 200210 11.334 11.389 11.445 11.501 11.556 11.612 11.667 11.723 11.778 11.834 11.889 210220 11.889 11.945 12.000 12.056 12.111 12.167 12.222 12.278 12.334 12.389 12.445 220230 12.445 12.500 12.556 12.611 12.667 12.722 12.778 12.833 12.889 12.944 13.000 230240 13.000 13.056 13.111 13.167 13.222 13.278 13.333 13.389 13.444 13.500 13.555 240

250 13.555 13.611 13.666 13.722 13.777 13.833 13.888 13.944 13.999 14.055 14.110 250260 14.110 14.166 14.221 14.277 14.332 14.388 14.443 14.499 14.554 14.609 14.665 260270 14.665 14.720 14.776 14.831 14.887 14.942 14.998 15.053 15.109 15.164 15.219 270280 15.219 15.275 15.330 15.386 15.441 15.496 15.552 15.607 15.663 15.718 15.773 280290 15.773 15.829 15.884 15.940 15.995 16.050 16.106 16.161 16.216 16.272 16.327 290

300 16.327 16.383 16.438 16.493 16.549 16.604 16.659 16.715 16.770 16.825 16.881 300310 16.881 16.936 16.991 17.046 17.102 17.157 17.212 17.268 17.323 17.378 17.434 310320 17.434 17.489 17.544 17.599 17.655 17.710 17.765 17.820 17.876 17.931 17.986 320330 17.986 18.041 18.097 18.152 18.207 18.262 18.318 18.373 18.428 18.483 18.538 330340 18.538 18.594 18.649 18.704 18.759 18.814 18.870 18.925 18.980 19.035 19.090 340

350 19.090 19.146 19.201 19.256 19.311 19.366 19.422 19.477 19.532 19.587 19.642 350360 19.642 19.697 19.753 19.808 19.863 19.918 19.973 20.028 20.083 20.139 20.194 360370 20.194 20.249 20.304 20.359 20.414 20.469 20.525 20.580 20.635 20.690 20.745 370380 20.745 20.800 20.855 20.911 20.966 21.021 21.076 21.131 21.186 21.241 21.297 380390 21.297 21.352 21.407 21.462 21.517 21.572 21.627 21.683 21.738 21.793 21.848 390

400 21.848 21.903 21.958 22.014 22.069 22.124 22.179 22.234 22.289 22.345 22.400 400410 22.400 22.455 22.510 22.565 22.620 22.676 22.731 22.786 22.841 22.896 22.952 410420 22.952 23.007 23.062 23.117 23.172 23.228 23.283 23.338 23.393 23.449 23.504 420430 23.504 23.559 23.614 23.670 23.725 23.780 23.835 23.891 23.946 24.001 24.057 430440 24.057 24.112 24.167 24.223 24.278 24.333 24.389 24.444 24.499 24.555 24.610 440

450 24.610 24.665 24.721 24.776 24.832 24.887 24.943 24.998 25.053 25.109 25.164 450460 25.164 25.220 25.275 25.331 25.386 25.442 25.497 25.553 25.608 25.664 25.720 460470 25.720 25.775 25.831 25.886 25.942 25.998 26.053 26.109 26.165 26.220 26.276 470480 26.276 26.332 26.387 26.443 26.499 26.555 26.610 26.666 26.722 26.778 26.834 480490 26.834 26.889 26.945 27.001 27.057 27.113 27.169 27.225 27.281 27.337 27.393 490

500 27.393 27.449 27.505 27.561 27.617 27.673 27.729 27.785 27.841 27.897 27.953 500510 27.953 28.010 28.066 28.122 28.178 28.234 28.291 28.347 28.403 28.460 28.516 510520 28.516 28.572 28.629 28.685 28.741 28.798 28.854 28.911 28.967 29.024 29.080 520530 29.080 29.137 29.194 29.250 29.307 29.363 29.420 29.477 29.534 29.590 29.647 530540 29.647 29.704 29.761 29.818 29.874 29.931 29.988 30.045 30.102 30.159 30.216 540

550 30.216 30.273 30.330 30.387 30.444 30.502 30.559 30.616 30.673 30.730 30.788 550560 30.788 30.845 30.902 30.960 31.017 31.074 31.132 31.189 31.247 31.304 31.362 560570 31.362 31.419 31.477 31.535 31.592 31.650 31.708 31.766 31.823 31.881 31.939 570580 31.939 31.997 32.055 32.113 32.171 32.229 32.287 32.345 32.403 32.461 32.519 580590 32.519 32.577 32.636 32.694 32.752 32.810 32.869 32.927 32.985 33.044 33.102 590

600 33.102 33.161 33.219 33.278 33.337 33.395 33.454 33.513 33.571 33.630 33.689 600610 33.689 33.748 33.807 33.866 33.925 33.984 34.043 34.102 34.161 34.220 34.279 610620 34.279 34.338 34.397 34.457 34.516 34.575 34.635 34.694 34.754 34.813 34.873 620630 34.873 34.932 34.992 35.051 35.111 35.171 35.230 35.290 35.350 35.410 35.470 630640 35.470 35.530 35.590 35.650 35.710 35.770 35.830 35.890 35.950 36.010 36.071 640

650 36.071 36.131 36.191 36.252 36.312 36.373 36.433 36.494 36.554 36.615 36.675 650660 36.675 36.736 36.797 36.858 36.918 36.979 37.040 37.101 37.162 37.223 37.284 660670 37.284 37.345 37.406 37.467 37.528 37.590 37.651 37.712 37.773 37.835 37.896 670680 37.896 37.958 38.019 38.081 38.142 38.204 38.265 38.327 38.389 38.450 38.512 680690 38.512 38.574 38.636 38.698 38.760 38.822 38.884 38.946 39.008 39.070 39.132 690

700 39.132 39.194 39.256 39.318 39.381 39.443 39.505 39.568 39.630 39.693 39.755 700710 39.755 39.818 39.880 39.943 40.005 40.068 40.131 40.193 40.256 40.319 40.382 710720 40.382 40.445 40.508 40.570 40.633 40.696 40.759 40.822 40.886 40.949 41.012 720730 41.012 41.075 41.138 41.201 41.265 41.328 41.391 41.455 41.518 41.581 41.645 730740 41.645 41.708 41.772 41.835 41.899 41.962 42.026 42.090 42.153 42.217 42.281 740

750 42.281 42.344 42.408 42.472 42.536 42.599 42.663 42.727 42.791 42.855 42.919 750760 42.919 42.983 43.047 43.111 43.175 43.239 43.303 43.367 43.431 43.495 43.559 760770 43.559 43.624 43.688 43.752 43.817 43.881 43.945 44.010 44.074 44.139 44.203 770780 44.203 44.267 44.332 44.396 44.461 44.525 44.590 44.655 44.719 44.784 44.848 780790 44.848 44.913 44.977 45.042 45.107 45.171 45.236 45.301 45.365 45.430 45.494 790

800 45.494 45.559 45.624 45.688 45.753 45.818 45.882 45.947 46.011 46.076 46.141 800810 46.141 46.205 46.270 46.334 46.399 46.464 46.528 46.593 46.657 46.722 46.786 810820 46.786 46.851 46.915 46.980 47.044 47.109 47.173 47.238 47.302 47.367 47.431 820830 47.431 47.495 47.560 47.624 47.688 47.753 47.817 47.881 47.946 48.010 48.074 830840 48.074 48.138 48.202 48.267 48.331 48.395 48.459 48.523 48.587 48.651 48.715 840

850 48.715 48.779 48.843 48.907 48.971 49.034 49.098 49.162 49.226 49.290 49.353 850860 49.353 49.417 49.481 49.544 49.608 49.672 49.735 49.799 49.862 49.926 49.989 860870 49.989 50.052 50.116 50.179 50.243 50.306 50.369 50.432 50.495 50.559 50.622 870880 50.622 50.685 50.748 50.811 50.874 50.937 51.000 51.063 51.126 51.188 51.251 880890 51.251 51.314 51.377 51.439 51.502 51.565 51.627 51.690 51.752 51.815 51.877 890

900 51.877 51.940 52.002 52.064 52.127 52.189 52.251 52.314 52.376 52.438 52.500 900910 52.500 52.562 52.624 52.686 52.748 52.810 52.872 52.934 52.996 53.057 53.119 910920 53.119 53.181 53.243 53.304 53.366 53.427 53.489 53.550 53.612 53.673 53.735 920930 53.735 53.796 53.857 53.919 53.980 54.041 54.102 54.164 54.225 54.286 54.347 930940 54.347 54.408 54.469 54.530 54.591 54.652 54.713 54.773 54.834 54.895 54.956 940

950 54.956 55.016 55.077 55.138 55.198 55.259 55.319 55.380 55.440 55.501 55.561 950960 55.561 55.622 55.682 55.742 55.803 55.863 55.923 55.983 56.043 56.104 56.164 960970 56.164 56.224 56.284 56.344 56.404 56.464 56.524 56.584 56.643 56.703 56.763 970980 56.763 56.823 56.883 56.942 57.002 57.062 57.121 57.181 57.240 57.300 57.360 980990 57.360 57.419 57.479 57.538 57.597 57.657 57.716 57.776 57.835 57.894 57.953 990

1000 57.953 58.013 58.072 58.131 58.190 58.249 58.309 58.368 58.427 58.486 58.545 10001010 58.545 58.604 58.663 58.722 58.781 58.840 58.899 58.957 59.016 59.075 59.134 10101020 59.134 59.193 59.252 59.310 59.369 59.428 59.487 59.545 59.604 59.663 59.721 10201030 59.721 59.780 59.838 59.897 59.956 60.014 60.073 60.131 60.190 60.248 60.307 10301040 60.307 60.365 60.423 60.482 60.540 60.599 60.657 60.715 60.774 60.832 60.890 1040

1050 60.890 60.949 61.007 61.065 61.123 61.182 61.240 61.298 61.356 61.415 61.473 10501060 61.473 61.531 61.589 61.647 61.705 61.763 61.822 61.880 61.938 61.996 62.054 10601070 62.054 62.112 62.170 62.228 62.286 62.344 62.402 62.460 62.518 62.576 62.634 10701080 62.634 62.692 62.750 62.808 62.866 62.924 62.982 63.040 63.098 63.156 63.214 10801090 63.214 63.271 63.329 63.387 63.445 63.503 63.561 63.619 63.677 63.734 63.792 1090

1100 63.792 63.850 63.908 63.966 64.024 64.081 64.139 64.197 64.255 64.313 64.370 11001110 64.370 64.428 64.486 64.544 64.602 64.659 64.717 64.775 64.833 64.890 64.948 11101120 64.948 65.006 65.064 65.121 65.179 65.237 65.295 65.352 65.410 65.468 65.525 11201130 65.525 65.583 65.641 65.699 65.756 65.814 65.872 65.929 65.987 66.045 66.102 11301140 66.102 66.160 66.218 66.275 66.333 66.391 66.448 66.506 66.564 66.621 66.679 1140

1150 66.679 66.737 66.794 66.852 66.910 66.967 67.025 67.082 67.140 67.198 67.255 11501160 67.255 67.313 67.370 67.428 67.486 67.543 67.601 67.658 67.716 67.773 67.831 11601170 67.831 67.888 67.946 68.003 68.061 68.119 68.176 68.234 68.291 68.348 68.406 11701180 68.406 68.463 68.521 68.578 68.636 68.693 68.751 68.808 68.865 68.923 68.980 11801190 68.980 69.037 69.095 69.152 69.209 69.267 69.324 69.381 69.439 69.496 69.553 1190

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 1382°F0 to 750°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 2.2°C or 0.75%Special: 1.1°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Reducing, Vacuum, Inert; Limited Use inOxidizing at High Temperatures; Not Recommended for Low TemperaturesTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°CJJ

ThermocoupleGrade

Ironvs.

Copper-Nickel

ExtensionGrade

+–

+–

Thermoelectric Voltage in Millivolts


Z-204

Z


-260 -6.458 -6.457 -6.456 -6.455 -6.453 -6.452 -6.450 -6.448 -6.446 -6.444 -6.441 -260-250 -6.441 -6.438 -6.435 -6.432 -6.429 -6.425 -6.421 -6.417 -6.413 -6.408 -6.404 -250

-240 -6.404 -6.399 -6.393 -6.388 -6.382 -6.377 -6.370 -6.364 -6.358 -6.351 -6.344 -240-230 -6.344 -6.337 -6.329 -6.322 -6.314 -6.306 -6.297 -6.289 -6.280 -6.271 -6.262 -230-220 -6.262 -6.252 -6.243 -6.233 -6.223 -6.213 -6.202 -6.192 -6.181 -6.170 -6.158 -220-210 -6.158 -6.147 -6.135 -6.123 -6.111 -6.099 -6.087 -6.074 -6.061 -6.048 -6.035 -210-200 -6.035 -6.021 -6.007 -5.994 -5.980 -5.965 -5.951 -5.936 -5.922 -5.907 -5.891 -200

-190 -5.891 -5.876 -5.861 -5.845 -5.829 -5.813 -5.797 -5.780 -5.763 -5.747 -5.730 -190-180 -5.730 -5.713 -5.695 -5.678 -5.660 -5.642 -5.624 -5.606 -5.588 -5.569 -5.550 -180-170 -5.550 -5.531 -5.512 -5.493 -5.474 -5.454 -5.435 -5.415 -5.395 -5.374 -5.354 -170-160 -5.354 -5.333 -5.313 -5.292 -5.271 -5.250 -5.228 -5.207 -5.185 -5.163 -5.141 -160-150 -5.141 -5.119 -5.097 -5.074 -5.052 -5.029 -5.006 -4.983 -4.960 -4.936 -4.913 -150

-140 -4.913 -4.889 -4.865 -4.841 -4.817 -4.793 -4.768 -4.744 -4.719 -4.694 -4.669 -140-130 -4.669 -4.644 -4.618 -4.593 -4.567 -4.542 -4.516 -4.490 -4.463 -4.437 -4.411 -130-120 -4.411 -4.384 -4.357 -4.330 -4.303 -4.276 -4.249 -4.221 -4.194 -4.166 -4.138 -120-110 -4.138 -4.110 -4.082 -4.054 -4.025 -3.997 -3.968 -3.939 -3.911 -3.882 -3.852 -110-100 -3.852 -3.823 -3.794 -3.764 -3.734 -3.705 -3.675 -3.645 -3.614 -3.584 -3.554 -100

-90 -3.554 -3.523 -3.492 -3.462 -3.431 -3.400 -3.368 -3.337 -3.306 -3.274 -3.243 -90-80 -3.243 -3.211 -3.179 -3.147 -3.115 -3.083 -3.050 -3.018 -2.986 -2.953 -2.920 -80-70 -2.920 -2.887 -2.854 -2.821 -2.788 -2.755 -2.721 -2.688 -2.654 -2.620 -2.587 -70-60 -2.587 -2.553 -2.519 -2.485 -2.450 -2.416 -2.382 -2.347 -2.312 -2.278 -2.243 -60-50 -2.243 -2.208 -2.173 -2.138 -2.103 -2.067 -2.032 -1.996 -1.961 -1.925 -1.889 -50

-40 -1.889 -1.854 -1.818 -1.782 -1.745 -1.709 -1.673 -1.637 -1.600 -1.564 -1.527 -40-30 -1.527 -1.490 -1.453 -1.417 -1.380 -1.343 -1.305 -1.268 -1.231 -1.194 -1.156 -30-20 -1.156 -1.119 -1.081 -1.043 -1.006 -0.968 -0.930 -0.892 -0.854 -0.816 -0.778 -20-10 -0.778 -0.739 -0.701 -0.663 -0.624 -0.586 -0.547 -0.508 -0.470 -0.431 -0.392 -10

0 -0.392 -0.353 -0.314 -0.275 -0.236 -0.197 -0.157 -0.118 -0.079 -0.039 0.000 0

0 0.000 0.039 0.079 0.119 0.158 0.198 0.238 0.277 0.317 0.357 0.397 010 0.397 0.437 0.477 0.517 0.557 0.597 0.637 0.677 0.718 0.758 0.798 1020 0.798 0.838 0.879 0.919 0.960 1.000 1.041 1.081 1.122 1.163 1.203 2030 1.203 1.244 1.285 1.326 1.366 1.407 1.448 1.489 1.530 1.571 1.612 3040 1.612 1.653 1.694 1.735 1.776 1.817 1.858 1.899 1.941 1.982 2.023 40

50 2.023 2.064 2.106 2.147 2.188 2.230 2.271 2.312 2.354 2.395 2.436 5060 2.436 2.478 2.519 2.561 2.602 2.644 2.685 2.727 2.768 2.810 2.851 6070 2.851 2.893 2.934 2.976 3.017 3.059 3.100 3.142 3.184 3.225 3.267 7080 3.267 3.308 3.350 3.391 3.433 3.474 3.516 3.557 3.599 3.640 3.682 8090 3.682 3.723 3.765 3.806 3.848 3.889 3.931 3.972 4.013 4.055 4.096 90

100 4.096 4.138 4.179 4.220 4.262 4.303 4.344 4.385 4.427 4.468 4.509 100110 4.509 4.550 4.591 4.633 4.674 4.715 4.756 4.797 4.838 4.879 4.920 110120 4.920 4.961 5.002 5.043 5.084 5.124 5.165 5.206 5.247 5.288 5.328 120130 5.328 5.369 5.410 5.450 5.491 5.532 5.572 5.613 5.653 5.694 5.735 130140 5.735 5.775 5.815 5.856 5.896 5.937 5.977 6.017 6.058 6.098 6.138 140

150 6.138 6.179 6.219 6.259 6.299 6.339 6.380 6.420 6.460 6.500 6.540 150160 6.540 6.580 6.620 6.660 6.701 6.741 6.781 6.821 6.861 6.901 6.941 160170 6.941 6.981 7.021 7.060 7.100 7.140 7.180 7.220 7.260 7.300 7.340 170180 7.340 7.380 7.420 7.460 7.500 7.540 7.579 7.619 7.659 7.699 7.739 180190 7.739 7.779 7.819 7.859 7.899 7.939 7.979 8.019 8.059 8.099 8.138 190

200 8.138 8.178 8.218 8.258 8.298 8.338 8.378 8.418 8.458 8.499 8.539 200210 8.539 8.579 8.619 8.659 8.699 8.739 8.779 8.819 8.860 8.900 8.940 210220 8.940 8.980 9.020 9.061 9.101 9.141 9.181 9.222 9.262 9.302 9.343 220230 9.343 9.383 9.423 9.464 9.504 9.545 9.585 9.626 9.666 9.707 9.747 230240 9.747 9.788 9.828 9.869 9.909 9.950 9.991 10.031 10.072 10.113 10.153 240

250 10.153 10.194 10.235 10.276 10.316 10.357 10.398 10.439 10.480 10.520 10.561 250260 10.561 10.602 10.643 10.684 10.725 10.766 10.807 10.848 10.889 10.930 10.971 260270 10.971 11.012 11.053 11.094 11.135 11.176 11.217 11.259 11.300 11.341 11.382 270280 11.382 11.423 11.465 11.506 11.547 11.588 11.630 11.671 11.712 11.753 11.795 280290 11.795 11.836 11.877 11.919 11.960 12.001 12.043 12.084 12.126 12.167 12.209 290

300 12.209 12.250 12.291 12.333 12.374 12.416 12.457 12.499 12.540 12.582 12.624 300310 12.624 12.665 12.707 12.748 12.790 12.831 12.873 12.915 12.956 12.998 13.040 310320 13.040 13.081 13.123 13.165 13.206 13.248 13.290 13.331 13.373 13.415 13.457 320330 13.457 13.498 13.540 13.582 13.624 13.665 13.707 13.749 13.791 13.833 13.874 330340 13.874 13.916 13.958 14.000 14.042 14.084 14.126 14.167 14.209 14.251 14.293 340

350 14.293 14.335 14.377 14.419 14.461 14.503 14.545 14.587 14.629 14.671 14.713 350360 14.713 14.755 14.797 14.839 14.881 14.923 14.965 15.007 15.049 15.091 15.133 360370 15.133 15.175 15.217 15.259 15.301 15.343 15.385 15.427 15.469 15.511 15.554 370380 15.554 15.596 15.638 15.680 15.722 15.764 15.806 15.849 15.891 15.933 15.975 380390 15.975 16.017 16.059 16.102 16.144 16.186 16.228 16.270 16.313 16.355 16.397 390

400 16.397 16.439 16.482 16.524 16.566 16.608 16.651 16.693 16.735 16.778 16.820 400410 16.820 16.862 16.904 16.947 16.989 17.031 17.074 17.116 17.158 17.201 17.243 410420 17.243 17.285 17.328 17.370 17.413 17.455 17.497 17.540 17.582 17.624 17.667 420430 17.667 17.709 17.752 17.794 17.837 17.879 17.921 17.964 18.006 18.049 18.091 430440 18.091 18.134 18.176 18.218 18.261 18.303 18.346 18.388 18.431 18.473 18.516 440

450 18.516 18.558 18.601 18.643 18.686 18.728 18.771 18.813 18.856 18.898 18.941 450460 18.941 18.983 19.026 19.068 19.111 19.154 19.196 19.239 19.281 19.324 19.366 460470 19.366 19.409 19.451 19.494 19.537 19.579 19.622 19.664 19.707 19.750 19.792 470480 19.792 19.835 19.877 19.920 19.962 20.005 20.048 20.090 20.133 20.175 20.218 480490 20.218 20.261 20.303 20.346 20.389 20.431 20.474 20.516 20.559 20.602 20.644 490

500 20.644 20.687 20.730 20.772 20.815 20.857 20.900 20.943 20.985 21.028 21.071 500510 21.071 21.113 21.156 21.199 21.241 21.284 21.326 21.369 21.412 21.454 21.497 510520 21.497 21.540 21.582 21.625 21.668 21.710 21.753 21.796 21.838 21.881 21.924 520530 21.924 21.966 22.009 22.052 22.094 22.137 22.179 22.222 22.265 22.307 22.350 530540 22.350 22.393 22.435 22.478 22.521 22.563 22.606 22.649 22.691 22.734 22.776 540

550 22.776 22.819 22.862 22.904 22.947 22.990 23.032 23.075 23.117 23.160 23.203 550560 23.203 23.245 23.288 23.331 23.373 23.416 23.458 23.501 23.544 23.586 23.629 560570 23.629 23.671 23.714 23.757 23.799 23.842 23.884 23.927 23.970 24.012 24.055 570580 24.055 24.097 24.140 24.182 24.225 24.267 24.310 24.353 24.395 24.438 24.480 580590 24.480 24.523 24.565 24.608 24.650 24.693 24.735 24.778 24.820 24.863 24.905 590

600 24.905 24.948 24.990 25.033 25.075 25.118 25.160 25.203 25.245 25.288 25.330 600610 25.330 25.373 25.415 25.458 25.500 25.543 25.585 25.627 25.670 25.712 25.755 610620 25.755 25.797 25.840 25.882 25.924 25.967 26.009 26.052 26.094 26.136 26.179 620630 26.179 26.221 26.263 26.306 26.348 26.390 26.433 26.475 26.517 26.560 26.602 630640 26.602 26.644 26.687 26.729 26.771 26.814 26.856 26.898 26.940 26.983 27.025 640

650 27.025 27.067 27.109 27.152 27.194 27.236 27.278 27.320 27.363 27.405 27.447 650660 27.447 27.489 27.531 27.574 27.616 27.658 27.700 27.742 27.784 27.826 27.869 660670 27.869 27.911 27.953 27.995 28.037 28.079 28.121 28.163 28.205 28.247 28.289 670680 28.289 28.332 28.374 28.416 28.458 28.500 28.542 28.584 28.626 28.668 28.710 680690 28.710 28.752 28.794 28.835 28.877 28.919 28.961 29.003 29.045 29.087 29.129 690

700 29.129 29.171 29.213 29.255 29.297 29.338 29.380 29.422 29.464 29.506 29.548 700710 29.548 29.589 29.631 29.673 29.715 29.757 29.798 29.840 29.882 29.924 29.965 710720 29.965 30.007 30.049 30.090 30.132 30.174 30.216 30.257 30.299 30.341 30.382 720730 30.382 30.424 30.466 30.507 30.549 30.590 30.632 30.674 30.715 30.757 30.798 730740 30.798 30.840 30.881 30.923 30.964 31.006 31.047 31.089 31.130 31.172 31.213 740

750 31.213 31.255 31.296 31.338 31.379 31.421 31.462 31.504 31.545 31.586 31.628 750760 31.628 31.669 31.710 31.752 31.793 31.834 31.876 31.917 31.958 32.000 32.041 760770 32.041 32.082 32.124 32.165 32.206 32.247 32.289 32.330 32.371 32.412 32.453 770780 32.453 32.495 32.536 32.577 32.618 32.659 32.700 32.742 32.783 32.824 32.865 780790 32.865 32.906 32.947 32.988 33.029 33.070 33.111 33.152 33.193 33.234 33.275 790

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 328 to 2282°F– 200 to 1250°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 2.2°C or 0.75% Above 0°C2.2°C or 2.0% Below 0°CSpecial: 1.1°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Clean Oxidizing and Inert; Limited Use inVacuum or Reducing; Wide TemperatureRange; Most Popular CalibrationTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°C KK

°C -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

ThermocoupleGrade

Nickel-Chromiumvs.

Nickel-Aluminum

ExtensionGrade

+–

+–


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C


Z-205


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

800 33.275 33.316 33.357 33.398 33.439 33.480 33.521 33.562 33.603 33.644 33.685 800810 33.685 33.726 33.767 33.808 33.848 33.889 33.930 33.971 34.012 34.053 34.093 810820 34.093 34.134 34.175 34.216 34.257 34.297 34.338 34.379 34.420 34.460 34.501 820830 34.501 34.542 34.582 34.623 34.664 34.704 34.745 34.786 34.826 34.867 34.908 830840 34.908 34.948 34.989 35.029 35.070 35.110 35.151 35.192 35.232 35.273 35.313 840

850 35.313 35.354 35.394 35.435 35.475 35.516 35.556 35.596 35.637 35.677 35.718 850860 35.718 35.758 35.798 35.839 35.879 35.920 35.960 36.000 36.041 36.081 36.121 860870 36.121 36.162 36.202 36.242 36.282 36.323 36.363 36.403 36.443 36.484 36.524 870880 36.524 36.564 36.604 36.644 36.685 36.725 36.765 36.805 36.845 36.885 36.925 880890 36.925 36.965 37.006 37.046 37.086 37.126 37.166 37.206 37.246 37.286 37.326 890

900 37.326 37.366 37.406 37.446 37.486 37.526 37.566 37.606 37.646 37.686 37.725 900910 37.725 37.765 37.805 37.845 37.885 37.925 37.965 38.005 38.044 38.084 38.124 910920 38.124 38.164 38.204 38.243 38.283 38.323 38.363 38.402 38.442 38.482 38.522 920930 38.522 38.561 38.601 38.641 38.680 38.720 38.760 38.799 38.839 38.878 38.918 930940 38.918 38.958 38.997 39.037 39.076 39.116 39.155 39.195 39.235 39.274 39.314 940

950 39.314 39.353 39.393 39.432 39.471 39.511 39.550 39.590 39.629 39.669 39.708 950960 39.708 39.747 39.787 39.826 39.866 39.905 39.944 39.984 40.023 40.062 40.101 960970 40.101 40.141 40.180 40.219 40.259 40.298 40.337 40.376 40.415 40.455 40.494 970980 40.494 40.533 40.572 40.611 40.651 40.690 40.729 40.768 40.807 40.846 40.885 980990 40.885 40.924 40.963 41.002 41.042 41.081 41.120 41.159 41.198 41.237 41.276 990

1000 41.276 41.315 41.354 41.393 41.431 41.470 41.509 41.548 41.587 41.626 41.665 10001010 41.665 41.704 41.743 41.781 41.820 41.859 41.898 41.937 41.976 42.014 42.053 10101020 42.053 42.092 42.131 42.169 42.208 42.247 42.286 42.324 42.363 42.402 42.440 10201030 42.440 42.479 42.518 42.556 42.595 42.633 42.672 42.711 42.749 42.788 42.826 10301040 42.826 42.865 42.903 42.942 42.980 43.019 43.057 43.096 43.134 43.173 43.211 1040

1050 43.211 43.250 43.288 43.327 43.365 43.403 43.442 43.480 43.518 43.557 43.595 10501060 43.595 43.633 43.672 43.710 43.748 43.787 43.825 43.863 43.901 43.940 43.978 10601070 43.978 44.016 44.054 44.092 44.130 44.169 44.207 44.245 44.283 44.321 44.359 10701080 44.359 44.397 44.435 44.473 44.512 44.550 44.588 44.626 44.664 44.702 44.740 10801090 44.740 44.778 44.816 44.853 44.891 44.929 44.967 45.005 45.043 45.081 45.119 1090

1100 45.119 45.157 45.194 45.232 45.270 45.308 45.346 45.383 45.421 45.459 45.497 11001110 45.497 45.534 45.572 45.610 45.647 45.685 45.723 45.760 45.798 45.836 45.873 11101120 45.873 45.911 45.948 45.986 46.024 46.061 46.099 46.136 46.174 46.211 46.249 11201130 46.249 46.286 46.324 46.361 46.398 46.436 46.473 46.511 46.548 46.585 46.623 11301140 46.623 46.660 46.697 46.735 46.772 46.809 46.847 46.884 46.921 46.958 46.995 1140

1150 46.995 47.033 47.070 47.107 47.144 47.181 47.218 47.256 47.293 47.330 47.367 11501160 47.367 47.404 47.441 47.478 47.515 47.552 47.589 47.626 47.663 47.700 47.737 11601170 47.737 47.774 47.811 47.848 47.884 47.921 47.958 47.995 48.032 48.069 48.105 11701180 48.105 48.142 48.179 48.216 48.252 48.289 48.326 48.363 48.399 48.436 48.473 11801190 48.473 48.509 48.546 48.582 48.619 48.656 48.692 48.729 48.765 48.802 48.838 1190

1200 48.838 48.875 48.911 48.948 48.984 49.021 49.057 49.093 49.130 49.166 49.202 12001210 49.202 49.239 49.275 49.311 49.348 49.384 49.420 49.456 49.493 49.529 49.565 12101220 49.565 49.601 49.637 49.674 49.710 49.746 49.782 49.818 49.854 49.890 49.926 12201230 49.926 49.962 49.998 50.034 50.070 50.106 50.142 50.178 50.214 50.250 50.286 12301240 50.286 50.322 50.358 50.393 50.429 50.465 50.501 50.537 50.572 50.608 50.644 1240

1250 50.644 50.680 50.715 50.751 50.787 50.822 50.858 50.894 50.929 50.965 51.000 12501260 51.000 51.036 51.071 51.107 51.142 51.178 51.213 51.249 51.284 51.320 51.355 12601270 51.355 51.391 51.426 51.461 51.497 51.532 51.567 51.603 51.638 51.673 51.708 12701280 51.708 51.744 51.779 51.814 51.849 51.885 51.920 51.955 51.990 52.025 52.060 12801290 52.060 52.095 52.130 52.165 52.200 52.235 52.270 52.305 52.340 52.375 52.410 1290

1300 52.410 52.445 52.480 52.515 52.550 52.585 52.620 52.654 52.689 52.724 52.759 13001310 52.759 52.794 52.828 52.863 52.898 52.932 52.967 53.002 53.037 53.071 53.106 13101320 53.106 53.140 53.175 53.210 53.244 53.279 53.313 53.348 53.382 53.417 53.451 13201330 53.451 53.486 53.520 53.555 53.589 53.623 53.658 53.692 53.727 53.761 53.795 13301340 53.795 53.830 53.864 53.898 53.932 53.967 54.001 54.035 54.069 54.104 54.138 1340

1350 54.138 54.172 54.206 54.240 54.274 54.308 54.343 54.377 54.411 54.445 54.479 13501360 54.479 54.513 54.547 54.581 54.615 54.649 54.683 54.717 54.751 54.785 54.819 13601370 54.819 54.852 54.886 1370


MAXIMUM TEMPERATURE RANGEThermocouple Grade– 328 to 2282°F– 200 to 1250°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 2.2°C or 0.75% Above 0°C2.2°C or 2.0% Below 0°CSpecial: 1.1°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Clean Oxidizing and Inert; Limited Use inVacuum or Reducing; Wide TemperatureRange; Most Popular CalibrationTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°CKK

ThermocoupleGrade

Nickel-Chromiumvs.

Nickel-Aluminum

ExtensionGrade

+–

+–


Z-206

Z


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

-260 -9.835 -9.833 -9.831 -9.828 -9.825 -9.821 -9.817 -9.813 -9.808 -9.802 -9.797 -260-250 -9.797 -9.790 -9.784 -9.777 -9.770 -9.762 -9.754 -9.746 -9.737 -9.728 -9.718 -250

-240 -9.718 -9.709 -9.698 -9.688 -9.677 -9.666 -9.654 -9.642 -9.630 -9.617 -9.604 -240-230 -9.604 -9.591 -9.577 -9.563 -9.548 -9.534 -9.519 -9.503 -9.487 -9.471 -9.455 -230-220 -9.455 -9.438 -9.421 -9.404 -9.386 -9.368 -9.350 -9.331 -9.313 -9.293 -9.274 -220-210 -9.274 -9.254 -9.234 -9.214 -9.193 -9.172 -9.151 -9.129 -9.107 -9.085 -9.063 -210-200 -9.063 -9.040 -9.017 -8.994 -8.971 -8.947 -8.923 -8.899 -8.874 -8.850 -8.825 -200

-190 -8.825 -8.799 -8.774 -8.748 -8.722 -8.696 -8.669 -8.643 -8.616 -8.588 -8.561 -190-180 -8.561 -8.533 -8.505 -8.477 -8.449 -8.420 -8.391 -8.362 -8.333 -8.303 -8.273 -180-170 -8.273 -8.243 -8.213 -8.183 -8.152 -8.121 -8.090 -8.059 -8.027 -7.995 -7.963 -170-160 -7.963 -7.931 -7.899 -7.866 -7.833 -7.800 -7.767 -7.733 -7.700 -7.666 -7.632 -160-150 -7.632 -7.597 -7.563 -7.528 -7.493 -7.458 -7.423 -7.387 -7.351 -7.315 -7.279 -150

-140 -7.279 -7.243 -7.206 -7.170 -7.133 -7.096 -7.058 -7.021 -6.983 -6.945 -6.907 -140-130 -6.907 -6.869 -6.831 -6.792 -6.753 -6.714 -6.675 -6.636 -6.596 -6.556 -6.516 -130-120 -6.516 -6.476 -6.436 -6.396 -6.355 -6.314 -6.273 -6.232 -6.191 -6.149 -6.107 -120-110 -6.107 -6.065 -6.023 -5.981 -5.939 -5.896 -5.853 -5.810 -5.767 -5.724 -5.681 -110-100 -5.681 -5.637 -5.593 -5.549 -5.505 -5.461 -5.417 -5.372 -5.327 -5.282 -5.237 -100

-90 -5.237 -5.192 -5.147 -5.101 -5.055 -5.009 -4.963 -4.917 -4.871 -4.824 -4.777 -90-80 -4.777 -4.731 -4.684 -4.636 -4.589 -4.542 -4.494 -4.446 -4.398 -4.350 -4.302 -80-70 -4.302 -4.254 -4.205 -4.156 -4.107 -4.058 -4.009 -3.960 -3.911 -3.861 -3.811 -70-60 -3.811 -3.761 -3.711 -3.661 -3.611 -3.561 -3.510 -3.459 -3.408 -3.357 -3.306 -60-50 -3.306 -3.255 -3.204 -3.152 -3.100 -3.048 -2.996 -2.944 -2.892 -2.840 -2.787 -50

-40 -2.787 -2.735 -2.682 -2.629 -2.576 -2.523 -2.469 -2.416 -2.362 -2.309 -2.255 -40-30 -2.255 -2.201 -2.147 -2.093 -2.038 -1.984 -1.929 -1.874 -1.820 -1.765 -1.709 -30-20 -1.709 -1.654 -1.599 -1.543 -1.488 -1.432 -1.376 -1.320 -1.264 -1.208 -1.152 -20-10 -1.152 -1.095 -1.039 -0.982 -0.925 -0.868 -0.811 -0.754 -0.697 -0.639 -0.582 -10

0 -0.582 -0.524 -0.466 -0.408 -0.350 -0.292 -0.234 -0.176 -0.117 -0.059 0.000 0

0 0.000 0.059 0.118 0.176 0.235 0.294 0.354 0.413 0.472 0.532 0.591 010 0.591 0.651 0.711 0.770 0.830 0.890 0.950 1.010 1.071 1.131 1.192 1020 1.192 1.252 1.313 1.373 1.434 1.495 1.556 1.617 1.678 1.740 1.801 2030 1.801 1.862 1.924 1.986 2.047 2.109 2.171 2.233 2.295 2.357 2.420 3040 2.420 2.482 2.545 2.607 2.670 2.733 2.795 2.858 2.921 2.984 3.048 40

50 3.048 3.111 3.174 3.238 3.301 3.365 3.429 3.492 3.556 3.620 3.685 5060 3.685 3.749 3.813 3.877 3.942 4.006 4.071 4.136 4.200 4.265 4.330 6070 4.330 4.395 4.460 4.526 4.591 4.656 4.722 4.788 4.853 4.919 4.985 7080 4.985 5.051 5.117 5.183 5.249 5.315 5.382 5.448 5.514 5.581 5.648 8090 5.648 5.714 5.781 5.848 5.915 5.982 6.049 6.117 6.184 6.251 6.319 90

100 6.319 6.386 6.454 6.522 6.590 6.658 6.725 6.794 6.862 6.930 6.998 100110 6.998 7.066 7.135 7.203 7.272 7.341 7.409 7.478 7.547 7.616 7.685 110120 7.685 7.754 7.823 7.892 7.962 8.031 8.101 8.170 8.240 8.309 8.379 120130 8.379 8.449 8.519 8.589 8.659 8.729 8.799 8.869 8.940 9.010 9.081 130140 9.081 9.151 9.222 9.292 9.363 9.434 9.505 9.576 9.647 9.718 9.789 140

150 9.789 9.860 9.931 10.003 10.074 10.145 10.217 10.288 10.360 10.432 10.503 150160 10.503 10.575 10.647 10.719 10.791 10.863 10.935 11.007 11.080 11.152 11.224 160170 11.224 11.297 11.369 11.442 11.514 11.587 11.660 11.733 11.805 11.878 11.951 170180 11.951 12.024 12.097 12.170 12.243 12.317 12.390 12.463 12.537 12.610 12.684 180190 12.684 12.757 12.831 12.904 12.978 13.052 13.126 13.199 13.273 13.347 13.421 190

200 13.421 13.495 13.569 13.644 13.718 13.792 13.866 13.941 14.015 14.090 14.164 200210 14.164 14.239 14.313 14.388 14.463 14.537 14.612 14.687 14.762 14.837 14.912 210220 14.912 14.987 15.062 15.137 15.212 15.287 15.362 15.438 15.513 15.588 15.664 220230 15.664 15.739 15.815 15.890 15.966 16.041 16.117 16.193 16.269 16.344 16.420 230240 16.420 16.496 16.572 16.648 16.724 16.800 16.876 16.952 17.028 17.104 17.181 240

250 17.181 17.257 17.333 17.409 17.486 17.562 17.639 17.715 17.792 17.868 17.945 250260 17.945 18.021 18.098 18.175 18.252 18.328 18.405 18.482 18.559 18.636 18.713 260270 18.713 18.790 18.867 18.944 19.021 19.098 19.175 19.252 19.330 19.407 19.484 270280 19.484 19.561 19.639 19.716 19.794 19.871 19.948 20.026 20.103 20.181 20.259 280290 20.259 20.336 20.414 20.492 20.569 20.647 20.725 20.803 20.880 20.958 21.036 290

300 21.036 21.114 21.192 21.270 21.348 21.426 21.504 21.582 21.660 21.739 21.817 300310 21.817 21.895 21.973 22.051 22.130 22.208 22.286 22.365 22.443 22.522 22.600 310320 22.600 22.678 22.757 22.835 22.914 22.993 23.071 23.150 23.228 23.307 23.386 320330 23.386 23.464 23.543 23.622 23.701 23.780 23.858 23.937 24.016 24.095 24.174 330340 24.174 24.253 24.332 24.411 24.490 24.569 24.648 24.727 24.806 24.885 24.964 340

350 24.964 25.044 25.123 25.202 25.281 25.360 25.440 25.519 25.598 25.678 25.757 350360 25.757 25.836 25.916 25.995 26.075 26.154 26.233 26.313 26.392 26.472 26.552 360370 26.552 26.631 26.711 26.790 26.870 26.950 27.029 27.109 27.189 27.268 27.348 370380 27.348 27.428 27.507 27.587 27.667 27.747 27.827 27.907 27.986 28.066 28.146 380390 28.146 28.226 28.306 28.386 28.466 28.546 28.626 28.706 28.786 28.866 28.946 390

400 28.946 29.026 29.106 29.186 29.266 29.346 29.427 29.507 29.587 29.667 29.747 400410 29.747 29.827 29.908 29.988 30.068 30.148 30.229 30.309 30.389 30.470 30.550 410420 30.550 30.630 30.711 30.791 30.871 30.952 31.032 31.112 31.193 31.273 31.354 420430 31.354 31.434 31.515 31.595 31.676 31.756 31.837 31.917 31.998 32.078 32.159 430440 32.159 32.239 32.320 32.400 32.481 32.562 32.642 32.723 32.803 32.884 32.965 440

450 32.965 33.045 33.126 33.207 33.287 33.368 33.449 33.529 33.610 33.691 33.772 450460 33.772 33.852 33.933 34.014 34.095 34.175 34.256 34.337 34.418 34.498 34.579 460470 34.579 34.660 34.741 34.822 34.902 34.983 35.064 35.145 35.226 35.307 35.387 470480 35.387 35.468 35.549 35.630 35.711 35.792 35.873 35.954 36.034 36.115 36.196 480490 36.196 36.277 36.358 36.439 36.520 36.601 36.682 36.763 36.843 36.924 37.005 490

500 37.005 37.086 37.167 37.248 37.329 37.410 37.491 37.572 37.653 37.734 37.815 500510 37.815 37.896 37.977 38.058 38.139 38.220 38.300 38.381 38.462 38.543 38.624 510520 38.624 38.705 38.786 38.867 38.948 39.029 39.110 39.191 39.272 39.353 39.434 520530 39.434 39.515 39.596 39.677 39.758 39.839 39.920 40.001 40.082 40.163 40.243 530540 40.243 40.324 40.405 40.486 40.567 40.648 40.729 40.810 40.891 40.972 41.053 540

550 41.053 41.134 41.215 41.296 41.377 41.457 41.538 41.619 41.700 41.781 41.862 550560 41.862 41.943 42.024 42.105 42.185 42.266 42.347 42.428 42.509 42.590 42.671 560570 42.671 42.751 42.832 42.913 42.994 43.075 43.156 43.236 43.317 43.398 43.479 570580 43.479 43.560 43.640 43.721 43.802 43.883 43.963 44.044 44.125 44.206 44.286 580590 44.286 44.367 44.448 44.529 44.609 44.690 44.771 44.851 44.932 45.013 45.093 590

600 45.093 45.174 45.255 45.335 45.416 45.497 45.577 45.658 45.738 45.819 45.900 600610 45.900 45.980 46.061 46.141 46.222 46.302 46.383 46.463 46.544 46.624 46.705 610620 46.705 46.785 46.866 46.946 47.027 47.107 47.188 47.268 47.349 47.429 47.509 620630 47.509 47.590 47.670 47.751 47.831 47.911 47.992 48.072 48.152 48.233 48.313 630640 48.313 48.393 48.474 48.554 48.634 48.715 48.795 48.875 48.955 49.035 49.116 640

650 49.116 49.196 49.276 49.356 49.436 49.517 49.597 49.677 49.757 49.837 49.917 650660 49.917 49.997 50.077 50.157 50.238 50.318 50.398 50.478 50.558 50.638 50.718 660670 50.718 50.798 50.878 50.958 51.038 51.118 51.197 51.277 51.357 51.437 51.517 670680 51.517 51.597 51.677 51.757 51.837 51.916 51.996 52.076 52.156 52.236 52.315 680690 52.315 52.395 52.475 52.555 52.634 52.714 52.794 52.873 52.953 53.033 53.112 690

700 53.112 53.192 53.272 53.351 53.431 53.510 53.590 53.670 53.749 53.829 53.908 700710 53.908 53.988 54.067 54.147 54.226 54.306 54.385 54.465 54.544 54.624 54.703 710720 54.703 54.782 54.862 54.941 55.021 55.100 55.179 55.259 55.338 55.417 55.497 720730 55.497 55.576 55.655 55.734 55.814 55.893 55.972 56.051 56.131 56.210 56.289 730740 56.289 56.368 56.447 56.526 56.606 56.685 56.764 56.843 56.922 57.001 57.080 740

750 57.080 57.159 57.238 57.317 57.396 57.475 57.554 57.633 57.712 57.791 57.870 750760 57.870 57.949 58.028 58.107 58.186 58.265 58.343 58.422 58.501 58.580 58.659 760770 58.659 58.738 58.816 58.895 58.974 59.053 59.131 59.210 59.289 59.367 59.446 770780 59.446 59.525 59.604 59.682 59.761 59.839 59.918 59.997 60.075 60.154 60.232 780790 60.232 60.311 60.390 60.468 60.547 60.625 60.704 60.782 60.860 60.939 61.017 790

800 61.017 61.096 61.174 61.253 61.331 61.409 61.488 61.566 61.644 61.723 61.801 800810 61.801 61.879 61.958 62.036 62.114 62.192 62.271 62.349 62.427 62.505 62.583 810820 62.583 62.662 62.740 62.818 62.896 62.974 63.052 63.130 63.208 63.286 63.364 820830 63.364 63.442 63.520 63.598 63.676 63.754 63.832 63.910 63.988 64.066 64.144 830840 64.144 64.222 64.300 64.377 64.455 64.533 64.611 64.689 64.766 64.844 64.922 840

850 64.922 65.000 65.077 65.155 65.233 65.310 65.388 65.465 65.543 65.621 65.698 850860 65.698 65.776 65.853 65.931 66.008 66.086 66.163 66.241 66.318 66.396 66.473 860870 66.473 66.550 66.628 66.705 66.782 66.860 66.937 67.014 67.092 67.169 67.246 870880 67.246 67.323 67.400 67.478 67.555 67.632 67.709 67.786 67.863 67.940 68.017 880890 68.017 68.094 68.171 68.248 68.325 68.402 68.479 68.556 68.633 68.710 68.787 890

900 68.787 68.863 68.940 69.017 69.094 69.171 69.247 69.324 69.401 69.477 69.554 900910 69.554 69.631 69.707 69.784 69.860 69.937 70.013 70.090 70.166 70.243 70.319 910920 70.319 70.396 70.472 70.548 70.625 70.701 70.777 70.854 70.930 71.006 71.082 920930 71.082 71.159 71.235 71.311 71.387 71.463 71.539 71.615 71.692 71.768 71.844 930940 71.844 71.920 71.996 72.072 72.147 72.223 72.299 72.375 72.451 72.527 72.603 940

950 72.603 72.678 72.754 72.830 72.906 72.981 73.057 73.133 73.208 73.284 73.360 950960 73.360 73.435 73.511 73.586 73.662 73.738 73.813 73.889 73.964 74.040 74.115 960970 74.115 74.190 74.266 74.341 74.417 74.492 74.567 74.643 74.718 74.793 74.869 970980 74.869 74.944 75.019 75.095 75.170 75.245 75.320 75.395 75.471 75.546 75.621 980990 75.621 75.696 75.771 75.847 75.922 75.997 76.072 76.147 76.223 76.298 76.373 990

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 328 to 1652°F– 200 to 900°CExtension Grade32 to 392°F0 to 200°C LIMITS OF ERROR(whichever is greater)Standard: 1.7°C or 0.5% Above 0°C1.7°C or 1.0% Below 0°CSpecial: 1.0°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Limited Use in Vacuum orReducing; Highest EMF Change per DegreeTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°C EE

°C -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

ThermocoupleGrade

Nickel-Chromiumvs.

Copper-Nickel

ExtensionGrade

+–

+–



Z-207


°C -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

-260 -6.258 -6.256 -6.255 -6.253 -6.251 -6.248 -6.245 -6.242 -6.239 -6.236 -6.232 -260-250 -6.232 -6.228 -6.223 -6.219 -6.214 -6.209 -6.204 -6.198 -6.193 -6.187 -6.180 -250

-240 -6.180 -6.174 -6.167 -6.160 -6.153 -6.146 -6.138 -6.130 -6.122 -6.114 -6.105 -240-230 -6.105 -6.096 -6.087 -6.078 -6.068 -6.059 -6.049 -6.038 -6.028 -6.017 -6.007 -230-220 -6.007 -5.996 -5.985 -5.973 -5.962 -5.950 -5.938 -5.926 -5.914 -5.901 -5.888 -220-210 -5.888 -5.876 -5.863 -5.850 -5.836 -5.823 -5.809 -5.795 -5.782 -5.767 -5.753 -210-200 -5.753 -5.739 -5.724 -5.710 -5.695 -5.680 -5.665 -5.650 -5.634 -5.619 -5.603 -200

-190 -5.603 -5.587 -5.571 -5.555 -5.539 -5.523 -5.506 -5.489 -5.473 -5.456 -5.439 -190-180 -5.439 -5.421 -5.404 -5.387 -5.369 -5.351 -5.334 -5.316 -5.297 -5.279 -5.261 -180-170 -5.261 -5.242 -5.224 -5.205 -5.186 -5.167 -5.148 -5.128 -5.109 -5.089 -5.070 -170-160 -5.070 -5.050 -5.030 -5.010 -4.989 -4.969 -4.949 -4.928 -4.907 -4.886 -4.865 -160-150 -4.865 -4.844 -4.823 -4.802 -4.780 -4.759 -4.737 -4.715 -4.693 -4.671 -4.648 -150

-140 -4.648 -4.626 -4.604 -4.581 -4.558 -4.535 -4.512 -4.489 -4.466 -4.443 -4.419 -140-130 -4.419 -4.395 -4.372 -4.348 -4.324 -4.300 -4.275 -4.251 -4.226 -4.202 -4.177 -130-120 -4.177 -4.152 -4.127 -4.102 -4.077 -4.052 -4.026 -4.000 -3.975 -3.949 -3.923 -120-110 -3.923 -3.897 -3.871 -3.844 -3.818 -3.791 -3.765 -3.738 -3.711 -3.684 -3.657 -110-100 -3.657 -3.629 -3.602 -3.574 -3.547 -3.519 -3.491 -3.463 -3.435 -3.407 -3.379 -100

-90 -3.379 -3.350 -3.322 -3.293 -3.264 -3.235 -3.206 -3.177 -3.148 -3.118 -3.089 -90-80 -3.089 -3.059 -3.030 -3.000 -2.970 -2.940 -2.910 -2.879 -2.849 -2.818 -2.788 -80-70 -2.788 -2.757 -2.726 -2.695 -2.664 -2.633 -2.602 -2.571 -2.539 -2.507 -2.476 -70-60 -2.476 -2.444 -2.412 -2.380 -2.348 -2.316 -2.283 -2.251 -2.218 -2.186 -2.153 -60-50 -2.153 -2.120 -2.087 -2.054 -2.021 -1.987 -1.954 -1.920 -1.887 -1.853 -1.819 -50

-40 -1.819 -1.785 -1.751 -1.717 -1.683 -1.648 -1.614 -1.579 -1.545 -1.510 -1.475 -40-30 -1.475 -1.440 -1.405 -1.370 -1.335 -1.299 -1.264 -1.228 -1.192 -1.157 -1.121 -30-20 -1.121 -1.085 -1.049 -1.013 -0.976 -0.940 -0.904 -0.867 -0.830 -0.794 -0.757 -20-10 -0.757 -0.720 -0.683 -0.646 -0.608 -0.571 -0.534 -0.496 -0.459 -0.421 -0.383 -10

0 -0.383 -0.345 -0.307 -0.269 -0.231 -0.193 -0.154 -0.116 -0.077 -0.039 0.000 0

0 0.000 0.039 0.078 0.117 0.156 0.195 0.234 0.273 0.312 0.352 0.391 010 0.391 0.431 0.470 0.510 0.549 0.589 0.629 0.669 0.709 0.749 0.790 1020 0.790 0.830 0.870 0.911 0.951 0.992 1.033 1.074 1.114 1.155 1.196 2030 1.196 1.238 1.279 1.320 1.362 1.403 1.445 1.486 1.528 1.570 1.612 3040 1.612 1.654 1.696 1.738 1.780 1.823 1.865 1.908 1.950 1.993 2.036 40

50 2.036 2.079 2.122 2.165 2.208 2.251 2.294 2.338 2.381 2.425 2.468 5060 2.468 2.512 2.556 2.600 2.643 2.687 2.732 2.776 2.820 2.864 2.909 6070 2.909 2.953 2.998 3.043 3.087 3.132 3.177 3.222 3.267 3.312 3.358 7080 3.358 3.403 3.448 3.494 3.539 3.585 3.631 3.677 3.722 3.768 3.814 8090 3.814 3.860 3.907 3.953 3.999 4.046 4.092 4.138 4.185 4.232 4.279 90

100 4.279 4.325 4.372 4.419 4.466 4.513 4.561 4.608 4.655 4.702 4.750 100110 4.750 4.798 4.845 4.893 4.941 4.988 5.036 5.084 5.132 5.180 5.228 110120 5.228 5.277 5.325 5.373 5.422 5.470 5.519 5.567 5.616 5.665 5.714 120130 5.714 5.763 5.812 5.861 5.910 5.959 6.008 6.057 6.107 6.156 6.206 130140 6.206 6.255 6.305 6.355 6.404 6.454 6.504 6.554 6.604 6.654 6.704 140

150 6.704 6.754 6.805 6.855 6.905 6.956 7.006 7.057 7.107 7.158 7.209 150160 7.209 7.260 7.310 7.361 7.412 7.463 7.515 7.566 7.617 7.668 7.720 160170 7.720 7.771 7.823 7.874 7.926 7.977 8.029 8.081 8.133 8.185 8.237 170180 8.237 8.289 8.341 8.393 8.445 8.497 8.550 8.602 8.654 8.707 8.759 180190 8.759 8.812 8.865 8.917 8.970 9.023 9.076 9.129 9.182 9.235 9.288 190

200 9.288 9.341 9.395 9.448 9.501 9.555 9.608 9.662 9.715 9.769 9.822 200210 9.822 9.876 9.930 9.984 10.038 10.092 10.146 10.200 10.254 10.308 10.362 210220 10.362 10.417 10.471 10.525 10.580 10.634 10.689 10.743 10.798 10.853 10.907 220230 10.907 10.962 11.017 11.072 11.127 11.182 11.237 11.292 11.347 11.403 11.458 230240 11.458 11.513 11.569 11.624 11.680 11.735 11.791 11.846 11.902 11.958 12.013 240

250 12.013 12.069 12.125 12.181 12.237 12.293 12.349 12.405 12.461 12.518 12.574 250260 12.574 12.630 12.687 12.743 12.799 12.856 12.912 12.969 13.026 13.082 13.139 260270 13.139 13.196 13.253 13.310 13.366 13.423 13.480 13.537 13.595 13.652 13.709 270280 13.709 13.766 13.823 13.881 13.938 13.995 14.053 14.110 14.168 14.226 14.283 280290 14.283 14.341 14.399 14.456 14.514 14.572 14.630 14.688 14.746 14.804 14.862 290

300 14.862 14.920 14.978 15.036 15.095 15.153 15.211 15.270 15.328 15.386 15.445 300310 15.445 15.503 15.562 15.621 15.679 15.738 15.797 15.856 15.914 15.973 16.032 310320 16.032 16.091 16.150 16.209 16.268 16.327 16.387 16.446 16.505 16.564 16.624 320330 16.624 16.683 16.742 16.802 16.861 16.921 16.980 17.040 17.100 17.159 17.219 330340 17.219 17.279 17.339 17.399 17.458 17.518 17.578 17.638 17.698 17.759 17.819 340

350 17.819 17.879 17.939 17.999 18.060 18.120 18.180 18.241 18.301 18.362 18.422 350360 18.422 18.483 18.543 18.604 18.665 18.725 18.786 18.847 18.908 18.969 19.030 360370 19.030 19.091 19.152 19.213 19.274 19.335 19.396 19.457 19.518 19.579 19.641 370380 19.641 19.702 19.763 19.825 19.886 19.947 20.009 20.070 20.132 20.193 20.255 380390 20.255 20.317 20.378 20.440 20.502 20.563 20.625 20.687 20.748 20.810 20.872 390

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 328 to 662°F– 200 to 350°CExtension Grade– 76 to 212°F– 60 to 100°CLIMITS OF ERROR(whichever is greater)Standard: 1.0°C or 0.75% Above 0°C 1.0°C or 1.5% Below 0°CSpecial: 0.5°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Mild Oxidizing, Reducing Vacuum or Inert; GoodWhere Moisture Is Present; Low Temperatureand Cryogenic ApplicationsTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°CTT

ThermocoupleGrade

Coppervs.

Copper-Nickel

ExtensionGrade

+–

+–



Z-208

Z


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

-40 -0.236 -0.232 -0.228 -0.224 -0.219 -0.215 -0.211 -0.207 -0.203 -0.199 -0.194 -40-30 -0.194 -0.190 -0.186 -0.181 -0.177 -0.173 -0.168 -0.164 -0.159 -0.155 -0.150 -30-20 -0.150 -0.146 -0.141 -0.136 -0.132 -0.127 -0.122 -0.117 -0.113 -0.108 -0.103 -20-10 -0.103 -0.098 -0.093 -0.088 -0.083 -0.078 -0.073 -0.068 -0.063 -0.058 -0.053 -10

0 -0.053 -0.048 -0.042 -0.037 -0.032 -0.027 -0.021 -0.016 -0.011 -0.005 0.000 0

0 0.000 0.005 0.011 0.016 0.022 0.027 0.033 0.038 0.044 0.050 0.055 010 0.055 0.061 0.067 0.072 0.078 0.084 0.090 0.095 0.101 0.107 0.113 1020 0.113 0.119 0.125 0.131 0.137 0.143 0.149 0.155 0.161 0.167 0.173 2030 0.173 0.179 0.185 0.191 0.197 0.204 0.210 0.216 0.222 0.229 0.235 3040 0.235 0.241 0.248 0.254 0.260 0.267 0.273 0.280 0.286 0.292 0.299 40

50 0.299 0.305 0.312 0.319 0.325 0.332 0.338 0.345 0.352 0.358 0.365 5060 0.365 0.372 0.378 0.385 0.392 0.399 0.405 0.412 0.419 0.426 0.433 6070 0.433 0.440 0.446 0.453 0.460 0.467 0.474 0.481 0.488 0.495 0.502 7080 0.502 0.509 0.516 0.523 0.530 0.538 0.545 0.552 0.559 0.566 0.573 8090 0.573 0.580 0.588 0.595 0.602 0.609 0.617 0.624 0.631 0.639 0.646 90

100 0.646 0.653 0.661 0.668 0.675 0.683 0.690 0.698 0.705 0.713 0.720 100110 0.720 0.727 0.735 0.743 0.750 0.758 0.765 0.773 0.780 0.788 0.795 110120 0.795 0.803 0.811 0.818 0.826 0.834 0.841 0.849 0.857 0.865 0.872 120130 0.872 0.880 0.888 0.896 0.903 0.911 0.919 0.927 0.935 0.942 0.950 130140 0.950 0.958 0.966 0.974 0.982 0.990 0.998 1.006 1.013 1.021 1.029 140

150 1.029 1.037 1.045 1.053 1.061 1.069 1.077 1.085 1.094 1.102 1.110 150160 1.110 1.118 1.126 1.134 1.142 1.150 1.158 1.167 1.175 1.183 1.191 160170 1.191 1.199 1.207 1.216 1.224 1.232 1.240 1.249 1.257 1.265 1.273 170180 1.273 1.282 1.290 1.298 1.307 1.315 1.323 1.332 1.340 1.348 1.357 180190 1.357 1.365 1.373 1.382 1.390 1.399 1.407 1.415 1.424 1.432 1.441 190

200 1.441 1.449 1.458 1.466 1.475 1.483 1.492 1.500 1.509 1.517 1.526 200210 1.526 1.534 1.543 1.551 1.560 1.569 1.577 1.586 1.594 1.603 1.612 210220 1.612 1.620 1.629 1.638 1.646 1.655 1.663 1.672 1.681 1.690 1.698 220230 1.698 1.707 1.716 1.724 1.733 1.742 1.751 1.759 1.768 1.777 1.786 230240 1.786 1.794 1.803 1.812 1.821 1.829 1.838 1.847 1.856 1.865 1.874 240

250 1.874 1.882 1.891 1.900 1.909 1.918 1.927 1.936 1.944 1.953 1.962 250260 1.962 1.971 1.980 1.989 1.998 2.007 2.016 2.025 2.034 2.043 2.052 260270 2.052 2.061 2.070 2.078 2.087 2.096 2.105 2.114 2.123 2.132 2.141 270280 2.141 2.151 2.160 2.169 2.178 2.187 2.196 2.205 2.214 2.223 2.232 280290 2.232 2.241 2.250 2.259 2.268 2.277 2.287 2.296 2.305 2.314 2.323 290

300 2.323 2.332 2.341 2.350 2.360 2.369 2.378 2.387 2.396 2.405 2.415 300310 2.415 2.424 2.433 2.442 2.451 2.461 2.470 2.479 2.488 2.497 2.507 310320 2.507 2.516 2.525 2.534 2.544 2.553 2.562 2.571 2.581 2.590 2.599 320330 2.599 2.609 2.618 2.627 2.636 2.646 2.655 2.664 2.674 2.683 2.692 330340 2.692 2.702 2.711 2.720 2.730 2.739 2.748 2.758 2.767 2.776 2.786 340

350 2.786 2.795 2.805 2.814 2.823 2.833 2.842 2.851 2.861 2.870 2.880 350360 2.880 2.889 2.899 2.908 2.917 2.927 2.936 2.946 2.955 2.965 2.974 360370 2.974 2.983 2.993 3.002 3.012 3.021 3.031 3.040 3.050 3.059 3.069 370380 3.069 3.078 3.088 3.097 3.107 3.116 3.126 3.135 3.145 3.154 3.164 380390 3.164 3.173 3.183 3.192 3.202 3.212 3.221 3.231 3.240 3.250 3.259 390

400 3.259 3.269 3.279 3.288 3.298 3.307 3.317 3.326 3.336 3.346 3.355 400410 3.355 3.365 3.374 3.384 3.394 3.403 3.413 3.423 3.432 3.442 3.451 410420 3.451 3.461 3.471 3.480 3.490 3.500 3.509 3.519 3.529 3.538 3.548 420430 3.548 3.558 3.567 3.577 3.587 3.596 3.606 3.616 3.626 3.635 3.645 430440 3.645 3.655 3.664 3.674 3.684 3.694 3.703 3.713 3.723 3.732 3.742 440

450 3.742 3.752 3.762 3.771 3.781 3.791 3.801 3.810 3.820 3.830 3.840 450460 3.840 3.850 3.859 3.869 3.879 3.889 3.898 3.908 3.918 3.928 3.938 460470 3.938 3.947 3.957 3.967 3.977 3.987 3.997 4.006 4.016 4.026 4.036 470480 4.036 4.046 4.056 4.065 4.075 4.085 4.095 4.105 4.115 4.125 4.134 480490 4.134 4.144 4.154 4.164 4.174 4.184 4.194 4.204 4.213 4.223 4.233 490

500 4.233 4.243 4.253 4.263 4.273 4.283 4.293 4.303 4.313 4.323 4.332 500510 4.332 4.342 4.352 4.362 4.372 4.382 4.392 4.402 4.412 4.422 4.432 510520 4.432 4.442 4.452 4.462 4.472 4.482 4.492 4.502 4.512 4.522 4.532 520530 4.532 4.542 4.552 4.562 4.572 4.582 4.592 4.602 4.612 4.622 4.632 530540 4.632 4.642 4.652 4.662 4.672 4.682 4.692 4.702 4.712 4.722 4.732 540

550 4.732 4.742 4.752 4.762 4.772 4.782 4.793 4.803 4.813 4.823 4.833 550560 4.833 4.843 4.853 4.863 4.873 4.883 4.893 4.904 4.914 4.924 4.934 560570 4.934 4.944 4.954 4.964 4.974 4.984 4.995 5.005 5.015 5.025 5.035 570580 5.035 5.045 5.055 5.066 5.076 5.086 5.096 5.106 5.116 5.127 5.137 580590 5.137 5.147 5.157 5.167 5.178 5.188 5.198 5.208 5.218 5.228 5.239 590

600 5.239 5.249 5.259 5.269 5.280 5.290 5.300 5.310 5.320 5.331 5.341 600610 5.341 5.351 5.361 5.372 5.382 5.392 5.402 5.413 5.423 5.433 5.443 610620 5.443 5.454 5.464 5.474 5.485 5.495 5.505 5.515 5.526 5.536 5.546 620630 5.546 5.557 5.567 5.577 5.588 5.598 5.608 5.618 5.629 5.639 5.649 630640 5.649 5.660 5.670 5.680 5.691 5.701 5.712 5.722 5.732 5.743 5.753 640

650 5.753 5.763 5.774 5.784 5.794 5.805 5.815 5.826 5.836 5.846 5.857 650660 5.857 5.867 5.878 5.888 5.898 5.909 5.919 5.930 5.940 5.950 5.961 660670 5.961 5.971 5.982 5.992 6.003 6.013 6.024 6.034 6.044 6.055 6.065 670680 6.065 6.076 6.086 6.097 6.107 6.118 6.128 6.139 6.149 6.160 6.170 680690 6.170 6.181 6.191 6.202 6.212 6.223 6.233 6.244 6.254 6.265 6.275 690

700 6.275 6.286 6.296 6.307 6.317 6.328 6.338 6.349 6.360 6.370 6.381 700710 6.381 6.391 6.402 6.412 6.423 6.434 6.444 6.455 6.465 6.476 6.486 710720 6.486 6.497 6.508 6.518 6.529 6.539 6.550 6.561 6.571 6.582 6.593 720730 6.593 6.603 6.614 6.624 6.635 6.646 6.656 6.667 6.678 6.688 6.699 730740 6.699 6.710 6.720 6.731 6.742 6.752 6.763 6.774 6.784 6.795 6.806 740

750 6.806 6.817 6.827 6.838 6.849 6.859 6.870 6.881 6.892 6.902 6.913 750760 6.913 6.924 6.934 6.945 6.956 6.967 6.977 6.988 6.999 7.010 7.020 760770 7.020 7.031 7.042 7.053 7.064 7.074 7.085 7.096 7.107 7.117 7.128 770780 7.128 7.139 7.150 7.161 7.172 7.182 7.193 7.204 7.215 7.226 7.236 780790 7.236 7.247 7.258 7.269 7.280 7.291 7.302 7.312 7.323 7.334 7.345 790

800 7.345 7.356 7.367 7.378 7.388 7.399 7.410 7.421 7.432 7.443 7.454 800810 7.454 7.465 7.476 7.487 7.497 7.508 7.519 7.530 7.541 7.552 7.563 810820 7.563 7.574 7.585 7.596 7.607 7.618 7.629 7.640 7.651 7.662 7.673 820830 7.673 7.684 7.695 7.706 7.717 7.728 7.739 7.750 7.761 7.772 7.783 830840 7.783 7.794 7.805 7.816 7.827 7.838 7.849 7.860 7.871 7.882 7.893 840

850 7.893 7.904 7.915 7.926 7.937 7.948 7.959 7.970 7.981 7.992 8.003 850860 8.003 8.014 8.026 8.037 8.048 8.059 8.070 8.081 8.092 8.103 8.114 860870 8.114 8.125 8.137 8.148 8.159 8.170 8.181 8.192 8.203 8.214 8.226 870880 8.226 8.237 8.248 8.259 8.270 8.281 8.293 8.304 8.315 8.326 8.337 880890 8.337 8.348 8.360 8.371 8.382 8.393 8.404 8.416 8.427 8.438 8.449 890

900 8.449 8.460 8.472 8.483 8.494 8.505 8.517 8.528 8.539 8.550 8.562 900910 8.562 8.573 8.584 8.595 8.607 8.618 8.629 8.640 8.652 8.663 8.674 910920 8.674 8.685 8.697 8.708 8.719 8.731 8.742 8.753 8.765 8.776 8.787 920930 8.787 8.798 8.810 8.821 8.832 8.844 8.855 8.866 8.878 8.889 8.900 930940 8.900 8.912 8.923 8.935 8.946 8.957 8.969 8.980 8.991 9.003 9.014 940

950 9.014 9.025 9.037 9.048 9.060 9.071 9.082 9.094 9.105 9.117 9.128 950960 9.128 9.139 9.151 9.162 9.174 9.185 9.197 9.208 9.219 9.231 9.242 960970 9.242 9.254 9.265 9.277 9.288 9.300 9.311 9.323 9.334 9.345 9.357 970980 9.357 9.368 9.380 9.391 9.403 9.414 9.426 9.437 9.449 9.460 9.472 980990 9.472 9.483 9.495 9.506 9.518 9.529 9.541 9.552 9.564 9.576 9.587 990

1000 9.587 9.599 9.610 9.622 9.633 9.645 9.656 9.668 9.680 9.691 9.703 10001010 9.703 9.714 9.726 9.737 9.749 9.761 9.772 9.784 9.795 9.807 9.819 10101020 9.819 9.830 9.842 9.853 9.865 9.877 9.888 9.900 9.911 9.923 9.935 10201030 9.935 9.946 9.958 9.970 9.981 9.993 10.005 10.016 10.028 10.040 10.051 10301040 10.051 10.063 10.075 10.086 10.098 10.110 10.121 10.133 10.145 10.156 10.168 1040

1050 10.168 10.180 10.191 10.203 10.215 10.227 10.238 10.250 10.262 10.273 10.285 10501060 10.285 10.297 10.309 10.320 10.332 10.344 10.356 10.367 10.379 10.391 10.403 10601070 10.403 10.414 10.426 10.438 10.450 10.461 10.473 10.485 10.497 10.509 10.520 10701080 10.520 10.532 10.544 10.556 10.567 10.579 10.591 10.603 10.615 10.626 10.638 10801090 10.638 10.650 10.662 10.674 10.686 10.697 10.709 10.721 10.733 10.745 10.757 1090

1100 10.757 10.768 10.780 10.792 10.804 10.816 10.828 10.839 10.851 10.863 10.875 11001110 10.875 10.887 10.899 10.911 10.922 10.934 10.946 10.958 10.970 10.982 10.994 11101120 10.994 11.006 11.017 11.029 11.041 11.053 11.065 11.077 11.089 11.101 11.113 11201130 11.113 11.125 11.136 11.148 11.160 11.172 11.184 11.196 11.208 11.220 11.232 11301140 11.232 11.244 11.256 11.268 11.280 11.291 11.303 11.315 11.327 11.339 11.351 1140

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 2642°F0 to 1450°CExtension Grade32 to 300°F0 to 150°CLIMITS OF ERROR(whichever is greater)Standard: 1.5°C or 0.25%Special: 0.6°C or 0.1%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High TemperatureTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°C SS

°C -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

ThermocoupleGrade

Platinum-10% Rhodiumvs.

Platinum

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-209


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

1150 11.351 11.363 11.375 11.387 11.399 11.411 11.423 11.435 11.447 11.459 11.471 11501160 11.471 11.483 11.495 11.507 11.519 11.531 11.542 11.554 11.566 11.578 11.590 11601170 11.590 11.602 11.614 11.626 11.638 11.650 11.662 11.674 11.686 11.698 11.710 11701180 11.710 11.722 11.734 11.746 11.758 11.770 11.782 11.794 11.806 11.818 11.830 11801190 11.830 11.842 11.854 11.866 11.878 11.890 11.902 11.914 11.926 11.939 11.951 1190

1200 11.951 11.963 11.975 11.987 11.999 12.011 12.023 12.035 12.047 12.059 12.071 12001210 12.071 12.083 12.095 12.107 12.119 12.131 12.143 12.155 12.167 12.179 12.191 12101220 12.191 12.203 12.216 12.228 12.240 12.252 12.264 12.276 12.288 12.300 12.312 12201230 12.312 12.324 12.336 12.348 12.360 12.372 12.384 12.397 12.409 12.421 12.433 12301240 12.433 12.445 12.457 12.469 12.481 12.493 12.505 12.517 12.529 12.542 12.554 1240

1250 12.554 12.566 12.578 12.590 12.602 12.614 12.626 12.638 12.650 12.662 12.675 12501260 12.675 12.687 12.699 12.711 12.723 12.735 12.747 12.759 12.771 12.783 12.796 12601270 12.796 12.808 12.820 12.832 12.844 12.856 12.868 12.880 12.892 12.905 12.917 12701280 12.917 12.929 12.941 12.953 12.965 12.977 12.989 13.001 13.014 13.026 13.038 12801290 13.038 13.050 13.062 13.074 13.086 13.098 13.111 13.123 13.135 13.147 13.159 1290

1300 13.159 13.171 13.183 13.195 13.208 13.220 13.232 13.244 13.256 13.268 13.280 13001310 13.280 13.292 13.305 13.317 13.329 13.341 13.353 13.365 13.377 13.390 13.402 13101320 13.402 13.414 13.426 13.438 13.450 13.462 13.474 13.487 13.499 13.511 13.523 13201330 13.523 13.535 13.547 13.559 13.572 13.584 13.596 13.608 13.620 13.632 13.644 13301340 13.644 13.657 13.669 13.681 13.693 13.705 13.717 13.729 13.742 13.754 13.766 1340

1350 13.766 13.778 13.790 13.802 13.814 13.826 13.839 13.851 13.863 13.875 13.887 13501360 13.887 13.899 13.911 13.924 13.936 13.948 13.960 13.972 13.984 13.996 14.009 13601370 14.009 14.021 14.033 14.045 14.057 14.069 14.081 14.094 14.106 14.118 14.130 13701380 14.130 14.142 14.154 14.166 14.178 14.191 14.203 14.215 14.227 14.239 14.251 13801390 14.251 14.263 14.276 14.288 14.300 14.312 14.324 14.336 14.348 14.360 14.373 1390

1400 14.373 14.385 14.397 14.409 14.421 14.433 14.445 14.457 14.470 14.482 14.494 14001410 14.494 14.506 14.518 14.530 14.542 14.554 14.567 14.579 14.591 14.603 14.615 14101420 14.615 14.627 14.639 14.651 14.664 14.676 14.688 14.700 14.712 14.724 14.736 14201430 14.736 14.748 14.760 14.773 14.785 14.797 14.809 14.821 14.833 14.845 14.857 14301440 14.857 14.869 14.881 14.894 14.906 14.918 14.930 14.942 14.954 14.966 14.978 1440

1450 14.978 14.990 15.002 15.015 15.027 15.039 15.051 15.063 15.075 15.087 15.099 14501460 15.099 15.111 15.123 15.135 15.148 15.160 15.172 15.184 15.196 15.208 15.220 14601470 15.220 15.232 15.244 15.256 15.268 15.280 15.292 15.304 15.317 15.329 15.341 14701480 15.341 15.353 15.365 15.377 15.389 15.401 15.413 15.425 15.437 15.449 15.461 14801490 15.461 15.473 15.485 15.497 15.509 15.521 15.534 15.546 15.558 15.570 15.582 1490

1500 15.582 15.594 15.606 15.618 15.630 15.642 15.654 15.666 15.678 15.690 15.702 15001510 15.702 15.714 15.726 15.738 15.750 15.762 15.774 15.786 15.798 15.810 15.822 15101520 15.822 15.834 15.846 15.858 15.870 15.882 15.894 15.906 15.918 15.930 15.942 15201530 15.942 15.954 15.966 15.978 15.990 16.002 16.014 16.026 16.038 16.050 16.062 15301540 16.062 16.074 16.086 16.098 16.110 16.122 16.134 16.146 16.158 16.170 16.182 1540

1550 16.182 16.194 16.205 16.217 16.229 16.241 16.253 16.265 16.277 16.289 16.301 15501560 16.301 16.313 16.325 16.337 16.349 16.361 16.373 16.385 16.396 16.408 16.420 15601570 16.420 16.432 16.444 16.456 16.468 16.480 16.492 16.504 16.516 16.527 16.539 15701580 16.539 16.551 16.563 16.575 16.587 16.599 16.611 16.623 16.634 16.646 16.658 15801590 16.658 16.670 16.682 16.694 16.706 16.718 16.729 16.741 16.753 16.765 16.777 1590

1600 16.777 16.789 16.801 16.812 16.824 16.836 16.848 16.860 16.872 16.883 16.895 16001610 16.895 16.907 16.919 16.931 16.943 16.954 16.966 16.978 16.990 17.002 17.013 16101620 17.013 17.025 17.037 17.049 17.061 17.072 17.084 17.096 17.108 17.120 17.131 16201630 17.131 17.143 17.155 17.167 17.178 17.190 17.202 17.214 17.225 17.237 17.249 16301640 17.249 17.261 17.272 17.284 17.296 17.308 17.319 17.331 17.343 17.355 17.366 1640

1650 17.366 17.378 17.390 17.401 17.413 17.425 17.437 17.448 17.460 17.472 17.483 16501660 17.483 17.495 17.507 17.518 17.530 17.542 17.553 17.565 17.577 17.588 17.600 16601670 17.600 17.612 17.623 17.635 17.647 17.658 17.670 17.682 17.693 17.705 17.717 16701680 17.717 17.728 17.740 17.751 17.763 17.775 17.786 17.798 17.809 17.821 17.832 16801690 17.832 17.844 17.855 17.867 17.878 17.890 17.901 17.913 17.924 17.936 17.947 1690

1700 17.947 17.959 17.970 17.982 17.993 18.004 18.016 18.027 18.039 18.050 18.061 17001710 18.061 18.073 18.084 18.095 18.107 18.118 18.129 18.140 18.152 18.163 18.174 17101720 18.174 18.185 18.196 18.208 18.219 18.230 18.241 18.252 18.263 18.274 18.285 17201730 18.285 18.297 18.308 18.319 18.330 18.341 18.352 18.362 18.373 18.384 18.395 17301740 18.395 18.406 18.417 18.428 18.439 18.449 18.460 18.471 18.482 18.493 18.503 1740

1750 18.503 18.514 18.525 18.535 18.546 18.557 18.567 18.578 18.588 18.599 18.609 17501760 18.609 18.620 18.630 18.641 18.651 18.661 18.672 18.682 18.693 1760

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 2642°F0 to 1450°CExtension Grade32 to 300°F0 to 150°CLIMITS OF ERROR(whichever is greater)Standard: 1.5°C or 0.25%Special: 0.6°C or 0.1%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High TemperatureTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°CSS

ThermocoupleGrade


Platinum

ExtensionGrade

+–

+–


NONEESTABLISHED

+–


Z-210

Z


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

-40 -0.226 -0.223 -0.219 -0.215 -0.211 -0.208 -0.204 -0.200 -0.196 -0.192 -0.188 -40-30 -0.188 -0.184 -0.180 -0.175 -0.171 -0.167 -0.163 -0.158 -0.154 -0.150 -0.145 -30-20 -0.145 -0.141 -0.137 -0.132 -0.128 -0.123 -0.119 -0.114 -0.109 -0.105 -0.100 -20-10 -0.100 -0.095 -0.091 -0.086 -0.081 -0.076 -0.071 -0.066 -0.061 -0.056 -0.051 -10

0 -0.051 -0.046 -0.041 -0.036 -0.031 -0.026 -0.021 -0.016 -0.011 -0.005 0.000 0

0 0.000 0.005 0.011 0.016 0.021 0.027 0.032 0.038 0.043 0.049 0.054 010 0.054 0.060 0.065 0.071 0.077 0.082 0.088 0.094 0.100 0.105 0.111 1020 0.111 0.117 0.123 0.129 0.135 0.141 0.147 0.153 0.159 0.165 0.171 2030 0.171 0.177 0.183 0.189 0.195 0.201 0.207 0.214 0.220 0.226 0.232 3040 0.232 0.239 0.245 0.251 0.258 0.264 0.271 0.277 0.284 0.290 0.296 40

50 0.296 0.303 0.310 0.316 0.323 0.329 0.336 0.343 0.349 0.356 0.363 5060 0.363 0.369 0.376 0.383 0.390 0.397 0.403 0.410 0.417 0.424 0.431 6070 0.431 0.438 0.445 0.452 0.459 0.466 0.473 0.480 0.487 0.494 0.501 7080 0.501 0.508 0.516 0.523 0.530 0.537 0.544 0.552 0.559 0.566 0.573 8090 0.573 0.581 0.588 0.595 0.603 0.610 0.618 0.625 0.632 0.640 0.647 90

100 0.647 0.655 0.662 0.670 0.677 0.685 0.693 0.700 0.708 0.715 0.723 100110 0.723 0.731 0.738 0.746 0.754 0.761 0.769 0.777 0.785 0.792 0.800 110120 0.800 0.808 0.816 0.824 0.832 0.839 0.847 0.855 0.863 0.871 0.879 120130 0.879 0.887 0.895 0.903 0.911 0.919 0.927 0.935 0.943 0.951 0.959 130140 0.959 0.967 0.976 0.984 0.992 1.000 1.008 1.016 1.025 1.033 1.041 140

150 1.041 1.049 1.058 1.066 1.074 1.082 1.091 1.099 1.107 1.116 1.124 150160 1.124 1.132 1.141 1.149 1.158 1.166 1.175 1.183 1.191 1.200 1.208 160170 1.208 1.217 1.225 1.234 1.242 1.251 1.260 1.268 1.277 1.285 1.294 170180 1.294 1.303 1.311 1.320 1.329 1.337 1.346 1.355 1.363 1.372 1.381 180190 1.381 1.389 1.398 1.407 1.416 1.425 1.433 1.442 1.451 1.460 1.469 190

200 1.469 1.477 1.486 1.495 1.504 1.513 1.522 1.531 1.540 1.549 1.558 200210 1.558 1.567 1.575 1.584 1.593 1.602 1.611 1.620 1.629 1.639 1.648 210220 1.648 1.657 1.666 1.675 1.684 1.693 1.702 1.711 1.720 1.729 1.739 220230 1.739 1.748 1.757 1.766 1.775 1.784 1.794 1.803 1.812 1.821 1.831 230240 1.831 1.840 1.849 1.858 1.868 1.877 1.886 1.895 1.905 1.914 1.923 240

250 1.923 1.933 1.942 1.951 1.961 1.970 1.980 1.989 1.998 2.008 2.017 250260 2.017 2.027 2.036 2.046 2.055 2.064 2.074 2.083 2.093 2.102 2.112 260270 2.112 2.121 2.131 2.140 2.150 2.159 2.169 2.179 2.188 2.198 2.207 270280 2.207 2.217 2.226 2.236 2.246 2.255 2.265 2.275 2.284 2.294 2.304 280290 2.304 2.313 2.323 2.333 2.342 2.352 2.362 2.371 2.381 2.391 2.401 290

300 2.401 2.410 2.420 2.430 2.440 2.449 2.459 2.469 2.479 2.488 2.498 300310 2.498 2.508 2.518 2.528 2.538 2.547 2.557 2.567 2.577 2.587 2.597 310320 2.597 2.607 2.617 2.626 2.636 2.646 2.656 2.666 2.676 2.686 2.696 320330 2.696 2.706 2.716 2.726 2.736 2.746 2.756 2.766 2.776 2.786 2.796 330340 2.796 2.806 2.816 2.826 2.836 2.846 2.856 2.866 2.876 2.886 2.896 340

350 2.896 2.906 2.916 2.926 2.937 2.947 2.957 2.967 2.977 2.987 2.997 350360 2.997 3.007 3.018 3.028 3.038 3.048 3.058 3.068 3.079 3.089 3.099 360370 3.099 3.109 3.119 3.130 3.140 3.150 3.160 3.171 3.181 3.191 3.201 370380 3.201 3.212 3.222 3.232 3.242 3.253 3.263 3.273 3.284 3.294 3.304 380390 3.304 3.315 3.325 3.335 3.346 3.356 3.366 3.377 3.387 3.397 3.408 390

400 3.408 3.418 3.428 3.439 3.449 3.460 3.470 3.480 3.491 3.501 3.512 400410 3.512 3.522 3.533 3.543 3.553 3.564 3.574 3.585 3.595 3.606 3.616 410420 3.616 3.627 3.637 3.648 3.658 3.669 3.679 3.690 3.700 3.711 3.721 420430 3.721 3.732 3.742 3.753 3.764 3.774 3.785 3.795 3.806 3.816 3.827 430440 3.827 3.838 3.848 3.859 3.869 3.880 3.891 3.901 3.912 3.922 3.933 440

450 3.933 3.944 3.954 3.965 3.976 3.986 3.997 4.008 4.018 4.029 4.040 450460 4.040 4.050 4.061 4.072 4.083 4.093 4.104 4.115 4.125 4.136 4.147 460470 4.147 4.158 4.168 4.179 4.190 4.201 4.211 4.222 4.233 4.244 4.255 470480 4.255 4.265 4.276 4.287 4.298 4.309 4.319 4.330 4.341 4.352 4.363 480490 4.363 4.373 4.384 4.395 4.406 4.417 4.428 4.439 4.449 4.460 4.471 490

500 4.471 4.482 4.493 4.504 4.515 4.526 4.537 4.548 4.558 4.569 4.580 500510 4.580 4.591 4.602 4.613 4.624 4.635 4.646 4.657 4.668 4.679 4.690 510520 4.690 4.701 4.712 4.723 4.734 4.745 4.756 4.767 4.778 4.789 4.800 520530 4.800 4.811 4.822 4.833 4.844 4.855 4.866 4.877 4.888 4.899 4.910 530540 4.910 4.922 4.933 4.944 4.955 4.966 4.977 4.988 4.999 5.010 5.021 540

550 5.021 5.033 5.044 5.055 5.066 5.077 5.088 5.099 5.111 5.122 5.133 550560 5.133 5.144 5.155 5.166 5.178 5.189 5.200 5.211 5.222 5.234 5.245 560570 5.245 5.256 5.267 5.279 5.290 5.301 5.312 5.323 5.335 5.346 5.357 570580 5.357 5.369 5.380 5.391 5.402 5.414 5.425 5.436 5.448 5.459 5.470 580590 5.470 5.481 5.493 5.504 5.515 5.527 5.538 5.549 5.561 5.572 5.583 590

600 5.583 5.595 5.606 5.618 5.629 5.640 5.652 5.663 5.674 5.686 5.697 600610 5.697 5.709 5.720 5.731 5.743 5.754 5.766 5.777 5.789 5.800 5.812 610620 5.812 5.823 5.834 5.846 5.857 5.869 5.880 5.892 5.903 5.915 5.926 620630 5.926 5.938 5.949 5.961 5.972 5.984 5.995 6.007 6.018 6.030 6.041 630640 6.041 6.053 6.065 6.076 6.088 6.099 6.111 6.122 6.134 6.146 6.157 640

650 6.157 6.169 6.180 6.192 6.204 6.215 6.227 6.238 6.250 6.262 6.273 650660 6.273 6.285 6.297 6.308 6.320 6.332 6.343 6.355 6.367 6.378 6.390 660670 6.390 6.402 6.413 6.425 6.437 6.448 6.460 6.472 6.484 6.495 6.507 670680 6.507 6.519 6.531 6.542 6.554 6.566 6.578 6.589 6.601 6.613 6.625 680690 6.625 6.636 6.648 6.660 6.672 6.684 6.695 6.707 6.719 6.731 6.743 690

700 6.743 6.755 6.766 6.778 6.790 6.802 6.814 6.826 6.838 6.849 6.861 700710 6.861 6.873 6.885 6.897 6.909 6.921 6.933 6.945 6.956 6.968 6.980 710720 6.980 6.992 7.004 7.016 7.028 7.040 7.052 7.064 7.076 7.088 7.100 720730 7.100 7.112 7.124 7.136 7.148 7.160 7.172 7.184 7.196 7.208 7.220 730740 7.220 7.232 7.244 7.256 7.268 7.280 7.292 7.304 7.316 7.328 7.340 740

750 7.340 7.352 7.364 7.376 7.389 7.401 7.413 7.425 7.437 7.449 7.461 750760 7.461 7.473 7.485 7.498 7.510 7.522 7.534 7.546 7.558 7.570 7.583 760770 7.583 7.595 7.607 7.619 7.631 7.644 7.656 7.668 7.680 7.692 7.705 770780 7.705 7.717 7.729 7.741 7.753 7.766 7.778 7.790 7.802 7.815 7.827 780790 7.827 7.839 7.851 7.864 7.876 7.888 7.901 7.913 7.925 7.938 7.950 790

800 7.950 7.962 7.974 7.987 7.999 8.011 8.024 8.036 8.048 8.061 8.073 800810 8.073 8.086 8.098 8.110 8.123 8.135 8.147 8.160 8.172 8.185 8.197 810820 8.197 8.209 8.222 8.234 8.247 8.259 8.272 8.284 8.296 8.309 8.321 820830 8.321 8.334 8.346 8.359 8.371 8.384 8.396 8.409 8.421 8.434 8.446 830840 8.446 8.459 8.471 8.484 8.496 8.509 8.521 8.534 8.546 8.559 8.571 840

850 8.571 8.584 8.597 8.609 8.622 8.634 8.647 8.659 8.672 8.685 8.697 850860 8.697 8.710 8.722 8.735 8.748 8.760 8.773 8.785 8.798 8.811 8.823 860870 8.823 8.836 8.849 8.861 8.874 8.887 8.899 8.912 8.925 8.937 8.950 870880 8.950 8.963 8.975 8.988 9.001 9.014 9.026 9.039 9.052 9.065 9.077 880890 9.077 9.090 9.103 9.115 9.128 9.141 9.154 9.167 9.179 9.192 9.205 890

900 9.205 9.218 9.230 9.243 9.256 9.269 9.282 9.294 9.307 9.320 9.333 900910 9.333 9.346 9.359 9.371 9.384 9.397 9.410 9.423 9.436 9.449 9.461 910920 9.461 9.474 9.487 9.500 9.513 9.526 9.539 9.552 9.565 9.578 9.590 920930 9.590 9.603 9.616 9.629 9.642 9.655 9.668 9.681 9.694 9.707 9.720 930940 9.720 9.733 9.746 9.759 9.772 9.785 9.798 9.811 9.824 9.837 9.850 940

950 9.850 9.863 9.876 9.889 9.902 9.915 9.928 9.941 9.954 9.967 9.980 950960 9.980 9.993 10.006 10.019 10.032 10.046 10.059 10.072 10.085 10.098 10.111 960970 10.111 10.124 10.137 10.150 10.163 10.177 10.190 10.203 10.216 10.229 10.242 970980 10.242 10.255 10.268 10.282 10.295 10.308 10.321 10.334 10.347 10.361 10.374 980990 10.374 10.387 10.400 10.413 10.427 10.440 10.453 10.466 10.480 10.493 10.506 990

1000 10.506 10.519 10.532 10.546 10.559 10.572 10.585 10.599 10.612 10.625 10.638 10001010 10.638 10.652 10.665 10.678 10.692 10.705 10.718 10.731 10.745 10.758 10.771 10101020 10.771 10.785 10.798 10.811 10.825 10.838 10.851 10.865 10.878 10.891 10.905 10201030 10.905 10.918 10.932 10.945 10.958 10.972 10.985 10.998 11.012 11.025 11.039 10301040 11.039 11.052 11.065 11.079 11.092 11.106 11.119 11.132 11.146 11.159 11.173 1040

1050 11.173 11.186 11.200 11.213 11.227 11.240 11.253 11.267 11.280 11.294 11.307 10501060 11.307 11.321 11.334 11.348 11.361 11.375 11.388 11.402 11.415 11.429 11.442 10601070 11.442 11.456 11.469 11.483 11.496 11.510 11.524 11.537 11.551 11.564 11.578 10701080 11.578 11.591 11.605 11.618 11.632 11.646 11.659 11.673 11.686 11.700 11.714 10801090 11.714 11.727 11.741 11.754 11.768 11.782 11.795 11.809 11.822 11.836 11.850 1090

1100 11.850 11.863 11.877 11.891 11.904 11.918 11.931 11.945 11.959 11.972 11.986 11001110 11.986 12.000 12.013 12.027 12.041 12.054 12.068 12.082 12.096 12.109 12.123 11101120 12.123 12.137 12.150 12.164 12.178 12.191 12.205 12.219 12.233 12.246 12.260 11201130 12.260 12.274 12.288 12.301 12.315 12.329 12.342 12.356 12.370 12.384 12.397 11301140 12.397 12.411 12.425 12.439 12.453 12.466 12.480 12.494 12.508 12.521 12.535 1140

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 2642°F0 to 1450°CExtension Grade32 to 300°F0 to 150°CLIMITS OF ERROR(whichever is greater)Standard: 1.5°C or 0.25%Special: 0.6°C or 0.1%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High TemperatureTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°C RR

°C -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

ThermocoupleGrade


Platinum

ExtensionGrade

+–

+–


NONEESTABLISHED

+–


Z-211


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

1150 12.535 12.549 12.563 12.577 12.590 12.604 12.618 12.632 12.646 12.659 12.673 11501160 12.673 12.687 12.701 12.715 12.729 12.742 12.756 12.770 12.784 12.798 12.812 11601170 12.812 12.825 12.839 12.853 12.867 12.881 12.895 12.909 12.922 12.936 12.950 11701180 12.950 12.964 12.978 12.992 13.006 13.019 13.033 13.047 13.061 13.075 13.089 11801190 13.089 13.103 13.117 13.131 13.145 13.158 13.172 13.186 13.200 13.214 13.228 1190

1200 13.228 13.242 13.256 13.270 13.284 13.298 13.311 13.325 13.339 13.353 13.367 12001210 13.367 13.381 13.395 13.409 13.423 13.437 13.451 13.465 13.479 13.493 13.507 12101220 13.507 13.521 13.535 13.549 13.563 13.577 13.590 13.604 13.618 13.632 13.646 12201230 13.646 13.660 13.674 13.688 13.702 13.716 13.730 13.744 13.758 13.772 13.786 12301240 13.786 13.800 13.814 13.828 13.842 13.856 13.870 13.884 13.898 13.912 13.926 1240

1250 13.926 13.940 13.954 13.968 13.982 13.996 14.010 14.024 14.038 14.052 14.066 12501260 14.066 14.081 14.095 14.109 14.123 14.137 14.151 14.165 14.179 14.193 14.207 12601270 14.207 14.221 14.235 14.249 14.263 14.277 14.291 14.305 14.319 14.333 14.347 12701280 14.347 14.361 14.375 14.390 14.404 14.418 14.432 14.446 14.460 14.474 14.488 12801290 14.488 14.502 14.516 14.530 14.544 14.558 14.572 14.586 14.601 14.615 14.629 1290

1300 14.629 14.643 14.657 14.671 14.685 14.699 14.713 14.727 14.741 14.755 14.770 13001310 14.770 14.784 14.798 14.812 14.826 14.840 14.854 14.868 14.882 14.896 14.911 13101320 14.911 14.925 14.939 14.953 14.967 14.981 14.995 15.009 15.023 15.037 15.052 13201330 15.052 15.066 15.080 15.094 15.108 15.122 15.136 15.150 15.164 15.179 15.193 13301340 15.193 15.207 15.221 15.235 15.249 15.263 15.277 15.291 15.306 15.320 15.334 1340

1350 15.334 15.348 15.362 15.376 15.390 15.404 15.419 15.433 15.447 15.461 15.475 13501360 15.475 15.489 15.503 15.517 15.531 15.546 15.560 15.574 15.588 15.602 15.616 13601370 15.616 15.630 15.645 15.659 15.673 15.687 15.701 15.715 15.729 15.743 15.758 13701380 15.758 15.772 15.786 15.800 15.814 15.828 15.842 15.856 15.871 15.885 15.899 13801390 15.899 15.913 15.927 15.941 15.955 15.969 15.984 15.998 16.012 16.026 16.040 1390

1400 16.040 16.054 16.068 16.082 16.097 16.111 16.125 16.139 16.153 16.167 16.181 14001410 16.181 16.196 16.210 16.224 16.238 16.252 16.266 16.280 16.294 16.309 16.323 14101420 16.323 16.337 16.351 16.365 16.379 16.393 16.407 16.422 16.436 16.450 16.464 14201430 16.464 16.478 16.492 16.506 16.520 16.534 16.549 16.563 16.577 16.591 16.605 14301440 16.605 16.619 16.633 16.647 16.662 16.676 16.690 16.704 16.718 16.732 16.746 1440

1450 16.746 16.760 16.774 16.789 16.803 16.817 16.831 16.845 16.859 16.873 16.887 14501460 16.887 16.901 16.915 16.930 16.944 16.958 16.972 16.986 17.000 17.014 17.028 14601470 17.028 17.042 17.056 17.071 17.085 17.099 17.113 17.127 17.141 17.155 17.169 14701480 17.169 17.183 17.197 17.211 17.225 17.240 17.254 17.268 17.282 17.296 17.310 14801490 17.310 17.324 17.338 17.352 17.366 17.380 17.394 17.408 17.423 17.437 17.451 1490

1500 17.451 17.465 17.479 17.493 17.507 17.521 17.535 17.549 17.563 17.577 17.591 15001510 17.591 17.605 17.619 17.633 17.647 17.661 17.676 17.690 17.704 17.718 17.732 15101520 17.732 17.746 17.760 17.774 17.788 17.802 17.816 17.830 17.844 17.858 17.872 15201530 17.872 17.886 17.900 17.914 17.928 17.942 17.956 17.970 17.984 17.998 18.012 15301540 18.012 18.026 18.040 18.054 18.068 18.082 18.096 18.110 18.124 18.138 18.152 1540

1550 18.152 18.166 18.180 18.194 18.208 18.222 18.236 18.250 18.264 18.278 18.292 15501560 18.292 18.306 18.320 18.334 18.348 18.362 18.376 18.390 18.404 18.417 18.431 15601570 18.431 18.445 18.459 18.473 18.487 18.501 18.515 18.529 18.543 18.557 18.571 15701580 18.571 18.585 18.599 18.613 18.627 18.640 18.654 18.668 18.682 18.696 18.710 15801590 18.710 18.724 18.738 18.752 18.766 18.779 18.793 18.807 18.821 18.835 18.849 1590

1600 18.849 18.863 18.877 18.891 18.904 18.918 18.932 18.946 18.960 18.974 18.988 16001610 18.988 19.002 19.015 19.029 19.043 19.057 19.071 19.085 19.098 19.112 19.126 16101620 19.126 19.140 19.154 19.168 19.181 19.195 19.209 19.223 19.237 19.250 19.264 16201630 19.264 19.278 19.292 19.306 19.319 19.333 19.347 19.361 19.375 19.388 19.402 16301640 19.402 19.416 19.430 19.444 19.457 19.471 19.485 19.499 19.512 19.526 19.540 1640

1650 19.540 19.554 19.567 19.581 19.595 19.609 19.622 19.636 19.650 19.663 19.677 16501660 19.677 19.691 19.705 19.718 19.732 19.746 19.759 19.773 19.787 19.800 19.814 16601670 19.814 19.828 19.841 19.855 19.869 19.882 19.896 19.910 19.923 19.937 19.951 16701680 19.951 19.964 19.978 19.992 20.005 20.019 20.032 20.046 20.060 20.073 20.087 16801690 20.087 20.100 20.114 20.127 20.141 20.154 20.168 20.181 20.195 20.208 20.222 1690

1700 20.222 20.235 20.249 20.262 20.275 20.289 20.302 20.316 20.329 20.342 20.356 17001710 20.356 20.369 20.382 20.396 20.409 20.422 20.436 20.449 20.462 20.475 20.488 17101720 20.488 20.502 20.515 20.528 20.541 20.554 20.567 20.581 20.594 20.607 20.620 17201730 20.620 20.633 20.646 20.659 20.672 20.685 20.698 20.711 20.724 20.736 20.749 17301740 20.749 20.762 20.775 20.788 20.801 20.813 20.826 20.839 20.852 20.864 20.877 1740

1750 20.877 20.890 20.902 20.915 20.928 20.940 20.953 20.965 20.978 20.990 21.003 17501760 21.003 21.015 21.027 21.040 21.052 21.065 21.077 21.089 21.101 1760

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 2642°F0 to 1450°CExtension Grade32 to 300°F0 to 150°CLIMITS OF ERROR(whichever is greater)Standard: 1.5°C or 0.25%Special: 0.6°C or 0.1%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High TemperatureTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°CRR

ThermocoupleGrade


Platinum

ExtensionGrade

+–

+–


NONEESTABLISHED

+–


Z-212

Z


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

0 0.000 0.000 0.000 -0.001 -0.001 -0.001 -0.001 -0.001 -0.002 -0.002 -0.002 010 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 -0.003 -0.003 -0.003 1020 -0.003 -0.003 -0.003 -0.003 -0.003 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 2030 -0.002 -0.002 -0.002 -0.002 -0.002 -0.001 -0.001 -0.001 -0.001 -0.001 0.000 3040 0.000 0.000 0.000 0.000 0.000 0.001 0.001 0.001 0.002 0.002 0.002 40

50 0.002 0.003 0.003 0.003 0.004 0.004 0.004 0.005 0.005 0.006 0.006 5060 0.006 0.007 0.007 0.008 0.008 0.009 0.009 0.010 0.010 0.011 0.011 6070 0.011 0.012 0.012 0.013 0.014 0.014 0.015 0.015 0.016 0.017 0.017 7080 0.017 0.018 0.019 0.020 0.020 0.021 0.022 0.022 0.023 0.024 0.025 8090 0.025 0.026 0.026 0.027 0.028 0.029 0.030 0.031 0.031 0.032 0.033 90

100 0.033 0.034 0.035 0.036 0.037 0.038 0.039 0.040 0.041 0.042 0.043 100110 0.043 0.044 0.045 0.046 0.047 0.048 0.049 0.050 0.051 0.052 0.053 110120 0.053 0.055 0.056 0.057 0.058 0.059 0.060 0.062 0.063 0.064 0.065 120130 0.065 0.066 0.068 0.069 0.070 0.072 0.073 0.074 0.075 0.077 0.078 130140 0.078 0.079 0.081 0.082 0.084 0.085 0.086 0.088 0.089 0.091 0.092 140

150 0.092 0.094 0.095 0.096 0.098 0.099 0.101 0.102 0.104 0.106 0.107 150160 0.107 0.109 0.110 0.112 0.113 0.115 0.117 0.118 0.120 0.122 0.123 160170 0.123 0.125 0.127 0.128 0.130 0.132 0.134 0.135 0.137 0.139 0.141 170180 0.141 0.142 0.144 0.146 0.148 0.150 0.151 0.153 0.155 0.157 0.159 180190 0.159 0.161 0.163 0.165 0.166 0.168 0.170 0.172 0.174 0.176 0.178 190

200 0.178 0.180 0.182 0.184 0.186 0.188 0.190 0.192 0.195 0.197 0.199 200210 0.199 0.201 0.203 0.205 0.207 0.209 0.212 0.214 0.216 0.218 0.220 210220 0.220 0.222 0.225 0.227 0.229 0.231 0.234 0.236 0.238 0.241 0.243 220230 0.243 0.245 0.248 0.250 0.252 0.255 0.257 0.259 0.262 0.264 0.267 230240 0.267 0.269 0.271 0.274 0.276 0.279 0.281 0.284 0.286 0.289 0.291 240

250 0.291 0.294 0.296 0.299 0.301 0.304 0.307 0.309 0.312 0.314 0.317 250260 0.317 0.320 0.322 0.325 0.328 0.330 0.333 0.336 0.338 0.341 0.344 260270 0.344 0.347 0.349 0.352 0.355 0.358 0.360 0.363 0.366 0.369 0.372 270280 0.372 0.375 0.377 0.380 0.383 0.386 0.389 0.392 0.395 0.398 0.401 280290 0.401 0.404 0.407 0.410 0.413 0.416 0.419 0.422 0.425 0.428 0.431 290

300 0.431 0.434 0.437 0.440 0.443 0.446 0.449 0.452 0.455 0.458 0.462 300310 0.462 0.465 0.468 0.471 0.474 0.478 0.481 0.484 0.487 0.490 0.494 310320 0.494 0.497 0.500 0.503 0.507 0.510 0.513 0.517 0.520 0.523 0.527 320330 0.527 0.530 0.533 0.537 0.540 0.544 0.547 0.550 0.554 0.557 0.561 330340 0.561 0.564 0.568 0.571 0.575 0.578 0.582 0.585 0.589 0.592 0.596 340

350 0.596 0.599 0.603 0.607 0.610 0.614 0.617 0.621 0.625 0.628 0.632 350360 0.632 0.636 0.639 0.643 0.647 0.650 0.654 0.658 0.662 0.665 0.669 360370 0.669 0.673 0.677 0.680 0.684 0.688 0.692 0.696 0.700 0.703 0.707 370380 0.707 0.711 0.715 0.719 0.723 0.727 0.731 0.735 0.738 0.742 0.746 380390 0.746 0.750 0.754 0.758 0.762 0.766 0.770 0.774 0.778 0.782 0.787 390

400 0.787 0.791 0.795 0.799 0.803 0.807 0.811 0.815 0.819 0.824 0.828 400410 0.828 0.832 0.836 0.840 0.844 0.849 0.853 0.857 0.861 0.866 0.870 410420 0.870 0.874 0.878 0.883 0.887 0.891 0.896 0.900 0.904 0.909 0.913 420430 0.913 0.917 0.922 0.926 0.930 0.935 0.939 0.944 0.948 0.953 0.957 430440 0.957 0.961 0.966 0.970 0.975 0.979 0.984 0.988 0.993 0.997 1.002 440

450 1.002 1.007 1.011 1.016 1.020 1.025 1.030 1.034 1.039 1.043 1.048 450460 1.048 1.053 1.057 1.062 1.067 1.071 1.076 1.081 1.086 1.090 1.095 460470 1.095 1.100 1.105 1.109 1.114 1.119 1.124 1.129 1.133 1.138 1.143 470480 1.143 1.148 1.153 1.158 1.163 1.167 1.172 1.177 1.182 1.187 1.192 480490 1.192 1.197 1.202 1.207 1.212 1.217 1.222 1.227 1.232 1.237 1.242 490

500 1.242 1.247 1.252 1.257 1.262 1.267 1.272 1.277 1.282 1.288 1.293 500510 1.293 1.298 1.303 1.308 1.313 1.318 1.324 1.329 1.334 1.339 1.344 510520 1.344 1.350 1.355 1.360 1.365 1.371 1.376 1.381 1.387 1.392 1.397 520530 1.397 1.402 1.408 1.413 1.418 1.424 1.429 1.435 1.440 1.445 1.451 530540 1.451 1.456 1.462 1.467 1.472 1.478 1.483 1.489 1.494 1.500 1.505 540

550 1.505 1.511 1.516 1.522 1.527 1.533 1.539 1.544 1.550 1.555 1.561 550560 1.561 1.566 1.572 1.578 1.583 1.589 1.595 1.600 1.606 1.612 1.617 560570 1.617 1.623 1.629 1.634 1.640 1.646 1.652 1.657 1.663 1.669 1.675 570580 1.675 1.680 1.686 1.692 1.698 1.704 1.709 1.715 1.721 1.727 1.733 580590 1.733 1.739 1.745 1.750 1.756 1.762 1.768 1.774 1.780 1.786 1.792 590

600 1.792 1.798 1.804 1.810 1.816 1.822 1.828 1.834 1.840 1.846 1.852 600610 1.852 1.858 1.864 1.870 1.876 1.882 1.888 1.894 1.901 1.907 1.913 610620 1.913 1.919 1.925 1.931 1.937 1.944 1.950 1.956 1.962 1.968 1.975 620630 1.975 1.981 1.987 1.993 1.999 2.006 2.012 2.018 2.025 2.031 2.037 630640 2.037 2.043 2.050 2.056 2.062 2.069 2.075 2.082 2.088 2.094 2.101 640

650 2.101 2.107 2.113 2.120 2.126 2.133 2.139 2.146 2.152 2.158 2.165 650660 2.165 2.171 2.178 2.184 2.191 2.197 2.204 2.210 2.217 2.224 2.230 660670 2.230 2.237 2.243 2.250 2.256 2.263 2.270 2.276 2.283 2.289 2.296 670680 2.296 2.303 2.309 2.316 2.323 2.329 2.336 2.343 2.350 2.356 2.363 680690 2.363 2.370 2.376 2.383 2.390 2.397 2.403 2.410 2.417 2.424 2.431 690

700 2.431 2.437 2.444 2.451 2.458 2.465 2.472 2.479 2.485 2.492 2.499 700710 2.499 2.506 2.513 2.520 2.527 2.534 2.541 2.548 2.555 2.562 2.569 710720 2.569 2.576 2.583 2.590 2.597 2.604 2.611 2.618 2.625 2.632 2.639 720730 2.639 2.646 2.653 2.660 2.667 2.674 2.681 2.688 2.696 2.703 2.710 730740 2.710 2.717 2.724 2.731 2.738 2.746 2.753 2.760 2.767 2.775 2.782 740

750 2.782 2.789 2.796 2.803 2.811 2.818 2.825 2.833 2.840 2.847 2.854 750760 2.854 2.862 2.869 2.876 2.884 2.891 2.898 2.906 2.913 2.921 2.928 760770 2.928 2.935 2.943 2.950 2.958 2.965 2.973 2.980 2.987 2.995 3.002 770780 3.002 3.010 3.017 3.025 3.032 3.040 3.047 3.055 3.062 3.070 3.078 780790 3.078 3.085 3.093 3.100 3.108 3.116 3.123 3.131 3.138 3.146 3.154 790

800 3.154 3.161 3.169 3.177 3.184 3.192 3.200 3.207 3.215 3.223 3.230 800810 3.230 3.238 3.246 3.254 3.261 3.269 3.277 3.285 3.292 3.300 3.308 810820 3.308 3.316 3.324 3.331 3.339 3.347 3.355 3.363 3.371 3.379 3.386 820830 3.386 3.394 3.402 3.410 3.418 3.426 3.434 3.442 3.450 3.458 3.466 830840 3.466 3.474 3.482 3.490 3.498 3.506 3.514 3.522 3.530 3.538 3.546 840

850 3.546 3.554 3.562 3.570 3.578 3.586 3.594 3.602 3.610 3.618 3.626 850860 3.626 3.634 3.643 3.651 3.659 3.667 3.675 3.683 3.692 3.700 3.708 860870 3.708 3.716 3.724 3.732 3.741 3.749 3.757 3.765 3.774 3.782 3.790 870880 3.790 3.798 3.807 3.815 3.823 3.832 3.840 3.848 3.857 3.865 3.873 880890 3.873 3.882 3.890 3.898 3.907 3.915 3.923 3.932 3.940 3.949 3.957 890

900 3.957 3.965 3.974 3.982 3.991 3.999 4.008 4.016 4.024 4.033 4.041 900910 4.041 4.050 4.058 4.067 4.075 4.084 4.093 4.101 4.110 4.118 4.127 910920 4.127 4.135 4.144 4.152 4.161 4.170 4.178 4.187 4.195 4.204 4.213 920930 4.213 4.221 4.230 4.239 4.247 4.256 4.265 4.273 4.282 4.291 4.299 930940 4.299 4.308 4.317 4.326 4.334 4.343 4.352 4.360 4.369 4.378 4.387 940

950 4.387 4.396 4.404 4.413 4.422 4.431 4.440 4.448 4.457 4.466 4.475 950960 4.475 4.484 4.493 4.501 4.510 4.519 4.528 4.537 4.546 4.555 4.564 960970 4.564 4.573 4.582 4.591 4.599 4.608 4.617 4.626 4.635 4.644 4.653 970980 4.653 4.662 4.671 4.680 4.689 4.698 4.707 4.716 4.725 4.734 4.743 980990 4.743 4.753 4.762 4.771 4.780 4.789 4.798 4.807 4.816 4.825 4.834 990

1000 4.834 4.843 4.853 4.862 4.871 4.880 4.889 4.898 4.908 4.917 4.926 10001010 4.926 4.935 4.944 4.954 4.963 4.972 4.981 4.990 5.000 5.009 5.018 10101020 5.018 5.027 5.037 5.046 5.055 5.065 5.074 5.083 5.092 5.102 5.111 10201030 5.111 5.120 5.130 5.139 5.148 5.158 5.167 5.176 5.186 5.195 5.205 10301040 5.205 5.214 5.223 5.233 5.242 5.252 5.261 5.270 5.280 5.289 5.299 1040

1050 5.299 5.308 5.318 5.327 5.337 5.346 5.356 5.365 5.375 5.384 5.394 10501060 5.394 5.403 5.413 5.422 5.432 5.441 5.451 5.460 5.470 5.480 5.489 10601070 5.489 5.499 5.508 5.518 5.528 5.537 5.547 5.556 5.566 5.576 5.585 10701080 5.585 5.595 5.605 5.614 5.624 5.634 5.643 5.653 5.663 5.672 5.682 10801090 5.682 5.692 5.702 5.711 5.721 5.731 5.740 5.750 5.760 5.770 5.780 1090

1100 5.780 5.789 5.799 5.809 5.819 5.828 5.838 5.848 5.858 5.868 5.878 11001110 5.878 5.887 5.897 5.907 5.917 5.927 5.937 5.947 5.956 5.966 5.976 11101120 5.976 5.986 5.996 6.006 6.016 6.026 6.036 6.046 6.055 6.065 6.075 11201130 6.075 6.085 6.095 6.105 6.115 6.125 6.135 6.145 6.155 6.165 6.175 11301140 6.175 6.185 6.195 6.205 6.215 6.225 6.235 6.245 6.256 6.266 6.276 1140

1150 6.276 6.286 6.296 6.306 6.316 6.326 6.336 6.346 6.356 6.367 6.377 11501160 6.377 6.387 6.397 6.407 6.417 6.427 6.438 6.448 6.458 6.468 6.478 11601170 6.478 6.488 6.499 6.509 6.519 6.529 6.539 6.550 6.560 6.570 6.580 11701180 6.580 6.591 6.601 6.611 6.621 6.632 6.642 6.652 6.663 6.673 6.683 11801190 6.683 6.693 6.704 6.714 6.724 6.735 6.745 6.755 6.766 6.776 6.786 1190

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 3092°F0 to 1700°CExtension Grade32 to 212°F0 to 100°CLIMITS OF ERROR(whichever is greater)Standard: 0.5°C over 800°CSpecial: NOT ESTABLISHEDCOMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High Temperature;Common Use in Glass IndustryTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°C BB

°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

ThermocoupleGrade


Platinum-6% Rhodium

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-213


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

1200 6.786 6.797 6.807 6.818 6.828 6.838 6.849 6.859 6.869 6.880 6.890 12001210 6.890 6.901 6.911 6.922 6.932 6.942 6.953 6.963 6.974 6.984 6.995 12101220 6.995 7.005 7.016 7.026 7.037 7.047 7.058 7.068 7.079 7.089 7.100 12201230 7.100 7.110 7.121 7.131 7.142 7.152 7.163 7.173 7.184 7.194 7.205 12301240 7.205 7.216 7.226 7.237 7.247 7.258 7.269 7.279 7.290 7.300 7.311 1240

1250 7.311 7.322 7.332 7.343 7.353 7.364 7.375 7.385 7.396 7.407 7.417 12501260 7.417 7.428 7.439 7.449 7.460 7.471 7.482 7.492 7.503 7.514 7.524 12601270 7.524 7.535 7.546 7.557 7.567 7.578 7.589 7.600 7.610 7.621 7.632 12701280 7.632 7.643 7.653 7.664 7.675 7.686 7.697 7.707 7.718 7.729 7.740 12801290 7.740 7.751 7.761 7.772 7.783 7.794 7.805 7.816 7.827 7.837 7.848 1290

1300 7.848 7.859 7.870 7.881 7.892 7.903 7.914 7.924 7.935 7.946 7.957 13001310 7.957 7.968 7.979 7.990 8.001 8.012 8.023 8.034 8.045 8.056 8.066 13101320 8.066 8.077 8.088 8.099 8.110 8.121 8.132 8.143 8.154 8.165 8.176 13201330 8.176 8.187 8.198 8.209 8.220 8.231 8.242 8.253 8.264 8.275 8.286 13301340 8.286 8.298 8.309 8.320 8.331 8.342 8.353 8.364 8.375 8.386 8.397 1340

1350 8.397 8.408 8.419 8.430 8.441 8.453 8.464 8.475 8.486 8.497 8.508 13501360 8.508 8.519 8.530 8.542 8.553 8.564 8.575 8.586 8.597 8.608 8.620 13601370 8.620 8.631 8.642 8.653 8.664 8.675 8.687 8.698 8.709 8.720 8.731 13701380 8.731 8.743 8.754 8.765 8.776 8.787 8.799 8.810 8.821 8.832 8.844 13801390 8.844 8.855 8.866 8.877 8.889 8.900 8.911 8.922 8.934 8.945 8.956 1390

1400 8.956 8.967 8.979 8.990 9.001 9.013 9.024 9.035 9.047 9.058 9.069 14001410 9.069 9.080 9.092 9.103 9.114 9.126 9.137 9.148 9.160 9.171 9.182 14101420 9.182 9.194 9.205 9.216 9.228 9.239 9.251 9.262 9.273 9.285 9.296 14201430 9.296 9.307 9.319 9.330 9.342 9.353 9.364 9.376 9.387 9.398 9.410 14301440 9.410 9.421 9.433 9.444 9.456 9.467 9.478 9.490 9.501 9.513 9.524 1440

1450 9.524 9.536 9.547 9.558 9.570 9.581 9.593 9.604 9.616 9.627 9.639 14501460 9.639 9.650 9.662 9.673 9.684 9.696 9.707 9.719 9.730 9.742 9.753 14601470 9.753 9.765 9.776 9.788 9.799 9.811 9.822 9.834 9.845 9.857 9.868 14701480 9.868 9.880 9.891 9.903 9.914 9.926 9.937 9.949 9.961 9.972 9.984 14801490 9.984 9.995 10.007 10.018 10.030 10.041 10.053 10.064 10.076 10.088 10.099 1490

1500 10.099 10.111 10.122 10.134 10.145 10.157 10.168 10.180 10.192 10.203 10.215 15001510 10.215 10.226 10.238 10.249 10.261 10.273 10.284 10.296 10.307 10.319 10.331 15101520 10.331 10.342 10.354 10.365 10.377 10.389 10.400 10.412 10.423 10.435 10.447 15201530 10.447 10.458 10.470 10.482 10.493 10.505 10.516 10.528 10.540 10.551 10.563 15301540 10.563 10.575 10.586 10.598 10.609 10.621 10.633 10.644 10.656 10.668 10.679 1540

1550 10.679 10.691 10.703 10.714 10.726 10.738 10.749 10.761 10.773 10.784 10.796 15501560 10.796 10.808 10.819 10.831 10.843 10.854 10.866 10.877 10.889 10.901 10.913 15601570 10.913 10.924 10.936 10.948 10.959 10.971 10.983 10.994 11.006 11.018 11.029 15701580 11.029 11.041 11.053 11.064 11.076 11.088 11.099 11.111 11.123 11.134 11.146 15801590 11.146 11.158 11.169 11.181 11.193 11.205 11.216 11.228 11.240 11.251 11.263 1590

1600 11.263 11.275 11.286 11.298 11.310 11.321 11.333 11.345 11.357 11.368 11.380 16001610 11.380 11.392 11.403 11.415 11.427 11.438 11.450 11.462 11.474 11.485 11.497 16101620 11.497 11.509 11.520 11.532 11.544 11.555 11.567 11.579 11.591 11.602 11.614 16201630 11.614 11.626 11.637 11.649 11.661 11.673 11.684 11.696 11.708 11.719 11.731 16301640 11.731 11.743 11.754 11.766 11.778 11.790 11.801 11.813 11.825 11.836 11.848 1640

1650 11.848 11.860 11.871 11.883 11.895 11.907 11.918 11.930 11.942 11.953 11.965 16501660 11.965 11.977 11.988 12.000 12.012 12.024 12.035 12.047 12.059 12.070 12.082 16601670 12.082 12.094 12.105 12.117 12.129 12.141 12.152 12.164 12.176 12.187 12.199 16701680 12.199 12.211 12.222 12.234 12.246 12.257 12.269 12.281 12.292 12.304 12.316 16801690 12.316 12.327 12.339 12.351 12.363 12.374 12.386 12.398 12.409 12.421 12.433 1690

1700 12.433 12.444 12.456 12.468 12.479 12.491 12.503 12.514 12.526 12.538 12.549 17001710 12.549 12.561 12.572 12.584 12.596 12.607 12.619 12.631 12.642 12.654 12.666 17101720 12.666 12.677 12.689 12.701 12.712 12.724 12.736 12.747 12.759 12.770 12.782 17201730 12.782 12.794 12.805 12.817 12.829 12.840 12.852 12.863 12.875 12.887 12.898 17301740 12.898 12.910 12.921 12.933 12.945 12.956 12.968 12.980 12.991 13.003 13.014 1740

1750 13.014 13.026 13.037 13.049 13.061 13.072 13.084 13.095 13.107 13.119 13.130 17501760 13.130 13.142 13.153 13.165 13.176 13.188 13.200 13.211 13.223 13.234 13.246 17601770 13.246 13.257 13.269 13.280 13.292 13.304 13.315 13.327 13.338 13.350 13.361 17701780 13.361 13.373 13.384 13.396 13.407 13.419 13.430 13.442 13.453 13.465 13.476 17801790 13.476 13.488 13.499 13.511 13.522 13.534 13.545 13.557 13.568 13.580 13.591 1790

1800 13.591 13.603 13.614 13.626 13.637 13.649 13.660 13.672 13.683 13.694 13.706 18001810 13.706 13.717 13.729 13.740 13.752 13.763 13.775 13.786 13.797 13.809 13.820 1810

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 3092°F0 to 1700°CExtension Grade32 to 212°F0 to 100°CLIMITS OF ERROR(whichever is greater)Standard: 0.5°C over 800°CSpecial: NOT ESTABLISHEDCOMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High Temperature;Common Use in Glass IndustryTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°CBB

ThermocoupleGrade


Platinum-6% Rhodium

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-214

Z


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

-260 - 4.345 - 4.345 - 4.344 - 4.344 - 4.343 - 4.342 - 4.341 - 4.340 - 4.339 - 4.337 -4.336 -260-250 -4.338 -4.334 -4.332 -4.330 -4.328 -4.326 -4.324 -4.321 -4.319 -4.318 -4.313 -250

-240 -4.313 -4.310 -4.307 -4.304 -4.300 -4.297 -4.293 -4.289 -4.285 -4.281 -4.277 -240-230 -4.277 -4.273 -4.268 -4.263 -4.258 -4.254 -4.248 -4.243 -4.238 -4.232 -4.226 -230-220 -4.226 -4.221 -4.215 -4.209 -4.202 -4.196 -4.189 -4.183 -4.176 - 4.169 -4.162 -220-210 -4.162 -4.154 -4.147 -4.140 -4.132 -4.124 -4.116 -4.108 -4.100 -4.091 -4.083 -210-200 -4.083 -4.074 -4.066 -4.057 -4.048 -4.038 -4.029 -4.020 -4.010 -4.000 -3.990 -200

-190 -3.990 -3.980 -3.970 -3.960 -3.950 -3.939 -3.928 -3.918 -3.907 -3.898 -3.884 -190-180 -3.884 -3.873 -3.862 -3.850 -3.838 -3.827 -3.815 -3.803 -3.790 -3.778 -3.786 -180-170 -3.766 -3.753 -3.740 -3.728 -3.715 -3.702 -3.688 -3.675 -3.662 -3.648 -3.634 -170-160 -3.634 -3.621 -3.607 -3.593 -3.578 -3.564 -3.550 -3.535 -3.521 -3.506 -3.491 -160-150 -3.491 -3.476 -3.461 -3.446 -3.431 -3.415 -3.400 -3.384 -3.368 -3.352 -3.336 -150

-140 -3.336 -3.320 -3.304 -3.288 -3.271 -3.255 -3.238 -3.221 -3.205 -3.188 -3.171 -140-130 -3.171 -3.153 -3.136 -3.119 -3.101 -3.084 -3.066 -3.048 -3.030 -3.012 -2.994 -130-120 -2.994 -2.976 -2.958 -2.939 -2.921 -2.902 -2.883 -2.865 -2.846 -2.827 -2.808 -120-110 -2.808 -2.789 -2.769 -2.750 -2.730 -2.711 -2.691 -2.672 -2.652 -2.632 -2.612 -110-100 -2.612 -2.592 -2.571 -2.551 -2.531 -2.510 -2.490 -2.469 -2.448 -2.428 -2.407 -100

-90 -2.407 -2.386 -2.385 -2.344 -2.322 -2.301 -2.280 -2.258 -2.237 -2.215 -2.193 -90-80 -2.193 -2.172 -2.150 -2.128 -2.106 -2.084 -2.082 -2. 039 -2.017 -1.995 -1.972 -80-70 -1.972 -1.950 -1.927 -1.905 -1.882 -1.859 -1.836 -1.813 -1.790 -1.767 -1.744 -70-60 -1.744 -1.721 -1.698 -1.674 -1.651 -1.627 -1.604 -1.580 -1.557 -1.533 -1.509 -60-50 -1.509 -1.485 -1.462 -1.438 -1.414 -1.390 -1.366 -1.341 -1.317 -1.293 -1.269 -50

-40 -1.269 -1.244 -1.220 -1.195 -1.171 -1.146 -1.122 -1.097 -1.072 -1.048 -1.023 -40-30 -1.023 -0.998 -0.973 -0.948 -0.923 -0.898 -0.873 -0.848 -0.823 -0.798 -0.772 -30-20 -0.772 -0.747 -0.722 -0.696 -0.671 -0.646 -0.620 -0.595 -0.589 -0.544 -0.518 -20-10 -0.518 -0.492 -0.467 -0.441 -0.415 -0.390 -0.364 -0.338 -0.312 -0.286 -0.260 -10

0 -0.260 -0.234 -0.209 -0.183 -0.157 -0.131 -0.104 -0.078 -0.052 -0.026 0.000 0

0 0.000 0.026 0.052 0.078 0.104 0.130 0.156 0.182 0.208 0.235 0.261 010 0.261 0.287 0.313 0.340 0.366 0.393 0.419 0.446 0.472 0.499 0.525 1020 0.525 0.552 0.578 O.605 0.632 O.659 0.685 0.712 0.739 0.766 0.793 2030 0.793 0.820 0.847 0.874 0.901 0.928 0.955 0.983 1.010 1.037 1.065 3040 1.065 1.092 1.119 1.147 1.174 1.202 1.229 1.257 1.284 1.312 1.340 40

50 1.340 1.368 1.395 1.423 1.451 1.479 1.507 1.535 1.563 1.501 1.619 5060 1.619 1.647 1.675 1.703 1.732 1.760 1.788 1.817 1.845 1.873 1.902 6070 1.902 1.930 1.959 1.988 2.016 2.045 2.074 2.102 2.131 2.160 2.189 7080 2.189 2.218 2.247 2.276 2.305 2.334 2.363 2.392 2.421 2.450 2.480 8090 2.480 2.509 2.538 2.568 2.597 2.826 2.656 2.685 2.715 2.744 2.774 90

100 2.774 2.804 2.833 2.863 2.893 2.923 2.953 2.983 3.012 3.042 3.072 100110 3.072 3.102 3.133 3.163 3.193 3.223 3.253 3.283 3.314 3.344 3.374 110120 3.374 3.405 3.435 3.466 3.496 3.527 3.557 3.588 3.619 3.649 3.680 120130 3.680 3.711 3.742 3.772 3.803 3.834 3.865 3.896 3.927 3.958 3.989 130140 3.989 4.020 4.051 4.083 4.114 4.145 4.176 4.208 4.239 4.270 4.302 140

150 4.302 4.333 4.365 4.396 4.428 4.459 4.491 4.523 4.554 4.586 4.618 I5O160 4.618 4.650 4.681 4.713 4.745 4.777 4.809 4.841 4.873 4.905 4.937 160170 4.937 4.969 5.001 5.033 5.066 5.098 5.130 5.162 5.195 5.227 5.259 170180 5.259 5.292 5.324 5.357 5.389 5.422 5.454 5.487 5.520 5.552 5.585 ISO190 5.585 5.618 5.650 5.683 5.716 5.749 5.782 5.815 5.847 5.880 5.913 190

200 5.913 5.946 5.979 6.013 6.046 6.079 6.112 6.145 6.178 6.211 6.245 200210 6.245 6.278 6.311 6.345 6.378 6.411 6.445 6.478 6.512 6.545 6.579 210220 6.579 68.612 e.e" 6.680 8.713 15.747 6.781 6.814 6.848 6.882 6.918 220230 6.916 6.949 6.983 7.017 7.051 7.085 7.119 7.153 7.187 7.221 7.255 230240 7.255 7.289 7.323 7.357 7.392 7.426 7.460 7.494 7.528 7.583 7.597 240

250 7.597 7.631 7.666 7.700 7.734 7.769 7.803 7.838 7.872 7.907 7.941 250260 7.941 7.976 8.010 8.045 8.080 8.114 8.149 8.184 8.218 8.253 8.288 260270 8.288 8.323 8.358 8.392 8.427 8.462 8.497 8.532 8.567 8.602 8.637 270280 8.637 8.672 8.707 8.742 8.777 8.812 8.847 8.882 8.918 8.953 8.988 280290 8.988 9.023 9.058 9.094 9.129 9.164 9.200 9.235 9.270 9.306 9.341 290

300 9.341 9.377 9.412 9.448 9.483 9.519 9.554 9.590 9.625 9.661 9.696 300310 9.696 9.732 9.768 9.803 9.839 9.875 9.910 9.946 9.982 10.018 10.054 310320 10.054 10.089 10.125 10.161 10.197 10.233 10.269 10.305 10.341 10.377 10.413 320330 10.413 10.449 10.485 10.521 10.557 10.593 10.629 10.665 10.701 10.737 10.774 330340 10.774 10.810 10.846 10.882 10.918 10.955 10.991 11.027 11.064 11.100 11.136 340

350 11.136 11.173 11.209 11.245 11.282 11.318 11.355 11.391 11.428 11.464 11.501 350360 11.501 11.537 11.574 1.610 11.647 11.683 11.720 11.757 11.793 11.830 11.867 360370 11.867 11.903 11.940 11.977 12.013 12.050 12.087 12.124 12.160 12.197 12.234 370380 12.234 12.271 12.308 12.345 12.382 12.418 12.455 12.492 12.529 12.566 12.603 380390 12.603 12.640 12.677 12.714 12.751 12.788 12.825 12.862 12.899 12.937 12.974 390

400 12.974 13.011 13.048 13.085 13.122 13.159 13.197 13.234 13.271 13.308 13.346 400410 13.346 13.383 13.420 13.457 13.495 13.532 13.569 13.607 13.644 13.682 13.719 410420 13.719 13.756 13.794 13.831 13.869 13.906 13.944 13.981 14.019 14.056 14.094 420430 14.094 14.131 14.169 14.206 14.244 14.281 14.319 14.356 14.394 14.432 14.469 430440 14.469 14.507 14.545 14.582 14.620 14.658 14.695 14.733 14.771 14.809 14.846 440

450 14.848 14.884 14.922 14.960 14.998 15.035 15.073 15.111 15.149 15.187 15.225 450460 15.225 15.262 15.300 15.338 15.376 15.414 15.452 15.490 15.528 15.566 15.604 460470 15.604 15.642 15.680 15.718 15.756 15.794 15.832 15.870 15.908 15.946 15.984 470480 15.984 16.022 16.060 I 6.099 16.137 16.175 16.213 16.251 16.289 16.327 16.366 480490 16.366 16.404 16.442 16.480 16.518 16.557 16.595 16.633 16.671 16.710 16.748 490

500 16.748 16.786 I 6.824 16.883 16.901 16.939 16.978 17.016 17.054 17.093 17.131 Soo510 17.131 17.169 17.208 17.246 17.285 17.323 17.361 17.400 17.438 17.477 17.515 510520 17.515 17.554 17.592 17.630 17.669 17.707 17.746 17.784 17.823 17.861 17.900 520530 17.900 17.938 17.977 18.016 18.054 18.093 18.131 18.170 18.208 18.247 18.286 530540 18.286 18.324 18.363 18.401 18.440 18.479 18.517 18.556 18.595 18.633 18.672 540

550 18.672 18.711 18.749 18.788 18.827 18.865 18.904 18.943 18.982 19.020 19.059 550560 19.059 19.096 19.136 19.175 19.214 19.253 19.292 19.330 19.369 19.408 19.447 560570 19.447 19.485 19.524 19.563 19.602 19.641 19.680 19.718 19.757 19.796 19.835 570580 19.835 19.874 19.913 19.952 19.990 20.029 20.068 20.107 20.146 20.185 20.224 580590 20.224 20.263 20.302 20.341 20.379 20.418 20.457 20.496 20.535 20.574 20.613 590

600 20.613 20.652 20.69l 20.730 20.769 20.808 20.847 20.886 20.925 20.964 21.003 600610 21.003 21.042 21.081 21.120 21.159 21.198 21.237 21.276 21.315 21.354 21.393 610620 21.393 21.432 21.471 21.510 21.549 21.588 21.628 21.667 21.706 21.745 21.784 620630 21.784 21.823 21.862 21.901 21.940 21.979 22.018 22.058 22.097 22.136 22.175 630640 22.175 22.214 22.253 22.292 22.331 22.370 22.410 22.449 22.488 22.527 22.566 640

650 22.556 22.605 22.644 22.684 22.723 22.762 22.801 22.840 22.879 22.919 22.958 650660 22.958 22.997 23.036 23.075 23.115 23.154 23.193 23.232 23.271 23.311 23.350 660670 23.350 23.389 23.428 23.467 23.507 23.546 23.585 23.624 23.663 23.703 23.742 670680 23.742 23.781 23.820 23.860 23.899 23.938 23.977 24.016 24.056 24.095 24.134 680690 24.134 24.173 24.213 24.252 24.291 24.330 24.370 24.409 24.448 24.487 24.527 690

700 24.527 24.566 24.605 24.644 24.684 24.723 24.762 24.801 24.841 24.880 24.919 700710 24.919 24.959 24.998 25.037 25.076 25.116 25.155 25.194 25.233 25.273 25.312 710720 25.312 25.351 25.391 25.430 25.469 25.508 25.548 25.587 25.626 25.666 25.705 720730 25.705 25.744 25.783 25.823 25.862 25.901 25.941 25.980 26.019 26.058 26.098 730740 26.098 26.137 26.176 26.216 26.255 26.294 26.333 26.373 26.412 26.451 26.491 740

750 26.491 26.530 26.569 26.608 26.648 26.687 26.726 26.766 26.805 26.844 26.883 75O760 26.883 26.923 26.962 27.001 27.041 27.080 27.119 27.158 27.198 27.237 27.276 760770 27.276 27.316 27.355 27.394 27.433 27.473 27.512 27.551 27.591 27.630 27.669 770780 27.669 27.708 27.748 27.787 27.826 27.866 27.905 27.944 27.983 28.023 28.062 780790 28.062 28.101 28.140 28.180 28.219 28.258 28.297 28.337 28.376 28.415 28.455 790

800 28.455 28.494 28.533 28.572 28.612 28.651 28.690 28.729 28.769 28.808 28.847 800810 28.847 28.886 28.926 28.965 29.004 29.043 29.083 29.122 29.161 29.200 29.239 810820 29.239 29.279 29.318 29.357 29.396 29.436 29.475 29.514 29.553 29.592 29.632 820830 29.632 29.671 29.710 29.749 29.789 29.828 29.867 29.906 29.945 29.985 30.024 830840 30.024 30.063 30.102 30.141 30.181 30.220 30.259 30.298 30.337 30.376 30.416 840

850 30.416 30.455 30.494 30.533 30.572 30.611 30.651 30.690 30.729 30.768 30.807 850860 30.807 30.846 30.886 30.925 30.964 31.003 31.042 31.081 31.120 31.160 31.199 860870 31.199 31.238 31.277 31.316 31.355 31.394 31.433 31.473 31.512 31.551 31.590 870880 31.590 31.629 31.668 31.707 31.746 31.785 31.824 31.863 31.903 31.942 31.981 880890 31.981 32.020 32.059 32.098 32.137 32.176 32.215 32.254 32.293 32.332 32.371 890

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 450 to 2372°F– 270 to 1300°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 2.2°C or 0.75% Above 0°C2.2°C or 2.0% Below 0°CSpecial: 1.1°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Alternative to Type K; More Stable at High TemperaturesTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°C NN

°C -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

ThermocoupleGrade

Nickel-14.2%Chromium-1.4% Silicon

vs.Nickel-4.4% Silicon-

0.1% Magnesium

ExtensionGrade

+–

+–



Z-215


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

900 32.371 32.410 32.449 32.488 32.527 32.566 32.605 32.644 32.683 32.722 32.761 900910 32.761 32.800 32.839 32.878 32.917 32.956 32.995 33.034 33.073 33.112 33.151 910920 33.151 33.190 33.229 33.268 33.307 33.346 33.385 33.424 33.463 33.502 33.541 920930 33.541 33.580 33.619 33.658 33.697 33.736 33.774 33.813 33.852 33.891 33.930 930940 33.930 33.969 34.008 34.047 34.086 34.124 34.163 34.202 34.241 34.280 34.319 940

950 34.319 34.358 34.396 34.435 34.474 34.513 34.552 34.591 34.629 34.668 34.707 950960 34.707 34.746 34.785 34.823 34.862 34.901 34.940 34.979 35.017 35.056 35.095 960970 35.095 35.134 35.172 35.211 35.250 35.289 35.327 35.366 35.405 35.444 35.482 970980 35.482 35.521 35.560 35.598 35.637 35.676 35.714 35.753 35.792 35.831 35.889 980990 35.869 35.908 35.946 35.985 36.024 36.062 36.101 36.140 36.178 36.217 36.256 990

1000 36.256 38.294 36.333 36.371 36.410 36.449 36.487 36.526 36.564 36.603 36.641 10001010 36.841 36.680 36.718 38.757 38.796 38.834 36.873 36.911 36.950 36.988 37.027 10101020 37.027 37.065 37.104 37.142 37.181 37.219 37.258 37.296 37.334 37.373 37.411 10201030 37.411 37.450 37.488 37.527 37.565 37.603 37.642 37.680 37.719 37.757 37.795 10301040 37.795 37.834 37.872 37.911 37.949 37.987 38.026 38.064 38.102 38.141 38.179 1040

1050 38.179 38.217 38.256 38.294 38.332 38.370 38.409 38.447 38.485 38.524 38.562 10501060 38.562 38.600 38.638 38.677 38.715 38.753 38.791 38.829 38.868 38.906 38.944 10601070 38.944 38.982 39.020 39.059 39.097 39.135 39.173 39.211 39.249 39.287 39.326 10701080 39.326 39.364 39.402 39.440 39.478 39.516 30.554 39.592 39.630 39.668 39.706 10001090 39.708 39.744 39.783 39.821 39.859 39.897 39.935 39.973 40.011 40.049 40.087 1090

1100 40.087 40.125 40.163 40.201 40.238 40.276 40.314 40.352 40.390 40.428 40.466 11001110 40.466 40.504 40.542 40.580 40.818 40.655 40.693 40.731 40.769 40.807 40.845 11101120 40.845 40.883 40.920 40.958 40.996 41.034 41.072 41.109 41.147 41.185 41.223 11201130 41.223 41.260 41.298 41.336 41.374 41.411 41.449 41.487 41.525 41.562 41.6OO 11301140 41.600 41.638 41.675 41.713 41.751 41.788 41.826 41.864 41.901 41.939 41.976 1140

1150 41.976 42.014 42.052 42.089 42.127 42.164 42.202 42.239 42.277 42.314 42.352 11501160 42.352 42.390 42.427 42.465 42.502 42.540 42.577 42.614 42.652 42.689 42.727 11601170 42.727 42.764 42.802 42.839 42.877 42.914 42.951 42.989 43.026 43.064 43.101 11701180 43.101 43.138 43.176 43.213 43.250 43.288 43.325 43.362 43.399 43.437 43.474 11901190 43.474 43.511 43.549 43.586 43.623 43.660 43.698 43.735 43.772 43.809 43.846 1190

1200 43.846 43.884 43.921 43.958 43.995 44.032 44.069 44.106 44.144 44.181 44.218 19001210 44.218 44.255 44.292 44.329 44.366 44.403 44.440 44.477 44.514 44.551 44.551 12101220 44.588 44.625 44.662 44.699 44.736 44.773 44.810 44.847 44.884 44.921 44.958 12201230 44.958 44.995 45.032 45.069 45.105 45.142 45.179 45.216 45.253 45.290 45.326 12301240 45.326 45.363 45.400 45.437 45.474 45.510 45.547 45.584 45.621 45.657 45.694 1240

1250 45.694 45.731 45.767 45.804 45.841 45.877 45.914 45.951 45.987 46.024 46.080 12501260 46.060 46.097 46.133 46.170 46.207 46.243 46.280 46.316 46.353 46.389 46.425 12601270 46.425 46.462 46.498 46.535 46.571 46.608 46.844 46.880 46.717 46.753 46.789 12701280 46.789 46.826 46.862 46.898 46.935 46.971 47.007 47.043 47.079 47.116 47.152 12801290 47.152 47.188 47.224 47.260 47.296 47.333 47.369 47.405 47.441 47.477 47.513 1290

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 450 to 2372°F– 270 to 1300°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 2.2°C or 0.75% Above 0°C2.2°C or 2.0% Below 0°CSpecial: 1.1°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Alternative to Type K; More Stable at High TemperaturesTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°CNN

ThermocoupleGrade



0.1% Magnesium

ExtensionGrade

+–

+–



Z-216

Z


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

-340 -8.095 -8.085 -8.074 -8.063 -8.052 -8.041 -8.030 -340-330 -8.030 -8.019 -8.008 -7.996 -7.985 -7.973 -7.962 -7.950 -7.938 -7.927 -7.915 -330-320 -7.915 -7.903 -7.890 -7.878 -7.866 -7.854 -7.841 -7.829 -7.816 -7.804 -7.791 -320-310 -7.791 -7.778 -7.765 -7.752 -7.739 -7.726 -7.713 -7.699 -7.686 -7.672 -7.659 -310-300 -7.659 -7.645 -7.632 -7.618 -7.604 -7.590 -7.576 -7.562 -7.548 -7.534 -7.519 -300

-290 -7.519 -7.505 -7.491 -7.476 -7.462 -7.447 -7.432 -7.417 -7.403 -7.388 -7.373 -290-280 -7.373 -7.357 -7.342 -7.327 -7.312 -7.296 -7.281 -7.265 -7.250 -7.234 -7.219 -280-270 -7.219 -7.203 -7.187 -7.171 -7.155 -7.139 -7.123 -7.107 -7.090 -7.074 -7.058 -270-260 -7.058 -7.041 -7.025 -7.008 -6.991 -6.975 -6.958 -6.941 -6.924 -6.907 -6.890 -260-250 -6.890 -6.873 -6.856 -6.839 -6.821 -6.804 -6.787 -6.769 -6.752 -6.734 -6.716 -250

-240 -6.716 -6.699 -6.681 -6.663 -6.645 -6.627 -6.609 -6.591 -6.573 -6.555 -6.536 -240-230 -6.536 -6.518 -6.500 -6.481 -6.463 -6.444 -6.426 -6.407 -6.388 -6.370 -6.351 -230-220 -6.351 -6.332 -6.313 -6.294 -6.275 -6.256 -6.236 -6.217 -6.198 -6.179 -6.159 -220-210 -6.159 -6.140 -6.120 -6.101 -6.081 -6.061 -6.042 -6.022 -6.002 -5.982 -5.962 -210-200 -5.962 -5.942 -5.922 -5.902 -5.882 -5.862 -5.842 -5.821 -5.801 -5.781 -5.760 -200

-190 -5.760 -5.740 -5.719 -5.699 -5.678 -5.657 -5.637 -5.616 -5.595 -5.574 -5.553 -190-180 -5.553 -5.532 -5.511 -5.490 -5.469 -5.448 -5.426 -5.405 -5.384 -5.363 -5.341 -180-170 -5.341 -5.320 -5.298 -5.277 -5.255 -5.233 -5.212 -5.190 -5.168 -5.146 -5.125 -170-160 -5.125 -5.103 -5.081 -5.059 -5.037 -5.015 -4.992 -4.970 -4.948 -4.926 -4.903 -160-150 -4.903 -4.881 -4.859 -4.836 -4.814 -4.791 -4.769 -4.746 -4.724 -4.701 -4.678 -150

-140 -4.678 -4.655 -4.633 -4.610 -4.587 -4.564 -4.541 -4.518 -4.495 -4.472 -4.449 -140-130 -4.449 -4.425 -4.402 -4.379 -4.356 -4.332 -4.309 -4.286 -4.262 -4.239 -4.215 -130-120 -4.215 -4.192 -4.168 -4.144 -4.121 -4.097 -4.073 -4.050 -4.026 -4.002 -3.978 -120-110 -3.978 -3.954 -3.930 -3.906 -3.882 -3.858 -3.834 -3.810 -3.786 -3.761 -3.737 -110-100 -3.737 -3.713 -3.688 -3.664 -3.640 -3.615 -3.591 -3.566 -3.542 -3.517 -3.493 -100

-90 -3.493 -3.468 -3.443 -3.419 -3.394 -3.369 -3.344 -3.320 -3.295 -3.270 -3.245 -90-80 -3.245 -3.220 -3.195 -3.170 -3.145 -3.120 -3.095 -3.070 -3.044 -3.019 -2.994 -80-70 -2.994 -2.969 -2.943 -2.918 -2.893 -2.867 -2.842 -2.817 -2.791 -2.766 -2.740 -70-60 -2.740 -2.714 -2.689 -2.663 -2.638 -2.612 -2.586 -2.560 -2.535 -2.509 -2.483 -60

- 50 -2.483 -2.457 -2.431 -2.405 -2.379 -2.353 -2.327 -2.301 -2.275 -2.249 -2.223 -50

-40 -2.223 -2.197 -2.171 -2.145 -2.118 -2.092 -2.066 -2.040 -2.013 -1.987 -1.961 -40-30 -1.961 -1.934 -1.908 -1.881 -1.855 -1.828 -1.802 -1.775 -1.749 -1.722 -1.695 -30-20 -1.695 -1.669 -1.642 -1.615 -1.589 -1.562 -1.535 -1.508 -1.482 -1.455 -1.428 -20-10 -1.428 -1.401 -1.374 -1.347 -1.320 -1.293 -1.266 -1.239 -1.212 -1.185 -1.158 -10

0 -1.158 -1.131 -1.104 -1.076 -1.049 -1.022 -0.995 -0.967 -0.940 -0.913 -0.886 0

0 -0.886 -0.858 -0.831 -0.803 -0.776 -0.749 -0.721 -0.694 -0.666 -0.639 -0.611 010 -0.611 -0.583 -0.556 -0.528 -0.501 -0.473 -0.445 -0.418 -0.390 -0.362 -0.334 1020 -0.334 -0.307 -0.279 -0.251 -0.223 -0.195 -0.168 -0.140 -0.112 -0.084 -0.056 2030 -0.056 -0.028 0.000 0.028 0.056 0.084 0.112 0.140 0.168 0.196 0.225 3040 0.225 0.253 0.281 0.309 0.337 0.365 0.394 0.422 0.450 0.478 0.507 40

50 0.507 0.535 0.563 0.592 0.620 0.649 0.677 0.705 0.734 0.762 0.791 5060 0.791 0.819 0.848 0.876 0.905 0.933 0.962 0.991 1.019 1.048 1.076 6070 1.076 1.105 1.134 1.162 1.191 1.220 1.249 1.277 1.306 1.335 1.364 7080 1.364 1.392 1.421 1.450 1.479 1.508 1.537 1.566 1.594 1.623 1.652 8090 1.652 1.681 1.710 1.739 1.768 1.797 1.826 1.855 1.884 1.913 1.942 90

100 1.942 1.972 2.001 2.030 2.059 2.088 2.117 2.146 2.175 2.205 2.234 100110 2.234 2.263 2.292 2.322 2.351 2.380 2.409 2.439 2.468 2.497 2.527 110120 2.527 2.556 2.585 2.615 2.644 2.673 2.703 2.732 2.762 2.791 2.821 120130 2.821 2.850 2.880 2.909 2.938 2.968 2.997 3.027 3.057 3.086 3.116 130140 3.116 3.145 3.175 3.204 3.234 3.264 3.293 3.323 3.353 3.382 3.412 140

150 3.412 3.442 3.471 3.501 3.531 3.560 3.590 3.620 3.650 3.679 3.709 150160 3.709 3.739 3.769 3.798 3.828 3.858 3.888 3.918 3.948 3.977 4.007 160170 4.007 4.037 4.067 4.097 4.127 4.157 4.187 4.217 4.246 4.276 4.306 170180 4.306 4.336 4.366 4.396 4.426 4.456 4.486 4.516 4.546 4.576 4.606 180190 4.606 4.636 4.666 4.696 4.726 4.757 4.787 4.817 4.847 4.877 4.907 190

200 4.907 4.937 4.967 4.997 5.028 5.058 5.088 5.118 5.148 5.178 5.209 200210 5.209 5.239 5.269 5.299 5.329 5.360 5.390 5.420 5.450 5.480 5.511 210220 5.511 5.541 5.571 5.602 5.632 5.662 5.692 5.723 5.753 5.783 5.814 220230 5.814 5.844 5.874 5.905 5.935 5.965 5.996 6.026 6.056 6.087 6.117 230240 6.117 6.147 6.178 6.208 6.239 6.269 6.299 6.330 6.360 6.391 6.421 240

250 6.421 6.452 6.482 6.512 6.543 6.573 6.604 6.634 6.665 6.695 6.726 250260 6.726 6.756 6.787 6.817 6.848 6.878 6.909 6.939 6.970 7.000 7.031 260270 7.031 7.061 7.092 7.122 7.153 7.184 7.214 7.245 7.275 7.306 7.336 270280 7.336 7.367 7.398 7.428 7.459 7.489 7.520 7.550 7.581 7.612 7.642 280290 7.642 7.673 7.704 7.734 7.765 7.795 7.826 7.857 7.887 7.918 7.949 290

300 7.949 7.979 8.010 8.041 8.071 8.102 8.133 8.163 8.194 8.225 8.255 300310 8.255 8.286 8.317 8.347 8.378 8.409 8.439 8.470 8.501 8.532 8.562 310320 8.562 8.593 8.624 8.654 8.685 8.716 8.747 8.777 8.808 8.839 8.869 320330 8.869 8.900 8.931 8.962 8.992 9.023 9.054 9.085 9.115 9.146 9.177 330340 9.177 9.208 9.238 9.269 9.300 9.331 9.362 9.392 9.423 9.454 9.485 340

350 9.485 9.515 9.546 9.577 9.608 9.639 9.669 9.700 9.731 9.762 9.793 350360 9.793 9.823 9.854 9.885 9.916 9.947 9.977 10.008 10.039 10.070 10.101 360370 10.101 10.131 10.162 10.193 10.224 10.255 10.285 10.316 10.347 10.378 10.409 370380 10.409 10.440 10.470 10.501 10.532 10.563 10.594 10.625 10.655 10.686 10.717 380390 10.717 10.748 10.779 10.810 10.840 10.871 10.902 10.933 10.964 10.995 11.025 390

400 11.025 11.056 11.087 11.118 11.149 11.180 11.211 11.241 11.272 11.303 11.334 400410 11.334 11.365 11.396 11.426 11.457 11.488 11.519 11.550 11.581 11.612 11.642 410420 11.642 11.673 11.704 11.735 11.766 11.797 11.828 11.858 11.889 11.920 11.951 420430 11.951 11.982 12.013 12.044 12.074 12.105 12.136 12.167 12.198 12.229 12.260 430440 12.260 12.290 12.321 12.352 12.383 12.414 12.445 12.476 12.506 12.537 12.568 440

450 12.568 12.599 12.630 12.661 12.691 12.722 12.753 12.784 12.815 12.846 12.877 450460 12.877 12.907 12.938 12.969 13.000 13.031 13.062 13.093 13.123 13.154 13.185 460470 13.185 13.216 13.247 13.278 13.308 13.339 13.370 13.401 13.432 13.463 13.494 470480 13.494 13.524 13.555 13.586 13.617 13.648 13.679 13.709 13.740 13.771 13.802 480490 13.802 13.833 13.864 13.894 13.925 13.956 13.987 14.018 14.049 14.079 14.110 490

500 14.110 14.141 14.172 14.203 14.233 14.264 14.295 14.326 14.357 14.388 14.418 500510 14.418 14.449 14.480 14.511 14.542 14.573 14.603 14.634 14.665 14.696 14.727 510520 14.727 14.757 14.788 14.819 14.850 14.881 14.911 14.942 14.973 15.004 15.035 520530 15.035 15.065 15.096 15.127 15.158 15.189 15.219 15.250 15.281 15.312 15.343 530540 15.343 15.373 15.404 15.435 15.466 15.496 15.527 15.558 15.589 15.620 15.650 540

550 15.650 15.681 15.712 15.743 15.773 15.804 15.835 15.866 15.897 15.927 15.958 550560 15.958 15.989 16.020 16.050 16.081 16.112 16.143 16.173 16.204 16.235 16.266 560570 16.266 16.296 16.327 16.358 16.389 16.419 16.450 16.481 16.512 16.542 16.573 570580 16.573 16.604 16.635 16.665 16.696 16.727 16.758 16.788 16.819 16.850 16.881 580590 16.881 16.911 16.942 16.973 17.003 17.034 17.065 17.096 17.126 17.157 17.188 590

600 17.188 17.219 17.249 17.280 17.311 17.341 17.372 17.403 17.434 17.464 17.495 600610 17.495 17.526 17.556 17.587 17.618 17.649 17.679 17.710 17.741 17.771 17.802 610620 17.802 17.833 17.863 17.894 17.925 17.955 17.986 18.017 18.048 18.078 18.109 620630 18.109 18.140 18.170 18.201 18.232 18.262 18.293 18.324 18.354 18.385 18.416 630640 18.416 18.446 18.477 18.508 18.538 18.569 18.600 18.630 18.661 18.692 18.722 640

650 18.722 18.753 18.784 18.814 18.845 18.876 18.906 18.937 18.968 18.998 19.029 650660 19.029 19.060 19.090 19.121 19.152 19.182 19.213 19.244 19.274 19.305 19.336 660670 19.336 19.366 19.397 19.428 19.458 19.489 19.520 19.550 19.581 19.612 19.642 670680 19.642 19.673 19.704 19.734 19.765 19.795 19.826 19.857 19.887 19.918 19.949 680690 19.949 19.979 20.010 20.041 20.071 20.102 20.132 20.163 20.194 20.224 20.255 690

700 20.255 20.286 20.316 20.347 20.378 20.408 20.439 20.469 20.500 20.531 20.561 700710 20.561 20.592 20.623 20.653 20.684 20.715 20.745 20.776 20.806 20.837 20.868 710720 20.868 20.898 20.929 20.960 20.990 21.021 21.052 21.082 21.113 21.143 21.174 720730 21.174 21.205 21.235 21.266 21.297 21.327 21.358 21.389 21.419 21.450 21.480 730740 21.480 21.511 21.542 21.572 21.603 21.634 21.664 21.695 21.726 21.756 21.787 740

750 21.787 21.817 21.848 21.879 21.909 21.940 21.971 22.001 22.032 22.063 22.093 750760 22.093 22.124 22.154 22.185 22.216 22.246 22.277 22.308 22.338 22.369 22.400 760770 22.400 22.430 22.461 22.492 22.522 22.553 22.584 22.614 22.645 22.676 22.706 770780 22.706 22.737 22.768 22.798 22.829 22.860 22.890 22.921 22.952 22.982 23.013 780790 23.013 23.044 23.074 23.105 23.136 23.166 23.197 23.228 23.258 23.289 23.320 790

800 23.320 23.350 23.381 23.412 23.442 23.473 23.504 23.535 23.565 23.596 23.627 800810 23.627 23.657 23.688 23.719 23.749 23.780 23.811 23.842 23.872 23.903 23.934 810820 23.934 23.964 23.995 24.026 24.057 24.087 24.118 24.149 24.180 24.210 24.241 820830 24.241 24.272 24.303 24.333 24.364 24.395 24.426 24.456 24.487 24.518 24.549 830840 24.549 24.579 24.610 24.641 24.672 24.702 24.733 24.764 24.795 24.826 24.856 840

850 24.856 24.887 24.918 24.949 24.979 25.010 25.041 25.072 25.103 25.134 25.164 850860 25.164 25.195 25.226 25.257 25.288 25.318 25.349 25.380 25.411 25.442 25.473 860870 25.473 25.504 25.534 25.565 25.596 25.627 25.658 25.689 25.720 25.750 25.781 870880 25.781 25.812 25.843 25.874 25.905 25.936 25.967 25.998 26.028 26.059 26.090 880890 26.090 26.121 26.152 26.183 26.214 26.245 26.276 26.307 26.338 26.369 26.400 890

900 26.400 26.431 26.462 26.493 26.524 26.555 26.586 26.617 26.648 26.679 26.710 900910 26.710 26.741 26.772 26.803 26.834 26.865 26.896 26.927 26.958 26.989 27.020 910920 27.020 27.051 27.082 27.113 27.144 27.175 27.206 27.237 27.268 27.299 27.330 920930 27.330 27.362 27.393 27.424 27.455 27.486 27.517 27.548 27.579 27.610 27.642 930940 27.642 27.673 27.704 27.735 27.766 27.797 27.829 27.860 27.891 27.922 27.953 940

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 1382°F0 to 750°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 2.2°C or 0.75%Special: 1.1°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Reducing, Vacuum, Inert; Limited Use inOxidizing at High Temperatures; Not Recommended for Low TemperaturesTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°F JJ

°F -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

ThermocoupleGrade

Ironvs.

Copper-Nickel

ExtensionGrade

+–

+–


+–


Z-217


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

950 27.953 27.985 28.016 28.047 28.078 28.109 28.141 28.172 28.203 28.234 28.266 950960 28.266 28.297 28.328 28.359 28.391 28.422 28.453 28.485 28.516 28.547 28.579 960970 28.579 28.610 28.641 28.672 28.704 28.735 28.767 28.798 28.829 28.861 28.892 970980 28.892 28.923 28.955 28.986 29.018 29.049 29.080 29.112 29.143 29.175 29.206 980990 29.206 29.238 29.269 29.301 29.332 29.363 29.395 29.426 29.458 29.489 29.521 990

1000 29.521 29.552 29.584 29.616 29.647 29.679 29.710 29.742 29.773 29.805 29.836 10001010 29.836 29.868 29.900 29.931 29.963 29.995 30.026 30.058 30.089 30.121 30.153 10101020 30.153 30.184 30.216 30.248 30.279 30.311 30.343 30.375 30.406 30.438 30.470 10201030 30.470 30.502 30.533 30.565 30.597 30.629 30.660 30.692 30.724 30.756 30.788 10301040 30.788 30.819 30.851 30.883 30.915 30.947 30.979 31.011 31.043 31.074 31.106 1040

1050 31.106 31.138 31.170 31.202 31.234 31.266 31.298 31.330 31.362 31.394 31.426 10501060 31.426 31.458 31.490 31.522 31.554 31.586 31.618 31.650 31.682 31.714 31.746 10601070 31.746 31.778 31.811 31.843 31.875 31.907 31.939 31.971 32.003 32.035 32.068 10701080 32.068 32.100 32.132 32.164 32.196 32.229 32.261 32.293 32.325 32.358 32.390 10801090 32.390 32.422 32.455 32.487 32.519 32.551 32.584 32.616 32.648 32.681 32.713 1090

1100 32.713 32.746 32.778 32.810 32.843 32.875 32.908 32.940 32.973 33.005 33.037 11001110 33.037 33.070 33.102 33.135 33.167 33.200 33.232 33.265 33.298 33.330 33.363 11101120 33.363 33.395 33.428 33.460 33.493 33.526 33.558 33.591 33.624 33.656 33.689 11201130 33.689 33.722 33.754 33.787 33.820 33.853 33.885 33.918 33.951 33.984 34.016 11301140 34.016 34.049 34.082 34.115 34.148 34.180 34.213 34.246 34.279 34.312 34.345 1140

1150 34.345 34.378 34.411 34.444 34.476 34.509 34.542 34.575 34.608 34.641 34.674 11501160 34.674 34.707 34.740 34.773 34.806 34.840 34.873 34.906 34.939 34.972 35.005 11601170 35.005 35.038 35.071 35.104 35.138 35.171 35.204 35.237 35.270 35.304 35.337 11701180 35.337 35.370 35.403 35.437 35.470 35.503 35.536 35.570 35.603 35.636 35.670 11801190 35.670 35.703 35.736 35.770 35.803 35.837 35.870 35.903 35.937 35.970 36.004 1190

1200 36.004 36.037 36.071 36.104 36.138 36.171 36.205 36.238 36.272 36.305 36.339 12001210 36.339 36.373 36.406 36.440 36.473 36.507 36.541 36.574 36.608 36.642 36.675 12101220 36.675 36.709 36.743 36.777 36.810 36.844 36.878 36.912 36.945 36.979 37.013 12201230 37.013 37.047 37.081 37.114 37.148 37.182 37.216 37.250 37.284 37.318 37.352 12301240 37.352 37.386 37.420 37.454 37.488 37.522 37.556 37.590 37.624 37.658 37.692 1240

1250 37.692 37.726 37.760 37.794 37.828 37.862 37.896 37.930 37.964 37.999 38.033 12501260 38.033 38.067 38.101 38.135 38.169 38.204 38.238 38.272 38.306 38.341 38.375 12601270 38.375 38.409 38.444 38.478 38.512 38.546 38.581 38.615 38.650 38.684 38.718 12701280 38.718 38.753 38.787 38.822 38.856 38.890 38.925 38.959 38.994 39.028 39.063 12801290 39.063 39.097 39.132 39.166 39.201 39.235 39.270 39.305 39.339 39.374 39.408 1290

1300 39.408 39.443 39.478 39.512 39.547 39.582 39.616 39.651 39.686 39.720 39.755 13001310 39.755 39.790 39.825 39.859 39.894 39.929 39.964 39.998 40.033 40.068 40.103 13101320 40.103 40.138 40.173 40.207 40.242 40.277 40.312 40.347 40.382 40.417 40.452 13201330 40.452 40.487 40.522 40.556 40.591 40.626 40.661 40.696 40.731 40.766 40.801 13301340 40.801 40.836 40.872 40.907 40.942 40.977 41.012 41.047 41.082 41.117 41.152 1340

1350 41.152 41.187 41.222 41.258 41.293 41.328 41.363 41.398 41.433 41.469 41.504 13501360 41.504 41.539 41.574 41.610 41.645 41.680 41.715 41.751 41.786 41.821 41.856 13601370 41.856 41.892 41.927 41.962 41.998 42.033 42.068 42.104 42.139 42.174 42.210 13701380 42.210 42.245 42.281 42.316 42.351 42.387 42.422 42.458 42.493 42.528 42.564 13801390 42.564 42.599 42.635 42.670 42.706 42.741 42.777 42.812 42.848 42.883 42.919 1390

1400 42.919 42.954 42.990 43.025 43.061 43.096 43.132 43.167 43.203 43.239 43.274 14001410 43.274 43.310 43.346 43.381 43.417 43.452 43.488 43.524 43.559 43.595 43.631 14101420 43.631 43.667 43.702 43.738 43.774 43.809 43.845 43.881 43.917 43.953 43.988 14201430 43.988 44.024 44.060 44.096 44.131 44.167 44.203 44.239 44.275 44.310 44.346 14301440 44.346 44.382 44.418 44.454 44.490 44.525 44.561 44.597 44.633 44.669 44.705 1440

1450 44.705 44.741 44.777 44.812 44.848 44.884 44.920 44.956 44.992 45.028 45.064 14501460 45.064 45.099 45.135 45.171 45.207 45.243 45.279 45.315 45.351 45.387 45.423 14601470 45.423 45.458 45.494 45.530 45.566 45.602 45.638 45.674 45.710 45.746 45.782 14701480 45.782 45.818 45.853 45.889 45.925 45.961 45.997 46.033 46.069 46.105 46.141 14801490 46.141 46.177 46.212 46.248 46.284 46.320 46.356 46.392 46.428 46.464 46.500 1490

1500 46.500 46.535 46.571 46.607 46.643 46.679 46.715 46.751 46.786 46.822 46.858 15001510 46.858 46.894 46.930 46.966 47.001 47.037 47.073 47.109 47.145 47.181 47.216 15101520 47.216 47.252 47.288 47.324 47.359 47.395 47.431 47.467 47.503 47.538 47.574 15201530 47.574 47.610 47.646 47.681 47.717 47.753 47.788 47.824 47.860 47.896 47.931 15301540 47.931 47.967 48.003 48.038 48.074 48.110 48.145 48.181 48.217 48.252 48.288 1540

1550 48.288 48.324 48.359 48.395 48.430 48.466 48.502 48.537 48.573 48.608 48.644 15501560 48.644 48.679 48.715 48.750 48.786 48.822 48.857 48.893 48.928 48.964 48.999 15601570 48.999 49.034 49.070 49.105 49.141 49.176 49.212 49.247 49.283 49.318 49.353 15701580 49.353 49.389 49.424 49.460 49.495 49.530 49.566 49.601 49.636 49.672 49.707 15801590 49.707 49.742 49.778 49.813 49.848 49.883 49.919 49.954 49.989 50.024 50.060 1590

1600 50.060 50.095 50.130 50.165 50.200 50.235 50.271 50.306 50.341 50.376 50.411 16001610 50.411 50.446 50.481 50.517 50.552 50.587 50.622 50.657 50.692 50.727 50.762 16101620 50.762 50.797 50.832 50.867 50.902 50.937 50.972 51.007 51.042 51.077 51.112 16201630 51.112 51.147 51.181 51.216 51.251 51.286 51.321 51.356 51.391 51.425 51.460 16301640 51.460 51.495 51.530 51.565 51.599 51.634 51.669 51.704 51.738 51.773 51.808 1640

1650 51.808 51.843 51.877 51.912 51.947 51.981 52.016 52.051 52.085 52.120 52.154 16501660 52.154 52.189 52.224 52.258 52.293 52.327 52.362 52.396 52.431 52.465 52.500 16601670 52.500 52.534 52.569 52.603 52.638 52.672 52.707 52.741 52.776 52.810 52.844 16701680 52.844 52.879 52.913 52.947 52.982 53.016 53.050 53.085 53.119 53.153 53.188 16801690 53.188 53.222 53.256 53.290 53.325 53.359 53.393 53.427 53.462 53.496 53.530 1690

1700 53.530 53.564 53.598 53.632 53.667 53.701 53.735 53.769 53.803 53.837 53.871 17001710 53.871 53.905 53.939 53.973 54.007 54.041 54.075 54.109 54.143 54.177 54.211 17101720 54.211 54.245 54.279 54.313 54.347 54.381 54.415 54.449 54.483 54.516 54.550 17201730 54.550 54.584 54.618 54.652 54.686 54.719 54.753 54.787 54.821 54.855 54.888 17301740 54.888 54.922 54.956 54.990 55.023 55.057 55.091 55.124 55.158 55.192 55.225 1740

1750 55.225 55.259 55.293 55.326 55.360 55.393 55.427 55.461 55.494 55.528 55.561 17501760 55.561 55.595 55.628 55.662 55.695 55.729 55.762 55.796 55.829 55.863 55.896 17601770 55.896 55.930 55.963 55.997 56.030 56.063 56.097 56.130 56.164 56.197 56.230 17701780 56.230 56.264 56.297 56.330 56.364 56.397 56.430 56.464 56.497 56.530 56.564 17801790 56.564 56.597 56.630 56.663 56.697 56.730 56.763 56.796 56.829 56.863 56.896 1790

1800 56.896 56.929 56.962 56.995 57.028 57.062 57.095 57.128 57.161 57.194 57.227 18001810 57.227 57.260 57.293 57.326 57.360 57.393 57.426 57.459 57.492 57.525 57.558 18101820 57.558 57.591 57.624 57.657 57.690 57.723 57.756 57.789 57.822 57.855 57.888 18201830 57.888 57.920 57.953 57.986 58.019 58.052 58.085 58.118 58.151 58.184 58.217 18301840 58.217 58.249 58.282 58.315 58.348 58.381 58.414 58.446 58.479 58.512 58.545 1840

1850 58.545 58.578 58.610 58.643 58.676 58.709 58.741 58.774 58.807 58.840 58.872 18501860 58.872 58.905 58.938 58.971 59.003 59.036 59.069 59.101 59.134 59.167 59.199 18601870 59.199 59.232 59.265 59.297 59.330 59.363 59.395 59.428 59.460 59.493 59.526 18701880 59.526 59.558 59.591 59.623 59.656 59.689 59.721 59.754 59.786 59.819 59.851 18801890 59.851 59.884 59.916 59.949 59.982 60.014 60.047 60.079 60.112 60.144 60.177 1890

1900 60.177 60.209 60.242 60.274 60.307 60.339 60.371 60.404 60.436 60.469 60.501 19001910 60.501 60.534 60.566 60.599 60.631 60.663 60.696 60.728 60.761 60.793 60.826 19101920 60.826 60.858 60.890 60.923 60.955 60.987 61.020 61.052 61.085 61.117 61.149 19201930 61.149 61.182 61.214 61.246 61.279 61.311 61.343 61.376 61.408 61.440 61.473 19301940 61.473 61.505 61.537 61.570 61.602 61.634 61.667 61.699 61.731 61.763 61.796 1940

1950 61.796 61.828 61.860 61.893 61.925 61.957 61.989 62.022 62.054 62.086 62.118 19501960 62.118 62.151 62.183 62.215 62.247 62.280 62.312 62.344 62.376 62.409 62.441 19601970 62.441 62.473 62.505 62.537 62.570 62.602 62.634 62.666 62.699 62.731 62.763 19701980 62.763 62.795 62.827 62.860 62.892 62.924 62.956 62.988 63.020 63.053 63.085 19801990 63.085 63.117 63.149 63.181 63.214 63.246 63.278 63.310 63.342 63.374 63.406 1990

2000 63.406 63.439 63.471 63.503 63.535 63.567 63.599 63.632 63.664 63.696 63.728 20002010 63.728 63.760 63.792 63.824 63.856 63.889 63.921 63.953 63.985 64.017 64.049 20102020 64.049 64.081 64.113 64.146 64.178 64.210 64.242 64.274 64.306 64.338 64.370 20202030 64.370 64.402 64.435 64.467 64.499 64.531 64.563 64.595 64.627 64.659 64.691 20302040 64.691 64.723 64.756 64.788 64.820 64.852 64.884 64.916 64.948 64.980 65.012 2040

2050 65.012 65.044 65.076 65.109 65.141 65.173 65.205 65.237 65.269 65.301 65.333 20502060 65.333 65.365 65.397 65.429 65.461 65.493 65.525 65.557 65.590 65.622 65.654 20602070 65.654 65.686 65.718 65.750 65.782 65.814 65.846 65.878 65.910 65.942 65.974 20702080 65.974 66.006 66.038 66.070 66.102 66.134 66.166 66.199 66.231 66.263 66.295 20802090 66.295 66.327 66.359 66.391 66.423 66.455 66.487 66.519 66.551 66.583 66.615 2090

2100 66.615 66.647 66.679 66.711 66.743 66.775 66.807 66.839 66.871 66.903 66.935 21002110 66.935 66.967 66.999 67.031 67.063 67.095 67.127 67.159 67.191 67.223 67.255 21102120 67.255 67.287 67.319 67.351 67.383 67.415 67.447 67.479 67.511 67.543 67.575 21202130 67.575 67.607 67.639 67.671 67.703 67.735 67.767 67.799 67.831 67.863 67.895 21302140 67.895 67.927 67.959 67.991 68.023 68.055 68.087 68.119 68.150 68.182 68.214 2140

2150 68.214 68.246 68.278 68.310 68.342 68.374 68.406 68.438 68.470 68.502 68.534 21502160 68.534 68.566 68.597 68.629 68.661 68.693 68.725 68.757 68.789 68.821 68.853 21602170 68.853 68.884 68.916 68.948 68.980 69.012 69.044 69.076 69.108 69.139 69.171 21702180 69.171 69.203 69.235 69.267 69.299 69.330 69.362 69.394 69.426 69.458 69.490 21802190 69.490 69.521 69.553 2190

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 1382°F0 to 750°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 2.2°C or 0.75%Special: 1.1°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Reducing, Vacuum, Inert; Limited Use inOxidizing at High Temperatures; Not Recommended for Low TemperaturesTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°F JJ

ThermocoupleGrade

Ironvs.

Copper-Nickel

ExtensionGrade

+–

+–



Z-218

Z


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

-450 -6.458 -6.457 -6.457 -6.456 -6.456 -450

-440 -6.456 -6.455 -6.454 -6.454 -6.453 -6.452 -6.451 -6.450 -6.449 -6.448 -6.446 -440-430 -6.446 -6.445 -6.444 -6.443 -6.441 -6.440 -6.438 -6.436 -6.435 -6.433 -6.431 -430-420 -6.431 -6.429 -6.427 -6.425 -6.423 -6.421 -6.419 -6.416 -6.414 -6.411 -6.409 -420-410 -6.409 -6.406 -6.404 -6.401 -6.398 -6.395 -6.392 -6.389 -6.386 -6.383 -6.380 -410-400 -6.380 -6.377 -6.373 -6.370 -6.366 -6.363 -6.359 -6.355 -6.352 -6.348 -6.344 -400

-390 -6.344 -6.340 -6.336 -6.332 -6.328 -6.323 -6.319 -6.315 -6.310 -6.306 -6.301 -390-380 -6.301 -6.296 -6.292 -6.287 -6.282 -6.277 -6.272 -6.267 -6.262 -6.257 -6.251 -380-370 -6.251 -6.246 -6.241 -6.235 -6.230 -6.224 -6.218 -6.213 -6.207 -6.201 -6.195 -370-360 -6.195 -6.189 -6.183 -6.177 -6.171 -6.165 -6.158 -6.152 -6.146 -6.139 -6.133 -360-350 -6.133 -6.126 -6.119 -6.113 -6.106 -6.099 -6.092 -6.085 -6.078 -6.071 -6.064 -350

-340 -6.064 -6.057 -6.049 -6.042 -6.035 -6.027 -6.020 -6.012 -6.004 -5.997 -5.989 -340-330 -5.989 -5.981 -5.973 -5.965 -5.957 -5.949 -5.941 -5.933 -5.925 -5.917 -5.908 -330-320 -5.908 -5.900 -5.891 -5.883 -5.874 -5.866 -5.857 -5.848 -5.840 -5.831 -5.822 -320-310 -5.822 -5.813 -5.804 -5.795 -5.786 -5.776 -5.767 -5.758 -5.749 -5.739 -5.730 -310-300 -5.730 -5.720 -5.711 -5.701 -5.691 -5.682 -5.672 -5.662 -5.652 -5.642 -5.632 -300

-290 -5.632 -5.622 -5.612 -5.602 -5.592 -5.581 -5.571 -5.561 -5.550 -5.540 -5.529 -290-280 -5.529 -5.519 -5.508 -5.497 -5.487 -5.476 -5.465 -5.454 -5.443 -5.432 -5.421 -280-270 -5.421 -5.410 -5.399 -5.388 -5.377 -5.365 -5.354 -5.343 -5.331 -5.320 -5.308 -270-260 -5.308 -5.296 -5.285 -5.273 -5.261 -5.250 -5.238 -5.226 -5.214 -5.202 -5.190 -260-250 -5.190 -5.178 -5.166 -5.153 -5.141 -5.129 -5.117 -5.104 -5.092 -5.079 -5.067 -250

-240 -5.067 -5.054 -5.042 -5.029 -5.016 -5.003 -4.991 -4.978 -4.965 -4.952 -4.939 -240-230 -4.939 -4.926 -4.913 -4.900 -4.886 -4.873 -4.860 -4.847 -4.833 -4.820 -4.806 -230-220 -4.806 -4.793 -4.779 -4.766 -4.752 -4.738 -4.724 -4.711 -4.697 -4.683 -4.669 -220-210 -4.669 -4.655 -4.641 -4.627 -4.613 -4.599 -4.584 -4.570 -4.556 -4.542 -4.527 -210-200 -4.527 -4.513 -4.498 -4.484 -4.469 -4.455 -4.440 -4.425 -4.411 -4.396 -4.381 -200

-190 -4.381 -4.366 -4.351 -4.336 -4.321 -4.306 -4.291 -4.276 -4.261 -4.246 -4.231 -190-180 -4.231 -4.215 -4.200 -4.185 -4.169 -4.154 -4.138 -4.123 -4.107 -4.091 -4.076 -180-170 -4.076 -4.060 -4.044 -4.029 -4.013 -3.997 -3.981 -3.965 -3.949 -3.933 -3.917 -170-160 -3.917 -3.901 -3.885 -3.869 -3.852 -3.836 -3.820 -3.803 -3.787 -3.771 -3.754 -160-150 -3.754 -3.738 -3.721 -3.705 -3.688 -3.671 -3.655 -3.638 -3.621 -3.604 -3.587 -150

-140 -3.587 -3.571 -3.554 -3.537 -3.520 -3.503 -3.486 -3.468 -3.451 -3.434 -3.417 -140-130 -3.417 -3.400 -3.382 -3.365 -3.348 -3.330 -3.313 -3.295 -3.278 -3.260 -3.243 -130-120 -3.243 -3.225 -3.207 -3.190 -3.172 -3.154 -3.136 -3.119 -3.101 -3.083 -3.065 -120-110 -3.065 -3.047 -3.029 -3.011 -2.993 -2.975 -2.957 -2.938 -2.920 -2.902 -2.884 -110-100 -2.884 -2.865 -2.847 -2.829 -2.810 -2.792 -2.773 -2.755 -2.736 -2.718 -2.699 -100

-90 -2.699 -2.680 -2.662 -2.643 -2.624 -2.605 -2.587 -2.568 -2.549 -2.530 -2.511 -90-80 -2.511 -2.492 -2.473 -2.454 -2.435 -2.416 -2.397 -2.378 -2.359 -2.339 -2.320 -80-70 -2.320 -2.301 -2.282 -2.262 -2.243 -2.223 -2.204 -2.185 -2.165 -2.146 -2.126 -70-60 -2.126 -2.106 -2.087 -2.067 -2.048 -2.028 -2.008 -1.988 -1.969 -1.949 -1.929 -60-50 -1.929 -1.909 -1.889 -1.869 -1.850 -1.830 -1.810 -1.790 -1.770 -1.749 -1.729 -50

-40 -1.729 -1.709 -1.689 -1.669 -1.649 -1.628 -1.608 -1.588 -1.568 -1.547 -1.527 -40-30 -1.527 -1.507 -1.486 -1.466 -1.445 -1.425 -1.404 -1.384 -1.363 -1.343 -1.322 -30-20 -1.322 -1.301 -1.281 -1.260 -1.239 -1.218 -1.198 -1.177 -1.156 -1.135 -1.114 -20-10 -1.114 -1.094 -1.073 -1.052 -1.031 -1.010 -0.989 -0.968 -0.947 -0.926 -0.905 -10

0 -0.905 -0.883 -0.862 -0.841 -0.820 -0.799 -0.778 -0.756 -0.735 -0.714 -0.692 0

0 -0.692 -0.671 -0.650 -0.628 -0.607 -0.586 -0.564 -0.543 -0.521 -0.500 -0.478 010 -0.478 -0.457 -0.435 -0.413 -0.392 -0.370 -0.349 -0.327 -0.305 -0.284 -0.262 1020 -0.262 -0.240 -0.218 -0.197 -0.175 -0.153 -0.131 -0.109 -0.088 -0.066 -0.044 2030 -0.044 -0.022 0.000 0.022 0.044 0.066 0.088 0.110 0.132 0.154 0.176 3040 0.176 0.198 0.220 0.242 0.264 0.286 0.308 0.330 0.353 0.375 0.397 40

50 0.397 0.419 0.441 0.463 0.486 0.508 0.530 0.552 0.575 0.597 0.619 5060 0.619 0.642 0.664 0.686 0.709 0.731 0.753 0.776 0.798 0.821 0.843 6070 0.843 0.865 0.888 0.910 0.933 0.955 0.978 1.000 1.023 1.045 1.068 7080 1.068 1.090 1.113 1.136 1.158 1.181 1.203 1.226 1.249 1.271 1.294 8090 1.294 1.316 1.339 1.362 1.384 1.407 1.430 1.453 1.475 1.498 1.521 90

100 1.521 1.543 1.566 1.589 1.612 1.635 1.657 1.680 1.703 1.726 1.749 100110 1.749 1.771 1.794 1.817 1.840 1.863 1.886 1.909 1.931 1.954 1.977 110120 1.977 2.000 2.023 2.046 2.069 2.092 2.115 2.138 2.161 2.184 2.207 120130 2.207 2.230 2.253 2.276 2.298 2.321 2.344 2.367 2.390 2.413 2.436 130140 2.436 2.459 2.483 2.506 2.529 2.552 2.575 2.598 2.621 2.644 2.667 140

150 2.667 2.690 2.713 2.736 2.759 2.782 2.805 2.828 2.851 2.874 2.897 150160 2.897 2.920 2.944 2.967 2.990 3.013 3.036 3.059 3.082 3.105 3.128 160170 3.128 3.151 3.174 3.197 3.220 3.244 3.267 3.290 3.313 3.336 3.359 170180 3.359 3.382 3.405 3.428 3.451 3.474 3.497 3.520 3.544 3.567 3.590 180190 3.590 3.613 3.636 3.659 3.682 3.705 3.728 3.751 3.774 3.797 3.820 190

200 3.820 3.843 3.866 3.889 3.912 3.935 3.958 3.981 4.004 4.027 4.050 200210 4.050 4.073 4.096 4.119 4.142 4.165 4.188 4.211 4.234 4.257 4.280 210220 4.280 4.303 4.326 4.349 4.372 4.395 4.417 4.440 4.463 4.486 4.509 220230 4.509 4.532 4.555 4.578 4.601 4.623 4.646 4.669 4.692 4.715 4.738 230240 4.738 4.760 4.783 4.806 4.829 4.852 4.874 4.897 4.920 4.943 4.965 240

250 4.965 4.988 5.011 5.034 5.056 5.079 5.102 5.124 5.147 5.170 5.192 250260 5.192 5.215 5.238 5.260 5.283 5.306 5.328 5.351 5.374 5.396 5.419 260270 5.419 5.441 5.464 5.487 5.509 5.532 5.554 5.577 5.599 5.622 5.644 270280 5.644 5.667 5.690 5.712 5.735 5.757 5.779 5.802 5.824 5.847 5.869 280290 5.869 5.892 5.914 5.937 5.959 5.982 6.004 6.026 6.049 6.071 6.094 290

300 6.094 6.116 6.138 6.161 6.183 6.205 6.228 6.250 6.272 6.295 6.317 300310 6.317 6.339 6.362 6.384 6.406 6.429 6.451 6.473 6.496 6.518 6.540 310320 6.540 6.562 6.585 6.607 6.629 6.652 6.674 6.696 6.718 6.741 6.763 320330 6.763 6.785 6.807 6.829 6.852 6.874 6.896 6.918 6.941 6.963 6.985 330340 6.985 7.007 7.029 7.052 7.074 7.096 7.118 7.140 7.163 7.185 7.207 340

350 7.207 7.229 7.251 7.273 7.296 7.318 7.340 7.362 7.384 7.407 7.429 350360 7.429 7.451 7.473 7.495 7.517 7.540 7.562 7.584 7.606 7.628 7.650 360370 7.650 7.673 7.695 7.717 7.739 7.761 7.783 7.806 7.828 7.850 7.872 370380 7.872 7.894 7.917 7.939 7.961 7.983 8.005 8.027 8.050 8.072 8.094 380390 8.094 8.116 8.138 8.161 8.183 8.205 8.227 8.250 8.272 8.294 8.316 390

400 8.316 8.338 8.361 8.383 8.405 8.427 8.450 8.472 8.494 8.516 8.539 400410 8.539 8.561 8.583 8.605 8.628 8.650 8.672 8.694 8.717 8.739 8.761 410420 8.761 8.784 8.806 8.828 8.851 8.873 8.895 8.918 8.940 8.962 8.985 420430 8.985 9.007 9.029 9.052 9.074 9.096 9.119 9.141 9.163 9.186 9.208 430440 9.208 9.231 9.253 9.275 9.298 9.320 9.343 9.365 9.388 9.410 9.432 440

450 9.432 9.455 9.477 9.500 9.522 9.545 9.567 9.590 9.612 9.635 9.657 450460 9.657 9.680 9.702 9.725 9.747 9.770 9.792 9.815 9.837 9.860 9.882 460470 9.882 9.905 9.927 9.950 9.973 9.995 10.018 10.040 10.063 10.086 10.108 470480 10.108 10.131 10.153 10.176 10.199 10.221 10.244 10.267 10.289 10.312 10.334 480490 10.334 10.357 10.380 10.402 10.425 10.448 10.471 10.493 10.516 10.539 10.561 490

500 10.561 10.584 10.607 10.629 10.652 10.675 10.698 10.720 10.743 10.766 10.789 500510 10.789 10.811 10.834 10.857 10.880 10.903 10.925 10.948 10.971 10.994 11.017 510520 11.017 11.039 11.062 11.085 11.108 11.131 11.154 11.176 11.199 11.222 11.245 520530 11.245 11.268 11.291 11.313 11.336 11.359 11.382 11.405 11.428 11.451 11.474 530540 11.474 11.497 11.519 11.542 11.565 11.588 11.611 11.634 11.657 11.680 11.703 540

550 11.703 11.726 11.749 11.772 11.795 11.818 11.841 11.864 11.887 11.910 11.933 550560 11.933 11.956 11.978 12.001 12.024 12.047 12.070 12.093 12.116 12.140 12.163 560570 12.163 12.186 12.209 12.232 12.255 12.278 12.301 12.324 12.347 12.370 12.393 570580 12.393 12.416 12.439 12.462 12.485 12.508 12.531 12.554 12.577 12.600 12.624 580590 12.624 12.647 12.670 12.693 12.716 12.739 12.762 12.785 12.808 12.831 12.855 590

600 12.855 12.878 12.901 12.924 12.947 12.970 12.993 13.016 13.040 13.063 13.086 600610 13.086 13.109 13.132 13.155 13.179 13.202 13.225 13.248 13.271 13.294 13.318 610620 13.318 13.341 13.364 13.387 13.410 13.433 13.457 13.480 13.503 13.526 13.549 620630 13.549 13.573 13.596 13.619 13.642 13.665 13.689 13.712 13.735 13.758 13.782 630640 13.782 13.805 13.828 13.851 13.874 13.898 13.921 13.944 13.967 13.991 14.014 640

650 14.014 14.037 14.060 14.084 14.107 14.130 14.154 14.177 14.200 14.223 14.247 650660 14.247 14.270 14.293 14.316 14.340 14.363 14.386 14.410 14.433 14.456 14.479 660670 14.479 14.503 14.526 14.549 14.573 14.596 14.619 14.643 14.666 14.689 14.713 670680 14.713 14.736 14.759 14.783 14.806 14.829 14.853 14.876 14.899 14.923 14.946 680690 14.946 14.969 14.993 15.016 15.039 15.063 15.086 15.109 15.133 15.156 15.179 690

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 328 to 2282°F– 200 to 1250°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 2.2°C or 0.75% Above 0°C2.2°C or 2.0% Below 0°CSpecial: 1.1°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Clean Oxidizing and Inert; Limited Use inVacuum or Reducing; Wide TemperatureRange; Most Popular CalibrationTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°F KK

°F -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

ThermocoupleGrade

Nickel-Chromiumvs.

Nickel-Aluminum

ExtensionGrade

+–

+–


+–


Z-219


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

700 15.179 15.203 15.226 15.250 15.273 15.296 15.320 15.343 15.366 15.390 15.413 700710 15.413 15.437 15.460 15.483 15.507 15.530 15.554 15.577 15.600 15.624 15.647 710720 15.647 15.671 15.694 15.717 15.741 15.764 15.788 15.811 15.834 15.858 15.881 720730 15.881 15.905 15.928 15.952 15.975 15.998 16.022 16.045 16.069 16.092 16.116 730740 16.116 16.139 16.163 16.186 16.209 16.233 16.256 16.280 16.303 16.327 16.350 740

750 16.350 16.374 16.397 16.421 16.444 16.468 16.491 16.514 16.538 16.561 16.585 750760 16.585 16.608 16.632 16.655 16.679 16.702 16.726 16.749 16.773 16.796 16.820 760770 16.820 16.843 16.867 16.890 16.914 16.937 16.961 16.984 17.008 17.031 17.055 770780 17.055 17.078 17.102 17.125 17.149 17.173 17.196 17.220 17.243 17.267 17.290 780790 17.290 17.314 17.337 17.361 17.384 17.408 17.431 17.455 17.478 17.502 17.526 790

800 17.526 17.549 17.573 17.596 17.620 17.643 17.667 17.690 17.714 17.738 17.761 800810 17.761 17.785 17.808 17.832 17.855 17.879 17.902 17.926 17.950 17.973 17.997 810820 17.997 18.020 18.044 18.068 18.091 18.115 18.138 18.162 18.185 18.209 18.233 820830 18.233 18.256 18.280 18.303 18.327 18.351 18.374 18.398 18.421 18.445 18.469 830840 18.469 18.492 18.516 18.539 18.563 18.587 18.610 18.634 18.657 18.681 18.705 840

850 18.705 18.728 18.752 18.776 18.799 18.823 18.846 18.870 18.894 18.917 18.941 850860 18.941 18.965 18.988 19.012 19.035 19.059 19.083 19.106 19.130 19.154 19.177 860870 19.177 19.201 19.224 19.248 19.272 19.295 19.319 19.343 19.366 19.390 19.414 870880 19.414 19.437 19.461 19.485 19.508 19.532 19.556 19.579 19.603 19.626 19.650 880890 19.650 19.674 19.697 19.721 19.745 19.768 19.792 19.816 19.839 19.863 19.887 890

900 19.887 19.910 19.934 19.958 19.981 20.005 20.029 20.052 20.076 20.100 20.123 900910 20.123 20.147 20.171 20.194 20.218 20.242 20.265 20.289 20.313 20.336 20.360 910920 20.360 20.384 20.407 20.431 20.455 20.479 20.502 20.526 20.550 20.573 20.597 920930 20.597 20.621 20.644 20.668 20.692 20.715 20.739 20.763 20.786 20.810 20.834 930940 20.834 20.857 20.881 20.905 20.929 20.952 20.976 21.000 21.023 21.047 21.071 940

950 21.071 21.094 21.118 21.142 21.165 21.189 21.213 21.236 21.260 21.284 21.308 950960 21.308 21.331 21.355 21.379 21.402 21.426 21.450 21.473 21.497 21.521 21.544 960970 21.544 21.568 21.592 21.616 21.639 21.663 21.687 21.710 21.734 21.758 21.781 970980 21.781 21.805 21.829 21.852 21.876 21.900 21.924 21.947 21.971 21.995 22.018 980990 22.018 22.042 22.066 22.089 22.113 22.137 22.160 22.184 22.208 22.232 22.255 990

1000 22.255 22.279 22.303 22.326 22.350 22.374 22.397 22.421 22.445 22.468 22.492 10001010 22.492 22.516 22.540 22.563 22.587 22.611 22.634 22.658 22.682 22.705 22.729 10101020 22.729 22.753 22.776 22.800 22.824 22.847 22.871 22.895 22.919 22.942 22.966 10201030 22.966 22.990 23.013 23.037 23.061 23.084 23.108 23.132 23.155 23.179 23.203 10301040 23.203 23.226 23.250 23.274 23.297 23.321 23.345 23.368 23.392 23.416 23.439 1040

1050 23.439 23.463 23.487 23.510 23.534 23.558 23.581 23.605 23.629 23.652 23.676 10501060 23.676 23.700 23.723 23.747 23.771 23.794 23.818 23.842 23.865 23.889 23.913 10601070 23.913 23.936 23.960 23.984 24.007 24.031 24.055 24.078 24.102 24.126 24.149 10701080 24.149 24.173 24.197 24.220 24.244 24.267 24.291 24.315 24.338 24.362 24.386 10801090 24.386 24.409 24.433 24.457 24.480 24.504 24.527 24.551 24.575 24.598 24.622 1090

1100 24.622 24.646 24.669 24.693 24.717 24.740 24.764 24.787 24.811 24.835 24.858 11001110 24.858 24.882 24.905 24.929 24.953 24.976 25.000 25.024 25.047 25.071 25.094 11101120 25.094 25.118 25.142 25.165 25.189 25.212 25.236 25.260 25.283 25.307 25.330 11201130 25.330 25.354 25.377 25.401 25.425 25.448 25.472 25.495 25.519 25.543 25.566 11301140 25.566 25.590 25.613 25.637 25.660 25.684 25.708 25.731 25.755 25.778 25.802 1140

1150 25.802 25.825 25.849 25.873 25.896 25.920 25.943 25.967 25.990 26.014 26.037 11501160 26.037 26.061 26.084 26.108 26.132 26.155 26.179 26.202 26.226 26.249 26.273 11601170 26.273 26.296 26.320 26.343 26.367 26.390 26.414 26.437 26.461 26.484 26.508 11701180 26.508 26.532 26.555 26.579 26.602 26.626 26.649 26.673 26.696 26.720 26.743 11801190 26.743 26.767 26.790 26.814 26.837 26.861 26.884 26.907 26.931 26.954 26.978 1190

1200 26.978 27.001 27.025 27.048 27.072 27.095 27.119 27.142 27.166 27.189 27.213 12001210 27.213 27.236 27.259 27.283 27.306 27.330 27.353 27.377 27.400 27.424 27.447 12101220 27.447 27.471 27.494 27.517 27.541 27.564 27.588 27.611 27.635 27.658 27.681 12201230 27.681 27.705 27.728 27.752 27.775 27.798 27.822 27.845 27.869 27.892 27.915 12301240 27.915 27.939 27.962 27.986 28.009 28.032 28.056 28.079 28.103 28.126 28.149 1240

1250 28.149 28.173 28.196 28.219 28.243 28.266 28.289 28.313 28.336 28.360 28.383 12501260 28.383 28.406 28.430 28.453 28.476 28.500 28.523 28.546 28.570 28.593 28.616 12601270 28.616 28.640 28.663 28.686 28.710 28.733 28.756 28.780 28.803 28.826 28.849 12701280 28.849 28.873 28.896 28.919 28.943 28.966 28.989 29.013 29.036 29.059 29.082 12801290 29.082 29.106 29.129 29.152 29.176 29.199 29.222 29.245 29.269 29.292 29.315 1290

1300 29.315 29.338 29.362 29.385 29.408 29.431 29.455 29.478 29.501 29.524 29.548 13001310 29.548 29.571 29.594 29.617 29.640 29.664 29.687 29.710 29.733 29.757 29.780 13101320 29.780 29.803 29.826 29.849 29.873 29.896 29.919 29.942 29.965 29.989 30.012 13201330 30.012 30.035 30.058 30.081 30.104 30.128 30.151 30.174 30.197 30.220 30.243 13301340 30.243 30.267 30.290 30.313 30.336 30.359 30.382 30.405 30.429 30.452 30.475 1340

1350 30.475 30.498 30.521 30.544 30.567 30.590 30.613 30.637 30.660 30.683 30.706 13501360 30.706 30.729 30.752 30.775 30.798 30.821 30.844 30.868 30.891 30.914 30.937 13601370 30.937 30.960 30.983 31.006 31.029 31.052 31.075 31.098 31.121 31.144 31.167 13701380 31.167 31.190 31.213 31.236 31.260 31.283 31.306 31.329 31.352 31.375 31.398 13801390 31.398 31.421 31.444 31.467 31.490 31.513 31.536 31.559 31.582 31.605 31.628 1390

1400 31.628 31.651 31.674 31.697 31.720 31.743 31.766 31.789 31.812 31.834 31.857 14001410 31.857 31.880 31.903 31.926 31.949 31.972 31.995 32.018 32.041 32.064 32.087 14101420 32.087 32.110 32.133 32.156 32.179 32.202 32.224 32.247 32.270 32.293 32.316 14201430 32.316 32.339 32.362 32.385 32.408 32.431 32.453 32.476 32.499 32.522 32.545 14301440 32.545 32.568 32.591 32.614 32.636 32.659 32.682 32.705 32.728 32.751 32.774 1440

1450 32.774 32.796 32.819 32.842 32.865 32.888 32.911 32.933 32.956 32.979 33.002 14501460 33.002 33.025 33.047 33.070 33.093 33.116 33.139 33.161 33.184 33.207 33.230 14601470 33.230 33.253 33.275 33.298 33.321 33.344 33.366 33.389 33.412 33.435 33.458 14701480 33.458 33.480 33.503 33.526 33.548 33.571 33.594 33.617 33.639 33.662 33.685 14801490 33.685 33.708 33.730 33.753 33.776 33.798 33.821 33.844 33.867 33.889 33.912 1490

1500 33.912 33.935 33.957 33.980 34.003 34.025 34.048 34.071 34.093 34.116 34.139 15001510 34.139 34.161 34.184 34.207 34.229 34.252 34.275 34.297 34.320 34.343 34.365 15101520 34.365 34.388 34.410 34.433 34.456 34.478 34.501 34.524 34.546 34.569 34.591 15201530 34.591 34.614 34.637 34.659 34.682 34.704 34.727 34.750 34.772 34.795 34.817 15301540 34.817 34.840 34.862 34.885 34.908 34.930 34.953 34.975 34.998 35.020 35.043 1540

1550 35.043 35.065 35.088 35.110 35.133 35.156 35.178 35.201 35.223 35.246 35.268 15501560 35.268 35.291 35.313 35.336 35.358 35.381 35.403 35.426 35.448 35.471 35.493 15601570 35.493 35.516 35.538 35.560 35.583 35.605 35.628 35.650 35.673 35.695 35.718 15701580 35.718 35.740 35.763 35.785 35.807 35.830 35.852 35.875 35.897 35.920 35.942 15801590 35.942 35.964 35.987 36.009 36.032 36.054 36.076 36.099 36.121 36.144 36.166 1590

1600 36.166 36.188 36.211 36.233 36.256 36.278 36.300 36.323 36.345 36.367 36.390 16001610 36.390 36.412 36.434 36.457 36.479 36.501 36.524 36.546 36.568 36.591 36.613 16101620 36.613 36.635 36.658 36.680 36.702 36.725 36.747 36.769 36.792 36.814 36.836 16201630 36.836 36.859 36.881 36.903 36.925 36.948 36.970 36.992 37.014 37.037 37.059 16301640 37.059 37.081 37.104 37.126 37.148 37.170 37.193 37.215 37.237 37.259 37.281 1640

1650 37.281 37.304 37.326 37.348 37.370 37.393 37.415 37.437 37.459 37.481 37.504 16501660 37.504 37.526 37.548 37.570 37.592 37.615 37.637 37.659 37.681 37.703 37.725 16601670 37.725 37.748 37.770 37.792 37.814 37.836 37.858 37.881 37.903 37.925 37.947 16701680 37.947 37.969 37.991 38.013 38.036 38.058 38.080 38.102 38.124 38.146 38.168 16801690 38.168 38.190 38.212 38.235 38.257 38.279 38.301 38.323 38.345 38.367 38.389 1690

1700 38.389 38.411 38.433 38.455 38.477 38.499 38.522 38.544 38.566 38.588 38.610 17001710 38.610 38.632 38.654 38.676 38.698 38.720 38.742 38.764 38.786 38.808 38.830 17101720 38.830 38.852 38.874 38.896 38.918 38.940 38.962 38.984 39.006 39.028 39.050 17201730 39.050 39.072 39.094 39.116 39.138 39.160 39.182 39.204 39.226 39.248 39.270 17301740 39.270 39.292 39.314 39.335 39.357 39.379 39.401 39.423 39.445 39.467 39.489 1740

1750 39.489 39.511 39.533 39.555 39.577 39.599 39.620 39.642 39.664 39.686 39.708 17501760 39.708 39.730 39.752 39.774 39.796 39.817 39.839 39.861 39.883 39.905 39.927 17601770 39.927 39.949 39.970 39.992 40.014 40.036 40.058 40.080 40.101 40.123 40.145 17701780 40.145 40.167 40.189 40.211 40.232 40.254 40.276 40.298 40.320 40.341 40.363 17801790 40.363 40.385 40.407 40.429 40.450 40.472 40.494 40.516 40.537 40.559 40.581 1790

1800 40.581 40.603 40.624 40.646 40.668 40.690 40.711 40.733 40.755 40.777 40.798 18001810 40.798 40.820 40.842 40.864 40.885 40.907 40.929 40.950 40.972 40.994 41.015 18101820 41.015 41.037 41.059 41.081 41.102 41.124 41.146 41.167 41.189 41.211 41.232 18201830 41.232 41.254 41.276 41.297 41.319 41.341 41.362 41.384 41.405 41.427 41.449 18301840 41.449 41.470 41.492 41.514 41.535 41.557 41.578 41.600 41.622 41.643 41.665 1840

1850 41.665 41.686 41.708 41.730 41.751 41.773 41.794 41.816 41.838 41.859 41.881 18501860 41.881 41.902 41.924 41.945 41.967 41.988 42.010 42.032 42.053 42.075 42.096 18601870 42.096 42.118 42.139 42.161 42.182 42.204 42.225 42.247 42.268 42.290 42.311 18701880 42.311 42.333 42.354 42.376 42.397 42.419 42.440 42.462 42.483 42.505 42.526 18801890 42.526 42.548 42.569 42.591 42.612 42.633 42.655 42.676 42.698 42.719 42.741 1890

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 328 to 2282°F– 200 to 1250°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 2.2°C or 0.75% Above 0°C2.2°C or 2.0% Below 0°CSpecial: 1.1°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Clean Oxidizing and Inert; Limited Use inVacuum or Reducing; Wide TemperatureRange; Most Popular CalibrationTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°FKK

ThermocoupleGrade

Nickel-Chromiumvs.

Nickel-Aluminum

ExtensionGrade

+–


+–


Z-220

Z


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

1900 42.741 42.762 42.783 42.805 42.826 42.848 42.869 42.891 42.912 42.933 42.955 19001910 42.955 42.976 42.998 43.019 43.040 43.062 43.083 43.104 43.126 43.147 43.169 19101920 43.169 43.190 43.211 43.233 43.254 43.275 43.297 43.318 43.339 43.361 43.382 19201930 43.382 43.403 43.425 43.446 43.467 43.489 43.510 43.531 43.552 43.574 43.595 19301940 43.595 43.616 43.638 43.659 43.680 43.701 43.723 43.744 43.765 43.787 43.808 1940

1950 43.808 43.829 43.850 43.872 43.893 43.914 43.935 43.957 43.978 43.999 44.020 19501960 44.020 44.041 44.063 44.084 44.105 44.126 44.147 44.169 44.190 44.211 44.232 19601970 44.232 44.253 44.275 44.296 44.317 44.338 44.359 44.380 44.402 44.423 44.444 19701980 44.444 44.465 44.486 44.507 44.528 44.550 44.571 44.592 44.613 44.634 44.655 19801990 44.655 44.676 44.697 44.719 44.740 44.761 44.782 44.803 44.824 44.845 44.866 1990

2000 44.866 44.887 44.908 44.929 44.950 44.971 44.992 45.014 45.035 45.056 45.077 20002010 45.077 45.098 45.119 45.140 45.161 45.182 45.203 45.224 45.245 45.266 45.287 20102020 45.287 45.308 45.329 45.350 45.371 45.392 45.413 45.434 45.455 45.476 45.497 20202030 45.497 45.518 45.539 45.560 45.580 45.601 45.622 45.643 45.664 45.685 45.706 20302040 45.706 45.727 45.748 45.769 45.790 45.811 45.832 45.852 45.873 45.894 45.915 2040

2050 45.915 45.936 45.957 45.978 45.999 46.019 46.040 46.061 46.082 46.103 46.124 20502060 46.124 46.145 46.165 46.186 46.207 46.228 46.249 46.269 46.290 46.311 46.332 20602070 46.332 46.353 46.373 46.394 46.415 46.436 46.457 46.477 46.498 46.519 46.540 20702080 46.540 46.560 46.581 46.602 46.623 46.643 46.664 46.685 46.706 46.726 46.747 20802090 46.747 46.768 46.789 46.809 46.830 46.851 46.871 46.892 46.913 46.933 46.954 2090

2100 46.954 46.975 46.995 47.016 47.037 47.057 47.078 47.099 47.119 47.140 47.161 21002110 47.161 47.181 47.202 47.223 47.243 47.264 47.284 47.305 47.326 47.346 47.367 21102120 47.367 47.387 47.408 47.429 47.449 47.470 47.490 47.511 47.531 47.552 47.573 21202130 47.573 47.593 47.614 47.634 47.655 47.675 47.696 47.716 47.737 47.757 47.778 21302140 47.778 47.798 47.819 47.839 47.860 47.880 47.901 47.921 47.942 47.962 47.983 2140

2150 47.983 48.003 48.024 48.044 48.065 48.085 48.105 48.126 48.146 48.167 48.187 21502160 48.187 48.208 48.228 48.248 48.269 48.289 48.310 48.330 48.350 48.371 48.391 21602170 48.391 48.411 48.432 48.452 48.473 48.493 48.513 48.534 48.554 48.574 48.595 21702180 48.595 48.615 48.635 48.656 48.676 48.696 48.717 48.737 48.757 48.777 48.798 21802190 48.798 48.818 48.838 48.859 48.879 48.899 48.919 48.940 48.960 48.980 49.000 2190

2200 49.000 49.021 49.041 49.061 49.081 49.101 49.122 49.142 49.162 49.182 49.202 22002210 49.202 49.223 49.243 49.263 49.283 49.303 49.323 49.344 49.364 49.384 49.404 22102220 49.404 49.424 49.444 49.465 49.485 49.505 49.525 49.545 49.565 49.585 49.605 22202230 49.605 49.625 49.645 49.666 49.686 49.706 49.726 49.746 49.766 49.786 49.806 22302240 49.806 49.826 49.846 49.866 49.886 49.906 49.926 49.946 49.966 49.986 50.006 2240

2250 50.006 50.026 50.046 50.066 50.086 50.106 50.126 50.146 50.166 50.186 50.206 22502260 50.206 50.226 50.246 50.266 50.286 50.306 50.326 50.346 50.366 50.385 50.405 22602270 50.405 50.425 50.445 50.465 50.485 50.505 50.525 50.545 50.564 50.584 50.604 22702280 50.604 50.624 50.644 50.664 50.684 50.703 50.723 50.743 50.763 50.783 50.802 22802290 50.802 50.822 50.842 50.862 50.882 50.901 50.921 50.941 50.961 50.981 51.000 2290

2300 51.000 51.020 51.040 51.060 51.079 51.099 51.119 51.139 51.158 51.178 51.198 23002310 51.198 51.217 51.237 51.257 51.276 51.296 51.316 51.336 51.355 51.375 51.395 23102320 51.395 51.414 51.434 51.453 51.473 51.493 51.512 51.532 51.552 51.571 51.591 23202330 51.591 51.611 51.630 51.650 51.669 51.689 51.708 51.728 51.748 51.767 51.787 23302340 51.787 51.806 51.826 51.845 51.865 51.885 51.904 51.924 51.943 51.963 51.982 2340

2350 51.982 52.002 52.021 52.041 52.060 52.080 52.099 52.119 52.138 52.158 52.177 23502360 52.177 52.197 52.216 52.235 52.255 52.274 52.294 52.313 52.333 52.352 52.371 23602370 52.371 52.391 52.410 52.430 52.449 52.468 52.488 52.507 52.527 52.546 52.565 23702380 52.565 52.585 52.604 52.623 52.643 52.662 52.681 52.701 52.720 52.739 52.759 2380239052.759 52.778 52.797 52.817 52.836 52.855 52.875 52.894 52.913 52.932 52.952 2390

2400 52.952 52.971 52.990 53.010 53.029 53.048 53.067 53.087 53.106 53.125 53.144 24002410 53.144 53.163 53.183 53.202 53.221 53.240 53.260 53.279 53.298 53.317 53.336 24102420 53.336 53.355 53.375 53.394 53.413 53.432 53.451 53.470 53.490 53.509 53.528 24202430 53.528 53.547 53.566 53.585 53.604 53.623 53.643 53.662 53.681 53.700 53.719 24302440 53.719 53.738 53.757 53.776 53.795 53.814 53.833 53.852 53.871 53.890 53.910 2440

2450 53.910 53.929 53.948 53.967 53.986 54.005 54.024 54.043 54.062 54.081 54.100 24502460 54.100 54.119 54.138 54.157 54.176 54.195 54.214 54.233 54.252 54.271 54.289 24602470 54.289 54.308 54.327 54.346 54.365 54.384 54.403 54.422 54.441 54.460 54.479 24702480 54.479 54.498 54.517 54.536 54.554 54.573 54.592 54.611 54.630 54.649 54.668 24802490 54.668 54.687 54.705 54.724 54.743 54.762 54.781 54.800 54.819 54.837 54.856 2490

2500 54.856 54.875 54.894 2500

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 328 to 2282°F– 200 to 1250°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 2.2°C or 0.75% Above 0°C2.2°C or 2.0% Below 0°CSpecial: 1.1°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Clean Oxidizing and Inert; Limited Use inVacuum or Reducing; Wide TemperatureRange; Most Popular CalibrationTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°F KK

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

ThermocoupleGrade

Nickel-Chromiumvs.

Nickel-Aluminum

ExtensionGrade

+–

+–



Z-221


°F -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

-450 -9.835 -9.834 -9.833 -9.832 -9.830 -450

-440 -9.830 -9.829 -9.827 -9.825 -9.823 -9.821 -9.819 -9.817 -9.814 -9.812 -9.809 -440-430 -9.809 -9.806 -9.803 -9.800 -9.797 -9.793 -9.790 -9.786 -9.782 -9.779 -9.775 -430-420 -9.775 -9.771 -9.766 -9.762 -9.758 -9.753 -9.749 -9.744 -9.739 -9.734 -9.729 -420-410 -9.729 -9.724 -9.718 -9.713 -9.707 -9.702 -9.696 -9.690 -9.684 -9.678 -9.672 -410-400 -9.672 -9.666 -9.659 -9.653 -9.646 -9.639 -9.632 -9.625 -9.618 -9.611 -9.604 -400

-390 -9.604 -9.597 -9.589 -9.581 -9.574 -9.566 -9.558 -9.550 -9.542 -9.534 -9.525 -390-380 -9.525 -9.517 -9.508 -9.500 -9.491 -9.482 -9.473 -9.464 -9.455 -9.446 -9.436 -380-370 -9.436 -9.427 -9.417 -9.408 -9.398 -9.388 -9.378 -9.368 -9.358 -9.348 -9.338 -370-360 -9.338 -9.327 -9.317 -9.306 -9.295 -9.285 -9.274 -9.263 -9.252 -9.241 -9.229 -360-350 -9.229 -9.218 -9.207 -9.195 -9.184 -9.172 -9.160 -9.148 -9.136 -9.124 -9.112 -350

-340 -9.112 -9.100 -9.088 -9.075 -9.063 -9.050 -9.038 -9.025 -9.012 -8.999 -8.986 -340-330 -8.986 -8.973 -8.960 -8.947 -8.934 -8.920 -8.907 -8.893 -8.880 -8.866 -8.852 -330-320 -8.852 -8.839 -8.825 -8.811 -8.797 -8.782 -8.768 -8.754 -8.739 -8.725 -8.710 -320-310 -8.710 -8.696 -8.681 -8.666 -8.652 -8.637 -8.622 -8.607 -8.591 -8.576 -8.561 -310-300 -8.561 -8.546 -8.530 -8.515 -8.499 -8.483 -8.468 -8.452 -8.436 -8.420 -8.404 -300

-290 -8.404 -8.388 -8.372 -8.356 -8.339 -8.323 -8.307 -8.290 -8.273 -8.257 -8.240 -290-280 -8.240 -8.223 -8.206 -8.189 -8.173 -8.155 -8.138 -8.121 -8.104 -8.087 -8.069 -280-270 -8.069 -8.052 -8.034 -8.017 -7.999 -7.981 -7.963 -7.945 -7.928 -7.910 -7.891 -270-260 -7.891 -7.873 -7.855 -7.837 -7.819 -7.800 -7.782 -7.763 -7.745 -7.726 -7.707 -260-250 -7.707 -7.688 -7.670 -7.651 -7.632 -7.613 -7.593 -7.574 -7.555 -7.536 -7.516 -250

-240 -7.516 -7.497 -7.478 -7.458 -7.438 -7.419 -7.399 -7.379 -7.359 -7.339 -7.319 -240-230 -7.319 -7.299 -7.279 -7.259 -7.239 -7.219 -7.198 -7.178 -7.157 -7.137 -7.116 -230-220 -7.116 -7.096 -7.075 -7.054 -7.033 -7.013 -6.992 -6.971 -6.950 -6.928 -6.907 -220-210 -6.907 -6.886 -6.865 -6.843 -6.822 -6.801 -6.779 -6.757 -6.736 -6.714 -6.692 -210-200 -6.692 -6.671 -6.649 -6.627 -6.605 -6.583 -6.561 -6.539 -6.516 -6.494 -6.472 -200

-190 -6.472 -6.449 -6.427 -6.405 -6.382 -6.359 -6.337 -6.314 -6.291 -6.269 -6.246 -190-180 -6.246 -6.223 -6.200 -6.177 -6.154 -6.130 -6.107 -6.084 -6.061 -6.037 -6.014 -180-170 -6.014 -5.991 -5.967 -5.943 -5.920 -5.896 -5.872 -5.849 -5.825 -5.801 -5.777 -170-160 -5.777 -5.753 -5.729 -5.705 -5.681 -5.656 -5.632 -5.608 -5.584 -5.559 -5.535 -160-150 -5.535 -5.510 -5.486 -5.461 -5.436 -5.412 -5.387 -5.362 -5.337 -5.312 -5.287 -150

-140 -5.287 -5.262 -5.237 -5.212 -5.187 -5.162 -5.136 -5.111 -5.086 -5.060 -5.035 -140-130 -5.035 -5.009 -4.984 -4.958 -4.932 -4.907 -4.881 -4.855 -4.829 -4.803 -4.777 -130-120 -4.777 -4.751 -4.725 -4.699 -4.673 -4.647 -4.621 -4.594 -4.568 -4.542 -4.515 -120-110 -4.515 -4.489 -4.462 -4.436 -4.409 -4.382 -4.355 -4.329 -4.302 -4.275 -4.248 -110-100 -4.248 -4.221 -4.194 -4.167 -4.140 -4.113 -4.086 -4.058 -4.031 -4.004 -3.976 -100

-90 -3.976 -3.949 -3.922 -3.894 -3.867 -3.839 -3.811 -3.784 -3.756 -3.728 -3.700 -90-80 -3.700 -3.672 -3.645 -3.617 -3.589 -3.561 -3.532 -3.504 -3.476 -3.448 -3.420 -80-70 -3.420 -3.391 -3.363 -3.335 -3.306 -3.278 -3.249 -3.221 -3.192 -3.163 -3.135 -70-60 -3.135 -3.106 -3.077 -3.048 -3.020 -2.991 -2.962 -2.933 -2.904 -2.875 -2.846 -60-50 -2.846 -2.816 -2.787 -2.758 -2.729 -2.699 -2.670 -2.641 -2.611 -2.582 -2.552 -50

-40 -2.552 -2.523 -2.493 -2.463 -2.434 -2.404 -2.374 -2.344 -2.315 -2.285 -2.255 -40-30 -2.255 -2.225 -2.195 -2.165 -2.135 -2.105 -2.074 -2.044 -2.014 -1.984 -1.953 -30-20 -1.953 -1.923 -1.893 -1.862 -1.832 -1.801 -1.771 -1.740 -1.709 -1.679 -1.648 -20-10 -1.648 -1.617 -1.587 -1.556 -1.525 -1.494 -1.463 -1.432 -1.401 -1.370 -1.339 -10

0 -1.339 -1.308 -1.277 -1.245 -1.214 -1.183 -1.152 -1.120 -1.089 -1.057 -1.026 0

0 -1.026 -0.994 -0.963 -0.931 -0.900 -0.868 -0.836 -0.805 -0.773 -0.741 -0.709 010 -0.709 -0.677 -0.645 -0.614 -0.582 -0.550 -0.517 -0.485 -0.453 -0.421 -0.389 1020 -0.389 -0.357 -0.324 -0.292 -0.260 -0.227 -0.195 -0.163 -0.130 -0.098 -0.065 2030 -0.065 -0.033 0.000 0.033 0.065 0.098 0.131 0.163 0.196 0.229 0.262 3040 0.262 0.294 0.327 0.360 0.393 0.426 0.459 0.492 0.525 0.558 0.591 40

50 0.591 0.624 0.657 0.691 0.724 0.757 0.790 0.824 0.857 0.890 0.924 5060 0.924 0.957 0.990 1.024 1.057 1.091 1.124 1.158 1.192 1.225 1.259 6070 1.259 1.292 1.326 1.360 1.394 1.427 1.461 1.495 1.529 1.563 1.597 7080 1.597 1.631 1.665 1.699 1.733 1.767 1.801 1.835 1.869 1.904 1.938 8090 1.938 1.972 2.006 2.041 2.075 2.109 2.144 2.178 2.212 2.247 2.281 90

100 2.281 2.316 2.351 2.385 2.420 2.454 2.489 2.524 2.558 2.593 2.628 100110 2.628 2.663 2.698 2.733 2.767 2.802 2.837 2.872 2.907 2.942 2.977 110120 2.977 3.012 3.048 3.083 3.118 3.153 3.188 3.224 3.259 3.294 3.330 120130 3.330 3.365 3.400 3.436 3.471 3.507 3.542 3.578 3.613 3.649 3.685 130140 3.685 3.720 3.756 3.792 3.827 3.863 3.899 3.935 3.970 4.006 4.042 140

150 4.042 4.078 4.114 4.150 4.186 4.222 4.258 4.294 4.330 4.366 4.403 150160 4.403 4.439 4.475 4.511 4.547 4.584 4.620 4.656 4.693 4.729 4.766 160170 4.766 4.802 4.839 4.875 4.912 4.948 4.985 5.021 5.058 5.095 5.131 170180 5.131 5.168 5.205 5.242 5.278 5.315 5.352 5.389 5.426 5.463 5.500 180190 5.500 5.537 5.574 5.611 5.648 5.685 5.722 5.759 5.796 5.833 5.871 190

200 5.871 5.908 5.945 5.982 6.020 6.057 6.094 6.132 6.169 6.207 6.244 200210 6.244 6.281 6.319 6.356 6.394 6.432 6.469 6.507 6.544 6.582 6.620 210220 6.620 6.658 6.695 6.733 6.771 6.809 6.847 6.884 6.922 6.960 6.998 220230 6.998 7.036 7.074 7.112 7.150 7.188 7.226 7.264 7.302 7.341 7.379 230240 7.379 7.417 7.455 7.493 7.532 7.570 7.608 7.647 7.685 7.723 7.762 240

250 7.762 7.800 7.839 7.877 7.916 7.954 7.993 8.031 8.070 8.108 8.147 250260 8.147 8.186 8.224 8.263 8.302 8.340 8.379 8.418 8.457 8.496 8.535 260270 8.535 8.573 8.612 8.651 8.690 8.729 8.768 8.807 8.846 8.885 8.924 270280 8.924 8.963 9.002 9.041 9.081 9.120 9.159 9.198 9.237 9.277 9.316 280290 9.316 9.355 9.395 9.434 9.473 9.513 9.552 9.591 9.631 9.670 9.710 290

300 9.710 9.749 9.789 9.828 9.868 9.907 9.947 9.987 10.026 10.066 10.106 300310 10.106 10.145 10.185 10.225 10.265 10.304 10.344 10.384 10.424 10.464 10.503 310320 10.503 10.543 10.583 10.623 10.663 10.703 10.743 10.783 10.823 10.863 10.903 320330 10.903 10.943 10.983 11.024 11.064 11.104 11.144 11.184 11.224 11.265 11.305 330340 11.305 11.345 11.385 11.426 11.466 11.506 11.547 11.587 11.627 11.668 11.708 340

350 11.708 11.749 11.789 11.830 11.870 11.911 11.951 11.992 12.032 12.073 12.113 350360 12.113 12.154 12.195 12.235 12.276 12.317 12.357 12.398 12.439 12.480 12.520 360370 12.520 12.561 12.602 12.643 12.684 12.724 12.765 12.806 12.847 12.888 12.929 370380 12.929 12.970 13.011 13.052 13.093 13.134 13.175 13.216 13.257 13.298 13.339 380390 13.339 13.380 13.421 13.462 13.504 13.545 13.586 13.627 13.668 13.710 13.751 390

400 13.751 13.792 13.833 13.875 13.916 13.957 13.999 14.040 14.081 14.123 14.164 400410 14.164 14.205 14.247 14.288 14.330 14.371 14.413 14.454 14.496 14.537 14.579 410420 14.579 14.620 14.662 14.704 14.745 14.787 14.828 14.870 14.912 14.953 14.995 420430 14.995 15.037 15.078 15.120 15.162 15.204 15.245 15.287 15.329 15.371 15.413 430440 15.413 15.454 15.496 15.538 15.580 15.622 15.664 15.706 15.748 15.790 15.831 440

450 15.831 15.873 15.915 15.957 15.999 16.041 16.083 16.125 16.168 16.210 16.252 450460 16.252 16.294 16.336 16.378 16.420 16.462 16.504 16.547 16.589 16.631 16.673 460470 16.673 16.715 16.758 16.800 16.842 16.884 16.927 16.969 17.011 17.054 17.096 470480 17.096 17.138 17.181 17.223 17.265 17.308 17.350 17.392 17.435 17.477 17.520 480490 17.520 17.562 17.605 17.647 17.690 17.732 17.775 17.817 17.860 17.902 17.945 490

500 17.945 17.987 18.030 18.073 18.115 18.158 18.200 18.243 18.286 18.328 18.371 500510 18.371 18.414 18.456 18.499 18.542 18.585 18.627 18.670 18.713 18.756 18.798 510520 18.798 18.841 18.884 18.927 18.969 19.012 19.055 19.098 19.141 19.184 19.227 520530 19.227 19.269 19.312 19.355 19.398 19.441 19.484 19.527 19.570 19.613 19.656 530540 19.656 19.699 19.742 19.785 19.828 19.871 19.914 19.957 20.000 20.043 20.086 540

550 20.086 20.129 20.172 20.216 20.259 20.302 20.345 20.388 20.431 20.474 20.517 550560 20.517 20.561 20.604 20.647 20.690 20.733 20.777 20.820 20.863 20.906 20.950 560570 20.950 20.993 21.036 21.080 21.123 21.166 21.209 21.253 21.296 21.339 21.383 570580 21.383 21.426 21.470 21.513 21.556 21.600 21.643 21.686 21.730 21.773 21.817 580590 21.817 21.860 21.904 21.947 21.991 22.034 22.078 22.121 22.165 22.208 22.252 590

600 22.252 22.295 22.339 22.382 22.426 22.469 22.513 22.556 22.600 22.644 22.687 600610 22.687 22.731 22.774 22.818 22.862 22.905 22.949 22.993 23.036 23.080 23.124 610620 23.124 23.167 23.211 23.255 23.298 23.342 23.386 23.429 23.473 23.517 23.561 620630 23.561 23.604 23.648 23.692 23.736 23.780 23.823 23.867 23.911 23.955 23.999 630640 23.999 24.042 24.086 24.130 24.174 24.218 24.262 24.305 24.349 24.393 24.437 640

650 24.437 24.481 24.525 24.569 24.613 24.657 24.701 24.745 24.789 24.832 24.876 650660 24.876 24.920 24.964 25.008 25.052 25.096 25.140 25.184 25.228 25.272 25.316 660670 25.316 25.360 25.404 25.448 25.493 25.537 25.581 25.625 25.669 25.713 25.757 670680 25.757 25.801 25.845 25.889 25.933 25.977 26.022 26.066 26.110 26.154 26.198 680690 26.198 26.242 26.286 26.331 26.375 26.419 26.463 26.507 26.552 26.596 26.640 690

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 328 to 1652°F– 200 to 900°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 1.7°C or 0.5% Above 0°C1.7°C or 1.0°C Below 0°CSpecial: 1.0°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Limited Use in Vacuum orReducing; Highest EMF Change per DegreeTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°FEE

ThermocoupleGrade

Nickel-Chromiumvs.

Copper-Nickel

ExtensionGrade

+–

+–


+–

+–


Z-222

Z


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

700 26.640 26.684 26.728 26.773 26.817 26.861 26.905 26.950 26.994 27.038 27.082 700710 27.082 27.127 27.171 27.215 27.259 27.304 27.348 27.392 27.437 27.481 27.525 710720 27.525 27.570 27.614 27.658 27.703 27.747 27.791 27.836 27.880 27.924 27.969 720730 27.969 28.013 28.057 28.102 28.146 28.191 28.235 28.279 28.324 28.368 28.413 730740 28.413 28.457 28.501 28.546 28.590 28.635 28.679 28.724 28.768 28.813 28.857 740

750 28.857 28.901 28.946 28.990 29.035 29.079 29.124 29.168 29.213 29.257 29.302 750760 29.302 29.346 29.391 29.435 29.480 29.525 29.569 29.614 29.658 29.703 29.747 760770 29.747 29.792 29.836 29.881 29.925 29.970 30.015 30.059 30.104 30.148 30.193 770780 30.193 30.238 30.282 30.327 30.371 30.416 30.461 30.505 30.550 30.595 30.639 780790 30.639 30.684 30.728 30.773 30.818 30.862 30.907 30.952 30.996 31.041 31.086 790

800 31.086 31.130 31.175 31.220 31.264 31.309 31.354 31.398 31.443 31.488 31.533 800810 31.533 31.577 31.622 31.667 31.711 31.756 31.801 31.846 31.890 31.935 31.980 810820 31.980 32.025 32.069 32.114 32.159 32.204 32.248 32.293 32.338 32.383 32.427 820830 32.427 32.472 32.517 32.562 32.606 32.651 32.696 32.741 32.786 32.830 32.875 830840 32.875 32.920 32.965 33.010 33.054 33.099 33.144 33.189 33.234 33.278 33.323 840

850 33.323 33.368 33.413 33.458 33.503 33.547 33.592 33.637 33.682 33.727 33.772 850860 33.772 33.816 33.861 33.906 33.951 33.996 34.041 34.086 34.130 34.175 34.220 860870 34.220 34.265 34.310 34.355 34.400 34.445 34.489 34.534 34.579 34.624 34.669 870880 34.669 34.714 34.759 34.804 34.849 34.893 34.938 34.983 35.028 35.073 35.118 880890 35.118 35.163 35.208 35.253 35.298 35.343 35.387 35.432 35.477 35.522 35.567 890

900 35.567 35.612 35.657 35.702 35.747 35.792 35.837 35.882 35.927 35.972 36.016 900910 36.016 36.061 36.106 36.151 36.196 36.241 36.286 36.331 36.376 36.421 36.466 910920 36.466 36.511 36.556 36.601 36.646 36.691 36.736 36.781 36.826 36.870 36.915 920930 36.915 36.960 37.005 37.050 37.095 37.140 37.185 37.230 37.275 37.320 37.365 930940 37.365 37.410 37.455 37.500 37.545 37.590 37.635 37.680 37.725 37.770 37.815 940

950 37.815 37.860 37.905 37.950 37.995 38.040 38.085 38.130 38.175 38.220 38.265 950960 38.265 38.309 38.354 38.399 38.444 38.489 38.534 38.579 38.624 38.669 38.714 960970 38.714 38.759 38.804 38.849 38.894 38.939 38.984 39.029 39.074 39.119 39.164 970980 39.164 39.209 39.254 39.299 39.344 39.389 39.434 39.479 39.524 39.569 39.614 980990 39.614 39.659 39.704 39.749 39.794 39.839 39.884 39.929 39.974 40.019 40.064 990

1000 40.064 40.109 40.154 40.199 40.243 40.288 40.333 40.378 40.423 40.468 40.513 10001010 40.513 40.558 40.603 40.648 40.693 40.738 40.783 40.828 40.873 40.918 40.963 10101020 40.963 41.008 41.053 41.098 41.143 41.188 41.233 41.278 41.323 41.368 41.412 10201030 41.412 41.457 41.502 41.547 41.592 41.637 41.682 41.727 41.772 41.817 41.862 10301040 41.862 41.907 41.952 41.997 42.042 42.087 42.132 42.176 42.221 42.266 42.311 1040

1050 42.311 42.356 42.401 42.446 42.491 42.536 42.581 42.626 42.671 42.715 42.760 10501060 42.760 42.805 42.850 42.895 42.940 42.985 43.030 43.075 43.120 43.165 43.209 10601070 43.209 43.254 43.299 43.344 43.389 43.434 43.479 43.524 43.569 43.613 43.658 10701080 43.658 43.703 43.748 43.793 43.838 43.883 43.928 43.972 44.017 44.062 44.107 10801090 44.107 44.152 44.197 44.242 44.286 44.331 44.376 44.421 44.466 44.511 44.555 1090

1100 44.555 44.600 44.645 44.690 44.735 44.780 44.824 44.869 44.914 44.959 45.004 11001110 45.004 45.049 45.093 45.138 45.183 45.228 45.273 45.317 45.362 45.407 45.452 11101120 45.452 45.497 45.541 45.586 45.631 45.676 45.720 45.765 45.810 45.855 45.900 11201130 45.900 45.944 45.989 46.034 46.079 46.123 46.168 46.213 46.258 46.302 46.347 11301140 46.347 46.392 46.437 46.481 46.526 46.571 46.616 46.660 46.705 46.750 46.794 1140

1150 46.794 46.839 46.884 46.929 46.973 47.018 47.063 47.107 47.152 47.197 47.241 11501160 47.241 47.286 47.331 47.375 47.420 47.465 47.509 47.554 47.599 47.643 47.688 11601170 47.688 47.733 47.777 47.822 47.867 47.911 47.956 48.001 48.045 48.090 48.135 11701180 48.135 48.179 48.224 48.268 48.313 48.358 48.402 48.447 48.492 48.536 48.581 11801190 48.581 48.625 48.670 48.715 48.759 48.804 48.848 48.893 48.937 48.982 49.027 1190

1200 49.027 49.071 49.116 49.160 49.205 49.249 49.294 49.338 49.383 49.428 49.472 12001210 49.472 49.517 49.561 49.606 49.650 49.695 49.739 49.784 49.828 49.873 49.917 12101220 49.917 49.962 50.006 50.051 50.095 50.140 50.184 50.229 50.273 50.318 50.362 12201230 50.362 50.407 50.451 50.495 50.540 50.584 50.629 50.673 50.718 50.762 50.807 12301240 50.807 50.851 50.895 50.940 50.984 51.029 51.073 51.118 51.162 51.206 51.251 1240

1250 51.251 51.295 51.340 51.384 51.428 51.473 51.517 51.561 51.606 51.650 51.695 12501260 51.695 51.739 51.783 51.828 51.872 51.916 51.961 52.005 52.049 52.094 52.138 12601270 52.138 52.182 52.227 52.271 52.315 52.360 52.404 52.448 52.493 52.537 52.581 12701280 52.581 52.625 52.670 52.714 52.758 52.803 52.847 52.891 52.935 52.980 53.024 12801290 53.024 53.068 53.112 53.157 53.201 53.245 53.289 53.334 53.378 53.422 53.466 1290

1300 53.466 53.510 53.555 53.599 53.643 53.687 53.732 53.776 53.820 53.864 53.908 13001310 53.908 53.952 53.997 54.041 54.085 54.129 54.173 54.218 54.262 54.306 54.350 13101320 54.350 54.394 54.438 54.482 54.527 54.571 54.615 54.659 54.703 54.747 54.791 13201330 54.791 54.835 54.879 54.924 54.968 55.012 55.056 55.100 55.144 55.188 55.232 13301340 55.232 55.276 55.320 55.364 55.408 55.453 55.497 55.541 55.585 55.629 55.673 1340

1350 55.673 55.717 55.761 55.805 55.849 55.893 55.937 55.981 56.025 56.069 56.113 13501360 56.113 56.157 56.201 56.245 56.289 56.333 56.377 56.421 56.465 56.509 56.553 13601370 56.553 56.597 56.641 56.685 56.729 56.773 56.816 56.860 56.904 56.948 56.992 13701380 56.992 57.036 57.080 57.124 57.168 57.212 57.256 57.300 57.344 57.387 57.431 13801390 57.431 57.475 57.519 57.563 57.607 57.651 57.695 57.738 57.782 57.826 57.870 1390

1400 57.870 57.914 57.958 58.002 58.045 58.089 58.133 58.177 58.221 58.265 58.308 14001410 58.308 58.352 58.396 58.440 58.484 58.527 58.571 58.615 58.659 58.702 58.746 14101420 58.746 58.790 58.834 58.878 58.921 58.965 59.009 59.053 59.096 59.140 59.184 14201430 59.184 59.228 59.271 59.315 59.359 59.402 59.446 59.490 59.534 59.577 59.621 14301440 59.621 59.665 59.708 59.752 59.796 59.839 59.883 59.927 59.970 60.014 60.058 1440

1450 60.058 60.101 60.145 60.189 60.232 60.276 60.320 60.363 60.407 60.451 60.494 14501460 60.494 60.538 60.581 60.625 60.669 60.712 60.756 60.799 60.843 60.887 60.930 14601470 60.930 60.974 61.017 61.061 61.105 61.148 61.192 61.235 61.279 61.322 61.366 14701480 61.366 61.409 61.453 61.496 61.540 61.583 61.627 61.671 61.714 61.758 61.801 14801490 61.801 61.845 61.888 61.932 61.975 62.018 62.062 62.105 62.149 62.192 62.236 1490

1500 62.236 62.279 62.323 62.366 62.410 62.453 62.496 62.540 62.583 62.627 62.670 15001510 62.670 62.714 62.757 62.800 62.844 62.887 62.931 62.974 63.017 63.061 63.104 15101520 63.104 63.148 63.191 63.234 63.278 63.321 63.364 63.408 63.451 63.494 63.538 15201530 63.538 63.581 63.624 63.668 63.711 63.754 63.798 63.841 63.884 63.927 63.971 15301540 63.971 64.014 64.057 64.101 64.144 64.187 64.230 64.274 64.317 64.360 64.403 1540

1550 64.403 64.447 64.490 64.533 64.576 64.619 64.663 64.706 64.749 64.792 64.835 15501560 64.835 64.879 64.922 64.965 65.008 65.051 65.094 65.138 65.181 65.224 65.267 15601570 65.267 65.310 65.353 65.396 65.440 65.483 65.526 65.569 65.612 65.655 65.698 15701580 65.698 65.741 65.784 65.827 65.871 65.914 65.957 66.000 66.043 66.086 66.129 15801590 66.129 66.172 66.215 66.258 66.301 66.344 66.387 66.430 66.473 66.516 66.559 1590

1600 66.559 66.602 66.645 66.688 66.731 66.774 66.817 66.860 66.903 66.946 66.989 16001610 66.989 67.031 67.074 67.117 67.160 67.203 67.246 67.289 67.332 67.375 67.418 16101620 67.418 67.460 67.503 67.546 67.589 67.632 67.675 67.718 67.760 67.803 67.846 16201630 67.846 67.889 67.932 67.974 68.017 68.060 68.103 68.146 68.188 68.231 68.274 16301640 68.274 68.317 68.359 68.402 68.445 68.488 68.530 68.573 68.616 68.659 68.701 1640

1650 68.701 68.744 68.787 68.829 68.872 68.915 68.957 69.000 69.043 69.085 69.128 16501660 69.128 69.171 69.213 69.256 69.298 69.341 69.384 69.426 69.469 69.511 69.554 16601670 69.554 69.597 69.639 69.682 69.724 69.767 69.809 69.852 69.894 69.937 69.979 16701680 69.979 70.022 70.064 70.107 70.149 70.192 70.234 70.277 70.319 70.362 70.404 16801690 70.404 70.447 70.489 70.531 70.574 70.616 70.659 70.701 70.744 70.786 70.828 1690

1700 70.828 70.871 70.913 70.955 70.998 71.040 71.082 71.125 71.167 71.209 71.252 17001710 71.252 71.294 71.336 71.379 71.421 71.463 71.506 71.548 71.590 71.632 71.675 17101720 71.675 71.717 71.759 71.801 71.844 71.886 71.928 71.970 72.012 72.055 72.097 17201730 72.097 72.139 72.181 72.223 72.266 72.308 72.350 72.392 72.434 72.476 72.518 17301740 72.518 72.561 72.603 72.645 72.687 72.729 72.771 72.813 72.855 72.897 72.939 1740

1750 72.939 72.981 73.023 73.066 73.108 73.150 73.192 73.234 73.276 73.318 73.360 17501760 73.360 73.402 73.444 73.486 73.528 73.570 73.612 73.654 73.696 73.738 73.780 17601770 73.780 73.821 73.863 73.905 73.947 73.989 74.031 74.073 74.115 74.157 74.199 17701780 74.199 74.241 74.283 74.324 74.366 74.408 74.450 74.492 74.534 74.576 74.618 17801790 74.618 74.659 74.701 74.743 74.785 74.827 74.869 74.910 74.952 74.994 75.036 1790

1800 75.036 75.078 75.120 75.161 75.203 75.245 75.287 75.329 75.370 75.412 75.454 18001810 75.454 75.496 75.538 75.579 75.621 75.663 75.705 75.746 75.788 75.830 75.872 18101820 75.872 75.913 75.955 75.997 76.039 76.081 76.122 76.164 76.206 76.248 76.289 18201830 76.289 76.331 76.373 1830

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 328 to 1652°F– 200 to 900°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 1.7°C or 0.5% Above 0°C1.7°C or 1.0°C Below 0°CSpecial: 1.0°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Limited Use in Vacuum orReducing; Highest EMF Change per DegreeTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°F EE

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

ThermocoupleGrade

Nickel-Chromiumvs.

Copper-Nickel

ExtensionGrade

+–


+–


Z-223


°F -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

-450 -6.258 -6.257 -6.256 -6.255 -6.254 -450

-440 -6.254 -6.253 -6.252 -6.251 -6.250 -6.248 -6.247 -6.245 -6.243 -6.242 -6.240 -440-430 -6.240 -6.238 -6.236 -6.234 -6.232 -6.230 -6.227 -6.225 -6.222 -6.220 -6.217 -430-420 -6.217 -6.215 -6.212 -6.209 -6.206 -6.203 -6.200 -6.197 -6.194 -6.191 -6.187 -420-410 -6.187 -6.184 -6.180 -6.177 -6.173 -6.170 -6.166 -6.162 -6.158 -6.154 -6.150 -410-400 -6.150 -6.146 -6.141 -6.137 -6.133 -6.128 -6.124 -6.119 -6.115 -6.110 -6.105 -400

-390 -6.105 -6.100 -6.095 -6.090 -6.085 -6.080 -6.075 -6.069 -6.064 -6.059 -6.053 -390-380 -6.053 -6.047 -6.042 -6.036 -6.030 -6.025 -6.019 -6.013 -6.007 -6.001 -5.994 -380-370 -5.994 -5.988 -5.982 -5.976 -5.969 -5.963 -5.956 -5.950 -5.943 -5.937 -5.930 -370-360 -5.930 -5.923 -5.916 -5.909 -5.902 -5.896 -5.888 -5.881 -5.874 -5.867 -5.860 -360-350 -5.860 -5.853 -5.845 -5.838 -5.830 -5.823 -5.815 -5.808 -5.800 -5.792 -5.785 -350

-340 -5.785 -5.777 -5.769 -5.761 -5.753 -5.745 -5.737 -5.729 -5.721 -5.713 -5.705 -340-330 -5.705 -5.697 -5.688 -5.680 -5.672 -5.663 -5.655 -5.646 -5.638 -5.629 -5.620 -330-320 -5.620 -5.612 -5.603 -5.594 -5.585 -5.577 -5.568 -5.559 -5.550 -5.541 -5.532 -320-310 -5.532 -5.523 -5.513 -5.504 -5.495 -5.486 -5.476 -5.467 -5.458 -5.448 -5.439 -310-300 -5.439 -5.429 -5.420 -5.410 -5.400 -5.391 -5.381 -5.371 -5.361 -5.351 -5.341 -300

-290 -5.341 -5.332 -5.322 -5.312 -5.301 -5.291 -5.281 -5.271 -5.261 -5.250 -5.240 -290-280 -5.240 -5.230 -5.219 -5.209 -5.198 -5.188 -5.177 -5.167 -5.156 -5.145 -5.135 -280-270 -5.135 -5.124 -5.113 -5.102 -5.091 -5.081 -5.070 -5.059 -5.048 -5.036 -5.025 -270-260 -5.025 -5.014 -5.003 -4.992 -4.980 -4.969 -4.958 -4.946 -4.935 -4.923 -4.912 -260-250 -4.912 -4.900 -4.889 -4.877 -4.865 -4.854 -4.842 -4.830 -4.818 -4.806 -4.794 -250

-240 -4.794 -4.783 -4.771 -4.759 -4.746 -4.734 -4.722 -4.710 -4.698 -4.685 -4.673 -240-230 -4.673 -4.661 -4.648 -4.636 -4.624 -4.611 -4.599 -4.586 -4.573 -4.561 -4.548 -230-220 -4.548 -4.535 -4.523 -4.510 -4.497 -4.484 -4.471 -4.458 -4.445 -4.432 -4.419 -220-210 -4.419 -4.406 -4.393 -4.380 -4.366 -4.353 -4.340 -4.326 -4.313 -4.300 -4.286 -210-200 -4.286 -4.273 -4.259 -4.246 -4.232 -4.218 -4.205 -4.191 -4.177 -4.163 -4.149 -200

-190 -4.149 -4.136 -4.122 -4.108 -4.094 -4.080 -4.066 -4.052 -4.037 -4.023 -4.009 -190-180 -4.009 -3.995 -3.980 -3.966 -3.952 -3.937 -3.923 -3.908 -3.894 -3.879 -3.865 -180-170 -3.865 -3.850 -3.836 -3.821 -3.806 -3.791 -3.777 -3.762 -3.747 -3.732 -3.717 -170-160 -3.717 -3.702 -3.687 -3.672 -3.657 -3.642 -3.626 -3.611 -3.596 -3.581 -3.565 -160-150 -3.565 -3.550 -3.535 -3.519 -3.504 -3.488 -3.473 -3.457 -3.441 -3.426 -3.410 -150

-140 -3.410 -3.394 -3.379 -3.363 -3.347 -3.331 -3.315 -3.299 -3.283 -3.267 -3.251 -140-130 -3.251 -3.235 -3.219 -3.203 -3.187 -3.171 -3.154 -3.138 -3.122 -3.105 -3.089 -130-120 -3.089 -3.072 -3.056 -3.040 -3.023 -3.006 -2.990 -2.973 -2.956 -2.940 -2.923 -120-110 -2.923 -2.906 -2.889 -2.873 -2.856 -2.839 -2.822 -2.805 -2.788 -2.771 -2.754 -110-100 -2.754 -2.737 -2.719 -2.702 -2.685 -2.668 -2.651 -2.633 -2.616 -2.598 -2.581 -100

-90 -2.581 -2.564 -2.546 -2.529 -2.511 -2.493 -2.476 -2.458 -2.440 -2.423 -2.405 -90-80 -2.405 -2.387 -2.369 -2.351 -2.334 -2.316 -2.298 -2.280 -2.262 -2.244 -2.225 -80-70 -2.225 -2.207 -2.189 -2.171 -2.153 -2.134 -2.116 -2.098 -2.079 -2.061 -2.043 -70-60 -2.043 -2.024 -2.006 -1.987 -1.969 -1.950 -1.931 -1.913 -1.894 -1.875 -1.857 -60-50 -1.857 -1.838 -1.819 -1.800 -1.781 -1.762 -1.743 -1.724 -1.705 -1.686 -1.667 -50

-40 -1.667 -1.648 -1.629 -1.610 -1.591 -1.572 -1.552 -1.533 -1.514 -1.494 -1.475 -40-30 -1.475 -1.456 -1.436 -1.417 -1.397 -1.378 -1.358 -1.338 -1.319 -1.299 -1.279 -30-20 -1.279 -1.260 -1.240 -1.220 -1.200 -1.181 -1.161 -1.141 -1.121 -1.101 -1.081 -20-10 -1.081 -1.061 -1.041 -1.021 -1.001 -0.980 -0.960 -0.940 -0.920 -0.900 -0.879 -10

0 -0.879 -0.859 -0.839 -0.818 -0.798 -0.777 -0.757 -0.736 -0.716 -0.695 -0.675 0

0 -0.675 -0.654 -0.633 -0.613 -0.592 -0.571 -0.550 -0.530 -0.509 -0.488 -0.467 010 -0.467 -0.446 -0.425 -0.404 -0.383 -0.362 -0.341 -0.320 -0.299 -0.278 -0.256 1020 -0.256 -0.235 -0.214 -0.193 -0.171 -0.150 -0.129 -0.107 -0.086 -0.064 -0.043 2030 -0.043 -0.022 0.000 0.022 0.043 0.065 0.086 0.108 0.130 0.151 0.173 3040 0.173 0.195 0.216 0.238 0.260 0.282 0.303 0.325 0.347 0.369 0.391 40

50 0.391 0.413 0.435 0.457 0.479 0.501 0.523 0.545 0.567 0.589 0.611 5060 0.611 0.634 0.656 0.678 0.700 0.723 0.745 0.767 0.790 0.812 0.834 6070 0.834 0.857 0.879 0.902 0.924 0.947 0.969 0.992 1.015 1.037 1.060 7080 1.060 1.083 1.105 1.128 1.151 1.174 1.196 1.219 1.242 1.265 1.288 8090 1.288 1.311 1.334 1.357 1.380 1.403 1.426 1.449 1.472 1.496 1.519 90

100 1.519 1.542 1.565 1.588 1.612 1.635 1.658 1.682 1.705 1.729 1.752 100110 1.752 1.776 1.799 1.823 1.846 1.870 1.893 1.917 1.941 1.964 1.988 110120 1.988 2.012 2.036 2.060 2.083 2.107 2.131 2.155 2.179 2.203 2.227 120130 2.227 2.251 2.275 2.299 2.323 2.347 2.371 2.395 2.420 2.444 2.468 130140 2.468 2.492 2.517 2.541 2.565 2.590 2.614 2.639 2.663 2.687 2.712 140

150 2.712 2.737 2.761 2.786 2.810 2.835 2.860 2.884 2.909 2.934 2.958 150160 2.958 2.983 3.008 3.033 3.058 3.082 3.107 3.132 3.157 3.182 3.207 160170 3.207 3.232 3.257 3.282 3.307 3.333 3.358 3.383 3.408 3.433 3.459 170180 3.459 3.484 3.509 3.534 3.560 3.585 3.610 3.636 3.661 3.687 3.712 180190 3.712 3.738 3.763 3.789 3.814 3.840 3.866 3.891 3.917 3.943 3.968 190

200 3.968 3.994 4.020 4.046 4.071 4.097 4.123 4.149 4.175 4.201 4.227 200210 4.227 4.253 4.279 4.305 4.331 4.357 4.383 4.409 4.435 4.461 4.487 210220 4.487 4.513 4.540 4.566 4.592 4.618 4.645 4.671 4.697 4.724 4.750 220230 4.750 4.776 4.803 4.829 4.856 4.882 4.909 4.935 4.962 4.988 5.015 230240 5.015 5.042 5.068 5.095 5.122 5.148 5.175 5.202 5.228 5.255 5.282 240

250 5.282 5.309 5.336 5.363 5.389 5.416 5.443 5.470 5.497 5.524 5.551 250260 5.551 5.578 5.605 5.632 5.660 5.687 5.714 5.741 5.768 5.795 5.823 260270 5.823 5.850 5.877 5.904 5.932 5.959 5.986 6.014 6.041 6.068 6.096 270280 6.096 6.123 6.151 6.178 6.206 6.233 6.261 6.288 6.316 6.343 6.371 280290 6.371 6.399 6.426 6.454 6.482 6.510 6.537 6.565 6.593 6.621 6.648 290

300 6.648 6.676 6.704 6.732 6.760 6.788 6.816 6.844 6.872 6.900 6.928 300310 6.928 6.956 6.984 7.012 7.040 7.068 7.096 7.124 7.152 7.181 7.209 310320 7.209 7.237 7.265 7.294 7.322 7.350 7.378 7.407 7.435 7.463 7.492 320330 7.492 7.520 7.549 7.577 7.606 7.634 7.663 7.691 7.720 7.748 7.777 330340 7.777 7.805 7.834 7.863 7.891 7.920 7.949 7.977 8.006 8.035 8.064 340

350 8.064 8.092 8.121 8.150 8.179 8.208 8.237 8.266 8.294 8.323 8.352 350360 8.352 8.381 8.410 8.439 8.468 8.497 8.526 8.555 8.585 8.614 8.643 360370 8.643 8.672 8.701 8.730 8.759 8.789 8.818 8.847 8.876 8.906 8.935 370380 8.935 8.964 8.994 9.023 9.052 9.082 9.111 9.141 9.170 9.200 9.229 380390 9.229 9.259 9.288 9.318 9.347 9.377 9.406 9.436 9.466 9.495 9.525 390

400 9.525 9.555 9.584 9.614 9.644 9.673 9.703 9.733 9.763 9.793 9.822 400410 9.822 9.852 9.882 9.912 9.942 9.972 10.002 10.032 10.062 10.092 10.122 410420 10.122 10.152 10.182 10.212 10.242 10.272 10.302 10.332 10.362 10.392 10.423 420430 10.423 10.453 10.483 10.513 10.543 10.574 10.604 10.634 10.664 10.695 10.725 430440 10.725 10.755 10.786 10.816 10.847 10.877 10.907 10.938 10.968 10.999 11.029 440

450 11.029 11.060 11.090 11.121 11.151 11.182 11.213 11.243 11.274 11.304 11.335 450460 11.335 11.366 11.396 11.427 11.458 11.489 11.519 11.550 11.581 11.612 11.643 460470 11.643 11.673 11.704 11.735 11.766 11.797 11.828 11.859 11.890 11.920 11.951 470480 11.951 11.982 12.013 12.044 12.075 12.106 12.138 12.169 12.200 12.231 12.262 480490 12.262 12.293 12.324 12.355 12.386 12.418 12.449 12.480 12.511 12.543 12.574 490

500 12.574 12.605 12.636 12.668 12.699 12.730 12.762 12.793 12.824 12.856 12.887 500510 12.887 12.919 12.950 12.982 13.013 13.045 13.076 13.108 13.139 13.171 13.202 510520 13.202 13.234 13.265 13.297 13.328 13.360 13.392 13.423 13.455 13.487 13.518 520530 13.518 13.550 13.582 13.614 13.645 13.677 13.709 13.741 13.772 13.804 13.836 530540 13.836 13.868 13.900 13.932 13.964 13.995 14.027 14.059 14.091 14.123 14.155 540

550 14.155 14.187 14.219 14.251 14.283 14.315 14.347 14.379 14.411 14.444 14.476 550560 14.476 14.508 14.540 14.572 14.604 14.636 14.669 14.701 14.733 14.765 14.797 560570 14.797 14.830 14.862 14.894 14.926 14.959 14.991 15.023 15.056 15.088 15.121 570580 15.121 15.153 15.185 15.218 15.250 15.283 15.315 15.347 15.380 15.412 15.445 580590 15.445 15.477 15.510 15.543 15.575 15.608 15.640 15.673 15.705 15.738 15.771 590

600 15.771 15.803 15.836 15.869 15.901 15.934 15.967 15.999 16.032 16.065 16.098 600610 16.098 16.130 16.163 16.196 16.229 16.262 16.295 16.327 16.360 16.393 16.426 610620 16.426 16.459 16.492 16.525 16.558 16.591 16.624 16.657 16.690 16.723 16.756 620630 16.756 16.789 16.822 16.855 16.888 16.921 16.954 16.987 17.020 17.053 17.086 630640 17.086 17.120 17.153 17.186 17.219 17.252 17.286 17.319 17.352 17.385 17.418 640

650 17.418 17.452 17.485 17.518 17.552 17.585 17.618 17.652 17.685 17.718 17.752 650660 17.752 17.785 17.819 17.852 17.886 17.919 17.952 17.986 18.019 18.053 18.086 660670 18.086 18.120 18.153 18.187 18.221 18.254 18.288 18.321 18.355 18.389 18.422 670680 18.422 18.456 18.490 18.523 18.557 18.591 18.624 18.658 18.692 18.725 18.759 680690 18.759 18.793 18.827 18.861 18.894 18.928 18.962 18.996 19.030 19.064 19.097 690

700 19.097 19.131 19.165 19.199 19.233 19.267 19.301 19.335 19.369 19.403 19.437 700710 19.437 19.471 19.505 19.539 19.573 19.607 19.641 19.675 19.709 19.743 19.777 710720 19.777 19.811 19.845 19.879 19.913 19.947 19.982 20.016 20.050 20.084 20.118 720730 20.118 20.152 20.187 20.221 20.255 20.289 20.323 20.358 20.392 20.426 20.460 730740 20.460 20.495 20.529 20.563 20.597 20.632 20.666 20.700 20.735 20.769 20.803 740

750 20.803 20.838 20.872 750

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 328 to 662°F– 200 to 350°CExtension Grade– 76 to 212°F– 60 to 100°CLIMITS OF ERROR(whichever is greater)Standard: 1.0°C or 0.75% Above 0°C1.0°C or 1.5% Below 0°CSpecial: 0.5°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Mild Oxidizing, Reducing Vacuum or Insert; Good Where Moisture Is Present;Low Temperature and Cryogenic ApplicationsTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°FTT

ThermocoupleGrade

Coppervs.

Copper-Nickel

ExtensionGrade

+–

+–


+–


Z-224

Z


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

-50 -0.236 -0.233 -0.231 -0.229 -0.227 -0.224 -0.222 -0.220 -0.218 -50

-40 -0.218 -0.215 -0.213 -0.211 -0.208 -0.206 -0.204 -0.201 -0.199 -0.197 -0.194 -40-30 -0.194 -0.192 -0.190 -0.187 -0.185 -0.182 -0.180 -0.178 -0.175 -0.173 -0.170 -30-20 -0.170 -0.168 -0.165 -0.163 -0.160 -0.158 -0.155 -0.153 -0.150 -0.148 -0.145 -20-10 -0.145 -0.142 -0.140 -0.137 -0.135 -0.132 -0.129 -0.127 -0.124 -0.122 -0.119 -10

0 -0.119 -0.116 -0.114 -0.111 -0.108 -0.106 -0.103 -0.100 -0.097 -0.095 -0.092 0

0 -0.092 -0.089 -0.086 -0.084 -0.081 -0.078 -0.075 -0.073 -0.070 -0.067 -0.064 010 -0.064 -0.061 -0.058 -0.056 -0.053 -0.050 -0.047 -0.044 -0.041 -0.038 -0.035 1020 -0.035 -0.033 -0.030 -0.027 -0.024 -0.021 -0.018 -0.015 -0.012 -0.009 -0.006 2030 -0.006 -0.003 0.000 0.003 0.006 0.009 0.012 0.015 0.018 0.021 0.024 3040 0.024 0.027 0.030 0.033 0.037 0.040 0.043 0.046 0.049 0.052 0.055 40

50 0.055 0.058 0.062 0.065 0.068 0.071 0.074 0.077 0.081 0.084 0.087 5060 0.087 0.090 0.093 0.097 0.100 0.103 0.106 0.110 0.113 0.116 0.119 6070 0.119 0.123 0.126 0.129 0.133 0.136 0.139 0.143 0.146 0.149 0.153 7080 0.153 0.156 0.159 0.163 0.166 0.169 0.173 0.176 0.180 0.183 0.186 8090 0.186 0.190 0.193 0.197 0.200 0.204 0.207 0.210 0.214 0.217 0.221 90

100 0.221 0.224 0.228 0.231 0.235 0.238 0.242 0.245 0.249 0.252 0.256 100110 0.256 0.260 0.263 0.267 0.270 0.274 0.277 0.281 0.285 0.288 0.292 110120 0.292 0.295 0.299 0.303 0.306 0.310 0.313 0.317 0.321 0.324 0.328 120130 0.328 0.332 0.335 0.339 0.343 0.346 0.350 0.354 0.357 0.361 0.365 130140 0.365 0.369 0.372 0.376 0.380 0.384 0.387 0.391 0.395 0.399 0.402 140

150 0.402 0.406 0.410 0.414 0.417 0.421 0.425 0.429 0.433 0.436 0.440 150160 0.440 0.444 0.448 0.452 0.456 0.459 0.463 0.467 0.471 0.475 0.479 160170 0.479 0.483 0.487 0.490 0.494 0.498 0.502 0.506 0.510 0.514 0.518 170180 0.518 0.522 0.526 0.530 0.534 0.538 0.541 0.545 0.549 0.553 0.557 180190 0.557 0.561 0.565 0.569 0.573 0.577 0.581 0.585 0.589 0.593 0.597 190

200 0.597 0.601 0.605 0.609 0.613 0.617 0.622 0.626 0.630 0.634 0.638 200210 0.638 0.642 0.646 0.650 0.654 0.658 0.662 0.666 0.670 0.675 0.679 210220 0.679 0.683 0.687 0.691 0.695 0.699 0.703 0.708 0.712 0.716 0.720 220230 0.720 0.724 0.728 0.732 0.737 0.741 0.745 0.749 0.753 0.758 0.762 230240 0.762 0.766 0.770 0.774 0.779 0.783 0.787 0.791 0.795 0.800 0.804 240

250 0.804 0.808 0.812 0.817 0.821 0.825 0.829 0.834 0.838 0.842 0.847 250260 0.847 0.851 0.855 0.859 0.864 0.868 0.872 0.877 0.881 0.885 0.889 260270 0.889 0.894 0.898 0.902 0.907 0.911 0.915 0.920 0.924 0.928 0.933 270280 0.933 0.937 0.942 0.946 0.950 0.955 0.959 0.963 0.968 0.972 0.977 280290 0.977 0.981 0.985 0.990 0.994 0.998 1.003 1.007 1.012 1.016 1.021 290

300 1.021 1.025 1.029 1.034 1.038 1.043 1.047 1.052 1.056 1.061 1.065 300310 1.065 1.069 1.074 1.078 1.083 1.087 1.092 1.096 1.101 1.105 1.110 310320 1.110 1.114 1.119 1.123 1.128 1.132 1.137 1.141 1.146 1.150 1.155 320330 1.155 1.159 1.164 1.168 1.173 1.177 1.182 1.186 1.191 1.196 1.200 330340 1.200 1.205 1.209 1.214 1.218 1.223 1.227 1.232 1.237 1.241 1.246 340

350 1.246 1.250 1.255 1.260 1.264 1.269 1.273 1.278 1.283 1.287 1.292 350360 1.292 1.296 1.301 1.306 1.310 1.315 1.319 1.324 1.329 1.333 1.338 360370 1.338 1.343 1.347 1.352 1.357 1.361 1.366 1.371 1.375 1.380 1.385 370380 1.385 1.389 1.394 1.399 1.403 1.408 1.413 1.417 1.422 1.427 1.431 380390 1.431 1.436 1.441 1.445 1.450 1.455 1.460 1.464 1.469 1.474 1.478 390

400 1.478 1.483 1.488 1.493 1.497 1.502 1.507 1.512 1.516 1.521 1.526 400410 1.526 1.531 1.535 1.540 1.545 1.550 1.554 1.559 1.564 1.569 1.573 410420 1.573 1.578 1.583 1.588 1.592 1.597 1.602 1.607 1.612 1.616 1.621 420430 1.621 1.626 1.631 1.636 1.640 1.645 1.650 1.655 1.660 1.664 1.669 430440 1.669 1.674 1.679 1.684 1.689 1.693 1.698 1.703 1.708 1.713 1.718 440

450 1.718 1.722 1.727 1.732 1.737 1.742 1.747 1.752 1.756 1.761 1.766 450460 1.766 1.771 1.776 1.781 1.786 1.790 1.795 1.800 1.805 1.810 1.815 460470 1.815 1.820 1.825 1.829 1.834 1.839 1.844 1.849 1.854 1.859 1.864 470480 1.864 1.869 1.874 1.878 1.883 1.888 1.893 1.898 1.903 1.908 1.913 480490 1.913 1.918 1.923 1.928 1.933 1.938 1.942 1.947 1.952 1.957 1.962 490

500 1.962 1.967 1.972 1.977 1.982 1.987 1.992 1.997 2.002 2.007 2.012 500510 2.012 2.017 2.022 2.027 2.032 2.037 2.042 2.047 2.052 2.057 2.062 510520 2.062 2.067 2.072 2.076 2.081 2.086 2.091 2.096 2.101 2.106 2.111 520530 2.111 2.116 2.121 2.126 2.131 2.136 2.141 2.147 2.152 2.157 2.162 530540 2.162 2.167 2.172 2.177 2.182 2.187 2.192 2.197 2.202 2.207 2.212 540

550 2.212 2.217 2.222 2.227 2.232 2.237 2.242 2.247 2.252 2.257 2.262 550560 2.262 2.267 2.272 2.277 2.283 2.288 2.293 2.298 2.303 2.308 2.313 560570 2.313 2.318 2.323 2.328 2.333 2.338 2.343 2.348 2.354 2.359 2.364 570580 2.364 2.369 2.374 2.379 2.384 2.389 2.394 2.399 2.404 2.410 2.415 580590 2.415 2.420 2.425 2.430 2.435 2.440 2.445 2.450 2.455 2.461 2.466 590

600 2.466 2.471 2.476 2.481 2.486 2.491 2.496 2.502 2.507 2.512 2.517 600610 2.517 2.522 2.527 2.532 2.537 2.543 2.548 2.553 2.558 2.563 2.568 610620 2.568 2.574 2.579 2.584 2.589 2.594 2.599 2.604 2.610 2.615 2.620 620630 2.620 2.625 2.630 2.635 2.641 2.646 2.651 2.656 2.661 2.666 2.672 630640 2.672 2.677 2.682 2.687 2.692 2.697 2.703 2.708 2.713 2.718 2.723 640

650 2.723 2.729 2.734 2.739 2.744 2.749 2.755 2.760 2.765 2.770 2.775 650660 2.775 2.781 2.786 2.791 2.796 2.801 2.807 2.812 2.817 2.822 2.827 660670 2.827 2.833 2.838 2.843 2.848 2.854 2.859 2.864 2.869 2.874 2.880 670680 2.880 2.885 2.890 2.895 2.901 2.906 2.911 2.916 2.922 2.927 2.932 680690 2.932 2.937 2.943 2.948 2.953 2.958 2.964 2.969 2.974 2.979 2.985 690

700 2.985 2.990 2.995 3.000 3.006 3.011 3.016 3.021 3.027 3.032 3.037 700710 3.037 3.042 3.048 3.053 3.058 3.063 3.069 3.074 3.079 3.085 3.090 710720 3.090 3.095 3.100 3.106 3.111 3.116 3.122 3.127 3.132 3.137 3.143 720730 3.143 3.148 3.153 3.159 3.164 3.169 3.174 3.180 3.185 3.190 3.196 730740 3.196 3.201 3.206 3.212 3.217 3.222 3.227 3.233 3.238 3.243 3.249 740

750 3.249 3.254 3.259 3.265 3.270 3.275 3.281 3.286 3.291 3.297 3.302 750760 3.302 3.307 3.313 3.318 3.323 3.329 3.334 3.339 3.345 3.350 3.355 760770 3.355 3.361 3.366 3.371 3.377 3.382 3.387 3.393 3.398 3.403 3.409 770780 3.409 3.414 3.419 3.425 3.430 3.435 3.441 3.446 3.451 3.457 3.462 780790 3.462 3.468 3.473 3.478 3.484 3.489 3.494 3.500 3.505 3.510 3.516 790

800 3.516 3.521 3.527 3.532 3.537 3.543 3.548 3.553 3.559 3.564 3.570 800810 3.570 3.575 3.580 3.586 3.591 3.596 3.602 3.607 3.613 3.618 3.623 810820 3.623 3.629 3.634 3.640 3.645 3.650 3.656 3.661 3.667 3.672 3.677 820830 3.677 3.683 3.688 3.694 3.699 3.704 3.710 3.715 3.721 3.726 3.731 830840 3.731 3.737 3.742 3.748 3.753 3.758 3.764 3.769 3.775 3.780 3.786 840

850 3.786 3.791 3.796 3.802 3.807 3.813 3.818 3.823 3.829 3.834 3.840 850860 3.840 3.845 3.851 3.856 3.862 3.867 3.872 3.878 3.883 3.889 3.894 860870 3.894 3.900 3.905 3.910 3.916 3.921 3.927 3.932 3.938 3.943 3.949 870880 3.949 3.954 3.959 3.965 3.970 3.976 3.981 3.987 3.992 3.998 4.003 880890 4.003 4.009 4.014 4.020 4.025 4.030 4.036 4.041 4.047 4.052 4.058 890

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 2642°F0 to 1450°CExtension Grade32 to 300°F0 to 150°CLIMITS OF ERROR(whichever is greater)Standard: 1.5°C or 0.25%Special: 0.6°C or 0.1%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High Temperature TEMPERATURE IN DEGREES °FFREFERENCE JUNCTION AT 32°F SS

°F -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

ThermocoupleGrade


Platinum

ExtensionGrade

+–


NONEESTABLISHED

+–

+–


Z-225


°F -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

900 4.058 4.063 4.069 4.074 4.080 4.085 4.091 4.096 4.102 4.107 4.113 900910 4.113 4.118 4.123 4.129 4.134 4.140 4.145 4.151 4.156 4.162 4.167 910920 4.167 4.173 4.178 4.184 4.189 4.195 4.200 4.206 4.211 4.217 4.222 920930 4.222 4.228 4.233 4.239 4.244 4.250 4.255 4.261 4.266 4.272 4.277 930940 4.277 4.283 4.288 4.294 4.299 4.305 4.310 4.316 4.321 4.327 4.332 940

950 4.332 4.338 4.343 4.349 4.355 4.360 4.366 4.371 4.377 4.382 4.388 950960 4.388 4.393 4.399 4.404 4.410 4.415 4.421 4.426 4.432 4.437 4.443 960970 4.443 4.449 4.454 4.460 4.465 4.471 4.476 4.482 4.487 4.493 4.498 970980 4.498 4.504 4.510 4.515 4.521 4.526 4.532 4.537 4.543 4.548 4.554 980990 4.554 4.559 4.565 4.571 4.576 4.582 4.587 4.593 4.598 4.604 4.610 990

1000 4.610 4.615 4.621 4.626 4.632 4.637 4.643 4.648 4.654 4.660 4.665 10001010 4.665 4.671 4.676 4.682 4.688 4.693 4.699 4.704 4.710 4.715 4.721 10101020 4.721 4.727 4.732 4.738 4.743 4.749 4.755 4.760 4.766 4.771 4.777 10201030 4.777 4.782 4.788 4.794 4.799 4.805 4.810 4.816 4.822 4.827 4.833 10301040 4.833 4.838 4.844 4.850 4.855 4.861 4.866 4.872 4.878 4.883 4.889 1040

1050 4.889 4.895 4.900 4.906 4.911 4.917 4.923 4.928 4.934 4.939 4.945 10501060 4.945 4.951 4.956 4.962 4.968 4.973 4.979 4.984 4.990 4.996 5.001 10601070 5.001 5.007 5.013 5.018 5.024 5.030 5.035 5.041 5.046 5.052 5.058 10701080 5.058 5.063 5.069 5.075 5.080 5.086 5.092 5.097 5.103 5.109 5.114 10801090 5.114 5.120 5.125 5.131 5.137 5.142 5.148 5.154 5.159 5.165 5.171 1090

1100 5.171 5.176 5.182 5.188 5.193 5.199 5.205 5.210 5.216 5.222 5.227 11001110 5.227 5.233 5.239 5.244 5.250 5.256 5.261 5.267 5.273 5.278 5.284 11101120 5.284 5.290 5.295 5.301 5.307 5.312 5.318 5.324 5.330 5.335 5.341 11201130 5.341 5.347 5.352 5.358 5.364 5.369 5.375 5.381 5.386 5.392 5.398 11301140 5.398 5.404 5.409 5.415 5.421 5.426 5.432 5.438 5.443 5.449 5.455 1140

1150 5.455 5.461 5.466 5.472 5.478 5.483 5.489 5.495 5.501 5.506 5.512 11501160 5.512 5.518 5.523 5.529 5.535 5.541 5.546 5.552 5.558 5.563 5.569 11601170 5.569 5.575 5.581 5.586 5.592 5.598 5.604 5.609 5.615 5.621 5.627 11701180 5.627 5.632 5.638 5.644 5.649 5.655 5.661 5.667 5.672 5.678 5.684 11801190 5.684 5.690 5.695 5.701 5.707 5.713 5.718 5.724 5.730 5.736 5.741 1190

1200 5.741 5.747 5.753 5.759 5.764 5.770 5.776 5.782 5.788 5.793 5.799 12001210 5.799 5.805 5.811 5.816 5.822 5.828 5.834 5.839 5.845 5.851 5.857 12101220 5.857 5.863 5.868 5.874 5.880 5.886 5.891 5.897 5.903 5.909 5.915 12201230 5.915 5.920 5.926 5.932 5.938 5.944 5.949 5.955 5.961 5.967 5.972 12301240 5.972 5.978 5.984 5.990 5.996 6.001 6.007 6.013 6.019 6.025 6.030 1240

1250 6.030 6.036 6.042 6.048 6.054 6.060 6.065 6.071 6.077 6.083 6.089 12501260 6.089 6.094 6.100 6.106 6.112 6.118 6.124 6.129 6.135 6.141 6.147 12601270 6.147 6.153 6.158 6.164 6.170 6.176 6.182 6.188 6.193 6.199 6.205 12701280 6.205 6.211 6.217 6.223 6.228 6.234 6.240 6.246 6.252 6.258 6.264 12801290 6.264 6.269 6.275 6.281 6.287 6.293 6.299 6.305 6.310 6.316 6.322 1290

1300 6.322 6.328 6.334 6.340 6.346 6.351 6.357 6.363 6.369 6.375 6.381 13001310 6.381 6.387 6.392 6.398 6.404 6.410 6.416 6.422 6.428 6.434 6.439 13101320 6.439 6.445 6.451 6.457 6.463 6.469 6.475 6.481 6.486 6.492 6.498 13201330 6.498 6.504 6.510 6.516 6.522 6.528 6.534 6.539 6.545 6.551 6.557 13301340 6.557 6.563 6.569 6.575 6.581 6.587 6.593 6.598 6.604 6.610 6.616 1340

1350 6.616 6.622 6.628 6.634 6.640 6.646 6.652 6.658 6.664 6.669 6.675 13501360 6.675 6.681 6.687 6.693 6.699 6.705 6.711 6.717 6.723 6.729 6.735 13601370 6.735 6.741 6.746 6.752 6.758 6.764 6.770 6.776 6.782 6.788 6.794 13701380 6.794 6.800 6.806 6.812 6.818 6.824 6.830 6.836 6.842 6.847 6.853 13801390 6.853 6.859 6.865 6.871 6.877 6.883 6.889 6.895 6.901 6.907 6.913 1390

1400 6.913 6.919 6.925 6.931 6.937 6.943 6.949 6.955 6.961 6.967 6.973 14001410 6.973 6.979 6.985 6.991 6.997 7.003 7.008 7.014 7.020 7.026 7.032 14101420 7.032 7.038 7.044 7.050 7.056 7.062 7.068 7.074 7.080 7.086 7.092 14201430 7.092 7.098 7.104 7.110 7.116 7.122 7.128 7.134 7.140 7.146 7.152 14301440 7.152 7.158 7.164 7.170 7.176 7.182 7.188 7.194 7.200 7.206 7.212 1440

1450 7.212 7.218 7.224 7.230 7.236 7.242 7.249 7.255 7.261 7.267 7.273 14501460 7.273 7.279 7.285 7.291 7.297 7.303 7.309 7.315 7.321 7.327 7.333 14601470 7.333 7.339 7.345 7.351 7.357 7.363 7.369 7.375 7.381 7.387 7.393 14701480 7.393 7.399 7.405 7.411 7.418 7.424 7.430 7.436 7.442 7.448 7.454 14801490 7.454 7.460 7.466 7.472 7.478 7.484 7.490 7.496 7.502 7.508 7.514 1490

1500 7.514 7.521 7.527 7.533 7.539 7.545 7.551 7.557 7.563 7.569 7.575 15001510 7.575 7.581 7.587 7.593 7.600 7.606 7.612 7.618 7.624 7.630 7.636 15101520 7.636 7.642 7.648 7.654 7.660 7.667 7.673 7.679 7.685 7.691 7.697 15201530 7.697 7.703 7.709 7.715 7.721 7.728 7.734 7.740 7.746 7.752 7.758 15301540 7.758 7.764 7.770 7.776 7.783 7.789 7.795 7.801 7.807 7.813 7.819 1540

1550 7.819 7.825 7.832 7.838 7.844 7.850 7.856 7.862 7.868 7.874 7.881 15501560 7.881 7.887 7.893 7.899 7.905 7.911 7.917 7.923 7.930 7.936 7.942 15601570 7.942 7.948 7.954 7.960 7.966 7.973 7.979 7.985 7.991 7.997 8.003 15701580 8.003 8.010 8.016 8.022 8.028 8.034 8.040 8.047 8.053 8.059 8.065 15801590 8.065 8.071 8.077 8.083 8.090 8.096 8.102 8.108 8.114 8.121 8.127 1590

1600 8.127 8.133 8.139 8.145 8.151 8.158 8.164 8.170 8.176 8.182 8.189 16001610 8.189 8.195 8.201 8.207 8.213 8.219 8.226 8.232 8.238 8.244 8.250 16101620 8.250 8.257 8.263 8.269 8.275 8.281 8.288 8.294 8.300 8.306 8.312 16201630 8.312 8.319 8.325 8.331 8.337 8.343 8.350 8.356 8.362 8.368 8.375 16301640 8.375 8.381 8.387 8.393 8.399 8.406 8.412 8.418 8.424 8.431 8.437 1640

1650 8.437 8.443 8.449 8.455 8.462 8.468 8.474 8.480 8.487 8.493 8.499 16501660 8.499 8.505 8.512 8.518 8.524 8.530 8.537 8.543 8.549 8.555 8.562 16601670 8.562 8.568 8.574 8.580 8.587 8.593 8.599 8.605 8.612 8.618 8.624 16701680 8.624 8.630 8.637 8.643 8.649 8.655 8.662 8.668 8.674 8.680 8.687 16801690 8.687 8.693 8.699 8.706 8.712 8.718 8.724 8.731 8.737 8.743 8.749 1690

1700 8.749 8.756 8.762 8.768 8.775 8.781 8.787 8.793 8.800 8.806 8.812 17001710 8.812 8.819 8.825 8.831 8.837 8.844 8.850 8.856 8.863 8.869 8.875 17101720 8.875 8.882 8.888 8.894 8.900 8.907 8.913 8.919 8.926 8.932 8.938 17201730 8.938 8.945 8.951 8.957 8.964 8.970 8.976 8.983 8.989 8.995 9.001 17301740 9.001 9.008 9.014 9.020 9.027 9.033 9.039 9.046 9.052 9.058 9.065 1740

1750 9.065 9.071 9.077 9.084 9.090 9.096 9.103 9.109 9.115 9.122 9.128 17501760 9.128 9.134 9.141 9.147 9.153 9.160 9.166 9.172 9.179 9.185 9.192 17601770 9.192 9.198 9.204 9.211 9.217 9.223 9.230 9.236 9.242 9.249 9.255 17701780 9.255 9.261 9.268 9.274 9.281 9.287 9.293 9.300 9.306 9.312 9.319 17801790 9.319 9.325 9.331 9.338 9.344 9.351 9.357 9.363 9.370 9.376 9.382 1790

1800 9.382 9.389 9.395 9.402 9.408 9.414 9.421 9.427 9.434 9.440 9.446 18001810 9.446 9.453 9.459 9.465 9.472 9.478 9.485 9.491 9.497 9.504 9.510 18101820 9.510 9.517 9.523 9.529 9.536 9.542 9.549 9.555 9.561 9.568 9.574 18201830 9.574 9.581 9.587 9.594 9.600 9.606 9.613 9.619 9.626 9.632 9.638 18301840 9.638 9.645 9.651 9.658 9.664 9.671 9.677 9.683 9.690 9.696 9.703 1840

1850 9.703 9.709 9.716 9.722 9.728 9.735 9.741 9.748 9.754 9.761 9.767 18501860 9.767 9.773 9.780 9.786 9.793 9.799 9.806 9.812 9.819 9.825 9.831 18601870 9.831 9.838 9.844 9.851 9.857 9.864 9.870 9.877 9.883 9.889 9.896 18701880 9.896 9.902 9.909 9.915 9.922 9.928 9.935 9.941 9.948 9.954 9.961 18801890 9.961 9.967 9.973 9.980 9.986 9.993 9.999 10.006 10.012 10.019 10.025 1890

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 2642°F0 to 1450°CExtension Grade32 to 300°F0 to 150°CLIMITS OF ERROR(whichever is greater)Standard: 1.5°C or 0.25%Special: 0.6°C or 0.1%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High Temperature TEMPERATURE IN DEGREES °FFREFERENCE JUNCTION AT 32°FSS

ThermocoupleGrade


Platinum

ExtensionGrade

+–

+–


NONEESTABLISHED

+–


Z-226

Z


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

1900 10.025 10.032 10.038 10.045 10.051 10.058 10.064 10.071 10.077 10.084 10.090 19001910 10.090 10.097 10.103 10.110 10.116 10.123 10.129 10.136 10.142 10.149 10.155 19101920 10.155 10.162 10.168 10.175 10.181 10.188 10.194 10.201 10.207 10.214 10.220 19201930 10.220 10.227 10.233 10.240 10.246 10.253 10.259 10.266 10.272 10.279 10.285 19301940 10.285 10.292 10.298 10.305 10.311 10.318 10.324 10.331 10.337 10.344 10.350 1940

1950 10.350 10.357 10.363 10.370 10.376 10.383 10.390 10.396 10.403 10.409 10.416 19501960 10.416 10.422 10.429 10.435 10.442 10.448 10.455 10.461 10.468 10.475 10.481 19601970 10.481 10.488 10.494 10.501 10.507 10.514 10.520 10.527 10.533 10.540 10.547 19701980 10.547 10.553 10.560 10.566 10.573 10.579 10.586 10.592 10.599 10.606 10.612 19801990 10.612 10.619 10.625 10.632 10.638 10.645 10.651 10.658 10.665 10.671 10.678 1990

2000 10.678 10.684 10.691 10.697 10.704 10.711 10.717 10.724 10.730 10.737 10.743 20002010 10.743 10.750 10.757 10.763 10.770 10.776 10.783 10.789 10.796 10.803 10.809 20102020 10.809 10.816 10.822 10.829 10.836 10.842 10.849 10.855 10.862 10.868 10.875 20202030 10.875 10.882 10.888 10.895 10.901 10.908 10.915 10.921 10.928 10.934 10.941 20302040 10.941 10.948 10.954 10.961 10.967 10.974 10.981 10.987 10.994 11.000 11.007 2040

2050 11.007 11.014 11.020 11.027 11.033 11.040 11.047 11.053 11.060 11.066 11.073 20502060 11.073 11.080 11.086 11.093 11.099 11.106 11.113 11.119 11.126 11.132 11.139 20602070 11.139 11.146 11.152 11.159 11.166 11.172 11.179 11.185 11.192 11.199 11.205 20702080 11.205 11.212 11.219 11.225 11.232 11.238 11.245 11.252 11.258 11.265 11.272 20802090 11.272 11.278 11.285 11.291 11.298 11.305 11.311 11.318 11.325 11.331 11.338 2090

2100 11.338 11.345 11.351 11.358 11.364 11.371 11.378 11.384 11.391 11.398 11.404 21002110 11.404 11.411 11.418 11.424 11.431 11.437 11.444 11.451 11.457 11.464 11.471 21102120 11.471 11.477 11.484 11.491 11.497 11.504 11.511 11.517 11.524 11.531 11.537 21202130 11.537 11.544 11.550 11.557 11.564 11.570 11.577 11.584 11.590 11.597 11.604 21302140 11.604 11.610 11.617 11.624 11.630 11.637 11.644 11.650 11.657 11.664 11.670 2140

2150 11.670 11.677 11.684 11.690 11.697 11.704 11.710 11.717 11.724 11.730 11.737 21502160 11.737 11.744 11.750 11.757 11.764 11.770 11.777 11.784 11.790 11.797 11.804 21602170 11.804 11.810 11.817 11.824 11.830 11.837 11.844 11.850 11.857 11.864 11.870 21702180 11.870 11.877 11.884 11.890 11.897 11.904 11.910 11.917 11.924 11.931 11.937 21802190 11.937 11.944 11.951 11.957 11.964 11.971 11.977 11.984 11.991 11.997 12.004 2190

2200 12.004 12.011 12.017 12.024 12.031 12.037 12.044 12.051 12.058 12.064 12.071 22002210 12.071 12.078 12.084 12.091 12.098 12.104 12.111 12.118 12.124 12.131 12.138 22102220 12.138 12.145 12.151 12.158 12.165 12.171 12.178 12.185 12.191 12.198 12.205 22202230 12.205 12.211 12.218 12.225 12.232 12.238 12.245 12.252 12.258 12.265 12.272 22302240 12.272 12.278 12.285 12.292 12.299 12.305 12.312 12.319 12.325 12.332 12.339 2240

2250 12.339 12.346 12.352 12.359 12.366 12.372 12.379 12.386 12.392 12.399 12.406 22502260 12.406 12.413 12.419 12.426 12.433 12.439 12.446 12.453 12.460 12.466 12.473 22602270 12.473 12.480 12.486 12.493 12.500 12.507 12.513 12.520 12.527 12.533 12.540 22702280 12.540 12.547 12.554 12.560 12.567 12.574 12.580 12.587 12.594 12.601 12.607 22802290 12.607 12.614 12.621 12.627 12.634 12.641 12.648 12.654 12.661 12.668 12.675 2290

2300 12.675 12.681 12.688 12.695 12.701 12.708 12.715 12.722 12.728 12.735 12.742 23002310 12.742 12.748 12.755 12.762 12.769 12.775 12.782 12.789 12.796 12.802 12.809 23102320 12.809 12.816 12.822 12.829 12.836 12.843 12.849 12.856 12.863 12.870 12.876 23202330 12.876 12.883 12.890 12.896 12.903 12.910 12.917 12.923 12.930 12.937 12.944 23302340 12.944 12.950 12.957 12.964 12.971 12.977 12.984 12.991 12.997 13.004 13.011 2340

2350 13.011 13.018 13.024 13.031 13.038 13.045 13.051 13.058 13.065 13.072 13.078 23502360 13.078 13.085 13.092 13.098 13.105 13.112 13.119 13.125 13.132 13.139 13.146 23602370 13.146 13.152 13.159 13.166 13.173 13.179 13.186 13.193 13.199 13.206 13.213 23702380 13.213 13.220 13.226 13.233 13.240 13.247 13.253 13.260 13.267 13.274 13.280 23802390 13.280 13.287 13.294 13.301 13.307 13.314 13.321 13.328 13.334 13.341 13.348 2390

2400 13.348 13.354 13.361 13.368 13.375 13.381 13.388 13.395 13.402 13.408 13.415 24002410 13.415 13.422 13.429 13.435 13.442 13.449 13.456 13.462 13.469 13.476 13.483 24102420 13.483 13.489 13.496 13.503 13.510 13.516 13.523 13.530 13.537 13.543 13.550 24202430 13.550 13.557 13.563 13.570 13.577 13.584 13.590 13.597 13.604 13.611 13.617 24302440 13.617 13.624 13.631 13.638 13.644 13.651 13.658 13.665 13.671 13.678 13.685 2440

2450 13.685 13.692 13.698 13.705 13.712 13.719 13.725 13.732 13.739 13.746 13.752 24502460 13.752 13.759 13.766 13.773 13.779 13.786 13.793 13.800 13.806 13.813 13.820 24602470 13.820 13.826 13.833 13.840 13.847 13.853 13.860 13.867 13.874 13.880 13.887 24702480 13.887 13.894 13.901 13.907 13.914 13.921 13.928 13.934 13.941 13.948 13.955 24802490 13.955 13.961 13.968 13.975 13.982 13.988 13.995 14.002 14.009 14.015 14.022 2490

2500 14.022 14.029 14.036 14.042 14.049 14.056 14.063 14.069 14.076 14.083 14.089 25002510 14.089 14.096 14.103 14.110 14.116 14.123 14.130 14.137 14.143 14.150 14.157 25102520 14.157 14.164 14.170 14.177 14.184 14.191 14.197 14.204 14.211 14.218 14.224 25202530 14.224 14.231 14.238 14.245 14.251 14.258 14.265 14.272 14.278 14.285 14.292 25302540 14.292 14.298 14.305 14.312 14.319 14.325 14.332 14.339 14.346 14.352 14.359 2540

2550 14.359 14.366 14.373 14.379 14.386 14.393 14.400 14.406 14.413 14.420 14.426 25502560 14.426 14.433 14.440 14.447 14.453 14.460 14.467 14.474 14.480 14.487 14.494 25602570 14.494 14.501 14.507 14.514 14.521 14.528 14.534 14.541 14.548 14.554 14.561 25702580 14.561 14.568 14.575 14.581 14.588 14.595 14.602 14.608 14.615 14.622 14.629 25802590 14.629 14.635 14.642 14.649 14.655 14.662 14.669 14.676 14.682 14.689 14.696 2590

2600 14.696 14.703 14.709 14.716 14.723 14.729 14.736 14.743 14.750 14.756 14.763 26002610 14.763 14.770 14.777 14.783 14.790 14.797 14.803 14.810 14.817 14.824 14.830 26102620 14.830 14.837 14.844 14.851 14.857 14.864 14.871 14.877 14.884 14.891 14.898 26202630 14.898 14.904 14.911 14.918 14.925 14.931 14.938 14.945 14.951 14.958 14.965 26302640 14.965 14.972 14.978 14.985 14.992 14.998 15.005 15.012 15.019 15.025 15.032 2640

2650 15.032 15.039 15.045 15.052 15.059 15.066 15.072 15.079 15.086 15.092 15.099 26502660 15.099 15.106 15.113 15.119 15.126 15.133 15.139 15.146 15.153 15.160 15.166 26602670 15.166 15.173 15.180 15.186 15.193 15.200 15.207 15.213 15.220 15.227 15.233 26702680 15.233 15.240 15.247 15.254 15.260 15.267 15.274 15.280 15.287 15.294 15.300 26802690 15.300 15.307 15.314 15.321 15.327 15.334 15.341 15.347 15.354 15.361 15.367 2690

2700 15.367 15.374 15.381 15.388 15.394 15.401 15.408 15.414 15.421 15.428 15.434 27002710 15.434 15.441 15.448 15.455 15.461 15.468 15.475 15.481 15.488 15.495 15.501 27102720 15.501 15.508 15.515 15.521 15.528 15.535 15.542 15.548 15.555 15.562 15.568 27202730 15.568 15.575 15.582 15.588 15.595 15.602 15.608 15.615 15.622 15.628 15.635 27302740 15.635 15.642 15.649 15.655 15.662 15.669 15.675 15.682 15.689 15.695 15.702 2740

2750 15.702 15.709 15.715 15.722 15.729 15.735 15.742 15.749 15.755 15.762 15.769 27502760 15.769 15.775 15.782 15.789 15.795 15.802 15.809 15.815 15.822 15.829 15.835 27602770 15.835 15.842 15.849 15.855 15.862 15.869 15.875 15.882 15.889 15.895 15.902 27702780 15.902 15.909 15.915 15.922 15.929 15.935 15.942 15.949 15.955 15.962 15.969 27802790 15.969 15.975 15.982 15.989 15.995 16.002 16.009 16.015 16.022 16.029 16.035 2790

2800 16.035 16.042 16.049 16.055 16.062 16.069 16.075 16.082 16.089 16.095 16.102 28002810 16.102 16.108 16.115 16.122 16.128 16.135 16.142 16.148 16.155 16.162 16.168 28102820 16.168 16.175 16.182 16.188 16.195 16.202 16.208 16.215 16.221 16.228 16.235 28202830 16.235 16.241 16.248 16.255 16.261 16.268 16.275 16.281 16.288 16.294 16.301 28302840 16.301 16.308 16.314 16.321 16.328 16.334 16.341 16.347 16.354 16.361 16.367 2840

2850 16.367 16.374 16.381 16.387 16.394 16.400 16.407 16.414 16.420 16.427 16.434 28502860 16.434 16.440 16.447 16.453 16.460 16.467 16.473 16.480 16.486 16.493 16.500 28602870 16.500 16.506 16.513 16.520 16.526 16.533 16.539 16.546 16.553 16.559 16.566 28702880 16.566 16.572 16.579 16.586 16.592 16.599 16.605 16.612 16.619 16.625 16.632 28802890 16.632 16.638 16.645 16.652 16.658 16.665 16.671 16.678 16.685 16.691 16.698 2890

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 2642°F0 to 1450°CExtension Grade32 to 300°F0 to 150°CLIMITS OF ERROR(whichever is greater)Standard: 1.5°C or 0.25%Special: 0.6°C or 0.1%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High Temperature TEMPERATURE IN DEGREES °FFREFERENCE JUNCTION AT 32°F SS

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

ThermocoupleGrade


Platinum

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-227


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

2900 16.698 16.704 16.711 16.718 16.724 16.731 16.737 16.744 16.751 16.757 16.764 29002910 16.764 16.770 16.777 16.783 16.790 16.797 16.803 16.810 16.816 16.823 16.829 29102920 16.829 16.836 16.843 16.849 16.856 16.862 16.869 16.876 16.882 16.889 16.895 29202930 16.895 16.902 16.908 16.915 16.922 16.928 16.935 16.941 16.948 16.954 16.961 29302940 16.961 16.967 16.974 16.981 16.987 16.994 17.000 17.007 17.013 17.020 17.026 2940

2950 17.026 17.033 17.040 17.046 17.053 17.059 17.066 17.072 17.079 17.085 17.092 29502960 17.092 17.099 17.105 17.112 17.118 17.125 17.131 17.138 17.144 17.151 17.157 29602970 17.157 17.164 17.171 17.177 17.184 17.190 17.197 17.203 17.210 17.216 17.223 29702980 17.223 17.229 17.236 17.242 17.249 17.255 17.262 17.268 17.275 17.282 17.288 29802990 17.288 17.295 17.301 17.308 17.314 17.321 17.327 17.334 17.340 17.347 17.353 2990

3000 17.353 17.360 17.366 17.373 17.379 17.386 17.392 17.399 17.405 17.412 17.418 30003010 17.418 17.425 17.431 17.438 17.444 17.451 17.457 17.464 17.470 17.477 17.483 30103020 17.483 17.490 17.496 17.503 17.509 17.516 17.522 17.529 17.535 17.542 17.548 30203030 17.548 17.555 17.561 17.568 17.574 17.581 17.587 17.594 17.600 17.607 17.613 30303040 17.613 17.620 17.626 17.633 17.639 17.645 17.652 17.658 17.665 17.671 17.678 3040

3050 17.678 17.684 17.691 17.697 17.704 17.710 17.717 17.723 17.729 17.736 17.742 30503060 17.742 17.749 17.755 17.762 17.768 17.775 17.781 17.787 17.794 17.800 17.807 30603070 17.807 17.813 17.819 17.826 17.832 17.839 17.845 17.852 17.858 17.864 17.871 30703080 17.871 17.877 17.884 17.890 17.896 17.903 17.909 17.915 17.922 17.928 17.935 30803090 17.935 17.941 17.947 17.954 17.960 17.966 17.973 17.979 17.985 17.992 17.998 3090

3100 17.998 18.004 18.011 18.017 18.023 18.030 18.036 18.042 18.049 18.055 18.061 31003110 18.061 18.068 18.074 18.080 18.086 18.093 18.099 18.105 18.112 18.118 18.124 31103120 18.124 18.130 18.137 18.143 18.149 18.155 18.162 18.168 18.174 18.180 18.187 31203130 18.187 18.193 18.199 18.205 18.211 18.218 18.224 18.230 18.236 18.242 18.248 31303140 18.248 18.255 18.261 18.267 18.273 18.279 18.285 18.292 18.298 18.304 18.310 3140

3150 18.310 18.316 18.322 18.328 18.334 18.341 18.347 18.353 18.359 18.365 18.371 31503160 18.371 18.377 18.383 18.389 18.395 18.401 18.407 18.413 18.419 18.425 18.431 31603170 18.431 18.437 18.443 18.449 18.455 18.461 18.467 18.473 18.479 18.485 18.491 31703180 18.491 18.497 18.503 18.509 18.515 18.521 18.527 18.533 18.539 18.545 18.551 31803190 18.551 18.557 18.562 18.568 18.574 18.580 18.586 18.592 18.598 18.603 18.609 3190

3200 18.609 18.615 18.621 18.627 18.633 18.638 18.644 18.650 18.656 18.661 18.667 32003210 18.667 18.673 18.679 18.684 18.690 3210

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 2642°F0 to 1450°CExtension Grade32 to 300°F0 to 150°CLIMITS OF ERROR(whichever is greater)Standard: 1.5°C or 0.25%Special: 0.6°C or 0.1%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High Temperature TEMPERATURE IN DEGREES °FFREFERENCE JUNCTION AT 32°FSS

ThermocoupleGrade


Platinum

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-228

Z


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

-50 -0.226 -0.224 -0.222 -0.220 -0.218 -0.216 -0.214 -0.212 -0.210 -50

-40 -0.210 -0.208 -0.205 -0.203 -0.201 -0.199 -0.197 -0.194 -0.192 -0.190 -0.188 -40-30 -0.188 -0.185 -0.183 -0.181 -0.179 -0.176 -0.174 -0.172 -0.169 -0.167 -0.165 -30-20 -0.165 -0.162 -0.160 -0.158 -0.155 -0.153 -0.150 -0.148 -0.145 -0.143 -0.141 -20-10 -0.141 -0.138 -0.136 -0.133 -0.131 -0.128 -0.126 -0.123 -0.121 -0.118 -0.116 -10

0 -0.116 -0.113 -0.110 -0.108 -0.105 -0.103 -0.100 -0.097 -0.095 -0.092 -0.090 0

0 -0.090 -0.087 -0.084 -0.082 -0.079 -0.076 -0.073 -0.071 -0.068 -0.065 -0.063 010 -0.063 -0.060 -0.057 -0.054 -0.051 -0.049 -0.046 -0.043 -0.040 -0.037 -0.035 1020 -0.035 -0.032 -0.029 -0.026 -0.023 -0.020 -0.017 -0.015 -0.012 -0.009 -0.006 2030 -0.006 -0.003 0.000 0.003 0.006 0.009 0.012 0.015 0.018 0.021 0.024 3040 0.024 0.027 0.030 0.033 0.036 0.039 0.042 0.045 0.048 0.051 0.054 40

50 0.054 0.057 0.060 0.064 0.067 0.070 0.073 0.076 0.079 0.082 0.086 5060 0.086 0.089 0.092 0.095 0.098 0.102 0.105 0.108 0.111 0.114 0.118 6070 0.118 0.121 0.124 0.127 0.131 0.134 0.137 0.141 0.144 0.147 0.151 7080 0.151 0.154 0.157 0.161 0.164 0.167 0.171 0.174 0.177 0.181 0.184 8090 0.184 0.188 0.191 0.194 0.198 0.201 0.205 0.208 0.212 0.215 0.218 90

100 0.218 0.222 0.225 0.229 0.232 0.236 0.239 0.243 0.246 0.250 0.254 100110 0.254 0.257 0.261 0.264 0.268 0.271 0.275 0.278 0.282 0.286 0.289 110120 0.289 0.293 0.296 0.300 0.304 0.307 0.311 0.315 0.318 0.322 0.326 120130 0.326 0.329 0.333 0.337 0.340 0.344 0.348 0.352 0.355 0.359 0.363 130140 0.363 0.366 0.370 0.374 0.378 0.382 0.385 0.389 0.393 0.397 0.400 140

150 0.400 0.404 0.408 0.412 0.416 0.420 0.423 0.427 0.431 0.435 0.439 150160 0.439 0.443 0.447 0.450 0.454 0.458 0.462 0.466 0.470 0.474 0.478 160170 0.478 0.482 0.486 0.489 0.493 0.497 0.501 0.505 0.509 0.513 0.517 170180 0.517 0.521 0.525 0.529 0.533 0.537 0.541 0.545 0.549 0.553 0.557 180190 0.557 0.561 0.565 0.569 0.573 0.578 0.582 0.586 0.590 0.594 0.598 190

200 0.598 0.602 0.606 0.610 0.614 0.618 0.623 0.627 0.631 0.635 0.639 200210 0.639 0.643 0.647 0.652 0.656 0.660 0.664 0.668 0.672 0.677 0.681 210220 0.681 0.685 0.689 0.693 0.698 0.702 0.706 0.710 0.715 0.719 0.723 220230 0.723 0.727 0.732 0.736 0.740 0.744 0.749 0.753 0.757 0.761 0.766 230240 0.766 0.770 0.774 0.779 0.783 0.787 0.792 0.796 0.800 0.805 0.809 240

250 0.809 0.813 0.818 0.822 0.826 0.831 0.835 0.839 0.844 0.848 0.853 250260 0.853 0.857 0.861 0.866 0.870 0.875 0.879 0.883 0.888 0.892 0.897 260270 0.897 0.901 0.906 0.910 0.915 0.919 0.923 0.928 0.932 0.937 0.941 270280 0.941 0.946 0.950 0.955 0.959 0.964 0.968 0.973 0.977 0.982 0.986 280290 0.986 0.991 0.995 1.000 1.005 1.009 1.014 1.018 1.023 1.027 1.032 290

300 1.032 1.036 1.041 1.046 1.050 1.055 1.059 1.064 1.069 1.073 1.078 300310 1.078 1.082 1.087 1.092 1.096 1.101 1.105 1.110 1.115 1.119 1.124 310320 1.124 1.129 1.133 1.138 1.143 1.147 1.152 1.157 1.161 1.166 1.171 320330 1.171 1.175 1.180 1.185 1.190 1.194 1.199 1.204 1.208 1.213 1.218 330340 1.218 1.223 1.227 1.232 1.237 1.242 1.246 1.251 1.256 1.261 1.265 340

350 1.265 1.270 1.275 1.280 1.284 1.289 1.294 1.299 1.304 1.308 1.313 350360 1.313 1.318 1.323 1.328 1.332 1.337 1.342 1.347 1.352 1.356 1.361 360370 1.361 1.366 1.371 1.376 1.381 1.386 1.390 1.395 1.400 1.405 1.410 370380 1.410 1.415 1.420 1.425 1.429 1.434 1.439 1.444 1.449 1.454 1.459 380390 1.459 1.464 1.469 1.473 1.478 1.483 1.488 1.493 1.498 1.503 1.508 390

400 1.508 1.513 1.518 1.523 1.528 1.533 1.538 1.543 1.548 1.553 1.558 400410 1.558 1.563 1.568 1.572 1.577 1.582 1.587 1.592 1.597 1.602 1.607 410420 1.607 1.612 1.617 1.622 1.627 1.632 1.638 1.643 1.648 1.653 1.658 420430 1.658 1.663 1.668 1.673 1.678 1.683 1.688 1.693 1.698 1.703 1.708 430440 1.708 1.713 1.718 1.723 1.728 1.733 1.739 1.744 1.749 1.754 1.759 440

450 1.759 1.764 1.769 1.774 1.779 1.784 1.790 1.795 1.800 1.805 1.810 450460 1.810 1.815 1.820 1.825 1.831 1.836 1.841 1.846 1.851 1.856 1.861 460470 1.861 1.867 1.872 1.877 1.882 1.887 1.892 1.898 1.903 1.908 1.913 470480 1.913 1.918 1.923 1.929 1.934 1.939 1.944 1.949 1.955 1.960 1.965 480490 1.965 1.970 1.975 1.981 1.986 1.991 1.996 2.002 2.007 2.012 2.017 490

500 2.017 2.022 2.028 2.033 2.038 2.043 2.049 2.054 2.059 2.064 2.070 500510 2.070 2.075 2.080 2.085 2.091 2.096 2.101 2.107 2.112 2.117 2.122 510520 2.122 2.128 2.133 2.138 2.144 2.149 2.154 2.159 2.165 2.170 2.175 520530 2.175 2.181 2.186 2.191 2.197 2.202 2.207 2.213 2.218 2.223 2.229 530540 2.229 2.234 2.239 2.245 2.250 2.255 2.261 2.266 2.271 2.277 2.282 540

550 2.282 2.287 2.293 2.298 2.304 2.309 2.314 2.320 2.325 2.330 2.336 550560 2.336 2.341 2.347 2.352 2.357 2.363 2.368 2.374 2.379 2.384 2.390 560570 2.390 2.395 2.401 2.406 2.411 2.417 2.422 2.428 2.433 2.438 2.444 570580 2.444 2.449 2.455 2.460 2.466 2.471 2.477 2.482 2.487 2.493 2.498 580590 2.498 2.504 2.509 2.515 2.520 2.526 2.531 2.537 2.542 2.547 2.553 590

600 2.553 2.558 2.564 2.569 2.575 2.580 2.586 2.591 2.597 2.602 2.608 600610 2.608 2.613 2.619 2.624 2.630 2.635 2.641 2.646 2.652 2.657 2.663 610620 2.663 2.668 2.674 2.679 2.685 2.690 2.696 2.701 2.707 2.713 2.718 620630 2.718 2.724 2.729 2.735 2.740 2.746 2.751 2.757 2.762 2.768 2.773 630640 2.773 2.779 2.785 2.790 2.796 2.801 2.807 2.812 2.818 2.824 2.829 640

650 2.829 2.835 2.840 2.846 2.851 2.857 2.863 2.868 2.874 2.879 2.885 650660 2.885 2.891 2.896 2.902 2.907 2.913 2.919 2.924 2.930 2.935 2.941 660670 2.941 2.947 2.952 2.958 2.964 2.969 2.975 2.980 2.986 2.992 2.997 670680 2.997 3.003 3.009 3.014 3.020 3.026 3.031 3.037 3.042 3.048 3.054 680690 3.054 3.059 3.065 3.071 3.076 3.082 3.088 3.093 3.099 3.105 3.110 690

700 3.110 3.116 3.122 3.127 3.133 3.139 3.144 3.150 3.156 3.161 3.167 700710 3.167 3.173 3.179 3.184 3.190 3.196 3.201 3.207 3.213 3.218 3.224 710720 3.224 3.230 3.236 3.241 3.247 3.253 3.258 3.264 3.270 3.276 3.281 720730 3.281 3.287 3.293 3.298 3.304 3.310 3.316 3.321 3.327 3.333 3.339 730740 3.339 3.344 3.350 3.356 3.362 3.367 3.373 3.379 3.385 3.390 3.396 740

750 3.396 3.402 3.408 3.413 3.419 3.425 3.431 3.437 3.442 3.448 3.454 750760 3.454 3.460 3.465 3.471 3.477 3.483 3.489 3.494 3.500 3.506 3.512 760770 3.512 3.517 3.523 3.529 3.535 3.541 3.546 3.552 3.558 3.564 3.570 770780 3.570 3.576 3.581 3.587 3.593 3.599 3.605 3.610 3.616 3.622 3.628 780790 3.628 3.634 3.640 3.645 3.651 3.657 3.663 3.669 3.675 3.680 3.686 790

800 3.686 3.692 3.698 3.704 3.710 3.716 3.721 3.727 3.733 3.739 3.745 800810 3.745 3.751 3.757 3.762 3.768 3.774 3.780 3.786 3.792 3.798 3.803 810820 3.803 3.809 3.815 3.821 3.827 3.833 3.839 3.845 3.851 3.856 3.862 820830 3.862 3.868 3.874 3.880 3.886 3.892 3.898 3.904 3.909 3.915 3.921 830840 3.921 3.927 3.933 3.939 3.945 3.951 3.957 3.963 3.969 3.975 3.980 840

850 3.980 3.986 3.992 3.998 4.004 4.010 4.016 4.022 4.028 4.034 4.040 850860 4.040 4.046 4.052 4.058 4.064 4.069 4.075 4.081 4.087 4.093 4.099 860870 4.099 4.105 4.111 4.117 4.123 4.129 4.135 4.141 4.147 4.153 4.159 870880 4.159 4.165 4.171 4.177 4.183 4.189 4.195 4.201 4.207 4.213 4.219 880890 4.219 4.225 4.231 4.237 4.243 4.249 4.255 4.261 4.267 4.273 4.279 890

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 2642°F0 to 1450°CExtension Grade32 to 300°F0 to 150°CLIMITS OF ERROR(whichever is greater)Standard: 1.5°C or 0.25%Special: 0.6°C or 0.1%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High TemperatureTEMPERATURE IN DEGREES °F REFERENCE JUNCTION AT 32°F RR

°F -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

ThermocoupleGrade


Platinum

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-229


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

900 4.279 4.285 4.291 4.297 4.303 4.309 4.315 4.321 4.327 4.333 4.339 900910 4.339 4.345 4.351 4.357 4.363 4.369 4.375 4.381 4.387 4.393 4.399 910920 4.399 4.405 4.411 4.417 4.423 4.429 4.435 4.441 4.447 4.453 4.459 920930 4.459 4.465 4.471 4.477 4.483 4.489 4.495 4.502 4.508 4.514 4.520 930940 4.520 4.526 4.532 4.538 4.544 4.550 4.556 4.562 4.568 4.574 4.580 940

950 4.580 4.586 4.593 4.599 4.605 4.611 4.617 4.623 4.629 4.635 4.641 950960 4.641 4.647 4.653 4.659 4.666 4.672 4.678 4.684 4.690 4.696 4.702 960970 4.702 4.708 4.714 4.720 4.727 4.733 4.739 4.745 4.751 4.757 4.763 970980 4.763 4.769 4.775 4.782 4.788 4.794 4.800 4.806 4.812 4.818 4.824 980990 4.824 4.831 4.837 4.843 4.849 4.855 4.861 4.867 4.874 4.880 4.886 990

1000 4.886 4.892 4.898 4.904 4.910 4.917 4.923 4.929 4.935 4.941 4.947 10001010 4.947 4.954 4.960 4.966 4.972 4.978 4.984 4.991 4.997 5.003 5.009 10101020 5.009 5.015 5.021 5.028 5.034 5.040 5.046 5.052 5.059 5.065 5.071 10201030 5.071 5.077 5.083 5.090 5.096 5.102 5.108 5.114 5.121 5.127 5.133 10301040 5.133 5.139 5.145 5.152 5.158 5.164 5.170 5.176 5.183 5.189 5.195 1040

1050 5.195 5.201 5.207 5.214 5.220 5.226 5.232 5.239 5.245 5.251 5.257 10501060 5.257 5.264 5.270 5.276 5.282 5.289 5.295 5.301 5.307 5.313 5.320 10601070 5.320 5.326 5.332 5.338 5.345 5.351 5.357 5.364 5.370 5.376 5.382 10701080 5.382 5.389 5.395 5.401 5.407 5.414 5.420 5.426 5.432 5.439 5.445 10801090 5.445 5.451 5.458 5.464 5.470 5.476 5.483 5.489 5.495 5.502 5.508 1090

1100 5.508 5.514 5.520 5.527 5.533 5.539 5.546 5.552 5.558 5.565 5.571 11001110 5.571 5.577 5.583 5.590 5.596 5.602 5.609 5.615 5.621 5.628 5.634 11101120 5.634 5.640 5.647 5.653 5.659 5.666 5.672 5.678 5.685 5.691 5.697 11201130 5.697 5.704 5.710 5.716 5.723 5.729 5.735 5.742 5.748 5.754 5.761 11301140 5.761 5.767 5.773 5.780 5.786 5.792 5.799 5.805 5.812 5.818 5.824 1140

1150 5.824 5.831 5.837 5.843 5.850 5.856 5.862 5.869 5.875 5.882 5.888 11501160 5.888 5.894 5.901 5.907 5.913 5.920 5.926 5.933 5.939 5.945 5.952 11601170 5.952 5.958 5.965 5.971 5.977 5.984 5.990 5.997 6.003 6.009 6.016 11701180 6.016 6.022 6.029 6.035 6.041 6.048 6.054 6.061 6.067 6.074 6.080 11801190 6.080 6.086 6.093 6.099 6.106 6.112 6.119 6.125 6.131 6.138 6.144 1190

1200 6.144 6.151 6.157 6.164 6.170 6.176 6.183 6.189 6.196 6.202 6.209 12001210 6.209 6.215 6.222 6.228 6.235 6.241 6.247 6.254 6.260 6.267 6.273 12101220 6.273 6.280 6.286 6.293 6.299 6.306 6.312 6.319 6.325 6.332 6.338 12201230 6.338 6.345 6.351 6.358 6.364 6.370 6.377 6.383 6.390 6.396 6.403 12301240 6.403 6.409 6.416 6.422 6.429 6.435 6.442 6.448 6.455 6.461 6.468 1240

1250 6.468 6.474 6.481 6.488 6.494 6.501 6.507 6.514 6.520 6.527 6.533 12501260 6.533 6.540 6.546 6.553 6.559 6.566 6.572 6.579 6.585 6.592 6.598 12601270 6.598 6.605 6.612 6.618 6.625 6.631 6.638 6.644 6.651 6.657 6.664 12701280 6.664 6.671 6.677 6.684 6.690 6.697 6.703 6.710 6.716 6.723 6.730 12801290 6.730 6.736 6.743 6.749 6.756 6.762 6.769 6.776 6.782 6.789 6.795 1290

1300 6.795 6.802 6.809 6.815 6.822 6.828 6.835 6.841 6.848 6.855 6.861 13001310 6.861 6.868 6.874 6.881 6.888 6.894 6.901 6.907 6.914 6.921 6.927 13101320 6.927 6.934 6.941 6.947 6.954 6.960 6.967 6.974 6.980 6.987 6.994 13201330 6.994 7.000 7.007 7.013 7.020 7.027 7.033 7.040 7.047 7.053 7.060 13301340 7.060 7.067 7.073 7.080 7.086 7.093 7.100 7.106 7.113 7.120 7.126 1340

1350 7.126 7.133 7.140 7.146 7.153 7.160 7.166 7.173 7.180 7.186 7.193 13501360 7.193 7.200 7.206 7.213 7.220 7.226 7.233 7.240 7.247 7.253 7.260 13601370 7.260 7.267 7.273 7.280 7.287 7.293 7.300 7.307 7.313 7.320 7.327 13701380 7.327 7.334 7.340 7.347 7.354 7.360 7.367 7.374 7.381 7.387 7.394 13801390 7.394 7.401 7.407 7.414 7.421 7.428 7.434 7.441 7.448 7.454 7.461 1390

1400 7.461 7.468 7.475 7.481 7.488 7.495 7.502 7.508 7.515 7.522 7.529 14001410 7.529 7.535 7.542 7.549 7.556 7.562 7.569 7.576 7.583 7.589 7.596 14101420 7.596 7.603 7.610 7.616 7.623 7.630 7.637 7.644 7.650 7.657 7.664 14201430 7.664 7.671 7.677 7.684 7.691 7.698 7.705 7.711 7.718 7.725 7.732 14301440 7.732 7.739 7.745 7.752 7.759 7.766 7.772 7.779 7.786 7.793 7.800 1440

1450 7.800 7.807 7.813 7.820 7.827 7.834 7.841 7.847 7.854 7.861 7.868 14501460 7.868 7.875 7.882 7.888 7.895 7.902 7.909 7.916 7.922 7.929 7.936 14601470 7.936 7.943 7.950 7.957 7.964 7.970 7.977 7.984 7.991 7.998 8.005 14701480 8.005 8.011 8.018 8.025 8.032 8.039 8.046 8.053 8.059 8.066 8.073 14801490 8.073 8.080 8.087 8.094 8.101 8.108 8.114 8.121 8.128 8.135 8.142 1490

1500 8.142 8.149 8.156 8.163 8.169 8.176 8.183 8.190 8.197 8.204 8.211 15001510 8.211 8.218 8.225 8.232 8.238 8.245 8.252 8.259 8.266 8.273 8.280 15101520 8.280 8.287 8.294 8.301 8.308 8.314 8.321 8.328 8.335 8.342 8.349 15201530 8.349 8.356 8.363 8.370 8.377 8.384 8.391 8.398 8.405 8.411 8.418 15301540 8.418 8.425 8.432 8.439 8.446 8.453 8.460 8.467 8.474 8.481 8.488 1540

1550 8.488 8.495 8.502 8.509 8.516 8.523 8.530 8.537 8.544 8.551 8.557 15501560 8.557 8.564 8.571 8.578 8.585 8.592 8.599 8.606 8.613 8.620 8.627 15601570 8.627 8.634 8.641 8.648 8.655 8.662 8.669 8.676 8.683 8.690 8.697 15701580 8.697 8.704 8.711 8.718 8.725 8.732 8.739 8.746 8.753 8.760 8.767 15801590 8.767 8.774 8.781 8.788 8.795 8.802 8.809 8.816 8.823 8.830 8.837 1590

1600 8.837 8.844 8.852 8.859 8.866 8.873 8.880 8.887 8.894 8.901 8.908 16001610 8.908 8.915 8.922 8.929 8.936 8.943 8.950 8.957 8.964 8.971 8.978 16101620 8.978 8.985 8.992 8.999 9.007 9.014 9.021 9.028 9.035 9.042 9.049 16201630 9.049 9.056 9.063 9.070 9.077 9.084 9.091 9.098 9.106 9.113 9.120 16301640 9.120 9.127 9.134 9.141 9.148 9.155 9.162 9.169 9.176 9.184 9.191 1640

1650 9.191 9.198 9.205 9.212 9.219 9.226 9.233 9.240 9.248 9.255 9.262 16501660 9.262 9.269 9.276 9.283 9.290 9.297 9.304 9.312 9.319 9.326 9.333 16601670 9.333 9.340 9.347 9.354 9.361 9.369 9.376 9.383 9.390 9.397 9.404 16701680 9.404 9.411 9.419 9.426 9.433 9.440 9.447 9.454 9.461 9.469 9.476 16801690 9.476 9.483 9.490 9.497 9.504 9.512 9.519 9.526 9.533 9.540 9.547 1690

1700 9.547 9.555 9.562 9.569 9.576 9.583 9.590 9.598 9.605 9.612 9.619 17001710 9.619 9.626 9.634 9.641 9.648 9.655 9.662 9.670 9.677 9.684 9.691 17101720 9.691 9.698 9.706 9.713 9.720 9.727 9.734 9.742 9.749 9.756 9.763 17201730 9.763 9.770 9.778 9.785 9.792 9.799 9.806 9.814 9.821 9.828 9.835 17301740 9.835 9.843 9.850 9.857 9.864 9.872 9.879 9.886 9.893 9.900 9.908 1740

1750 9.908 9.915 9.922 9.929 9.937 9.944 9.951 9.958 9.966 9.973 9.980 17501760 9.980 9.987 9.995 10.002 10.009 10.016 10.024 10.031 10.038 10.046 10.053 17601770 10.053 10.060 10.067 10.075 10.082 10.089 10.096 10.104 10.111 10.118 10.126 17701780 10.126 10.133 10.140 10.147 10.155 10.162 10.169 10.177 10.184 10.191 10.198 17801790 10.198 10.206 10.213 10.220 10.228 10.235 10.242 10.250 10.257 10.264 10.271 1790

1800 10.271 10.279 10.286 10.293 10.301 10.308 10.315 10.323 10.330 10.337 10.345 18001810 10.345 10.352 10.359 10.367 10.374 10.381 10.389 10.396 10.403 10.411 10.418 18101820 10.418 10.425 10.433 10.440 10.447 10.455 10.462 10.469 10.477 10.484 10.491 18201830 10.491 10.499 10.506 10.513 10.521 10.528 10.535 10.543 10.550 10.557 10.565 18301840 10.565 10.572 10.580 10.587 10.594 10.602 10.609 10.616 10.624 10.631 10.638 1840

1850 10.638 10.646 10.653 10.661 10.668 10.675 10.683 10.690 10.698 10.705 10.712 18501860 10.712 10.720 10.727 10.734 10.742 10.749 10.757 10.764 10.771 10.779 10.786 18601870 10.786 10.794 10.801 10.808 10.816 10.823 10.831 10.838 10.845 10.853 10.860 18701880 10.860 10.868 10.875 10.883 10.890 10.897 10.905 10.912 10.920 10.927 10.934 18801890 10.934 10.942 10.949 10.957 10.964 10.972 10.979 10.986 10.994 11.001 11.009 1890

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 2642°F0 to 1450°CExtension Grade32 to 300°F0 to 150°CLIMITS OF ERROR(whichever is greater)Standard: 1.5°C or 0.25%Special: 0.6°C or 0.1%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High TemperatureTEMPERATURE IN DEGREES °F REFERENCE JUNCTION AT 32°FRR

ThermocoupleGrade


Platinum

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-230

Z


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

1900 11.009 11.016 11.024 11.031 11.039 11.046 11.053 11.061 11.068 11.076 11.083 19001910 11.083 11.091 11.098 11.106 11.113 11.121 11.128 11.135 11.143 11.150 11.158 19101920 11.158 11.165 11.173 11.180 11.188 11.195 11.203 11.210 11.218 11.225 11.233 19201930 11.233 11.240 11.247 11.255 11.262 11.270 11.277 11.285 11.292 11.300 11.307 19301940 11.307 11.315 11.322 11.330 11.337 11.345 11.352 11.360 11.367 11.375 11.382 1940

1950 11.382 11.390 11.397 11.405 11.412 11.420 11.427 11.435 11.442 11.450 11.457 19501960 11.457 11.465 11.472 11.480 11.487 11.495 11.502 11.510 11.518 11.525 11.533 19601970 11.533 11.540 11.548 11.555 11.563 11.570 11.578 11.585 11.593 11.600 11.608 19701980 11.608 11.615 11.623 11.631 11.638 11.646 11.653 11.661 11.668 11.676 11.683 19801990 11.683 11.691 11.698 11.706 11.714 11.721 11.729 11.736 11.744 11.751 11.759 1990

2000 11.759 11.766 11.774 11.782 11.789 11.797 11.804 11.812 11.819 11.827 11.834 20002010 11.834 11.842 11.850 11.857 11.865 11.872 11.880 11.888 11.895 11.903 11.910 20102020 11.910 11.918 11.925 11.933 11.941 11.948 11.956 11.963 11.971 11.979 11.986 20202030 11.986 11.994 12.001 12.009 12.016 12.024 12.032 12.039 12.047 12.054 12.062 20302040 12.062 12.070 12.077 12.085 12.092 12.100 12.108 12.115 12.123 12.131 12.138 2040

2050 12.138 12.146 12.153 12.161 12.169 12.176 12.184 12.191 12.199 12.207 12.214 20502060 12.214 12.222 12.230 12.237 12.245 12.252 12.260 12.268 12.275 12.283 12.291 20602070 12.291 12.298 12.306 12.313 12.321 12.329 12.336 12.344 12.352 12.359 12.367 20702080 12.367 12.375 12.382 12.390 12.397 12.405 12.413 12.420 12.428 12.436 12.443 20802090 12.443 12.451 12.459 12.466 12.474 12.482 12.489 12.497 12.505 12.512 12.520 2090

2100 12.520 12.528 12.535 12.543 12.551 12.558 12.566 12.574 12.581 12.589 12.597 21002110 12.597 12.604 12.612 12.620 12.627 12.635 12.643 12.650 12.658 12.666 12.673 21102120 12.673 12.681 12.689 12.696 12.704 12.712 12.719 12.727 12.735 12.742 12.750 21202130 12.750 12.758 12.765 12.773 12.781 12.788 12.796 12.804 12.812 12.819 12.827 21302140 12.827 12.835 12.842 12.850 12.858 12.865 12.873 12.881 12.889 12.896 12.904 2140

2150 12.904 12.912 12.919 12.927 12.935 12.942 12.950 12.958 12.966 12.973 12.981 21502160 12.981 12.989 12.996 13.004 13.012 13.019 13.027 13.035 13.043 13.050 13.058 21602170 13.058 13.066 13.073 13.081 13.089 13.097 13.104 13.112 13.120 13.128 13.135 21702180 13.135 13.143 13.151 13.158 13.166 13.174 13.182 13.189 13.197 13.205 13.213 21802190 13.213 13.220 13.228 13.236 13.243 13.251 13.259 13.267 13.274 13.282 13.290 2190

2200 13.290 13.298 13.305 13.313 13.321 13.329 13.336 13.344 13.352 13.359 13.367 22002210 13.367 13.375 13.383 13.390 13.398 13.406 13.414 13.421 13.429 13.437 13.445 22102220 13.445 13.452 13.460 13.468 13.476 13.483 13.491 13.499 13.507 13.514 13.522 22202230 13.522 13.530 13.538 13.545 13.553 13.561 13.569 13.577 13.584 13.592 13.600 22302240 13.600 13.608 13.615 13.623 13.631 13.639 13.646 13.654 13.662 13.670 13.677 2240

2250 13.677 13.685 13.693 13.701 13.709 13.716 13.724 13.732 13.740 13.747 13.755 22502260 13.755 13.763 13.771 13.778 13.786 13.794 13.802 13.810 13.817 13.825 13.833 22602270 13.833 13.841 13.848 13.856 13.864 13.872 13.880 13.887 13.895 13.903 13.911 22702280 13.911 13.919 13.926 13.934 13.942 13.950 13.957 13.965 13.973 13.981 13.989 22802290 13.989 13.996 14.004 14.012 14.020 14.028 14.035 14.043 14.051 14.059 14.066 2290

2300 14.066 14.074 14.082 14.090 14.098 14.105 14.113 14.121 14.129 14.137 14.144 23002310 14.144 14.152 14.160 14.168 14.176 14.183 14.191 14.199 14.207 14.215 14.222 23102320 14.222 14.230 14.238 14.246 14.254 14.261 14.269 14.277 14.285 14.293 14.300 23202330 14.300 14.308 14.316 14.324 14.332 14.340 14.347 14.355 14.363 14.371 14.379 23302340 14.379 14.386 14.394 14.402 14.410 14.418 14.425 14.433 14.441 14.449 14.457 2340

2350 14.457 14.465 14.472 14.480 14.488 14.496 14.504 14.511 14.519 14.527 14.535 23502360 14.535 14.543 14.551 14.558 14.566 14.574 14.582 14.590 14.597 14.605 14.613 23602370 14.613 14.621 14.629 14.637 14.644 14.652 14.660 14.668 14.676 14.683 14.691 23702380 14.691 14.699 14.707 14.715 14.723 14.730 14.738 14.746 14.754 14.762 14.770 23802390 14.770 14.777 14.785 14.793 14.801 14.809 14.817 14.824 14.832 14.840 14.848 2390

2400 14.848 14.856 14.864 14.871 14.879 14.887 14.895 14.903 14.911 14.918 14.926 24002410 14.926 14.934 14.942 14.950 14.958 14.965 14.973 14.981 14.989 14.997 15.005 24102420 15.005 15.012 15.020 15.028 15.036 15.044 15.052 15.059 15.067 15.075 15.083 24202430 15.083 15.091 15.099 15.106 15.114 15.122 15.130 15.138 15.146 15.153 15.161 24302440 15.161 15.169 15.177 15.185 15.193 15.200 15.208 15.216 15.224 15.232 15.240 2440

2450 15.240 15.248 15.255 15.263 15.271 15.279 15.287 15.295 15.302 15.310 15.318 24502460 15.318 15.326 15.334 15.342 15.349 15.357 15.365 15.373 15.381 15.389 15.397 24602470 15.397 15.404 15.412 15.420 15.428 15.436 15.444 15.451 15.459 15.467 15.475 24702480 15.475 15.483 15.491 15.499 15.506 15.514 15.522 15.530 15.538 15.546 15.553 24802490 15.553 15.561 15.569 15.577 15.585 15.593 15.601 15.608 15.616 15.624 15.632 2490

2500 15.632 15.640 15.648 15.655 15.663 15.671 15.679 15.687 15.695 15.703 15.710 25002510 15.710 15.718 15.726 15.734 15.742 15.750 15.758 15.765 15.773 15.781 15.789 25102520 15.789 15.797 15.805 15.812 15.820 15.828 15.836 15.844 15.852 15.860 15.867 25202530 15.867 15.875 15.883 15.891 15.899 15.907 15.915 15.922 15.930 15.938 15.946 25302540 15.946 15.954 15.962 15.969 15.977 15.985 15.993 16.001 16.009 16.017 16.024 2540

2550 16.024 16.032 16.040 16.048 16.056 16.064 16.071 16.079 16.087 16.095 16.103 25502560 16.103 16.111 16.119 16.126 16.134 16.142 16.150 16.158 16.166 16.174 16.181 25602570 16.181 16.189 16.197 16.205 16.213 16.221 16.228 16.236 16.244 16.252 16.260 25702580 16.260 16.268 16.276 16.283 16.291 16.299 16.307 16.315 16.323 16.330 16.338 25802590 16.338 16.346 16.354 16.362 16.370 16.378 16.385 16.393 16.401 16.409 16.417 2590

2600 16.417 16.425 16.432 16.440 16.448 16.456 16.464 16.472 16.480 16.487 16.495 26002610 16.495 16.503 16.511 16.519 16.527 16.534 16.542 16.550 16.558 16.566 16.574 26102620 16.574 16.582 16.589 16.597 16.605 16.613 16.621 16.629 16.636 16.644 16.652 26202630 16.652 16.660 16.668 16.676 16.683 16.691 16.699 16.707 16.715 16.723 16.731 26302640 16.731 16.738 16.746 16.754 16.762 16.770 16.778 16.785 16.793 16.801 16.809 2640

2650 16.809 16.817 16.825 16.832 16.840 16.848 16.856 16.864 16.872 16.879 16.887 26502660 16.887 16.895 16.903 16.911 16.919 16.926 16.934 16.942 16.950 16.958 16.966 26602670 16.966 16.973 16.981 16.989 16.997 17.005 17.013 17.020 17.028 17.036 17.044 26702680 17.044 17.052 17.060 17.067 17.075 17.083 17.091 17.099 17.107 17.114 17.122 26802690 17.122 17.130 17.138 17.146 17.154 17.161 17.169 17.177 17.185 17.193 17.200 2690

2700 17.200 17.208 17.216 17.224 17.232 17.240 17.247 17.255 17.263 17.271 17.279 27002710 17.279 17.286 17.294 17.302 17.310 17.318 17.326 17.333 17.341 17.349 17.357 27102720 17.357 17.365 17.373 17.380 17.388 17.396 17.404 17.412 17.419 17.427 17.435 27202730 17.435 17.443 17.451 17.458 17.466 17.474 17.482 17.490 17.498 17.505 17.513 27302740 17.513 17.521 17.529 17.537 17.544 17.552 17.560 17.568 17.576 17.583 17.591 2740

2750 17.591 17.599 17.607 17.615 17.622 17.630 17.638 17.646 17.654 17.661 17.669 27502760 17.669 17.677 17.685 17.693 17.700 17.708 17.716 17.724 17.732 17.739 17.747 27602770 17.747 17.755 17.763 17.771 17.778 17.786 17.794 17.802 17.810 17.817 17.825 27702780 17.825 17.833 17.841 17.849 17.856 17.864 17.872 17.880 17.888 17.895 17.903 27802790 17.903 17.911 17.919 17.926 17.934 17.942 17.950 17.958 17.965 17.973 17.981 2790

2800 17.981 17.989 17.997 18.004 18.012 18.020 18.028 18.035 18.043 18.051 18.059 28002810 18.059 18.067 18.074 18.082 18.090 18.098 18.105 18.113 18.121 18.129 18.137 28102820 18.137 18.144 18.152 18.160 18.168 18.175 18.183 18.191 18.199 18.206 18.214 28202830 18.214 18.222 18.230 18.238 18.245 18.253 18.261 18.269 18.276 18.284 18.292 28302840 18.292 18.300 18.307 18.315 18.323 18.331 18.338 18.346 18.354 18.362 18.369 2840

2850 18.369 18.377 18.385 18.393 18.400 18.408 18.416 18.424 18.431 18.439 18.447 28502860 18.447 18.455 18.462 18.470 18.478 18.486 18.493 18.501 18.509 18.517 18.524 28602870 18.524 18.532 18.540 18.548 18.555 18.563 18.571 18.579 18.586 18.594 18.602 28702880 18.602 18.610 18.617 18.625 18.633 18.640 18.648 18.656 18.664 18.671 18.679 28802890 18.679 18.687 18.695 18.702 18.710 18.718 18.725 18.733 18.741 18.749 18.756 2890

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 2642°F0 to 1450°CExtension Grade32 to 300°F0 to 150°CLIMITS OF ERROR(whichever is greater)Standard: 1.5°C or 0.25%Special: 0.6°C or 0.1%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High TemperatureTEMPERATURE IN DEGREES °F REFERENCE JUNCTION AT 32°F RR

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

ThermocoupleGrade


Platinum

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-231


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

2900 18.756 18.764 18.772 18.779 18.787 18.795 18.803 18.810 18.818 18.826 18.834 29002910 18.834 18.841 18.849 18.857 18.864 18.872 18.880 18.887 18.895 18.903 18.911 29102920 18.911 18.918 18.926 18.934 18.941 18.949 18.957 18.965 18.972 18.980 18.988 29202930 18.988 18.995 19.003 19.011 19.018 19.026 19.034 19.042 19.049 19.057 19.065 29302940 19.065 19.072 19.080 19.088 19.095 19.103 19.111 19.118 19.126 19.134 19.141 2940

2950 19.141 19.149 19.157 19.165 19.172 19.180 19.188 19.195 19.203 19.211 19.218 29502960 19.218 19.226 19.234 19.241 19.249 19.257 19.264 19.272 19.280 19.287 19.295 29602970 19.295 19.303 19.310 19.318 19.326 19.333 19.341 19.349 19.356 19.364 19.372 29702980 19.372 19.379 19.387 19.395 19.402 19.410 19.418 19.425 19.433 19.440 19.448 29802990 19.448 19.456 19.463 19.471 19.479 19.486 19.494 19.502 19.509 19.517 19.525 2990

3000 19.525 19.532 19.540 19.547 19.555 19.563 19.570 19.578 19.586 19.593 19.601 30003010 19.601 19.609 19.616 19.624 19.631 19.639 19.647 19.654 19.662 19.670 19.677 30103020 19.677 19.685 19.692 19.700 19.708 19.715 19.723 19.730 19.738 19.746 19.753 30203030 19.753 19.761 19.769 19.776 19.784 19.791 19.799 19.807 19.814 19.822 19.829 30303040 19.829 19.837 19.845 19.852 19.860 19.867 19.875 19.882 19.890 19.898 19.905 3040

3050 19.905 19.913 19.920 19.928 19.936 19.943 19.951 19.958 19.966 19.973 19.981 30503060 19.981 19.989 19.996 20.004 20.011 20.019 20.026 20.034 20.041 20.049 20.056 30603070 20.056 20.064 20.072 20.079 20.087 20.094 20.102 20.109 20.117 20.124 20.132 30703080 20.132 20.139 20.147 20.154 20.162 20.169 20.177 20.184 20.192 20.199 20.207 30803090 20.207 20.214 20.222 20.229 20.237 20.244 20.252 20.259 20.266 20.274 20.281 3090

3100 20.281 20.289 20.296 20.304 20.311 20.319 20.326 20.333 20.341 20.348 20.356 31003110 20.356 20.363 20.371 20.378 20.385 20.393 20.400 20.407 20.415 20.422 20.430 31103120 20.430 20.437 20.444 20.452 20.459 20.466 20.474 20.481 20.488 20.496 20.503 31203130 20.503 20.510 20.518 20.525 20.532 20.540 20.547 20.554 20.562 20.569 20.576 31303140 20.576 20.583 20.591 20.598 20.605 20.612 20.620 20.627 20.634 20.641 20.649 3140

3150 20.649 20.656 20.663 20.670 20.678 20.685 20.692 20.699 20.706 20.714 20.721 31503160 20.721 20.728 20.735 20.742 20.749 20.756 20.764 20.771 20.778 20.785 20.792 31603170 20.792 20.799 20.806 20.813 20.821 20.828 20.835 20.842 20.849 20.856 20.863 31703180 20.863 20.870 20.877 20.884 20.891 20.898 20.905 20.912 20.919 20.926 20.933 31803190 20.933 20.940 20.947 20.954 20.961 20.968 20.975 20.982 20.989 20.996 21.003 3190

3200 21.003 21.010 21.016 21.023 21.030 21.037 21.044 21.051 21.058 21.065 21.071 32003210 21.071 21.078 21.085 21.092 21.099 3210

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 2642°F0 to 1450°CExtension Grade32 to 300°F0 to 150°CLIMITS OF ERROR(whichever is greater)Standard: 1.5°C or 0.25%Special: 0.6°C or 0.1%COMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High TemperatureTEMPERATURE IN DEGREES °F REFERENCE JUNCTION AT 32°FRR

ThermocoupleGrade


Platinum

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-232

Z


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

30 0.000 0.000 0.000 0.000 -0.001 -0.001 -0.001 -0.001 -0.001 3040 -0.001 -0.001 -0.001 -0.001 -0.001 -0.001 -0.002 -0.002 -0.002 -0.002 -0.002 40

50 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 5060 -0.002 -0.002 -0.002 -0.003 -0.003 -0.003 -0.003 -0.003 -0.003 -0.003 -0.003 6070 -0.003 -0.003 -0.003 -0.003 -0.003 -0.003 -0.003 -0.002 -0.002 -0.002 -0.002 7080 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 -0.002 8090 -0.002 -0.002 -0.002 -0.002 -0.002 -0.001 -0.001 -0.001 -0.001 -0.001 -0.001 90

100 -0.001 -0.001 -0.001 -0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 100110 0.000 0.000 0.001 0.001 0.001 0.001 0.001 0.001 0.002 0.002 0.002 110120 0.002 0.002 0.002 0.002 0.003 0.003 0.003 0.003 0.003 0.004 0.004 120130 0.004 0.004 0.004 0.005 0.005 0.005 0.005 0.005 0.006 0.006 0.006 130140 0.006 0.006 0.007 0.007 0.007 0.007 0.008 0.008 0.008 0.009 0.009 140

150 0.009 0.009 0.009 0.010 0.010 0.010 0.011 0.011 0.011 0.012 0.012 150160 0.012 0.012 0.013 0.013 0.013 0.014 0.014 0.014 0.015 0.015 0.015 160170 0.015 0.016 0.016 0.016 0.017 0.017 0.017 0.018 0.018 0.019 0.019 170180 0.019 0.019 0.020 0.020 0.021 0.021 0.021 0.022 0.022 0.023 0.023 180190 0.023 0.023 0.024 0.024 0.025 0.025 0.026 0.026 0.027 0.027 0.027 190

200 0.027 0.028 0.028 0.029 0.029 0.030 0.030 0.031 0.031 0.032 0.032 200210 0.032 0.033 0.033 0.034 0.034 0.035 0.035 0.036 0.036 0.037 0.037 210220 0.037 0.038 0.038 0.039 0.039 0.040 0.041 0.041 0.042 0.042 0.043 220230 0.043 0.043 0.044 0.044 0.045 0.046 0.046 0.047 0.047 0.048 0.049 230240 0.049 0.049 0.050 0.050 0.051 0.052 0.052 0.053 0.053 0.054 0.055 240

250 0.055 0.055 0.056 0.057 0.057 0.058 0.059 0.059 0.060 0.060 0.061 250260 0.061 0.062 0.062 0.063 0.064 0.065 0.065 0.066 0.067 0.067 0.068 260270 0.068 0.069 0.069 0.070 0.071 0.072 0.072 0.073 0.074 0.074 0.075 270280 0.075 0.076 0.077 0.077 0.078 0.079 0.080 0.080 0.081 0.082 0.083 280290 0.083 0.083 0.084 0.085 0.086 0.086 0.087 0.088 0.089 0.090 0.090 290

300 0.090 0.091 0.092 0.093 0.094 0.094 0.095 0.096 0.097 0.098 0.099 300310 0.099 0.099 0.100 0.101 0.102 0.103 0.104 0.105 0.105 0.106 0.107 310320 0.107 0.108 0.109 0.110 0.111 0.112 0.112 0.113 0.114 0.115 0.116 320330 0.116 0.117 0.118 0.119 0.120 0.121 0.121 0.122 0.123 0.124 0.125 330340 0.125 0.126 0.127 0.128 0.129 0.130 0.131 0.132 0.133 0.134 0.135 340

350 0.135 0.136 0.137 0.138 0.139 0.140 0.141 0.142 0.143 0.144 0.145 350360 0.145 0.146 0.147 0.148 0.149 0.150 0.151 0.152 0.153 0.154 0.155 360370 0.155 0.156 0.157 0.158 0.159 0.160 0.161 0.162 0.163 0.164 0.165 370380 0.165 0.166 0.167 0.168 0.170 0.171 0.172 0.173 0.174 0.175 0.176 380390 0.176 0.177 0.178 0.179 0.180 0.182 0.183 0.184 0.185 0.186 0.187 390

400 0.187 0.188 0.190 0.191 0.192 0.193 0.194 0.195 0.196 0.198 0.199 400410 0.199 0.200 0.201 0.202 0.203 0.205 0.206 0.207 0.208 0.209 0.211 410420 0.211 0.212 0.213 0.214 0.215 0.217 0.218 0.219 0.220 0.222 0.223 420430 0.223 0.224 0.225 0.226 0.228 0.229 0.230 0.231 0.233 0.234 0.235 430440 0.235 0.236 0.238 0.239 0.240 0.242 0.243 0.244 0.245 0.247 0.248 440

450 0.248 0.249 0.251 0.252 0.253 0.255 0.256 0.257 0.259 0.260 0.261 450460 0.261 0.263 0.264 0.265 0.267 0.268 0.269 0.271 0.272 0.273 0.275 460470 0.275 0.276 0.277 0.279 0.280 0.282 0.283 0.284 0.286 0.287 0.288 470480 0.288 0.290 0.291 0.293 0.294 0.296 0.297 0.298 0.300 0.301 0.303 480490 0.303 0.304 0.305 0.307 0.308 0.310 0.311 0.313 0.314 0.316 0.317 490

500 0.317 0.319 0.320 0.321 0.323 0.324 0.326 0.327 0.329 0.330 0.332 500510 0.332 0.333 0.335 0.336 0.338 0.339 0.341 0.342 0.344 0.345 0.347 510520 0.347 0.348 0.350 0.352 0.353 0.355 0.356 0.358 0.359 0.361 0.362 520530 0.362 0.364 0.365 0.367 0.369 0.370 0.372 0.373 0.375 0.377 0.378 530540 0.378 0.380 0.381 0.383 0.384 0.386 0.388 0.389 0.391 0.393 0.394 540

550 0.394 0.396 0.397 0.399 0.401 0.402 0.404 0.406 0.407 0.409 0.411 550560 0.411 0.412 0.414 0.416 0.417 0.419 0.421 0.422 0.424 0.426 0.427 560570 0.427 0.429 0.431 0.432 0.434 0.436 0.437 0.439 0.441 0.443 0.444 570580 0.444 0.446 0.448 0.449 0.451 0.453 0.455 0.456 0.458 0.460 0.462 580590 0.462 0.463 0.465 0.467 0.469 0.470 0.472 0.474 0.476 0.478 0.479 590

600 0.479 0.481 0.483 0.485 0.486 0.488 0.490 0.492 0.494 0.495 0.497 600610 0.497 0.499 0.501 0.503 0.505 0.506 0.508 0.510 0.512 0.514 0.516 610620 0.516 0.517 0.519 0.521 0.523 0.525 0.527 0.529 0.530 0.532 0.534 620630 0.534 0.536 0.538 0.540 0.542 0.544 0.546 0.547 0.549 0.551 0.553 630640 0.553 0.555 0.557 0.559 0.561 0.563 0.565 0.567 0.569 0.570 0.572 640

650 0.572 0.574 0.576 0.578 0.580 0.582 0.584 0.586 0.588 0.590 0.592 650660 0.592 0.594 0.596 0.598 0.600 0.602 0.604 0.606 0.608 0.610 0.612 660670 0.612 0.614 0.616 0.618 0.620 0.622 0.624 0.626 0.628 0.630 0.632 670680 0.632 0.634 0.636 0.638 0.640 0.642 0.644 0.646 0.648 0.650 0.653 680690 0.653 0.655 0.657 0.659 0.661 0.663 0.665 0.667 0.669 0.671 0.673 690

700 0.673 0.675 0.678 0.680 0.682 0.684 0.686 0.688 0.690 0.692 0.694 700710 0.694 0.697 0.699 0.701 0.703 0.705 0.707 0.709 0.712 0.714 0.716 710720 0.716 0.718 0.720 0.722 0.725 0.727 0.729 0.731 0.733 0.735 0.738 720730 0.738 0.740 0.742 0.744 0.746 0.749 0.751 0.753 0.755 0.757 0.760 730740 0.760 0.762 0.764 0.766 0.769 0.771 0.773 0.775 0.778 0.780 0.782 740

750 0.782 0.784 0.787 0.789 0.791 0.793 0.796 0.798 0.800 0.802 0.805 750760 0.805 0.807 0.809 0.812 0.814 0.816 0.818 0.821 0.823 0.825 0.828 760770 0.828 0.830 0.832 0.835 0.837 0.839 0.842 0.844 0.846 0.849 0.851 770780 0.851 0.853 0.856 0.858 0.860 0.863 0.865 0.867 0.870 0.872 0.875 780790 0.875 0.877 0.879 0.882 0.884 0.886 0.889 0.891 0.894 0.896 0.898 790

800 0.898 0.901 0.903 0.906 0.908 0.910 0.913 0.915 0.918 0.920 0.923 800810 0.923 0.925 0.927 0.930 0.932 0.935 0.937 0.940 0.942 0.945 0.947 810820 0.947 0.950 0.952 0.955 0.957 0.959 0.962 0.964 0.967 0.969 0.972 820830 0.972 0.974 0.977 0.979 0.982 0.984 0.987 0.989 0.992 0.994 0.997 830840 0.997 1.000 1.002 1.005 1.007 1.010 1.012 1.015 1.017 1.020 1.022 840

850 1.022 1.025 1.027 1.030 1.033 1.035 1.038 1.040 1.043 1.045 1.048 850860 1.048 1.051 1.053 1.056 1.058 1.061 1.064 1.066 1.069 1.071 1.074 860870 1.074 1.077 1.079 1.082 1.085 1.087 1.090 1.092 1.095 1.098 1.100 870880 1.100 1.103 1.106 1.108 1.111 1.114 1.116 1.119 1.122 1.124 1.127 880890 1.127 1.130 1.132 1.135 1.138 1.140 1.143 1.146 1.148 1.151 1.154 890

900 1.154 1.157 1.159 1.162 1.165 1.167 1.170 1.173 1.176 1.178 1.181 900910 1.181 1.184 1.186 1.189 1.192 1.195 1.197 1.200 1.203 1.206 1.208 910920 1.208 1.211 1.214 1.217 1.220 1.222 1.225 1.228 1.231 1.233 1.236 920930 1.236 1.239 1.242 1.245 1.247 1.250 1.253 1.256 1.259 1.262 1.264 930940 1.264 1.267 1.270 1.273 1.276 1.278 1.281 1.284 1.287 1.290 1.293 940

950 1.293 1.296 1.298 1.301 1.304 1.307 1.310 1.313 1.316 1.318 1.321 950960 1.321 1.324 1.327 1.330 1.333 1.336 1.339 1.342 1.344 1.347 1.350 960970 1.350 1.353 1.356 1.359 1.362 1.365 1.368 1.371 1.374 1.377 1.379 970980 1.379 1.382 1.385 1.388 1.391 1.394 1.397 1.400 1.403 1.406 1.409 980990 1.409 1.412 1.415 1.418 1.421 1.424 1.427 1.430 1.433 1.436 1.439 990

1000 1.439 1.442 1.445 1.448 1.451 1.454 1.457 1.460 1.463 1.466 1.469 10001010 1.469 1.472 1.475 1.478 1.481 1.484 1.487 1.490 1.493 1.496 1.499 10101020 1.499 1.502 1.505 1.508 1.511 1.515 1.518 1.521 1.524 1.527 1.530 10201030 1.530 1.533 1.536 1.539 1.542 1.545 1.548 1.552 1.555 1.558 1.561 10301040 1.561 1.564 1.567 1.570 1.573 1.576 1.580 1.583 1.586 1.589 1.592 1040

1050 1.592 1.595 1.598 1.601 1.605 1.608 1.611 1.614 1.617 1.620 1.624 10501060 1.624 1.627 1.630 1.633 1.636 1.639 1.643 1.646 1.649 1.652 1.655 10601070 1.655 1.659 1.662 1.665 1.668 1.671 1.675 1.678 1.681 1.684 1.687 10701080 1.687 1.691 1.694 1.697 1.700 1.704 1.707 1.710 1.713 1.716 1.720 10801090 1.720 1.723 1.726 1.729 1.733 1.736 1.739 1.743 1.746 1.749 1.752 1090

1100 1.752 1.756 1.759 1.762 1.765 1.769 1.772 1.775 1.779 1.782 1.785 11001110 1.785 1.789 1.792 1.795 1.798 1.802 1.805 1.808 1.812 1.815 1.818 11101120 1.818 1.822 1.825 1.828 1.832 1.835 1.838 1.842 1.845 1.849 1.852 11201130 1.852 1.855 1.859 1.862 1.865 1.869 1.872 1.875 1.879 1.882 1.886 11301140 1.886 1.889 1.892 1.896 1.899 1.903 1.906 1.909 1.913 1.916 1.920 1140

1150 1.920 1.923 1.926 1.930 1.933 1.937 1.940 1.944 1.947 1.950 1.954 11501160 1.954 1.957 1.961 1.964 1.968 1.971 1.975 1.978 1.981 1.985 1.988 11601170 1.988 1.992 1.995 1.999 2.002 2.006 2.009 2.013 2.016 2.020 2.023 11701180 2.023 2.027 2.030 2.034 2.037 2.041 2.044 2.048 2.051 2.055 2.058 11801190 2.058 2.062 2.065 2.069 2.072 2.076 2.079 2.083 2.086 2.090 2.094 1190

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 3092°F0 to 1700°CExtension Grade32 to 212°F0 to 100°CLIMITS OF ERROR(whichever is greater)Standard: 0.5°C over 800°CSpecial: NOT ESTABLISHEDCOMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High Temperature;Common Use in Glass IndustryTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°F BB

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

ThermocoupleGrade


Platinum-6% Rhodium

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-233


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

1200 2.094 2.097 2.101 2.104 2.108 2.111 2.115 2.118 2.122 2.126 2.129 12001210 2.129 2.133 2.136 2.140 2.143 2.147 2.151 2.154 2.158 2.161 2.165 12101220 2.165 2.169 2.172 2.176 2.179 2.183 2.187 2.190 2.194 2.197 2.201 12201230 2.201 2.205 2.208 2.212 2.216 2.219 2.223 2.226 2.230 2.234 2.237 12301240 2.237 2.241 2.245 2.248 2.252 2.256 2.259 2.263 2.267 2.270 2.274 1240

1250 2.274 2.278 2.281 2.285 2.289 2.292 2.296 2.300 2.303 2.307 2.311 12501260 2.311 2.315 2.318 2.322 2.326 2.329 2.333 2.337 2.341 2.344 2.348 12601270 2.348 2.352 2.355 2.359 2.363 2.367 2.370 2.374 2.378 2.382 2.385 12701280 2.385 2.389 2.393 2.397 2.400 2.404 2.408 2.412 2.416 2.419 2.423 12801290 2.423 2.427 2.431 2.434 2.438 2.442 2.446 2.450 2.453 2.457 2.461 1290

1300 2.461 2.465 2.469 2.472 2.476 2.480 2.484 2.488 2.492 2.495 2.499 13001310 2.499 2.503 2.507 2.511 2.515 2.518 2.522 2.526 2.530 2.534 2.538 13101320 2.538 2.541 2.545 2.549 2.553 2.557 2.561 2.565 2.569 2.572 2.576 13201330 2.576 2.580 2.584 2.588 2.592 2.596 2.600 2.604 2.607 2.611 2.615 13301340 2.615 2.619 2.623 2.627 2.631 2.635 2.639 2.643 2.647 2.651 2.654 1340

1350 2.654 2.658 2.662 2.666 2.670 2.674 2.678 2.682 2.686 2.690 2.694 13501360 2.694 2.698 2.702 2.706 2.710 2.714 2.718 2.722 2.726 2.730 2.734 13601370 2.734 2.738 2.742 2.746 2.750 2.754 2.758 2.762 2.766 2.770 2.774 13701380 2.774 2.778 2.782 2.786 2.790 2.794 2.798 2.802 2.806 2.810 2.814 13801390 2.814 2.818 2.822 2.826 2.830 2.834 2.838 2.842 2.846 2.850 2.854 1390

1400 2.854 2.859 2.863 2.867 2.871 2.875 2.879 2.883 2.887 2.891 2.895 14001410 2.895 2.899 2.903 2.908 2.912 2.916 2.920 2.924 2.928 2.932 2.936 14101420 2.936 2.940 2.944 2.949 2.953 2.957 2.961 2.965 2.969 2.973 2.978 14201430 2.978 2.982 2.986 2.990 2.994 2.998 3.002 3.007 3.011 3.015 3.019 14301440 3.019 3.023 3.027 3.032 3.036 3.040 3.044 3.048 3.052 3.057 3.061 1440

1450 3.061 3.065 3.069 3.073 3.078 3.082 3.086 3.090 3.094 3.099 3.103 14501460 3.103 3.107 3.111 3.116 3.120 3.124 3.128 3.132 3.137 3.141 3.145 14601470 3.145 3.149 3.154 3.158 3.162 3.166 3.171 3.175 3.179 3.183 3.188 14701480 3.188 3.192 3.196 3.200 3.205 3.209 3.213 3.218 3.222 3.226 3.230 14801490 3.230 3.235 3.239 3.243 3.248 3.252 3.256 3.261 3.265 3.269 3.273 1490

1500 3.273 3.278 3.282 3.286 3.291 3.295 3.299 3.304 3.308 3.312 3.317 15001510 3.317 3.321 3.325 3.330 3.334 3.338 3.343 3.347 3.352 3.356 3.360 15101520 3.360 3.365 3.369 3.373 3.378 3.382 3.386 3.391 3.395 3.400 3.404 15201530 3.404 3.408 3.413 3.417 3.422 3.426 3.430 3.435 3.439 3.444 3.448 15301540 3.448 3.452 3.457 3.461 3.466 3.470 3.474 3.479 3.483 3.488 3.492 1540

1550 3.492 3.497 3.501 3.506 3.510 3.514 3.519 3.523 3.528 3.532 3.537 15501560 3.537 3.541 3.546 3.550 3.555 3.559 3.563 3.568 3.572 3.577 3.581 15601570 3.581 3.586 3.590 3.595 3.599 3.604 3.608 3.613 3.617 3.622 3.626 15701580 3.626 3.631 3.635 3.640 3.644 3.649 3.653 3.658 3.662 3.667 3.672 15801590 3.672 3.676 3.681 3.685 3.690 3.694 3.699 3.703 3.708 3.712 3.717 1590

1600 3.717 3.722 3.726 3.731 3.735 3.740 3.744 3.749 3.753 3.758 3.763 16001610 3.763 3.767 3.772 3.776 3.781 3.786 3.790 3.795 3.799 3.804 3.809 16101620 3.809 3.813 3.818 3.822 3.827 3.832 3.836 3.841 3.845 3.850 3.855 16201630 3.855 3.859 3.864 3.869 3.873 3.878 3.882 3.887 3.892 3.896 3.901 16301640 3.901 3.906 3.910 3.915 3.920 3.924 3.929 3.934 3.938 3.943 3.948 1640

1650 3.948 3.952 3.957 3.962 3.966 3.971 3.976 3.980 3.985 3.990 3.994 16501660 3.994 3.999 4.004 4.009 4.013 4.018 4.023 4.027 4.032 4.037 4.041 16601670 4.041 4.046 4.051 4.056 4.060 4.065 4.070 4.075 4.079 4.084 4.089 16701680 4.089 4.093 4.098 4.103 4.108 4.112 4.117 4.122 4.127 4.131 4.136 16801690 4.136 4.141 4.146 4.151 4.155 4.160 4.165 4.170 4.174 4.179 4.184 1690

1700 4.184 4.189 4.194 4.198 4.203 4.208 4.213 4.217 4.222 4.227 4.232 17001710 4.232 4.237 4.242 4.246 4.251 4.256 4.261 4.266 4.270 4.275 4.280 17101720 4.280 4.285 4.290 4.295 4.299 4.304 4.309 4.314 4.319 4.324 4.328 17201730 4.328 4.333 4.338 4.343 4.348 4.353 4.358 4.362 4.367 4.372 4.377 17301740 4.377 4.382 4.387 4.392 4.397 4.401 4.406 4.411 4.416 4.421 4.426 1740

1750 4.426 4.431 4.436 4.441 4.445 4.450 4.455 4.460 4.465 4.470 4.475 17501760 4.475 4.480 4.485 4.490 4.495 4.500 4.504 4.509 4.514 4.519 4.524 17601770 4.524 4.529 4.534 4.539 4.544 4.549 4.554 4.559 4.564 4.569 4.574 17701780 4.574 4.579 4.584 4.589 4.593 4.598 4.603 4.608 4.613 4.618 4.623 17801790 4.623 4.628 4.633 4.638 4.643 4.648 4.653 4.658 4.663 4.668 4.673 1790

1800 4.673 4.678 4.683 4.688 4.693 4.698 4.703 4.708 4.713 4.718 4.723 18001810 4.723 4.728 4.733 4.738 4.743 4.748 4.754 4.759 4.764 4.769 4.774 18101820 4.774 4.779 4.784 4.789 4.794 4.799 4.804 4.809 4.814 4.819 4.824 18201830 4.824 4.829 4.834 4.839 4.844 4.850 4.855 4.860 4.865 4.870 4.875 18301840 4.875 4.880 4.885 4.890 4.895 4.900 4.905 4.911 4.916 4.921 4.926 1840

1850 4.926 4.931 4.936 4.941 4.946 4.951 4.957 4.962 4.967 4.972 4.977 18501860 4.977 4.982 4.987 4.992 4.998 5.003 5.008 5.013 5.018 5.023 5.028 18601870 5.028 5.034 5.039 5.044 5.049 5.054 5.059 5.065 5.070 5.075 5.080 18701880 5.080 5.085 5.090 5.096 5.101 5.106 5.111 5.116 5.121 5.127 5.132 18801890 5.132 5.137 5.142 5.147 5.153 5.158 5.163 5.168 5.173 5.179 5.184 1890

1900 5.184 5.189 5.194 5.199 5.205 5.210 5.215 5.220 5.225 5.231 5.236 19001910 5.236 5.241 5.246 5.252 5.257 5.262 5.267 5.273 5.278 5.283 5.288 19101920 5.288 5.294 5.299 5.304 5.309 5.315 5.320 5.325 5.330 5.336 5.341 19201930 5.341 5.346 5.351 5.357 5.362 5.367 5.373 5.378 5.383 5.388 5.394 19301940 5.394 5.399 5.404 5.410 5.415 5.420 5.425 5.431 5.436 5.441 5.447 1940

1950 5.447 5.452 5.457 5.463 5.468 5.473 5.479 5.484 5.489 5.495 5.500 19501960 5.500 5.505 5.511 5.516 5.521 5.527 5.532 5.537 5.543 5.548 5.553 19601970 5.553 5.559 5.564 5.569 5.575 5.580 5.585 5.591 5.596 5.601 5.607 19701980 5.607 5.612 5.618 5.623 5.628 5.634 5.639 5.644 5.650 5.655 5.661 19801990 5.661 5.666 5.671 5.677 5.682 5.688 5.693 5.698 5.704 5.709 5.715 1990

2000 5.715 5.720 5.725 5.731 5.736 5.742 5.747 5.752 5.758 5.763 5.769 20002010 5.769 5.774 5.780 5.785 5.790 5.796 5.801 5.807 5.812 5.818 5.823 20102020 5.823 5.828 5.834 5.839 5.845 5.850 5.856 5.861 5.867 5.872 5.878 20202030 5.878 5.883 5.888 5.894 5.899 5.905 5.910 5.916 5.921 5.927 5.932 20302040 5.932 5.938 5.943 5.949 5.954 5.960 5.965 5.971 5.976 5.982 5.987 2040

2050 5.987 5.993 5.998 6.004 6.009 6.015 6.020 6.026 6.031 6.037 6.042 20502060 6.042 6.048 6.053 6.059 6.064 6.070 6.075 6.081 6.086 6.092 6.098 20602070 6.098 6.103 6.109 6.114 6.120 6.125 6.131 6.136 6.142 6.147 6.153 20702080 6.153 6.159 6.164 6.170 6.175 6.181 6.186 6.192 6.197 6.203 6.209 20802090 6.209 6.214 6.220 6.225 6.231 6.237 6.242 6.248 6.253 6.259 6.264 2090

2100 6.264 6.270 6.276 6.281 6.287 6.292 6.298 6.304 6.309 6.315 6.320 21002110 6.320 6.326 6.332 6.337 6.343 6.349 6.354 6.360 6.365 6.371 6.377 21102120 6.377 6.382 6.388 6.394 6.399 6.405 6.410 6.416 6.422 6.427 6.433 21202130 6.433 6.439 6.444 6.450 6.456 6.461 6.467 6.473 6.478 6.484 6.490 21302140 6.490 6.495 6.501 6.507 6.512 6.518 6.524 6.529 6.535 6.541 6.546 2140

2150 6.546 6.552 6.558 6.563 6.569 6.575 6.580 6.586 6.592 6.597 6.603 21502160 6.603 6.609 6.615 6.620 6.626 6.632 6.637 6.643 6.649 6.655 6.660 21602170 6.660 6.666 6.672 6.677 6.683 6.689 6.695 6.700 6.706 6.712 6.718 21702180 6.718 6.723 6.729 6.735 6.740 6.746 6.752 6.758 6.763 6.769 6.775 21802190 6.775 6.781 6.786 6.792 6.798 6.804 6.809 6.815 6.821 6.827 6.833 2190

2200 6.833 6.838 6.844 6.850 6.856 6.861 6.867 6.873 6.879 6.884 6.890 22002210 6.890 6.896 6.902 6.908 6.913 6.919 6.925 6.931 6.937 6.942 6.948 22102220 6.948 6.954 6.960 6.966 6.971 6.977 6.983 6.989 6.995 7.000 7.006 22202230 7.006 7.012 7.018 7.024 7.030 7.035 7.041 7.047 7.053 7.059 7.065 22302240 7.065 7.070 7.076 7.082 7.088 7.094 7.100 7.105 7.111 7.117 7.123 2240

2250 7.123 7.129 7.135 7.141 7.146 7.152 7.158 7.164 7.170 7.176 7.182 22502260 7.182 7.187 7.193 7.199 7.205 7.211 7.217 7.223 7.229 7.234 7.240 22602270 7.240 7.246 7.252 7.258 7.264 7.270 7.276 7.281 7.287 7.293 7.299 22702280 7.299 7.305 7.311 7.317 7.323 7.329 7.335 7.340 7.346 7.352 7.358 22802290 7.358 7.364 7.370 7.376 7.382 7.388 7.394 7.400 7.406 7.412 7.417 2290

2300 7.417 7.423 7.429 7.435 7.441 7.447 7.453 7.459 7.465 7.471 7.477 23002310 7.477 7.483 7.489 7.495 7.501 7.507 7.512 7.518 7.524 7.530 7.536 23102320 7.536 7.542 7.548 7.554 7.560 7.566 7.572 7.578 7.584 7.590 7.596 23202330 7.596 7.602 7.608 7.614 7.620 7.626 7.632 7.638 7.644 7.650 7.656 23302340 7.656 7.662 7.668 7.674 7.680 7.686 7.692 7.698 7.704 7.710 7.716 2340

2350 7.716 7.722 7.728 7.734 7.740 7.746 7.752 7.758 7.764 7.770 7.776 23502360 7.776 7.782 7.788 7.794 7.800 7.806 7.812 7.818 7.824 7.830 7.836 23602370 7.836 7.842 7.848 7.854 7.860 7.866 7.872 7.878 7.884 7.891 7.897 23702380 7.897 7.903 7.909 7.915 7.921 7.927 7.933 7.939 7.945 7.951 7.957 23802390 7.957 7.963 7.969 7.975 7.981 7.987 7.994 8.000 8.006 8.012 8.018 2390

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 3092°F0 to 1700°CExtension Grade32 to 212°F0 to 100°CLIMITS OF ERROR(whichever is greater)Standard: 0.5°C over 800°CSpecial: NOT ESTABLISHEDCOMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High Temperature;Common Use in Glass IndustryTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°FBB

ThermocoupleGrade


Platinum-6% Rhodium

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-234

Z


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

2400 8.018 8.024 8.030 8.036 8.042 8.048 8.054 8.060 8.066 8.073 8.079 24002410 8.079 8.085 8.091 8.097 8.103 8.109 8.115 8.121 8.127 8.134 8.140 24102420 8.140 8.146 8.152 8.158 8.164 8.170 8.176 8.182 8.188 8.195 8.201 24202430 8.201 8.207 8.213 8.219 8.225 8.231 8.237 8.244 8.250 8.256 8.262 24302440 8.262 8.268 8.274 8.280 8.286 8.293 8.299 8.305 8.311 8.317 8.323 2440

2450 8.323 8.329 8.336 8.342 8.348 8.354 8.360 8.366 8.372 8.379 8.385 24502460 8.385 8.391 8.397 8.403 8.409 8.416 8.422 8.428 8.434 8.440 8.446 24602470 8.446 8.453 8.459 8.465 8.471 8.477 8.483 8.490 8.496 8.502 8.508 24702480 8.508 8.514 8.521 8.527 8.533 8.539 8.545 8.551 8.558 8.564 8.570 24802490 8.570 8.576 8.582 8.589 8.595 8.601 8.607 8.613 8.620 8.626 8.632 2490

2500 8.632 8.638 8.644 8.651 8.657 8.663 8.669 8.675 8.682 8.688 8.694 25002510 8.694 8.700 8.707 8.713 8.719 8.725 8.731 8.738 8.744 8.750 8.756 25102520 8.756 8.763 8.769 8.775 8.781 8.787 8.794 8.800 8.806 8.812 8.819 25202530 8.819 8.825 8.831 8.837 8.844 8.850 8.856 8.862 8.869 8.875 8.881 25302540 8.881 8.887 8.894 8.900 8.906 8.912 8.919 8.925 8.931 8.937 8.944 2540

2550 8.944 8.950 8.956 8.962 8.969 8.975 8.981 8.988 8.994 9.000 9.006 25502560 9.006 9.013 9.019 9.025 9.031 9.038 9.044 9.050 9.057 9.063 9.069 25602570 9.069 9.075 9.082 9.088 9.094 9.101 9.107 9.113 9.119 9.126 9.132 25702580 9.132 9.138 9.145 9.151 9.157 9.164 9.170 9.176 9.182 9.189 9.195 25802590 9.195 9.201 9.208 9.214 9.220 9.227 9.233 9.239 9.245 9.252 9.258 2590

2600 9.258 9.264 9.271 9.277 9.283 9.290 9.296 9.302 9.309 9.315 9.321 26002610 9.321 9.328 9.334 9.340 9.347 9.353 9.359 9.366 9.372 9.378 9.385 26102620 9.385 9.391 9.397 9.404 9.410 9.416 9.423 9.429 9.435 9.442 9.448 26202630 9.448 9.454 9.461 9.467 9.473 9.480 9.486 9.492 9.499 9.505 9.511 26302640 9.511 9.518 9.524 9.530 9.537 9.543 9.550 9.556 9.562 9.569 9.575 2640

2650 9.575 9.581 9.588 9.594 9.600 9.607 9.613 9.619 9.626 9.632 9.639 26502660 9.639 9.645 9.651 9.658 9.664 9.670 9.677 9.683 9.690 9.696 9.702 26602670 9.702 9.709 9.715 9.721 9.728 9.734 9.741 9.747 9.753 9.760 9.766 26702680 9.766 9.772 9.779 9.785 9.792 9.798 9.804 9.811 9.817 9.824 9.830 26802690 9.830 9.836 9.843 9.849 9.856 9.862 9.868 9.875 9.881 9.888 9.894 2690

2700 9.894 9.900 9.907 9.913 9.920 9.926 9.932 9.939 9.945 9.952 9.958 27002710 9.958 9.964 9.971 9.977 9.984 9.990 9.996 10.003 10.009 10.016 10.022 27102720 10.022 10.028 10.035 10.041 10.048 10.054 10.061 10.067 10.073 10.080 10.086 27202730 10.086 10.093 10.099 10.105 10.112 10.118 10.125 10.131 10.138 10.144 10.150 27302740 10.150 10.157 10.163 10.170 10.176 10.183 10.189 10.195 10.202 10.208 10.215 2740

2750 10.215 10.221 10.228 10.234 10.240 10.247 10.253 10.260 10.266 10.273 10.279 27502760 10.279 10.286 10.292 10.298 10.305 10.311 10.318 10.324 10.331 10.337 10.344 27602770 10.344 10.350 10.356 10.363 10.369 10.376 10.382 10.389 10.395 10.402 10.408 27702780 10.408 10.414 10.421 10.427 10.434 10.440 10.447 10.453 10.460 10.466 10.473 27802790 10.473 10.479 10.485 10.492 10.498 10.505 10.511 10.518 10.524 10.531 10.537 2790

2800 10.537 10.544 10.550 10.556 10.563 10.569 10.576 10.582 10.589 10.595 10.602 28002810 10.602 10.608 10.615 10.621 10.628 10.634 10.641 10.647 10.653 10.660 10.666 28102820 10.666 10.673 10.679 10.686 10.692 10.699 10.705 10.712 10.718 10.725 10.731 28202830 10.731 10.738 10.744 10.751 10.757 10.763 10.770 10.776 10.783 10.789 10.796 28302840 10.796 10.802 10.809 10.815 10.822 10.828 10.835 10.841 10.848 10.854 10.861 2840

2850 10.861 10.867 10.874 10.880 10.887 10.893 10.900 10.906 10.913 10.919 10.925 28502860 10.925 10.932 10.938 10.945 10.951 10.958 10.964 10.971 10.977 10.984 10.990 28602870 10.990 10.997 11.003 11.010 11.016 11.023 11.029 11.036 11.042 11.049 11.055 28702880 11.055 11.062 11.068 11.075 11.081 11.088 11.094 11.101 11.107 11.114 11.120 28802890 11.120 11.127 11.133 11.140 11.146 11.153 11.159 11.166 11.172 11.179 11.185 2890

2900 11.185 11.192 11.198 11.205 11.211 11.218 11.224 11.231 11.237 11.244 11.250 29002910 11.250 11.257 11.263 11.270 11.276 11.282 11.289 11.295 11.302 11.308 11.315 29102920 11.315 11.321 11.328 11.334 11.341 11.347 11.354 11.360 11.367 11.373 11.380 29202930 11.380 11.386 11.393 11.399 11.406 11.412 11.419 11.425 11.432 11.438 11.445 29302940 11.445 11.451 11.458 11.464 11.471 11.477 11.484 11.490 11.497 11.503 11.510 2940

2950 11.510 11.516 11.523 11.529 11.536 11.542 11.549 11.555 11.562 11.568 11.575 29502960 11.575 11.582 11.588 11.595 11.601 11.608 11.614 11.621 11.627 11.634 11.640 29602970 11.640 11.647 11.653 11.660 11.666 11.673 11.679 11.686 11.692 11.699 11.705 29702980 11.705 11.712 11.718 11.725 11.731 11.738 11.744 11.751 11.757 11.764 11.770 29802990 11.770 11.777 11.783 11.790 11.796 11.803 11.809 11.816 11.822 11.829 11.835 2990

3000 11.835 11.842 11.848 11.855 11.861 11.868 11.874 11.881 11.887 11.894 11.900 30003010 11.900 11.907 11.913 11.920 11.926 11.933 11.939 11.946 11.952 11.959 11.965 30103020 11.965 11.972 11.978 11.985 11.991 11.998 12.004 12.011 12.017 12.024 12.030 30203030 12.030 12.037 12.043 12.050 12.056 12.063 12.069 12.076 12.082 12.089 12.095 30303040 12.095 12.102 12.108 12.115 12.121 12.128 12.134 12.141 12.147 12.154 12.160 3040

3050 12.160 12.166 12.173 12.179 12.186 12.192 12.199 12.205 12.212 12.218 12.225 30503060 12.225 12.231 12.238 12.244 12.251 12.257 12.264 12.270 12.277 12.283 12.290 30603070 12.290 12.296 12.303 12.309 12.316 12.322 12.329 12.335 12.342 12.348 12.355 30703080 12.355 12.361 12.368 12.374 12.381 12.387 12.394 12.400 12.407 12.413 12.420 30803090 12.420 12.426 12.433 12.439 12.446 12.452 12.458 12.465 12.471 12.478 12.484 3090

3100 12.484 12.491 12.497 12.504 12.510 12.517 12.523 12.530 12.536 12.543 12.549 31003110 12.549 12.556 12.562 12.569 12.575 12.582 12.588 12.595 12.601 12.607 12.614 31103120 12.614 12.620 12.627 12.633 12.640 12.646 12.653 12.659 12.666 12.672 12.679 31203130 12.679 12.685 12.692 12.698 12.704 12.711 12.717 12.724 12.730 12.737 12.743 31303140 12.743 12.750 12.756 12.763 12.769 12.776 12.782 12.789 12.795 12.801 12.808 3140

3150 12.808 12.814 12.821 12.827 12.834 12.840 12.847 12.853 12.860 12.866 12.872 31503160 12.872 12.879 12.885 12.892 12.898 12.905 12.911 12.918 12.924 12.931 12.937 31603170 12.937 12.943 12.950 12.956 12.963 12.969 12.976 12.982 12.989 12.995 13.001 31703180 13.001 13.008 13.014 13.021 13.027 13.034 13.040 13.047 13.053 13.059 13.066 31803190 13.066 13.072 13.079 13.085 13.092 13.098 13.104 13.111 13.117 13.124 13.130 3190

3200 13.130 13.137 13.143 13.149 13.156 13.162 13.169 13.175 13.182 13.188 13.194 32003210 13.194 13.201 13.207 13.214 13.220 13.227 13.233 13.239 13.246 13.252 13.259 32103220 13.259 13.265 13.271 13.278 13.284 13.291 13.297 13.304 13.310 13.316 13.323 32203230 13.323 13.329 13.336 13.342 13.348 13.355 13.361 13.368 13.374 13.380 13.387 32303240 13.387 13.393 13.400 13.406 13.412 13.419 13.425 13.432 13.438 13.444 13.451 3240

3250 13.451 13.457 13.464 13.470 13.476 13.483 13.489 13.496 13.502 13.508 13.515 32503260 13.515 13.521 13.527 13.534 13.540 13.547 13.553 13.559 13.566 13.572 13.579 32603270 13.579 13.585 13.591 13.598 13.604 13.610 13.617 13.623 13.630 13.636 13.642 32703280 13.642 13.649 13.655 13.661 13.668 13.674 13.680 13.687 13.693 13.700 13.706 32803290 13.706 13.712 13.719 13.725 13.731 13.738 13.744 13.750 13.757 13.763 13.769 3290

3300 13.769 13.776 13.782 13.789 13.795 13.801 13.808 13.814 13.820 3300

MAXIMUM TEMPERATURE RANGEThermocouple Grade32 to 3092°F0 to 1700°CExtension Grade32 to 212°F0 to 100°CLIMITS OF ERROR(whichever is greater)Standard: 0.5°C over 800°CSpecial: NOT ESTABLISHEDCOMMENTS, BARE WIRE ENVIRONMENT:Oxidizing or Inert; Do Not Insert in Metal Tubes;Beware of Contamination; High Temperature;Common Use in Glass IndustryTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°F BB

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

ThermocoupleGrade


Platinum-6% Rhodium

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-235


°F -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

-450 -4.345 -4.345 -4.345 -4.344 -4.344 -450

-440 -4.344 -4.344 -4.343 -4.343 -4.342 -4.342 -4.341 -4.341 -4.340 -4.340 -4.339 -440-430 -4.339 -4.338 -4.337 -4.337 -4.336 -4.335 -4.334 -4.333 -4.332 -4.331 -4.330 -430-420 -4.330 -4.329 -4.327 -4.326 -4.325 -4.324 -4.322 -4.321 -4.319 -4.318 -4.316 -420-410 -4.316 -4.315 -4.313 -4.312 -4.310 -4.308 -4.306 -4.305 -4.303 -4.301 -4.299 -410-400 -4.299 -4.297 -4.295 -4.293 -4.291 -4.288 -4.286 -4.284 -4.282 -4.279 -4.277 -400

-390 -4.277 -4.275 -4.272 -4.270 -4.267 -4.264 -4.262 -4.259 -4.256 -4.254 -4.251 -390-380 -4.251 -4.248 -4.245 -4.242 -4.239 -4.236 -4.233 -4.230 -4.226 -4.223 -4.220 -380-370 -4.220 -4.217 -4.213 -4.210 -4.206 -4.203 -4.199 -4.196 -4.192 -4.189 -4.185 -370-360 -4.185 -4.181 -4.177 -4.174 -4.170 -4.166 -4.162 -4.158 -4.154 -4.150 -4.145 -360-350 -4.145 -4.141 -4.137 -4.133 -4.128 -4.124 -4.120 -4.115 -4.111 -4.106 -4.102 -350

-340 -4.102 -4.097 -4.092 -4.088 -4.083 -4.078 -4.073 -4.068 -4.064 -4.059 -4.054 -340-330 -4.054 -4.049 -4.043 -4.038 -4.033 -4.028 -4.023 -4.017 -4.012 -4.007 -4.001 -330-320 -4.001 -3.996 -3.990 -3.985 -3.979 -3.974 -3.968 -3.962 -3.957 -3.951 -3.945 -320-310 -3.945 -3.939 -3.933 -3.927 -3.921 -3.915 -3.909 -3.903 -3.897 -3.891 -3.884 -310-300 -3.884 -3.878 -3.872 -3.866 -3.859 -3.853 -3.846 -3.840 -3.833 -3.827 -3.820 -300

-290 -3.820 -3.813 -3.807 -3.800 -3.793 -3.786 -3.779 -3.773 -3.766 -3.759 -3.752 -290-280 -3.752 -3.745 -3.738 -3.730 -3.723 -3.716 -3.709 -3.702 -3.694 -3.687 -3.679 -280-270 -3.679 -3.672 -3.665 -3.657 -3.650 -3.642 -3.634 -3.627 -3.619 -3.611 -3.604 -270-260 -3.604 -3.596 -3.588 -3.580 -3.572 -3.564 -3.556 -3.548 -3.540 -3.532 -3.524 -260-250 -3.524 -3.516 -3.508 -3.499 -3.491 -3.483 -3.474 -3.466 -3.458 -3.449 -3.441 -250

-240 -3.441 -3.432 -3.424 -3.415 -3.407 -3.398 -3.389 -3.380 -3.372 -3.363 -3.354 -240-230 -3.354 -3.345 -3.336 -3.327 -3.318 -3.309 -3.300 -3.291 -3.282 -3.273 -3.264 -230-220 -3.264 -3.255 -3.246 -3.236 -3.227 -3.218 -3.208 -3.199 -3.189 -3.180 -3.171 -220-210 -3.171 -3.161 -3.151 -3.142 -3.132 -3.123 -3.113 -3.103 -3.093 -3.084 -3.074 -210-200 -3.074 -3.064 -3.054 -3.044 -3.034 -3.024 -3.014 -3.004 -2.994 -2.984 -2.974 -200

-190 -2.974 -2.964 -2.954 -2.943 -2.933 -2.923 -2.912 -2.902 -2.892 -2.881 -2.871 -190-180 -2.871 -2.860 -2.850 -2.839 -2.829 -2.818 -2.808 -2.797 -2.786 -2.776 -2.765 -180-170 -2.765 -2.754 -2.743 -2.733 -2.722 -2.711 -2.700 -2.689 -2.678 -2.667 -2.656 -170-160 -2.656 -2.645 -2.634 -2.623 -2.612 -2.601 -2.589 -2.578 -2.567 -2.556 -2.544 -160-150 -2.544 -2.533 -2.522 -2.510 -2.499 -2.488 -2.476 -2.465 -2.453 -2.442 -2.430 -150

-140 -2.430 -2.418 -2.407 -2.395 -2.384 -2.372 -2.360 -2.348 -2.337 -2.325 -2.313 -140-130 -2.313 -2.301 -2.289 -2.277 -2.265 -2.254 -2.242 -2.230 -2.218 -2.206 -2.193 -130-120 -2.193 -2.181 -2.169 -2.157 -2.145 -2.133 -2.121 -2.108 -2.096 -2.084 -2.072 -120-110 -2.072 -2.059 -2.047 -2.035 -2.022 -2.010 -1.997 -1.985 -1.972 -1.960 -1.947 -110-100 -1.947 -1.935 -1.922 -1.910 -1.897 -1.884 -1.872 -1.859 -1.846 -1.834 -1.821 -100

-90 -1.821 -1.808 -1.795 -1.783 -1.770 -1.757 -1.744 -1.731 -1.718 -1.705 -1.692 -90-80 -1.692 -1.679 -1.666 -1.653 -1.640 -1.627 -1.614 -1.601 -1.588 -1.575 -1.562 -80-70 -1.562 -1.549 -1.536 -1.522 -1.509 -1.496 -1.483 -1.470 -1.456 -1.443 -1.430 -70-60 -1.430 -1.416 -1.403 -1.390 -1.376 -1.363 -1.349 -1.336 -1.323 -1.309 -1.296 -60-50 -1.296 -1.282 -1.269 -1.255 -1.242 -1.228 -1.214 -1.201 -1.187 -1.174 -1.160 -50

-40 -1.160 -1.146 -1.133 -1.119 -1.105 -1.092 -1.078 -1.064 -1.050 -1.037 -1.023 -40-30 -1.023 -1.009 -0.995 -0.981 -0.967 -0.954 -0.940 -0.926 -0.912 -0.898 -0.884 -30-20 -0.884 -0.870 -0.856 -0.842 -0.828 -0.814 -0.800 -0.786 -0.772 -0.758 -0.744 -20-10 -0.744 -0.730 -0.716 -0.702 -0.688 -0.674 -0.660 -0.646 -0.632 -0.617 -0.603 -10

0 -0.603 -0.589 -0.575 -0.561 -0.546 -0.532 -0.518 -0.504 -0.490 -0.475 -0.461 0

0 -0.461 -0.447 -0.433 -0.418 -0.404 -0.390 -0.375 -0.361 -0.347 -0.332 -0.318 010 -0.318 -0.304 -0.289 -0.275 -0.260 -0.246 -0.232 -0.217 -0.203 -0.188 -0.174 1020 -0.174 -0.159 -0.145 -0.131 -0.116 -0.102 -0.087 -0.073 -0.058 -0.044 -0.029 2030 -0.029 -0.015 0.000 0.014 0.029 0.043 0.058 0.072 0.087 0.101 0.116 3040 0.116 0.130 0.145 0.159 0.174 0.188 0.203 0.217 0.232 0.246 0.261 40

50 0.261 0.275 0.290 0.305 0.319 0.334 0.349 0.363 0.378 0.393 0.407 5060 0.407 0.422 0.437 0.451 0.466 0.481 0.496 0.510 0.525 0.540 0.555 6070 0.555 0.570 0.584 0.599 0.614 0.629 0.644 0.659 0.674 0.688 0.703 7080 0.703 0.718 0.733 0.748 0.763 0.778 0.793 0.808 0.823 0.838 0.853 8090 0.853 0.868 0.883 0.898 0.913 0.928 0.943 0.958 0.974 0.989 1.004 90

100 1.004 1.019 1.034 1.049 1.065 1.080 1.095 1.110 1.125 1.141 1.156 100110 1.156 1.171 1.186 1.202 1.217 1.232 1.248 1.263 1.278 1.294 1.309 110120 1.309 1.324 1.340 1.355 1.371 1.386 1.402 1.417 1.432 1.448 1.463 120130 1.463 1.479 1.494 1.510 1.525 1.541 1.557 1.572 1.588 1.603 1.619 130140 1.619 1.635 1.650 1.666 1.682 1.697 1.713 1.729 1.744 1.760 1.776 140

150 1.776 1.791 1.807 1.823 1.839 1.855 1.870 1.886 1.902 1.918 1.934 150160 1.934 1.950 1.965 1.981 1.997 2.013 2.029 2.045 2.061 2.077 2.093 160170 2.093 2.109 2.125 2.141 2.157 2.173 2.189 2.205 2.221 2.237 2.253 170180 2.253 2.269 2.285 2.301 2.318 2.334 2.350 2.366 2.382 2.398 2.415 180190 2.415 2.431 2.447 2.463 2.480 2.496 2.512 2.528 2.545 2.561 2.577 190

200 2.577 2.594 2.610 2.626 2.643 2.659 2.676 2.692 2.708 2.725 2.741 200210 2.741 2.758 2.774 2.791 2.807 2.824 2.840 2.857 2.873 2.890 2.906 210220 2.906 2.923 2.939 2.956 2.973 2.989 3.006 3.022 3.039 3.056 3.072 220230 3.072 3.089 3.106 3.123 3.139 3.156 3.173 3.189 3.206 3.223 3.240 230240 3.240 3.257 3.273 3.290 3.307 3.324 3.341 3.358 3.374 3.391 3.408 240

250 3.408 3.425 3.442 3.459 3.476 3.493 3.510 3.527 3.544 3.561 3.578 250260 3.578 3.595 3.612 3.629 3.646 3.663 3.680 3.697 3.714 3.731 3.748 260270 3.748 3.766 3.783 3.800 3.817 3.834 3.851 3.869 3.886 3.903 3.920 270280 3.920 3.937 3.955 3.972 3.989 4.007 4.024 4.041 4.058 4.076 4.093 280290 4.093 4.110 4.128 4.145 4.162 4.180 4.197 4.215 4.232 4.250 4.267 290

300 4.267 4.284 4.302 4.319 4.337 4.354 4.372 4.389 4.407 4.424 4.442 300310 4.442 4.459 4.477 4.495 4.512 4.530 4.547 4.565 4.583 4.600 4.618 310320 4.618 4.635 4.653 4.671 4.688 4.706 4.724 4.742 4.759 4.777 4.795 320330 4.795 4.813 4.830 4.848 4.866 4.884 4.901 4.919 4.937 4.955 4.973 330340 4.973 4.991 5.008 5.026 5.044 5.062 5.080 5.098 5.116 5.134 5.152 340

350 5.152 5.170 5.188 5.206 5.224 5.241 5.259 5.277 5.295 5.314 5.332 350360 5.332 5.350 5.368 5.386 5.404 5.422 5.440 5.458 5.476 5.494 5.512 360370 5.512 5.531 5.549 5.567 5.585 5.603 5.621 5.639 5.658 5.676 5.694 370380 5.694 5.712 5.731 5.749 5.767 5.785 5.804 5.822 5.840 5.858 5.877 380390 5.877 5.895 5.913 5.932 5.950 5.968 5.987 6.005 6.024 6.042 6.060 390

400 6.060 6.079 6.097 6.116 6.134 6.152 6.171 6.189 6.208 6.226 6.245 400410 6.245 6.263 6.282 6.300 6.319 6.337 6.356 6.374 6.393 6.411 6.430 410420 6.430 6.449 6.467 6.486 6.504 6.523 6.542 6.560 6.579 6.597 6.616 420430 6.616 6.635 6.653 6.672 6.691 6.710 6.728 6.747 6.766 6.784 6.803 430440 6.803 6.822 6.841 6.859 6.878 6.897 6.916 6.934 6.953 6.972 6.991 440

450 6.991 7.010 7.029 7.047 7.066 7.085 7.104 7.123 7.142 7.161 7.179 450460 7.179 7.198 7.217 7.236 7.255 7.274 7.293 7.312 7.331 7.350 7.369 460470 7.369 7.388 7.407 7.426 7.445 7.464 7.483 7.502 7.521 7.540 7.559 470480 7.559 7.578 7.597 7.616 7.635 7.654 7.673 7.692 7.711 7.731 7.750 480490 7.750 7.769 7.788 7.807 7.826 7.845 7.865 7.884 7.903 7.922 7.941 490

500 7.941 7.960 7.980 7.999 8.018 8.037 8.057 8.076 8.095 8.114 8.134 500510 8.134 8.153 8.172 8.191 8.211 8.230 8.249 8.269 8.288 8.307 8.327 510520 8.327 8.346 8.365 8.385 8.404 8.423 8.443 8.462 8.482 8.501 8.520 520530 8.520 8.540 8.559 8.579 8.598 8.617 8.637 8.656 8.676 8.695 8.715 530540 8.715 8.734 8.754 8.773 8.793 8.812 8.832 8.851 8.871 8.890 8.910 540

550 8.910 8.929 8.949 8.968 8.988 9.008 9.027 9.047 9.066 9.086 9.105 550560 9.105 9.125 9.145 9.164 9.184 9.204 9.223 9.243 9.262 9.282 9.302 560570 9.302 9.321 9.341 9.361 9.381 9.400 9.420 9.440 9.459 9.479 9.499 570580 9.499 9.519 9.538 9.558 9.578 9.598 9.617 9.637 9.657 9.677 9.696 580590 9.696 9.716 9.736 9.756 9.776 9.795 9.815 9.835 9.855 9.875 9.895 590

600 9.895 9.914 9.934 9.954 9.974 9.994 10.014 10.034 10.054 10.073 10.093 600610 10.093 10.113 10.133 10.153 10.173 10.193 10.213 10.233 10.253 10.273 10.293 610620 10.293 10.313 10.333 10.353 10.373 10.393 10.413 10.433 10.453 10.473 10.493 620630 10.493 10.513 10.533 10.553 10.573 10.593 10.613 10.633 10.653 10.673 10.693 630640 10.693 10.713 10.733 10.753 10.774 10.794 10.814 10.834 10.854 10.874 10.894 640

650 10.894 10.914 10.934 10.955 10.975 10.995 11.015 11.035 11.055 11.076 11.096 650660 11.096 11.116 11.136 11.156 11.177 11.197 11.217 11.237 11.257 11.278 11.298 660670 11.298 11.318 11.338 11.359 11.379 11.399 11.419 11.440 11.460 11.480 11.501 670680 11.501 11.521 11.541 11.561 11.582 11.602 11.622 11.643 11.663 11.683 11.704 680690 11.704 11.724 11.744 11.765 11.785 11.805 11.826 11.846 11.867 11.887 11.907 690

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 450 to 2372°F– 270 to 1300°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 2.2°C or 0.75% Above 0°C2.2°C or 2.0% Below 0°CSpecial: 1.1°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Alternative to Type K; More Stable at High TemperaturesTEMPERATURE IN DEGREES °F REFERENCE JUNCTION AT 32°FNN

ThermocoupleGrade



0.1% Magnesium

ExtensionGrade

+–

+–



Z-236

Z


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

700 11.907 11.928 11.948 11.968 11.989 12.009 12.030 12.050 12.071 12.091 12.111 700710 12.111 12.132 12.152 12.173 12.193 12.214 12.234 12.255 12.275 12.295 12.316 710720 12.316 12.336 12.357 12.377 12.398 12.418 12.439 12.459 12.480 12.500 12.521 720730 12.521 12.542 12.562 12.583 12.603 12.624 12.644 12.665 12.685 12.706 12.726 730740 12.726 12.747 12.768 12.788 12.809 12.829 12.850 12.871 12.891 12.912 12.932 740

750 12.932 12.953 12.974 12.994 13.015 13.036 13.056 13.077 13.098 13.118 13.139 750760 13.139 13.159 13.180 13.201 13.221 13.242 13.263 13.284 13.304 13.325 13.346 760770 13.346 13.366 13.387 13.408 13.428 13.449 13.470 13.491 13.511 13.532 13.553 770780 13.553 13.574 13.594 13.615 13.636 13.657 13.677 13.698 13.719 13.740 13.760 780790 13.760 13.781 13.802 13.823 13.844 13.864 13.885 13.906 13.927 13.948 13.969 790

800 13.969 13.989 14.010 14.031 14.052 14.073 14.094 14.114 14.135 14.156 14.177 800810 14.177 14.198 14.219 14.240 14.260 14.281 14.302 14.323 14.344 14.365 14.386 810820 14.386 14.407 14.428 14.448 14.469 14.490 14.511 14.532 14.553 14.574 14.595 820830 14.595 14.616 14.637 14.658 14.679 14.700 14.721 14.742 14.763 14.784 14.804 830840 14.804 14.825 14.846 14.867 14.888 14.909 14.930 14.951 14.972 14.993 15.014 840

850 15.014 15.035 15.056 15.077 15.098 15.119 15.140 15.162 15.183 15.204 15.225 850860 15.225 15.246 15.267 15.288 15.309 15.330 15.351 15.372 15.393 15.414 15.435 860870 15.435 15.456 15.477 15.498 15.520 15.541 15.562 15.583 15.604 15.625 15.646 870880 15.646 15.667 15.688 15.709 15.731 15.752 15.773 15.794 15.815 15.836 15.857 880890 15.857 15.878 15.900 15.921 15.942 15.963 15.984 16.005 16.027 16.048 16.069 890

900 16.069 16.090 16.111 16.132 16.154 16.175 16.196 16.217 16.238 16.260 16.281 900910 16.281 16.302 16.323 16.344 16.366 16.387 16.408 16.429 16.450 16.472 16.493 910920 16.493 16.514 16.535 16.557 16.578 16.599 16.620 16.642 16.663 16.684 16.705 920930 16.705 16.727 16.748 16.769 16.790 16.812 16.833 16.854 16.875 16.897 16.918 930940 16.918 16.939 16.961 16.982 17.003 17.025 17.046 17.067 17.088 17.110 17.131 940

950 17.131 17.152 17.174 17.195 17.216 17.238 17.259 17.280 17.302 17.323 17.344 950960 17.344 17.366 17.387 17.408 17.430 17.451 17.472 17.494 17.515 17.536 17.558 960970 17.558 17.579 17.601 17.622 17.643 17.665 17.686 17.707 17.729 17.750 17.772 970980 17.772 17.793 17.814 17.836 17.857 17.879 17.900 17.921 17.943 17.964 17.986 980990 17.986 18.007 18.028 18.050 18.071 18.093 18.114 18.136 18.157 18.178 18.200 990

1000 18.200 18.221 18.243 18.264 18.286 18.307 18.328 18.350 18.371 18.393 18.414 10001010 18.414 18.436 18.457 18.479 18.500 18.522 18.543 18.565 18.586 18.608 18.629 10101020 18.629 18.650 18.672 18.693 18.715 18.736 18.758 18.779 18.801 18.822 18.844 10201030 18.844 18.865 18.887 18.908 18.930 18.951 18.973 18.994 19.016 19.037 19.059 10301040 19.059 19.081 19.102 19.124 19.145 19.167 19.188 19.210 19.231 19.253 19.274 1040

1050 19.274 19.296 19.317 19.339 19.360 19.382 19.404 19.425 19.447 19.468 19.490 10601060 19.490 19.511 19.533 19.554 19.576 19.598 19.619 19.641 19.662 19.684 19.705 10601070 19.705 19.727 19.749 19.770 19.792 19.813 19.835 19.857 19.878 19.900 19.921 10701080 19.921 19.943 19.964 19.986 20.008 20.029 20.051 20.072 20.094 20.116 20.137 10601090 20.137 20.159 20.181 20.202 20.224 20.245 20.267 20.289 20.310 20.332 20.353 1090

1100 20.353 20.375 20.397 20.418 20.440 20.462 20.483 20.505 20.527 20.548 20.570 11001110 20.570 20.591 20.613 20.635 20.656 20.678 20.700 20.721 20.743 20.765 20.786 11101120 20.786 20.808 20.830 20.851 20.873 20.895 20.916 20.938 20.960 20.981 21.003 11201130 21.003 21.025 21.046 21.068 21.090 21.111 21.133 21.155 21.176 21.198 21.220 11301140 21.220 21.241 21.263 21.285 21.306 21.328 21.350 21.371 21.393 21.415 21.437 1140

1150 21.437 21.458 21.480 21.502 21.523 21.545 21.567 21.588 21.610 21.632 21.654 11501160 21.654 21.675 21.697 21.719 21.740 21.762 21.784 21.806 21.827 21.849 21.871 11601170 21.871 21.892 21.914 21.936 21.958 21.979 22.001 22.023 22.044 22.066 22.088 11701180 22.088 22.110 22.131 22.153 22.175 22.197 22.218 22.240 22.262 22.284 22.305 11801190 22.305 22.327 22.349 22.370 22.392 22.414 22.436 22.457 22.479 22.501 22.523 1190

1200 22.523 22.544 22.566 22.588 22.610 22.631 22.653 22.675 22.697 22.718 22.740 12001210 22.740 22.762 22.784 22.805 22.827 22.849 22.871 22.893 22.914 22.936 22.958 12101220 22.958 22.980 23.001 23.023 23.045 23.067 23.088 23.110 23.132 23.154 23.178 12201230 23.176 23.197 23.219 23.241 23.263 23.284 23.306 23.328 23.350 23.372 23.393 12301240 23.393 23.415 23.437 23.459 23.480 23.502 23.524 23.546 23.568 23.589 23.611 1240

1250 23.611 23.633 23.655 23.676 23.698 23.720 23.742 23.764 23.785 23.807 23.829 12501260 23.829 23.851 23.873 23.894 23.916 23.938 23.960 23.982 24.003 24.025 24.047 12601270 24.047 24.069 24.091 24.112 24.134 24.156 24.178 24.200 24.221 24.243 24.265 12701280 24.265 24.287 24.309 24.330 24.352 24.374 24.396 24.418 24.439 24.461 24.483 12801290 24.483 24.505 24.527 24.548 24.570 24.592 24.614 24.636 24.658 24.679 24.701 1290

1300 24.701 24.723 24.745 24.767 24.788 24.810 24.832 24.854 24.876 24.897 24.919 13001310 24.919 24.941 24.963 24.985 25.007 25.028 25.050 25.072 25.094 25.116 25.137 13101320 25.137 25.159 25.181 25.203 25.225 25.247 25.268 25.290 25.312 25.334 25.356 13201330 25.356 25.377 25.399 25.421 25.443 25.465 25.487 25.508 25.530 25.552 25.574 13301340 25.574 25.596 25.618 25.639 25.661 25.683 25.705 25.727 25.748 25.770 25.792 1340

1350 25.792 25.814 25.836 25.858 25.879 25.901 25.923 25.945 25.967 25.989 26.010 13501360 26.010 26.032 26.054 26.076 26.098 26.119 26.141 26.163 26.185 26.207 26.229 13601370 26.229 26.250 26.272 26.294 26.316 26.338 26.360 26.381 26.403 26.425 26.447 13701380 26.447 26.469 26.491 26.512 26.534 26.556 26.578 26.600 26.622 26.643 26.665 13801390 26.665 26.687 26.709 26.731 26.752 26.774 26.796 26.818 26.840 26.862 26.883 1390

1400 26.883 26.905 26.927 26.949 26.971 26.993 27.014 27.036 27.058 27.080 27.102 14001410 27.102 27.124 27.145 27.167 27.189 27.211 27.233 27.254 27.276 27.298 27.320 14101420 27.320 27.342 27.364 27.385 27.407 27.429 27.451 27.473 27.495 27.516 27.538 14201430 27.538 27.560 27.582 27.604 27.625 27.647 27.669 27.691 27.713 27.735 27.756 14301440 27.756 27.778 27.800 27.822 27.844 27.866 27.887 27.909 27.931 27.953 27.975 1440

1450 27.975 27.996 28.018 28.040 28.062 28.084 28.105 28.127 28.149 28.171 28.193 14501460 28.193 28.215 28.236 28.258 28.280 28.302 28.324 28.345 28.367 28.389 28.411 14601470 28.411 28.433 28.455 28.476 28.498 28.520 28.542 28.564 28.585 28.607 28.629 14701480 28.629 28.651 28.673 28.694 28.716 28.738 28.760 28.782 28.803 28.825 28.847 14801490 28.847 28.869 28.891 28.912 28.934 28.956 28.978 29.000 29.021 29.043 29.065 1490

1500 29.085 29.087 29.109 29.130 29.152 29.174 29.196 29.218 29.239 29.261 29.283 15001510 29.283 29.305 29.327 29.348 29.370 29.392 29.414 29.436 29.457 29.479 29.501 15101520 29.501 29.523 29.545 29.566 29.588 29.610 29.632 29.653 29.675 29.697 29.719 I5201530 29.719 29.741 29.762 29.784 29.806 29.828 29.850 29.871 29.893 29.915 29.937 I5301540 29.937 29.958 29.980 30.002 30.024 30.046 30.067 30.089 30.111 30.133 30.154 IS40

1550 30.154 30.176 30.198 30.220 30.242 30.263 30.285 30.307 30.329 30.350 30.372 15501560 30.372 30.304 30.416 30.437 30.459 30.481 30.503 30.524 30.546 30.568 30.590 15601570 30.590 30.611 30.633 30.655 30.677 30.699 30.720 30.742 30.764 30.786 30.807 15701580 30.807 30.829 30.851 30.873 30.894 30.916 30.938 30.960 30.981 31.003 31.025 15801590 31.025 31.047 31.068 31.090 31.112 31.133 31.155 31.177 31.199 31.220 31.242 1590

1600 31.242 31.264 31.286 31.307 31.329 31.351 31.373 31.394 31.416 31.438 31.459 16001610 31.450 31.481 31.503 31.525 31.546 31.568 31.590 31.612 31.633 31.655 31.677 16101620 31.677 31.698 31.720 31.742 31.764 31.785 31.807 31.829 31.850 31.872 31.894 16201630 31.894 31.916 31.937 31.959 31.981 32.002 32.024 32.046 32.068 32.089 32.111 16301640 32.111 32.133 32.154 32.176 32.198 32.219 32.241 32.263 32.284 32.306 32.328 1640

1650 32.328 32.350 32.371 32.393 32.415 32.436 32.458 32.480 32.501 32.523 32.545 16501660 32.545 32.566 32.588 32.610 32.631 32.653 32.675 32.696 32.718 32.740 32.761 16601670 32.716 32.783 32.805 32.826 32.848 32.870 32.891 32.913 32.935 32.956 32.978 16701680 32.978 32.000 32.021 32.043 33.065 35.086 33.108 33.130 33.151 33.173 33.195 16801690 33.195 33.216 33.238 33.260 33.281 33.303 33.325 33.346 33.368 33.389 33.411 1690

1700 33.411 33.433 33.454 33.476 33.498 33.519 33.541 33.563 33.584 33.606 33.627 17001710 33.627 33.649 33.671 33.692 33.714 33.736 33.757 33.779 33.800 33.822 33.844 17101720 33.844 33.865 33.887 33.908 33.930 33.952 33.973 33.995 34.016 34.038 34.060 17201730 34.060 34.081 34.103 34.124 34.146 34.168 34.189 34.211 34.232 34.254 34.276 17301740 34.276 34.297 34.319 34.340 34.362 34.384 34.405 34.427 34.448 34.470 34.491 1740

1750 34.491 34.513 34.535 34.556 34.578 34.599 34.621 34.642 34.664 34.686 34.707 17501760 34.707 34.729 34.750 34.772 34.793 34.815 34.836 34.858 34.879 34.901 34.923 17601770 34.923 34.944 34.966 34.987 35.009 35.030 35.052 35.073 35.095 35.116 35.138 17701790 35.138 35.160 35.181 35.203 35.224 35.246 35.267 35.289 35.310 35.332 35.353 17801790 35.353 35.375 35.396 35.418 35.439 35.461 35.482 35.504 35.525 35.547 35.568 1790

1800 35.568 35.590 35.611 35.633 35.654 35.676 35.697 35.719 35.740 35.762 35.783 18001810 35.783 35.805 35.826 35.848 35.869 35.891 35.912 35.934 35.955 35.977 35.998 18101820 35.998 35.019 36.041 36.062 36.084 36.105 36.127 36.148 36.170 36.191 36.213 18201830 35.213 35.234 36.256 36.277 36.298 36.320 36.341 36.363 36.384 36.406 36.427 18301840 36.427 36.449 36.470 36.491 36.513 36.534 36.556 36.577 36.599 36.620 36.641 1840

1850 36.841 36.663 36.684 36.706 36.727 36.748 36.770 36.791 38.813 36.834 36.855 18501860 36.855 36.877 36.898 36.920 36.941 36.962 36.984 37.005 37.027 37.048 37.069 18601870 37.069 37.091 37.112 37.134 37.155 37.176 37.198 37.219 37.240 37.262 37.283 18701880 37.283 37.305 37.326 37.347 37.369 37.390 37.411 37.433 37.454 37.475 37.497 188018901 37.497 37.518 37.539 37.561 37.582 37.603 37.625 37.646 37.667 37.689 37.710 1890

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 450 to 2372°F– 270 to 1300°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 2.2°C or 0.75% Above 0°C2.2°C or 2.0% Below 0°CSpecial: 1.1°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Alternative to Type K; More Stable at High TemperaturesTEMPERATURE IN DEGREES °F REFERENCE JUNCTION AT 32°F NN

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

ThermocoupleGrade



0.1% Magnesium

ExtensionGrade

+–

+–



Z-237


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

1900 37.710 37.731 37.753 37.774 37.795 37.817 37.838 37.859 37.881 37.902 37.923 19001910 37.923 37.945 37.966 37.987 38.009 38.030 38.051 38.073 38.094 38.115 38.136 19101920 38.136 38.158 38.179 38.200 38.222 38.243 38.264 38.285 38.307 38.328 38.349 19201930 38.349 38.370 38.392 38.413 38.434 38.456 38.477 38.498 38.519 38.541 38.562 19301940 38.562 38.583 38.604 38.626 38.647 38.668 38.689 38.711 38.732 38.753 38.774 1940

1950 38.774 38.795 38.817 38.838 38.859 38.880 38.902 38.923 38.944 38.965 38.986 19501960 38.986 39.008 38.029 39.050 39.071 39.093 39.114 39.135 39.156 39.177 39.198 19601970 39.198 39.220 39.241 39.262 39.283 39.304 39.326 39.347 39.368 39.389 39.410 19701980 39.410 39.431 39.453 39.474 39.495 39.516 39.537 39.558 39.580 39.601 39.622 19801990 39.622 39.643 39.664 39.685 39.706 39.728 39.749 39.770 39.791 39.812 39.833 1990

2000 39.833 39.854 39.875 39.897 39.918 39.939 39.960 39.981 40.002 40.023 40.044 20002010 40.044 40.066 40.087 40.108 40.129 40.150 40.171 40.192 40.213 40.234 40.255 20102020 40.255 40.276 40.297 40.319 40.340 40.361 40.382 40.403 40.424 40.445 40.466 20202030 40.466 40.487 40.508 40.529 40.550 40.571 40.592 40.613 40.634 40.655 40.677 20302040 40.677 40.698 40.719 40.740 40.761 40.782 40.803 40.824 40.845 40.866 40.887 2040

2050 40.887 40.908 40.929 40.95O 40.971 40.992 41.013 41.034 41.055 41.076 41.097 20502060 41.097 41.118 41.139 41.160 41.181 41.202 41.223 41.244 41.265 41.286 41.307 20602070 41.307 41.328 41.349 41.370 41.390 41.411 41.432 41.453 41.474 41.495 41.516 20702080 41.516 41.537 41.558 41.579 41.600 41.621 41.642 41.663 41.684 41.705 41.725 20802090 41.725 41.746 41.767 41.788 41.809 41.830 41.851 41.872 41.893 41.914 41.935 2090

2100 41.935 41.955 41.976 41.997 42.018 42.039 42.060 42.081 42.102 42.123 42.143 21002110 42.143 42.164 42.185 42.206 42.227 42.248 42.269 42.289 42.310 42.331 42.352 21102120 42.352 42.373 42.394 42.415 42.435 42.456 42.477 42.498 42.519 42.540 42.560 21202130 42.560 42.581 42.602 42.623 42.644 42.664 42.685 42.706 42.727 42.748 42.768 21302140 42.768 42.789 42.810 42.831 42.852 42.872 42.893 42.914 42.935 42.956 42.976 2140

2150 42.976 42.997 43.018 43.039 43.059 43.080 43.101 43.122 43.142 43.163 43.184 21502160 43.184 43.205 43.225 43.246 43.267 43.288 43.308 43.329 43.350 43.370 43.391 21602170 43.391 43.412 43.433 43.453 43.474 43.495 43.515 43.536 43.557 43.578 43.598 21702180 43.598 43.619 43.640 43.660 43.681 43.702 43.722 43.743 43.764 43.784 43.805 21802190 43.805 43.826 43.846 43.867 43.888 43.908 43.929 43.950 43.970 43.991 43.012 2190

2200 44.012 44.032 44.053 44.073 44.094 44.115 44.135 44.156 44.177 44.197 44.218 22002210 44.218 44.238 44.259 44.280 44.300 44.321 44.341 44.362 44.383 44.403 44.424 22102220 44.424 44.444 44.465 44.485 44.506 44.527 44.547 44.568 44.588 44.609 44.629 22202230 44.629 44.650 44.671 44.691 44.712 44.732 44.753 44.773 44.794 44.814 44.835 22302240 44.835 44.855 44.876 44.896 44.917 44.937 44.958 44.978 44.999 45.019 45.040 2240

2250 45.040 45.060 45.081 45.101 45.122 45.142 45.163 45.183 45.204 45.224 45.245 22502260 45.245 45.265 45.286 45.306 45.326 45.347 45.367 45.388 45.408 45.429 45.449 22602270 45.449 45.469 45.490 45.510 45.531 45.551 45.572 45.592 45.612 45.633 45.653 22702280 45.653 45.674 45.694 45.714 45.735 45.755 45.775 45.796 45.816 45.837 45.857 22802290 45.857 45.877 45.898 45.918 45.938 45.959 45.979 45.999 46.020 46.040 46.060 2290

2300 46.060 46.081 46.101 46.121 46.142 46.162 46.182 46.202 46.223 46.243 46.263 23002310 46.263 46.284 46.304 46.324 46.344 46.365 46.385 46.405 46.425 46.446 46.466 23102320 46.466 46.486 46.506 46.527 46.547 46.567 48.587 46.608 46.628 46.648 46.668 23202330 46.668 46.688 46.709 46.729 46.749 46.769 48.789 46.810 48.830 46.850 46.870 23302340 48.870 46.890 46.910 48.931 46.951 46.971 48.991 47.011 47-031 47.051 47.071 2340

2350 47.071 47.092 47.112 47.132 47.152 47.172 47.192 47.212 47.232 47.252 47.272 23502360 47.272 47.292 47.312 47.333 47.353 47.373 47.393 47.413 47.433 47.453 47.473 23602370 47.473 47.493 47.513 2370

MAXIMUM TEMPERATURE RANGEThermocouple Grade– 450 to 2372°F– 270 to 1300°CExtension Grade32 to 392°F0 to 200°CLIMITS OF ERROR(whichever is greater)Standard: 2.2°C or 0.75% Above 0°C2.2°C or 2.0% Below 0°CSpecial: 1.1°C or 0.4%COMMENTS, BARE WIRE ENVIRONMENT:Alternative to Type K; More Stable at High TemperaturesTEMPERATURE IN DEGREES °F REFERENCE JUNCTION AT 32°FNN

ThermocoupleGrade



0.1% Magnesium

ExtensionGrade

+–

+–



Z-238

Z


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

0 0.000 0.013 0.026 0.040 0.053 0.067 0.080 0.094 0.107 0.121 0.135 010 0.135 0.148 0.162 0.176 0.189 0.203 0.217 0.231 0.244 0.258 0.272 1020 0.272 0.286 0.300 0.314 0.328 0.342 0.356 0.370 0.384 0.398 0.412 2030 0.412 0.426 0.440 0.454 0.469 0.483 0.497 0.511 0.525 0.540 0.554 040 0.554 0.568 0.583 0.597 0.612 0.626 0.640 0.655 0.669 0.684 0.698 40

50 0.698 0.713 0.727 0.742 0.757 0.771 0.786 0.801 0.815 0.830 0.845 5060 0.845 0.860 0.874 0.889 0.904 0.919 0.934 0.948 0.963 0.978 0.993 6070 0.993 1.008 1.023 1.038 1.053 1.068 1.083 1.098 1.114 1.129 1.144 7080 1.144 1.159 1.174 1.189 1.205 1.220 1.235 1.250 1.266 1.281 1.296 8090 1.296 1.312 1.327 1.342 1.358 1.373 1.389 1.404 1.420 1.435 1.451 90

100 1.451 1.466 1.482 1.497 1.513 1.529 1.544 1.560 1.576 1.591 1.607 100110 1.607 1.623 1.639 1.654 1.670 1.686 1.702 1.718 1.733 1.749 1.765 110120 1.765 1.781 1.797 1.813 1.829 1.845 1.861 1.877 1.893 1.909 1.925 120130 1.925 1.941 1.957 1.973 1.989 2.006 2.022 2.038 2.054 2.070 2.087 130140 2.087 2.103 2.119 2.135 2.152 2.168 2.184 2.201 2.217 2.233 2.250 140

150 2.250 2.266 2.283 2.299 2.316 2.332 2.349 2.365 2.382 2.398 2.415 150160 2.415 2.431 2.448 2.464 2.481 2.498 2.514 2.531 2.548 2.564 2.581 160170 2.581 2.598 2.614 2.631 2.648 2.665 2.682 2.698 2.715 2.732 2.749 170180 2.749 2.766 2.783 2.800 2.816 2.833 2.850 2.867 2.884 2.901 2.918 180190 2.918 2.935 2.952 2.969 2.986 3.003 3.020 3.038 3.055 3.072 3.089 190

200 3.089 3.106 3.123 3.140 3.158 3.175 3.192 3.209 3.227 3.244 3.26 200210 3.261 3.278 3.296 3.313 3.330 3.348 3.365 3.382 3.400 3.417 3.434 210220 3.434 3.452 3.469 3.487 3.504 3.522 3.539 3.557 3.574 3.592 3.609 220230 3.609 3.627 3.644 3.662 3.679 3.697 3.714 3.732 3.750 3.767 3.785 230240 3.785 3.803 3.820 3.838 3.856 3.873 3.891 3.909 3.927 3.944 3.962 240

250 3.962 3.980 3.998 4.015 4.033 4.051 4.069 4.087 4.104 4.122 4.140 250260 4.140 4.158 4.176 4.194 4.212 4.230 4.248 4.266 4.284 4.301 4.319 260270 4.319 4.337 4.355 4.373 4.391 4.410 4.428 4.446 4.464 4.482 4.500 270280 4.500 4.518 4.536 4.554 4.572 4.590 4.608 4.627 4.645 4.663 4.681 280290 4.681 4.699 4.717 4.736 4.754 4.772 4.790 4.809 4.827 4.845 4.863 290

300 4.863 4.882 4.900 4.918 4.937 4.955 4.973 4.992 5.010 5.028 5.047 300310 5.047 5.065 5.083 5.102 5.120 5.139 5.157 5.175 5.194 5.212 5.231 310320 5.231 5.249 5.268 5.286 5.305 5.323 5.342 5.360 5.379 5.397 5.416 320330 5.416 5.434 5.453 5.471 5.490 5.508 5.527 5.546 5.564 5.583 5.601 330340 5.601 5.620 5.639 5.657 5.676 5.695 5.713 5.732 5.751 5.769 5.788 340

350 5.788 5.807 5.825 5.844 5.863 5.882 5.900 5.919 5.938 5.956 5.975 350360 5.975 5.994 6.013 6.032 6.050 6.069 6.088 6.107 6.126 6.144 6.163 360370 6.163 6.182 6.201 6.220 6.239 6.257 6.276 6.295 6.314 6.333 6.352 370380 6.352 6.371 6.390 6.409 6.427 6.446 6.465 6.484 6.503 6.522 6.541 380390 6.541 6.560 6.579 6.598 6.617 6:636 6.655 6.674 6.693 6.712 6.731 390

400 6.731 6.750 6. 69 6.788 6.807 6.826 6.845 6.864 6.883 6.902 6.921 400410 6.921 6.940 6.959 6.979 6.998 7.017 7.036 7.055 7.074 7.093 7.112 410420 7.112 7.131 7.151 7.170 7.189 7.208 7.227 7.246 7.265 7.285 7.304 420430 7.304 7.323 7.342 7.361 7.380 7.400 7.419 7.438 7.457 7.476 7.496 430440 7.496 7.515 7.534 7.553 7.572 7.592 7.611 7.630 7.649 7.669 7.688 440

450 7.688 7.707 7.726 7.746 7.765 7.784 7.804 7.823 7.842 7.861 7.881 450460 7.881 7.900 7.919 7.939 7.958 7.977 7.996 8.016 8.035 8.054 8.074 460470 8.074 8.093 8.112 8.132 8.151 8.170 8.190 8.209 8.229 8.248 8.267 470480 8.267 8.287 8.306 8.325 8.345 8.364 8.383 8.403 8.422 8.422 8.461 480490 8.461 8.480 8.500 8.519 8.539 8.558 8.577 8.597 8.616 8.636 8.655 490

500 8.655 8.674 8.694 8.713 8.733 8.752 8.772 8.791 8.810 8.830 8.849 500510 8.849 8.869 8.888 8.908 8.927 8.947 8.966 8.986 9.005 9.024 9.044 510520 9.044 9.063 9.083 9.102 9.122 9.141 9.161 9.180 9.200 9.219 9.239 520530 9.239 9.258 9.278 9.297 9.317 9.336 9.356 9.375 9.395 9.414 9.434 530540 9.434 9.453 9.473 9.492 9.512 9.531 9.551 9.570 9.590 9.609 9.629 540

550 9.629 9.648 9.668 9.687 9.707 9.726 9.746 9.765 9.785 9.804 9.824 550560 9.824 9.843 9.863 9.883 9.902 9.922 9.941 9.961 9.980 10.000 10.019 560570 10.019 10.039 10.058 10.078 10.097 10.117 10.137 10.156 10.176 10.195 10.215 570580 10.215 10.234 10.254 10.273 10.293 10.312 10.332 10.352 10.371 10.391 10.410 580590 10.410 10.430 10.449 10.469 10.488 10.508 10.528 10.547 10.567 10.586 10.606 590

600 10.606 10-625 10.645 10.664 10.684 10.703 10.723 10.743 10.762 10.782 10.801 600610 10.801 10.821 10.840 10.860 10.879 10.899 10.919 10.938 10.958 10.977 10.997 610620 10.997 11.016 11.036 11.055 11.075 11.095 11.114 11.134 11.153 11.173 11.192 620630 11.192 11.212 11.231 11.251 11.270 11.290 11.310 11.329 11.349 11.368 11.388 630640 11.388 11.407 11.427 11.446 11.466 11.485 11.505 11.525 11.544 11.564 11.583 640

650 11.583 11.603 11.622 11.642 11.661 11.681 11.700 11.720 11.739 11.759 11.778 650660 11.778 11.798 11.817 11.837 11.857 11.876 11.896 11.915 11.935 11.954 11.974 660670 11.974 11.993 12.013 12.032 12.052 12.071 12.091 12.110 12.130 12.149 12.169 670680 12.169 12.188 12.208 12.227 12.247 12.266 12.286 12.305 12.325 12.344 12.364 680690 12.364 12.383 12.403 12.422 12.442 12.461 12.481 12.500 12-519 12.539 12.558 690

700 12.558 12.578 12.597 12.617 12.636 12.656 12.675 12.695 12.714 12.734 12.753 700710 12.753 12.772 12.792 12.811 12.831 12.850 12.870 12.889 12.909 12.928 12.947 710720 12.947 12.967 12.986 13.006 13.025 13.045 13.064 13.083 13.103 13.122 13.142 720730 13.142 13.161 13.180 13.200 13.219 13.239 13.258 13.277 13.297 13.316 13.336 730740 13.336 13.355 13.374 13.394 13.413 13.432 13.452 13.471 13.491 13.510 13.529 740

750 13.529 13.549 13.568 13.587 13.607 13.626 13.645 13.665 13.684 13.703 13.723 750760 13.723 13.742 13.761 13.781 13.800 13.819 13.839 13.858 13.877 13.897 13.916 760770 13.916 13.935 13.955 13.974 13.993 14.012 14.032 14.051 14 .070 14.090 14.109 770780 14.109 14.128 14.147 14.167 14.186 14.205 14.224 14.244 14.263 14.282 14.302 780790 14.302 14.321 14.340 14.359 14.378 14.398 14.417 14.436 14.455 14.475 14.494 790

800 14.494 14.513 14.532 14-551 14.571 14.590 14.609 14.628 14.647 14.667 14.686 800810 14.686 14.705 14.724 14.743 14.762 14.782 14.801 14.820 14.839 14.858 14.877 810820 14.877 14.897 14.916 14.935 14.954 14.973 14.992 15.011 15.030 15.050 15.069 820830 15.069 15.088 15.107 15.126 15.145 15.164 15.183 15.202 15.221 15.241 15.260 830840 15.260 15.279 15.298 15.317 15.336 15.355 15.374 15.393 15.412 15.431 15.450 840

850 15.450 15.469 15.488 15.507 15.526 15.545 15.564 15.583 15.602 15.621 15.640 850860 15.640 15.659 15.678 15.697 15.716 15.735 15.754 15.773 15.792 15.811 15.830 860870 15.830 15.849 15.868 15.887 15.906 15.925 15.944 15.963 15.982 16.001 16.020 870880 16.020 16.038 16.057 16.076 16.095 16.114 16.133 16.152 16.171 19.190 16.208 880890 16.208 16.227 16.246 16.265 16.284 16.303 16.322 16.340 16.359 16.378 16.397 890

900 16.397 16.416 16.435 16.453 16.472 16.491 16.510 16.529 16.547 16.566 16.585 900910 16.585 16.604 16.623 16.641 16.660 16.679 16.698 16.716 16.735 16.754 16.773 910920 16.773 16.791 16.810 16.829 16.848 16.866 16.885 16.904 16.923 16.941 16.960 920930 16.960 16.979 16.997 17.016 17.035 17.053 17.072 17.091 17.109 17.128 17.147 930940 17.147 17.165 17.184 17.203 17.221 17.240 17.258 17.277 17.296 17.314 17.333 940

950 17.333 17.352 17.370 17.389 17.407 17.426 17.444 17.463 17.482 17.500 17.519 950960 17.519 17.537 17.556 17.574 17.593 17.611 17.630 17.648 17.667 17.686 17.704 960970 17.704 17.723 17.741 17.760 17.778 17.796 17.815 17.833 17.852 17.870 17.889 970980 17.889 17.907 17.926 17.944 17.963 17.981 17.999 18.018 18.036 18.055 18.073 980990 18.073 18.092 18.110 18.128 18.147 18.165 18.184 18.202 18.220 18.239 18.257 990

MAXIMUM TEMPERATURE RANGEThermocouple Grade-32 to 4208°F-0 to 2320°CExtension Grade32 to 1600°F0 to 870°CLIMITS OF ERROR(whichever is greater)Standard: 4.5°C to 425°C1.0% to 2320°CSpecial: Not EstablishedCOMMENTS, BARE WIRE ENVIRONMENT:Vacuum, Inert; Hydrogen; Beware ofEmbrittlement; Not Practical Below 750°F;Not for Oxidizing AtmosphereTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°C CC

°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

ThermocoupleGrade

Tungsten-5% Rhenium

vs.Tungsten-

26% Rhenium

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-239


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

1000 18.257 18.275 18.294 18.312 18.330 18.349 18.367 18.385 18.404 18.422 18.440 10001010 18.440 18.459 18.477 18.495 18.513 18.532 18.550 18.568 18.587 18.605 18.623 10101020 18.623 18.641 18.660 18.678 18.696 18.714 18.732 18.751 18.769 18.787 18.805 10201030 18.805 18.824 18.842 18.860 18.878 18.896 18.914 18.933 18.951 18.969 18.987 10301040 18.987 19.005 19.023 19.041 19.060 19.078 19.096 19.114 19.132 19.150 19.168 1040

1050 19.168 19.186 19.204 19.223 19.241 19.259 19.277 19.295 19.313 19.331 19.349 10501060 19.349 19.367 19.385 19.403 19.421 19.439 19.457 19.475 19.493 19.511 19.529 10601070 19.529 19.547 19.565 19.583 19.601 19.619 19.637 19.655 19.673 19.691 19.709 10701080 19.709 19.727 19.744 19.762 19.780 19.798 19.816 19.834 19.852 19.870 19.888 10801090 19.888 19.905 19.923 19.941 19.959 19.977 19.995 20.013 20.030 20.048 20.066 1090

1100 20.066 20.084 20.102 20.120 20.137 20.155 20.173 20.191 20.208 20.226 20.066 11001110 20.244 20.262 20.279 20.297 20.315 20.333 20.350 20.368 20.386 20.404 20.421 11101120 20.421 20.439 20.457 20.474 20.492 20.510 20.527 20.545 20.563 20.580 20.598 11201130 20.598 20.616 20.633 20.651 20.669 20.686 20.704 20.721 20.739 20.757 20.774 11301140 20.774 20.792 20.809 20.827 20.845 20.862 20.880 20.897 20.915 20.932 20.950 1140

1150 20.950 20.967 20.985 21.002 21.020 21.037 21.055 21.072 21.090 21.107 21.125 11501160 21.125 21.142 21.160 21.177 21.195 21.212 21.230 21.247 21.265 21.282 21.299 11601170 21.299 21.317 21.334 21.352 21.369 21.386 21.404 21.421 21.439 21.456 21.473 11701180 21.473 21.491 21.508 21.525 21.543 21.560 21.577 21.595 21.612 21.629 21.647 11801190 21.647 21.664 21.681 21.698 21.716 21.733 21.750 21.768 21.785 21.802 21.819 1190

1200 21.819 21.837 21.854 21.871 21.888 21.905 21.923 21.940 21.957 21.974 21.991 12001210 21.991 22.009 22.026 22.043 22.060 22.077 22.094 22.112 22.129 22.146 22.163 12101220 22.163 22.180 22.197 22.214 22.231 22.249 22.266 22.283 22.300 22.317 22.334 12201230 22.334 22.35 22.368 22.385 22.402 22.419 22.436 22.453 22.470 22.487 22.504 12301240 22.504 22.521 22.538 22.555 22.572 22.589 22.606 22.623 22.640 22.657 22.674 1240

1250 22.674 22.691 22.708 22.725 22.742 22.759 22.776 22.792 22.809 22.826 22.843 12501260 22.843 22.860 22.877 22.894 22.911 22.928 22.944 22.961 22.978 22.995 23.012 12601270 23.012 23.029 23.045 23.062 23.079 23.096 23.113 23.129 23.146 23.163 23.180 12701280 23.180 23.196 23.213 23.230 23.247 23.263 23.280 23.297 23.314 23.330 23.347 12801290 23.347 23.364 23.380 23.397 23.414 23.431 23.447 23.464 23.481 23.497 23.514 1290

1300 23.514 23.530 23.547 23.564 23.580 23.597 23.614 23.630 23.647 23.663 23.680 13001310 23.680 23.697 23.713 23.730 23.746 23.763 23.779 23.796 23.812 23.829 23.846 13101320 23.846 23.862 23.879 23.895 23.912 23.928 23.945 23.961 23.978 23.994 24.010 13201330 24.010 24.027 24.043 24.060 24.076 24.093 24.109 24.126 24.142 24.158 24.175 13301340 24.175 24.191 24.208 24.224 24.240 24.257 24.273 24.290 24.306 24.322 24.339 1340

1350 24.339 24.355 24.371 24.388 24.404 24.420 24.437 24.453 24.46 24.485 24.502 13501360 24.502 24.518 24.534 24.551 24.567 24.583 24.599 24.616 24.632 24.648 24.664 13601370 24.664 24.680 24.697 24.713 24.729 24.745 24.762 24.778 24.794 24.810 24.826 13701380 24.826 24.842 24.859 24.875 24.891 24.907 24.923 24.939 24.955 24.971 24.988 13801390 24.988 25.004 25.020 25.036 25.052 25.068 25.084 25.100 25.116 24.132 25.148 1390

1400 25.148 25.164 25.180 25.196 25.212 25.228 25.244 25.260 25.276 25.292 25.308 14001410 25.308 25.324 25.340 25.356 25.372 25.388 25.404 25.420 25.436 25.452 25.468 14101420 25.468 25.484 25.500 25.516 25.532 25.547 25.563 25.579 25.595 25.611 25.627 14201430 25.627 25.643 25.658 25.674 25.690 25.706 25.722 25.738 25.753 25.769 25.785 14301440 25.785 25.801 25.817 25.832 25.848 25.864 25.880 25.896 25.911 25.927 25.943 1440

1450 25.943 25.959 25.974 25.990 26.006 26.021 26.037 26.053 26.069 26.084 26.100 14501460 26.100 26.116 26.131 26.147 26.163 26.178 26.194 26.209 26.225 26.241 26.256 14601470 26.256 26.272 26.288 26.303 26.319 26.334 26.350 26.366 26.381 26.397 26.412 14701480 26.412 26.428 26.443 26.459 26.474 26.490 26.505 26.521 26.537 26.552 26.568 14801490 26.568 26.583 26.599 26.614 26.629 26.645 26.660 26.676 26.691 26.707 26.722 1490

1500 26.722 26.738 26.753 26.768 26.784 26.799 26.815 26.830 26.845 26.861 26.876 15001510 26.876 26.892 26.907 26.922 26.938 26.953 26.968 26.984 26.999 27.014 27.030 15101520 27.030 27.045 27.060 27.076 27.091 27.106 27.121 27.137 27.152 27.167 27.183 15201530 27.183 27.198 27.213 27.228 27.244 27.259 27.274 27.289 27.304 27.320 27.335 15301540 27.335 27.350 27.365 27.380 27.396 27.411 27.426 27.441 27.456 27.471 27.486 1540

1550 27.486 27.502 27.517 27.532 27.547 27.562 27.577 27.592 27.607 27.622 27.637 15501560 27.637 27.653 27.668 27.683 27.698 27.713 27.728 27.743 27.758 27.773 27.788 15601570 27.788 27.803 27.818 27.833 27.848 27.863 27.878 27.893 27.908 27.923 27.938 15701580 27.938 27.953 27.968 27.983 27.997 28.012 28.027 28.042 28.057 28.072 28.087 15801590 28.087 28.102 28.117 28.132 28.146 28.161 28.176 28.191 28.206 28.221 28.236 1590

1600 28.236 28.250 28.265 28.280 28.295 28.310 28.324 28.339 28.354 28.369 28.531 16001610 28.531 28.398 28.413 28.428 28.443 28.457 28.472 28.487 28.502 28.516 28.531 16101620 28.531 28.546 28.560 28.575 28.590 28.604 28.619 28.634 28.648 28.663 28.678 16201630 28.678 28.692 28.707 28.722 28.736 28.751 28.765 28.780 28.795 28.809 28.824 16301640 28.824 28.838 28.853 28.868 28.882 28.897 28.911 28.926 28.940 28.955 28.969 1640

1650 28.969 28.984 28.998 29.013 29.027 29.042 29.056 29.071 29.085 29.100 29.114 16501660 29.114 29.129 29.143 29.158 29.172 29.187 29.201 29.215 29.230 29.244 29.259 16601670 29.259 29.273 29.287 29.302 29.316 29.331 29.345 29.359 29.374 29.388 29.402 16701680 29.402 29.417 29.431 29.445 29.460 29.474 29.488 29.503 29.517 29.531 29.546 16801690 29.546 29.560 29.574 29.588 29.603 29.617 29.631 29.645 29.660 29.674 29.688 1690

1700 29.688 29.702 29.716 29.731 29.745 29.759 29.773 29.787 29.802 29.816 29.830 17001710 29.830 29.844 29.858 29.872 29.886 29.901 29.915 29.929 29.943 29.957 29.971 17101720 29.971 29.985 29.999 30.013 30.027 30.041 30.056 30.070 30.084 30.098 30.112 17201730 30.112 30.126 30.140 30.154 30.168 30.182 30.196 30.210 30.224 30.238 30.252 17301740 30.252 30.266 30.280 30.294 30.308 30.321 30.335 30.349 30.363 30.377 30.391 1740

1750 30.391 30.405 30.419 30.433 30.447 30.460 30.474 30.488 30.502 30.516 30.530 17501760 30.530 30.544 30.557 30.571 30.585 30.599 30.613 30.627 20.640 30.654 30.668 17601770 30.668 30.682 30.695 30.709 30.723 30.737 30.750 30.764 30.778 30.792 30.805 17701780 30.805 30.819 30.833 30.846 30.860 30.874 30.887 30.901 30.915 20.928 30.942 17801790 30.942 30.956 30.969 30.983 30.997 31.010 31.024 31.038 31.051 31.065 31.078 1790

1800 31.078 31.092 31.105 31.119 31.133 31.146 31.160 31.173 31.187 31.200 31.214 18001810 31.214 31.227 31.241 31.254 31.268 31.281 31.295 31.308 31.322 31.335 31.349 18101820 31.349 31.362 31.376 31.389 31.403 31.416 31.429 31.443 31.456 31.470 31.483 18201830 31.483 31.496 31.510 31.523 31.536 31.550 31.563 31.577 31.590 31.603 31.617 18301840 31.617 31.630 31.643 31.656 31.670 31.683 31.696 31.710 31.723 31.736 31.749 1840

1850 31.749 31.763 31.776 31.789 31.802 31.816 31.829 31.842 31.855 31.869 31.882 18501860 31.882 31.895 31.908 31.921 31.934 31.948 31.961 31.974 31.987 32.000 32.013 18601870 32.013 32.026 32.040 32.053 32.066 32.079 32.092 32.105 32.118 32.131 32.144 18701880 32.144 32.157 32.170 31.183 32.196 32.209 32.222 32.235 32.248 32.261 32.274 18801890 32.274 32.287 32.300 31.313 32.326 32.339 32.352 32.365 32.378 32.391 32.404 1890

1900 32.404 32.417 32.430 32.443 32.456 32.468 32.481 32.494 32.507 32.520 32.533 19001910 32.533 32.546 32.558 32.571 32.584 32.597 32.610 32.623 32.635 32.648 32.661 19101920 32.661 32.674 32.686 32.699 32.712 32.725 32.737 32.750 32.763 32.776 32.788 19201930 32.788 32.801 32.814 32.826 32.839 32.852 32.864 32.877 32.890 32.902 32.915 19301940 32.915 32.928 32.940 32.953 32.966 32.978 32.991 33.003 33.016 33.028 33.041 1940

1950 33.041 33.054 33.066 33.079 33.091 33.104 33.116 33.129 33.141 33.154 33.166 19501960 33.166 33.179 33.191 33.204 33.216 33.229 33.241 33.254 33.266 33.278 33.291 19601970 33.291 33.303 33.316 33.328 33.341 33.353 33.365 33.378 33.390 33.402 33.415 19701980 33.415 33.427 33.439 33.452 33.464 33.476 33.489 33.501 33.513 33.525 33.538 19801990 33.538 33.550 33.562 33.575 33.587 33.599 33.611 33.623 33.636 33.648 33.660 1990

MAXIMUM TEMPERATURE RANGEThermocouple Grade-32 to 4208°F-0 to 2320°CExtension Grade32 to 1600°F0 to 870°CLIMITS OF ERROR(whichever is greater)Standard: 4.5°C to 425°C1.0% to 2320°CSpecial: Not EstablishedCOMMENTS, BARE WIRE ENVIRONMENT:Vacuum, Inert; Hydrogen; Beware ofEmbrittlement; Not Practical Below 750°F;Not for Oxidizing AtmosphereTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°CCC

ThermocoupleGrade

Tungsten-5% Rhenium

vs.Tungsten-

26% Rhenium

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-240

Z


°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

2000 33.660 33.672 33.684 33.697 33.709 33.721 33.733 33.745 33.757 33.769 33.782 20002010 33.782 33.794 33.806 33.818 33.830 33.842 33.854 33.866 33.878 33.890 33.902 20102020 33.902 33.914 33.926 33.938 33.950 33.962 33.974 33.986 33.998 34.010 34.022 20202030 34.022 34.034 34.046 34.058 34.070 34.082 34.094 34.106 34.118 34.130 34.142 20302040 34.142 34.153 34.165 34.177 34.189 34.201 34.213 34.225 34.236 34.248 34.260 2040

2050 34.260 34.272 34.284 34.295 34.307 34.319 34.331 34.342 34.354 34.366 34.378 20502060 34.378 34.389 34.401 34.413 34.424 34.436 34.448 34.459 34.471 34.483 34.494 20602070 34.494 34.506 34.518 34.529 34.541 34.552 34.564 34.576 34.587 34.599 34.610 20702080 34.610 34.622 34.633 34.645 34.656 34.668 34.679 34.691 34.702 34.714 34.725 20802090 34.725 34.737 34.748 34.760 34.771 34.782 34.794 34.805 34.817 34.828 34.839 2090

2100 34.839 34.851 34.862 34.874 34.885 34.896 34.908 34.919 34.930 34.942 34.953 21002110 34.953 34.964 34.975 34.987 34.998 35.009 35.020 35.032 35.043 35.054 35.065 21102120 35.065 35.077 35.088 35.099 35.110 35.121 35.132 34.144 35.155 35.166 35.177 21202130 35.177 35.188 35.199 35.210 35.221 35.232 35.243 35.254 35.265 35.277 35.288 21302140 35.288 35.299 35.310 35.321 35.332 35.343 35.353 35.364 35.375 35.386 35.397 2140

2150 35.397 35.408 35.419 35.430 35.441 35.452 35.463 35.474 35.484 35.495 35.506 21502160 35.506 35.517 35.528 35.539 35.549 35.560 35.571 35.582 35.592 35.603 35.614 21602170 35.614 35.625 35.635 35.646 35.657 35.668 35.678 35.689 35.700 35.710 35.721 21702180 35.721 35.731 35.742 35.753 35.763 35.774 35.784 35.795 35.806 35.816 35.827 21802190 35.827 35.837 35.848 35.858 35.869 35.879 35.890 35.900 35.911 35.921 35.932 2190

2200 35.932 35.942 35.953 35.963 35.973 35.984 35.994 36.004 36.015 36.025 36.036 22002210 36.036 36.046 36-056 36.067 36.077 36.087 36.097 36.108 36.118 36.128 36.138 22102220 36.138 36.149 36.159 36.169 36.179 36.189 36.200 36.210 36.220 36.230 36.240 22202230 36.240 36.250 36.260 36.271 36.281 36.291 36.301 36.311 36.321 36.331 36.341 22302240 36.341 36.351 36.361 36.371 36.381 36.391 36.401 36.411 36.421 36.431 36.441 2240

2250 36.441 36.451 36.460 36.470 36.480 36.490 36-500 36.510 36.520 36.529 36.539 22502260 36.539 36.549 36.559 36.569 36.578 36.588 36.598 36.608 36.617 36.627 36.637 22602270 36.637 36.646 36.656 36.666 36.675 36.685 36.695 36.704 36.714 36.723 36.733 22702280 36.733 36.743 36.752 36.762 36.771 36.781 36.790 36.800 36.809 36.819 36.828 22802290 36.828 36.838 36.847 36.857 36.866 36.875 36.885 36.894 36.903 36.913 36.922 2290

2300 36.922 36.932 36.941 36.950 36.959 36.969 36.978 36.987 36.997 37.006 37.015 23002310 37.015 37.024 37.033 37.043 37.052 37.061 37.070 37.079 37.088 37.097 37.107 2310

MAXIMUM TEMPERATURE RANGEThermocouple Grade-32 to 4208°F-0 to 2320°CExtension Grade32 to 1600°F0 to 870°CLIMITS OF ERROR(whichever is greater)Standard: 4.5°C to 425°C1.0% to 2320°CSpecial: Not EstablishedCOMMENTS, BARE WIRE ENVIRONMENT:Vacuum, Inert; Hydrogen; Beware ofEmbrittlement; Not Practical Below 750°F;Not for Oxidizing AtmosphereTEMPERATURE IN DEGREES °CREFERENCE JUNCTION AT 0°C CC

°C 0 1 2 3 4 5 6 7 8 9 10 °C °C 0 1 2 3 4 5 6 7 8 9 10 °C

ThermocoupleGrade

Tungsten-5% Rhenium

vs.Tungsten-

26% Rhenium

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-241


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

0 -0.234 -0.227 -0.220 -0.213 -0.206 -0.198 -0.191 -0.184 -0.177 -0.169 -0.162 010 -0.162 -0.155 -0.148 -0.140 -0.133 -0.126 -0.118 -0.111 -0.104 -0.096 -0.089 1020 -0.089 -0.082 -0.074 -0.067 -0.060 -0.052 -0.045 -0.037 -0.030 -0.023 -0.015 2030 -0.015 -0.008 0.000 0.007 0.014 0.022 0.029 0.037 0.044 0.052 0.059 3040 0.059 0.067 0.074 0.082 0.089 0.097 0.104 0.112 0.120 0.127 0.135 40

50 0.135 0.142 0.150 0.157 0.165 0.173 0.180 0.188 0.196 0.203 0.211 5060 0.211 0.218 0.226 0.234 0.241 0.249 0.257 0.264 0.272 0.280 0.288 6070 0.288 0.295 0.303 0.311 0.319 0.326 0.334 0.342 0.350 0.357 0.365 7080 0.365 0.373 0.381 0.389 0.396 0.404 0.412 0.420 0.428 0.436 0.443 8090 0.443 0.451 0.459 0.467 0.475 0.483 0.491 0.499 0.506 0.514 0.522 90

100 0.522 0.530 0.538 0.546 0.554 0.562 0.570 0.578 0.586 0.594 0.522 100110 0.602 0.610 0.618 0.626 0.634 0.642 0.650 0.658 0.666 0.674 0.682 10120 0.682 0.690 0.698 0.706 0.714 0.723 0.731 0.739 0.747 0.755 0.763 120130 0.763 0.771 0.779 0.788 0.796 0.804 0.812 0.820 0.828 0.837 0.845 130140 0.845 0.853 0.861 0.869 0.878 0.886 0.894 0.902 0.911 0.919 0.927 140

150 0.927 0.935 0.944 0.952 0.960 0.968 0.977 0.985 0.993 1.002 1.010 150160 1.010 1.018 1.027 1.035 1.043 1.052 1.060 1.068 1.077 1.085 1.093 160170 1.093 1.102 1.110 1.119 1.127 1.135 1.144 1.152 1.161 1.169 1.178 170180 1.178 1.186 1.194 1.203 1.211 1.220 1.228 1.237 1.245 1.254 1.262 180190 1.262 1.271 1.279 1.288 1.296 1.305 1.313 1.322 1.330 1.339 1.348 190

200 1.348 1.356 1.365 1.373 1.382 1.390 1.399 1.408 1.416 1.425 1.434 200210 1.434 1.442 1.451 1.459 1.468 1.477 1.485 1.494 1.503 1.511 1.520 210220 1.520 1.529 1.537 1.546 1.555 1.563 1.572 1.581 1.590 1.598 1.607 220230 1.607 1.616 1.625 1.633 1.642 1.651 1.660 1.668 1.677 1.686 1.695 230240 1.695 1.703 1.712 1.721 1.730 1.739 1.748 1.756 1.765 1.774 1.783 240

250 1.783 1.792 1.801 1.809 1.818 1.827 1.836 1.845 1.854 1.863 1.872 250260 1.872 1.880 1.889 1.898 1.907 1.916 1.925 1.934 1.943 1.952 1.961 260270 1.961 1.970 1.979 1.988 1.997 2.006 2.015 2.024 2.033 2.042 2.051 270280 2.051 2.060 2.069 2.078 2.087 2.096 2.105 2.114 2.123 2.132 2.141 280290 2.141 2.150 2.159 2.168 2.177 2.186 2.195 2.204 2.213 2.223 2.232 290

300 2.232 2.241 2.250 2.259 2.268 2.277 2.286 2.295 2.305 2.314 2.323 300310 2.323 2.332 2.341 2.350 2.360 2.369 2.378 2.387 2.396 2.405 2.415 310320 2.415 2.424 2.433 2.442 2.451 2.461 2.470 2.479 2.488 2.498 2.507 320330 2.507 2.516 2.525 2.535 2.544 2.553 2.562 2.572 2.581 2.590 2.600 330340 2.600 2.609 2.618 2.628 2.637 2.646 2.655 2.665 2.674 2.683 2.693 340

350 2.693 2.702 2.711 2.721 2.730 2.740 2.749 2.758 2.768 2.777 2.786 350360 2.786 2.796 2.805 2.815 2.824 2.833 2.843 2.852 2.862 2.871 2.880 360370 2.880 2.890 2.899 2.909 2.918 2.928 2.937 2.947 2.956 2.965 2.975 370380 2.975 2.984 2.994 3.003 3.013 3.022 3.032 3.041 3.051 3.060 3.070 380390 3.070 3.079 3.089 3.098 3.108 3.118 3.127 3.137 3.146 3.156 3.165 390

400 3.165 3.175 3.184 3.194 3.204 3.213 3.223 3.232 3.242 3.251 3.261 400410 3.261 3.271 3.280 3.290 3.299 3.309 3.319 3.328 3.338 3.348 3.357 410420 3.357 3.367 3.376 3.386 3.396 3.405 3.415 3.425 3.434 3.444 3.454 420430 3.454 3.463 3.473 3.483 3.492 3.502 3.512 3.522 3.531 3.541 3.551 430440 3.551 3.560 3.570 3.580 3.590 3.599 3.609 3.619 3.629 3.638 3.648 440

450 3.648 3.658 3.668 3.677 3.687 3.697 3.707 3.716 3.726 3.736 3.746 450460 3.746 3.756 3.765 3.775 3.785 3.795 3.805 3.814 3.824 3.834 3.844 460470 3.844 3.854 3.864 3.873 3.883 3.893 3.903 3.913 3.923 3.932 3.942 470480 3.942 3.952 3.962 3.972 3.982 3.992 4.002 4.011 4.021 4.031 4.041 480490 4.041 4.051 4.061 4.071 4.081 4.091 4.101 4.110 4.120 4.130 4.140 490

500 4.140 4.150 4.160 4.170 4.180 4.190 4.200 4.210 4.220 4.230 4.240 500510 4.240 4.250 4.260 4.270 4.280 4.290 4.299 4.309 4.319 4.329 4.339 510520 4.339 4.349 4.359 4.369 4.379 4.389 4.399 4.410 4.420 4.430 4.440 520530 4.440 4.450 4.460 4.470 4.480 4.490 4.500 4.510 4.520 4.530 4.540 530540 4.540 4.550 4.560 4.570 4.580 4.590 4.600 4.610 4.621 4.631 4.641 540

550 4.641 4.651 4.661 4.671 4.681 4.691 4.701 4.711 4.722 4.732 4.742 550560 4.742 4.752 4.762 4.772 4.782 4.792 4.803 4.813 4.823 4.833 4.843 560570 4.843 4.853 4.863 4.874 4.884 4.894 4.904 4.914 4.924 4.935 4.945 570580 4.945 4.955 4.965 4.975 4.985 4.996 5.006 5.016 5.026 5.036 5.047 580590 5.047 5.057 5.067 5.077 5.087 5.098 5.108 5.118 5.128 5.139 5.149 590

600 5.149 5.159 5.169 5.180 5.190 5.200 5.210 5.220 5.231 5.241 5.251 600610 5.251 5.261 5.272 5.282 5.292 5.303 5.313 5.323 5.333 5.344 5.354 610620 5.354 5.364 5.375 5.385 5.395 5.405 5.416 5.426 5.436 5.447 5.457 620630 5.457 5.467 5.478 5.488 5.498 5.508 5.519 5.529 5.539 5.550 5.560 630640 5.560 5.570 5.581 5.591 5.601 5.612 5.622 5.632 5.643 5.653 5.664 640

650 5.664 5.674 5.684 5.695 5.705 5.715 5.726 5.736 5.746 5.757 5.767 650660 5.767 5.778 5.788 5.798 5.809 5.819 5.830 5.840 5.850 5.861 5.871 660670 5.871 5.882 5.892 5.902 5.913 5.923 5.934 5.944 5.954 5.965 5.975 670680 5.975 5.986 5.996 6.007 6.017 6.027 6.038 6.048 6.059 6.069 6.080 680690 6.080 6.090 6.100 6.111 6.121 6.132 6.142 6.153 6.163 6.174 6.184 690

700 6.184 6.195 6.205 6.216 6.226 6.236 6.247 6.257 6.268 6.278 6.289 700710 6.289 6.299 6.310 6.320 6.331 6.341 6.352 6.362 6.373 6.383 6.394 710720 6.394 6.404 6.415 6.425 6.436 6.446 6.457 6.467 6.478 6.488 6.499 720730 6.499 6.509 6.520 6.531 6.541 6.552 6.562 6.573 6.583 6.594 6.604 730740 6.604 6.615 6.625 6.636 6.646 6.657 6.668 6.678 6.689 6.699 6.710 740

750 6.710 6.720 6.731 6.741 6.752 6.763 6.773 6.784 6.794 6.805 6.815 750760 6.815 6.826 6.837 6.847 6.858 6.868 6.879 6.890 6.900 6.911 6.921 760770 6.921 6.932 6.943 6.953 6.964 6.974 6.985 6.996 7.006 7.017 7.027 770780 7.027 7.038 7.049 7.059 7.070 7.080 7.091 7.102 7.112 7.123 7.134 780790 7.134 7.144 7.155 7.165 7.176 7.187 7.197 7.208 7.219 7.229 7.240 790

800 7.240 7.250 7.261 7.272 7.282 7.293 7.304 7.314 7.325 7.336 7.346 800810 7.346 7.357 7.368 7.378 7.389 7.400 7.410 7.421 7.432 7.442 7.453 810820 7.453 7.464 7.474 7.485 7.496 7.506 7.517 7.528 7.538 7.549 7.560 820830 7.560 7.570 7.581 7.592 7.602 7.613 7.624 7.634 7.645 7.656 7.667 830840 7.667 7.677 7.688 7.699 7.709 7.720 7.731 7.741 7.752 7.763 7.774 840

850 7.774 7.784 7.795 7.806 7.816 7.827 7.838 7.849 7.859 7.870 7.881 850860 7.881 7.891 7.902 7.913 7.924 7.934 7.945 7.956 7.966 7.977 7.988 860870 7.988 7.999 8.009 8.020 8.031 8.042 8.052 8.063 8.074 8.085 8.095 870880 8.095 8.106 8.117 8.127 8.138 8.149 8.160 8.170 8.181 8.192 8.203 880890 8.203 8.213 8.224 8.235 8.246 8.256 8.267 8.278 8.289 8.300 8.310 890

900 8.310 8.321 8.332 8.343 8.353 8.364 8.375 8.386 8.396 8.407 8.418 900910 8.418 8.429 8.439 8.450 8.461 8.472 8.483 8.493 8.504 8.515 8.526 910920 8.526 8.536 8.547 8.558 8.569 8.580 8.590 8.601 8.612 8.623 8.633 920930 8.633 8.644 8.655 8.666 8.677 8.687 8.698 8.709 8.720 8.731 8.741 930940 8.741 8.752 8.763 8.774 8.785 8.795 8.806 8.817 8.828 8.839 8.849 940

950 8.849 8.860 8.871 8.882 8.893 8.903 8.914 8.925 8.936 8.947 8.957 950960 8.957 8.968 8.979 8.990 9.001 9.011 9.022 9.033 9.044 9.055 9.066 960970 9.066 9.076 9.087 9.098 9.109 9.120 9.130 9.141 9.152 9.163 9.174 970980 9.174 9.185 9.195 9.206 9.217 9.228 9.239 9.250 9.260 9.271 9.282 980990 9.282 9.293 9.304 9.314 9.325 9.336 9.347 9.358 9.369 9.379 9.390 990

MAXIMUM TEMPERATURE RANGEThermocouple Grade-32 to 4208°F-0 to 2320°CExtension Grade32 to 1600°F0 to 870°CLIMITS OF ERROR(whichever is greater)Standard: 4.5°C to 425°C1.0% to 2320°CSpecial: Not EstablishedCOMMENTS, BARE WIRE ENVIRONMENT:Vacuum, Inert; Hydrogen; Beware ofEmbrittlement; Not Practical Below 750°F;Not for Oxidizing AtmosphereTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°FCC

ThermocoupleGrade

Tungsten-5% Rhenium

vs.Tungsten-

26% Rhenium

ExtensionGrade

+–

+–



Z-242

Z


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

1000 9.390 9.401 9.412 9.423 9.434 9.444 9.455 9.466 9.477 9.488 9.499 10001010 9.499 9.509 9.520 9.531 9.542 9.553 9.564 9.575 9.585 9.596 9.607 10101020 9.607 9.618 9.629 9.640 9.650 9.661 9.672 9.683 9.694 9.705 9.715 10201030 9.715 9.726 9.737 9.748 9.759 9.770 9.781 9.791 9.802 9.813 9.824 10301040 9.824 9.835 9.846 9.857 9.867 9.878 9.889 9.900 9.911 9.922 9.932 1040

1050 9.932 9.943 9.954 9.965 9.976 9.987 9.998 10.008 10.019 10.030 9.932 10501060 10.041 10.052 10.063 10.074 10.084 10.095 10.106 10.117 10.128 10.139 10.150 10601070 10.150 10.160 10.171 10.182 10.193 10.204 10.215 10.226 10.236 10.247 10.258 10701080 10.258 10.269 10.280 10.291 10.302 10.312 10.323 10.334 10.345 10.356 10.367 10801090 10.367 10.378 10.388 10.399 10.410 10.421 10.432 10.443 10.454 10.464 10.475 1090

1100 10.475 10.486 10.497 10.508 10.519 10.530 10.541 10.551 10.562 10.573 10.584 11001110 10.584 10.595 10.606 10.617 10.627 10.638 10.649 10.660 10.671 10.682 10.693 11101120 10.693 10.703 10.714 10.725 10.736 10.747 10.758 10.769 10.780 10.790 10.801 11201130 10.801 10.812 10.823 10.834 10.845 10.856 10.866 10.877 10.888 10.899 10.910 11301140 10.910 10.921 10.932 10.942 10.953 10.964 10.975 10.986 10.997 11.008 11.019 1140

1150 11.019 11.029 11.040 11.051 11.062 11.073 11.084 11.095 11.105 11.116 11.127 11501160 11.127 11.138 11.149 11.160 11.171 11.181 11.192 11.203 11.214 11.225 11.236 11601170 11.236 11.247 11.257 11.268 11.279 11.290 11.301 11.312 11.323 11.333 11.344 11701180 11.344 11.355 11.366 11.377 11.388 11.399 11.409 11.420 11.431 11.442 11.453 11801190 11.453 11.464 11.475 11.485 11.496 11.507 11.518 11.529 11.540 11.551 11.561 1190

1200 11.561 11.572 11.583 11.594 11.605 11.616 11.627 11.637 11.648 11.659 11.670 12001210 11.670 11.681 11.692 11.702 11.713 11.724 11.735 11.746 11.757 11.768 11.778 12101220 11.778 11.789 11.800 11.811 11.822 11.833 11.844 11.854 11.865 11.876 11.887 12201230 11.887 11.898 11.909 11.919 11.930 11.941 11.952 11.963 11.974 11.984 11.995 12301240 11.995 12.006 12.017 12.028 12.039 12.050 12.060 12.071 12.082 12.093 12.104 1240

1250 12.104 12.115 12.125 12.136 12.147 12.158 12.169 12.180 12.190 12.201 12.212 12501260 12.212 12.223 12.234 12.245 12.255 12.266 12.277 12.288 12.299 12.310 12.320 12601270 12.320 12.331 12.342 12.353 12.364 12.374 12.385 12.396 12.407 12.418 12.429 12701280 12.429 12.439 12.450 12.461 12.472 12.483 12.494 12.504 12.515 12.526 12.537 12801290 12.537 12.548 12.558 12.569 12.580 12.591 12.602 12.612 12.623 12.634 12.645 1290

1300 12.645 12.656 12.667 12.677 12.688 12.699 12.710 12.721 12.731 12.742 12.753 13001310 12.753 12.764 12.775 12.785 12.796 12.807 12.818 12.829 12.839 12.850 12.861 13101320 12.861 12.872 12.883 12.893 12.904 12.915 12.926 12.937 12.947 12.958 12.969 13201330 12.969 12.980 12.991 13.001 13.012 13.023 13.034 13.045 13.055 13.066 13.077 13301340 13.077 13.088 13.098 13.109 13.120 13.131 13.142 13.152 13.163 13.174 13.185 1340

1350 13.185 13.196 13.206 13.217 13.228 13.239 13.249 13.260 13.271 13.282 13.292 13501360 13.292 13.303 13.314 13.325 13.336 13.346 13.357 13.368 13.379 13.389 13.400 13601370 13.400 13.411 13.422 13.432 13.443 13.454 13.465 13.476 13.486 13.497 13.508 13701380 13.508 13.519 13.529 13.540 13.551 13.562 13.572 13.583 13.594 13.605 13.615 13801390 13.615 13.626 13.637 13.648 13.658 13.669 13.680 13.691 13.701 13.712 13.723 1390

1400 13.723 13.734 13.744 13.755 13.766 13.776 13.787 13.798 13.809 13.819 13.830 14001410 13.830 13.841 13.852 13.862 13.873 13.884 13.895 13.905 13.916 13.927 13.937 14101420 13.937 13.948 13.959 13.970 13.980 13.991 14.002 14.012 14.023 14.034 14.045 14201430 14.045 14.055 14.066 14.077 14.087 14.098 14.109 14.120 14.130 14.141 14.152 14301440 14.152 14.162 14.173 14.184 14.195 14.205 14.216 14.227 14.237 14.248 14.259 1440

1450 14.259 14.269 14.280 14.291 14.302 14.312 14.323 14.334 14.344 14.355 14.366 14501460 14.366 14.376 14.387 14.398 14.408 14.419 14.430 14.440 14.451 14.462 14.472 14601470 14.472 14.483 14.494 14.504 14.515 14.526 14.536 14.547 14.558 14.569 14.579 14701480 14.579 14.590 14.601 14.611 14.622 14.632 14.643 14.654 14.664 14.675 14.686 14801490 14.686 14.696 14.707 14.718 14.728 14.739 14.750 14.760 14.771 14.782 14.792 1490

1500 14.792 14.803 14.814 14.824 14.835 14.846 14.856 14.867 14.877 14.888 14.899 15001510 14.899 14.909 14.920 14.931 14.941 14.952 14.962 14.973 14.984 14.994 15.005 15101520 15.005 15.016 15.026 15.037 15.047 15.058 15.069 15.079 15.090 15.101 15.111 15201530 15.111 15.122 15.132 15.143 15.154 15.164 15.175 15.185 15.196 15.207 15.217 15301540 15.217 15.228 15.238 15.249 15.260 15.270 15.281 15.291 15.302 15.313 15.323 1540

1550 15.323 15.334 15.344 15.355 15.366 15.376 15.387 15.397 15.408 15.418 15.429 15501560 15.429 15.440 15.450 15.461 15.471 15.482 15.492 15.503 15.514 15.524 15.535 15601570 15.535 15.545 15.556 15.566 15.577 15.588 15.598 15.609 15.619 15.630 15.640 15701580 15.640 15.651 15.661 15.672 15.683 15.693 15.704 15.714 15.725 15.735 15.746 15801590 15.746 15.756 15.767 15.777 15.788 15.799 15.809 15.820 15.830 15.841 15.851 1590

1600 15.851 15.862 15.872 15.883 15.893 15.904 15.914 15.925 15.935 15.946 15.956 16001610 15.956 15.967 15.977 15.988 15.998 16.009 16.020 16.030 16.041 16.051 16.062 16101620 16.062 16.072 16.083 16.093 16.104 16.114 16.125 16.135 16.146 16.156 16.167 16201630 16.167 16.177 16.187 16.198 16.208 16.219 16.229 16.240 16.250 16.261 16.271 16301640 16.271 16.282 16.292 16.303 16.313 16.324 16.334 16.345 16.355 16.366 16.376 1640

1650 16.376 16.387 16.397 16.407 16.418 16.428 16.439 16.449 16.460 16.470 16.481 16501660 16.481 16.491 16.502 16.512 16.522 16.533 16.543 16.554 16.564 16.575 16.585 16601670 16.585 16.596 16.606 16.616 16.627 16.637 16.648 16.658 16.669 16.679 16.689 16701680 16.689 16.700 16.710 16.721 16.731 16.741 16.752 16.762 16.773 16.783 16.794 16801690 16.794 16.804 16.814 16.825 16.835 16.846 16.856 16.866 16.877 16.887 16.898 1690

1700 16.898 16.908 16.918 16.929 16.939 16.950 16.960 16.970 16.981 16.991 17.001 17001710 17.001 17.012 17.022 17.033 17.043 17.053 17.064 17.074 17.084 17.095 17.105 17101720 17.105 17.116 17.126 17.136 17.147 17.157 17.167 17.178 17.188 17.198 17.209 17201730 17.209 17.219 17.230 17.240 17.250 17.261 17.271 17.281 17.292 17.302 17.312 17301740 17.312 17.323 17.333 17.343 17.35 17.364 17.374 17.385 17.395 17.405 17.416 1740

1750 17.416 17.426 17.436 17.447 17.457 17.467 17.477 17.488 17.498 17.508 17.519 17501760 17.519 17.529 17.539 17.550 17.560 17.570 17.581 17.591 17.601 17.611 17.622 17601770 17.622 17.632 17.642 17.653 17.663 17.673 17.683 17.694 17.704 17.714 17.725 17701780 17.725 17.735 17.745 17.755 17.766 17.776 17.786 17.796 17.807 17.817 17.827 17801790 17.827 17.838 17.848 17.858 17.868 17.879 17.889 17.899 17.909 17.920 17.930 1790

1800 17.930 17.940 17.950 17.961 17.971 17.981 17.991 18.002 18.012 18.022 18.032 18001810 18.032 18.042 18.053 18.063 18.073 18.083 18.094 18.104 18.114 18.124 18.134 18101820 18.134 18.145 18.155 18.165 18.175 18.186 18.196 18.206 18.216 18.226 18.237 18201830 18.237 18.247 18.257 18.267 18.277 18.288 18.298 18.308 18.318 18.328 18.339 18301840 18.339 18.349 18.359 18.369 18.379 18.389 18.400 18.410 18.420 18.430 18.440 1840

1850 18.440 18.450 18.461 18.471 18.481 18.491 18.501 18.511 18.522 18.532 18.542 18501860 18.542 18.552 18.562 18.572 18.582 18.593 18.603 18.613 18.623 18.633 18.643 18601870 18.643 18.653 18.664 18.674 18.684 18.694 18.704 18.714 18.724 18.735 18.745 18701880 18.745 18.755 18.765 18.775 18.785 18.795 18.805 18.815 18.826 18.836 18.846 18801890 18.846 18.856 18.866 18.876 18.886 18.896 18.906 18.916 18.927 18.937 18.947 1890

1900 18.947 18.957 18.967 18.977 18.987 18.997 19.007 19.017 19.027 19.037 19.048 19901910 19.048 19.058 19.068 19.078 19.088 19.098 19.108 19.118 19.128 19.138 19.148 19101920 19.148 19.158 19.168 19.178 19.188 19.198 19.208 19.218 19.229 19.239 19.249 19201930 19.249 19.259 19.269 19.279 19.289 19.299 19.309 19.319 19.329 19.339 19.349 19301940 19.349 19.359 19.369 19.379 19.389 19.399 19.409 19.419 19.429 19.439 19.449 1940

1950 19.449 19.459 19.469 19.479 19.489 19.499 19.509 19.519 19.529 19.539 19.549 19501960 19.549 19.559 19.569 19.579 19.589 19.599 19.609 19.619 19.629 19.639 19.649 19601970 19.649 19.659 19.669 19.679 19.689 19.699 19.709 19.719 19.729 19.738 19.748 19701980 19.748 19.758 19.768 19.778 19.788 19.798 19.808 19.818 19.828 19.838 19.848 19801990 19.848 19.858 19.868 19.878 19.888 19.898 19.907 19.917 19.927 19.937 19.947 1990

MAXIMUM TEMPERATURE RANGEThermocouple Grade-32 to 4208°F-0 to 2320°CExtension Grade32 to 1600°F0 to 870°CLIMITS OF ERROR(whichever is greater)Standard: 4.5°C to 425°C1.0% to 2320°CSpecial: Not EstablishedCOMMENTS, BARE WIRE ENVIRONMENT:Vacuum, Inert; Hydrogen; Beware ofEmbrittlement; Not Practical Below 750°F;Not for Oxidizing AtmosphereTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°F CC

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

ThermocoupleGrade

Tungsten-5% Rhenium

vs.Tungsten-

26% Rhenium

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-243


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

2000 19.947 19.957 19.967 19.977 19.987 19.997 20.007 20.017 20.026 20.036 20.046 20002010 20.046 20.056 20.066 20.076 20.086 20.096 20.106 20.116 20.125 20.135 20.145 20102020 20.145 20.155 20.165 20.175 20.185 20.195 20.204 20.214 20.224 20.234 20.244 20202030 20.244 20.254 20.264 20.274 20.283 20.293 20.303 20.313 20.323 20.333 20.343 20302040 20.343 20.352 20.362 20.372 20.382 20.392 20.402 20.411 20.421 20.431 20.441 2040

2050 20.441 20.451 20.461 20.470 20.480 20.490 20.500 20.510 20.520 20.529 20.539 20502060 20.539 20.549 20.559 20.569 20.578 20.588 20.598 20.608 20.618 20.627 20.637 20602070 20.637 20.647 20.657 20.667 20.676 20.686 20.696 20.706 20.716 20.725 20.735 20702080 20.735 20.745 20.755 20.765 20.774 20.784 20.794 20.804 20.813 20.823 20.833 20802090 20.833 20.843 20.852 20.862 20.872 20.882 20.891 20.901 20.911 20.921 20.930 2090

2100 20.930 20.940 20.950 20.960 20.969 20.979 20.989 20.999 21.008 21.018 21.028 21002110 21.028 21.037 21.047 21.057 21.067 21.076 21.086 21.096 21.106 21.115 21.125 21102120 21.125 21.135 21.144 21.154 21.164 21.173 21.183 21.193 21.203 21.212 21.222 21202130 21.222 21.232 21.241 21.251 21.261 21.270 21.280 21.290 21.299 21.309 21.319 21302140 21.319 21.328 21.338 21.348 21.357 21.367 21.377 21.386 21.396 21.406 21.415 2140

2150 21.415 21.425 21.435 21.444 21.454 21.464 21.473 21.483 21.493 21.502 21.512 21502160 21.512 21.521 21.531 21.541 21.550 21.560 21.570 21.579 21.589 21.599 21.608 21602170 21.608 21.618 21.627 21.637 21.647 21.656 21.666 21.675 21.685 21.695 21.704 21702180 21.704 21.714 21.723 21.733 21.743 21.752 21.762 21.771 21.781 21.791 21.800 21802190 21.800 21.810 21.819 21.829 21.838 21.848 21.858 21.867 21.877 21.886 21.896 2190

2200 21.896 21.905 21.915 21.925 21.934 21.944 21.953 21.963 21.972 21.982 21.991 22002210 21.991 22.001 22.011 22.020 22.030 22.039 22.049 22.058 22.068 22.077 22.087 22102220 22.087 22.096 22.106 22.115 22.125 22.134 22.144 22.153 22.163 22.172 22.182 22202230 22.182 22.192 22.201 22.211 22.220 22.230 22.239 22.249 22.258 22.268 22.277 22302240 22.277 22.286 22.296 22.305 22.315 22.324 22.334 22.343 22.353 22.362 22.372 2240

2250 22.372 22.381 22.391 22.400 22.410 22.419 22.429 22.438 22.448 22.457 22.466 22502260 22.466 22.476 22.485 22.495 22.504 22.514 22.523 22.533 22.542 22.551 22.561 22602270 22.561 22.570 22.580 22.589 22.599 22.608 22.618 22.627 22.636 22.646 22.655 22702280 22.655 22.665 22.674 22.683 22.693 22.702 22.712 22.721 22.730 22.740 22.749 22802290 22.749 22.759 22.768 22.777 22.787 22.796 22.806 22.815 22.824 22.834 22.843 2290

2300 22.843 22.853 22.862 22.871 22.881 22.890 22.899 22.909 22.918 22.928 22.937 23002310 22.937 22.946 22.956 22.965 22.974 22.984 22.993 23.002 23.012 23.021 23.030 23102320 23.030 23.040 23.049 23.058 23.068 23.077 23.086 23.096 23.105 23.114 23.124 23202330 23.124 23.133 23.142 23.152 23.161 23.170 23.180 23.189 23.198 23.208 23.217 23302340 23.217 23.226 23.236 23.245 23.254 23.263 23.273 23.282 23.291 23.301 23.310 2340

2350 23.310 23.319 23.328 23.338 23.347 23.356 23.366 23.375 23.384 23.393 23.403 23502360 23.403 23.412 23.421 23.431 23.440 23.449 23.458 23.468 23.477 23.486 23.495 23602370 23.495 23.505 23.514 23.523 23.532 23.542 23.551 23.560 23.569 23.579 23.588 23702380 23.588 23.597 23.606 23.615 23.625 23.634 23.643 23.652 23.662 23.671 23.680 23802390 23.680 23.689 23.698 23.708 23.717 23.726 23.735 23.744 23.754 23.763 23.772 2390

2400 23.772 23.781 23.790 23.800 23.809 23.818 23.827 23.836 23.846 23.855 23.864 24002410 23.864 23.873 23.882 23.891 23.901 23.910 23.919 23.928 23.937 23.946 23.956 24102420 23.956 23.965 23.974 23.983 23.992 24.001 24.010 24.020 24.029 24.038 24.047 24202430 24.047 24.056 24.065 24.074 24.084 24.093 24.102 24.111 24.120 24.129 24.138 24302440 24.138 24.147 24.157 24.166 24.175 24.184 24.193 24.202 24.211 24.220 24.229 2440

2450 24.229 24.239 24.248 24.257 24.266 24.275 24.284 24.293 24.302 24.311 24.320 24502460 24.320 24.330 24.339 24.348 24.357 24.366 24.375 24.384 24.393 24.402 24.411 24602470 24.411 24.420 24.429 24.438 24.447 24.456 24.466 24.475 24.484 24.493 24.502 24702480 24.502 24.511 24.520 24.529 24.538 24.547 24.556 24.565 24.574 24.583 24.592 24802490 24.592 24.601 24.610 24.619 24.628 24.637 24.646 24.655 24.664 24.673 24.682 2490

2500 24.682 24.691 24.700 24.709 24.718 24.727 24.736 24.745 24.754 24.763 24.772 25002510 24.772 24.781 24.790 24.799 24.808 24.817 24.826 24.835 24.844 24.853 24.862 25102520 24.862 24.871 24.880 24.889 24.898 24.907 24.916 24.925 24.934 24.943 24.952 25202530 24.952 24.961 24.970 24.979 24.988 24.996 25.005 25.014 25.023 25.032 25.041 25302540 25.041 25.050 25.059 25.068 25.077 25.086 25.095 25.104 25.113 25.122 25.130 2540

2550 25.130 25.139 25.148 25.157 25.166 25.175 25.184 25.193 25.202 25.211 25.219 25502560 25.219 25.228 25.237 25.246 25.255 25.264 25.273 25.282 25.291 25.299 25.308 25602570 25.308 25.317 25.326 25.335 25.344 25.353 25.362 25.370 25.379 25.388 25.397 25702580 25.397 25.406 25.415 25.424 25.432 25.441 25.450 25.459 25.468 25.477 25.486 25802590 25.486 25.494 25.503 25.512 25.521 25.530 25.539 25.547 25.556 25.565 25.574 2590

2600 25.574 25.583 25.592 25.600 25.609 25.618 25.627 25.636 25.644 25.653 25.662 26002610 25.662 25.671 25.680 25.688 25.697 25.706 25.715 25.724 25.732 25.741 25.750 26102620 25.750 25.759 25.76 25.776 25.785 25.794 25.803 25.811 25.820 25.829 25.838 26202630 25.838 25.846 25.855 25.864 25.873 25.882 25.890 25.899 25.908 25.917 25.925 26302640 25.925 25.934 25.943 25.952 25.960 25.969 25.978 25.986 25.995 26.004 26.013 2640

2650 26.013 26.021 26.030 26.039 26.048 26.056 26.065 26.074 26.082 26.091 26.100 26502660 26.100 26.109 26.117 26.126 26.135 26.143 26.152 26.161 26.170 26.178 26.187 26602670 26.187 26.196 26.204 26.213 26.222 26.230 26.239 26.248 26.256 26.265 26.274 26702680 26.274 26.282 26.291 26.300 26.308 26.317 26.326 26.334 26.343 26.352 26.360 26802690 26.360 26.369 26.378 26.386 26.395 26.404 26.412 26.421 26.430 26.438 26.447 2690

2700 26.447 26.455 26.464 26.473 26.481 26.490 26.499 26.507 26.516 26.524 26.533 27002710 26.533 26.542 26.550 26.559 26.568 26.576 26.585 26.593 26.602 26.611 26.619 27102720 26.619 26.628 26.636 26.645 26.654 26.662 26.671 26.679 26.688 26.696 26.705 27202730 26.705 26.714 26.722 26.731 26.739 26.748 26.756 26.765 26.774 26.782 26.791 27302740 26.791 26.799 26.808 26.816 26.825 26.834 26.842 26.851 26.859 26.868 26.876 2740

2750 26.876 26.885 26.893 26.902 26.910 26.919 26.927 26.936 26.945 26.953 26.962 27502760 26.962 26.970 26.979 26.987 26.996 27.004 27.013 27.021 27.030 27.038 27.047 27602770 27.047 27.055 27.064 27.072 27.081 27.089 27.098 27.106 27.115 27.123 27.132 27702780 27.132 27.140 27.149 27.157 27.166 27.174 27.183 27.191 27.200 27.208 27.216 27802790 27.216 27.225 27.233 27.242 27.250 27.259 27.267 27.276 27.284 27.293 27.301 2790

2800 27.301 27.309 27.318 27.326 27.335 27.343 27.352 27.360 27.369 27.377 27.385 28002810 27.385 27.394 27.402 27.411 27.419 27.428 27.436 27.444 27.453 27.461 27.470 28102820 27.470 27.478 27.486 27.495 27.503 27.512 27.520 27.528 27.537 27.545 27.554 28202830 27.554 27.562 27.570 27.579 27.587 27.596 27.604 27.612 27.621 27.629 27.637 28302840 27.637 27.646 27.654 27.663 27-671 27.679 27.688 27.696 27.704 27.713 27.721 2840

2850 27.721 27.729 27.738 27.746 27.755 27.763 27.771 27.780 27.788 27.796 27.805 28502860 27.805 27.813 27.821 27.830 27.838 27.846 27.855 27.863 27.871 27.880 27.888 28602870 27.888 27.896 27.904 27.913 27.921 27.929 27.938 27.946 27.954 27.963 27.971 28702880 27.971 27.979 27.988 27.996 28.004 28.012 28.021 28.029 28.037 28.046 28.054 28802890 28.054 28.062 28.070 28.079 28.087 28.095 28.103 28.112 28.120 28.128 28.137 2890

2900 28.137 28.145 28.153 28.161 28.170 28.178 28.186 28.194 28.203 28.211 28.219 29002910 28.219 28.227 28.236 28.244 28.252 28.260 28.268 28.277 28.285 28.293 28.301 29102920 28.301 28.310 28.318 28.326 28.334 28.342 28.351 28.359 28.367 28.375 28.384 29202930 28.384 28.392 28.400 28.408 28.416 28.425 28.433 28.441 28.449 28.457 28.466 29302940 28.466 28.474 28.482 28.490 28.498 28.506 28.515 28.523 28.531 28.539 28.547 2940

2950 28.547 28.555 28.564 28.572 28.580 28.588 28.596 28.604 28.613 28.621 28.629 29502960 28.629 28.637 28.645 28.653 28.661 28.670 28.678 28.686 28.694 28.702 28.710 29602970 28.710 28.718 28.727 28.725 28.743 28.751 28.759 28.767 28.775 28.783 28.791 29702980 28.791 28.800 28.808 28.816 28.824 28.832 28.840 28.848 28.856 28.864 28.872 29802990 28.872 28.881 28.889 28.897 28.905 28.913 28.921 28.929 28.937 28.945 28.953 2990


ThermocoupleGrade

Tungsten-5% Rhenium

vs.Tungsten-

26% Rhenium

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-244

Z


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

3000 28.953 28.961 28.969 28.978 28.986 28.994 29.002 29.010 29.018 29.026 29.034 30003010 29.034 29.042 29-050 29.058 29.066 29.074 29.082 29.090 29.098 29.106 29.114 30103020 29.114 29.122 29.130 29.138 29.147 29.155 29.163 29.171 29.179 29.187 29.195 30203030 29.195 29.203 29.211 29.219 29.227 29.235 29.243 29.251 29.259 29.267 29.275 30303040 29.275 29.283 29.291 29.299 29.307 29.315 29.323 29.331 29.339 29.347 29.355 3040

3050 29.355 29.363 29.371 29.379 29.386 29.394 29.402 29.410 29.418 29.426 29.434 30503060 29.434 29.442 29.450 29.458 29.466 29.474 29.482 29.490 29.498 29.506 29.514 30603070 29.514 29.522 29.530 29.538 29.546 29.553 29.561 29.569 29.577 29.585 29.593 30703080 29.593 29.601 29.609 29.617 29.625 29.633 29.641 29.648 29.656 29.664 29.672 30803090 29.672 29.680 29.688 29.696 29.704 29.712 29.720 29.727 29.735 29.743 29.751 3090

3100 29.751 29.759 29.767 29.775 29.783 29.791 29.798 29.806 29.814 29.822 29.830 31003110 29.830 29.838 29.846 29.853 29.861 29.869 29.877 29.885 29.893 29.901 29.908 3110 3120 29.908 29.916 29.924 29.932 29.940 29.948 29.955 29.963 29.971 29.979 29.987 31203130 29.987 29.995 30.002 30.010 30.018 30.026 30.034 30.041 30.049 30.057 30.065 31303140 30.065 30.073 30.081 30.088 30.096 30.104 30.112 30.119 30.127 30.135 30.143 3140

3150 30.143 30.151 30.158 30.166 30.174 30.182 30.190 30.197 30.205 30.213 30.221 31503160 30.221 30.228 30.236 30.244 30.252 30.259 30.267 30.275 30.283 30.290 30.298 31603170 30.298 30.306 30.314 30.321 30.329 30.337 30.345 30.352 30.360 30.368 30.376 31703180 30.376 30.383 30.391 30.399 30.406 30.414 30.422 30.430 30.437 30.445 30.453 31803190 30.453 30.460 30.468 30.476 30.484 30.491 30.499 30.507 30.514 40.522 30.530 3190

3200 30.530 30.537 30.545 30.553 30.561 30.568 30.576 30.584 30.591 30.599 30.607 32003210 30.607 30.614 30.622 30.630 30.637 30.645 30.653 30.660 30.668 30.676 30.683 32103220 30.683 30.691 30.698 30.706 30.714 30.721 30.729 30.737 30.744 30.752 30.760 32203230 30.760 30.767 30.775 30.782 30.790 30.798 30.805 30.813 30.821 30.828 30.836 32303240 30.836 30.843 30.851 30.859 30.866 30.874 30.881 30.889 30.897 30.904 30.912 3240

3250 30.912 30.919 30.927 30.935 30.942 30.950 30.957 30.965 30.972 30.980 30.988 32503260 30.988 30.995 31.003 31.010 31.018 31.025 31.033 31.041 31.048 31.056 31.063 32603270 31.063 31.071 31.078 31.086 31.093 31.101 31.109 31.116 31.124 31.131 31.139 32703280 31.139 31.146 31.154 31.161 31.169 31.176 31.184 31.191 31.199 31.206 31.214 32803290 31.214 31.221 31.229 31.236 31.244 31.251 31.259 31.266 31.274 31.281 31.289 3290

3300 31.289 31.296 31.304 31.311 31.319 31.326 31.334 31.341 31.349 31.356 31.364 33003310 31.364 31.371 31.379 31.386 31.394 31.401 31.408 31.416 31.423 31.431 31.438 33103320 31.438 31.446 31.453 31.461 31.468 31.476 31.483 31.490 31.498 31.505 31.513 33203330 31.513 31.520 31.528 31.535 31.542 31.550 31.557 31.565 31.572 31.580 31.587 33303340 31.587 31.594 31.602 31.609 31.617 31.624 31.631 31.639 31.646 31.654 31.661 3340

3350 31.661 31.668 31.676 31.683 31.690 31.698 31.705 31.713 31.720 31.727 31.735 33503360 31.735 31.742 31.749 31.757 31.764 31.772 31.779 31.786 31.794 31.801 31.808 33603370 31.808 31.816 31.823 31.830 31.838 31.845 31.852 31.860 31.867 31.874 31.882 33703380 31.882 31.889 31.896 31.904 31.911 31.918 31.926 31.933 31.940 31.948 31.955 33803390 31.955 31.962 31.969 31.977 31.984 31.991 31.999 32.006 32.013 32.021 32.028 3390

3400 32.028 32.035 32.042 32.050 32.057 32.064 32.072 32.079 32.086 32.093 32.101 34003410 32.101 32.108 32.115 32.122 32.130 32.137 32.144 32.151 32.159 32.166 32.173 34103420 32.173 32.180 32.188 32.195 32.202 32.209 32.217 32.224 32.231 32.238 32.246 34203430 32.246 32.253 32.260 32.267 32.274 32.282 32.289 32.296 32.303 32.310 32.318 34303440 32.318 32.325 32.332 32.339 32.346 32.354 32.361 32.368 32.375 32.382 32.390 3440

3450 32.390 32.397 32.404 32.411 32.418 32.425 32.433 32.440 32.447 32.454 32.461 34503460 32.461 32.468 32.476 32.483 32.490 32.497 32.504 32.511 32.518 32.526 32.533 34603470 32.533 32.540 32.547 32.554 32.561 32.568 32.576 32.583 32.590 32.597 32.604 34703480 32.604 32.611 32.618 32.625 32.632 32.640 32.647 32.654 32.661 32.668 32.675 34803490 32.675 32.682 32.689 32.696 32.703 32.711 32.718 32.725 31.732 32.739 32.746 3490

3500 32.746 32.753 32.760 32.767 32.774 32.781 32.788 32.795 32.802 32.809 32.817 35003510 32.817 32.824 32.831 32.838 32.845 32.852 32.859 32.866 32.873 32.880 32.887 35103520 32.887 32.894 32.901 32.908 32.915 32.922 32.929 32.936 32.943 32.950 32.957 35203530 32.957 32.964 32.971 32.978 32.985 32.992 32.999 33.006 33.013 33.020 33.027 35303540 33.027 33.034 33.041 33.048 33.055 33.062 33.069 33.076 33-083 33.090 33.097 3540

3550 33.097 33.104 33.111 33.118 33.125 33.132 33.139 33.146 33.152 33.159 33.166 35503560 33.166 33.173 33.180 33.187 33.194 33.201 33.208 33.215 33.222 33.229 33.236 35603570 33.236 33.243 33.249 33.256 33.263 33.270 33.277 33.284 33.291 33.298 33.305 35703580 33.305 33.312 33.318 33.325 33.332 33.339 33.346 33.353 33.360 33.367 33.374 35803590 33.374 33.380 33.387 33.394 33.401 33.408 33.415 33.422 33.428 33.435 33.442 3590

3600 33.442 33.449 33.456 33.463 33.469 33.476 33.483 33.490 33.497 33.504 33.510 36003610 33.510 33.517 33.524 33.531 33.538 33.545 33.551 33.558 33.565 33.572 33.579 36103620 33.579 33.585 33.592 33.599 33.606 33.613 33.619 33.626 33.633 33.640 33.647 36203630 33.647 33.653 33.660 33.667 33.674 33.680 33.687 33.694 33.701 33.707 33.714 36303640 33.714 33.721 33.728 33.734 33.741 33.748 33.755 33.761 33.768 33.775 33.782 3640

3650 33.782 33.788 33.795 33.802 33.809 33.815 33.822 33.829 33.835 33.842 33.849 36503660 33.849 33.856 33.862 33.869 33.876 33.882 33:889 33.896 33.902 33.909 33.916 36603670 33.916 33.922 33.929 33.936 33.942 33.949 33.956 33.962 33.969 33.976 33.982 36703680 33.982 33.989 33.996 34.002 34.009 34.016 34.022 34.029 34.036 34.042 34.049 36803690 34.049 34.056 34.062 34-069 34.075 34.082 34.089 34.095 34.102 34.109 34.115 3690

3700 34.115 34.122 34.128 34.135 34.142 34.148 34.155 34.161 34.168 34.175 34.181 37003710 34.181 34.188 34.194 34.201 34.207 34.214 34.221 34.227 34.234 34.240 34.247 37103720 34.247 34.253 34.260 34.267 34.273 34.280 34.286 34.293 34.299 34.306 34.312 37203730 34.312 34.319 34.325 34.332 34.338 34.345 34.351 34.358 34.365 34.371 34.378 37303740 34.378 34.384 34.391 34.397 34.404 34.410 34.417 34.423 34.430 34.436 34.442 3740

3750 34.442 34.449 34.455 34.462 34.468 34.475 34.481 34.488 34.494 34.501 34.507 37503760 34.507 34.514 34-520 34.527 34.533 34.539 34.546 34.552 34.559 34.565 34.572 37603770 34.572 34.578 34.585 34.591 34.597 34.604 34.610 34.617 34.623 34.629 34.636 37703780 34.636 34.642 34.649 34.655 34.661 34.668 34.674 34.681 34.687 34.693 34.700 37803790 34.700 34.706 34.713 34.719 34.725 34.732 34.738 34.744 34.751 34.757 34.763 3790

3800 34.763 34.770 34.776 34.782 34.789 34.795 34.802 34.808 34.814 34.821 34.827 38003810 34.827 34.833 34.839 34.846 34.852 34.858 34.865 34.871 34.877 34.884 34.890 38103820 34.890 34.896 34.903 34.909 34.915 34.921 34.928 34.934 34.940 34.947 34.953 38203830 34.953 34.959 34.965 34.972 34.978 34.984 34.990 34.997 35.003 35.009 35.015 38303840 35.015 35.022 35.028 35.034 35.040 35.047 35.053 35.059 35.065 35.072 35.078 3840

3850 35.078 35.084 35.090 35.096 35.103 35.109 35.115 35.121 35.127 35.134 35.140 38503860 35.140 35.146 35.152 35.158 35.165 35.171 35.177 35.183 35.189 35.195 35.202 38603870 35.202 35.208 35.214 35.220 35.226 35.132 35.238 35.245 35.251 35.257 35.263 38703880 35.263 35.269 35.275 35.281 35.288 35.294 35.300 35.306 35.312 35.318 35.324 38803890 35.324 35.330 35.336 35.343 35.349 35.355 35.361 35.367 35.373 35.379 35.385 3890

3900 35.385 35.391 35.397 35.403 35.409 35.415 35.422 35.428 35.434 35.440 35.446 39003910 35.446 35.452 35.458 35.464 35.470 35.476 35.482 35.488 35.494 35.500 35.506 39103920 35.506 35.512 35.518 35.524 35.530 35.536 35.542 35.548 35.554 35.560 35.566 39203930 35.566 35.572 35.578 35.584 35.590 35.596 35.602 35.608 35.614 35.620 35.626 39303940 35.626 35.632 35.638 35.644 35.650 35.656 35.662 35.668 35.673 35.679 35.685 3940

3950 35.685 35.691 35.697 35.703 35.709 35.715 35.721 35.727 35.733 35.739 35.744 39503960 35.744 35.750 35.756 35.762 35.768 35.774 35.780 35.786 35.792 35.797 35.803 39603970 35.803 35.809 35.815 35.821 35.827 35.833 35.838 35.844 35.850 35.856 35.862 39703980 35.862 35.868 35.873 35.879 35.885 35.891 35.897 35.903 35.908 35.914 35.920 39803990 35.920 35.926 35.932 35.937 35.943 35.949 35.955 35.961 35.966 35.972 35.978 3990

MAXIMUM TEMPERATURE RANGEThermocouple Grade-32 to 4208°F-0 to 2320°CExtension Grade32 to 1600°F0 to 870°CLIMITS OF ERROR(whichever is greater)Standard: 4.5°C to 425°C1.0% to 2320°CSpecial: Not EstablishedCOMMENTS, BARE WIRE ENVIRONMENT:Vacuum, Inert; Hydrogen; Beware ofEmbrittlement; Not Practical Below 750°F;Not for Oxidizing AtmosphereTEMPERATURE IN DEGREES °FREFERENCE JUNCTION AT 32°F CC

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

ThermocoupleGrade

Tungsten-5% Rhenium

vs.Tungsten-

26% Rhenium

ExtensionGrade

+–

+–


NONEESTABLISHED


Z-245


°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

°F 0 1 2 3 4 5 6 7 8 9 10 °F °F 0 1 2 3 4 5 6 7 8 9 10 °F

4000 35.978 35.984 35.989 35.995 36.001 36.007 36.013 36.018 36.024 36.030 36.036 40004010 36.036 36.041 36.047 36:053 36.058 36.064 36.070 36.076 36.081 36.087 36.093 40104020 36.093 36.099 36.104 36.110 36.116 36.121 36-127 36.133 36.138 36.144 36.150 40204030 36.150 36.155 36.161 36.167 36.172 36.178 36.184 36.189 36.195 36.201 36.206 40304040 36.206 36.212 36.218 36.223 36.229 36.235 36.240 36.246 36.251 36.257 36.263 4040

4050 36.263 36.268 36.274 36.280 36.285 36.291 36.296 36.302 36.308 36.313 36.319 40504060 36.319 36.324 36.330 36.335 36.341 36.347 36.352 36.358 36.363 36.369 36.374 40604070 36.374 36.380 36.385 36.391 36.397 36.402 36.408 36.413 36.419 36.424 36.430 40704080 36.430 36.435 36.441 36.446 36.452 36.457 36.463 36.468 36.474 36.479 36.485 40804090 36.485 36.490 36.496 36.501 36.507 36.512 36.517 36:523 36.528 36.534 36.539 4090

4100 36.539 36.545 36.550 36.556 36-561 36.566 36.572 36.577 36.583 36.588 36.594 41004110 36.594 36.599 36.604 36.610 36.615 36.621 36.626 36.631 36.637 36.642 36.647 41104120 36.647 36.653 36.658 36.664 36.669 36.674 36.680 36.685 36.690 36.696 36.701 41204130 36.701 36.706 36.712 36.717 36.722 36.728 36.733 36.738 36.744 36.749 36.754 41304140 36.754 36.760 36.765 36.770 36.775 36.781 36.786 36.791 36.797 36.802 36.807 4140

4150 36.807 36.812 36.818 36.823 36.828 36.833 36.839 36.844 36.849 36.854 36.860 41504160 36.860 36.865 36.870 36.875 36.881 36.886 36.891 36.896 36.901 36.907 36.912 41604170 36.912 36.917 36.922 36.927 36.933 36.938 36.943 36.948 36.953 36.958 36.964 41704180 36.964 36.969 36.974 36.979 36.984 36.989 36.994 37.000 37.005 37.010 37.015 41804190 37.015 37.020 37.025 37.030 37.035 37.041 37.046 37.051 37.056 37.061 37.066 4190


ThermocoupleGrade

Tungsten-5% Rhenium

vs.Tungsten-

26% Rhenium

ExtensionGrade

+–

+–


NONEESTABLISHED

Adopted March 4, 1974

Z-246

Z

DEGREES F 0° 20° 40° 60° 80° DEGREES F 0° 20° 40° 60° 80°0° -.016 -.007 0.006 0.026 0.050 2200° 18.701 18.936 19.170 19.405 19.639

100° 0.079 0.113 0.153 0.197 0.246 2300° 19.873 20.106 20.340 20.573 20.806200° 0.299 0.357 0.420 0.487 0.559 2400° 21.038 21.270 21.502 21.734 21.965300° 0.634 0.714 0.799 0.887 0.979 2500° 22.195 22.425 22.655 22.884 23.113400° 1.075 1.175 1.279 1.387 1.498 2600° 23.341 23.569 23.796 24.023 24.249500° 1.613 1.731 1.853 1.978 2.106 2700° 24.474 24.699 24.923 25.146 25.369600° 2.238 2.373 2.511 2.652 2.796 2800° 25.591 25.812 26.033 26.253 26.472700° 2.943 3.093 3.246 3.401 3.559 2900° 26.690 26.907 27.124 27.340 27.555800° 3.720 3.884 4.049 4.218 4.389 3000° 27.769 27.983 28.195 28.407 28.618900° 4.562 4.737 4.915 5.095 5.277 3100° 28.827 29.036 29.244 29.451 29.657

1000° 5.461 5.647 5.836 6.026 6.218 3200° 29.862 30.066 30.269 30.471 30.6721100° 6.412 6.607 6.805 7.004 7.205 3300° 30.871 31.070 31.268 31.464 31.6601200° 7.407 7.611 7.816 8.023 8.232 3400° 31.854 32.047 32.240 32.430 32.6201300° 8.441 8.652 8.865 9.078 9.293 3500° 32.809 32.996 33.182 33.367 33.5511400° 9.509 9.726 9.945 10.164 10.384 3600° 33.733 33.914 34.094 34.273 34.4501500° 10.606 10.828 11.051 11.275 11.500 3700° 34.626 34.801 34.974 35.146 35.3171600° 11.725 11.952 12.179 12.407 12.635 3800° 35.486 35.654 35.821 35.986 36.1501700° 12.864 13.094 13.324 13.555 13.786 3900° 36.312 36.473 36.632 36.790 36.9461800° 14.018 14.250 14.482 14.715 14.948 4000° 37.101 37.254 37.406 37.557 37.7051900° 15.182 15.415 15.649 15.884 16.118 4100° 37.853 37.998 38.142 38.285 38.4252000° 16.353 16.587 16.822 17.057 17.292 4200° 38.5642100° 17.527 17.762 17.997 18.232 18.467


100° 0.522 0.682 0.845 1.010 1.178 2300° 22.843 23.030 23.217 23.403 23.588200° 1.348 1.520 1.695 1.872 2.051 2400° 23.772 23.956 24.138 24.320 24.502300° 2.232 2.415 2.600 2.786 2.975 2500° 24.682 24.862 25.041 25.219 25.397400° 3.165 3.357 3.551 3.746 3.942 2600° 25.574 25.750 25.925 26.100 26.274500° 4.140 4.339 4.540 4.742 4.945 2700° 26.447 26.619 26.791 26.962 27.132600° 5.149 5.354 5.560 5.767 5.975 2800° 27.301 27.470 27.637 27.805 27.971700° 6.184 6.394 6.604 6.815 7.027 2900° 28.137 28.301 28.466 28.629 28.791800° 7.240 7.453 7.667 7.881 8.095 3000° 28.953 29.114 29.275 29.434 29.593900° 8.310 8.526 8.741 8.957 9.174 3100° 29.751 29.908 30.065 30.221 30.376

1000° 9.390 9.607 9.824 10.041 10.258 3200° 30.530 30.683 30.836 30.988 31.1391100° 10.475 10.693 10.910 11.127 11.344 3300° 31.289 31.438 31.587 31.735 31.8821200° 11.561 11.778 11.995 12.212 12.429 3400° 32.028 32.173 32.318 32.461 32.6041300° 12.645 12.861 13.077 13.292 13.508 3500° 32.746 32.887 33.027 33.166 33.3051400° 13.723 13.937 14.152 14.366 14.579 3600° 33.442 33.579 33.714 33.849 33.9821500° 14.792 15.005 15.217 15.429 15.640 3700° 34.115 34.247 34.378 34.507 34.6361600° 15.851 16.062 16.271 16.481 16.689 3800° 34.763 34.890 35.015 35.140 35.2631700° 16.898 17.105 17.312 17.519 17.725 3900° 35.385 35.506 35.626 35.744 35.8621800° 17.930 18.134 18.339 18.542 18.745 4000° 35.978 36.093 36.206 36.319 36.4301900° 18.947 19.148 19.349 19.549 19.748 4100° 36.539 36.647 36.754 36.860 36.9642000° 19.947 20.145 20.343 20.539 20.735 4200° 37.0662100° 20.930 21.125 21.319 21.512 21.704


100° 0.390 0.515 0.644 0.778 0.916 2300° 23.283 23.492 23.701 23.909 24.116200° 1.058 1.204 1.354 1.507 1.664 2400° 24.323 24.529 24.735 24.940 25.145300° 1.824 1.988 2.154 2.324 2.497 2500° 25.348 25.551 25.754 25.956 26.157400° 2.673 2.851 3.032 3.216 3.402 2600° 26.358 26.558 26.757 26.956 27.154500° 3.590 3.781 3.973 4.168 4.365 2700° 27.352 27.548 27.745 27.940 28.135600° 4.564 4.765 4.967 5.171 5.377 2800° 28.329 28.523 28.715 28.908 29.099700° 5.584 5.793 6.003 6.214 6.427 2900° 29.290 29.480 29.669 29.858 30.046800° 6.640 6.855 7.071 7.288 7.506 3000° 30.233 30.419 30.605 30.790 30.974900° 7.725 7.945 8.165 8.386 8.608 3100° 31.158 31.340 31.522 31.703 31.884

1000° 8.830 9.053 9.277 9.501 9.726 3200° 32.063 32.242 32.420 32.596 32.7721100° 9.951 10.176 10.402 10.628 10.854 3300° 32.948 33.122 33.295 33.467 33.6391200° 11.080 11.307 11.534 11.761 11.988 3400° 33.809 33.979 34.147 34.314 34.4811300° 12.215 12.443 12.670 12.897 13.125 3500° 34.646 34.810 34.973 35.135 35.2951400° 13.352 13.579 13.807 14.034 14.262 3600° 35.455 35.613 35.770 35.926 36.0801500° 14.489 14.717 14.944 15.171 15.398 3700° 36.233 36.384 36.535 36.683 36.8311600° 15.624 15.850 16.076 16.302 16.527 3800° 36.976 37.120 37.263 37.404 37.5431700° 16.752 16.976 17.200 17.424 17.647 3900° 37.681 37.816 37.950 38.082 38.2131800° 17.870 18.093 18.315 18.537 18.758 4000° 38.341 38.467 38.591 38.714 38.8341900° 18.979 19.199 19.419 19.638 19.857 4100° 38.951 39.067 39.180 39.291 39.4002000° 20.075 20.293 20.510 20.726 20.943 4200° 39.5062100° 21.158 21.373 21.588 21.802 22.015

Tungsten vs. Tungsten-26% Rhenium - Type G*Temperature in Degrees F Reference Junction at 32°F

Tungsten-5% Rhenium vs. Tungsten-26% Rhenium - Type C*Temperature in Degrees F Reference Junction at 32°F

Tungsten-3% Rhenium vs. Tungsten-25% Rhenium - Type D*Temperature in Degrees F Reference Junction at 32°F

Adopted March 4, 1974 *Not an ANSI designationHoskins Manufacturing Company

Adopted March 4, 1974

Z-247

Temperature Temperature Temperature Temperature(KELVIN) E, µV (KELVIN) E, µV (KELVIN) E, µV (KELVIN) E, µV

35 545.40 70 1136.21 105 1776.7136 561.86 71 1153.80 106 1795.7337 578.31 72 1171.44 107 1814.78

3 28.02 38 594.76 73 1189.12 108 1833.864 39.94 39 611.22 74 1206.84 109 1852.99

5 52.84 40 627.68 75 1224.60 110 1872.146 66.58 41 644.16 76 1242.40 111 1891.347 81.01 42 660.65 77 1260.25 112 1910.578 96.02 43 677.16 78 1278.14 113 1929.839 111.51 44 693.69 79 1296.08 114 1949.13

10 127.39 45 710.24 80 1314.05 115 1968.4611 143.58 46 726.82 81 1332.07 116 1987.8212 160.02 47 743.43 82 1350.13 117 2007.2213 176.65 48 760.07 83 1368.23 118 2026.6514 193.42 49 776.74 84 1386.37 119 2046.11

15 210.29 50 793.45 85 1404.56 120 2065.6116 227.23 51 810.20 86 1422.79 121 2085.1417 244.21 52 826.98 87 1441.05 122 2104.7018 261.21 53 843.80 88 1459.36 123 2124.2919 278.20 54 860.66 89 1477.71 124 2143.91

20 295.18 55 877.56 90 1496.10 125 2163.5621 312.14 56 894.50 91 1514.53 126 2183.2422 329.06 57 911.49 92 1533.00 127 2202.9623 345.94 58 928.51 93 1551.52 128 2222.7024 362.77 59 945.58 94 1570.07 129 2242.47

25 379.56 60 962.70 95 1588.66 130 2262.2726 396.31 61 979.85 96 1607.29 131 2282.1027 413.01 62 997.05 97 1625.96 132 2301.9628 429.67 63 1014.29 98 1644.67 133 2321.8529 446.29 64 1013.58 99 1663.42 134 2341.76

30 462.87 65 1048.91 100 1682.21 135 2361.7031 479.43 66 1066.28 101 1701.03 136 2381.6832 495.95 67 1083.70 102 1719.90 137 2401.6733 512.45 68 1101.16 103 1738.80 138 2421.7034 528.93 69 1118.66 104 1757.74 139 2441.75

Table of Temperature vs.Thermoelectric Voltage

CHROMEGA® VS. GOLD-0.07ATOMIC PERCENT IRONTHERMOCOUPLE

Z-248

Z

Temperature Temperature Temperature Temperature(KELVIN) E, µV (KELVIN) E, µV (KELVIN) E, µV (KELVIN) E, µV

140 2461.83 175 3180.19 210 3923.82 245 4686.39141 2481.94 176 3201.12 211 3945.38 246 4708.38142 2502.07 177 3222.07 212 3966.95 247 4730.37143 2522.23 178 3243.04 213 3988.54 248 4752.38144 2542.42 179 3264.03 214 4010.15 249 4774.39

145 2562.63 180 3285.03 215 4031.77 250 4796.41146 2582.87 181 3306.06 216 4053.40 251 4818.45147 2603.13 182 3327.11 217 4075.06 252 4840.49148 2623.42 183 3348.18 218 4096.72 253 4862.54149 2643.73 184 3369.27 219 4118.40 254 4884.60

150 2664.07 185 3390.37 220 4140.09 255 4906.68151 2684.44 186 3411.50 221 4161.80 256 4928.76152 2704.82 187 3432.64 222 4183.52 257 4950.85153 2725.24 188 3453.80 223 4205.26 258 4972.96154 2745.67 189 3474.98 224 4227.01 259 4995.07

155 2766.14 190 3496.18 225 4248.77 260 5017.20156 2786.62 191 3517.40 226 4270.55 261 5039.34157 2807.13 192 3538.63 227 4292.33 262 5061.49158 2827.67 193 3559.88 228 4314.13 263 5083.65159 2848.22 194 3581.15 229 4335.95 264 5105.83

160 2868.80 195 3602.44 230 4357.77 265 5128.01161 2889.41 196 3623.75 231 4379.61 266 5150.21162 2910.03 197 3645.07 232 4401.45 267 5172.42163 2930.68 198 3666.41 233 4423.31 268 5194.64164 2951.35 199 3687.77 234 4445.18 269 5216.87

165 2972.05 200 3709.14 235 4467.06 270 5239.11166 2992.77 201 3730.54 236 4488.95 271 5261.36167 3013.50 202 3751.95 237 4510.85 272 5283.62168 3034.27 203 3773.37 238 4532.76 273 5305.88169 3055.05 204 3794.82 239 4554.68 274 5328.16

170 3075.85 205 3816.28 240 4576.61 275 5350.44171 3096.68 206 3837.75 241 4598.55 276 5372.73172 3117.52 207 3859.25 242 4620.49 277 5395.02173 3138.39 208 3880.76 243 4642.45 278 5417.31174 3159.28 209 3902.28 244 4664.42 279 5439.61

Z-249

Space for Transmitters inProbe Assembly Heads

HEAD TRANSMITTER SPACE PROBES

Model Number Diameter, mm Height, mm Typical(in) (in)

NB1 47.6 19.0 NB1-ICSS-14G-12(1 7⁄8) (3⁄4) PR-12-2-100-1/8-6-E

NB2 31.7 19.0 NB2-ICSS-14G-24(1 1⁄4) (3⁄4) PR-14-2-100-1/8-6-E

NB3 57.1 25.4 NB1-ICSS-14G-12(2 1⁄4) (1) PR-18-2-100-1/8-6-E

NB4 22.2 9.5 NB4-ICSS-14G-12(7⁄8) (3⁄8) PR-19-2-100-1/8-6-E

NEPA, NEPB 69.8 38.1 NEPB-ICSS-14G-12(2 3⁄4) (1 1⁄2) NEPB-2-100-1/8-6-E

NBS 50.8 31.7 NBS-ICSS-14G-12(2) (1 1⁄4) NBS-2-100-1/8-6-E

NSA, NSB, NSC 50.8 31.7 NSB-ICSS-14G-12(2) (1 1⁄4) NSB-2-100-1/8-6-E

NBB 47.6 19.0 NBB-ICSS-14G-12(1 7⁄8) (3⁄4) NBB-2-100-1/8-6-E

NBN 50.8 19.0 NBN-ICSS-14G-12(2) (3⁄4) NBN-2-100-1/8-6-E

NBG 44.4 19.0 NBG-ICSS-14G-12(1 3⁄4) (3⁄4) NBG-2-100-1/8-6-E

NXT 47.6 50.8 NXT-ICSS-14G-12(1 7⁄8) (2) NXT-2-100-1/8-6-E

HEP-TX 76.2 50.8 HEP-TX-100-J1(3) (2) HEP-TX-110-PT1

HEP-TX70 76.2 50.8 HEP-TX71-J-50-350C(3) (2) HEP-TX75-50-350C

Z-250

Z

TEMPERATURE °C

Tolerance

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

2.25

2.0

1.75

1.5

1.25

1.0

0.75

0.5

0.25

OHMS deg C

Basic DetectorResistance at0°C Is 100 ohms

CLASS BDIN 43760-1980BS 1904

CLASS ADIN 43760-1980BS 1904

JISC1604-19810.15

JISC1604-1981

0.2

JISC1604-1981

0.5

-200 -100 0 100 200 300 400 500

Detector Interchangeability Tolerance Chart

Platinum ResistanceTemperature Detectors

Z-251

RTD TablesAccording to DIN EN 60751for Class B and Class A

Resistance vs Temperature TablesAccording to DIN EN 60751 for Class B and Class A

∝ = .00385 per ITS-90

t ≥ 0°C : t < 0°C :

R(t) = R0 · (1 + A · t + B · t2) R(t) = R0 · [1 + A · t + B · t2 + C ·(t - 100°C) · t3)

with with

A = 3,9083 · 10-3 °C-1 A = 3,9083 · 10-3 °C-1

B = -5,775 · 10-7 °C-2 B = -5,775 · 10-7 °C-2

R0 = 100Ω C = -4,183 · 10-13 °C

R0 = 100Ω

Class B:

dt = ±(0.3 + 0.005 · lt l)°C

Class A

dt = ±(0.15 + 0.002 · lt l)°C

Z-252

Z

°C Ohms Diff. °C Ohms Diff. °C Ohms Diff. °C Ohms Diff. °C Ohms Diff. °C Ohms Diff.

-200 18.52 -140 43.88 0.42 -80 68.33 0.41 -20 92.16 0.39 ± 0 100.00 0.39 +60 123.24 0.38199 18.96 0.44 139 44.29 0.41 79 68.73 0.40 19 92.55 0.39 + 1 100.39 0.39 61 123.62 0.38198 19.39 0.43 138 44.71 0.42 78 69.13 0.40 18 92.95 0.40 2 100.78 0.39 62 124.01 0.39197 19.82 0.43 137 45.12 0.41 77 69.53 0.40 17 93.34 0.39 3 101.17 0.39 63 124.39 0.38196 20.25 0.43 136 45.53 0.41 76 69.93 0.40 16 93.73 0.39 4 101.56 0.39 64 124.77 0.38195 20.68 0.43 135 45.95 0.42 75 70.33 0.40 15 94.12 0.39 5 101.95 0.39 65 125.17 0.40194 21.11 0.43 134 46.35 0.40 74 70.73 0.40 14 94.52 0.40 6 102.34 0.39 66 125.55 0.38193 21.54 0.43 133 46.76 0.41 73 71.13 0.40 13 94.91 0.39 7 102.73 0.39 67 125.93 0.38192 21.97 0.43 132 47.18 0.42 72 71.53 0.40 12 95.30 0.39 8 103.12 0.39 68 126.32 0.39191 22.40 0.43 131 47.59 0.41 71 71.93 0.40 11 95.69 0.39 9 103.51 0.39 69 126.70 0.38190 22.83 0.43 130 48.00 0.41 70 72.33 0.40 10 96.09 0.40 10 103.90 0.39 70 127.08 0.38189 23.26 0.43 129 48.41 0.41 69 72.73 0.40 9 96.48 0.39 11 104.29 0.39 71 127.46 0.38188 23.69 0.43 128 48.82 0.41 68 73.13 0.40 8 96.87 0.39 12 104.68 0.39 72 127.85 0.39187 24.12 0.43 127 49.23 0.41 67 73.53 0.40 7 97.26 0.39 13 105.07 0.39 73 128.23 0.38186 24.55 0.43 126 49.64 0.41 66 73.93 0.40 6 97.65 0.39 14 105.46 0.39 74 128.61 0.38185 24.97 0.42 125 50.06 0.42 65 74.33 0.40 5 98.04 0.39 15 105.85 0.39 75 128.99 0.38184 25.39 0.42 124 50.47 0.41 64 74.73 0.40 4 98.44 0.40 16 106.24 0.39 76 129.38 0.39183 25.82 0.43 123 50.88 0.41 63 75.13 0.40 3 98.83 0.39 17 106.63 0.39 77 129.76 0.38182 26.25 0.43 122 51.29 0.41 62 75.53 0.40 2 99.22 0.39 18 107.02 0.39 78 130.14 0.38181 26.67 0.42 121 51.70 0.41 61 75.93 0.40 1 99.61 0.39 19 107.40 0.38 79 130.52 0.38180 27.10 0.43 120 52.11 0.41 60 76.33 0.40 20 107.79 0.39 80 130.90 0.38179 27.52 0.42 119 52.52 0.41 59 76.73 0.40 21 108.18 0.39 81 131.28 0.38178 27.95 0.43 118 52.92 0.40 58 77.13 0.40 22 108.57 0.39 82 131.67 0.39177 28.37 0.42 117 53.33 0.41 57 77.52 0.39 23 108.96 0.39 83 132.05 0.38176 28.80 0.43 116 53.74 0.41 56 77.92 0.40 24 109.35 0.39 84 132.43 0.38175 29.22 0.42 115 54.15 0.41 55 78.32 0.40 25 109.73 0.38 85 132.81 0.38174 29.65 0.43 114 54.56 0.41 54 78.72 0.40 26 110.12 0.39 86 133.19 0.38173 30.07 0.42 113 54.97 0.41 53 79.11 0.39 27 110.51 0.39 87 133.57 0.38172 30.49 0.42 112 55.38 0.41 52 79.51 0.40 28 110.90 0.39 88 133.95 0.38171 30.92 0.43 111 55.78 0.40 51 79.91 0.40 29 111.28 0.38 89 134.33 0.38170 31.34 0.42 110 56.19 0.41 50 80.31 0.40 30 111.67 0.39 90 134.71 0.38169 31.76 0.42 109 56.60 0.41 49 80.70 0.39 31 112.06 0.39 91 135.09 0.38168 32.18 0.42 108 57.00 0.40 48 81.10 0.40 32 112.45 0.39 92 135.47 0.38167 32.61 0.43 107 57.41 0.41 47 81.50 0.40 33 112.83 0.38 93 135.85 0.38166 33.03 0.42 106 57.82 0.41 46 81.89 0.39 34 113.22 0.39 94 136.23 0.38165 33.45 0.42 105 58.22 0.40 45 82.29 0.40 35 113.61 0.39 95 136.61 0.38164 33.86 0.41 104 58.63 0.41 44 82.69 0.40 36 113.99 0.38 96 136.99 0.38163 34.28 0.42 103 59.04 0.41 43 83.08 0.39 37 114.38 0.39 97 137.37 0.38162 34.70 0.42 102 59.44 0.40 42 83.48 0.40 38 114.77 0.39 98 137.75 0.38161 35.12 0.42 101 59.85 0.41 41 83.88 0.40 39 115.15 0.38 99 138.13 0.38160 35.54 0.42 100 60.26 0.41 40 84.27 0.39 40 115.54 0.39 100 138.51 0.38159 35.96 0.42 99 60.67 0.41 39 84.67 0.40 41 115.93 0.39 101 138.89 0.38158 36.38 0.42 98 61.07 0.40 38 85.06 0.39 42 116.31 0.38 102 139.27 0.38157 36.80 0.42 97 61.48 0.41 37 85.46 0.40 43 116.70 0.39 103 139.65 0.38156 37.22 0.42 96 61.87 0.41 36 85.85 0.39 44 117.08 0.38 104 140.03 0.38155 37.63 0.41 95 62.29 0.42 35 86.25 0.40 45 117.47 0.39 105 140.39 0.36154 38.05 0.42 94 62.69 0.40 34 86.64 0.39 46 117.85 0.38 106 140.77 0.38153 38.47 0.42 93 63.10 0.41 33 87.04 0.40 47 118.24 0.39 107 141.15 0.38152 38.89 0.42 92 63.50 0.40 32 87.43 0.39 48 118.62 0.38 108 141.53 0.38151 39.31 0.42 91 63.91 0.41 31 87.83 0.40 49 119.01 0.39 109 141.91 0.38150 39.72 0.41 90 64.30 0.39 30 88.22 0.39 50 119.40 0.39 110 142.29 0.38149 40.14 0.42 89 64.70 0.40 29 88.62 0.40 51 119.78 0.38 111 142.66 0.37148 40.56 0.42 88 65.11 0.41 28 89.01 0.39 52 120.16 0.38 112 143.04 0.38147 40.97 0.41 87 65.51 0.40 27 89.40 0.39 53 120.55 0.39 113 143.42 0.38146 41.39 0.42 86 65.91 0.40 26 89.80 0.40 54 120.93 0.38 114 143.80 0.38145 41.80 0.41 85 66.31 0.40 25 90.19 0.39 55 121.32 0.39 115 144.18 0.38144 42.22 0.42 84 66.72 0.41 24 90.59 0.40 56 121.70 0.38 116 144.56 0.38143 42.64 0.42 83 67.12 0.40 23 90.98 0.39 57 122.09 0.39 117 144.94 0.38142 43.05 0.41 82 67.52 0.40 22 91.37 0.39 58 122.47 0.38 118 145.32 0.38141 43.46 0.41 81 67.92 0.40 21 91.77 0.40 59 122.86 0.39 119 145.69 0.37

RTD Temperaturevs. Resistance TableFor European Curve, Alpha = .00385, ITS-90 1° Celsius Increments

Note: At 100°C, resistance is 138.50 ohms. (DIN 43 760)

Z-253



+120 146.07 0.38 +180 168.48 0.37 +240 190.47 0.36 +300 212.05 0.36 +360 233.21 0.35 +420 253.96 0.34121 146.45 0.38 181 168.85 0.37 241 190.83 0.36 301 212.40 0.35 361 233.56 0.35 421 254.30 0.34122 146.82 0.37 182 169.22 0.37 242 191.20 0.37 302 212.76 0.36 362 233.91 0.35 422 254.65 0.35123 147.20 0.38 183 169.59 0.37 243 191.56 0.36 303 213.12 0.36 363 234.26 0.35 423 254.99 0.34124 147.58 0.38 184 169.96 0.37 244 191.92 0.36 304 213.47 0.35 364 234.60 0.36 424 255.33 0.34125 147.95 0.37 185 170.33 0.37 245 192.28 0.36 305 213.83 0.36 365 234.95 0.35 425 255.67 0.34126 148.33 0.38 186 170.69 0.36 246 192.66 0.38 306 214.19 0.36 366 235.30 0.35 426 256.01 0.34127 148.71 0.38 187 171.06 0.37 247 193.02 0.36 307 214.55 0.36 367 235.65 0.35 427 256.35 0.34128 149.08 0.37 188 171.43 0.37 248 193.38 0.36 308 214.90 0.35 368 236.00 0.35 428 256.70 0.35129 149.46 0.38 189 171.80 0.37 249 193.74 0.36 309 215.26 0.36 369 236.35 0.35 429 257.04 0.34130 149.83 0.37 190 172.17 0.37 250 194.10 0.36 310 215.61 0.35 370 236.70 0.35 430 257.38 0.34131 150.21 0.38 191 172.54 0.37 251 194.47 0.37 311 215.97 0.36 371 237.05 0.35 431 257.72 0.34132 150.58 0.37 192 172.91 0.37 252 194.83 0.36 312 216.32 0.35 372 237.40 0.35 432 258.06 0.34133 150.96 0.38 193 173.27 0.36 253 195.19 0.36 313 216.68 0.36 373 237.75 0.35 433 258.40 0.34134 151.34 0.38 194 173.64 0.37 254 195.55 0.36 314 217.03 0.35 374 238.09 0.34 434 258.74 0.34135 151.71 0.37 195 174.01 0.37 255 195.90 0.35 315 217.39 0.36 375 238.44 0.35 435 259.08 0.34136 152.09 0.38 196 174.39 0.38 256 196.26 0.36 316 217.73 0.34 376 238.79 0.35 436 259.42 0.34137 152.46 0.37 197 174.75 0.36 257 196.62 0.36 317 218.08 0.35 377 239.14 0.35 437 259.76 0.34138 152.84 0.38 198 175.12 0.37 258 196.98 0.36 318 218.44 0.36 378 239.48 0.34 438 260.10 0.34139 153.21 0.37 199 175.49 0.37 259 197.35 0.37 319 218.79 0.35 379 239.83 0.35 439 260.44 0.34140 153.58 0.37 200 175.86 0.37 260 197.71 0.36 320 219.15 0.36 380 240.18 0.35 440 260.78 0.34141 153.95 0.37 201 176.23 0.37 261 198.07 0.36 321 219.50 0.35 381 240.52 0.34 441 261.12 0.34142 154.32 0.37 202 176.59 0.36 262 198.43 0.36 322 219.85 0.35 382 240.87 0.35 442 261.46 0.34143 154.71 0.39 203 176.96 0.37 263 198.79 0.36 323 220.21 0.36 383 241.22 0.35 443 261.80 0.34144 155.08 0.37 204 177.33 0.37 264 199.15 0.36 324 220.56 0.35 384 241.56 0.34 444 262.14 0.34145 155.46 0.38 205 177.70 0.37 265 199.51 0.36 325 220.91 0.35 385 241.91 0.35 445 262.48 0.34146 155.83 0.37 206 178.06 0.36 266 199.87 0.36 326 221.27 0.36 386 242.25 0.34 446 262.83 0.35147 156.21 0.38 207 178.43 0.37 267 200.23 0.36 327 221.62 0.35 387 242.60 0.35 447 263.17 0.34148 156.58 0.37 208 178.80 0.37 268 200.59 0.36 328 221.97 0.35 388 242.95 0.35 448 263.50 0.33149 156.96 0.38 209 179.16 0.36 269 200.95 0.36 329 222.32 0.35 389 243.29 0.34 449 263.84 0.34150 157.33 0.37 210 179.53 0.37 270 201.31 0.36 330 222.68 0.36 390 243.64 0.35 450 264.18 0.34151 157.71 0.38 211 179.90 0.37 271 201.67 0.36 331 223.03 0.35 391 243.98 0.34 451 264.52 0.34152 158.08 0.37 212 180.26 0.36 272 202.03 0.36 332 223.38 0.35 392 244.33 0.35 452 264.86 0.34153 158.45 0.37 213 180.63 0.37 273 202.38 0.35 333 223.73 0.35 393 244.67 0.34 453 265.20 0.34154 158.83 0.38 214 180.99 0.36 274 202.74 0.36 334 224.09 0.36 394 245.02 0.35 454 265.54 0.34155 159.20 0.37 215 181.36 0.37 275 203.10 0.36 335 224.45 0.36 395 245.36 0.34 455 265.87 0.33156 159.56 0.36 216 181.73 0.37 276 203.46 0.36 336 224.80 0.35 396 245.71 0.35 456 266.21 0.34157 159.94 0.38 217 182.09 0.36 277 203.82 0.36 337 225.15 0.35 397 246.05 0.34 457 266.55 0.34158 160.31 0.37 218 182.46 0.37 278 204.18 0.36 338 225.50 0.35 398 246.40 0.35 458 266.89 0.34159 160.68 0.37 219 182.82 0.36 279 204.54 0.36 339 225.85 0.35 399 246.74 0.34 459 267.22 0.33160 161.05 0.37 220 183.19 0.37 280 204.90 0.36 340 226.21 0.36 400 247.09 0.35 460 267.56 0.34161 161.43 0.38 221 183.55 0.36 281 205.25 0.35 341 226.56 0.35 401 247.43 0.34 461 267.90 0.34162 161.80 0.37 222 183.92 0.37 282 205.61 0.36 342 226.91 0.35 402 247.78 0.35 462 268.24 0.34163 162.17 0.37 223 184.28 0.36 283 205.97 0.36 343 227.26 0.35 403 248.12 0.34 463 268.57 0.33164 162.54 0.37 224 184.65 0.37 284 206.33 0.36 344 227.61 0.35 404 248.46 0.34 464 268.91 0.34165 162.91 0.37 225 185.01 0.36 285 206.70 0.37 345 227.96 0.35 405 248.81 0.35 465 269.25 0.34166 163.28 0.37 226 185.38 0.37 286 207.05 0.35 346 228.31 0.35 406 249.15 0.34 466 269.58 0.33167 163.66 0.38 227 185.74 0.36 287 207.41 0.36 347 228.66 0.35 407 249.50 0.35 467 269.92 0.34168 164.03 0.37 228 186.11 0.37 288 207.77 0.36 348 229.01 0.35 408 249.84 0.34 468 270.26 0.34169 164.40 0.37 229 186.47 0.36 289 208.13 0.36 349 229.36 0.35 409 250.18 0.34 469 270.59 0.33170 164.77 0.37 230 186.84 0.37 290 208.48 0.35 350 229.72 0.34 410 250.53 0.35 470 270.93 0.34171 165.14 0.37 231 187.20 0.36 291 208.84 0.36 351 230.07 0.35 411 250.89 0.34 471 271.27 0.34172 165.51 0.37 232 187.56 0.36 292 209.20 0.36 352 230.42 0.35 412 251.21 0.34 472 271.60 0.33173 165.88 0.37 233 187.93 0.37 293 209.55 0.35 353 230.77 0.35 413 251.55 0.34 473 271.94 0.34174 166.25 0.37 234 188.29 0.36 294 209.91 0.36 354 231.12 0.35 414 251.90 0.35 474 272.27 0.33175 166.62 0.37 235 188.65 0.36 295 210.27 0.36 355 231.47 0.35 415 252.24 0.34 475 272.61 0.34176 167.00 0.38 236 189.02 0.37 296 210.62 0.35 356 231.81 0.36 416 252.59 0.35 476 272.95 0.34177 167.37 0.37 237 189.38 0.36 297 210.98 0.36 357 232.16 0.35 417 252.94 0.35 477 273.28 0.33178 167.74 0.37 238 189.74 0.36 298 211.34 0.36 358 232.51 0.35 418 253.28 0.34 478 273.62 0.34179 168.11 0.37 239 190.11 0.37 299 211.69 0.35 359 232.86 0.35 419 253.62 0.34 479 273.95 0.33


Z-254

Z



+480 274.29 0.34 +542 294.87 0.33 +604 315.00 0.32 +666 334.68 0.32 +728 353.91 0.30 +790 372.71 0.30481 274.62 0.33 543 295.20 0.33 605 315.32 0.32 667 334.99 0.31 729 354.22 0.31 791 373.01 0.30482 274.96 0.34 544 295.53 0.33 606 315.64 0.32 668 335.31 0.32 730 354.53 0.31 792 373.31 0.30483 275.29 0.33 545 295.85 0.32 607 315.96 0.32 669 335.62 0.31 731 354.83 0.30 793 373.61 0.30484 275.63 0.34 546 296.18 0.33 608 316.28 0.32 670 335.93 0.31 732 355.14 0.31 794 373.91 0.30485 275.96 0.33 547 296.51 0.33 609 316.60 0.32 671 336.25 0.32 733 355.44 0.30 795 374.21 0.30486 276.31 0.34 548 296.84 0.33 610 316.92 0.32 672 336.56 0.31 734 355.75 0.31 796 374.51 0.30487 276.64 0.33 549 297.16 0.32 611 317.24 0.32 673 336.87 0.31 735 356.06 0.31 797 374.80 0.29488 276.97 0.33 550 297.49 0.33 612 317.56 0.32 674 337.18 0.31 736 356.37 0.31 798 374.10 0.30489 277.31 0.34 551 297.82 0.33 613 317.88 0.32 675 337.50 0.32 737 356.68 0.31 799 375.40 0.30490 277.64 0.33 552 298.14 0.32 614 318.20 0.32 676 337.81 0.31 738 356.98 0.30 800 375.70 0.30491 277.98 0.34 553 298.47 0.33 615 318.52 0.32 677 338.12 0.31 739 357.29 0.31 801 376.00 0.30492 278.31 0.33 554 298.80 0.33 616 318.85 0.33 678 338.43 0.31 740 357.59 0.30 802 376.29 0.29493 278.64 0.33 555 299.12 0.32 617 319.17 0.32 679 338.75 0.32 741 357.90 0.31 803 376.59 0.30494 278.98 0.34 556 299.45 0.33 618 319.49 0.32 680 339.06 0.31 742 358.20 0.30 804 376.89 0.30495 279.31 0.33 557 299.78 0.33 619 319.81 0.32 681 339.37 0.31 743 358.51 0.31 805 377.19 0.30496 279.64 0.33 558 300.10 0.32 620 320.12 0.31 682 339.68 0.31 744 358.81 0.30 806 377.49 0.30497 279.98 0.34 559 300.43 0.33 621 320.44 0.32 683 339.99 0.31 745 359.12 0.31 807 377.79 0.30498 280.31 0.33 560 300.75 0.32 622 320.76 0.32 684 340.30 0.31 746 359.42 0.30 808 378.09 0.30499 280.64 0.33 561 301.08 0.33 623 321.08 0.32 685 340.62 0.32 747 359.72 0.30 809 378.39 0.30500 280.98 0.34 562 301.41 0.33 624 321.40 0.32 686 340.94 0.32 748 360.03 0.31 810 378.68 0.29501 281.31 0.33 563 301.73 0.32 625 321.72 0.32 687 341.25 0.31 749 360.33 0.30 811 378.98 0.30502 281.64 0.33 564 302.06 0.33 626 322.03 0.31 688 341.55 0.30 750 360.64 0.31 812 379.28 0.30503 281.97 0.33 565 302.38 0.32 627 322.34 0.31 689 341.87 0.32 751 360.94 0.30 813 379.57 0.29504 282.31 0.34 566 302.71 0.33 628 322.66 0.32 690 342.18 0.31 752 361.24 0.30 814 379.87 0.30505 282.64 0.33 567 303.03 0.32 629 322.98 0.32 691 342.49 0.31 753 361.55 0.31 815 380.17 0.30506 282.97 0.33 568 303.36 0.33 630 323.30 0.32 692 342.80 0.31 754 361.85 0.30 816 380.46 0.29507 283.30 0.33 569 303.68 0.32 631 323.61 0.31 693 343.11 0.31 755 362.15 0.30 817 380.76 0.30508 283.63 0.33 570 304.01 0.33 632 323.93 0.32 694 343.42 0.31 756 362.46 0.31 818 381.05 0.29509 283.97 0.34 571 304.33 0.32 633 324.25 0.32 695 343.73 0.31 757 362.76 0.30 819 381.35 0.30510 284.30 0.33 572 304.66 0.33 634 324.57 0.32 696 344.04 0.31 758 363.06 0.30 820 381.65 0.30511 284.63 0.33 573 304.98 0.32 635 324.88 0.31 697 344.35 0.31 759 363.36 0.30 821 381.94 0.29512 284.96 0.33 574 305.30 0.32 636 325.21 0.33 698 344.66 0.31 760 363.67 0.31 822 382.24 0.30513 285.29 0.33 575 305.63 0.33 637 325.53 0.32 699 344.97 0.31 761 363.97 0.30 823 382.53 0.29514 285.62 0.33 576 305.95 0.32 638 325.85 0.32 700 345.28 0.31 762 364.27 0.30 824 382.83 0.30515 285.95 0.33 577 306.28 0.33 639 326.16 0.31 701 345.59 0.31 763 364.57 0.30 825 383.12 0.29516 286.30 0.35 578 306.60 0.32 640 326.48 0.32 702 345.90 0.31 764 364.88 0.31 826 383.42 0.30517 286.63 0.33 579 306.92 0.32 641 326.79 0.31 703 346.21 0.31 765 365.18 0.30 827 383.71 0.29518 286.96 0.33 580 307.25 0.33 642 327.11 0.32 704 346.52 0.31 766 365.49 0.31 828 384.01 0.30519 287.29 0.33 581 307.57 0.32 643 327.43 0.32 705 346.83 0.31 767 365.79 0.30 829 384.30 0.29520 287.62 0.33 582 307.89 0.32 644 327.74 0.31 706 346.15 0.32 768 366.09 0.30 830 384.60 0.30521 287.95 0.33 583 308.22 0.33 645 328.06 0.32 707 347.46 0.31 769 366.40 0.31 831 384.89 0.29522 288.28 0.33 584 308.54 0.32 646 328.38 0.32 708 347.76 0.30 770 366.70 0.30 832 385.18 0.29523 288.61 0.33 585 308.86 0.32 647 328.69 0.31 709 348.07 0.31 771 367.00 0.30 833 385.48 0.30524 288.94 0.33 586 309.19 0.33 648 329.01 0.32 710 348.38 0.31 772 367.30 0.30 834 385.77 0.29525 289.27 0.33 587 309.51 0.32 649 329.32 0.31 711 348.69 0.31 773 367.60 0.30 835 386.07 0.30526 289.60 0.33 588 309.83 0.32 650 329.64 0.32 712 349.00 0.31 774 367.90 0.30 836 386.37 0.30527 289.93 0.33 589 310.15 0.32 651 329.95 0.31 713 349.31 0.31 775 368.20 0.30 837 386.66 0.29528 290.26 0.33 590 310.48 0.33 652 330.27 0.32 714 349.61 0.30 776 368.50 0.30 838 386.96 0.30529 290.59 0.33 591 310.80 0.32 653 330.58 0.31 715 349.92 0.31 777 368.81 0.31 839 387.25 0.29530 290.92 0.33 592 311.12 0.32 654 330.90 0.32 716 350.23 0.31 778 369.11 0.30 840 387.55 0.30531 291.25 0.33 593 311.45 0.33 655 331.21 0.31 717 350.54 0.31 779 369.41 0.30 841 387.84 0.29532 291.58 0.33 594 311.78 0.33 656 331.53 0.32 718 350.85 0.31 780 369.71 0.30 842 388.13 0.29533 291.90 0.32 595 312.10 0.32 657 331.84 0.31 719 351.15 0.30 781 370.01 0.30 843 388.42 0.29534 292.23 0.33 596 312.43 0.33 658 332.16 0.32 720 351.46 0.31 782 370.31 0.30 844 388.72 0.30535 292.56 0.33 597 312.75 0.32 659 332.47 0.31 721 351.77 0.31 783 370.61 0.30 845 389.01 0.29536 292.90 0.34 598 313.07 0.32 660 332.79 0.32 722 352.07 0.30 784 370.91 0.30 846 389.31 0.30537 293.23 0.33 599 313.39 0.32 661 333.10 0.31 723 352.38 0.31 785 371.21 0.30 847 389.61 0.30538 293.56 0.33 600 313.71 0.32 662 333.41 0.31 724 352.69 0.31 786 371.52 0.31 848 389.90 0.29539 293.89 0.33 601 314.04 0.33 663 333.73 0.32 725 352.99 0.30 787 371.82 0.30 849 390.19 0.29540 294.21 0.32 602 314.36 0.32 664 334.04 0.31 726 353.30 0.31 788 372.12 0.30 850 390.48 0.29541 294.54 0.33 603 314.68 0.32 665 334.36 0.32 727 353.61 0.31 789 372.41 0.29


Z-255

°C Ohms °C Ohms °C Ohms °C Ohms °C Ohms °C Ohms °C Ohms °C Ohms °C Ohms

-100 59.57 -38 84.80 24 109.51 86 133.75 148 157.53 210 180.86 272 203.74 334 226.17 396 248.16-99 59.98 -37 85.20 25 109.90 87 134.14 149 157.91 211 181.23 273 204.11 335 226.53 397 248.51-98 60.39 -36 85.60 26 110.30 88 134.52 150 158.29 212 181.61 274 204.47 336 226.89 398 248.86-97 60.80 -35 86.01 27 110.69 89 134.91 151 158.67 213 181.98 275 204.84 337 227.25 399 249.21-96 61.21 -34 86.41 28 111.09 90 135.30 152 159.05 214 182.35 276 205.20 338 227.61 400 249.56-95 61.63 -33 86.81 29 111.48 91 135.68 153 159.43 215 182.72 277 205.57 339 227.96 401 249.91-94 62.04 -32 87.21 30 111.88 92 136.07 154 159.81 216 183.09 278 205.93 340 228.32 402 250.26-93 62.45 -31 87.61 31 112.27 93 136.46 155 160.19 217 183.47 279 206.30 341 228.68 403 250.61-92 62.86 -30 88.01 32 112.66 94 136.84 156 160.57 218 183.84 280 206.66 342 229.04 404 250.96-91 63.27 -29 88.42 33 113.06 95 137.23 157 160.95 219 184.21 281 207.02 343 229.39 405 251.31-90 63.68 -28 88.82 34 113.45 96 137.62 158 161.33 220 184.58 282 207.39 344 229.75 406 251.66-89 64.09 -27 89.22 35 113.84 97 138.00 159 161.70 221 184.95 283 207.75 345 230.11 407 252.01-88 64.50 -26 89.62 36 114.24 98 138.39 160 162.08 222 185.32 284 208.12 346 230.46 408 252.36-87 64.91 -25 90.02 37 114.63 99 138.77 161 162.46 223 185.70 285 208.48 347 230.82 409 252.71-86 65.32 -24 90.42 38 115.02 100 139.16 162 162.84 224 186.07 286 208.85 348 231.18 410 253.06-85 65.73 -23 90.82 39 115.42 101 139.55 163 163.22 225 186.44 287 209.21 349 231.53 411 253.41-84 66.14 -22 91.22 40 115.81 102 139.93 164 163.60 226 186.81 288 209.57 350 231.89 412 253.76-83 66.55 -21 91.62 41 116.20 103 140.32 165 163.97 227 187.18 289 209.94 351 232.25 413 254.11-82 66.96 -20 92.02 42 116.59 104 140.70 166 164.35 228 187.55 290 210.30 352 232.60 414 254.46-81 67.36 -19 92.42 43 116.99 105 141.09 167 164.73 229 187.92 291 210.66 353 232.96 415 254.80-80 67.77 -18 92.82 44 117.38 106 141.47 168 165.11 230 188.29 292 211.03 354 233.31 416 255.15-79 68.18 -17 93.22 45 117.77 107 141.86 169 165.48 231 188.66 293 211.39 355 233.67 417 255.50-78 68.59 -16 93.62 46 118.16 108 142.24 170 165.86 232 189.03 294 211.75 356 234.03 418 255.85-77 69.00 -15 94.02 47 118.56 109 142.63 171 166.24 233 189.40 295 212.11 357 234.38 419 256.20-76 69.41 -14 94.42 48 118.95 110 143.01 172 166.62 234 189.77 296 212.48 358 234.74 420 256.55-75 69.81 -13 94.82 49 119.34 111 143.39 173 166.99 235 190.14 297 212.84 359 235.09 421 256.89-74 70.22 -12 95.22 50 119.73 112 143.78 174 167.37 236 190.51 298 213.20 360 235.45 422 257.24-73 70.63 -11 95.62 51 120.12 113 144.16 175 167.75 237 190.88 299 213.56 361 235.80 423 257.59-72 71.04 -10 96.02 52 120.51 114 144.55 176 168.12 238 191.25 300 213.93 362 236.16 424 257.94-71 71.44 -9 96.42 53 120.91 115 144.93 177 168.50 239 191.62 301 214.29 363 236.51 425 258.29-70 71.85 -8 96.81 54 121.30 116 145.31 178 168.88 240 191.99 302 214.65 364 236.87 426 258.63-69 72.26 -7 97.21 55 121.69 117 145.70 179 169.25 241 192.36 303 215.01 365 237.22 427 258.98-68 72.66 -6 97.61 56 122.08 118 146.08 180 169.63 242 192.73 304 215.37 366 237.58 428 259.33-67 73.07 -5 98.01 57 122.47 119 146.47 181 170.00 243 193.09 305 215.74 367 237.93 429 259.67-66 73.48 -4 98.41 58 122.86 120 146.85 182 170.38 244 193.46 306 216.10 368 238.28 430 260.02-65 73.88 -3 98.81 59 123.25 121 147.23 183 170.76 245 193.83 307 216.46 369 238.64 431 260.37-64 74.29 -2 99.20 60 123.64 122 147.61 184 171.13 246 194.20 308 216.82 370 238.99 432 260.72-63 74.70 -1 99.60 61 124.03 123 148.00 185 171.51 247 194.57 309 217.18 371 239.35 433 261.06-62 75.10 0 100.00 62 124.42 124 148.38 186 171.88 248 194.94 310 217.54 372 239.70 434 261.41-61 75.51 1 100.40 63 124.81 125 148.76 187 172.26 249 195.31 311 217.90 373 240.05 435 261.75-60 75.91 2 100.80 64 125.20 126 149.15 188 172.63 250 195.67 312 218.26 374 240.41 436 262.10-59 76.32 3 101.19 65 125.59 127 149.53 189 173.01 251 196.04 313 218.63 375 240.76 437 262.45-58 76.72 4 101.59 66 125.98 128 149.91 190 173.38 252 196.41 314 218.99 376 241.11 438 262.79-57 77.13 5 101.99 67 126.37 129 150.29 191 173.76 253 196.78 315 219.35 377 241.47 439 263.14-56 77.53 6 102.38 68 126.76 130 150.67 192 174.13 254 197.14 316 219.71 378 241.82 440 263.49-55 77.94 7 102.78 69 127.15 131 151.06 193 174.51 255 197.51 317 220.07 379 242.17 441 263.83-54 78.34 8 103.18 70 127.54 132 151.44 194 174.88 256 197.88 318 220.43 380 242.53 442 264.18-53 78.75 9 103.57 71 127.93 133 151.82 195 175.26 257 198.25 319 220.79 381 242.88 443 264.52-52 79.15 10 103.97 72 128.32 134 152.20 196 175.63 258 198.61 320 221.15 382 243.23 444 264.87-51 79.56 11 104.37 73 128.71 135 152.58 197 176.01 259 198.98 321 221.51 383 243.58 445 265.21-50 79.96 12 104.76 74 129.09 136 152.96 198 176.38 260 199.35 322 221.87 384 243.94 446 265.56-49 80.36 13 105.16 75 129.48 137 153.35 199 176.75 261 199.71 323 222.23 385 244.29 447 265.90-48 80.77 14 105.56 76 129.87 138 153.73 200 177.13 262 200.08 324 222.59 386 244.64 448 266.25-47 81.17 15 105.95 77 130.26 139 154.11 201 177.50 263 200.45 325 222.94 387 244.99 449 266.59-46 81.58 16 106.35 78 130.65 140 154.49 202 177.88 264 200.81 326 223.30 388 245.35 450 266.94-45 81.98 17 106.74 79 131.04 141 154.87 203 178.25 265 201.18 327 223.66 389 245.70 451 267.28-44 82.38 18 107.14 80 131.42 142 155.25 204 178.62 266 201.55 328 224.02 390 246.05 452 267.63-43 82.79 19 107.53 81 131.81 143 155.63 205 179.00 267 201.91 329 224.38 391 246.40 453 267.97-42 83.19 20 107.93 82 132.20 144 156.01 206 179.37 268 202.28 330 224.74 392 246.75 454 268.31-41 83.59 21 108.32 83 132.59 145 156.39 207 179.74 269 202.64 331 225.10 393 247.10 455 268.66-40 83.99 22 108.72 84 132.98 146 156.77 208 180.12 270 203.01 332 225.46 394 247.46 456 269.00-39 84.40 23 109.11 85 133.36 147 157.15 209 180.49 271 203.38 333 225.81 395 247.81 457 269.35

RTD Temperaturevs. Resistance TableFor American Curve, Alpha = .00392 1° Celsius Increments

Z-256

Z

Part NO. 44004 44005 44007 44006 44008 PART NO. 44004 44005 44007 44006 4400844033 44030 44034 44031 44032 44033 44030 44034 44031 44032

Ω @25°C 2252 3000 5000 10,000 30,000 Ω @25°C 2252 3000 5000 10,000 30,000BLACK BLACK BLACK BLACK BLACK BLACK BLACK BLACK BLACK BLACK

BODY ORANGE ORANGE ORANGE ORANGE ORANGE BODY ORANGE ORANGE ORANGE ORANGE ORANGEYELLOW GREEN VIOLET BLUE GRAY YELLOW GREEN VIOLET BLUE GRAY

END ORANGE BLACK YELLOW BROWN RED END ORANGE BLACK YELLOW BROWN REDTEMP. °C RESISTANCE Ω TEMP. °C RESISTANCE Ω

- 80 1660K 2211K 3685K 3558K -20 21.87K 29.13K 48.56K 78.91K 271.2K79 1518K 2022K 3371K 3296K 19 20.64K 27.49K 45.83K 74.91K 256.5K78 1390K 1851K 3086K 3055K 18 19.48K 25.95K 43.27K 71.13K 242.8K77 1273K 1696K 2827K 2833K 17 18.40K 24.51K 40.86K 67.57K 229.8K76 1167K 1555K 2592K 2629K 16 17.39K 23.16K 38.61K 64.20K 217.6K75 1071K 1426K 2378K 2440K 15 16.43K 21.89K 36.49K 61.02K 206.2K74 982.8K 1309K 2182K 2266K 14 15.54K 20.70K 34.50K 58.01K 195.4K73 902.7K 1202K 2005K 2106K 13 14.70K 19.58K 32.63K 55.17K 185.2K72 829.7K 1105K 1843K 1957K 12 13.91K 18.52K 30.88K 52.48K 175.6K71 763.1K 1016K 1695K 1821K 11 13.16K 17.53K 29.23K 49.94K 166.6K

-70 702.3K 935.4K 1560K 1694K -10 12.46K 16.60K 27.67K 47.54K 158.0K69 646.7K 861.4K 1436K 1577K 9 11.81K 15.72K 26.21K 45.27K 150.0K68 595.9K 793.7K 1323K 1469K 8 11.19K 14.90K 24.83K 43.11K 142.4K67 549.4K 731.8K 1220K 1369K 7 10.60K 14.12K 23.54K 41.07K 135.2K66 506.9K 675.2K 1126K 1276K 6 10.05K 13.39K 22.32K 39.14K 128.5K65 467.9K 623.3K 1039K 1190K 5 9534 12.70K 21.17K 37.31K 122.1K 64 432.2K 575.7K 959.9K 1111K 4 9046 12.05K 20.08K 35.57K 116.0K63 399.5K 532.1K 887.2K 1037K 3 8586 11.44K 19.06K 33.93K 110.3K62 369.4K 492.1K 820.5K 968.4K 2 8151 10.86K 18.10K 32.37K 104.9K61 341.8K 455.3K 759.2K 904.9K - 1 7741 10.31K 17.19K 30.89K 99.80K

-60 316.5K 421.5K 702.9K 845.9K 0 7355 9796 16.33K 29.49K 94.98K59 293.2K 390.5K 651.1K 791.1K + 1 6989 9310 15.52K 28.15K 90.41K58 271.7K 361.9K 603.5K 740.2K 2 6644 8851 14.75K 26.89K 86.09K57 252.0K 335.7K 559.7K 692.8K 3 6319 8417 14.03K 25.69K 81.99K56 233.8K 311.5K 519.4K 648.8K 4 6011 8006 13.34K 24.55K 78.11K55 217.1K 289.2K 482.2K 607.8K 5 5719 7618 12.70K 23.46K 74.44K54 201.7K 268.6K 447.9K 569.6K 6 5444 7252 12.09K 22.43K 70.96K53 187.4K 249.7K 416.3K 534.1K 7 5183 6905 11.51K 21.45K 67.66K52 174.3K 232.2K 387.1K 501.0K 8 4937 6576 10.96K 20.52K 64.53K51 162.2K 216.0K 360.2K 470.1K 9 4703 6265 10.44K 19.63K 61.56K

-50 151.0K 201.1K 335.3K 441.3K +10 4482 5971 9951 18.79K 58.75K49 140.6K 187.3K 312.3K 414.5K 11 4273 5692 9486 17.98K 56.07K48 131.0K 174.5K 291.0K 389.4K 12 4074 5427 9046 17.22K 53.54K47 122.1K 162.7K 271.3K 366.0K 13 3886 5177 8628 16.49K 51.13K46 113.9K 151.7K 253.0K 344.1K 14 3708 4939 8232 15.79K 48.84K45 106.3K 141.6K 236.2K 323.7K 15 3539 4714 7857 15.13K 46.67K44 99.26K 132.2K 220.5K 304.6K 16 3378 4500 7500 14.50K 44.60K43 92.72K 123.5K 205.9K 286.7K 17 3226 4297 7162 13.90K 42.64K42 86.65K 115.4K 192.5K 270.0K 18 3081 4105 6841 13.33K 40.77K41 81.02K 107.9K 180.0K 254.4K 19 2944 3922 6536 12.79K 38.99K

-40 75.79K 101.0K 168.3K 239.8K 884.6K + 20 2814 3748 6247 12.26K 37.30K39 70.93K 94.48K 157.5K 226.0K 830.9K 21 2690 3583 5972 11.77K 35.70K38 66.41K 88.46K 147.5K 213.2K 780.8K 22 2572 3426 5710 11.29K 34.17K37 62.21K 82.87K 138.2K 201.1K 733.9K 23 2460 3277 5462 10.84K 32.71K36 58.30K 77.66K 129.5K 189.8K 690.2K 24 2354 3135 5225 10.41K 31.32K35 54.66K 72.81K 121.4K 179.2K 649.3K 25 2252 3000 5000 10.00K 30.00K34 51.27K 68.30K 113.9K 169.3K 611.0K 26 2156 2872 4787 9605 28.74K33 48.11K 64.09K 106.9K 160.0K 575.2K 27 2064 2750 4583 9227 27.54K32 45.17K 60.17K 100.3K 151.2K 541.7K 28 1977 2633 4389 8867 26.40K31 42.42K 56.51K 94.22K 143.0K 510.4K 29 1894 2523 4204 8523 25.31K

-30 39.86K 53.10K 88.53K 135.2K 481.0K + 30 1815 2417 4029 8194 24.27K29 37.47K 49.91K 83.22K 127.9K 453.5K 31 1739 2317 3861 7880 23.28K28 35.24K 46.94K 78.26K 121.1K 427.7K 32 1667 2221 3702 7579 22.33K27 33.15K 44.16K 73.62K 114.6K 403.5K 33 1599 2130 3549 7291 21.43K26 31.20K 41.56K 69.29K 108.6K 380.9K 34 1533 2042 3404 7016 20.57K25 29.38K 39.13K 65.24K 102.9K 359.6K 35 1471 1959 3266 6752 19.74K24 27.67K 36.86K 61.45K 97.49K 339.6K 36 1412 1880 3134 6500 18.96K23 26.07K 34.73K 57.90K 92.43K 320.9K 37 1355 1805 3008 6258 18.21K22 24.58K 32.74K 54.58K 87.66K 303.3K 38 1301 1733 2888 6026 17.49K21 23.18K 30.87K 51.47K 83.16K 286.7K + 39 1249 1664 2773 5805 16.80K

Note: Data in black refer to thermistors with ±0.2°C interchangeability. Data in brown refer to thermistors with ±0.1°C interchangeability. Temperature/resistance figures are the same for both types.Note: Only thermistors with ±0.2°C interchangeability are available encased in Teflon as standard parts. For Part No. of Teflon encased thermistors add 100 to part No. of ±0-2°C interchangeable thermistor. Example: 44005 is a standard thermistor. 44105 is a Teflon encased thermistor with the same resistance values.

Thermistor Resistance vs. Temperature

Z-257

Part NO. 44004 44005 44007 44006 44008 PART NO. 44004 44005 44007 44006 4400844033 44030 44034 44031 44032 44033 44030 44034 44031 44032

Ω @25°C 2252 3000 5000 10,000 30,000 Ω @25°C 2252 3000 5000 10,000 30,000BLACK BLACK BLACK BLACK BLACK BLACK BLACK BLACK BLACK BLACK

BODY ORANGE ORANGE ORANGE ORANGE ORANGE BODY ORANGE ORANGE ORANGE ORANGE ORANGEYELLOW GREEN VIOLET BLUE GRAY YELLOW GREEN VIOLET BLUE GRAY

END ORANGE BLACK YELLOW BROWN RED END ORANGE BLACK YELLOW BROWN REDTEMP. °C RESISTANCE Ω TEMP. °C RESISTANCE Ω

+40 1200 1598 2663 5592 16.15K +100 152.8 203.8 339.6 816.8 206941 1152 1535 2559 5389 15.52K 101 148.4 197.9 329.8 794.6 200942 1107 1475 2459 5193 14.92K 102 144.2 192.2 320.4 773.1 195043 1064 1418 2363 5006 14.35K 103 140.1 186.8 311.3 752.3 189444 1023 1363 2272 4827 13.80K 104 136.1 181.5 302.5 732.1 184045 983.8 1310 2184 4655 13.28K 105 132.3 176.4 294.0 712.6 178846 946.2 1260 2101 4489 12.77K 106 128.6 171.4 285.7 693.6 173747 910.2 1212 2021 4331 12.29K 107 125.0 166.7 277.8 675.3 168848 875.8 1167 1944 4179 11.83K 108 121.6 162.0 270.1 657.5 164049 842.8 1123 1871 4033 11.39K 109 118.2 157.6 262.6 640.3 1594

+50 811.3 1081 1801 3893 10.97K +110 115.0 153.2 255.4 623.5 155051 781.1 1040 1734 3758 10.57K 111 111.8 149.0 248.4 607.3 150752 752.2 1002 1670 3629 10.18K 112 108.8 145.0 241.6 591.6 146553 724.5 965.0 1608 3504 9807 113 105.8 141.1 235.1 576.4 142554 697.9 929.6 1549 3385 9450 114 103.0 137.2 228.7 561.6 138655 672.5 895.8 1493 3270 9109 115 100.2 133.6 222.6 547.3 134856 648.1 863.3 1439 3160 8781 116 97.6 130.0 216.7 533.4 131157 624.8 832.2 1387 3054 8467 117 95.0 126.5 210.9 519.9 127658 602.4 802.3 1337 2952 8166 118 92.5 123.2 205.3 506.8 124159 580.9 773.7 1290 2854 7876 119 90.0 119.9 199.9 494.1 1208

+60 560.3 746.3 1244 2760 7599 +120 87.7 116.8 194.7 481.8 117661 540.5 719.9 1200 2669 7332 121 85.4 113.8 189.6 469.8 114562 521.5 694.7 1158 2582 7076 122 83.2 110.8 184.7 458.2 111463 503.3 670.4 1117 2497 6830 123 71.1 107.9 179.9 446.9 108564 485.8 647.1 1079 2417 6594 124 79.0 105.2 175.3 435.9 105765 469.0 624.7 1041 2339 6367 125 77.0 102.5 170.8 425.3 102966 452.9 603.3 1006 2264 6149 126 75.0 99.9 166.4 414.9 100267 437.4 582.6 971.1 2191 5940 127 73.1 97.3 162.2 404.9 976.368 422.5 562.9 938.0 2122 5738 128 71.3 94.9 158.1 395.1 951.169 408.2 543.7 906.3 2055 5545 129 69.5 92.5 154.1 385.6 926.7

+70 394.5 525.4 875.7 1990 5359 +130 67.8 90.2 150.3 376.4 903.071 381.2 507.8 846.4 1928 5180 131 66.1 87.9 146.5 367.4 880.072 368.5 490.9 818.3 1868 5007 132 64.4 85.7 142.9 358.7 857.773 356.2 474.7 791.2 1810 4842 133 62.9 83.6 139.4 350.3 836.174 344.5 459.0 765.1 1754 4682 134 61.3 81.6 136.0 342.0 815.075 333.1 444.0 740.0 1700 4529 135 59.8 79.6 132.6 334.0 794.676 322.3 429.5 715.9 1648 4381 136 58.4 77.6 129.4 326.3 774.877 311.8 415.6 692.7 1598 4239 137 57.0 75.8 126.3 318.7 755.678 301.7 402.2 670.3 1549 4102 138 55.6 73.9 123.2 311.3 736.979 292.0 389.3 648.8 1503 3970 139 54.3 72.2 120.3 304.2 718.8

+80 282.7 376.9 628.1 1458 3843 +140 53.0 70.4 117.4 297.2 701.281 273.7 364.9 608.2 1414 3720 141 51.7 68.8 114.6 290.4 684.182 265.0 353.4 588.9 1372 3602 142 50.5 67.1 111.9 283.8 667.583 256.7 342.2 570.4 1332 3489 143 49.3 65.5 109.2 277.4 651.384 248.6 331.5 552.6 1293 3379 144 48.2 64.0 106.7 271.2 635.685 240.9 321.2 535.4 1255 3273 145 47.0 62.5 104.2 265.1 620.386 233.4 311.3 518.8 1218 3172 146 45.9 61.1 101.8 259.2 605.587 226.2 301.7 502.8 1183 3073 147 44.9 59.6 99.40 253.4 591.188 219.3 292.4 487.4 1149 2979 148 43.8 58.3 97.10 247.8 577.189 212.6 283.5 472.6 1116 2887 149 42.8 56.9 94.87 242.3 563.5

+90 206.1 274.9 458.2 1084 2799 +150 41.9 55.6 92.70 237.0 550.291 199.9 266.6 444.4 1053 271492 193.9 258.6 431.0 1023 263293 188.1 250.9 418.2 994.2 255294 182.5 243.4 405.7 966.3 247695 177.1 236.2 393.7 939.3 240296 171.9 229.3 382.1 913.2 233197 166.9 222.6 370.9 887.9 226298 162.0 216.1 360.1 863.4 219599 157.3 209.8 349.7 839.7 2131

Note: Data in black refer to thermistors with ±0.2°C interchangeability.Data in blue refer to thermistors with 0.1°C interchangeability.Temperature/resistance figures are the same for both types.

Note: Only thermistors with ±0.2°C interchangeability are available encasedin Teflon as standard parts. For Part No. of Teflon encased thermistorsadd 100 to part No. of ±0.2°C interchangeable thermistors. Example:44005 is a standard thermistor. 44105 is a Teflon encased thermistorwith the same resistance values.

Thermistor Resistance vs. Temperature

Z-258

Z

T1 RESISTANCE VERSUS TEMPERATURE -30 to +100°C

TEMP°C RES TEMP°C RES TEMP°C RES TEMP°C RES TEMP°C RES

-30 106.2K 0 19.59K +30 4834 +60 1493 +90 549.829 99.82K + 1 18.62K 31 4634 61 1440 91 533.228 93.88K 2 17.70K 32 4442 62 1389 92 517.227 88.32K 3 16.83K 33 4260 63 1341 93 501.826 83.12K 4 16.01K 34 4084 64 1294 94 486.825 78.26K 5 15.24K 35 3918 65 1249 95 472.424 73.72K 6 14.50K 36 3760 66 1207 96 458.623 69.46K 7 13.81K 37 3610 67 1165 97 445.222 65.48K 8 13.15K 38 3466 68 1126 98 432.221 61.74K 9 12.53K 39 3328 69 1087 99 419.6

-20 58.26K +10 11.94K +40 3196 +70 1051 +100 407.619 54.98K 11 11.38K 41 3070 71 101618 51.90K 12 10.85K 42 2950 72 981.817 49.02K 13 10.35K 43 2836 73 949.416 46.32K 14 9878 44 2726 74 918.015 43.78K 15 9428 45 2620 75 888.014 41.40K 16 9000 46 2520 76 859.013 39.16K 17 8594 47 2424 77 831.212 37.04K 18 8210 48 2334 78 804.411 35.06K 19 7844 49 2246 79 773.6

-10 33.20K +20 7496 +50 2162 +80 753.89 31.49K 21 7166 51 2080 81 729.88 29.80K 22 6852 52 2004 82 706.87 28.24K 23 6554 53 1930 83 684.46 26.78K 24 6270 54 1859 84 663.05 25.40K 25 6000 55 1792 85 642.44 24.10K 26 5744 56 1727 86 622.63 22.88K 27 5500 57 1664 87 603.42 21.72K 28 5266 58 1605 88 584.8

-1 20.62K 29 5046 59 1547 89 567.0

T2 RESISTANCE VERSUS TEMPERATURE -30 to +100°C

TEMP°C RES TEMP°C RES TEMP°C RES TEMP°C RES TEMP°C RES

-30 481.0K 0 94.98K +30 24.27K +60 7599 +90 279929 453.5K +1 90.41 K 31 23.28K 61 7332 91 271428 427.7K 2 86.09K 32 22.33K 62 7076 92 263227 403.5K 3 81.99K 33 21.43K 63 6830 93 255226 380.9K 4 78.11 K 34 20.57K 64 6594 94 247625 359.6K 5 74.44K 35 19.74K 65 6367 95 240224 339.6K 6 70.96K 36 18.96K 66 6149 96 233123 320.9K 7 67.66K 37 18.21K 67 5940 97 226222 303.3K 8 64.53K 38 17.49K 68 5738 98 219521 286.7K 9 61.56K 39 16.80K 69 5545 99 2131

-20 271.2K +10 58.75K +40 16.15K +70 5359 +100 206919 256.5K 11 56.07K 41 15.52K 71 518018 242.8K 12 53.54K 42 14.92K 72 500717 229.8K 13 51.13K 43 14.35K 73 484216 217.6K 14 48.84K 44 13.80K 74 468215 206.2K 15 46.67K 45 13.28K 75 452914 195.4K 16 44.60K 46 12.77K 76 438113 185.2K 17 42.64K 47 12.29K 77 423912 175.6K 18 40.77K 48 11.83K 78 410211 166.6K 19 38.99K 49 11.39K 79 3970

-10 158.0K +20 37.30K +50 10.97K +80 38439 150.0K 21 35.70K 51 10.57K 81 37208 142.4K 22 34.17K 52 10.18K 80 36027 135.2K 23 32.71K 53 9807 83 34896 128.5K 24 31.32K 54 9450 84 33795 122.1 K 25 30.00K 55 9109 85 32734 116.0K 26 28.74K 56 8781 86 31723 110.3K 27 27.54K 57 8467 87 30732 104.9K 28 26.40K 58 8166 88 2979

-1 99.80K 29 25.31 K 59 7876 89 2887

These tables give the resistancevalues for T1 and T2 as defined onPage F-10 for the 44018 LinearResponse Thermistor which is usedin the Series 700 Linear ThermistorProbes. Resistance in ohms.Temperature in °C.

Resistance vs Temperature forSeries “700” Linear Thermistors

Z-259

Temperature Conversion Chart

°C = 5⁄9 (°F - 32) °F = 9⁄5°C + 32 TABLE EXAMPLE:Kelvin = °C + 273.15 Rankine = °F + 459.67 To Convert 1000°C to °F, look up 1000 and read left

To Convert 1000°F to °C, look up 1000 and read right

to °F From to °C to °F From to °C to °F From to °C to °F From to °C to °F From to °C

- -458 -272.22 - -308 -188.89 -252.4 -158 -105.56 +17.6 -8 -22.22 287.6 142 61.11- -456 -271.11 - -306 -187.78 -248.2 -156 -104.44 +21.2 -6 -21.11 291.2 144 62.22- -454 -270.00 - -304 -186.67 -245.2 -154 -103.33 +24.8 -4 -20.00 294.8 146 63.33- -452 -268.89 - -302 -185.56 -241.6 -152 -102.22 +28.4 -2 -18.89 298.4 140 64.44- -450 -267.78 - -300 -184.44 -238.0 -150 -101.11 +32.0 0 -17.78 302.0 150 65.56

- -448 -266.67 - -298 -183.33 -234.4 -148 -100.00 +35.6 2 -16.67 305.6 152 66.67- -446 -265.56 - -296 -182.22 -230.2 -146 -98.89 +39.2 4 -15.56 309.2 154 67.78- -444 -264.44 - -294 -181.11 -227.2 -144 -97.78 +42.8 6 -14.44 312.8 156 68.89- -442 -263.33 - -292 -180.00 -223.6 -142 -96.67 +46.4 8 -13.33 316.4 158 70.00- -440 -262.22 - -290 -178.89 -220.0 -140 -95.56 +50.0 10 -12.22 320.0 160 71.11

- -438 -261.11 - -288 -177.78 -216.4 -138 -94.44 +53.6 12 -11.11 323.6 162 72.22- -436 -260.00 - -286 -176.67 -212.8 -136 -93.33 +57.2 14 -10.00 327.2 164 73.33- -434 -258.89 - -284 -175.56 -209.2 -134 -92.22 +60.8 16 -8.89 330.8 166 74.44- -432 -257.78 - -282 -174.44 -205.6 -132 -91.11 +64.4 18 -7.78 334.4 168 75.56- -430 -256.67 - -280 -173.33 -202.0 -130 -90.00 +68.0 20 -6.67 338.0 170 76.67

- -428 -255.56 - -278 -172.22 -198.4 -128 -88.89 +71.6 22 -5.56 341.6 172 77.78- -426 -264.44 - -276 -171.11 -194.2 -126 -87.78 +75.2 24 -4.44 345.2 174 78.89- -424 -253.33 - -274 -170.00 -191.2 -124 -86.67 +78.8 26 -3.33 348.8 176 80.00- -422 -252.22 -457.6 -272 -168.89 -187.6 -122 -85.56 +82.4 28 -2.22 352.4 178 81.11- -420 -251.11 -454.0 -270 -167.78 -184.0 -120 -84.44 +86.0 30 -1.11 356.0 180 82.22

- -418 -250.00 -450.4 -268 -166.67 -180.4 -118 -83.33 +89.6 32 0.00 359.6 182 83.33- -416 -248.89 -446.8 -266 -165.56 -176.8 -116 -82.22 +93.2 34 1.11 363.2 184 84.44- -414 -247.78 -443.2 -264 -164.44 -173.2 -114 -81.11 +96.8 36 2.22 366.8 186 85.56- -412 -246.67 -439.6 -262 -163.33 -169.6 -112 -80.00 +100.4 38 3.33 370.4 188 86.67- -410 -245.56 -436.0 -260 -162.22 -166.0 -110 -78.89 +104.0 40 4.44 374.0 190 87.78

- -408 -244.44 -432.4 -258 -161.11 -162.4 -108 -77.78 107.6 42 5.56 377.6 192 88.89- -406 -243.33 -428.8 -256 -160.00 -158.8 -106 -76.67 111.2 44 6.67 381.2 194 90.00- -404 -242.22 -425.2 -254 -158.89 -155.2 -104 -75.56 114.2 46 7.78 384.8 196 91.11- -402 -241.11 -421.6 -252 -157.78 -151.6 -102 -74.44 118.4 48 8.89 388.4 198 92.22

-400 -240.00 -418.0 -250 -156.67 -148.0 -100 -73.33 122.0 50 10.00 392.0 200 93.33

- -398 -238.89 -414.4 -248 -155.56 -144.4 -98 -72.22 125.6 52 11.11 395.6 202 94.44- -396 -237.78 -410.8 -246 -154.44 -140.8 -96 -71.11 129.2 54 12.22 399.2 204 95.56- -394 -236.67 -407.2 -244 -153.33 -137.2 -94 -70.00 132.8 56 13.33 402.8 206 96.67- -392 -235.56 -403.6 -242 -152.22 -133.6 -92 -68.89 136.4 58 14.44 406.4 208 97.78- -390 -234.44 -400.0 -240 -151.11 -130.0 -90 -67.78 140.0 60 15.56 410.0 210 98.89

- -388 -233.33 -396.4 -238 -150.00 -126.4 -88 -66.67 143.6 62 16.67 413.6 212 100.00- -386 -232.22 -392.8 -236 -148.89 -122.2 -86 -65.56 147.2 64 17.78 417.2 214 101.11- -384 -231.11 -389.2 -234 -147.78 -119.2 -84 -64.44 150.8 66 18.89 420.8 216 102.22- -382 -230.00 -385.6 -232 -146.67 -115.6 -82 -63.33 154.4 68 20.00 424.4 218 103.33- -380 -228.89 -382.0 -230 -145.56 -112.0 -80 -62.22 158.0 70 21.11 428.0 220 104.44

- -378 -227.78 -378.4 -228 -144.44 -108.4 -78 -61.11 161.6 72 22.22 431.6 222 105.56- -376 -226.67 -374.8 -226 -143.33 -104.8 -76 -60.00 165.2 74 23.33 435.2 224 106.67- -374 -225.56 -371.2 -224 -142.22 -101.2 -74 -58.89 168.8 76 24.44 438.8 226 107.78- -372 -224.44 -367.6 -222 -141.11 -97.6 -72 -57.78 172.4 78 25.56 442.4 228 108.89- -370 -223.33 -364.0 -220 -140.00 -94.0 -70 -56.67 176.0 80 26.67 446.0 230 110.00

- -368 -222.22 -360.4 -218 -138.89 -90.4 -68 -55.56 179.6 82 27.78 449.6 232 111.11- -366 -221.11 -356.8 -216 -137.78 -86.8 -66 -54.44 183.2 84 28.89 453.2 234 112.22- -364 -220.00 -353.2 -214 -136.67 -83.2 -64 -53.33 186.8 86 30.00 456.8 236 113.33- -362 -218.89 -349.6 -212 -135.56 -79.6 -62 -52.22 190.4 88 31.11 460.4 238 114.44- -360 -217.78 -346.0 -210 -134.44 -76.0 -60 -51.11 194.0 90 32.22 464.0 240 115.56

- -358 -216.67 -342.4 -208 -133.33 -72.4 -58 -50.00 197.6 92 33.33 467.6 242 116.67- -356 -215.56 -338.8 -206 -132.22 -68.8 -56 -48.89 201.2 94 34.44 471.2 244 117.78- -354 -214.44 -335.2 -204 -131.11 -65.2 -54 -47.78 204.8 96 35.56 474.8 246 118.89- -352 -213.33 -331.6 -202 -130.00 -61.6 -52 -46.67 208.4 98 36.67 478.4 248 120.00- -350 -212.22 -328.0 -200 -128.89 -58.0 -50 -45.56 212.0 100 37.78 482.0 250 121.11

- -348 -211.11 -324.4 -198 -127.78 -54.4 -48 -44.44 215.6 102 38.89 485.6 252 122.22- -346 -210.00 -320.8 -196 -126.67 -50.8 -46 -43.33 219.2 104 40.00 489.2 254 123.33- -344 -208.89 -317.2 -194 -125.56 -47.2 -44 -42.22 222.8 106 41.11 492.8 256 124.44- -342 -207.78 -313.6 -192 -124.44 -43.6 -42 -41.11 226.4 108 42.22 496.4 258 125.56- -340 -206.67 -310.0 -190 -123.33 -40.0 -40 -40.00 230.0 110 43.33 500.0 260 126.67

- -338 -205.56 -306.4 -188 -122.22 -36.4 -38 -38.89 233.6 112 44.44 503.6 262 127.78- -336 -204.44 -302.8 -186 -121.11 -32.8 -36 -37.78 237.2 114 45.56 507.2 264 128.89- -334 -203.33 -299.2 -184 -120.00 -29.2 -34 -36.67 240.2 116 46.67 510.8 266 130.00- -332 -202.22 -295.6 -182 -118.89 -25.6 -32 -35.56 244.4 118 47.78 514.4 268 131.11- -330 -201.11 -292.0 -180 -117.78 -22.0 -30 -34.44 248.0 120 48.89 518.0 270 132.22

- -328 -200.00 -288.4 -178 -116.67 -18.4 -28 -33.33 251.6 122 50.00 521.6 272 133.33- -326 -198.89 -284.8 -176 -115.56 -14.8 -26 -32.22 255.2 124 51.11 525.2 274 134.44- -324 -197.78 -281.2 -174 -114.44 -11.2 -24 -31.11 258.8 126 52.22 528.8 276 135.56- -322 -196.67 -277.6 -172 -113.33 -7.6 -22 -30.00 262.4 128 53.33 532.4 278 136.67- -320 -195.56 -274.0 -170 -112.22 -4.0 -20 -28.89 266.0 130 54.44 536.0 280 137.78

- -318 -194.44 -270.4 -168 -111.11 -0.4 -18 -27.78 269.6 132 55.56 539.6 282 138.89- -316 -193.33 -266.8 -166 -110.00 +3.2 -16 -26.67 273.2 134 56.67 543.2 284 140.00- -314 -192.22 -263.2 -164 -108.89 +6.8 -14 -25.56 276.8 136 57.78 546.8 286 141.11- -312 -191.11 -259.6 -162 -107.78 +10.4 -12 -24.44 280.4 138 58.89 550.4 288 142.22- -310 190.00 1 -256.0 -160 106.67 +14.0 -10 - 23.33 284.0 140 60.00 594.0 290 143.33

Z-260

Z

to °F From to °C to °F From to °C to °F From to °C to °F From to °C to °F From to °C

557.6 292 144.44 870.8 466 241.11 1832.0 1000 537.78 3398.0 1870 1021.1 4964.0 2740 1504.4561.2 294 145.56 874.4 468 242.22 1850.0 1010 543.33 3416.0 1880 1026.7 4982.0 2750 1510.0564.8 296 146.67 878.0 470 243.33 1868.0 1020 548.89 3434.0 1890 1032.2 5000.0 2760 1515.6568.4 298 147.78 881.6 472 244.44 1886.0 1030 554.44 3452.0 1900 1037.8 5018.0 2770 1521.1572.0 300 148.89 885.2 474 245.56 1904.0 1040 560.00 3470.0 1910 1043.3 5036.0 2780 1526.7

575.6 302 150.00 888.8 476 246.67 1922.0 1050 565.56 3488.0 1920 1048.9 5054.0 2790 1532.2 579.2 304 151.11 892.4 478 247.78 1940.0 1060 571.11 3506.0 1930 1054.4 5072.0 2800 1537.8582.8 306 152.22 896.0 480 248.89 1958.0 1070 576.67 3524.0 1940 1060.0 5090.0 2810 1543.3586.4 308 153.33 899.6 482 250.00 1976.0 1080 582.22 3542.0 1950 1065.6 5108.0 2820 1548.9590.0 310 154.44 903.2 484 251.11 1994.0 1090 587.78 3560.0 1960 1071.1 5126.0 2830 1554.4

593.6 312 155.56 906.8 486 252.22 2012.0 1100 593.33 3578.0 1970 1076.7 5144.0 2840 1560.0597.2 314 156.67 910.4 488 253.33 2030.0 1110 598.89 3596.0 1980 1082.2 5162.0 2850 1565.6600.8 316 157.78 914.0 490 254.44 2048.0 1120 604.44 3614.0 1990 1087.8 5180.0 2860 1571.1604.4 318 158.89 917.6 492 255.56 2066.0 1130 610.00 3632.0 2000 1093.3 5198.0 2870 1576.7608.0 320 160.00 921.2 494 256.67 2084.0 1140 615.56 3650.0 2010 1098.9 5216.0 2880 1582.2

611.6 322 161.11 924.8 496 257.78 2102.0 1150 621.11 3668.0 2020 1104.4 5234.0 2890 1597.8615.2 324 162.22 928.4 498 258.89 2120.0 1160 626.67 3686.0 2030 1110.0 5252.0 2900 1593.3618.8 326 163.33 932.0 500 260.00 2138.0 1170 632.22 3704.0 2040 1156.6 5270.0 2910 1598.9622.4 328 164.44 935.6 502 261.11 2156.0 1180 637.78 3722.0 2050 1121.1 5288.0 2920 1604.4626.0 330 165.56 939.2 504 262.22 2174.0 1190 643.33 3740.0 2060 1126.7 5306.0 2930 1610.0

629.6 332 166.67 942.8 506 263.33 2192.0 1200 648.89 3758.0 2070 1132.2 5324.0 2940 1615.6633.2 334 167.78 946.4 508 264.44 2210.0 1210 654.44 3776.0 2080 1137.8 5342.0 2950 1621.1636.8 336 168.89 950.0 510 265.56 2228.0 1220 660.00 3794.0 2090 1143.3 5360.0 2960 1626.7640.4 338 170.00 953.6 512 266.67 2246.0 1230 665.56 3812.0 2100 1148.9 5378.0 2970 1632.2644.0 340 171.11 957.2 514 267.78 2264.0 1240 671.11 3830.0 2110 1154.4 5396.0 2980 1637.2

647.6 342 172.22 960.8 516 268.89 2282.0 1250 676.67 3848.0 2120 1160.0 5414.0 2990 1643.3651.2 344 173.33 964.4 518 270.00 2300.0 1260 682.22 3866.0 2130 1165.6 5432.0 3000 1648.9654.8 346 174.44 968.0 520 271.11 2318.0 1270 687.78 3884.0 2140 1171.1 5450.0 3010 1654.4658.4 348 175.56 971.6 522 272.22 2336.0 1280 693.33 3902.0 2150 1176.7 5468.0 3020 1660.0662.0 350 176.67 975.2 524 273.33 2354.0 1290 698.89 3920.0 2160 1182.2 5486.0 3030 1665.6

665.6 352 177.78 978.8 526 274.44 2372.0 1300 704.44 3938.0 2170 1187.8 5504.0 3040 1671.1669.2 354 178.89 982.4 528 276.56 2390.0 1310 710.00 3956.0 2180 1193.3 5522.0 3050 1676.7672.8 356 180.00 986.0 530 276.67 2408.0 1320 715.56 3974.0 2190 1198.9 5540.0 3060 1682.2676.4 358 181.11 989.6 532 277.78 2426.0 1330 721.11 3992.0 2200 1204.4 5588.0 3070 1687.8680.0 380 182.22 993.2 534 278.89 2444.0 1340 726.67 4010.0 2210 1210.0 5576.0 3080 1693.3

683.6 362 183.33 996.8 536 280.00 2462.0 1350 732.22 4028.0 2220 1215.6 5594.0 3090 1698.9687.2 364 184.44 1000.4 538 281.11 2480.0 1360 737.78 4046.0 2230 1221.1 5612.0 3100 1704.4690.8 366 186.56 1004.0 540 282.22 2498.0 1370 743.33 4064.0 2240 1226.7 5702.0 3150 1732.2694.4 368 186.67 1007.6 542 283.33 2516.0 1380 748.89 4082.0 2250 1232.2 5792.0 3200 1760.0698.0 370 187.78 1011.2 544 284.44 2534.0 1390 754.44 4100.0 2260 1237.8 5882.0 3250 1787.8

701.6 372 188.89 1014.8 546 285.56 2552.0 1400 760.00 4118.0 2270 1243.3 5972.0 3300 1815.6705.2 374 190.00 1018.4 548 286.67 2570.0 1410 765.56 4136.0 2280 1248.9 6062.0 3350 1843.3708.8 376 191.11 1022.0 550 287.78 2588.0 1420 771.11 4154.0 2290 1254.4 6152.0 3400 1871.1712.4 378 192.22 1040.0 560 293.33 2606.0 1430 776.67 4172.0 2300 1260.0 6242.0 3450 1898.9716.0 380 193.33 1058.0 570 298.89 2624.0 1440 782.22 4190.0 2310 1265.6 6332.0 3500 1926.7

719.6 382 194.44 1076.0 580 304.44 2642.0 1450 787.78 4208.0 2320 1271.1 6422.0 3550 1954.4723.2 384 195.56 1094.0 590 310.00 2660.0 1460 793.33 4226.0 2330 1276.7 6512.0 3600 1982.2726.8 386 196.67 1112.0 600 315.56 2678.0 1470 798.89 4244.0 2340 1282.2 6602.0 3650 2010.0730.4 388 197.78 1130.0 610 321.11 2696.0 1480 804.44 4262.0 2350 1287.8 6692.0 3700 2037.8734.0 390 198.89 1148.0 620 326.67 2714.0 1490 810.00 4280.0 2360 1293.3 6782.0 3750 2065.6

737.6 392 200.00 1166.0 630 332.22 2732.0 1500 815.56 4298.0 2370 1298.9 6972.0 3800 2093.3741.2 394 201.11 1184.0 640 337.78 2750.0 1510 821.11 4316.0 2380 1304.4 6962.0 3850 2121.1744.8 396 202.22 1202.0 650 343.33 2768.0 1520 826.67 4334.0 2390 1310.0 7052.0 3900 2148.9748.4 398 203.33 1220.0 660 348.89 2786.0 1530 832.22 4352.0 2400 1315.6 7142.0 3950 2176.7752.0 400 204.44 1238.0 670 354.44 2804.0 1540 837.78 4370.0 2410 1321.1 7232.0 4000 2204.4

755.6 402 205.66 1256.0 680 360.00 2822.0 1550 843.33 4388.0 2420 1326.7 7322.0 4050 2232.2759.2 404 206.67 1274.0 690 365.56 2840.0 1560 848.89 4406.0 2430 1332.2 7412.0 4100 2260.0762.8 406 207.78 1292.0 700 371.11 2858.0 1570 854.44 4424.0 2440 1337.8 7502.0 4150 2287.8766.4 408 208.89 1310.0 710 376.67 2876.0 1580 860.00 4442.0 2450 1343.3 7592.0 4200 2315.6770.0 410 210.00 1328.0 720 382.22 2894.0 1590 865.56 4460.0 2460 1348.9 7682.0 4250 2343.3

773.6 412 211.11 1346.0 730 387.78 2912.0 1600 871.11 4478.0 2470 1354.4 7772.0 4300 2371.1777.2 414 212.22 1364.0 740 393.33 2930.0 1610 876.67 4496.0 2480 1360.0 7862.0 4350 2398.9780.8 416 213.33 1382.0 750 398.89 2948.0 1620 882.22 4514.0 2490 1365.6 7952.0 4400 2426.7784.4 418 214.44 1400.0 760 404.44 2966.0 1630 887.78 4532.0 2500 1371.1 8042.0 4450 2454.4788.0 420 215.56 1418.0 770 410.00 2984.0 1640 893.33 4550.0 2510 1376.7 8132.0 4450 2482.2

791.6 422 216.67 1436.0 780 415.56 3002.0 1650 898.89 4568.0 2520 1382.2 8222.0 4550 2510.0795.2 424 217.78 1454.0 790 421.11 3020.0 1660 904.44 4586.0 2530 1387.2 8312.0 4600 2537.8798.8 426 218.89 1472.0 800 426.67 3038.0 1670 910.00 4604.0 2540 1393.3 8402.0 4650 2565.6802.4 428 220.00 1490.0 810 432.22 3056.0 1680 915.56 4622.0 2550 1398.9 8492.0 4700 2593.3806.0 430 221.11 1508.0 820 437.78 3074.0 1690 921.11 4640.0 2560 1404.4 8582.0 4750 2621.1

809.6 432 222.22 1526.0 830 443.33 3092.0 1700 926.67 4658.0 2570 1410.0 8672.0 4800 2648.9813.2 434 223.33 1544.0 840 448.89 3110.0 1710 932.22 4676.0 2680 1415.6 8762.0 4850 2676.7816.8 436 224.44 1562.0 850 454.44 3128.0 1720 937.78 4694.0 2590 1421.1 8852.0 4900 2704.4820.4 438 225.56 1580.0 860 460.00 3146.0 1730 943.33 4712.0 2600 1426.7 8942.0 4950 2732.2824.0 440 226.67 1598.0 870 465.56 3164.0 1740 948.89 4730.0 2610 1432.2 9032.0 5000 2760.0

827.6 442 227.78 1616.0 880 471.11 3182.0 1750 954.44 4748.0 2620 1437.8 9122.0 5050 2787.8831.2 444 228.89 1634.0 890 476.67 3200.0 1760 960.00 4766.0 2630 1443.3 9212.0 5100 2815.6834.8 446 230.00 1652.0 900 482.22 3218.0 1770 965.56 4784.0 2640 1448.9 9302.0 5150 2843.3838.4 448 231.11 1670.0 910 487.78 3236.0 1780 971.11 4802.0 2650 1454.4 9392.0 5200 2871.1842.0 450 232.22 1688.0 920 493.33 3254.0 1790 976.67 4820.0 2660 1460.0 9482.0 5250 2898.9

845.6 452 233.33 1706.0 930 498.89 3272.0 1800 982.22 4838.0 2670 1465.6 9572.0 5300 2926.7849.2 454 234.44 1724.0 940 504.44 3290.0 1810 997.78 4856.0 2680 1471.1 9662.0 5350 2954.4852.2 456 235.56 1742.0 950 510.00 3308.0 1820 993.33 4974.0 2690 1467.7 9752.0 5400 2982.2856.4 458 236.67 1760.0 960 515.66 3326.0 1830 998.89 4892.0 2700 1482.2 9842.0 5450 3010.0860.0 460 237.78 1778.0 970 521.11 3344.0 1840 1004.40 4910.0 2710 1487.8 9932.0 5500 3037.8

863.6 462 238.89 1796.0 980 526.67 3362.0 1850 1010.0 4928.0 2720 1493.3 10,002.0 5550 3065.6867.2 464 240.00 1814.0 990 532.22 3380.0 1860 1015.6 4946.0 2730 1498.9 10,112.0 5600 3093.3

TOOBTAIN MULTIPLY BY

Z-261

Atmospheres In HG@32ºF 0.033421BTU Watt-hours 3.412BTU KWh 3412Centimeters Inches 2.540Cm of Hg @ 0 deg C Atmospheres 76.0Cm of Hg @ 0 deg C Grams/sq. cm 0.07356Cm of Hg @ 0 deg C Lb/sq in. 5.1715Cm of Hg @ 0 deg C Lb/sq ft 0.035913Cm/(sec)(sec) Gravity 980.665Centipoises Centistokes DensityCentistokes Centipoises 1/densityCu cm Cu ft 28,317Cu cm Cu in. 16-387Cu cm Gal (USA, liq.) 3785.43Cu cm Liters 1000.03Cu cm Quarts (USA, liq.) 946.358Cu cm/sec Cu ft/min 472.0Cu ft Cu meters 35.314Cu ft Gal (USA, liq.) 0.13368Cu ft Liters 0.03532Cu ft/min Cu meters/sec 2118.9Cu ft/min Gal (USA, liq.)/sec 8.0192Cu ft/sec Gal (USA, liq.)/min 0.0022280Cu ft/sec Liters/min 0.0005886Cu in. Cu centimeters 0.061023Cu in. Gal (USA, liq.) 231.0Cu in. Liters 61.03Cu meters Gal (USA, liq.) 0.0037854Cu meters Liters 0.001000028Cu meters/hr Gal/min 0.22712Cu meters/kg Cu ft/lb 0.062428Cu meters/min Cu ft/min 0.02832Cu meters/sec Gal/min 0.000063088Feet Meters 3.281Ft/min Cm/sec 1.9685Ft/sec Meters/sec 3.2808Ft/(sec)(sec) Gravity (sea level) 32.174Ft/(sec)(sec) Meters/(sec)(sec) 3.2808Gal (Imperial, liq.) Gal (USA, liq.) 0.83268Gal (USA, liq.) Barrels

(Petroleum, USA) 42Gal (USA, liq.) Cu ft 7.4805Gal (USA, liq.) Cu meters 264.173Gal (USA, liq.) Cu yards 202.2Gal (USA, liq.) Gal (Imperial, liq.) 1.2010Gal (USA, liq.) Liters 0.2642Gal (USA, liq.)/min Cu ft/sec 448.83Gal (USA, liq.)/min Cu meters/hr 4.4029Gal (USA, liq.)/sec Liters/min 0.0044028Grams Pounds (avoir.) 453.5924

ACF = Actual Cubic FeetA/D = Analog to DigitalATM = AtmospheresBTU = British Thermal Unitscc/min = Cubic Centimeters

per MinuteCFH = Standard Cubic Feet

per Hour (SCFH)CP = Specific HeatC.S. = Carbon SteelD = DiameterDia. = DiameterDiam . = DiameterD/A = Digital to AnalogEMI = Electromagnetic InterferenceEPR = Ethylene Propylene RubberFDA = Food and Drug

AdministrationFNPT = Female National Pipe

ThreadFPM = Feet Per MinuteFPS = Feet Per SecondF.S. = Full ScaleFT = Feetgals = Gallonsgpm = Gallons Per Minutegph = Gallons Per HourHF = Latent Heat of FusionH/L = High-LowHV = Latent Heat of VaporizationI.D. = Inside DiameterI/0 = Input/Outputk = Thermal ConductivityIbs = PoundsIbs/in 2 = Pounds Per Square Inchlpm = Liters Per MinuteL/min = Liters Per MinutemL/min = Milliliters Per MinuteMNPT = Male National Pipe Threadms = Millisecondsm/s = Meters Per SecondMSEC = MillisecondsNiCad = Nickel CadmiumNO/NC = Normally Open/

Normally ClosedNPT = National Pipe ThreadO.D. = Outside DiameterP-P = Peak to PeakPSIA = Pounds Per Square Inch

AbsolutePSID = Pounds Per Square Inch

DifferentialPSIG = Pounds Per Square Inch

GagePVC = Polyvinyl ChloridePVDF = Polyvinylidene

Fluoride (Kynaol)RF = Raised FaceRFI = Radio Frequency InterferenceRMS = Root Mean SquareSCCM = Standard Cubic

Centimeters per MinuteSCHED. NO. = Schedule NumberSCFH = Standard Cubic Feet per

HourSCFM = Standard Cubic Feet per

MinuteSLM = Standard Liters per MinuteSLPM = Standard Liters per Minutesq.ft. = Square FeetSSU = Saybolt Seconds Universal∆T = Temperature RiseTTL = Transistor-Transistor LogicW = WattsW-hr = Watt-HoursW/in2 2 Watt DensityW T = Weight of Material

TECHNICAL DATA SECTIONReference Section

Conversion FactorsTERMINOLOGY

Z-262

Z

METRIC PREFIXES

MEGA = 1,000,000KILO = 1,000HECTO = 100DECA= 10DECI= .1CENTI = .01MILLI= .001MICRO = .000,001

TEMPERATURE CONVERSION FORMULAS:

˚F = (9/5 ˚C) + 32˚C = (˚F - 32) x 5/9

TOOBTAIN MULTIPLY BY

Conversion Factors

Grams/(cm)(sec) Centipoises 0.01Grams/cu cm Lb/cu ft 0.016018Grams/cu cm Lb/cu in. 27.680Grams/cu cm Lb/gal 0.119826Inches Centimeters 0.3937Inches of Hg @ 32˚ F Atmospheres 29.921Inches of Hg @ 32˚ F Lb/sq in. 2.0360Inches of Hg @ 32˚ F In. of H2O @ 4°C 0.07355Inches/deg F Cm/deg C 0.21872Kg Pounds (avoir.) 0.45359Kg-cal/sq meter BTU/sq ft 2.712Kg/cu meter Lb/cu ft 16.018Kg/(hr)(meter) Centipoises 3.60Kg/liter Lb/gal (USA, liq.) 0.11983Kg/meter Lb/ft 1.488Kg/sq cm Lb/sq in. 0.0703Kg/sq meter Lb/sq ft 4.8824KWh BTU .0002930KWh watt-hours .001Liters Cu ft 28.316Liters Cu in. 0.01639Liters Cu meters 999.973Liters Gal (Imperial, liq.) 4.546Liters Gal (USA, liq.) 3.785306Liters/kg Cu ft/lb 62.42621Liters/min Cu ft/sec 1698.963Liters/min Gal (USA, liq.)/min 3.785Liters/sec Cu ft/min 0.47193Liters/sec Gal/min 0.063088Meters Feet 0.3048Meters/sec Ft/sec 0.3048Mete rs/sec)(sec) Ft/(sec)(sec) 0.3048Ounces Grams 0.035274Pounds (avoir.) Kg 2.2046Pounds/cu ft Grams/cu cm 62.428Pounds/cu ft Pounds/gal 7.48Pounds/cu in. Grams/cu cm 0.036127Pounds/(hr)(ft) Centipoises 2.42Pounds/inch Grams/cm 0.0056Pounds/(sec)(ft) Centipoises 0.000672Pounds/gal. (USA, liq.) Kg/liter 8.3452Pounds/gal. (USA, liq.) Pounds/cu ft 0.1337Pounds/gal. (USA, liq.) Pounds/cu in. 231Sq centimeters Sq ft 929.0Sq centimeters Sq in. 6.4516Sq ft Sq meters 10.764Sq in. Sq centimeters 0.155Sq meters Sq ft 0.0929W-hr BTU .2390W-hr KWh 1000

®

National Pipe TaperThread DimensionsNPT SIZE THREADS DIM “A” DIM “B”

PER INCH (IN) (IN)1⁄16 27 .312 .2611⁄8 27 .405 .2641⁄4 18 .540 .4023⁄8 18 .675 .4081⁄2 14 .840 .5343⁄4 14 1.050 .5461 111⁄2 1.315 .683

11⁄4 111⁄2 1.660 .707

EFECTIVE THREAD

B

A1°47'

Z-263

Percent of rated wattage for various applied voltagesApplied Rated VoltageVoltage 110 115 120 208 220 230 240 277 380 415 440 460 480 550

VARIATIONS OF OHM’S LAW

VOLTSœ ßßßßßßßßVOLTS = WATTS x OHMS

VOLTS = WATTSAMPERES

VOLTS = AMPERES x OHMS

OHMS

OHMS = VOLTSAMPERES

OHMS = VOLTS2

WATTS

OHMS = WATTS2

AMPERES2

AMPERES

AMPERES = VOLTSOHMS

AMPERES = WATTSVOLTS

AMPERES = WATTSOHMS

WATTS

WATTS = VOLTS2

OHMS

WATTS = AMPERES 2 x OHMS

WATTS = VOLTS x AMPERES

Currents for resistance heating loadsHeating elements are frequently used atvoltages other than those shown in ourcatalog. The percentages shown beloware used to determine the resultingwattage. Should you wish to use aheater on a voltage not shown above,you may calculate the resultant wattagewith this formula:

Actual Wattage = Rated Wattage x Applied Voltage2

Rated Voltage2

Table 11 Currents for resistance heating loads

1 8.4 4.8 4.2 2.3 2.1 2.8 2.5 1.4 1.32 16.7 9.7 8.4 4.6 4.2 5.6 4.9 2.7 2.53 25 14.5 12.5 6.9 6.3 8.4 7.3 4 3.74 33.4 19.3 16.7 9.1 8.4 11.2 9.7 5.3 4.9

5 41.7 24.1 20.9 11.4 10.5 13.9 12.1 6.6 6.16 50 28.9 25 13.7 12.5 16.7 14.5 7.9 7.37.5 62.5 36.1 31.3 17.1 15.7 20.9 18.1 9.9 9.110 83.4 48.1 41.7 22.8 20.9 27.8 24.1 13.2 12.1

12 100 57.7 50 27.3 25 33.4 29 15.8 14.515 125 72.2 62.5 34.1 31.2 41.7 36.2 19.7 18.120 167 96.2 83.4 45.5 41.7 55.6 48.2 26.3 24.125 209 121 105 56.9 52.1 69.5 60.3 32.9 30.1

30 250 145 125 68.2 62.5 83.4 72.3 39.4 36.250 417 241 209 114 105 139 121 65.7 60.375 625 361 313 171 157 209 181 98.6 90.4100 834 481 417 228 209 278 241 132 121

110 100% 91% 84% 28% 25% 23% 21% 16% 8.4% 7% 6.2% 5.7% 5.2% 4%115 109% 100% 92% 31% 27% 25% 23% 17% 9.0% 7.6% 6.7% 6.2% 5.7% 4.3%120 119% 109% 100% 33% 30% 27% 25% 19% 10% 8.4% 7.4% 6.8% 6.3% 4.8%208 300% 100% 89% 82% 75% 56% 30% 25% 22% 20% 19% 14%220 112% 100% 91% 84% 63% 34% 28% 25% 23% 21% 16%230 122% 109% 100% 92% 69% 37% 31% 27% 25% 23% 17%240 133% 119% 109% 100% 75% 40% 33% 30% 27% 25% 19%277 133% 100% 53% 45% 40% 36% 33% 25%380 188% 100% 84% 74% 68% 63% 47%415 119% 100% 89% 81% 75% 57%440 112% 100% 91% 84% 64%460 123% 109% 100% 92% 70%480 119% 109% 100% 76%550 156% 143% 131% 100%

VOLTS OHM

S

WAT

TSAMPERES

W IRE

EI

IR

W/R

E2

RI2R

E2

W

E I

ER

W I2

WI

WE

WR

kW 120V 208V 240V 440V 480V 208V 240V 440V 480VThree phase balanced loadSingle phase

OHM’S LAW

Z-264

Z

Ratio ofSI unit Magnitude of

Quantity Symbol Equation SI unit symbol CGS unit SI to cgs unitCurrent I, i I=E/R; I = E/Z; I = Q/t Ampere A Abampere 10-1

Quantity Q, q Q = it; Q = CE Coulomb C Abcoulomb 10-1

Electromotive force E, e E = IR; E = W/Q Volt V Abvolt 108

Resistance R, r R=E/I; R = rl /A Ohm Ω Abohm 109

Resistivity r r = RA / I Ohm-metre Ω•m Abohm-cm 1011

Conductance G, g G =g A / l G = A/rl Siemens S Abmho 10-9

Conductivity g g = 1/r; g = I/ RA Siemens/meter S/m Abmho/cm 10-11

Capacitance C C = Q/E Farad F Abfarad* 10-9

Permittivity e Farads/meter F/m Stat farad*/cm 8.85 X 10-12

Relative permittivity er er = e/eo Numerical Numerical ISelf-inductance L L = - N(df/dt) Henry H Abhenry 109

Mutual inductance M M = K(L1L2) 1/2 Henry H Abhenry 109

Energy J J = eit Joule J Erg 107

kwh kwh = kw/3600; 3.6 MJ Kilowatthour kWh 36 X 1012

Active power W W = J/t; W = EI cos U Watt W Abwatt 107

Reactive power jQ Q = El sin U Var var Abvar 107

Apparent power VA VA = El Volt-ampere VAPower factor pf pf = W/VA; pf = W/(W + jQ) 1Reactance, inductive XL XL = 2pfL Ohm Ω Abohm 109

Reactance, capacitive XC XC = 1/(2pfC) Ohm Ω Abohm 109

Impedance Z Z = E/I Z = R + j(XL - XC) Ohm Ω Abohm 109

Conductance G G = R/Z2 Siemens S Abmho 10-9

Susceptance B B = X/Z2 Siemens S Abmho 10-9

Admittance Y Y =I/E; Y = G + jB Siemens S Abmho 10-9

Frequency f f = 1/T Hertz Hz Cps Hz 1Period T T = 1/f Second s Second 1Time constant T L/R; RC Second s Second 1Angular velocity ω ω= 2πf Radians/second rad/s Radians/second 1

*1 Abfarad (EMU Units) = 9 X 10-20 stat farads (ESU units).

Electrical Units

Reproduced with Permission from McGraw-Hill, Marks’ Standard Handbook forMechanical Engineers, 8th ed. Authors: Baumeister, et al. Copyright 1987

Omega Temp

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