Industrial temperature measurement Basics and practice

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© 2008 ABB Automation Products GmbH

Practices for IndustrialTemperature Measurements

Author Team:

Karl Ehinger, Dieter Flach, Lothar GellrichEberhard Horlebein, Dr. Ralf HuckHenning Ilgner, Thomas KayserHarald Müller, Helga SchädlichAndreas Schüssler, Ulrich Staab

ABB Automation Products GmbH

Introduction

Automation is a growing, worldwide fundamental technology. The driving force for itsgrowth are the variety of distinct economical and environmental requirements of the ba-sic food and energy supply for an efficient, low emission utilization of natural resourcesand energy and the increased productivity in all manufacturing and distribution pro-cesses.

As a result of the enormous growth of the markets in certain regions of the world andthe increasing integration between them, new requirements and unexpected opportu-nities have arisen.

The interaction between the actual measurement technology and the processes iscontinually becoming tighter. The transfer of information and quality evaluations havetraditionally been a key requirement and a fundamental strength of the ABB-Engineersfor worldwide optimization through automation.

Temperature, for many processes in the most varied applications, is the primarymeasurement value. The wide spectrum of applications in which the measurementlocations are usually directly in the fluid medium, often pose difficult requirements onthe process technician.

With this Handbook for industrial temperature measurements we are attempting to pro-vide the technician with solutions to his wide variety of responsibilities. At the sametime, it provides for those new to the field, insight into the basics of the most importantmeasurement principles and their application limits in a clear and descriptive manner.

The basic themes include material science and measurement technology, applications,signal processing and fieldbus communication. A practice oriented selection of appro-priate temperature sensor designs for the process field is presented as well as therequired communication capability of the meter locations.

The factory at Alzenau, Germany, a part of ABB, is the Global Center of Competencefor Temperature, with numerous local experts on hand in the most important industrialsectors, is responsible for activities worldwide in this sector.

125 years of temperature measurement technology equates to experience and compe-tence. At the same time, it forms an important basis for continued innovation. In closecooperation with our customers and users, our application engineers create conceptsto meet the measurement requirements. Our Sector-Teams support the customer,planner and user in the preparation of professional solutions.

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The most modern developments, supported by a network of globally organized ABB-Research Centers, assure innovative products and solutions. Efficient factories andcommitted employees manufacture the products using the latest methods and produc-tion techniques. Competent and friendly technical advice from Sales and Service roundout the ABB offering.

We wish you much pleasure when reading this Handbook and that you may findsuccess when applying the principles to practical applications. Thanks also the all theauthors who have contributed to the creation of this book. We also look forward to yoursuggestions and comments, which are appreciated and can be incorporated in newtechnological solutions.

“Power and Productivity for a better world“

Eberhard Horlebein

PRU TemperatureDirector Product Management

www.abb.com/instrumentation

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Formula Symbols

p Pressure (Pa, bar)

V Volume (l, m3)

n Material quantity (mol)

R Gas Constant

t Temperature (°C, °F, K, °N, °R)

t90 Temperature per ITS-90 in °C (°F)

T90 Temperature per ITS-90 in K

Q Heat energy (J, Nm, Ws)

Ll Spectral radiation density (W m-2 l-1)

en Elementary thermal voltage (mV)

Rt Resistance at the temperature t (Ω)

R0 Resistance at the temperature 0 °C (°F) (Ω)

α Slope coefficient of a Pt100 between 0 °C (32 °F) and 100 °C (212 °F) (K-1 or °F-1)

δ Coefficient from the Callendar equation (K-2)

β Coefficient per van Dusen for t < 0 °C (32 °F) (K-4)

Abbreviations

AISI American Iron and Steel Institute

ANSI American National Standards Institute

DKD Deutscher Kalibrier Dienst (German Calibration Service)

JIS Japanese Industrial Standards

NF Normalisation Francaise (French Standards)

NAMUR Normungs-Ausschuss the Mess- and Regelungstechnik(Standards Commission for Measurement and Control Technology)

NACE National Association of Corrosion Engineers

ASME American Society of Mechanical Engineers

MIL Military Standard

Page

1 125 Years of Competency in TemperatureMeasurement Technology at ABB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2 Introduction to Temperature Measurement Technology . . . . . . . . . . . . . 172.1 Historic Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172.1.1 Heat and Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172.1.2 The Historic Development of the Thermometers . . . . . . . . . . . . . . . . . . . . . . 182.1.3 The Thermodynamic Temperature Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . 222.1.4 The International Temperature Scale of 1990 (ITS 90) . . . . . . . . . . . . . . . . . 232.2 Basics of Temperature Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252.2.1 The Physical Concept of Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252.2.2 The Technical Significance of Temperature . . . . . . . . . . . . . . . . . . . . . . . . . 252.2.3 The Thermoelectric Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262.2.4 The Temperature Dependent Ohmic Resistance . . . . . . . . . . . . . . . . . . . . . 292.3 The Principles of Temperature Measurement . . . . . . . . . . . . . . . . . . . . . . . . 332.3.1 Mechanical Contacting Thermometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352.3.2 Electric Contacting Thermometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362.3.3 Additional Contacting Measurement Principles . . . . . . . . . . . . . . . . . . . . . . . 372.3.4 Non-contacting Temperature Measurement . . . . . . . . . . . . . . . . . . . . . . . . . 38

3 Industrial Temperature Measurement UsingElectrical Contacting Thermometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.1 Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403.1.1 Thermocouples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403.1.2 Mineral Insulated Thermocouple Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513.1.3 Thermocouple Wires and Compensating Cables . . . . . . . . . . . . . . . . . . . . . 553.1.4 Older National Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583.1.5 Measurement Resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623.2 Industrial Temperature Sensor Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 763.2.1 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 763.2.2 Installation Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 813.2.3 Process Connections Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 853.2.4 Process Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 873.2.5 Thermowell Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893.2.6 Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 963.2.7 Material Selections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1063.2.8 Ceramic Thermowells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1083.3 Application Specific Temperature Sensor Designs . . . . . . . . . . . . . . . . . . . 1113.4 Dynamic Response of Temperature Sensors . . . . . . . . . . . . . . . . . . . . . . . 1273.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1273.4.2 Step Response and Transfer Functions, Response Time and

and Time Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1283.4.3 Establishing the Dynamic Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1293.4.4 Influencing Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

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3.5 Aging Mechanisms in Temperature Sensors . . . . . . . . . . . . . . . . . . . . . . . 1313.5.1 Drift Mechanisms for Thermocouples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1313.5.2 Drift Mechanisms for Resistance Thermometers . . . . . . . . . . . . . . . . . . . . 1433.6 Possible Errors and Corrective Measures . . . . . . . . . . . . . . . . . . . . . . . . . . 148

4 Non-Contacting Temperature Measurements in Field Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

4.1 Advantages and Uses for Applying Infrared Measuring Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

4.2 Fundamentals and Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1554.2.1 Determining the Emissivity Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1594.2.2 Measuring Temperatures of Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1604.2.3 Measuring Temperatures of Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1614.2.4 Measuring Temperatures of Glass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1624.2.5 The Measuring Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1634.2.6 Stray Radiation and High Ambient Temperatures . . . . . . . . . . . . . . . . . . . . 1654.2.7 Optic Radiation Input, Protection Glass and Window Materials . . . . . . . . . 1664.3 Indication and Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1694.4 Application Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

5 Measurement Signal Processing and Evaluation . . . . . . . . . . . . . . . . . 1715.1 Application of Transmitters in Temperature Measurements . . . . . . . . . . . . 1715.2 Measurements of Thermal Voltages and Resistances . . . . . . . . . . . . . . . . 1745.3 Power Supply of Temperature Transmitters . . . . . . . . . . . . . . . . . . . . . . . . 1775.4 Design Principles for a Temperature Transmitter . . . . . . . . . . . . . . . . . . . . 1785.5 Programmable Temperature Transmitters . . . . . . . . . . . . . . . . . . . . . . . . . 1845.6 Communication Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1885.7 Temperature Transmitters in Explosion Hazardous Areas . . . . . . . . . . . . . 1945.8 Electromagnetic Compatibility (EMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2015.9 Temperature Transmitters using Interface Technology . . . . . . . . . . . . . . . . 2035.10 High Accuracy Temperature Measurements with Programmable

Transmitters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

6 Accuracy, Calibration, Verification, Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

6.1 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2096.1.1 Basic Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2096.1.2 Determining (Estimating) the Measurement Uncertainties . . . . . . . . . . . . . 2106.1.3 Measurement Uncertainty Estimations using a Practical Example . . . . . . . 2136.1.4 Error Effects for Temperature Measurements . . . . . . . . . . . . . . . . . . . . . . . 2156.2 Calibration and Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2246.2.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2246.2.2 Calibration Methods for Temperature Sensors . . . . . . . . . . . . . . . . . . . . . . 2256.2.3 The Traceability of the Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2266.2.4 Suitable Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2276.2.5 The Water Triple Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228

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6.2.6 Documenting the Calibration Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2296.2.7 The German Calibration Service (DKD) . . . . . . . . . . . . . . . . . . . . . . . . . . . 2316.2.8 DKD-Laboratories at ABB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2326.2.9 Conducting a Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2346.2.10 User Advantages offered by the DKD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2356.3 Quality Assurance Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

7 Explosion Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2447.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2447.2 Terms and Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2457.3 Types of Protection in Europe and in North America . . . . . . . . . . . . . . . . . 2527.4 Marking of the Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2567.5 Evidence of the Intrinsic Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

8 SIL - Functional Safety in Process Automation . . . . . . . . . . . . . . . . . . . 261

9 Standards and Regulations for Temperature Measurements . . . . . . . . 263

10 Appendix 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

11 Appendix 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

12 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276

13 Basic Values for Thermocouples and Resistance Thermometers . . . . 280

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1 125 Years of Competency in TemperatureMeasurement Technology at ABB

Significant activities at ABB in industrial temperature measurements date back to 1881.

Fig. 1-1: G. Siebert factory

Wilhelm Siebert started in his family’s cigar rolling factory G. Siebert in Hanau, Ger-many, by melting platinum and mechanically working the material into wires. Helearned the art of “Assaying“ at the plant of Dr. Richter & Co. in Pforzheim, Germany.In 1905 Degussa became a participant in the G. Siebert company. Later on the treat-ment of Platinum and Platinum/Rhodium wires for thermocouples was further devel-oped here.

Between 1860 and 1900 the development of electrical temperature measurements be-gan. This laid the cornerstone for present day process automation and far distancetransfer of measurement signals. During 1883...1891 another branch of the long exist-ing temperature measurement technology resulted from the invention by Prof. Ferdi-nand Braun (1850...1918/Nobel Prize in Physics 1909) of the Braun Pyrometer.

Fig. 1-2: Electrical precision-pyrometer according to Braun

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A protected Platinum wire was used as sensor which was connected across a Wheat-stone Bridge to galvanometer. The measurement value could be read directly from acalibrated scale in °C, without calculations, due to the changing resistance of thebridge. This instrument was used to measure temperatures to 1500 °C (2732 °F) inovens and boilers.

In 1893 the Telethermometer was invented, e.g. “to remote control the heater from anoffice”. It was used to measure the temperature in rooms, greenhouses, oasts, dryingchambers or ovens in the Ceramic industry.

Fig. 1-3: Telethermometer

Further developments in temperature sensors during the time span 1894…1974:

Fig. 1-4: Temperature sensor history up to 1974

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Over a span of approximately 50 years, beginning in 1939, transmitters were devel-oped to improve the transmission of the measured temperatures.

Development steps for temperature transmitters during the time span 1939…1985:

Fig. 1-5: Temperature transmitter history up to 1985

From 1950...1954 the Degussa company developed a high temperature capable ther-mocouple “PtRh18“ with long term stability, which later, in 1967...1974, was certified bythe American Standards Association Committee C96 (ISA) as “PtRh18“ ThermocoupleType B.

About 1960 the Degussa company in Hanau, Germany, began series manufacturing ofnew temperature measurement wire resistors.

1962 Obrowski and Prinz from Degussa defined the reference function and basic valuetables for the “PtRh18“ thermocouples.

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In 1960 Degussa began manufacturing thermocouple wires and mineral insulatedcables. By 1970, Degussa had technically improved this process which led to a volumeincrease.

Fig. 1-6: Cross section of a mineral insulated cable

1977 Degussa further expanded their temperature measurement technology activitiesby acquiring Bush Beach Engineering Ltd. in England, who brought with them vastapplication experience in the oil and gas industry sector.

1978 one of the first worldwide electronic transmitters for mounting directly in the tem-perature sensor head was developed. It can be installed in explosion hazardous areas.After intensive tests in the Degussa factory, the transmitter was introduced into themarket at leading customers in the process industries. After some initial concerns, theproduct received enormous acceptance. The new transmitter began replacing existingtechnologies.

Fig. 1-7: First transmitter for mounting in the sensor head (TR01)

1988 saw the introduction of an industrialized version of fiber optic temperature mea-surement instruments, which, e.g., can make temperature measurements in micro-wave systems.

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1989 Degussa founded a new subsidiary and brand, SENSYCON in Hanau, Germany.

1991 Hartmann & Braun acquired SENSYCON.

1994 SENSYCON temperature measurement technology manufacturing was movedfrom Hanau to Alzenau, Germany, about 15 km (10 mi) away.

1995 the first HART-sensor head transmitter was developed.

1996 Elsag Bailey acquired Hartmann & Braun including the temperature measure-ment systems from SENSYCON.

1998 the first fieldbus capable temperature transmitter was developed.

1999 ABB acquired Elsag Bailey, whereby SENSYCON temperature measurementtechnology achieved a worldwide leading role in the instrumentation sector.

2006 new powerful and state of the art temperature transmitters designated TTH300for sensor head mounting and TTF300 for field mounting were introduced to themarket.

Fig. 1-8: Transmitters TTH300 and TTF300

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The temperature sensor series – SensyTemp TSP100 and SensyTemp TSP300 for theprocess industries represent the present state of the technology.

Fig. 1-9: Temperature sensor series SensyTemp TSP

“With a Tradition for Innovation“ ABB in the last 125 years has actively lead the way intemperature measurement technology. The goal is to challenge the measurementtechnology and improving the efficiency to satisfy the global requirements of thecustomers.

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2 Introduction to Temperature Measurement Technology

2.1 Historic Development

2.1.1 Heat and Temperature

Only in recent times has the heat phenomenon been studied systematically. Previous-ly, man was satisfied with a few qualitative, practice oriented experiences relative toheat. With the invention of the steam engine, the interest of the scientists in the heatphenomenon increased. Joseph Black was the first to realize the difference betweenheat and temperature. In 1760 he declared that applying the same heat to different ma-terials results in different temperatures.

Initially heat was considered to be a material substance, which could be added orremoved from a material or, could be transferred from one material to another. Thissubstance was named Caloric. When wood is burned, according to this theory, theCaloric content in the wood is transferred to the flame, from there further on to the boilerset over the flame and then to its contents. When the water in the boiler becomes sat-urated with caloric, it is converted to steam.

Only toward the end of the 18th century did observations lead Benjamin Thompson(Count Rumford) and Humphry Davy to an alternate theory, which described heat as acyclic phenomenon.

The theory that heat is a form of energy is attributed, among others, to the work of thephysicist Sadi Carnot, who is considered the father of scientific thermodynamics. Heinvestigated early in the 19th century, the motion of heat from the viewpoint of how theenergy stored in the steam is converted to mechanical work. The investigation of thereverse process, namely, how work is converted to heat, led to the basic thought thatenergy is conserved, i.e., it can neither be created nor destroyed. This approach led tothe law of conservation of energy (First Law of Thermodynamics).

The prerequisite for a clear understanding of heat requires an exploration of the atomicstructure of materials. In the middle of the 18th century, Maxwell and Bolzmann devel-oped the mathematical basics and formulated the kinetic gas theory. In this theory, heatis equated to molecular movement. The thermal motions of a molecule are totally ran-dom and independent of each other. Their velocity distribution however can be definedby strict mathematical laws.

The question regarding the concept of temperature, however, was still not conclusivelyanswered.

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Maxwell defined the temperature of a body as a thermal property, which makes it pos-sible to transfer heat (energy) to or from another body. From a measurement viewpoint,temperature is then the physical property which provides information about the energycontent of a system and thereby describes the heat energy content (degree of heat,heat status). For Maxwell temperature was the measure of the average kinetic energyof the molecules which constitute the substance, and the measurement of the temper-ature provides a mean to determine the energy (heat) content of the substance.

The term temperature supposedly originated from the Latin word “tempera“, whichmeans "moderate or soften".

If one wants to determine the temperature of a system, it follows that the velocity of themolecules should be selected as the value to be measured. Based on this approach, asystem will have no heat content when the molecules have lost all their kinetic energy,i.e., are at rest. This condition could be defined as “absolute heatlessness“. Since theobservation and measurement of the motion of the molecules is impractical and unre-alistic, it is unusable in practice. Therefore to make practical temperature measure-ments, other methods must be employed. Utilized are the effects that the heat (energy)has on other properties of the system, e.g. geometric expansion when heat is applied.

Human senses evaluate the temperature of a body only subjectively. Even so, theterms “hot“, “warm“, “cold“ or “ice cold“ mean something to everyone based on theirown experience and are relatively useful for comparison purposes. This also applies tovisual terms such as “red hot“ or “white hot“. The exact assignment of a temperaturevalue (quantification) however eludes the subjective possibilities of man.

For an objective and reproducible measurement of the temperature of a body, asuitable measurement instrument is required.

2.1.2 The Historic Development of the Thermometers

Instruments to measure the temperature generally are called thermometers. What therelationship to temperature was that the old Egyptians had, has not been handed down.No instrument was ever discovered in any of the Egyptian drawings from which one caninfer that it was utilized for temperature measurement. But it is quite clear that the oldEgyptians understood how to make ice (evaporative cooling).

The oldest known instrument for “measuring“ temperature was based on the expansionof air and is attributed to the Greek Heron of Alexandria (about 120 BC). It was not aThermo “Meter“ in the true sense since it did not have a scale. Thermometers basedon the same principle (the so called Thermoscopes) appeared again at the beginningof the 17th century in Europe.

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Individuals who have been identified as being associated with the continued systematicdevelopment of thermometers, are Satorio Santorre, Giovanfrancesco Sagredo, Gali-leo Galilei, Benedetto Castelli and Vicencio Viviani. That all these names have an Ital-ian heritage can be traced to the fact that the glass blowing art was most developed inItaly at that time.

Fig. 2-1: a) Early air thermometer (thermoscope) with compass to measure the changes;b) Early florentine thermometer; c) Typical thermometer around 1750

The step from Thermoscope to liquid filled thermometer is attributed to Grand DukeFerdinand II of Toscany, a student of Galilei. In 1654 he manufactured liquid alcoholfilled thermometers (so called Florentine Thermometer) made with a bulb and capillary(including a scale with 50 units). The scales were aligned by comparing the instrumentsamong each other.

Antonio Alemanni around 1660 built a thermometer with a length of 108 cm (42.5“)which was divided into 520 units. The capillary for this thermometer was like a coil. Thisinstrument is still available today.

In 1701 Sir Isaac Newton described a liquid oil filled thermometer and a calibrationmethod at the temperature of freezing water, (0 °N), and the temperature of blood(12 °N).

At the beginning of the 18th century, the Dutchman Musschenbroek was apparently thefirst to conceive the thought of using the expansion of metals for measuring tempera-tures.

a) b) c)

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Around 1703 the Frenchman Amontons designed a gas thermometer with a constantvolume and postulated, that heat was a type of movement. He was the first to mentionthe concept of a zero temperature point in nature, which would be reached if all move-ment was completely at rest.

In 1714 Fahrenheit, a glass blower from Danzig in Poland, appreciably improved theexisting liquid filled thermometers and implemented the initial step to a measurementinstrument. He initially filled the thermometer with alcohol and later with Mercury, whichhad the advantage of not wetting the glass capillary and which also could be used upto the boiling point of water. These “Fahrenheit Thermometers“ had a scale which wasreproducible because Fahrenheit introduced three fixed values:

• 0 for the temperature of an ammonium chloride mixture,• 4 for the temperature of melting ice and • 12 for the temperature of the human body.

It was desirable at that time to define the spacing between the fixed values as 12 inaccordance with the duodecimal numbering system. Since the individual values wereunsuitably large, they were halved a number of times until each of the original degreescorresponded to 8 degrees. The result was that the freezing point of water nowoccurred at a value of 32 and body temperature at a value of 96. Later Fahrenheit usedthe boiling point of water as the upper fixed value and established its value as 212 °Fby extrapolating the scale from 0 °F to 32 °F. He maintained these values, whose dif-ference is 180 °F, for all later measurements. Closer observation resulted in a bodytemperature of 98 °F in a healthy individual. This scale can still be found in a numberof countries today.

Around 1715 the Frenchman Réaumur defined a temperature scale which bears hisname. In this scale the ice point is 0 °R and the temperature increase which an alcohol-water mixture (20 % water) experiences as its volume increases by 0.1 % is defined as1 °R. Transferring this scale to a Mercury thermometer resulted in a value of 80 °R forthe boiling point of water.

In 1740 the Swede A. Celsius defined a scale with 100 graduations in which the freez-ing point of water is 0 and its boiling point is 100. Three years later the Celsius scalewas established by his student Carl von Linné, which exists to the present day, with theconditions 0 °C for the freezing point and 100 °C for the boiling point.

In the middle of the 18th century, the temperature measurement (Thermometry) wascommonly introduced to the science as measurement technology. The maximum mea-surable temperatures at that time were about 300 °C (572 °F). The desire to measuretemperatures of molten metals (metallurgy) led to the development of additional mea-surement methods.

20

The important milestones of the later developments:

1800 Construction of a simple bimetal thermometer by A. L. Brèguet.

1818 Discovery of the relationship between the electrical resistance of an ohmic conductor and temperature by H. Cr. Oersted.

1820 Description of the effect of thermoelectricity by Seebeck.

1821 Construction of the first thermocoupleby H. Davy.

1840 Development of a thermocouple made of Nickel-Silver and iron for measuring body temperature by Chr. Poggendorf.

1852 Establishment of a thermodynamic temperature scale, which is independent of all material properties and is basedon the 2nd Law of Thermodynamics by William Thompson (later Lord Kelvin).

1871 Construction of a Platinum resistance thermometer by Werner von Siemens

1885 Further development of the Platinum resistance thermometer intoa precision thermometer, including higher temperature use by H.L. Callendar

1887-1889 Construction of thermocouples for technical temperature measurements by H. le Chatelier and C. Barus

1892 Development of the first usable spectral pyrometer by H. le Chatelier.

The problems which scientists in the 18th century had in using their instruments and thetransfer of their measurement results were clarified by statements made by René-An-toine Ferchault de Réaumur in the year 1730:

“The thermometers are without a doubt one of the nicest inventions of modern physics,and they have also contributed most to its progress. One likes very much to observethermometers in order to determine the temperature of the air; namely, one uses theinstrument when it is too hot or too cold for comfort.

If on the one hand one realizes how amusing and useful this instrument is, one knowson the other hand its imperfections. The action of all thermometers is different. Finally,one understands only the thermometer which one has observed for many years. Allothers remain incomprehensible.“

21

2.1.3 The Thermodynamic Temperature Scale

The decisive starting point for a general temperature scale is the indispensable require-ment for a reproducible scale, independent of the special characteristics of the materi-als used. In addition, the entire temperature range must be applicable without restric-tions, actually, from the lowest to the highest temperatures. This is the only way toensure the transferability of measurement results.

The path to this goal is provided by the basics of thermodynamics and was first followedby Lord Kelvin in the year 1852. Thermodynamics describes the relationship betweencondition changes of materials and temperature, allowing the temperature to be deter-mined when any of these condition changes can be measured.

The definition of the thermodynamic temperature scale is derived from the 2nd Law ofThermodynamics using the Carnot Cycle. The starting point is the fact that the temper-ature change in a perfect gas under constant volume and pressure conditions is a func-tion only of the heat quantity Q added or removed and is proportional to it.

A gas volume which has no heat energy content has reached its lowest thermodynamicenergy level. From this viewpoint Kelvin postulated the existence of a lowest possibletemperature, the absolute zero, and assigned the value 0 to that condition. By definingthe scale in this manner, negative temperatures cannot exist, and therefore, the tem-perature scale proposed by Kelvin has an absolute character, an absolute tempera-ture scale. Thermodynamic temperature conditions are defined by the absolute tem-perature value with units of "Kelvin" (K). The Kelvin units are one of the primary unitswhich exist today in the International System of Units (SI).

For the practical determination of the temperature, the quantities of heat added orremoved during the process cycle must be determined experimentally. The requiredprocedure is technically very difficult to solve.

Using the equation of state for a perfect gas as a basis

p · V = n · R · T

which defines the relationship between the thermodynamic values pressure (p), vol-ume (V), temperature (T) of a quantity (n) of a gas and the ideal gas constant (R), it caneasily be shown that the thermodynamic temperature (T) can be calculated from themeasurement of one of the other variables (pressure or volume), provided that the oth-er values remain constant. The scientific significance of the thermodynamic tempera-ture scale achieved even greater importance, when L. Bolzmann and M. Planck founda method to include light-radiation of very highly heated substances in the basic equa-tions of thermodynamics.

22

2.1.4 The International Temperature Scale of 1990 (ITS 90)

In metrological practice, thermodynamic temperatures are measured with a gas ther-mometer, or at higher temperatures, using radiation pyrometers.

The first valid, generalized definition for a temperature scale, was for normal Hydrogenin the year 1889. It was based on using a gas thermometer as the measuring instru-ment.

The effort for this measurement method can hardly be justified for practical measure-ments. Therefore at the beginning of the last century the first experiments were con-ducted to define an easily representable, and thereby practical temperature scale,which would be in essential agreement with the thermodynamic temperature scale.

The first version of this scale was the “International Temperature Scale of 1927“(ITS-27). Based on the scales ITS 48 and IPTS-68, the EPT-76 was published in 1975.

Further basic theoretical and experimental investigations of a thermodynamic temper-ature scale in the subsequent years led to a new and improved formulation which hasbeen valid since 1990, the “International Temperature Scale of 1990“ (ITS-90).

Temperatures measured per ITS-90 are designated T90 for temperature values in Kand t90 for temperature values in °C.

ITS-90 defines a temperature scale in the range from 0.65 K to far above 3000 K. It isdivided into ranges, some of which overlap, for which defined temperature points the“Normal Instruments“ (to picture the ranges between the fixed points), and equationsare prescribed for extrapolation.

In the temperature range to 1357 K (1084 °C/1983 °F), for thermometric measure-ments 16 fixed points are used for the defining and mathematical relationships aregiven with which temperature values between two of these fixed points can bedetermined. The fixed points are the phase equilibrium values for extremely pure sub-stances, at which the phase change (liquid to gas or liquid to solid) occurs at constanttemperature values. Numerical values are assigned to these temperatures that bestagree with the thermodynamic measurements. The most important fixed point in ITS-90 is the triple point of water, at which solid, liquid, and gaseous water coexist in equi-librium and which occurs at T90 = 273.16 K or t90 = +0.01 °C.

23

Tbl. 2-1: Defined fixed points for ITS-90

In the temperature range above 1357 K, ITS-90 is defined using the Planck RadiationFormula (black body radiation).

Dependent on the type of normal instrument (interpolation instrument), ITS-90 is divid-ed into three temperature ranges:

In the range from 0.65 K to 24.55 K the steam and gas pressure thermometers of var-ious designs are used as the normal instruments.

In the range from 13.8 K to 1234.93 K the Platinum resistance thermometer is used asthe normal instrument. Platinum normal resistance thermometers (so called ITS-90-Thermometers) must satisfy very high technical requirements and are exceptional pre-cise instruments. For practical applications in calibration laboratories there also existso called secondary thermometers, which are less precise but possess better mechan-ical stability.

In the range above 1234.93 K (solidification point of silver) radiation pyrometers are thenormal instrument.

Equilibrium Conditions T90 / K t90 / °C

Vapor pressure of Helium 3...5 -270.15...-268.15

Triple point of equilibrium Hydrogen 13.8033 -259.3467

Vapor pressure of equilibrium Hydrogen (329 hPa)(1022 hPa)

~ 17~ 20.3

~ -256.15~ -252.85

Triple point of Neon 24.5561 -248.5939

Triple point of Oxygen 54.3584 -218.7916

Triple point of Argon 83.8058 -189.3442

Triple point of Mercury 234.3156 -38.8344

Triple point of Water 273.16 0.01

Melting point of Gallium 302.9146 29.7646

Solidification point of Indium 429.7485 156.5985

Solidification point of Tin 505.078 231.928

Solidification point of Zinc 692.677 419.527

Solidification point of Aluminum 933.473 660.323

Solidification point of Silver 1234.93 961.78

Solidification point of Gold 1337.33 1064.18

Solidification point of Copper 1357.77 1084.62

24

2.2 Basics of Temperature Measurement

2.2.1 The Physical Concept of Temperature

Temperature can be viewed as a measure of the statistically determined averagevelocity of the molecules in a body and thereby it is kinetic energy. In order to warm abody from temperature T1 to T2, energy must be added. How much depends to somedegree on the number of molecules (the amount of material) and their size. In order todescribe the thermodynamic energy level of the body by its temperature, the velocitydistribution of its molecules must be determined based on statistical principles. Thusthe laws of Thermodynamics only apply when a sufficiently large number of moleculesare present.

In modern Thermodynamics the temperature of a body is described as a type of heatpotential, with the property to add or remove heat (heat sources and heat sinks). So thetemperature gradient (the direction of the greatest temperature difference) defines thedirection of the greatest heat effect within a body. The direction of the heat effect is al-ways from the higher to the lower temperature.

Although this statement may appear trivial, it is of fundamental importance when usingcontacting thermometers.

2.2.2 The Technical Significance of Temperature

Temperature is one of seven basic values in the current SI-System of Units and at thesame time, probably the most important parameter in measurement technology.

Temperature measurements can be roughly divided in three application categories:• Precision temperature measurements for scientific and basic research• Technical temperature measurements for measurement and control technology• Temperature monitoring using temperature indicators.

The goal of the technical temperature measurement is to strive for a practical solutionfor every application requirement, which should be an optimum for the required mea-surement accuracy at acceptable costs.

Of the many methods used for temperature measurements, and of those described indetail in this handbook, the electrical temperature sensors have a dominant position inthe measurement and control technology. They convert the measured value into anelectrical signal.

25

2.2.3 The Thermoelectric Effect

The Seebeck-Effect together with the Peltier and Thomson Effect belongs to a groupof thermoelectrical effects. Its discovery has been attributed to T. J. Seebeck. In theyear 1822 he published the observation that a current can be recognized in an electricalcircuit comprising two dissimilar metal conductors, when each of the two connectionpoints of the conductors is at a different temperature level. The cause of this thermalcurrent is the generation of a thermal voltage (thermal force) whose magnitude is pro-portional to the temperature difference between the hot and cold ends and additionallyis a function of the applied material combination.

As early as 1826 A. Becquerel recommended a Platinum-Palladium thermocouple fortemperature measurement.

Theory of the Thermoelectric Effect

The temperature dependence of the electron potentials, which cause a charge shift inan electrical conductor when it is placed in a nonhomogeneous temperature field, isconsidered today as the origin of the thermoelectrical effects.

Simply stated: the free charge carriers (electrons) in a one side warmed conductor dis-tribute themselves in a nonhomogeneous manner so that a potential difference (ther-mal voltage) is generated. At the cold end more electrons accumulate while at the hotend, the electron quantity is decreasing. Therefore it is plausible that even in a singleelectrical conductor in a temperature field a thermal voltage is generated.

This thermal voltage can only be measured if a second conductor is added (thermocou-ple), provided that the temperature dependence of this effect is different in the secondconductor from that in the first conductor (see Fig. 2-2).

26

27

Fig. 2-2: Generation of a thermal voltage

If the thermal voltage effects in both conductors are the same (e.g. for identical conduc-tor materials), then the effects cancel each other and no thermal voltage can be mea-sured.

It is important that this thermal voltage effect is the result of a volume diffusion effect ofthe charge carriers and not a contact voltage phenomenon between the two materials.Therefore it is understandable that the thermal voltage is produced along the entirelength of the thermocouple and not only at the “hot“ connection between the two legs.

Uniform electron distribution for a homogeneous temperature distri-bution in a conductor

Electron depletion at the hot end

Dissimilar electron concentration inthe circuit consisting of two differentconductors

20 °C 20 °C

20 °C

Cu

+

+

-

-

988 °C

988 °CNiCr

NiAl

20 °C

20 °C

U

40

.0m

V

a)

b)

c)

Principles

The Law of Linear Superposition (Superposition Principle) applies to thermocouples,if one visualizes a thermocouple as a series circuit consisting of a (infinite) number ofindividual elements. The thermal voltage generated in the thermocouple is the same asthe sum of the thermal voltages generated in the individual elements. An additional hotzone added between the hot and the cold end therefore has no effect on the resultantthermal voltage, since the additional added thermal voltages cancel each other.

Fig. 2-3: Superposition of thermal voltages

The Law of Homogeneous Temperature states that the thermal voltage in a conductorin a homogeneous temperature field is equal to zero. Therefore the thermal voltages ina thermal circuit (series circuit) made up of any number of different material combina-tions is also equal to zero, if all the components are at the same temperature. For prac-tical application this means that even nonhomogeneous thermocouple wires or plugconnections of different materials have no effect as long as no temperature differenceexists at that location. Therefore design care must be exercised, especially in the areaof plug connections. E.g. a massive thermal insulation (isothermal block) may be usedto achieve a homogeneous temperature.

The Law of a Homogeneous Circuit states, that the temperature of homogeneous con-ductors between two measurement locations does not have any effect on the resultantthermal voltage. Of greater importance is the reverse conclusion: if the resultant ther-mal voltage changes through regions of nonhomogeneous temperatures (with constanthot and cold ends) then the conductor material in not homogeneous. Nonhomoge-neous conditions can occur during production, or already during use (mechanical or

20 °C(68 °F)

e1

e2

e3

e

e = e + e + e1 2 3

1000 °C(1832 °F)

800 °C(1472 °F)

600 °C(1112 °F)

28

29

thermal overstressing) of thermocouples. Of course, the nonhomogeneous conditionswill have no effect if they are in a homogeneous temperature field.

Fig. 2-4: Thermal circuit: c = Metering point; a, b = Thermal legs; d, e = Reference junction

Derived Fundamental Conclusions for the Use of Thermocouples:

• In a homogeneous temperature field no thermal voltage is generated.

• In a homogeneous conductor the magnitude of the thermal voltage is only a functionof the temperature difference between the ends of the conductor.

• The junction of a thermocouple does not generate any thermal voltages.

2.2.4 The Temperature Dependent Ohmic Resistance

The electrical conductivity of all metals increases greatly with decreasing tempera-tures. The electrical conductivity of a metal is based on the movement of its conductionelectrons, the so called electron gas. It consists of the outer electrons of the metalatoms. The atoms of the metal form a dense ion lattice structure. The lattice atomsoscillate. As the temperature increases the oscillation amplitude increases. Thisimpedes the motion of the conduction electrons, resulting in a temperature dependentincrease of the electrical resistance.

This effect is described as a positive temperature coefficient (Tc) of the electricalresistance. It is utilized as the measurement effect. Additionally, flaws in the crystallinestructure of the metal interfere with the electron flow. These flaws include foreign ormissing lattice electrons, lattice faults at the particle boundaries and atoms in the latticeinterstices. Since these interference effects are temperature independent, they resultin an additional constant resistance value.

a

b

d

e

c

Therefore the relationship between temperature and electrical resistance is no longerlinear, but can be approximated by a polynomial. Metals, which are suitable for use asresistance thermometers, should have a high Tc, so that the temperature dependentresistance changes are pronounced. There are additional requirements for the materi-als including high chemical resistance, easy workability, availability in a very pure stateand excellent reproducibility of the electrical properties. Also the resistance materialsmay not change their physical and chemical properties in the temperature range inwhich they are to be used. Freedom from hysteresis effects and a high degree of pres-sure insensitivity are further requirements.

Platinum, in spite of its high price, has become dominant as the resistance material forindustrial applications . Alternative materials such as Nickel, Molybdenum and Copperare also used, but play a subordinate role at this time.

30

Platinum Resistance Thermometer Curves

For Platinum the resistance to temperature relationships are especially easy to de-scribe. A polynomial of this form suffices:

Rt = R0 (1 + At + Bt2) for t ≥ 0 °C (1)Rt = R0 (1 + At +Bt2 +C(t-100)t3) for t < 0 °C (2)

The value R0 is the resistance of the thermometer at 0 °C. The coefficients A, B and C,as well as all the other important properties which the Platinum resistance thermome-ters must satisfy are contained in Standard EN 60751.

Callendar in 1886 had already formulated the relationship as a quadratic equation fortemperature ranges > 0 °C. He first defined by using a strictly linear approach similarto that for gas thermometers, a so called Platinum temperature tp using the expression:

If one substitutes for α the average temperature coefficient between 0 °C and 100 °C,the equation gives a linear relationship between the resistance Rt and the temperaturetp, in which tp not only agrees at 0 °C but also at 100 °C with the actual temperature t.For all other temperatures the calculated value of tp differs from the true temperature t.

By introducing a second constant δ, the differences between the true temperature t andthe Platinum temperature tp are taken into account:

This gives the “historical“ form as:

This equation is known as the Callendar-Equation. The basic Callendar-Equation how-ever, leads quickly to appreciably large errors for temperatures < 0 °C. The equationwas improved by van Dusen in 1925 by the introduction of an additional correction fac-tor with a constant value β (β is equal to zero for temperatures ≥ 0 °C). This modifiedequation is known as the Callendar-van Dusen-Equation.

tR R

R RRRp

t= ×−−

= × −1001 10

100 0 0α α(3)

R R tt t

t = × + + ×⎛⎝⎜

⎞⎠⎟× −

⎛⎝⎜

⎞⎠⎟

⎛⎝⎜

⎞⎠⎟0 1

1001

100α αδ (4)

t tt t

p− = ×⎛⎝⎜

⎞⎠⎟ −

⎛⎝⎜

⎞⎠⎟

⎡

⎣⎢

⎤

⎦⎥δ

100 100

2

(5)

31

From a mathematical standpoint, there are no differences between the curves in theDIN EN standards and Callendar-van Dusen-Equation. In both cases the curves aredefined by three or four (at t < 0 °C) coefficients. It is relatively simple to convert theconstants A, B, C into a, d and b.

For years the formulation of Callendar-van Dusen enjoyed great popularity because ofthe simplicity by which the constants can be determined directly by calibrating at differ-ent temperatures (0 °C, 100 °C etc.). Furthermore, the parameters α and δ can essen-tially be considered to be material properties. In this case, the α-value provides infor-mation about the purity of the used Platinum and the δ-value about the actualmechanical construction of the thermometer (voltage freeness).

Since the introduction of ITS-90, the boiling point of water (100 °C) is no longer adefined point in the temperature scale, and since that temperature is essential fordetermining the α-value in the Callendar-van Dusen equation, this formulation has lostits significance in recent times.

Typically, the curves today are defined by equations (1) and (2), with the coefficientspublished in the Standard EN 60751:

A = 3.9083 x 10-3 K-1

B = -5.775 x 10-7 K-2

C = -4.183 x 10-12 K-4

32

2.3 The Principles of Temperature Measurement

The development of temperature measurement has and is occurring in parallel with thetechnological developments. Thereby only a portion of the new measurement methodshave replaced the older ones. They have actually expanded their scope allowingtemperature measurement to be made in areas where in the past none or only veryrestricted ones were possible.

In the following table a number of measurement methods will be presented in con-densed form together with their application ranges and significance. The table below isbased on the temperature measurement methods described in VDI/VDE 3511 Sheet1)

Tbl. 2-2: Measurement methods

Measurement Methods Range Error Limits

from to °C (°F)

Mechanical Thermometers

Liquid filled glass thermometer

Non-wetting liquid -38 (-36) 630 (1166) according to DIN 16178 Sheet 1Wetting liquid -200 (-328) 210 (410)

Indicator Thermometers

Bimetal thermometer -50 (122) 400 (752) 1...3 % of the indicator range

Rod expansion thermometer 0 (32) 1000 (1832) 1...2 % of the indicator range

Liquid filled spring thermometer -30 (-22) 500 (932) 1...2 % of the indicator range

Vapor pressure spring thermometer -200 (-328) 700 (1292) 1...2 % of the scale length

Thermocouples

Cu-CuNi, Type U, T -200 (-328) 600 (1112) 0.75 % of the reference value of the temperature, at leastaccording to EN 60584

Fe-CuNi, Type L, J -200 (-328) 900 (1652)

NiCr-Ni, Type K, NiCrSi-NiSi, Type N 0 (32) 1300 (2372)

PtRh-Pt, Type R, S 10 % Rh (S); 13 % Rh (R)

0 (32) 1600 (2912) 0.5 % of the reference value of the temperature, at least according to EN 60584Pt Rh30-PtRh6, Type B 0 (32) 1800 (3272)

Resistance Thermometers with Metal Resistors

Pt-resistance thermometer -200 (-328) 1000 (1832) 0.3...4.6 °C (32.54...40.28 °F)depending on the temperature(EN 60751)

Ni-resistance thermometer -60 (-76) 250 (482) 0.4...2.1 °C (32.72...35.78 °F)depending on the temperature(according to DIN 43760)

33

Tbl. 2-3: Continuation – measurement methods

A differentiation is made between contacting temperature measurement methods andnon-contacting measurement methods. The contacting measurement methods, whichare dominant in industrial temperature measurement technology, can be further subdi-vided into mechanical and electrical contacting thermometers.

Measurement Methods Range Error LImits

from to °C (°F)

Semiconductor Resistance Thermometers

Hot wire resistance thermometer,thermistor

-40 (-40)-60 (-76)

-100 (-148)

180 (356)200 (392)400 (752)

0.1...1 °C (0.2...2 °F);0.5...2.5 °C (1...5 °F)depending on the temperature

Cold wire resistance thermometer 200 (392) 2...10 °C (4...18 °F)

Silicon measurement resistor -70 (-94) 175 (347) 0.2...1 °C (0.4...2 °F)

Semiconductor diodes/integratedtemperature sensor

160 (320) 0.1...3 °C (.02...6 °F) depending on the temperature

Radiation Thermometers

Spectral pyrometer 20 (68) 5000 (9000) 0.5...1.5 % of the temperature,but at least 0.5...2 °C (1...4 °F) in the range from -100...400 °C (-148...752 °F)

Infrared radiation pyrometer -100 (-148) 2000 (3600) 0.5...1.5 % of the temperature,but at least 0.5...2 °C (1...4 °F) in the range from -100...400 °C (-148...752 °F)

Total radiation pyrometer -100 (-148) 2000 (3600) 0.5...1.5 % of the temperature,but at least 0.5...2 °C (1...4 °F) in the range from -100...400 °C (-148...752 °F)

Ratio pyrometer 150 (302) 3000 (5400) 0.5...1.5 % of the temperature,but at least 0.5...2 °C (1...4 °F) in the range from -100...400 °C (-148...752 °F)

Thermography instrument -50 (-58) 1500 (2900) 0.5...1.5 % of the temperature,but at least 0.5...2 °C (1...4 °F) in the range from -100...400 °C (-148...752 °F)

Quartz thermometer -80 (-112) 250 (482) Resolution 0.1 °C (0.2 °F)

Thermal noise thermometer -269 (-452) 970 (1778) 0.1 %

Ultrasonic thermometer 3300 (6000) approx. 1 %

Gas thermometer -268 (-450) 1130 (2066) depending on design

Optical Methods

Fiber optic luminescence thermometer

400 (752) 0.5 °C (32.9 °F)

Fiber optic measurement systembased on Raman-Radiation

600 (1112) 1 °C (33.8 °F)

34

2.3.1 Mechanical Contacting Thermometers

The expansion of gases, liquids and solids as the temperature increases is experi-enced daily. To use this effect for temperature measurement in practice, the specificproperties of the material have to be taken into account.

Considering a solid body, the length change (dL) of a bar exposed to a temperaturechange (dt) as a first approximation is proportional to the bar length (L):

dL = a x L x dt

The proportionality factor a (linear thermal longitudinal expansion coefficient) is a prop-erty of the specific material. The integration of this equation, beginning with the lengthof the bar at a given temperature, gives the length of the bar at temperature t. Since theproportionality factor a can only be considered as linear over small temperature ranges,higher order terms must be included in the calculation for larger temperature differ-ences.

The technical application of this sensor principle leads to bar and bimetal thermome-ters. They are installed in industrial applications where local indicators are all that isrequired.

The dependence of a liquid volume on temperature can be utilized in an analogousmanner. In this case, a cubic expansion coefficient ß applies. This coefficient is also aproperty of the type fluid being employed.

Liquid filled thermometers are encountered as glass thermometers (clinical thermome-ters, filament thermometers) or as direct indicators for machine glass thermometers.They are used for local temperature monitoring of liquids, gases and steam in pipelinesand tanks.

A variant is the liquid filled spring-loaded thermometer. In this design a capillary tubecompletely filled with liquid is placed in a metal housing. Changes in the temperatureproduce an increase or decrease in the pressure which is transmitted over a membraneto an elastic, deformable spring. Newer designs measure the pressure differences anduse a pressure transmitter to display the temperature values.

If the liquid is replaced by a gas, then essentially the same design principles can beapplied as for the liquid filled spring-loaded thermometers. For gas pressure ther-mometers the ideal gas equation is used to evaluate the temperature relationships ofthe gas. It can be considered either at a constant pressure or a constant volume. Gaspressure thermometers can also be used for local measurements and as temperatureindicators, e.g., in machines. For both the liquid filled as well as the gas pressure ther-mometers it is essential that the measurement body is completely surrounded by themedium whose temperature is being measured.

35

2.3.2 Electric Contacting Thermometers

Thermocouples

If two dissimilar metals are connected together, a voltage is generated. This voltage isa function of the combined metals and the changes in the temperature (Thermal Volt-age).

Resistance Thermometers

Metals as electrical conductors offer a resistance to the current flowing through themas a result of the oscillations of the lattice atoms. The magnitude of the resistance isdependent on the temperature.

Semiconductor Sensors

Semiconductors also exhibit a characteristic change of their electrical resistance whenthe temperature changes. A differentiation is made between cold wire (PTC-resistors),and hot wire (NTC-resistors or thermistors).

Semiconductor PTC’s are polycrystalline ceramics based on barium titanate. This ma-terial combination generates, in addition to the semiconductor effect, ferroelectricity.This leads to a very large increase of the electrical resistance in a narrow temperaturerange. The ideal application range is between -50 °C (-58 °F) and 150 °C (302 °F). Ad-ditionally the PTC's have a leap-temperature at which the increase of the resistancechanges dramatically. For this reason they are specially suitable for use as temperaturelimit switches for machines and systems.

The NTC's, made of a mixture of polycrystalline ceramic oxides, with NiO, CaO, Li2Oadditives, work differently. They are manufactured using a high temperature sinter pro-cess. They are normally used in a temperature range from -110 °C (-166 °F) to 300 °C(572 °F). For the NTC's the relationship between the resistance and the temperatureis almost exponential. Because of the non-linear curve and the drift when subjected totemperature change stresses, the use of NTC's in industrial measurement technologyis limited. Due to their low cost they are primarily used in the appliance and automotiveindustries and in other mass produced consumer product industries.

36

Silicon Measurement Resistors

Silicon also possesses a pronounced positive temperature coefficient and can there-fore be used for temperature measurements between -70 °C (-94 °F) and 160 °C(320 °F), over which range the curves deviate only slightly from linear. Silicon measure-ment resistors have a high temperature coefficient and long term stability. To date theyhave not found wide acceptance.

2.3.3 Additional Contacting Measurement Principles

Oscillating Quartz Temperature Sensors

Oscillating quartz, cut at a specific angle, has a high temperature coefficient for itsresonant frequency (approx. 100 ppm/K). This quartz can be used for temperaturemeasurement. Its frequency vs. temperature curve is not linear, but is very repro-ducible. It can be described by a 5th order polynomial. The application range for thesesensors is typically between -80 °C (-112 °F) and 300 °C (572 °F). The expected largeindustrial use of the oscillating quartz thermometers which have been introduced in1986, has never been realized.

Thermal Noise Thermometers

For determining thermodynamic temperatures the high accuracy thermal noise ther-mometer is suitable. In the temperature range 300 °C (572 °F) to 1200 °C (2192 °F) itachieves a measurement uncertainty of 0.1 %. The measurement principle is based onthe temperature dependence of the average velocity of the electrons in an unloadedresistor.

There are however problems in practical applications, because the thermal noise inamplifier assemblies, connection cables and other components require costly elimina-tion effort. The use of thermal noise thermometers, due to their high cost, is limited toapplications where the properties of the other more common thermometers are not sta-ble and cannot readily be removed for recalibration. Thermal noise thermometers forexample are not affected by nuclear radiation in a reactor. They are often used in com-bination with other electrical thermometers.

Fiber Optic Temperature Measurement Systems

This is a special measurement system, in which the locally temperatures in a glass fibercable can be measured. It consists of a measurement instrument (laser source, opticalmodule, receiver and evaluation unit) and a quartz glass fiber cable. Thermal molecularoscillations of the quartz glass material cause a Raman-Radiation within the fiber opticcable. The Anti-Stokes portion of the Raman-radiated light is a function of the temper-ature. The local fiber temperature is determined from its intensity. In this way the tem-perature distribution in cables, wires, pipes etc., can be measured by using fiber optics.It is used to detect local temperature differences (temperature increases), which indi-cate errors or damages to cables, wires and pipes.

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Fiber Optic Thermometers

The fiber optic thermometer consists of a glass fiber at the end of which a crystal ismounted, e.g., a Cr-YAG-Crystal. It is excited by a pulsed luminescent radiation. Thelength of the excitation during the excitation conditions and therefore the decay time ofthe luminescent radiation decreases with increasing temperature. The applicationrange is between -50 °C (-58 °F) and 400 °C (752 °F). Fiber optic thermometers areadvantageous in areas where high electromagnetic fields may be expected as well asin potentially explosive atmospheres. Also included is the use in industrial microwaveapplications, (e.g., driers).

2.3.4 Non-contacting Temperature Measurement

Infrared Measurement Technology, Pyrometry

The recognition of radiation heating of a hot body belongs to the basic experiences ofmankind. The measurement of temperature radiation (infrared radiation) to determinethe temperature of a body is one of the newer temperature measurement methods inthe industrial sector.

In a pyrometer the thermal radiation emanating from a body is focussed by a lens on aradiation receiver. As receiver, thermocouples, photomultipliers, photoresistors, photo-diodes etc. can be used. The “heat radiation“ generates an electrical signal which canbe utilized to determine the temperature.

A differentiation is made between the various pyrometer types, such as total radiationpyrometer, spectral pyrometer, radiation density pyrometer, distribution pyrometer anddisappearing filament pyrometer.

Pyrometers can replace contacting thermometers only in a few applications. More oftenthey are used to supplement contacting methods in areas where no or unsatisfactoryresults occur. Basically, pyrometry, in contrast to contacting methods, can only mea-sure the heat on the surface.

The application focus is the temperature measurement on surfaces, on fast movingparts, on objects with minimal heat capacity or heat conductivity, on objects with fastchanging temperatures and on objects which are not easily accessible. Also productswhich cannot be touched due to sterilization or processing constraints (e.g. in the foodindustry) are suitable for temperature measurements with pyrometers.

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Thermal Imaging Cameras

In principle the thermal imaging camera has the same physical effects as a pyrometer.However, the pyrometers determine the average temperature of the entire surfacebeing measured while the thermal imaging camera produces a thermal picture of theobject. Area sensors are used for this. The number of available detector elementsdefines the quality of the picture.

Thermal imaging cameras are primarily used today to monitor and control machinery,electrical and mechanical systems and objects in which localized heating could dam-age or destroy the item as well as where heat losses are to be determined.

Acoustic Measurement Methods

The dispersion velocity of sound in various materials is a function of the temperature(the absolute temperature is proportional to the square of the sound velocity). Thisproperty can be used as temperature measurement method Two methods are utilized:the resonant method (e.g. quartz resonators) and non-resonant methods, which utilizefor example a sound transit time measurement.

Measurement sensors for non-resonant solid body sensors consist of a Rhenium wirewhich operates based on a Pulse-Echo principle. Acoustic measurement methods areespecially suitable for high temperatures. They are used to determine the temperatureprofiles in furnaces such as those used in waste incineration systems. A disadvantageof the acoustic method is its relatively high cost.

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3 Industrial Temperature Measurement UsingElectrical Contacting Thermometers

3.1 Sensors

3.1.1 Thermocouples

The simplest thermocouple designs are those made using insulated thermal wires. Theusual insulation materials are glass fibers, mineral fibers, PVC, Silicone rubber, Teflonor Ceramic. They must be compatible with the installation requirements, which includechemical resistance, temperature resistance, moisture protection, etc.

A special design of insulated thermocouple wires are mineral insulated thermocouplecables.

Thermocouples according to EN 60584/IEC 584

The thermocouples described in these standards are generally divided into two groups.The precious metal thermocouples Types S, R and B, and the base metal thermocou-ples Types E, J, K, N and T.

These standardized types are incorporated in many international standards and, rela-tive to their basic thermal voltage values, are compatible. For example, it is possible touse a Type K according to EN 60584 as a Type K according to ANSI-MC 96.1, or even,as a Type K according to JIS C 1602. Only in the deviation limits of the accuracy class-es may differences be found. Detailed information for each type is available in thecorresponding standard.

40

Fig. 3-1: Basic value curves for thermocouples according to EN 60584

-300 -100 100 300 500 700 900 1100 1300 1500 1700 1900-10

-5

0

5

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15

20

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45

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Type B

Type S

Type RType T

Type N

Type K

Type E

Type J

The

rmal

Vol

tage

[mV

]

Temperature [°C]

41

Type S (Pt10%Rh-Pt):Defined Temperature Range -50...1768 °C (-58...3214 °F).The Type S thermocouple was developed and tested over 100 years ago by H. LeChat-elier. These early investigations already indicated that the primary advantages of theType S were the reproducibility of its measurements, its stability and its applicability tomiddle high temperatures. This was the primary reason why it has been selected as thestandard thermocouple since 1927 (ITS 27) until the introduction on 1st January 1990of ITS 90.

The nominal composition of Type S consists of Platinum-10%Rhodium comparedagainst Platinum. The positive conductor (SP) contains 10.00 ± 0.05 % Rhodium. Forthe alloy, Rhodium with a purity of ≥ 99.98 %, and Platinum with a purity of ≥ 99.99 %should be used. The negative conductor (SN) is made of Platinum with ≥ 99.99 % pu-rity. The Type S thermocouple can be used in a temperature range from -50 °C (-58 °F)almost to the melting point of Platinum at 1769 °C (3216 °F). It should be noted that theoutput voltages for continuous operation are only stable to about 1300 °C (2372 °F).

The life span of the thermocouple is limited at the higher temperatures due to the phys-ical problem of grain growth in the wires. This reduces the mechanical strength, alsoimpurities can diffuse into the wires and thereby change the thermal voltage. The ther-mocouple is most stable when it is operated in a clean, oxidizing environment (e.g., air),although short term use in inert, gaseous atmospheres or in a vacuum is possible.Without suitable protection, it should not be used in reducing environments, in metallicor nonmetallic vapors containing, for example, Lead, Zinc, Arsenic, Phosphorous, orSulphur, or in lightly reducing oxides.

Decisive for the stability at higher temperatures is furthermore the quality of the protec-tion tube and insulation material. Ceramic, in particular Aluminum oxide (Al2O3) with apurity of ≥ 99 %, is best suited for this purpose. Metallic protection tubes should neverbe used at the higher temperatures > 1200 °C (2192 °F).

Type R (Pt13%Rh-Pt)Defined Temperature Range -50...1768 °C (-58...3214 °F).At the beginning of the twentieth century it was noticed that the Type S thermocouplesused in the USA and in Europe showed large differences in their thermal voltagesamong each other. In some temperature ranges differences up to 5 °C (9 °F) were not-ed. The reason was that in Europe the Rhodium used for the alloy was contaminatedwith 0.34 % iron. Since many instruments were already calibrated with these “contam-inated Type S“ thermocouples, the Type R was developed as a compromise, which hascomparable thermal voltages.

42

The nominal composition of Type R consists of Platinum-13%Rhodium comparedagainst Platinum. The positive conductor (RP) contains 13.00 ± 0.05 % Rhodium. Forthe alloy Rhodium with a purity of ≥ 99.98 %, and Platinum with a purity of ≥ 99.99 %should be used. The negative conductor (RN) is made of Platinum with ≥ 99.99 % pu-rity.

For the most part of their defined temperature range, Type R thermocouples have atemperature gradient about 12 % higher (Seebeck-Coefficient) than the Type S ther-mocouples. The remaining material properties are identical to the Type S.

Type B (Pt30%Rh-Pt6%Rh)Defined Temperature Range 0...1820 °C (32...3308 °F).The Type B thermocouple was introduced into the market in the fifties by Degussa/Ha-nau, Germany, and was called PtRh18, a name which is still used in some areas today.It was designed to satisfy the requirements for temperature measurements in the range1200...1800 °C (2192...3272 °F).

The nominal composition for Type B consists of Platinum-30%Rhodium comparedagainst Platinum-6%Rhodium. The positive conductor (BP) contains 29.60 ± 0.2 % andthe negative conductor (BN) 6.12 ± 0.2 % Rhodium. For the alloy Rhodium with a purityof ≥ 99.98 %, and Platinum with a purity of ≥ 99.99 % should be used. They also con-tain a very small amount of Palladium, Iridium, Iron and Silicon impurities.

Investigations have shown, that thermocouples, in which both conductors are made ofPt-Rh alloys, are suitable and reliable for measuring high temperatures. They havedecided advantages over Types R and S, with regard to improved stability, increasedmechanical strength and higher temperature capabilities. The maximum applicationtemperature range for Type B is essentially limited by the melting point of the Pt6%Rhconductor (BN) at approx. 1820 °C (3308 °F).

A Type B thermocouple can, if handled properly, be operated for a number of hours attemperatures to 1790 °C (3254 °F), and for a few hundred hours at temperatures to1700 °C (3092 °F), without an appreciable change in the output thermal voltage values.The thermocouple operates most reliably when operated in clean, oxidizing environ-ment (air), a neutral atmosphere or in a vacuum. Suitable protection is mandatory if itis to be used in reducing environment as well as in environments with destructivevapors or other contaminants which might react with the Platinum materials.

The selections of suitable protection tube and insulation materials are the same as forType S.

Type J (Fe-CuNi)Defined Temperature Range -210 ...1200 °C (-346...2192 °F).Because of its relatively steep temperature gradient (Seebeck-Coefficient) and low ma-terial costs, Type J, in addition to Type K, is one of the most commonly used industrialthermocouples today.

43

Nominally, Type J consists of Iron compared against a Copper-Nickel alloy. The posi-tive conductor (JP) is made of commercially available Iron with a purity of approx.99.5 % with approx. 0.25 % Manganese and approx. 0.12 % Copper, as well as smallerquantities of Carbon, Chromium, Nickel, Phosphorous, Silicon and Sulphur.

The negative conductor (JN) is made of a Copper-Nickel alloy, which is calledConstantan. It should be noted that alloys designated as Constantan which are avail-able commercially, may have a Copper content between 45 % and 60 % . For negativeconductor (JN) usually an alloy with approx. 55 % Copper, approx. 45 % Nickel andapprox. 0.1 % each of Cobalt, Iron and Manganese is used.

It should be stressed, JN conductors cannot generally be exchanged with conductorsof Types TN or EN, even though all consist of Constantan. Manufacturers of Type Jthermocouples usually combine one particular Iron melt with an appropriate Copper-Nickel batch in order to achieve the basic thermal voltage values of Type J.

Since the composition of both conductors (JP and JN) can vary from manufacturer tomanufacturer, it is not advisable to use individual conductors from more than onemanufacturer, otherwise the required tolerance classes in some instances may beexceeded.

Although the basic values for Type J are defined in the standard for a temperaturerange from -210...1200 °C (-346...2192 °F), the thermocouples should only be used ina range of 0...750 °C (32...1382 °F) when operating continuously. For temperaturesover 750 °C (1382 °F) the oxidation rate for both conductors increases rapidly.

Further reasons for the restricted temperature range are to find in the special propertiesof the positive conductor (JP). Since Iron rusts in damp environments and becomesbrittle, it is not advisable to operate Type J thermocouples at temperatures below 0 °C(32 °F) without suitable protection. In addition, Iron experiences a magnetic change at769 °C (1462 °F) (Curie point) and at approx. 910 °C (1670 °F) an Alpha-Gamma crys-tal structure change occurs.

Both effects, particularly the latter, have a significant influence on the thermoelectricproperties of the Iron and therefore on the Type J thermocouple. Should a Type J beoperated above 910 °C (1670 °F), the output thermal voltages will change appreciably,especially when cooled quickly to lower temperatures.

In the temperature range 0...760 °C (32...1400 °F) the Type J can be used in vacuum,oxidizing, reducing or inert atmospheres. In Sulphur containing environments, suitableprotection should be employed at temperatures above 500 °C (932 °F).

44

Type K (NiCr-NiAl)Defined Temperature Range -270...1372 °C (-454...2501 °F).Since this thermocouple type for middle temperatures is more resistant against oxida-tion than Types J and E, it is used in many applications today for temperatures over500 °C (932 °F). Nominally, the thermocouple contains a Nickel-Chromium alloy com-pared against a Nickel-Aluminum alloy. The positive conductor (KP) is identical to thematerial of Type E positive conductor and consists of 89 to 90 % Nickel, 9 to 9.5 %Chromium, approx. 0.5 % Silicon, approx. 0.5 % Iron and smaller amounts of Carbon,Manganese and Cobalt. The negative conductor (KN) contains 95 to 96 % Nickel, 1 to2.3 % Aluminum, 1 to 1.5 % Silicon, 1.6 to 3.2 % Magnesium, approx. 0.5 % Cobalt, aswell as minimal traces of Iron, Copper and Lead.

The basic values for Type K thermocouples are defined for the range from -270...1372 °C (-454...2501 °F). It should be noted that at temperatures over 750 °C(1382 °F) the oxidation rate in air for both conductors increases sharply. Also, it shouldnot be installed without suitable protection at higher temperatures in Sulphur contain-ing, reducing or alternately oxidizing and reducing atmospheres.

There are also effects to be considered here which drastically change the output ther-mal voltages.

If a Type K is exposed for longer periods of time to higher temperatures in a vacuum,then the Chromium volatilizes out of the alloy of the KP conductor (“vacuum sensitivi-ty“). If on the other hand, a smaller, but not negligible amount of oxygen or steam ispresent at the thermocouple, the KP conductor may be subjected to the so called“green rot“. In these situations, the oxidation attacks only the easier to oxidize Chromi-um without oxidizing the Nickel. At temperatures between 800 °C and 1050 °C (1472...1922 °F) this is most severe. “Green rot“ and “vacuum sensitivity“ produce irreversibleeffects on the composition of the conductor and thereby on the thermal voltage. Erro-neous measurements of more than 100 °C (212 °F) are possible!

In addition, a magnetic change in the Nickel leg KN occurs at 353 °C (667 °F) (Curiepoint). The Nickel-Chromium alloy of the KP-conductor in the range from 400...600 °C(752...1112 °F) changes from an ordered to an unordered atomic distribution state, theso called “K-Condition“. If a Type K is operated at temperatures over 600 °C (1112 °F)and subsequently cooled too quickly, these changes may not be reversible and canchange the output thermal voltages by up to 5 °C (9 °F).

Both effects are reversible, since they can be restored to their original condition byheating to over 600 °C (1112 °F) and then slowly cooling (for additional information seechapter 3.5 "Aging Mechanisms in Temperature Sensors").

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Type N (NiCrSi-NiSi)Defined Temperature Range -270...1300 °C (-454...2372 °F).Type N is the newest thermocouple defined in this standard. It was developed at theend of the sixties and offers distinct advantages due to its higher thermoelectric stabilityat temperatures over 870 °C (1598 °F) and less tendency to oxidize compared againstthermocouples Types J, K and E.

Nominally, the thermocouple consists of a Nickel-Chromium-Silicon alloy comparedagainst a Nickel-Silicon alloy. The positive conductor (NP) contains approx. 84 % Nick-el, 13.7 to 14.7 % Chromium, 1.2 to 1.6 % Silicon, <0.15 % Iron, <0.05 % Carbon,<0.01 % Magnesium, as well as minimal traces of Cobalt. The negative conductor (NN)contains approx. 95 % Nickel, 4.2 to 4.6 % Silicon, 0.05 to 0.2 % Magnesium, <0.15 %Iron, <0.05 % Carbon, as well as small amounts of Manganese and Cobalt. These con-ductors are also known by their trade names Nicrosil (NP) and Nisil (NN).

Of all the base metal thermocouples, Type N is best suited for applications with oxidiz-ing, damp or inert atmospheres. As a result of its relatively high Silicon content, the ox-idation occurs on the surface of the conductor. Tightly adhering and protective oxidesare formed which minimize further corrosion.

In reducing atmospheres or air in the range of 870...1180 °C (1598...2156 °F) the ther-mocouple exhibits a decidedly higher thermoelectric stability than a Type K thermo-couple under the same conditions. Also the “K-State“ which occurs in the Type K is al-most completely suppressed due to the Silicon content. At higher temperatures inSulphur containing, reducing or alternately oxidizing and reducing atmospheres suit-able protection is still necessary.

The “Green rot“ and “vacuum sensitivity“ phenomena described for the Type K thermo-couple do also occur in the Type N, where however, both the Chromium and the Siliconvolatilize in vacuum.

Attention: Type K and N cannot be exchanged for each other!

Type T (Cu-CuNi)Defined Temperature Range -270...400 °C (-454...752 °F).This is one of the oldest thermocouples for low temperature measurements, andis still commonly used in the triple point range for Neon at -248.5939 °C (-415.4690 °F)up to 370 °C (698 °F).

Type T nominally contains Copper compared against a Copper-Nickel alloy. The posi-tive conductor (TP) consists of approx. 99.95 % pure Copper with an Oxygen contentof 0.02 to 0.07 % dependent on the Sulphur content of the Copper. The remainingimpurities amount to approx. 0.01 % in total. The negative conductor (TN) consists ofa Copper-Nickel alloy, also called Constantan with approx. 55 % Copper and 45 %Nickel, as well as approx. 0.1 % each of Cobalt, Iron and Manganese. The TN conduc-tor is identical to and can be interchanged with an EN conductor. It is, however, gener-ally not identical to Type JN conductors.

46

The Type T thermocouple exhibits good thermoelectric homogeneity. Due to the goodheat conductivity of the conductors, problems can occure when used for precision mea-surements, resulting from heat abstraction, particularly if the conductor diameter is verylarge. The Type T can be used in vacuum, oxidizing, reducing or inert atmospheres.

It should be noted that above 370 °C (698 °F) the oxidation rate of the TP-conductorincreases dramatically. It is not recommended to use the thermocouple in hydrogencontaining environments above 370 °C (698 °F) without suitable protection, becausethe TP-conductor could become brittle.

Type E (NiCr-CuNi)Defined Temperature Range -270...1000 °C (-454...1832 °F).The thermocouple has a relatively small heat conductivity, very high resistance inhumid atmospheres, good homogeneity, and a relative steep temperature gradient(Seebeck-Coefficient) at extremely low temperatures. For these reasons it has becomethe most common thermocouple for low temperature measurements. Above 0 °C(32 °F) it has the steepest temperature gradient of all the thermocouples defined in thestandard.

Type E nominally consists of a Nickel-Chromium alloy compared against a Copper-Nickel alloy. The materials of the positive conductor (EP) are identical to those alreadydescribed for the KP-conductor in the Type K, and the negative conductor (EN) is thesame as the TN-conductor in the Type T . The Type E thermocouple can be used in atemperature range from -270...1000 °C (-454...1832 °F). For temperatures over 750 °C(1382 °F) the oxidation rate in air for both conductors is high. Since the EP-conductoris identical to the KP-conductor, the same effects of “vacuum sensitivity“, “K-State“ and“Green rot“ already described are also applicable to this thermocouple.

The Type E is essentially insensitive to oxidizing or inert atmospheres. In Sulphur con-taining, reducing or alternately oxidizing and reducing atmospheres suitable protectionis still necessary.

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Tbl. 3-1: Classes and deviation limits for thermocouples acc. to EN 60584 (former IEC 584)

Thermocouples according to DIN 43710

The thermocouples Type U (Cu-CuNi) and Type L (Fe-CuNi) defined in this standardare no longer included in any current national or international standards. This has notprecluded the continued use of these thermocouples in many applications. They werenot included in EN 60584 or IEC 584, but replaced by the Types J and T.

DIN 43710 recommends that these thermocouples should not be used for any newapplications and if existing installations are updated or reworked, the thermocouplesshould be replaced by Types J and T.

Attention: They cannot simply be exchanged for one another!

Type Class 1 Class 2 Class 3Type R, Type STemperature rangeDeviation limitsTemperature range

Deviation limits

0...1100 °C (32...2012 °F)± 1 °C (1.8 °F)1100...1600 °C(2012...2912 °F)±[1+0.003 x (t -1100)] °C±[1+0.0017 x (t -2000)] °F

0...600 °C (32...1112 °F)± 1.5 °C (2.7 °F)600...1600 °C(1112...2912 °F)± 0.0025 x [t] °C± 0.0014 x [t] °F

–––

–

Type BTemperature range

Deviation limitsTemperature range

Deviation limits

–

–––

–

– 600...1700 °C(1112...3092 °F)± 0.0025 x [t] °C± 0.0014 x [t] °F

600...800 °C(1112...1472 °F)± 4 °C (7.2 °F)800...1700 °C(1472...3092 °F)± 0.005 x [t] °C± 0.0028 x [t] °F

Type JTemperature rangeDeviation limitsTemperature rangeDeviation limits

-40...375 °C (-40...707 °F)± 1.5 °C (2.7 °F)375...750 °C (707...1382 °F)± 0.004 x [t] °C ± 0.002 x [t] °F

-40...333 °C (-40...631 °F)± 2.5 °C (4.5 °F)333...700 °C (631...1292 °F)± 0.0075 x [t] °C± 0.0042 x [t] °F

––––

Type K, Type NTemperature rangeDeviation limitsTemperature range

Deviation limits

-40...375 °C (-40...707 °F)± 1.5 °C (2.7 °F)375..1000 °C (707...1832 °F)± 0.004 x [t] °C± 0.002 x [t] °F

-40...333 °C (-40...631 °F)± 2.5 °C (4.5 °F)333...1200 °C(631...2192 °F)± 0.0075 x [t] °C± 0.0042 x [t] °F

-167...40 °C(-269...104 °F)± 2.5 °C (4.5 °F)-200...-167 °C (-328...-269 °F)± 0.015 x [t] °C± 0.0008 x [t] °F

Type TTemperature rangeDeviation limitsTemperature rangeDeviation limits

-40...125 °C (-40...257 °F)± 0.5 °C (0.9 °F)125...350 °C (257...662 °F)± 0.005 x [t] °C± 0.0028 x [t] °F

-40...133 °C (-40...271 °F)± 1 °C (1.8 °F)133...350 °C (271...661 °F)± 0.0075 x [t] °C± 0.0042 x [t] °F

-67...40 °C(-89...104 °F)± 1 °C (1.8 °F)-200...-67 °C (-328...-89 °F)± 0.015 x [t] °C± 0.0008 x [t] °F

Type ETemperature rangeDeviation limitsTemperature range

Deviation limits

-40...375 °C (-40...707 °F)± 1.5 °C (2.7 °F)375...800 °C (707...1472 °F)± 0.004 x [t] °C± 0.002 x [t] °F

-40...333 °C (-40...631 °F)± 2.5 °C (4.5 °F)333...900 °C (631...1652 °F)± 0.0075 x [t] °C± 0.0042 x [t] °F

-167...40 °C (-269...104 °F)± 2.5 °C (4.5 °F)-200...-167 °C (-328...-269 °F)± 0.015 x [t] °C± 0.0008 x [t] °F

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Fig. 3-2: Basic curves for thermocouples according to DIN 43710

Type U Cu-CuNi)Defined Temperature Range -200...600 °C (-328...1112 °F).Type U nominally consists of Copper compared against a Copper-Nickel alloy. Thepositive conductor (UP) is made of the same Copper composition as the positive con-ductor described for Type T earlier in this section. The negative conductor (UN) is madeof a Copper-Nickel alloy (Constantan) with approx. 55 % Copper, approx. 44 % Nickeland approx. 1 % Manganese.

-200 -100 0 100 200 300 400 500 600 700 800 900 1000-10

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As a result of these very small differences in their compositions, the basic values forthe thermal voltages for the Type U are different from those for Type T. The remainingmaterial properties are however essentially the same as those for Type T.

Type L (Fe-CuNi)Defined Temperature Range -200...900 °C (-328...1652 °F).Type L nominally consists of Iron compared against a Copper-Nickel alloy. The positiveconductor (LP) is made of the same Iron composition as the positive conductor of TypeJ. The negative conductor (LN) is made of the same Copper-Nickel alloy (Constantan)as the negative conductor of Type U. Therefore the basic values for the thermal volt-ages for Type L are different from those for Type J. The remaining material propertiesare however essentially the same as those for Type J.

Tbl. 3-2: Classes for the deviation limits for thermocouples according to DIN 43710

Non-Standard Thermocouples

In addition to the standardized thermocouples, there is a whole set of non-standardthermocouples for special applications, whose basic values are not included in any cur-rent standard. The basic values for these thermocouples must be established by themanufacturer using individual calibrations.

The most well known include:

Iridium-Iridium rhodium (Ir-Ir40%Rh)For laboratory measurements in neutral or weak oxidizing atmospheres at temper-atures to 2000 °C (3632 °F). The thermocouple consists of very brittle cold rolled steelwires which may not be bent. They are insulated using capillary tubes made of pureAluminum oxide (Al2O3). The thermal voltage is approx. 10 mV at 2000 °C (3632 °F).

Type DIN

Type UTemperature rangeDeviation limitsTemperature rangeDeviation limits

50...400 °C (122...752 °F)± 3 °C (5.4 °F)400...600 °C (752...1112 °F)± 0.0075 x [t] °C± 0.0028 x [t] °F

Type LTemperature rangeDeviation limitsTemperature rangeDeviation limits

50...400 °C (122...752 °F)± 3 °C (5.4 °F)400...900 °C (752...1652 °F)± 0.0075 x [t] °C± 0.0028 x [t] °F

50

Tungsten-Tungsten Rhenium (W-W26%Rh),Tungsten Rhenium-Tungsten Rhenium (W5%Rh-W26%Rh) andTungsten Rhenium-Tungsten Rhenium (W3%Rh-W25%Rh)These thermocouples, identified in the USA by the letters “G“, “C“ and “D“, are de-signed for use in high vacuums and for inert gases to 2320 °C (4200 °F).The thermal voltage is at 2320 °C (4208 °F) for W-W26%Rh approx. 38.6 mV, forW5%Rh-W26%Rh approx. 37.1 mV and for W3%Rh-W25%Rh approx. 39.5 mV.

Pallaplath® (Pt5%Rh-Au46%Pd2%Pt)This thermocouple can be used to 1200 °C (2192 °F) in air, but is not suitable forenvironments containing Silicon or Carbon. It combines the stability of a precious metalwith the high thermal voltages of a base metal thermocouple. The thermal voltage isapprox. 55.4 mV at 1200 °C (2192 °F).

Gold Iron-Chromium (AuFe-Cr)This thermocouple is used primarily for low temperature measurements in a range from-270...-200 °C (-454...-328 °F). At -270 °C (-454 °F) the thermal voltage is approx.4.7 mV.

3.1.2 Mineral Insulated Thermocouple Cables

Mineral insulated thermocouple cables have an outer sheath made of metal and for anyone design, 2...6 internal wires made of a thermal material. The insulation consists ofhighly compressed metal oxide powder, preferably Magnesium oxide MgO, or Alumi-num oxide AI2O3.

They are used where particularly high mechanical, electrical and chemical stability isrequired. Because they are readily bendable, these cables are preferred where prob-lematic space requirements exist and a flexible installation is desired, e.g. in machinebuilding, laboratories and experimental test facilities.

The minimum bending radius is approx. 3 x outside diameter of the cable. As a resultof the development of economical manufacturing processes, sheathed cables are find-ing more and more applicability as an essential part for the production of standard ther-mocouples, especially in the industrial measurement and control sector as well as forautomotive sensors.

Due to the metallic outer sheath, these thermocouples are essentially unaffected byfield induced electromagnetic interference (EMI), provided that they are grounded cor-rectly.

51

Insulation and Insulation Resistance

The achievable insulation resistance is a function of the purity of ceramic insulationmaterial. Aside from the standard material MgO with a purity of > 97 %, also MgO witha purity of 99.4 % and Al2O3 can be used. Since these oxides are highly hygroscopic,care must be exercised when handling the cable. After removing the sealing or cuttingthe cable, it has to be dried properly. Afterward the open ends have to be immediatelysealed against moisture entry. Storing for any length of time with open ends must beavoided.

Since the insulation material of the mineral insulated thermocouple cables andsheathed thermocouples has a low rest conductivity, the insulation resistance de-creases as the length of the cable or thermocouple increases. Therefore a lengthrelated resistance with the units Ω x m or MΩ x m is specified.

For lengths less than 1 m the insulation resistance is specified independent of thelength. Based on EN 61515 the insulation resistance must be tested with a voltage of75 ±25 V DC for outside diameters ≤ 1.5 mm and with 500 ±50 V DC for outside diam-eters >1.5 mm.

Tbl. 3-3: Minimum insulation resistance of mineral insulated thermocouple cables according toEN 61515

Tbl. 3-4: Minimum insulation resistance of sheathed thermocouples with insulated measurement spot locations according to EN 61515

Insertion depthat test temperature

min.m (ft.)

Test temperature

°C (°F)

Insulation resistancemin.

MΩ x m

Ambienttemperature 1 (3) 20 ±15 (68 ±27) 1000

Increased temperatureTypes J, K, N, E 0.5 (1.5) 500 ±15 (932 ±27) 5

Increased temperatureType T 0.5 (1.5) 300 ±15 (572 ±27) 500

Length of Thermo-couplem (ft.)

Insertion depthat test

temperaturem (inch)

Test temperature

°C (°F)

Insulation resistance

min.MΩ x m

Insulation resistance

min.MΩ

Ambienttemperature ≥ 1 (3) Total length

20 ±15(68 ±27) 1000 –

Ambienttemperature < 1 (3) Total length

20 ±15(68 ±27) – 1000

Increased temperatureTypes J, K, N, E All lengths

50 % of thetotal lengthmax. 0.3 (1)

500 ±15(932 ±27)

– 5

Increased temperatureType T All lengths

50 % of thetotal lengthmax. 0.3 (1)

500 ±15(932 ±27)

– 500

52

It should be noted when using sheathed thermocouples that the insulation resistanceof the insulating ceramic decreases appreciably with increasing temperatures. Whenlonger lengths of the sheath material are exposed to high temperatures, measurementerrors could result due to shunt currents or cross talk between adjacent measurementinstallations along the length of the cable.

Sheath Materials

Basically, mineral insulated thermocouple cables could be made of materials suffi-ciently ductile, preferred however, are those made entirely of austenitic stainless steel.

Nickel alloys are also useful for special applications. Though not all sheathmaterial/thermocouple combinations are possible, e. g., for high heat resistant sheathmaterials the required intermediate annealing temperatures required for processingmay, in part, be appreciably above the allowable temperature limits for the thermo-couple materials. The most common sheath materials are:

1.4541 (corresponds to AISI 321)Max. operating temperature: 800 °C (1472 °F).Application areas: Nuclear plants and reactor construction, chemical system engineer-ing, heat treating furnaces, heat exchangers, paper and textile industries, petrochemi-cal and petroleum industries, lubricant and soap industries.Material properties: Good intercrystalline corrosion resistance, also after welding.Good resistance against crude oil products, steam and combustion gases. Good oxi-dation resistance. Good welding properties for all standard welding processes, no sub-sequent heat treatment required after welding, good ductility.

1.4571 (corresponds to AISI 316 TI)Max. operating temperature: 800 °C (1472 °F)Application areas: Nuclear plants and reactor construction, chemical system engineer-ing, furnace manufacture, chemical and pharmaceutical industries.Material properties: Increased corrosion resistance to specific acids due to the additionof Molybdenum. Resistant against pitting, salt water and aggressive industrial influenc-es. Good welding properties for all standard welding processes, no subsequent heattreatment required after welding, good ductility.

53

1.4749 (corresponds to AISI 446)Max. operating temperature: 1150 °C (2102 °F)Application areas: Petrochemical industries, metallurgy, energy technologies and forrecuperators, heat treatment ovens, systems for controlling fluidized bed coatings,waste incineration plants.Material properties: Extremely good resistance against reducing atmospheres contain-ing Sulphur. Very good resistance against oxidation and air. Good resistance againstcorrosion by combustion products, Copper, Lead- and Tin melting. Good welding prop-erties for applications using arc or WlG welding. Preheating to 200...400 °C (392...752 °F) is recommended. Subsequent heat treatment is not required.

1.4841 (corresponds to AISI 314)Max. operating temperature: 1150 °C (2102 °F)Application areas: Steam boilers and blast furnaces, cement and tile ovens, glass man-ufacture, petroleum and petrochemical industries, furnace manufacture, power plants.Material properties: Exceptional corrosion resistance, even at high temperatures. Suit-able for Carbon and Sulphur containing atmospheres. Air oxidation resistance to1000 °C (1832 °F) (batch operation) or 1150 °C (2102 °F) (continuous operation). Verygood for higher alternating temperature changes. Long term continuous operation isnot recommended for temperature ranges from 425...850 °C (797...1562 °F). Goodwelding properties for applications using arc welding. Subsequent heat treatment is notrequired. Good ductility in the as received condition. After longer use some slight brit-tleness can be expected.

1.4845 (corresponds to AISI 310 S)Max. operating temperature: 1100 °C (2012 °F)Application areas: Steam boilers and blast furnaces, cement and tile ovens, glass man-ufacture, petroleum and petrochemical industries, furnace manufacture, power plants.Material properties: Good resistance against oxidation and sulfidization. Due to thehigh Chromium content resistant to oxidizing aqueous solutions as well as good resis-tance against Chlorine induced stress crack corrosion. Good resistance in Cyanidemelters and neutral fused salt at high temperatures. Not sensitive to “Green rot“. Read-ily weldable. It is recommended that heat be added during welding. When intercrystal-line corrosion may occur, solution heat treat after welding.

1.4876 (corresponds to Incolloy 800®)Max. operating temperature: 1100 °C (2012 °F) in airApplication areas: power plants, petroleum and petrochemical industries, furnace man-ufacture.Material properties: Due to the admix of Titanium and Aluminum the material hasespecially good heat resistance. Suitable for applications, where highest loading isrequired. Resistant to scale. Exceptionally stable where carburization and nitration canbe expected. Good welding properties for applications using arc or TlG welding. Sub-sequent heat treatment is not required.

54

2.4816 (corresponds to Inconel 600®)Max. operating temperature: 1100 °C (2012 °F)Application areas: Pressurized water reactors, nuclear power plants, furnace manufac-ture, plastic industry, heat tempering, paper and food industries, steam boilers, airplaneengines.Material properties: Good general corrosion resistance, resistant to stress crack corro-sion. Exceptional oxidation resistance. Not recommended for CO2 and Sulphur con-taining gases above 550 °C (1022 °F) and Sodium above 750 °C (1382 °F). Stable inair to 1100 °C (2012 °F). Good welding properties for all welding techniques. The ma-terial should be annealed before welding. Subsequent heat treatment is not required.Exceptional ductility even after long term use.

Platinum 10% RhodiumMax. operating temperature: 1300 °C (2372 °F)Application areas: Glass, electrochemical and catalytic technology, chemical industry,laboratory applications, melting, annealing and firing ovens.Material properties: High temperature resistance to 1300 °C (2372 °F) under oxidizingconditions. In the absence of Oxygen, Sulphur, Silicon, high heat resistance to 1200 °C(2192 °F). Especially resistant to halogens, acetic acid, NaOCI solutions etc. Embrittle-ment due to absorption of Silicon from sheath ceramics. Sulphur eutectic formationpossible above 1000 °C (1832 °F). Phosphorous sensitivity.

3.1.3 Thermocouple Wires and Compensating Cables

It is often necessary to locate the reference junction of the thermocouple at a great dis-tance from the measurement site due to safety concerns or constructional reasons.

In other instances the measurement circuit installation is fixed and the actual thermo-couple is designed as a measuring inset so that it can easily be exchanged. Also, forcost reasons, especially for precious metal thermocouples it is economical to use an-other, less costly material for the reference junction. In this case, an interconnection ca-ble is used between the actual thermocouple and the reference junction, which over arestricted temperature range has the same thermoelectrical properties as the corre-sponding thermocouple. These “connector links“ are the thermocouple and compen-sating cables. The application range for these cables is limited in most national and in-ternational standards to a temperature range of -25 °C (-13 °F) to 200 °C (392 °F), oris dependent on the temperature resistance of the insulation material used. The insu-lation material itself is to be selected so that the requirements at the “local site“, includ-ing chemical and heat resistance, moisture protection etc. are satisfied.

55

Concepts

Thermal cables are made of thermal wires or braid conductors, which have the samenominal composition as the corresponding thermocouple. Compensating cables aremade of substitute materials (other alloys than those for the thermocouple), but havingthe same thermoelectrical properties over a limited temperature range. Since theagreement of the thermal voltage of the particular thermocouple is based on the com-pensating pair and not on its individual wire, there may not be any temperature differ-ences at the transition locations between the legs of the thermocouple. Otherwise par-asitic thermal voltages will produce measurement errors.

The allowable deviation limits for the thermocouple or compensating cables limit theadditional deviations which may be added in the measurement circuit of such a cablein microvolts.

Thermocouple Wires and Compensating Cables according to EN 60584-3/DIN 43722

Since 1994 EN 60584-3 has been accepted by all the industrial countries worldwide.DIN 43722 is the minimally modified German version of IEC 584-3: 1989.

Short Designation:Thermocouple wires (original material) are identified by the letter X (X stands foreX-tension), which is added after the code letter for the thermocouple, for example: JX.Compensation cables (substitute material) are identified by the letter C (C stands forCompensating), which is added after the code letter for the thermocouple, for example:KC.Since for some thermocouples, additional substitute materials are used, they must beidentified by an additional letter for differentiation, for example: KCA and KCB.

Color Identification:The color for the negative conductor for all thermocouple types is white, the positiveconductor corresponds to specifications in the following table.

Tbl. 3-5: Color code for thermocouple wires and compensating cables according to DIN 43722

Type ofthermocouple

Color of positiveconductor and sheath

Color ofnegative conductor

S orange white

R orange white

B gray white

J black white

K green white

N pink white

T brown white

E violet white

56

The outer sheath, if present, has the same color code as the positive conductor. Anexception are the connection wires for Intrinsically Safe circuits, for which the colorcode is blue for all thermocouple types. If the thermocouple or compensating cableshave a plug connector, then it must be identified with the same color code as thepositive conductor or sheath. The entire connection plug is to colored, or alternatively,a color dot can be applied to its outer surface.

Deviation Limits:The allowable deviations listed in the table below (in microvolts) for thermocouple wiresand compensating cables for the allowable temperature ranges. The deviations inbrackets are the equivalent deviations expressed in (°C/°F) when the meter location ofthe entire measurement circuit (thermocouple with connected thermocouple wires orcompensating cable) is also at the same temperature.

Tbl. 3-6: Deviation limits for thermocouple wires and compensating cables classes according to DIN 43722

Type ofthermo-couple

Typeof

cable

Deviation limit Class Applicabletemperature

range

Temp.at the

measurementlocation

1 2

J JX ±85 μV(±1.5 °C/±2.7°F)

±140 μV (±2.5 °C /±4.5 °F)

-25...200 °C(-13...392 °F)

500 °C (932 °F)

T TX ±30 μV(±1.5 °C/±2.7 °F)

±60 μV (±1.0 °C /±1.8 °F)

-25...100 °C(-13...212 °F)

300 °C (572 °F)

E EX ±120 μV(±1.5 °C/±2.7 °F)

±200 μV (±2.5 °C /±4.5 °F)

-25...200 °C(-13...392 °F)

500 °C (932 °F)

K KX ±60 μV(±1.5 °C/±2.7 °F)

±100 μV (±2.5 °C /±4.5 °F)

-25...200 °C(-13...392 °F)

900 °C (1652 °F)

N NX ±60 μV(±1.5 °C/±2.7 °F)

±100 μV (±2.5 °C /±4.5 °F)

-25...200 °C(-13...392 °F)

900 °C (1652 °F)

K KCA – ±100 μV (±2.5 °C /±4.5 °F)

0...150 °C(32...302 °F)

900 °C (1652 °F)

K KCB – ±100 μV (±2.5 °C /±4.5 °F)

0...100 °C(32...212 °F)

900 °C (1652 °F)

N NC – ±100 μV (±2.5 °C /±4.5 °F)

0...150 °C(32...302 °F)

900 °C (1652 °F)

R RCA – ±30 μV (±2.5 °C /±4.5 °F)

0...150 °C(32...302 °F)

1000 °C (1832 °F)

R RCB – ±60 μV (±5.0 °C /±9 °F)

0...200 °C (32...392 °F)

1000 °C (1832 °F)

S SCA – ±30 μV (±2.5 °C /±4.5 °F)

0...100 °C (32...212 °F)

1000 °C (1832 °F)

S SCB – ±60 μV (±5.0 °C /±9 °F)

0...200 °C(32...392 °F)

1000 °C (1832 °F)

B BC – ±40 μV (±3.5 °C /±6.3 °F)

0...100 °C (32...212 °F)

1400 °C (2552 °F)

57

3.1.4 Older National Standards

For many of the cables described in older standards, national or international basic val-ues do not exist, yet these products are installed in many systems worldwide. For newinstallations and when updating existing systems, only the thermocouple and compen-sating cables according to IEC 584-3: 1989 or DIN 43722 described in the previoussections should be used. The best known still being used, but no longer being updatedin the national standards are:

Compensating Cables according to DIN 43713 / DIN 43714

Short Designation:In DIN 43713 / DIN 43714 a differentiation was not made between compensating andthermocouple wires. All cables are designated as compensating cables and identifiedby the abbreviation AGL followed by the text “DIN 43714“ and the nominal compositionof the corresponding thermocouple, for example: AGL DIN 43714 Fe-CuNi.

Color Code:The color code for the insulation of positive conductor for all thermocouple types is red,for the negative conductor the color codes are listed in the table below:

Tbl. 3-7: Color codes for compensating cables according to DIN 43714

The outer sheath, if present, has the same color code as that listed in the above table.An exception are those cables for Intrinsically Safe circuits, for which the color code isalways light blue for all thermocouple types which also includes a stripe or tracer threadwith the color for the particular negative conductor.

Type of thermocouple Color of positive conductor

Color of negative conductorand sheath

S red white

R red white

L red dark blue

K red green

U red brown

58

Deviation Limits:The allowable deviations (in °C / °F) are listed in the table below for the compensatingcables with the allowable operating temperature ranges.

Tbl. 3-8: Deviation limits according to DIN 43710 for compensating cables acc. to DIN 43713

Thermocouples and Compensating Cables according to ANSI-MC96.1 (USA)

Short Designation:In ANSI-MC96.1 a differentiation was not made between compensating and thermo-couple cables. All cables were identified the same by the code letter X, added after thecode letter for the thermocouple, for example: EX.

Color Code:The color code for the insulation of the negative conductor for all thermocouple typesis red, for the positive conductor the color codes are listed in the table below:

Tbl. 3-9: Color codes for thermocouple wires and compensating cables according to ANSI-MC96.1

The outer sheath, if present, has the same color code as those listed in the above table.

Type of thermocouple

Type of cable Allowabledeviation limit

Operatingtemperature range

Cu-CuNi (U) Cu-CuNi ± 3.0 °C (± 5.4 °F) 0...200 °C (32...392 °F)

Fe-CuNi (L) Fe-CuNi ± 3.0 °C (± 5.4 °F) 0...200 °C (32...392 °F)

NiCr-Ni (K) NiCr-Ni ± 3.0 °C (± 5.4 °F) 0...200 °C (32...392 °F)

NiCr-Ni (K) SoNiCr-SoNi1 ± 3.0 °C (± 5.4 °F) 0...200 °C (32...392 °F)

NiCr-Ni (K) SoNiCr-SoNi2 ± 3.0 °C (± 5.4 °F) 0...100 °C (32...212 °F)

Pt10%Rh-Pt (S) SoPtRh1-SoPt1 ± 3.0 °C (± 5.4 °F) 0...200 °C (32...392 °F)

Pt10%Rh-Pt (S) SoPtRh2-SoPt2 ± 3.0 °C (± 5.4 °F) 0...100 °C (32...212 °F)

Pt13%Rh-Pt (R) SoPtRh1-SoPt1 ± 3.0 °C (± 5.4 °F) 0...200 °C (32...392 °F)

Pt13%Rh-Pt (R) SoPtRh2-SoPt2 ± 3.0 °C (± 5.4 °F) 0...100 °C (32...212 °F)

Type ofthermocouple

Color ofsheath

Color ofpositive conductor

Color ofnegative conductor

S green black red

R green black red

B gray gray red

J black white red

K yellow yellow red

T blue blue red

E violet violet red

59

Deviation Limits:The allowable deviations listed in the table below (in microvolts and °C / °F) for thermo-couple and compensating cables for the allowable operating temperature ranges.

Tbl. 3-10: Deviation limits for thermocouple wires and compensating cable classes according to ANSI-MC96.1

Thermocouple Wires and Compensating Cables according to NF C 42-324 (France)

Short Designation:In NF C 42-324 a differentiation is made between thermocouple wires and compensat-ing cables (Câble de Extension et Câble de Compensation), but a compensating cablecan also be a thermocouple, which may differ from the thermocouple because its com-position has a lower thermoelectric quality (tolerance). That means that the compen-sating cables may or may not be identical to the thermocouple.The thermocouple wires are identified by the code letter X added after the code letterfor the thermocouple, for example: JX.Compensating cables are identified by the code letter C added after the code letter forthe thermocouple, for example: KC.

Color Code:The color code for the insulation of the positive conductor for all thermocouple types isyellow, for the negative conductor the color codes are listed in the table below.The outer sheath, if present, is identified by the color codes listed in the table below.

Type ofthermocouple

Type ofcable

Deviation limit Classes Operatingtemperature range

special standard

E EX – ±1.7 °C (±3.06 °F) 0...200 °C (32...392 °F)

J JX ±1.1 °C (±1.98 °F) ±2.2 °C (±3.96 °F) 0...200 °C (32...392 °F)

K KX – ±2.2 °C (±3.96 °F) 0...200 °C (32...392 °F)

T TX ±0.5 °C (±0.9 °F) ±1.0 °C (±1.98 °F) 0...100 °C (32...212 °F)

R SX – ± 57 μV 0...200 °C (32...392 °F)

R SX – ± 57 μV 0...200 °C (32...392 °F)

S SX – ± 57 μV 0...200 °C (32...392 °F)

S SX – ± 57 μV 0...200 °C (32...392 °F)

B BX – + 0 μV/-33 μV 0...100 °C (32...212 °F)

60

Tbl. 3-11: Color codes for thermocouple wires and compensating cables according to NF C 42-324

Deviation Limits:The allowable deviations listed in the table below in °C (°F) for thermocouple and com-pensating cable for the allowable operating temperature ranges.

Tbl. 3-12: Deviation limits for thermocouple wires according to NF C 42-324

Tbl. 3-13: Deviation limits for compensating cables according to NF C 42-324

Type ofthermocouple

Thermo-couple wire

Compensatingcable

Color of positive conductor

Color of negativeconductor and sheath

S – SC yellow green

R – SC yellow green

B – BC yellow gray

J JX JC yellow black

K KX KC yellow violet

K – VC yellow brown

K – WC yellow white

T TX TC yellow blue

E EX EC yellow orange

Temperature range TX JX EX KX

-25...250 °C (-13...482 °F)

±0.5 °C (±0.9 °F)

±1.5 °C (±2.7 °F)

±1.5 °C (±2.7 °F)

±1.5 °C (±2.7 °F)

Temperaturerange

TC JC EC KC VC WC SC BC

-25...100 °C(-13...212 °F)

±1.0 °C (±1.8 °F)

±3.0 °C (±5.4 °F)

±3.0 °C (±5.4 °F)

±3.0 °C (±5.4 °F)

±3.0 °C (±5.4 °F)

±3.0 °C (±5.4 °F)

±7.0 °C (±12.6 °F)

±4.0 °C (±7.2 °F)

100...200 °C(212...392 °F)

– ±3.0 °C (±5.4 °F)

±3.0 °C (±5.4 °F)

±3.0 °C (±5.4 °F)

– ±3.0 °C (±5.4 °F)

±7.0 °C (±12.6 °F)

±4.0 °C (±7.2 °F)

200...250 °C(392...482 °F)

– ±3.0 °C (±5.4 °F)

±3.0 °C (±5.4 °F)

– – – – –

61

3.1.5 Measurement Resistors

When making temperature measurements using measurement resistors the electricalresistance of a sensor subjected to the temperature is the variable utilized.

The temperature dependence of the electrical resistance of metals, semiconductorsand ceramics is used as the measurement value. The materials are divided into twogroups based on the slope of the curve: NTC- and PTC-sensors.

PTC-sensors are materials whose resistance increases as the temperature increases(positive temperature coefficient) or “cold wire“. Included are the metallic conductorswhich are used in the manufacture of the measurement resistors described below.

NTC-sensors (negative temperature-coefficient) or “hot wire“ are usually semiconduc-tor or ceramic sensors, which are usually installed for specific requirements and tem-peratures.

Materials for Measurement Resistors

The are a number of requirements which must be met for the materials used as tem-perature sensors in order that good and reproducible measurements can be made.

• Large temperature coefficient,• Minimal sensitivity to environmental effects (corrosion, chemical attack),• Wide measurement range,• Interchangeability,• Long term stability,• Easily processed.

For industrial temperature measurement technology, Platinum is the most used mate-rial for the resistors followed by Nickel.

It is for this reason that both of these materials will be described in detail in the follow-ing.

The Platinum measurement resistors with a nominal value of 100 Ω (Pt100) has be-come established in recent years as the industrial standard.

62

Nominal ValuesThe resistors are identified by the resistance at 0 °C (32 °F) (nominal value). Ni100 andPt100 the most common types have a resistance of 100 Ω at 0 °C (32 °F), Pt500 orPt1000 have 500 or 1000 Ω respectively at 0 °C (32 °F).

Fig. 3-3: Resistance Rt relationship to temperature for Platinum measurement resistorswith different nominal values

Temperature Coefficient (Tc)More precisely stated, the temperature coefficient of the electrical resistance. It definesthe change in electrical resistance between two temperatures, usually between 0 °Cand 100 °C (32 °F and 212 °F) with the units:

which is therefore dimensionless

For smaller temperature ranges a linear relationship can be assumed:

with

-200 -100 0 100 200 300 400

Pt500

Pt100

Pt1000

Pt2000

500 600 700 800 9000

500

1000

1500

2000

2500

R[

]t

Ω

Pt10Pt20

Temperature [°C]

Ω

Ω K⋅---------- 1

K---

( )[ ]R R t tt = + −0 01 α

α =−

⋅ °R R100 0

R 100 C0

63

Where:

t: Temperature in °Ct0: Reference temperature ( e.g. 0°)Rt: Resistance at temperature t in ΩR0:Nominal resistance at 0 °C in Ωα: Average temperature coefficient between 0 °C and 100 °C (32 °F and 212 °F) in K-1

Platinum MaterialIts advantages include very pure producability, high chemical resistance, easy manu-facturability, good reproducibility of the electrical properties and a wide applicationrange between -250 °C and 850 °C (-418 °F and 1562 °F).

The temperature coefficient of spectral pure Platinum is 0.003925 K-1 and is differentthan the value required for Pt-measurement resistors. The Platinum used for industrialPlatinum temperature resistors is selectively produced.

Specified in EN 60751 for the Platinum sensors, among others, are the temperaturerelationship to the resistance, the nominal value, the allowable deviation limits and thetemperature range.

Measurement Characteristics of PlatinumSimplified:It the range from 0...100 °C (32...212 °F) Platinum has a temperature coefficient of0.00385 K-1, i. e. a Pt100 measurement resistor at 0 °C (32 °F) has a resistance of100 Ω and at 100 °C (212 °F) 138.5 Ω.

Expanded:By definition the basic values are divided into two different temperature ranges:

For -200...0 °C (-328...32 °F) a third order polynomial applies

For the range from 0...850 °C (32...1562 °F) a second order polynomial applies

The coefficients according to EN 60751 are:

A = 3.9083 · 10-3 K-1

B = 5.775 · 10-7 K-2

C = 4.183 · 10-12 K-4

( )[ ]R R A t B t C t C tt = + ⋅ + ⋅ + ⋅ − ° ⋅02 31 100

[ ]R R A t B tt = + ⋅ + ⋅021

64

For temperatures above 0 °C (32 °F) the relationship between the temperature an theresistance can be described by the equation:

in which the resistance values for the basic value tables in EN 60751 are listed for tem-perature in steps of 1 K.

For the sensitivity, i.e. the resistance change according to K, for temperatures <0 °C(32 °F):

For temperatures above 0 °C (32 °F) the following applies:

Fig. 3-4: Sensitivity dR/dT for Ni100 and Platinum measurement resistors with dIfferent nominal values

t AB

AB

R RR B

t= −⋅

−⋅

⎛⎝⎜

⎞⎠⎟

+−

⋅2 2

20

0

2

( )ΔΔRt

R A B t C t C t= + ⋅ ⋅ − ° ⋅ + ⋅ ⋅02 32 300 4

( )ΔΔRt

R A B t= + ⋅ ⋅0 2

-200 -100 0 100 200 300 400 500 600 700 800 9000

1

2

3

4

5

6

7

8

9

Pt500

Pt100

Pt1000

Pt2000

Ni100

Sen

sitiv

ity [

/ K]

Ω

Temperature [°C]

65

Tolerance Classes for Platinum

According to EN 60751 the Platinum resistance thermometers the deviation limits Δtare divided into two tolerance classes:

Class A:

Class B:

Tbl. 3-14: Deviation limit according to EN 60751 and expanded deviation limit

Fig. 3-5: Deviation limit for Platinum resistance thermometers in °C

Tolerancedesignation

Temperaturerange

Tolerance in K Deviation limit at 0 °C (32 °F)

resistance

Tempera-ture

R0 =100 Ω

R0 =500 Ω

R0 =1000 Ω

Class A -200...650 °C (-328...1202 °F)

±(0.15 K+0.002 · [t]) ±0.15 K ±0.06 Ω ±0.29 Ω ±0.59 Ω

Class B -200...850 °C (-328...1562 °F)

±(0.30 K+0.005 · [t]) ±0.30 K ±0.12 Ω ±0.59 Ω ±1.17 Ω

Deviation limit at 100 °C (212 °F)

Class A ±0.35 K

Class B ±0.80 K

( )t002.0C15.0t ⋅+°±=Δ

( )t005.0C30.0t ⋅+°±=Δ

-200 -100 0 100 200 300 400 500 600 700 800 9000

1

2

3

4

5

6

Class B

Class A

Dev

iatio

n Li

mit

[°C

]

Temperature [°C]

66

Nickel MaterialIt is appreciably less expensive than Platinum. Its temperature coefficient is almosttwice as high, but it has a decidedly poorer chemical resistance. The measurementrange is limited to only -60...250 °C (-76...482 °F) and the allowable deviation limits aregreater than for Platinum. The Nickel measurement resistors are standardized inDIN 43760.

Measurement Characteristics of NickelSimplified:In the range from 0...100 °C (32...212 °F) Nickel has a temperature coefficient of0.00618 K-1 i.e. the measurement resistor Ni100 at 0 °C (32 °F) has a resistance of100 Ω and at 100 °C (212 °F) 161.85 Ω.

Expanded:The relationship between the resistance and temperature for Nickel in a temperaturerange -60...250 °C (-76...482 °F) is:

whereA = 0.5485 · 10-2 K-1

B = 0.665 · 10-5 K-2

C = 2.805 · 10-11 K-4

D = -2 · 10-17 K-6

According to DIN 43 760 the nominal value is 100.00 Ω (therefore: Ni100). Additionally,resistors with R0 = 10 Ω, 1000 Ω or 5000 Ω are also manufactured.

Fig. 3-6: Relationship of the resistance Rt to the temperature for Ni100

( )R R A t B t C t D tt = + ⋅ + ⋅ + ⋅ + ⋅04 61

-100 -50 0 50 100 150 200

Ni100

2500

50

100

150

200

250

300

R[

]t

Ω

Temperature [°C]

67

In the standard the maximum allowable deviation limits Δt for Nickel resistors aredefined by:

for 0...250 °C (32...482 °F)

for -60...0 °C (-76...32 °F)

Fig. 3-7: Maximum deviation limit in °C for Ni100

Nickel resistors are often found in the heating, ventilating and air conditioning sectors.

( )t007.0C4.0t ⋅+°±=Δ

( )t028.0C4.0t ⋅+°±=Δ

-100 -50 0 50 100 150 200

Ni100

250

Dev

iatio

n Li

mit

[°C

]

Temperature [°C]

0.0

0.5

1.0

1.5

2.0

2.5

68

Measurement Resistor DesignsOnly Platinum measurement resistors will be discussed in the following. They aredivided into two categories, thin film and wire-wounded resistors. Ceramic, glass orplastic are used as the basic carrier materials.

Thin Film ResistorsThe measurement coil is made of Platinum wires with diameters between 10 µm and50 µm.

Wire-wounded ResistorsA precisely adjusted Platinum coil with connections leads is located in a ceramic doublecapillary. Glass frit powder is packed into the holes of the capillaries. Both ends of theceramic body are sealed with glass frit. After the glass frit is melted the Platinum coiland the connection leads are fixed in place.

In another design, the Platinum coil is not placed in the holes of a ceramic cylinder, butis placed in a slot in the ceramic body. The outside dimensions are between 0.9 mmand 4.9 mm (0.035” and 0.20”) with lengths between 7 mm and 32 mm (0.28” and1.25”).Typical applications: demanding measurement and control requirements in the processindustries and laboratory applications.

Fig. 3-8: Ceramic wire-wounded resistor

Ceramic double capillary

Platinum coil

Drilling

Connection wires

69

Glass Measurement ResistorsIn this design the measurement coil is wound in a bifilar configuration on a glass rodand melted into the glass and the connection wires attached. After it is adjusted, a thinwall glass tube is placed over measurement coil and both elements fused together. Thegeometric dimensions of the diameter are between 0.9...5.0 mm (0.035”...0.20”) withlengths varying between 7...60 mm (0.275”...2.35”).Typical applications: chemical system engineering.

Fig. 3-9: Glass measurement resistor

Slot Resistance ThermometerThe Platinum measurement winding is placed stress free in a slot in a plastic band andconnection leads attached stress free. The insulation body is surrounded, including thecable exit by shrinkable tubing. The geometric dimensions for the width can varybetween 8 mm (0.31”) and 12 mm (0.5”), lengths between 63 mm and 250 mm (2.5”and 10”). The thickness is 2 mm (0.08”).Typical applications: temperature measurements in the winding of electrical machinesand on curved surfaces

Foil Temperature SensorsThe Platinum measurement winding is embedded between two Polyimide foils and theconnection leads attached. The thickness is 0.17 mm (0.007”).Typical applications: Measurements on pipes

Metal Film ResistorsIn place of measurement wires thin platinum layers are used as the measurement ele-ment. The layers are applied to ceramic carriers. There are a number of methods fordepositing thin layers, e.g. vacuum vapor deposition, sputtering or sintering a thickPlatinum paste.

Glass rod

Glass tube

Platinum coil

Connection wires

70

Platinum Thick Film Measurement ResistorsIn this design a Platinum paste is applied to a ceramic substrate using a silk screenprocess and fused. Then the resistance is trimmed to the nominal value, a glass pro-tection layer and connection leads attached and then stress relieved. The thickness ofthe Platinum layer is between 10 µm and 15 µm.

Platinum Thin Film Measurement ResistorsFlat typesA Platinum layer 1 µm to 2 µm thick is vapor deposited or sputtered onto a ceramic sub-strate. The desired geometric shape is formed by cutting with a laser or structuredusing photolithography. The Platinum traces are between 7 µm and 30 µm wide. Alaser trimmer is used to adjust the resistance to the nominal value. For protectionagainst mechanical damage (scratches) a 10 µm thick glass ceramic insulation isapplied using a silk screen process and fused. After the connection leads are attachedby welding the connection spots are covered by a fused glass coating applied in astress free manner. The geometric dimensions of the flat types vary from 1.4 mm x1.6 mm (0.05” x 0.06”) to 2 mm x 10 mm (0.08” x 0.40”), the substrate thickness from0.25 mm to 0.65 mm (0.010” to 0.026”) Typical applications: all application ranges, surface temperature measurements

Fig. 3-10: Thin film measurement resistor

71

Thin Film Tubular TypesIn addition to the flat type thin film measurement resistors a round form is available. Inthis design the flat measurement resistors are inserted axially in cylindrical ceramictubes. The ends of the tube are sealed by melting glass frit across them which alsoseals and positions the ends of the measurement resistor together with the connectionleads. The end result is a round shape. The ceramic also provides protection for thethin film measurement resistors. The outside dimensions of the diameter are 2 mm to4.8 mm (0.080” to 0.20”) and the lengths are 5 mm to 14 mm (0.20” to 0.55”) .Typical applications: process engineering

Fig. 3-11: Thin film tube type (Installation principle)

72

Thin Film Platinum Measurement Resistors with Solder Connection PadsIn this design the connection pads are coated with a solderable metallization. Thedesign has adjacent connection pads with solder depots suitable for direct connectionof insulated cables. Measurement resistors with connection pads at opposite ends arecalled “Surface Mounted Devices“, SMD, which can be directly soldered to circuitboards or hybrid circuits.Typical application: On circuit boards.

Fig. 3-12: Thin film and metal wire measurement resistor designs

Selection Criteria and Application Limits

The application limits of the sensors are restricted by numerous parameters. The mostimportant, without question, is the temperature. Exactly defined temperature limits aredifficult to specify. In addition to the temperature, they are also influenced by themedium to be measured, mechanical factors (different expansion coefficients) and theaccuracy and reliability requirements.

It is not possible to specify a universally applicable conclusion as to which resistancethermometer design represents the best solution. The best construction solution is in ahigh way depending on the application conditions. Selection criteria are:

– Temperature rangeIt is rare, that for a specific application the entire range specified in the standards isrequired. For high temperatures (greater than 600 °C (1112 °F)) sensors with specialconnection leads (NiCr) are used. For applications with temperature shocks wire-wounded types are preferred.

73

– Required accuracy and long term stabilityThe accuracies are derived from the tolerance classes of from the actual individualmeasurement values; for long term stability, specific ambient conditions must beconsidered. Particularly, for industrial conditions above 400 °C (752 °F) cautionshould be exercised, carefully weigh versus thermocouples.

– Sensitivity and self heatingSensitivity is defined by the resistance changes according to K and for the Pt100 itis 0.385 Ω/K and for the Pt1000 it is 3.85 Ω/K. Since the measurement signal isderived directly from measured current, the resistance to the current (voltage drop atthe measurement resistor is U = RxI) in the circuit causes self heating in themeasurement resistor, which increases as the square of the current (P = I2 xR). Foraccurate measurements the self heating must be kept small and therefore the cur-rent has to be limited.

It can be stated simply that for industrial applications, using the measurement currentsof modern transmitters, the following needs not to be considered.

Expanded:

whereIallow : Allowable measurement currentEK: Self heating coefficient in W/KΔTallow: Allowable temperature increaseR0: Nominal resistanceα: Temperature coefficient

Typical values for the voltage sensitivity for an allowable temperature increase of 0.1 Kfor Pt100 film type measurement resistors are approx. 0.1 mV/K and for a Pt1000, ap-prox. 0.4 mV/K for measurements in flowing water.

In air, the values for a Pt100 are approx. 0.03 mV/K to 0.09 mV/K. The maximum allow-able measurement current for flowing water for a Pt100 is approx. 6 to10 mA and for aPt1000 approx. 3 mA. In air for a Pt100 it is approx. 2 mA and for a Pt1000 approx.1 mA. Wire resistors have somewhat lower self heating coefficient than the film resistortypes and therefore can be operated with higher allowable measurement currents (forPt100 Iallow. is approx. 4 mA to 14 mA in water and 2 mA to 3 mA in air). Their nominalvalue is however limited to 100 mW.

2

0

allowallow R

TEKI

Δ⋅=

2allow

20 EKTR

dTdU

⋅⋅α⋅=

74

– Response timeThe response time of the bare resistors is usually of little concern because thedesign of the thermometer into which they are installed is the dominant factor indetermining the response time. The following values, however, are of importance inlaboratory applications.

The small geometric dimensions of the film type measurement resistors and theirassociated minimal heat capacity results in short response times, at T0.5 approx.0.1 s in water and approx. 3 s to 6 s in air. For wire type resistors the response timeT0.5 is between 0.2 s and 0.5 s in water and between 4 s and 25 s in air.

– Geometric dimensions and connection wire resistancesThe assigned basic values and their allowable deviation limits apply to the measure-ment resistors including the connection wire resistances (generally 10 mm...30 mm(0.4”...1.2”) long) or for longer connection wires up to a defined sensor point. Alladditional connection wires and junction resistances must be considered or compen-sated using special circuits.

75

3.2 Industrial Temperature Sensor Design

3.2.1 Design

Temperature sensor (thermocouples or resistance thermometers) designs can betraced back to three basic versions:

– Sheathed temperature sensors– Temperature sensors with exchangeable measuring insets– Temperature sensors for high temperatures (straight thermocouples)

Sheathed Temperature SensorsThey consist of wires embedded in an insulating powder inside a metal tube. At oneend the measuring element is capped and the other end contains a connection ele-ment, which can be a cable, plug or connection box.

During the manufacturing process for mineral insulated cables, the initially large diam-eter is reduced by stretching which compresses the insulating powder in such a mannerthat a flexible, vibration tight unit results.

Tbl. 3-15: Construction and dimensions of mineral insulated cables with 2 inner conductors

Outside Ø of the cable (D)nominal

± deviation limits

mm / inch

Minimum wall thickness

(S)

mm / inch

Minimum Øof the internal

conductor (C)

mm / inch

Minimuminsulation

thickness (I)

mm / inch

D = Outside diameterC = Conductor diameterS = Wall thicknessI = Insulation thickness

0.5 ± 0.025/0.020 ± 0.0011.0 ± 0.025/0.040 ± 0.0011.5 ± 0.025/0.060 ± 0.0011.6 ± 0.025/0.063 ± 0.0012.0 ± 0.025/0.080 ± 0.001

3.0 ± 0.030/0.118 ± 0.0013.2 ± 0.030/0.125 ± 0.0014.0 ± 0.045/0.157 ± 0.0024.5 ± 0.045/0.177 ± 0.0024.8 ± 0.045/0.187 ± 0.002

6.0 ± 0.060/0.236 ± 0.00256.4 ± 0.060/0.252 ± 0.00258.0 ± 0.080/0.315 ± 0.0032

10.0 ± 0.100/0.394 ± 0.0039

0.05/0.00200.10/0.00400.15/0.00600.16/0.00630.20/0.0080

0.30/0.01180.32/0.01250.40/0.01570.45/0.01770.48/0.0187

0.60/0.02360.64/0.02520.80/0.03151.00/0.0395

0.08/0.00310.15/0.00600.23/0.00910.24/0.00940.30/0.0118

0.45/0.01770.48/0.01870.60/0.02360.68/0.02680.72/0.0283

0.90/0.03540.96/0.03781.20/0.04721.50/0.0590

0.04/0.00160.08/0.00320.12/0.00470.13/0.00510.16/0.0063

0.24/0.00950.26/0.01020.32/0.01250.36/0.01420.38/0.0150

0.48/0.01870.51/0.02000.64/0.02520.80/0.0315

76

The sheathed temperature sensors are used, e.g., where the measurement site is dif-ficult to access.

Applications:Bearing temperature measurements, hot gas ducts, open tanks, laboratories, teststands, etc.

Fig. 3-13: Sheathed temperature sensor design for direct contact with the medium

77

Temperature Sensors with Exchangeable Measuring InsetThe measurement inset is constructed in a manner similar to the sheathed temperaturesensors. The connections are usually made using screw terminals on a ceramic socket.To protect this unit from process conditions and to facilitate replacing the unit withoutshutting down the process, the unit is built into a protection fitting. It consists of a ther-mowell with process connections (e.g. flanged, threaded) and a connection head, withprovisions for installing an appropriate cable connector. These components are definedin the standards:

DIN 43729 for connection heads,DIN 43772 for thermowells.

Fig. 3-14: Standardized thermowell examples: form 4 for hot steam pipelinesNAMUR thermowells for short response times

The entire sets of design types are defined in the standards:

DIN 43770, DIN 43771 for temperature sensors with exchangeable measuring insetsand DIN 43733 for straight thermocouples.

L

U

C

min 30

Ø 7

Ø 2

4 h7

Ø 1

2.5

4

Form 4 (D1, D4)

Ø D

Ø E

S50Ø 6

.1

Welded flange

78

Manufacturers and users have developed additional designs, based on the standard-ized ones, in order to accommodate varying operating and installation requirements.

Fig. 3-15: Additionally developed connection head examples;Type BUZH, BUKH for transmitter installed in the coverType AGL Flameproof Enclosure / Explosionproof

Often direct contact of the measuring sensor with the medium is not possible. In orderto increase the life of the inset when oxidation and corrosion effects are present, or tofacilitate a fast exchange without interrupting the process, thermowells are utilized.

For higher pressures, thermowells are made of drilled solid materials and processedon the outside. They have the advantage that their dimensions, shape and wall thick-ness can be optimally matched to the requirements (pressure, flow, etc.). Thermowellsmanufactured using these designs are usually more expensive than those made of tub-ing and pipes. For this reason the thermowells made from solid materials are only usedfor medium contacting temperature sensor area. Outside of the medium contact area,they can be extended using extension tubes if required.

For processes with lower loads, economical thermowells are used manufactured fromtubing material with a welded plug at the outer end.

Tbl. 3-16: Recommended installation lengths (standard values for stationary media)

Medium Minimum installation length

Gas 15...20 times thermowell diameterat the tip

Liquid 5...10 times thermowell diameterat the tip

Solid 3...5 times thermowell diameterat the tip

Type BUKH Type BUZH Type AGL

M24 x 1.5M20 x 1.5

M24 x 1.5

M20 x 1.5

79

The installation length includes the length contained in the pipe couplings. In addition,listed in the following are minimum length recommendations for the most common ther-mowells:

Tbl. 3-17: Recommended installation lengths for standard thermowell diameters

Fig. 3-16: Completely assembled temperature sensor with thermowell and extension tube

Thermowell diameter

9 mm0.357¨

11/12 mm0.433¨/0.472¨

14/15 mm0.551¨/0.590¨

22 mm0.866¨

25 mm0.984¨

Medium Minimum installation length

Gas 180 mm7.09¨

250 mm 9.84¨

300 mm11.81¨

450 mm17.72¨

500 mm19.69¨

Liquid 80 mm 3.15¨

110 mm4.33¨

160 mm6.30¨

250 mm9.84¨

300 mm11.81¨

Process connection

Sensor head(option with transmitter)

Measuring inset

Thermowell

Extension tube

80

Temperature Sensors for High Temperatures (Straight Thermocouples)

These are also designed with exchangeable measuring insets. Since these applica-tions are predominantly in combustion processes (temperatures to 1800 °C (3272 °F),these sensors incorporate some special design features.

Measuring inset: Thermocouple wires with large cross sectionsin a ceramic insulating rod

Thermowell: Made of heat resistant metals or ceramics.

Process connections: Since these applications are predominantly pressure free, basic connections (oval flange, threaded bushings) with packing glands can be used.

Fig. 3-17: Example: Temperature sensor design “Straight Thermocouple“

3.2.2 Installation Requirements

In industry there are a multitude of applications requiring temperature measurement. Inmany instances a standardized temperature sensor cannot be used. Special designsare required in order to optimize the measurement, e.g. measuring sensors with ex-tremely short sensor lengths or thermowells with minimum mass.

Heat Transfer

Temperature sensors must always be in good contact with the medium, so that a fasttemperature equilibrium condition can be achieved. Thermal measuring errors can beminimized using appropriate measures.

NH

K

M20 x 1.5

Ø D

S

D 15 16 24 26H 22 22 32 32

Connection head

DesignST P-AK

DesignST P-AKK

Thermocouplewith ceramicinsulation

Ceramic thermowell

Ceramic inner tube

Metal extension

tube

Process connection

81

With increasing flow velocity the heat transfer increases and installation lengths can bereduced. This is particularly apparent by the D-Sleeves defined in standard DIN 43772for use in hot steam pipelines. They are only installed to the tapered end and thereforehave an appreciably shorter installation length than the previously listed rules of thumb(see Tbl. 3-17 Recommended installation lengths):

Fig. 3-18: Temperature sensor in a hot steam pipeline at high flowrate

82

Installation Positions

If the designed installation length required for the installation is not available, thendesign changes to the sensor or to the installation arrangement may be required toassure more advantageous conditions:

• A tapered thermowell can reduce the required installation length by approx. 30 %.

• In pipelines with smaller diameters (DN 10...DN 20 (3/8”...3/4”)) the thermowell can be made an integral part of the connection adapter.

Fig. 3-19: Shorter installation lengths using reduced thermowell tips or exposedmeasuring inset

Fig. 3-20: Temperature sensor installation in small diameter pipelines

83

At the installation site, selection of the connection adaptor orientation for the sensormay also be used to achieve the required length:

• By lengthening the connection adaptor for the sensor (see Fig. 3-20),• by increasing the diameter of the pipeline,• by installing at an angle,• by installing in an elbow (this installation method is preferred because it reduces

the pipeline cross section the least and imposes the least stress on the thermo-well) see Fig. 3-21.

Fig. 3-21: Installation orientations in a pipeline

Installations without Thermowells

Using a directly installed temperature sensor without a thermowell can improve theresponse time and with the smaller diameter the installation length can be made veryshort (possibly:1.5; 2; 3; 6 mm (0.060“; 0.080“; 0.125“; 0.250“)). Thermocouples, incomparison to resistance thermometers measure at point locations, allowing very shortinstallation lengths (see Tbl. 3-18).

Tbl. 3-18: Recommended installation lengths for direct immersion (without thermowell) of the temperature sensors

Diameter

1.5 mm (0.060“) 3 mm (0.125“) 6 mm (0.250“)

Medium Minimum installation length

Gas 30 mm (1.18“) 60 mm (2.37“) 100 mm (4.00“)

Liquid 8 mm (0.312“) 30 mm (1.18“) 60 mm (2.37“)

Solid 5 mm (0.200“) 20 mm (0.750“) 30 mm (1.18“)

For resistance thermometers the temperature sensitive length of the measurementresistors, type dependent, is approx. 7...30 mm (0.28“...1.18“) long and must beadded to the values in the table.

84

3.2.3 Process Connections Types

Installations in pipelines are predominantly made using threaded, flanged or weldedconnections. The selected installation type determines the pressure rating, since thepressure existing in the process pipeline acts on the cross section of the connectionfitting.

Threaded Connections

Cylindrical threads are sealed using gaskets installed in the seal area. Based on thetemperature at the seal and the aggressiveness of the medium, gaskets made of Flu-orocarbon, Copper or stainless steel can be used. Because of the different elasticitiesand because the process pressure could cause the gaskets to lift from the seal surface,pressures which can be sealed are relatively low (max. 100 bar (1,450.38 psi)).

Tapered threads seals are achieved by the sealing action of the thread design withoutrequiring additional gaskets or the use of teflon tape. Since the seal exists along theentire length of the threads, the process pressures which can be sealed are higher.Dependent on the manufacturing process for the threads in the threaded bush-ings or nipples and the strength of the material, pressures of 300...400 bar(4,351.13...5,801.51 psi) can be sealed.

Flanged Connections

For flanged connections the pressure rating of the flange determines the maximumpressure. Pressure ratings up to 160 bar (2,320.60 psi) are available. At the lower pres-sures, flat gaskets are used while at higher pressure, O-ring gaskets in conjunction withring joints are used.

Welded Connections

In ranges to 700 bar (10,152.64 psi) welded thermowell connections are often used.Care should be exercised, especially at high flow velocities, to assure that the connec-tion nipples/thermowells are designed to be close fitting, to prevent damage or break-age of the thermowell due to vibrations at resonance.

Conical and Lens Type Connections

For high pressure applications (up to 4000 bar (58,015.07 psi)) in gas synthesis appli-cations, requiring fast responding and replaceable sensors, conical shaped seal sys-tems are used, in which the mating piece has an approx. 1° larger angle, so that theseal is effectively produced by a line shaped seal area. In this design, extremely highseal forces can be achieved.

Note:

The smaller the projected area of the seal, the higher the seal pressure becausewhen bolting the mating parts together, a higher compression force between theparts can be achieved.

85

Fig. 3-22: High pressure temperature sensor with conical seal

Pressure Tests

Often the manufacturer must provide a test certification showing that the seal is effec-tive under pressure (see chapter 6). Typically, a test pressure 1.5 times the pressurerating of the operating pressure is applied for 3 minute period.

86

3.2.4 Process Requirements

When selecting the optimal sensor for a particular application, the required propertiesmust first be defined:

– Short response time– Accuracy– Small space requirements

The result is a design with small sensors.

On the other hand, the process requirements must be considered:

– Temperature– Flow velocity– Pressure– Vibration– Abrasion– Aggressive media

These require a more substantial design with longer installation lengths, because:

– The temperature requires a reduction in the strength,– the flow velocity causes a bending force and resonance vibrations,– the pressure causes a radial force on the sheathed surface,– the vibration causes a load on the material, especially at the attachment point,– the abrasion causes material loss,– an aggressive fluid causes a loss of the wall thickness due to corrosion attack.

In addition to the many special designs, there are also thermowells, which are com-pletely defined in the standards (e.g. DIN 43772). The thermowell should provide pro-tection for the measuring inset against chemical and mechanical damage. The selec-tion of the thermowells is on the one hand dependant on the process parameters andon the other on the required measurement parameters.

87

88

The standard DIN 43772 includes the load diagrams for various thermowell designs.

Fig. 3-23: Typical load diagram, material 1.4571 (316 Ti)

Fig. 3-24: Pressure/Material dependent selection of thermowells (form 4 with 65 mm (2-1/2”) tapered length/installation length)

*) Form 4 (D2, D5)Protection sleeve c = 125mm (5“):Bending, flow impact lengths = 125 mm (5“)Thermowell diameter = 24 mm (0.95“)Thermowell inside diam. = 7 mm (0.28“)

**) Form 4 (DS)Protection sleeve c = 65 mm (2.6“):Bending, flow impact lengths = 65mm (2.6“)

Thermowell diameter = 18 mm (0.7“) Thermowell inside diam. = 3.5 mm (0.14“)

Flow velocityWater = 5 m/s (16 ft./s)Steam = 60 m/s (200 ft./s)Air = 60 m/s (200 ft./s)

12060 180 300240 360 420 480 60000

800

720

640

560

480*)

**)

320

160

240

400

80

Temperature [°C]

Per

mitt

ed p

ress

ure

[bar

]Vapor pressure curve

540

3.2.5 Thermowell Designs

Thermowells must satisfy the following functions:

• Position the temperature sensitive sensor tip in the process• Protect the temperature sensor• Seal the process areas from the environment.

Failure of any of these components can lead to operation interruptions, release of flam-mable, explosive or poisonous materials, equipment damage or personnel injury.Therefore a meticulous risk and load analysis is essential.

Thermowells, dependent on the application area, are subjected to certain legal require-ments. As pressurized parts e.g. materials, design, calculations, manufacture and test-ing must satisfy the Pressure Equipment Directive. Internationally the rules and regu-lations in the ASME-Codes have as wide acceptance. In explosion hazardous areas,the thermowells provide a separation between zones of different hazardous levels (seealso chapter 7).

Thermowells are available in proven and standardized forms with a variety of differentprocess connections.

Fig. 3-25: Thermowell designs (schematically)

For standardized thermowells, load diagrams are published in the corresponding stan-dard, which specify the maximum allowable pressure in air/steam or water at a specifictemperature and a specific maximum flow velocity. Often, however, thermowells devi-ate in dimensions and/or operating conditions from the standard values.

89

Thermowell Materials

In addition to the design and dimensions of the thermowells, the selection of the mate-rial is of decisive importance. The material must be compatible with the process condi-tions and have sufficient stability (see chapter 3.2.4 and chapter 3.2.6).

For pressure containing parts, material test certifications are often required for theirheat strength and/or notch impact strength. The load limits for the materials in the lowertemperature ranges are determined, e.g., from the 1 %- yield point and at higher tem-peratures from the 100,000 hour creep strength. These values are published as a func-tion of the operating temperature in the material standards or data sheets. The safetyfactor (e.g. 1.5 for ductile steel) and possible load reductions due to welded connec-tions can be found as a function of the material group in the relevant directives.

Thermowells made of brittle materials (e.g. glass, ceramic) require special consider-ations, since a single impact could lead to sudden and complete destruction. As a rule,considerably higher safety factors and protection measures are required relative to im-pact stresses. In critical installations a second barrier (compression fittings, solid elec-tric feedthrus, etc.) is necessary, which prevents the escape of hazardous material incase of a thermowell breakage.

Selection of the Thermowell Design

The medium acts mechanically on the thermowell through pressure, flow velocity andeddy formation. Therefore selection of a thermowell design includes:

• The stress due to the external static pressure,• the bending stress due to the flow of the medium,• the stress due to the outside induced flexural vibrations.

An example of a installation situation for thermowells is shown in Fig. 3-26.

90

Fig. 3-26: Thermowell installation example

The pressure strength can be increased by increasing the wall thicknesses. At highertemperatures, the strength values for many materials decrease to the point whereacceptable wall thicknesses can only be achieved by using higher heat resistant steelor nickel alloys.

The statistical calculations for the thermowell loads yield the stress conditions. Thestresses due to external pressure are superimpose on the bending stresses due to theflowing medium. As a function of the outside diameter of the thermowell, the skin-fric-tion coefficient, the velocity of the medium and its density a distributed load is producedon the thermowell. This causes a bending stress whose maximum occurs at the mount-ing location. The most effective method to reduce high bending stresses is to reducethe length of the thermowell. Additionally increases in the outside diameter at themounting location or selection of a stronger material are also possible alternatives.

In horizontal installations at higher temperatures a bending stresses can be producedby the weight of the thermowell because of the creep processes and lead to apprecia-ble deformations.

Distributed load

TemperaturePressure

θρa

Spec. densityVelocity

ρν

Medium

Bearing point Tip

Process tube

Flange adaptor

Vibrationable length

Product flow length Inne

r di

amet

er

Out

er d

iam

eterWelded seam

91

Vibration Analysis

The dynamic loads due to the vibration of the thermowells require a detailed discus-sion. The vibrations cause alternating stresses in the thermowell, which are superim-posed on the stress conditions described above.

In addition to the resonant frequency of the thermowells in its installed condition, theexcitation frequencies of external periodic forces are important. One of these excitationfrequencies are caused by vortex shedding of the flowing medium downstream fromthe thermowell. At certain flow conditions, a “Karman Vortex Street“ forms which alter-nately sheds individual vortices from the sides of the thermowell. The frequency of thevortex shedding is a function of the process parameters and the thermowell dimen-sions.

Fig. 3-27: Flow conditions around thermowells

The periodic excitation forces cause the thermowell to vibrate. The stress due to thevibration amplitude increases rapidly in the resonance range, i.e. when the excitationfrequency is the same as the resonant frequency of the thermowells.

Since the damping in the worst case can be assumed to be small, the amplification fac-tor of the vibrations at resonance approaches infinity. This quickly leads to fatigue andbreakage of the thermowell at the mounting location or at any other sharp edge or sud-den change in the wall thickness (Notch effects).

Periodic excitation forces, which can also be produced by pumps, compressors andother rotating or oscillating masses, are transmitted through the pipeline to the ther-mowell. Non-critical and aperiodic forces (e.g. individual pressure shocks), do not leadto excessive forces and long term vibrations of the thermowells.

0 < Re < 4

4 < Re < 40

40 < Re < 160

Re > 160

Laminar flow

Stagnation eddy

Kármán Vortex Street

Turbulent flow

92

As a consequence a very conservative design rule requires that the excitation fre-quency never exceed 80 % of the resonant frequency of the thermowells in applica-tions with a high risk potential.

When vibration problems exist, shortening the unsupported length (which also changesthe resonant frequency) is the most effective measure to prevent failures due to vibra-tion. The reduction of the effective total length can also be achieved by adding closefitting sleeves or supports at suitable locations. Welded sleeves can be used to reducethe length of the part protruding from the sleeve/thermowell.

In those applications where it is not possible to follow the 80 % design rule (e.g. tem-perature sensors for Diesel motors, turbines, compressors etc.), comprehensive typetests are required. They include, for example, vibration tests at resonant frequencypoint at the operating temperature, where acceleration amplitudes at the thermowelltips may exceed 150 g (150 times the acceleration of earth gravity).

After 10 million load cycles have been successfully passed, long term reliability can beassumed. In spite of this, the resonant frequency point should be passed quickly whenstarting up or closing down the system, when possible.

Optimization Measures

Unfortunately many measures to improve the mechanical stability have a negativeimpact on the measuring characteristics.

High load carrying, i.e., relatively thick walled thermowells result in a decidedly longerresponse times due to their heat capacity. They can be reduced by making the fit be-tween the measuring inset and the opening in thermowell tighter, reducing the thick-ness at the thermowell tips, as well as reducing the measuring inset diameter as far asthis is technically possible.

Thermowell with vibration desirable short installation lengths show a relatively largeheat loss. Possible improvement measures include reducing the temperature sensitivelength of the measuring inset to the end of the temperature sensor and reducing thethickness at the thermowell tip.

93

Tbl. 3-19: Summary of the primary optimization options for thermowells

Important for highly stressed thermowells is to avoid stress peaks at step diameterchanges, threads, weld seams etc. The so called Notch effect can be reduced by care-fully rounding all sharp edges at geometry transitions, selecting less sensitive threadtypes, move welded seams to less sensitive locations, etc.

It is possible to optimize the flow conditions by appropriate thermowell geometries, e.g.,a tapered thermowell with its continuously changing outside diameter reduces the for-mation of a vortex street and thereby the excitation forces.

Various operating conditions can be considered together, as long as the selections forthe undesirable conditions are defined (e.g. maximum flow velocity at maximum medi-um density and maximum pressure). It should be noted that the density of the mediummay increase if the phase changes or if it is cooled which adds to stresses on the ther-mowell.

Problem Corrective measuresThermowell geometry

Corrective measuresOperating parameters

Excitation frequency too close to resonance point

– Reduce unsupported length– Increase outside diameter

– Reduce flow velocity(Medium density has no effect)

Pressure force at tip too high – Increase outside diameter of the tip

– Select higher strength thermowell material

– Reduce operating pressure

Bending stress at the mounting location too high

– Increase outside diameter atthe mounting location

– Reduce length– Select higher strength

thermowell material

– Reduce flow velocity– Reduce medium density– Reduce operating pressure

94

Selecting Practical Thermowell Specifications

Several special programs are available to assist in selecting thermowell designs. Thebasis for the selections is the careful specification of the operating conditions anddesign details (see Tbl. 3-20). The determination of the correct entry parameters, aswell as the interpretation the selection results together with optimization measuresrequires, especially in borderline applications, a fundamental knowledge of the subjectand experience. Design and manufacturing quality are in the end, decisive for operat-ing safety of thermowells.

Tbl. 3-20: Information for selecting thermowell designs

Connections of Thermowells

For the dimension of the process connections there are standardized calculation meth-ods (e.g. for welded seam thicknesses, flange connections) or corresponding experi-ence values (e.g. nipples with seal rings, self sealing tapered threads).

For process connections with gaskets the so called sealing pressure is decisive. It is afunction, in addition to the type, of the material and dimensions of the gasket, as wellas the operating temperature and proper installation. For threads an appropriate lubri-cant to reduce the thread friction and prevent galling is recommended.

Thereby the stresses on the threaded nipples are reduced and higher sealing pres-sures at lower tightening torques are achieved. For threads with gaskets, retighteningafter the first load cycles to equalize the seating processes and maintain the gasketforces is recommended.

Category Required information Useful information

General SystemDesign

Special hazardous conditionsGeometric installation requirements

Medium CompositionTemperaturePressureFlow velocity

Density at operating conditions

Test pressureNormal volume, mass flowrate,Pipeline size

Material Temperature limitsCorrosion resistanceWeldablility

Available material specificationsProblems with corrosion, abrasionConnection materials

Geometry DiameterLengthConnection dimensions

Maximum possible diameterResponse timeHeat conduction error

95

3.2.6 Corrosion

Reasons for the Formation of a Corrosion ElementThe electrochemical processes, in which the corrosion occurs, are determined by thematerial, the ambient effects and the composition of the electrolytes. For the formationof a corrosions element, i.e. the generation of a potential difference, certain factorsmust be present:

• Material zones with electrically conductive materials at different potentials,• a connection between these zones for exchanging charge carriers (electrons),• completing the circuit by the electrolyte.

Corrosion elements can exist in parts, that appear to be made of “one“ material due tocomposition differences in the alloy or contamination.

Corrosion Types

Surface CorrosionSurface corrosion, which can be uniform or nonuniform over the entire surface, pro-duces crater type depressions. This can be countered by properly sizing the thermo-wells. Or, the material loss due to corrosion can be reduced by increasing the surfacequality. Uniform corrosion is easiest to combat through use of suitable materials.

Fig. 3-28: Uniform material disintegration corrosion shown schematically A Starting conditionB Material thickness disintegration of the part due to uniform corrosion K Grain (crystal)

96

Contact CorrosionContact corrosion occurs when two dissimilar metals are in contact in the presence ofan electrolyte. The less precious of the two metals is subjected to the most corrosion,the material loss is uniform. The problem is design related and can be counteracted,e.g. by selection of similar material type combinations.

High Temperature CorrosionThe suitability of materials for use at high temperature is primarily due to the build upof a protective oxide layer on the surface. The presence of this oxide layer reduces thedirect contact between the metal and the atmosphere, finally preventing it. The oxida-tion resistance of a material at elevated temperatures depends on the type of oxidewhich forms. If the oxide is loose and porous, the oxidation process continues until theentire surface is oxidized.

The selection of suitable alloys must be made considering the actual operating condi-tions. The oxidation resistance of Fe-Ni-Cr alloys at isothermal conditions is primarily afunction of their chromium content, while the Nickel and Iron components contributeonly slightly.

Under cyclic temperature conditions the degree of resistance can change appreciably.In this case, alloys with a higher Nickel contact are decidedly better, because it reducesthe thermal expansion and thereby the flaking off of the oxide.

Fig. 3-29: High temperature corrosion of CrNi-Steel 1.4841 (AISI 314) for use in waste Incineration systems at temperatures approx. 1300 °C (2372 °F) after 5-days-service

fehlt

97

Pitting CorrosionThe pitting corrosion is a localized, pinpoint shaped, penetrating type of corrosion,which in a relative short time can progress through the entire thickness of the metal.Since it actually eats into the metal and only exhibits point like damage on the surface,it is often difficult to recognize and therefore dangerous. It is greatly accelerated in chlo-ride containing aqueous solutions. The addition of Molybdenum (Mo) and higher chro-mium contents provides better resistance, e.g. 1.4571 (AISI 316) which contains 2.5 %Mo. The material 1.4539 (Uranus B6) with 5 % Mo appreciably improves the resistancecompared to 1.4571 (AISI 316).

Fig. 3-30: Pitting corrosion schematically I Passive layer, with small localized breakthroughs at which pinpoint and hole shaped corrosion occursII Active disintegration of the material

Fig. 3-31: Pitting corrosion in a Monel thermowell after usage in a chemical system

98

Crevice CorrosionCrevice corrosion occurs due to potentials in the narrow openings caused by the pres-ence of oxygen, such as may exist under a water surface or in narrow gaps, e.g. at thethermowell/flange connection. As a manufacturing countermeasure, the thermowellshould be welded to the flange without gaps. The material disintegration occurs as agroove or surface phenomenon. Since crevice corrosion is not always visually evident,it is one of the most dangerous types of corrosion. Steels with higher pitting resistanceare also less susceptible to crevice corrosion.

Fig. 3-32: Crevice corrosion schematicallyIII Passive layer, which will no longer be created in the narrowing gapIII Active disintegration of the materialIII Surface contamination, deposits, etc.

99

Intercrystalline CorrosionIntercrystalline corrosion is caused by selective corrosion. This occurs due the exist-ence of differing potentials at the grain boundaries, or due to nonhomogeneous struc-tures, in which the grain boundaries are dissolved. This type of corrosion occurs prima-rily in stainless steels when exposed to an acidic medium when, due to heating effects(450...850 °C (842...1562 °F)) in austenitic stainless steels and above 900 °C(1652 °F) for ferritic stainless steels the Chromium Carbides precipitate in a combined“critical“ form at the grain boundaries.

This causes a localized depletion of Chromium in addition to the precipitated ChromiumCarbides. For reducing these effects, steels with reduced Carbon content, so called“Low carbon“ steels such as 1.4404 (316L) or so called stabilized (with Titanium or Nio-bium) steels such as 1.4571 and 1.4550 (AISI 316Ti and 347) are used. The Titaniumor Niobium binds with the Carbon to stabilize the Ti- or Nb-carbides, so that even forcritical heat effects, the Chromium Carbides cannot be precipitated.

Fig. 3-33: Intercrystalline corrosion schematicallyIII Passive layer formed at grain boundaries where Chromium has not been depletedIII Selective attack near the grain boundaries in zones with depleted ChromiumIII Grain boundaries with Chromium Carbide

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Transcrystalline corrosionDiffering from intercrystalline corrosion the transcrystalline corrosion takes place withinthe grains in a material structure. It generally occurs along those sliding planes, onwhich an increased displacement density (the number of displacements which existwhich is a measure of previous deformations ) has occurred due to plastic deformationsand therefore a higher energy level has resulted. It is a form of corrosion with seriousconsequences, since it usually becomes apparent only after a breakage has occurred(e.g. after continuous, large tension loads).

Fig. 3-34: Transcrystalline corrosion stress cracks schematically; branching cracksII Passive layerII Localized penetration through the passive layer

101

Stress Crack CorrosionConditions for the occurrence of stress crack corrosion are the presence of tensile andresidual stresses (e.g. caused by welding or cold working), the presence of an electro-lyte and the existence of a crack.

These stresses lead to a movement of the internal displacements in the material. Onthe surface of the part sliding stages occur. If the surface is covered with a tightlyattached blocking oxide layer, it can rupture at the sliding stages and corrosion canattack the material. The interaction between the corrosion and the mechanical loadsleads to accelerated crack formation and early failure of the part.

The tendency towards stress crack corrosion is particularly evident in austenitic steels.This aided by Halogen ion containing corrosion elements, especially ones containingChlorides of Alkali or Earth Alkali metals, e.g. solutions which contain Sodium, Calciumor Magnesium chlorides. As the chloride ion concentration increases, so does thesusceptibility. For this reason in sour gas applications, e.g. according to NACE, a hard-ness of 22 HRC should not be exceeded for steels. Cold worked thermowells shouldbe stress relieved after they have been formed.

Fig. 3-35: Stress crack corrosion as the result of the interaction among of different factors

Material- Type- Composition- Structure- Precipitation- Grain boundaries- Surface- ...

- Residual stress- Operating stress

(stat./dynam./therm.)- ...-

- Composition- Electro-chemical

coditions (Redoxcorrosion potential)

- pH value- Temperature- Stream...

--

and

Medium

Mechanicalstress

SCC

102

Vibration Crack CorrosionVibration crack corrosion is the result of the existence of dynamic tensile stresses in thepresence of a corrosive medium. Displacement of the sliding stages of the material onthe surface of the part, which occurred due to the vibration forces lead to deep cracks.Even weak electrolytes can cause an early failure of the part.

Vibration crack corrosion can be counteracted by selecting suitable materials as a func-tion of the attacking medium and by appropriate thermowell design. For critical appli-cations operating near the stress limits, it is essential that design calculations be made.They should consider especially the critical resonance vibrations (see chapter 3.2.5).

Fig. 3-36: Vibration crack corrosion example of a flange/thermowell connection. The crack started at the beginning of the threads on the process side.

Stress and vibration corrosion can occur in all metallic materials. The corrosion processfor stress crack corrosion is a function of the material and occurs as electrolytic inter-or transcrystalline corrosion.

103

Hydrogen EmbrittlementHydrogen embrittlement is caused by cathodic reactions in an electrolyte. The activehydrogen diffuses into the material and is stored in the tetrahedron and octahedronspaces in the crystal lattice. The crystal lattice is expanded and the hydrogen atomsrestrict the elastic movement of the metal atoms (embrittlement). When stressed,cracks are formed eventually leading to failure of the material. As with all crack corro-sion the process remains unnoticed initially and only becomes apparent after a failurehas occurred. Special materials are used to prevent this type of corrosion.

The types of damage caused by hydrogen in an aqueous medium in steels are differentfrom those that occur at high temperatures in gases. The damage in gaseous media isbased primarily on the decarburization of the steel, while, dependent on the tempera-ture of the material and the pressure in the medium containing the hydrogen, thedecarburization may progress from the surface into the inner sections of the steel. Thediffusion effects are forced into the background.

In a truer sense, only the damages caused by the inner decarburization are designatedas hydrogen attacks. Since the decarburization can be suppressed if the carbon iscombined, all carbide building steel alloys are superior to the carbon steels in regard tocompressed hydrogen resistance. The resistance increases in general with increasingalloy content.

The specially developed steels for use against compressed hydrogen attack containabove all else, Chromium, Molybdenum and Vanadium elements in low alloy steelssuch as 1.7362 . They are standardized in SEW 590 (Steel Iron Material Sheet).

In addition to these materials, other steels can be used dependent on the stress con-ditions, particularly the material groups “heat resistant and high heat resistant steel“ aswell “stainless and acid resistant steel“.

Selective CorrosionDiffering from the corrosion mechanisms discussed up to this point, selective corrosiononly attacks one structure type, while the rest of the structure remains completelyintact. For the austenitic CrNi steels it is primarily the Sigma-Phase and the δ-Ferritewhich is converted to the Sigma-Phase which is selectively attacked. This type ofcorrosion occurs predominantly in the welded seams of austenitic CrNi steels. A selec-tive attack occurs for certain mixtures of reducing and oxidizing acids, e.g. hydrofluoric/nitric acid mixtures and in strong oxidizing sulphuric acid.

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General Comments

Even when the material selection is optimized, an aggressive attack could still occur incertain areas, e.g. at welded seams, because during welding, decomposition of thealloy can occur. Partial material compositions may be formed which have a lower resis-tance. In order to prevent this possibility, thermowells manufactured from solid materi-als are used where an aggressive medium is present so that weld seams on the medi-um side are not required. In addition, sometimes two thermowells are using, one placedinside the other.

In general, there are materials suitable for most media, but there is no material that istotally resistant. For the temperature measurements the interaction of aggressivemedia and high temperatures, disintegration is always a given. The degree depends onthe material selection, which may be used to minimize the effects or to maximize thelife of the instrument.

For selecting the correct material it is advisable, as a minimum, to use at least the samematerial quality which was used to make the tank/pipeline. If cost or strength is a con-cern, a material can be used with appropriate properties for the sheath material, e.g.Glass, Teflon, Tantalum, or an abrasion and corrosion resistant coating such as Stel-lite.

105

3.2.7 Material Selections

The following table provides an overview of the many materials used for thermowells.

*) As a function of the pressure load and corrosion attack, operating temperatures to 800 °C (1472 °F) arepossible.

Max.Temp.in °C (°F)

Material No. Material properties Application range

Unalloyed, Heat and High Heat Resistant Steel

400(750)

1.0305 (ASTM 105)

Unalloyed steel Welded and threaded thermowells insteam pipelines

500(930)

1.5415(AISI A204 Gr.A)

Low alloy heat resistantwith Molybdenum additive

Welded and threaded thermowells

540(1000)

1.7335(AISI A182 F11)

Low alloy heat resistant steelwith Chromium & Molybdenum additives

Welded and threaded thermowells

570(1000)

1.7380(AISI A182 F22)

Low alloy heat resistant steelwith Chromium & Molybdenum additives

Welded and threaded thermowells

650(1200)

1.4961 High heat resistant austeniticChrome-Nickel steel (Niobium stabilized)

Welded and threaded thermowells

Rust and Acid Resistant Steel

550*)(1020)

1.4301(AISI 304)

Good resistance against organic acids at moderate temperatures, salt solutions, e.g. sulfates, sulfides, alkaline solutions at moderate temperatures

Food and beverage industry, medical system engineering

550*)(1020)

1.4404(AISI 316 L)

Through the addition of Molybdenum higher corrosion resistance in non-oxidizing acids, such as acetic acid, tartaric acid, phospho-ric acid, sulphuric acid and others. In-creased resistance against intercrystalline and pitting corrosion due to reduced Carbon content

Chemical and paper industries, nuclear technology, textile, dye, fatty acid, soap and pharmaceutical indus-tries as well as dairies and breweries

550*)(1020)

1.4435(AISI 316 L)

Higher corrosion resistance than 1.4404, lower Delta-ferrite content

Pharmaceuticalindustry

550*)(1020)

1.4541(AISI 321)

Good intercrystalline corrosion resistance. Good resistance against heavy oil products, steam and combustion gases. Good oxidation resistance

Chemical, nuclear power plants, textile, dye, fatty acid and soap industries

550*)(1020)

1.4571(AISI 316 Ti)

Increased corrosion resistance against cer-tain acids due to addition of Molybdenum. Resistant to pitting, salt water and aggres-sive industrial influences

Pharmaceutical industry and dairies and breweries

106

Tbl. 3-21: Thermowell materials

For applications at low temperatures, austenitic Cr-Ni or Ni alloys are used. They arecharacterized by especially high toughness at very low temperatures.

Max.Temp.in °C (°F)

Material No. Material properties Application range

Heat Resistant Steel

1100(2012)

1.4749(AISI 446)

Very high resistance to Sulphur con-taining gases and salts due to high Chromium content, very good oxidation resistance not only at constant but also for cyclical temperatures(Minimum resistance to Nitrogen containing gases)

Use in flue and combustion gases, industrial furnaces

1200(2192)

1.4762(AISI 446)

High resistance to Sulphur containing gases due to high Chromium content(Minimum resistance to Nitrogen containing gases)

Use in flue and combustion gases, industrial furnaces

1150(2102)

1.4841(AISI 314)

High resistance to Nitrogen containing and Oxygen poor gases. Continuous use not between 700 °C (1292 °F) and 900 °C (1652 °F) due to embrittlement (higher heat resistance than 1.4749 and 1.4762)

Poser plant construction, petroleum and petrochemical, industrial furnaces

1100(2012)

2.4816(Inconel 600)

Good general corrosion resistance, resistant to stress crack corrosion. Exceptional Oxidation resistance. Not recommended for CO2 and Sulphur containing gases above 550 °C (1022 °F) and Sodium above 750 °C (1382 °F)

Pressurized water reactor, nuclear power, industrial furnaces, steam boilers, turbines

1100(2012)

1.4876(Incoloy 800)

Due to addition of Titanium and Alumi-num the material has especially good heat resistance. Suitable for applica-tions, where in addition to scale resis-tance, highest toughness is required. Exceptional resistance to carburizing and nitration

Pressurized water reactor, nuclear power construc-tion, petroleum and petrochemical, industrial furnaces

107

3.2.8 Ceramic Thermowells

Metal thermowells are preferred since they assure an absolute seal against the medi-um and the pressure. Their use is limited to temperatures below 1150...1200 °C(2102...2192 °F), because their mechanical strength as well as their oxidation resis-tance above this temperature range can no longer assure a sufficiently long operatinglife.

Ceramic thermowells, because of their comparatively poorer mechanical properties(very brittle) are only used when the operating conditions exclude the use of metal orfor chemical resistance or for very high measuring temperatures. In the temperaturerange 1200...1800 °C (2192...3272 °F) ceramic thermowells must be used.

Installation Orientation

In order to assure satisfactory operation, a number of special aspects must be consid-ered. Ceramic thermowells break easily and are shock sensitive, and have lowmechanical strength at high temperatures.

Rules of thumb for using ceramic thermowells:

• Keep the length short• Install vertically• Approach higher temperate zones very slowly• Keep away from direct vibrations • Protect from added weight due deposits• Avoid impact stresses from flying particles• Store dry (best in an oven).

It is not essential that the measuring location be in the middle of the oven chamber. Ata shorter distance from the wall, i.e. a shorter installation length, the temperature profileis practically constant (as long as the wall is not cooled).

Since the temperatures at the wall or at the lining in a furnace are usually less than1200 °C (2192 °F), heat resistant steel materials can be used for such applications.The ceramic thermowell should be inserted in a metal supporting tube in order to keepthe unsupported length, which might be subjected to bending forces, short. This designalso has the advantage, when the temperature sensor is mounted in the support tubeusing the usual sliding collar/flanged stop, that it can be introduced slowly stepwise intothe process zone.

108

Fig. 3-37: Installation of a straight thermocouple with an adjustable mounting

Thermal Shock Resistance

The ceramic thermowell materials used have different sensitivities to thermal shock.

The ability to withstand temperature changes decreases with increasing purity of the(Al2O3) thermowells (C 530 > 80 % purity, not gas tight; C 610 > 60 % purity, gas tightand C 799 > 99 % purity, gas tight). Even hairline cracks in the ceramic thermowell canallow foreign materials to infiltrate and cause the thermal voltage values to drift. To pre-vent cracks, care must be exercised when installing or removing the thermowell fromthe process. It should only be subjected to gradual temperature changes.

The use of an internal thermowell made of a gas tight ceramic inside an outer thermow-ell made of a thermal shock resistant ceramic is advantageous. In this design, the outerthermowell protects the inner thermowell. The air layer between the two thermowellsalso protects the inner thermowell from a too large temperature shock. This increasesthe life of the temperature sensor.

109

Installation Information

Decisive is the temperature of the process into which the sensor is to be inserted.

If the sensor is to be installed under these conditions, then the procedure is to insertthe sensor to the middle of the furnace liner, wait 10 minutes, and then continue toinsert the sensor in 10 cm (3/8”) steps waiting another 5...10 minutes after each step.Using this procedure, the sensors will be preheated by the radiation from the interior ofthe furnace to slowly reach the medium temperature.

Tbl. 3-22: Ceramic thermowell materials

Furthermore, for special applications, e.g. metal melts, thermowells made of carbidesor nitrides may be used.

Ceramic thermowells

Max. operatingtemperature in °C (°F)

Material No. Material properties

1400(2550)

C 530 Temperature change resistant, fine pores, not gas tight, shock sensitive

1500(2750)

C 610 Gas tight, high fire resistance, average temperature change resistance, low AI2O3 purity, shock sensitive

1800(3250)

C 799 Very gas tight, highest fire resistance, minimal temperature change resistance, shock sensitive

If these precautionary measures are not observed, the ceramic tubecan be destroyed by internal heat stresses!

110

3.3 Application Specific Temperature Sensor Designs

Hot Gas Measurements in a FurnaceA temperature sensor measures changes in gas temperatures very slowly due to thepoor thermal conductivity of gases. In order to reduce large errors due to thermal radi-ation (cooled walls), which may exist in blast furnaces, vacuum temperature sensorsare utilized. The hot process gasses are drawn off using a vacuum created with com-pressed air.

Fig. 3-38: Vacuum temperature sensor in a blast furnace

Temperature Measurements in High Pressure / High Temperature ReactorsIn these applications temperature sensors with in- and outside ceramic thermowellsand used. The thermocouple wires are sealed by a pressure tight connector as theyexit to the connection box. To protect against aggressive fluids which might influencethe thermocouple characteristics (e.g. sulphur in Claus Processes), an inert purge gasis introduced through a fitting. This creates a positive pressure in the thermowell. Thepurge flow can be regulated or increased using an additional outlet connection.

Purge gas will only flow if its pressure is greater than the process pressure. Only a verysmall purge flow is usually required. Applications include the manufacture of chemicalproducts which require the addition of high pressure/temperature elements for thereaction (synthesis reactors, fertilizer production, etc.).

Connectionfor vacuummeter

Com

pressedair

111

Fig. 3-39: Purged thermocouple in a high pressure reactor

Temperature Measurements in Particle Loaded Gases

For the pneumatic transport of granulates and powders a temperature measurement isoften required in order to monitor the temperature to assure that the ignition limit is notexceeded. The temperature sensor, which is inserted in the flow stream is subjected toa high degree of abrasion. It is possible to counteract abrasion by installing armorcoated thermowells (e.g., with Stellite, see Fig. 3-40), low wear tips made of solid ma-terials, eccentrically drilled thermowells or by installing an deflecting impingement rodahead of the thermowell. This temperature sensor design is used in wood and coal pro-cessing, cement and glass industries and in coal fired power plants.

Fig. 3-40: Armor coated thermocouple in an abrasive gas stream

112

Temperature Measurements in Flue Gas Channels

Filter systems in smoke stacks are very sensitive to overheating. Therefore it is impor-tant to recognize a temperature increase very quickly.

Since a horizontally installed, thin sheathed temperature sensor is not sturdy enoughand a minimum insertion length is required, a special design is required. The tempera-ture sensor in this design has a support pipe upstream of the measuring element andwhich bent at a right angle to guide the flow.

Fig. 3-41: Fast responding temperature sensor in a flow channel

113

Multipoint Temperature Sensors for Temperature Measurements in Large Tanks

In chemical processes the temperatures in large volumes are often monitored. Sincethe temperature distribution in a large tank may not be uniform, multiple measuringlocations are necessary, which are distributed in a representative manner throughoutthe volume. Since most tanks only have a single opening at the top, multipoint sensorsare used. They have a number of measuring locations within a single thermowell. Mul-tipoint sensors with lengths up to 20 m (65 ft.) and weighing more that a ton are notuncommon.

Good heat coupling is established in thermowells by the contact between the measur-ing element and its inside wall. Individual designs for explosion and pressure proof ap-plications are possible. They are used for status monitoring in liquid and solids storagetanks.

Fig. 3-42: Multipoint temperature sensors in storage tanks and process reactors

114

Temperature Measurements in Metal Melting and Salt Baths Using Angled Thermocouples

These temperature sensors are used primarily to measure temperatures in non-ironmetal melting furnaces and salt baths for hardening. For vertical installation in openvessels an angled design is used so that the connection head and connection cablescan be mounted outside of the radiating surface at the top of the furnace. Suitablematerials made of thermal shock resistant ceramic are used for thermowells, as well asmetal. Since the thermowell for direct immersion in the molten materials is stressed tothe maximum, it is considered to be a consumable part. Its durability can be increased,if in this region, an additional protective sleeve is installed over the thermowell.

For waste incineration furnaces, rotary kilns, fluidized bed furnaces and air heaterapplications, thermowells made of silicon carbide, metal ceramic or porous oxideceramic are particularly well suited because of their high temperature resistance, hard-ness and abrasion resistance together with their resistance to acid and alkali vapors.These temperature sensor are then not angled, but are designed as “straight thermo-couples“.

Fig. 3-43: Angled thermocouple in a crucible

115

Resistance Thermometers with Extremely Short Response Times

For applications where control functions require that process temperature changes berecognized very quickly, special designs have been developed. The designs are suchthat the measurement resistor is sintered into the measuring inset tip with using a highheat conducting material. The measuring tip itself is designed as an adapter sleeve,which fits closely into the thermowell, and becomes part of the exchangeable measur-ing inset. As a result of the extremely good heat transfer possible with this design,response times τ0.5 of less than 3 seconds can be achieved (measured in flowing waterat v = 0.4 m/s (1.3 ft/s).

Temperature sensors of this design are predominantly used in the primary circulatingloops in nuclear plants, as well as in safety relevant applications for energy balancingin chemical systems, where the highest safety requirements must be satisfied, evenduring a failure condition. Process parameters include flow velocities up to 15 m/s(50 ft./s), pressures to approx. 175 bar (2,538.16 psi) at a maximum temperature of330 °C (626 °F).

Fig. 3-44: Fast response temperature sensor in a reactor cooling pipeline

116

Temperature Measurements in Plastic Extruders

An exact knowledge of the product temperature during the extrusion process is anessential factor to assure the workability of the material and the quality of the endproduct.

The measurement is difficult because a built in sensor

• would interfere with the flow of the extrusion stream,• must have a very rugged construction, since the processing pressures

are between 300...500 bar (4,351.13...7,251.89 psi),• would be greatly affected by exposure to the external heat jacket.

The design for this application is a massive sensor with a short length, in whose tipmeasuring locations at multiple steps are incorporated. Since it is not possible to pre-vent the effects due to external heat sources, a measurement of the temperaturegradient allows a temperature determination to be made. In this way meaningful valuesfor the temperature of the plastic mass can achieved.

Fig. 3-45: Extruder temperature sensor

117

Temperature Sensors for the Food and Pharmaceutical Industries

Temperature sensors for these applications must be designed in accordance with stricthygienic requirements. This means that the construction must not have any small gapsor dead spaces, where product or residue could be deposited in the sensor. The tem-perature sensor must be able to be cleaned and sterilized without being disassembled.This property is classified CIP-Capable (Cleaning In Place) and SIP-Capable (Sterilis-ing In Place). The connection head must incorporate a high level of protection, in orderto remain sealed when cleaned with a steam jet.

The measuring task requires very fast response times (< 3 s) at a high accuracy, so theproduct quality can be maintained within tight limits. High alloyed stainless steel mate-rials are used such as 1.4571, 1.4435 and 1.4404 (AISI 316Ti, 316L).

Fig. 3-46: Temperature sensor with ball type welded adapter for hygienic applications and installation at various angles

118

Temperature Measurements of the Tank Content with a Flush Thermowell

All sided heat contact is not always possible with an insertion thermowell, because itmay interfere with the process or cannot withstand some of the forces which may occur,e.g. in tanks with stirrers, the thermowell would interfere with the wall scraping stirrer,so the measurements must be made flush with the wall.

Special measures must be considered in the sensor design to assure that:

• the sensor is thermally decoupled from the wall,• the contact area with the medium large enough,• the measurement will not be affected by external heat jackets.

A suitable sensor design assures that the sensor element is in contact only with theinterior of the tank and not with its mechanical mounting arrangement.

Fig. 3-47: Flush tank wall installation of a temperature sensor

119

Temperature Sensors for Heat Quantity Measurements

Since heat energy is very expensive, cost effective balancing is required with veryprecise measurements. The requirements relative to the design and allowable mea-surement deviations for heat quantity sensors are defined in the Standard EN 1434-2.Because the accuracy requirement for the sensor pair is in the range of 0.1 °C(0.18 °F), it is very important, that in addition to the correct selection of the sensor, therelationship of the sensor mass to the installation length be considered in order to pre-vent any external influences from effecting the measurement.

Temperature sensors without thermowells with extremely short measuring resistors areused to allow an exact measurement to be made in the center, as required, of the usu-ally small diameter pipelines while minimizing the heat loss.

Fig. 3-48: Temperature sensors for the heat quantity measurements

120

Temperature Measurements on Surfaces

The surface temperature measurement has gained increasing importance. For a vari-ety of reasons (measuring location hard to access, sterility of the system, no distur-bance in the flow circuit, etc.) the direct insertion of temperature sensors into the pro-cess loop is often undesirable. For such applications, the non-contacting infra-redmeasuring methods are not the only ones used (see chapter 4). Surface temperaturesare measured using contacting temperature sensors especially in applications whereundefined or changing conditions relative to the emission coefficient ε may exist. Adifferentiation is made between two basic methods, a portable system (sensorspositioned manually, touch sensors) and a system with sensors permanently mountedon the surface. For process systems, only the permanently mounted sensors are ofimportance.

For temperature measurements on the surface of bodies a basic knowledge of the tem-perature difference between the surface and the enclosed medium must be known.Surface sensors operate within a defined temperature gradient range.

Errors may result when making surface temperature measurements due to effect of thesensor (interference) itself on the surface temperature (undisturbed).

When applying surface temperature sensors it follows that not only the actual errors inthe sensor itself must be determined by a calibration, but also, the magnitude of theeffect the temperature sensor has on the surface temperature itself must be deter-mined. The correct application of surface temperature sensors requires extensiveexperience in the field of temperature measurement technology. Requesting technical,application oriented recommendations from the temperature sensor manufacturer arerecommended.

To keep the heat removal by the measurement element as small as possible, its massshould be a minimum. For small surfaces, thermocouples, because of their small masswith diameters of 0.5 mm (0.020“) are often used.

121

Sensor mounting methods vary for each installation. They can be mounted using sol-dering, welding, screwing or held in place by a spring. For larger cross sections, resis-tance thermometers are also used. They are designed as bottom sensitive types for thespecific mounting arrangement (tangential/axial). They are either held in place by apipe clamp or clamped using a metal plate screwed onto the surface.

Fig. 3-49: Measurements on a pipe surface

122

Pipe Wall Temperature Measurements in Heat Exchanger Pipes

In heat exchangers e.g., a liquid medium is pumped through a pipe bundle installedwithin a hot gas filled tank. Due to the large contact area, the medium approaches thetemperature of the gas. Since the temperature and pressure in the pipes is usually high,near the material limits, monitoring the wall temperature of the pipes is necessary, inorder to prevent over stressing the materials and possibly rupturing the pipes.

The design of a suitable sensor must assure good contact with the wall without, due itsown mass and its contact with the hot gas, produce erroneous results. Since operatingtemperatures may reach approx. 560 °C (1040 °F), the use of conventional insulatingmaterials is for all practical purposes excluded. The solution for this problem is a sensorwith a mineral insulated cable with a V-shaped knife edge whose measuring section isbent toward the inner wall and welded to assure good contact with the pipe wall. In thisdesign, the welded portion forms a cap over the measurement element and which is atthe same temperature as the pipe wall. To compensate for the temperature differences,additional compensating windings are incorporated.

Fig. 3-50: Measurements on a pipeline in a heat exchanger

123

Temperature Measurements in Housings and Walls

In order to measure the temperature in solid bodies, the measuring element is posi-tioned in a hole drilled into the object to be measured. The hole itself and the measuringelement disturb the temperature field, so that measurement errors result. The mea-surement error increases as the size of the hole increases in relation to size of theobject and how different the heat conductivity of the inserted temperature sensor isfrom that of the object.

Guidelines for the ratio diameter/depth of the hole for temperature measurements inobjects are:

• With good heat conductivity 1:5• With poor heat conductivity 1:10 to 1:15.

The solution is a sensor consisting of two independent, spring loaded sheathed ther-mocouples, which due to their small mass form point shaped measuring locationswhich essentially assure an error free measurement. These temperature sensors areused, among others, in high, thermally stressed elements in power plants.

Fig. 3-51: Difference temperature measurements within a wall

124

Temperature Measurements in Bearing Shells and Housings

To measure the temperature of a housing a small hole is usually added with a minimumdepth. This requires temperature sensor designs with very short, temperature sensitivelengths. They are usually pressed against the bottom of the hole by a spring to assuregood thermal contact. Silver tips are also used to optimize the heat transfer. Since, e.g.,there are enormous vibration forces present in Diesel motors, the measuring sensorsmust be designed with an extremely rugged internal construction coupled with the useof reinforced springs.

These temperature sensors are used to measure bearing temperatures in pumps,turbines, blowers and motors. For use in large Diesel motors in ships, type tests arealso required by the Ship Classification Societies such as Lloyds Register of Shipping,German Lloyd and others.

Fig. 3-52: Temperature measurements in pump bearings

125

Temperature Measurements in Brakes and Railroad Train Axles

To monitor the brakes in high speed trains, temperature sensors with the followingcharacteristics are required:

• Small, rugged design,• resistant to high mechanical shocks,• special measuring surfaces, which can be mounted

as close to the rubbing surfaces (brake linings) as possible,• fast response.

An appropriate design is a small, spring loaded sensor with a conical seat mounted inthe brake caliper housing.

Fig. 3-53: Temperature measurements in a brake caliper

126

3.4 Dynamic Response of Temperature Sensors

3.4.1 Introduction

The dynamic response of a temperature sensor describes the reaction of its outputsignal to a change in the temperature of the medium being measured.

When making contacting temperature measurements, the temperature sensor is indirect contact with the measured medium. The temperature which exists, after a equi-librium state is reached, is a “mixed temperatures“ consisting of the original tempera-ture of the temperature sensor and the temperature of the measured medium. Ingeneral, the thermal mass of the measured medium is decidedly greater than that ofthe temperature sensor, so that this “mixed temperatures“ and the temperature of themeasured medium are the same.

When the temperature of the measured medium TM(t) changes, the temperature sen-sor reacts. Its output signal TS(t) approaches the new temperature. Finally when theoutput signal of temperature sensor no longer indicates any measurable changes, thestationary status is reached.

During this time period the time related difference is

which is defined as the dynamic measurement error. The dynamic response of a tem-perature sensor is almost exclusively a function of the equalization processes occurringbetween the measured object or medium, the temperature sensor and the ambientconditions.

Information about the basic values of the dynamic response of the temperature sensorare required e.g. to estimate the response time after a sensor is inserted into a mediumat constant temperature, for the measurement or transmission of fast temperaturechanges and for use in temperature controlled circuits.

ΔT(t) = TS(t) – TM(t)

127

3.4.2 Step Response and Transfer Functions, Response Time and and Time Constants

If a temperature sensor is at a starting temperature TS0, e.g., the ambient temperatureTAmb, at time t = 0 is brought into thermal contact instantaneously with a measuredobject or medium at a constant temperature TM, e.g., by contact or immersion, a ther-mal equalization process begins. From a curve of the sensor temperature TS(t) as afunction of the time, the so called step response, the value of primary interest is theresponse time tR which is the time when the dynamic measurement error becomes lessthan a meaningful, defined portion of the measurement uncertainty δ from the startingtemperature difference TS0 – TM:

Fig. 3-54: Typical response time curve (step response) also called transfer function of a temperature sensor

The characteristic value for the temperature sensor is its response time. It is called thetime constant:

T05 and T09 are the times the temperature sensor requires to detect 50 % (90 %) of atemperature step change. The magnitude of the temperature jump is of lesser impor-tance. Therefore, the response to a temperature change by the temperature sensor isa function of the remaining temperature difference from the temperature of the mea-sured medium. The temperature of the measured medium will only be reached exactlyat t = ∞.

TS(tR) – TM ≤ δ (TSO – TM)

70

0 10 20

δ = 5%

t95%t 50% t99%40

20

60

40

50

30

TM

T (t)S

TS0

δ = 1%

ΔT(t)

0

20

40

60

80

100

Te

mp

era

ture

T[°

C]

Tra

nsfe

rfu

nctio

nh

(t)

[%]

Time t [s]

128

3.4.3 Establishing the Dynamic Values

According to VDI 3522 and EN 60751 the following two measurement conditions arerecommended to determine comparable dynamic values:

air: TA ≈ 25 °C (77 °F), vA = (3 ± 0.3) m/s (→ αA)

water: TW ≈ 25 °C (77 °F), vW = (0.4 ± 0.05) m/s (→ αW)

When these values are to be converted to other application conditions, the effectiveheat transfer coefficient for the measurement conditions must be known. They can beestimated from values listed in the VDI-Heat Atlas.

Listed in the following table are the values at the above stated standard measuring con-ditions.

3.4.4 Influencing Factors

The values T05 and T09 are dependent on the installation parameters, the temperaturesensor and the measured medium.

The Main Factors are

For the measured medium:• heat capacity,• heat coefficient,• heat transfer coefficient to the temperature sensor,• flow velocity.

For the temperature sensor:• size (generally the diameter),• weight,• materials used,• internal construction.

The influence factors for the measured medium are given values. These can hardly beoptimized. For the temperature sensor however, there are a number of measures whichcan be taken to shorten the response time.

The most important are:• reduction of the diameter in the region of the sensor,• reduction of the mass in the region of the sensor.

These two measures are interrelated.

D [mm] 0.2 0.4 0.6 0.8 1 2 4 6 8 10 20

[inch] 0.008 0.016 0.025 0.031 0.039 0.079 0.157 0.236 0.315 0.394 0.787

αA [W/m2K] 414 290 237 205 184 132 95 79 70 64 47

αW [W/m2K] 28910 20540 16890 14700 13260 9670 7190 6100 5460 3990 3260

129

The temperature sensor only reaches a constant condition when its temperature ishomogeneous. A total warming of the sensor is reached quicker in smaller sensorsthan in larger ones. It is important to assure, if such measures are taken, that themechanical stability is not overloaded.

The thermowell geometries are also factors affecting the optimization of the responsetime, as well as the mechanical requirements.

• Position the sensor in the middle of the pipe

When laminar flow exists, then the highest flow velocity of the measured medium is inthe middle of the pipe. If such measures are employed, assure that the mechanical sta-bility is not jeopardized. Sensor installation examples see chapter 3.2.

Another means which can be utilized to achieve faster response is to use thermallyconductive coupling materials, e.g. heat conducting paste (for Tmax < 200 °C (392 °F)),or the use of thermowell points made of good heat conducting materials. The multitudeof sensor geometries preclude the presentation of a complete listing.

The effect that the design and dimensions have on the dynamic response of a temper-ature sensor as well as its construction and especially the heat transfer conditions isshown in Fig. 3-55. The very different responses to a step change are shown for thesame measuring conditions (flowing water) and the same resistance thermometermeasuring inset (Ø = 6 mm (0.236”) ), due to the addition of a thermowell and finally,due to addition of a corrosion resistant Teflon coating 0.5 mm (0.020“) thick.

Fig. 3-55: Transfer function for resistance thermometers of different designs in water vW = 0.4 m/s (16 ft./s), TW = 25 °C (77 °F)

0 10

10

0

20

30

40

50

60

70

80

100

90

20 30 40 50 60 70 80 90 100 110 130120Time t [s]

Tran

sfer

func

tion

h(t)

[%]

Measuring insetwith thermowell

Measuring inset with thermo-well and 0.5 mm coating

Meas-uringinset

130

3.5 Aging Mechanisms in Temperature Sensors

Temperature sensors, during use, are subjected to application related aging effects.These complex processes, which define the long term characteristics of the sensor inan application, are generally categorized as “drift“. They are the result metallurgical,chemical and physical effects.

The quantitative effects are primarily due to the temperature itself. The consequencesof these effects are seen in a drift resulting from the changes in the thermal voltages orresistance values. The values of the thermal voltages and resistances, continuallychange from those defined in the Standard Value Tables or the Standard Value Seriesfor the ideal temperature sensor.

The causes can be roughly divided into two groups:

• drift, due to mechanical damage of the temperature sensor or the sensor element,

• drift, due to metallurgical changes in the sensor.

It can be stated that mechanical damage is almost always the catalyst for metallurgicalchanges in the sensor materials.

3.5.1 Drift Mechanisms for Thermocouples

K-State (Short Range Ordered State)

This effect is not actually drift, because its result can be eliminated by appropriate heattreatment of the sensor. The technical effect is essentially identical to normal drift char-acteristics. Since Type K (NiCr-Ni) thermocouple is the most commonly used thermo-couple, and since many users are unaware of these K-State problems, this problem willbe presented in detail. The NiCr-leg of Types K (NiCr-Ni) and E (NiCr-CuNi) are sub-jected to a special effect, which occurs when the wires are cooled quickly from temper-atures in the range of 400...600 °C (752...1112 °F), causing a change in the thermalvoltages (essentially undefined).

131

This effect, often called an approximation effect, alters the structure of the individuallattice elements and is usually referred to as K-Effect or K-State. Practically all metalsof technical importance, solidify either as face-centered-cubic metals (Nickel), body-centered-cubic metals (Chromium) or as hexagonal-lattice metals (Zinc). There arealso other solidification forms with tetragonal, rhombic lattice structures as well asothers.

For an ideal, pure metal, all the lattice spaces would be occupied by atoms of the sameelement during solidification. For the NiCr-alloy, an important thermocouple material,which solidifies as a face-centered-cubic lattice (Fig. 3-56) in which the lattice spacesare occupied by atoms of the individual alloy components (Nickel and Chromium)resulting in a mixed crystal. Viewed submicroscopically, the lattice structure of a meltas it solidifies, has the same proportion of individual atomic elements as the stoichiom-etry of the composition of the alloy.

Fig. 3-56: The face-centered-cubic crystal lattice

Considering the atomic structure of a NiCr-crystal more closely, the resultant latticeoccupancy by Ni or Cr atoms is dependent on the rate of cooling of the molten metal.Starting by considering a NiCr-alloy, which is at a temperature above 600 °C (1100 °F),the atoms are diffused into the crystal structure, which corresponds to a face-centered-cubic lattice in which the former atoms of the “crystal“ are formed by Chromium atoms,the central atoms by of the individual faces by Nickel. Observing this structure perpen-dicular to a face, then the positions of the Ni- and Cr-atoms is as shown in the followingfigure.

Atom position

132

Fig. 3-57: The large-range-ordered state structure of the Ni and Cr atoms at temperatures > 600 °C (1112 °F)

If the NiCr-leg of a Type K thermocouple is used in a large-range-ordered state (U-State) always at temperatures > 600 °C (1112 °F), then reproducible thermal voltageswill result. If this NiCr-leg is slowly cooled (< 100 K/h) to temperatures < 400 °C(752 °F), then an atom structure will be formed called short-range-ordered state (K-State) (Fig. 3-58). In this condition, the typical large-range-ordered state structure(Cr atoms at the corners, Ni atoms in the center of the faces) is found in small sectionsof the lattice, interspersed with “distorted“ lattice areas.

Fig. 3-58: The short-range-ordered state structure of Ni and Cr atoms

This lattice structure also produces reproducible thermal voltages. However, if the cool-ing from temperatures > 600 °C (1112 °F) occurs very quickly, then the atoms do nothave sufficient time to move from a large-range-ordered state structure into a short-range-ordered state structure. The result is a mixed structure somewhere between thetwo regular structures described above, i.e. an arbitrary structure, which is in effect anunordered structure (Fig. 3-59). The positioning of the Ni and Cr atoms in any arbitrarystructure to each other is possible, dependent on the starting temperature and the timeprofiles of the cooling.

Large ordered state

Chromium Atom

Nickel Atom

Short ordered state

Chromium Atom

Nickel Atom

133

Fig. 3-59: An unordered state

If a NiCr-leg, which has an unordered atomic structure due to rapid cooling, is allowedto remain for a longer period of time at temperatures < 400 °C (752 °F), then, as a re-sult of thermal diffusion the atoms will gradually revert to the short-range-ordered statestructure. In the unordered condition and in the transition phase to a short-range-ordered state structure, the thermal voltages generated by this leg changes. A thermalvoltage change equivalent up to 5 K can occur and cause erroneous measurements.For the accuracy and reproducibility, the generated thermal voltage and therefore thesuitability for measurement and control functions, the as received condition of theType K thermocouple is of decisive importance.

The last step in the manufacturing of thermocouples or mineral insulated thermocouplecables is always an annealing above 600 °C (1112 °F), to relieve the stresses whichresulted from cold working the material. The NiCr-leg therefore has a large-range-ordered state structure. This is followed by rapid cooling in order not to impair the weld-ablility of the sheath material of the mineral insulated thermocouple cables. The NiCrleg is then in an undefined transition stage, previously described, between K and U. Anew thermocouple delivered in a transition stage will quickly change to the K-State, pro-vided the temperature at the measuring location is > 600 °C (1112 °F).

In the temperature gradient region between the hot and cold ends, a slow transition tothe U-State occurs. Continually changing thermal voltages are the result, which onlystabilize after the transiting phase has been completed. The values can varyappreciably from the thermal voltages of a new, as received, thermocouple. Only ther-mocouples, that are shipped in the “set“ K-State (this can be accomplished by a sec-ond, more complex final annealing and by a slow, defined cooling under an inert gas),provide immediate, stable temperature indications. Also to consider is that in theordered structure state the NiCr-leg, and thereby the thermal voltages it generates, inthe temperature range between 250 °C and 600 °C (482 °F and 1112 °F) is relativelyundefined. This makes the use of Type K thermocouples for measuring rapidly chang-ing temperatures of limited applicability, since the thermal voltage changes, that occurduring the crystal transition stage, are a type of signal hysteresis.

Chromium Atom

Nickel Atom

134

A remedy is to add a small amount of Silicon to the alloy for both legs (in thermocoupleType N, NiCrSi-NiSi), which appreciably reduces the short order effects to the pointwhere they, for all practical purposes, are negligible. It should be noted that the replace-ment of Type K by Type N thermocouples has proceeded very slowly in technicalapplications.

Selective oxidation of Cr

When using NiCr-alloys (typically used in Type K thermocouples) exposed to an oxy-gen poor, neutral or reducing atmosphere in combination with moisture. Green rotoccurs in the temperature range between 800 °C and 1000 °C (1472 °F and 1832 °F)a selective Chromium oxidation of the NiCr-leg occurs. Under the described conditionsthe stabilizing, continuous coating of Nickel oxide cannot form, similar to the conditionwhen an excess of Oxygen is present. The Chromium in the conductor is depleted, thecomposition of the alloy changes and the thermal voltages decrease dramatically. Thethermal voltage for a thermocouple damaged by Green rot corresponds to the temper-ature difference between the temperature at the measuring location if no wire damagehad occurred and the reference junction. The measuring location has effectively movedfrom the tip to the “back“. Measuring errors caused by Green rot can be as large as afew 100 °C (212 °F). The Ni-leg is not subjected to Green rot.

Radioactive Radiation

The α- and β-rays have practically no effect on the output signal of a thermocouple. Theγ-rays however heat the measuring location and dependent on the intensity and volumeexposed to the radiation, cause errors of several hundreds of degrees. Thermal neu-tron radiation however, changes the thermal material itself. Neutrons are absorbed asa function of the cross section of the material. The subsequent radioactive decaycauses conversion in stages into other elements with different thermal properties. Thetype and duration of the conversion is a function of the radiation dosage. Materials witha smaller absorption cross section experience only small changes while materialsexposed to higher absorptions are quickly and completely converted.

135

The following effects occur in the most important thermal materials:

• Rhodium has a high absorption cross section and is converted within a short operating time. Thermocouples Types R, S and B are therefore unsuitable for applications whereneutron radiation exists.

• Tungsten-Rhenium thermocouples experience changes in both thermocouple legs,measurement errors up to 15 % are possible.

• Nickel-Chromium wire is also converted. The Iron and Copper in the structure are enriched and the Cobalt and Manganese depleted.

• Nickel- or Platinum wire experiences practically no changes.

• The insulation material of sheathed thermocouples experience a reduction of the insulation resistance. A continually increasing error is the result.

Impurities in the Alloys of Thermocouple Materials

In order for a thermocouple to generate thermal voltages, which are defined in the basicvalues in the standards, the composition of the alloys in the legs of the thermocouplemust conform exactly to the specifications. The thermal voltages generated by the ther-mocouple are very sensitive to minor changes in the alloy composition and therefore tothe presence of any traces of foreign materials. The thermal voltage reacts to the pres-ence of foreign materials to such a degree, that alloys which have been tested using aspectrum analyzer and found to have nominally the same composition (within the res-olution of the instrument) can consistently generate different thermal voltages.

The following table shows the effect of typical impurities on the thermal voltage of a wiremade of pure Platinum (purity > 99.99 %).

Tab. 3-23: Influence of impurities on the thermal voltage (dUth) of Platinum

Element dUth (µV/ppm)

Fe 2.30

Ni 0.50

Ir 0.35

Mn 0.32

Rh 0.20

Cu 0.12

Pd 0.07

Ag 0.03

Au -0.07

Pb 3.00

Cr 4.04

136

That a material is suitable for use as a thermocouple material is first apparent duringits calibration, after it has been used to manufacture a thermocouple. Foreign materialscan not only infiltrate during the production of the thermal material from the melt, butalso during manufacture or further processing of the thermal wire to the point, wherean originally “usable“ material can be turned into an “unusable“ one due to the presenceof foreign materials. The greatest changes in the wires of a thermocouple occur duringtheir actual operating period. These changes occur due to the infusion of foreign mate-rials, caused by contact with the materials contained in the ambient atmosphere. Themajor factor for accelerating the diffusion process is the temperature itself. The combi-nation of unfavorable installation conditions and high temperatures can result in the“poisoning“ of the thermal materials. This is particularly true for precious metal thermo-couples made of Platinum.

The Most Common Cause of Contamination:

• Pure materials, such as Copper, Iron and Platinum, experience aging effects prima-rily from the diffusion of foreign materials into them.

• Typical Platinum poisons are Silicon and Phosphorous, whose diffusion rate accel-erates above 1000 °C (1832 °F). It accelerates the effects due to the catalytic actionof the Platinum. Silicon quickly alloys with Platinum to form an eutectic, brittle alloy,which begins to melt at 1340 °C (2444 °F) and after a few minutes at the high tem-peratures can cause the thermocouple to fail. Here it is essential that only high purityAluminum oxide (Al2O3) be used for the insulation material, because it only containsvery small traces of Silicon.

• When using Pt-thermocouples the Rhodium slowly wanders over the weld area intothe Pt-leg and increases or displaces the measuring point. This leads to measure-ment errors, as soon as change reaches the area of the temperature gradient.

• For alloys such as CuNi, NiCr or PtRh start-up drifts may be observed which can beattributed to the relaxation of the stresses in the structure introduced during manu-facture. The drift effect continues to slow down, but it is never completely eliminated.

• For NiCr-alloys the diffusion of Sulfur is the most common, which diffuses into thegrain boundaries and destroys the material.

• NiCr-Ni thermocouples exhibit over longer time periods, relative to impurities, in com-parison, a smaller aging effect, because the individual legs drift in the same directioneffectively compensating the drift effect of the thermocouple (Fig. 3-60).

137

• Through the use of suitable ceramic and sheath materials for the mineral insulatedcables of the thermocouple Type K, a surface oxidation (intentional pre-aging) of thewires can be achieved. These protective oxide coatings can multiply the useful oper-ating period (Fig. 3-61).

Fig. 3-60: Typical aging of NiCr-Ni thermocouples at 1200 °C (2192 °F)

Fig. 3-61: Aging curves for Platinum thermocouples inside thermomwells containing SiO2 in reducing and oxidizing atmospheres

NiCr-Ni

NiCr

Ni

10 20

Operating timein hours

0.2

0

0.2

0.4

0.5

0.8

1.0

Thermomwell contains reducing Silicon Dioxide

Thermomwell contains oxidizing Silicon Dioxide

0 10 20 30 40 50

Pt

Pt 6%Rh

Pt 10%Rh

Pt 30%Rh

0.3

0.2

0.1

0.0

-0.3

Operating time in hours

The

rmoe

lect

r.ch

ange

s [m

V]

0 5 10 15 20

Pt 6%Rh*

Pt*

Pt 10%Rh*

Pt 30%Rh*

3

2

1

0

-0.5

Operating time in minutes

The

rmoe

lect

r.ch

ange

s [m

V]

* brittle

138

Tab. 3-24: Properties of ceramic insulation materials

Changes in the Thermal Voltages due to Mechanical Deformations of the Wire

When processing metallic materials for manufacturing thermocouples, it is important torecognize the effects that forming the materials has on the thermal forces. Many exten-sive investigations of this subject have been conducted in the past (Borelius, Tammanand Bandel). Thermal force differences exist between the hard drawn and soft an-nealed conditions of a thermocouple wire in an order of magnitude of approx. 1µV/K.This effect must be considered, especially for precious metal thermocouples, becausethe thermal forces are by their nature, small. For these thermocouples the effectsalready described can cause appreciable measurement errors. In other words, twistingthe wire may produce comparable effects.

If a thermocouple is made of wires in their hard drawn condition, (wires which were notsubjected to a recrystallization annealing), then during the operating life of the thermo-couple the thermal voltages will not be stable, which can be traced back to the slowtransition of the wire from a hard to a soft condition. When manufacturing thermo-couples, especially those made of Platinum thermocouple wire, it is imperative that thewire first be stabilized by annealing (soft-annealing).

Mechanical stresses in the thermocouple wire can cause disturbances in the crystallattice structure. Bending the wire over a sharp edge or repeated bending with a verysmall bending radius can lead to appreciable changes of the thermal voltages.

Properties

Material PortionAI2O3in %

Densityin g/cm3

Tempera-ture

changeresistance

Max.operating

temperaturein °C (°F)

Electricalresistancein Ω / cm

Alsint 99.71)3) 99.7 3.80...3.93 good 1700 (3092) 1014

Pythagoras 18001)3) 76 3.10 very good 1600 (2912) 1013

Pythagoras1)3) 60 2.60 good 1400 (2552) 1013

Silimantin 601) 73...75 2.35 very good 1350 (2462) No specs.

Degussit Al232)3) 99.5...99.7 3.7...3.95 good 1950 (3542) 1014 (RT)

Degussit Al242) 99.5...99.7 3.4...3.6 very good 1950 (3542) 107 (1000 °C (1832 °F))

Degussit Al252) 99.5...99.7 2.8...3.1 very good 1950 (3542) 104 (1500 °C (2732 °F))

1) Trade name of the company Haldenwanger2) Trade name of the company Friatec (previously Friedrichsfeld)3) Gas tight materials (all others are more or less porous)

139

Changing the Thermal Voltages due to Coarse Grain Formation

Metallic materials drawn down to fine wire sizes are subjected to accelerated grainboundary growth after longer exposure to higher temperatures. This growth leads tothe formation of larger and larger grains, so called coarse grain formation. in certaininstances this can result in the entire cross section of a thin wire consisting of only afew grains. This not only decidedly reduces the mechanical strength of the wire, butalso changes its thermal forces. This effect can be observed especially in the negativelegs of thermocouple Types R and S, which are made of unalloyed Platinum materials.It is for this reason that some manufacturers offer a Platinum thermocouple wire with afine grain quality. Special elements are alloyed into this material, which appreciably re-duce the grain boundary growth without affecting the thermal voltage.

Changes in the Insulation Resistance

A simplified circuit diagram for a temperature sensor includes a signal source and anetwork of serial and parallel resistors (Fig. 3-62). The serial resistors in a real temper-ature sensor are made up of the resistors in the connection leads and the resistance atthe connection terminals or plug contacts. The parallel resistors result from the non-ide-al behavior of the insulation materials, which are used to electrically insulate the cableand connection wires from each other in the measuring inset.

Fig. 3-62: Simplified electrical circuit diagram for a thermocouple

RL1.2 RL1.1

RL2.2 RL2.1

EthUth

Rins

Eth parasitic

RL = Connection lead resistanceRins = Insulation resistance

140

When using thermocouples the changing series (connection leads) resistances playonly a subordinate role in the aging processes, as long as they are not subjected to acontinuous mechanical wire connection, which could completely disable the thermo-couple due to lead breakage. A decrease in the insulation resistance however canresult in appreciable errors in the output signal of the thermocouple.

A reduction in the insulation resistance may have a number of causes.

• In simple thermocouples, made using insulated thermocouple wires, the insulationproperties of the wire insulation can be permanently damaged by a single exposureto an excessive temperature and made useless.

• For thermocouples, which are designed as measuring insets using a mineral insu-lated cable, the insulation capability of the insulating ceramic (Al2O3 or MgO) can bestrongly limited by moisture absorbed or bound in the ceramic material.

Moisture can enter undetected during the manufacture of the product, e.g. if the mineralinsulated cable is exposed for a longer period of time with unprotected ends to the nor-mal humidity in the air. The ceramic materials used are extremely hygroscopic, andbind in the moisture as crystal water. Moisture can also be absorbed by a thermocoupleduring use if it is mechanically damaged. In addition, the insulation properties declinesharply for these materials at higher temperatures (approx. one order of magnitude/100 K), so that for temperatures in the range from 1000 °C (1832 °F) and above, theactual reason for using the insulation no longer exists.

This is caused, at higher temperatures, by the increase in the ionic and electron con-ductivities of all ceramic insulation materials. A marked decrease in the insulationresistance, will without fail, cause electrical shunt currents to flow between the legs ofthe thermocouple, loading the signal source and causing erroneous thermal voltagesignals.

141

Even more critical are the so called secondary measuring locations. These form whenboth thermocouple legs, due to a decrease in the insulation resistance, are electricallyconnected together anywhere within the temperature sensor creating an additional(secondary) measuring location. The output signal of the thermocouple is now a com-bination of the different thermal voltages which are generated at the various measuringlocations. The danger presented by these secondary measuring locations occurs whenpart of the thermocouple is located in areas where the temperature is higher that at themeasuring location itself (steam boiler tubes in large power plants, brick lining at thebottom of industrial ovens).

The electric insulation capability is naturally not only a function of the insulation materialused but also of the geometry (diameter and length) of the thermocouple itself. Espe-cially for very long thermocouples, e.g. in large power plants, it is difficult to achievehigh insulation resistance. For applications with temperatures over 1000 °C (1832 °F)the use of thermocouples made with mineral insulated cables can only be recommend-ed with very limiting restrictions. For these applications, the use of thermocouplesdesigned using conventional technology (pipe designs) are to be recommended. Theinsulation values of the ceramic bodies used in this design are an order of magnitudehigher than those of the softer ceramic of the mineral insulated materials. This is dueprimarily to the differing degrees of compression of the materials.

Fig. 3-63: Relationship of the insulation resistance of mineral insulated cablesto the operating temperature

1000

1

10

100

0,01

0,1

900 1000800

Temperature t [° C]

R[k

Ohm

]in

s

1100 1200 1300

MgO

Al O2 3

142

3.5.2 Drift Mechanisms for Resistance Thermometers

The effect of impurities on the temperature coefficient of Pt-resistor materials

As already mentioned, the purity of the mandatory alloy compositions is an essentialrequirement for the thermal materials. The Platinum resistance wire for the manufac-ture of Platinum measuring resistors is no exception.

A rough differentiation can be made between application categories:

• For the manufacture of temperature sensors, in order for the requirements in ITS 90to be satisfied, Platinum with pure quality is required. Temperature sensors of thistype are used as definition and interpolation instruments for determining the Inter-national Temperature Scale between the fixed points in the temperature range from-189 °C (-308.2 °F) (N2-Point) to 961 °C (1761.8 °F) (Ag-Point).

• For resistance thermometers, as they are defined in EN 60751, physically pure Plat-inum is used, which, as a result of the addition of specific elements to the alloy, are“set“ to the required temperature coefficient α.

For its temperature coefficient (which corresponds to the linearized temperaturedependence of the material in the temperature range between 0...100 °C (32...212 °F))the value 3.8506 x 10-3 K-1 can be calculated from the basic values in EN 60751.

Impurities, which may contaminate the Platinum during manufacture or during theoperating period of the temperature sensor, can change the chemical composition ofthe material and thereby its temperature coefficient. The result is a deviation from thebasic values in the standard. The Platinum resistance wire will be gradually “poisoned“.The sensor drifts.

A typical problem, which also leads to the poisoning of the Platinum resistance wire, isthe absorption of foreign materials from the thermomwell material, or from the sheathmaterials used for the mineral insulated cables. This absorption process is practicallynonexistent or extremely slow at lower temperatures, but it accelerates dramatically athigher temperatures. For this reason, metallic thermomwells made of stainless steelshould not be used when long term temperature exposure over approx. 420 °C(788 °F) is anticipated. For long term use above that temperature, thermomwell mate-rials such as quartz glass, high purity ceramic or mineral insulated cables with a Plati-num sheath should be used.

143

A typical indication that the resistance material is aging, which can be attributed topoisoning, is an increase in the Ro-value, accompanied by a decrease in the α-value.

The following table demonstrates the effects of impurities on the α-value for physicallypure Platinum.

Tab. 3-25: Effects of contamination on the temperature coefficient (α) of Platinum

Drift effects due to mechanical stresses in the sensor element during operation

Not only changes in the chemical composition of the resistor material due to contami-nation by foreign elements can cause instability in the temperature sensor, but also thepresence of mechanical stresses in the sensor element or in the total assembly canlead to changes of the resistance values. Continuous mechanical vibrations, especiallywhen combined with high operating temperatures, affect the temperature sensor sig-nificantly. There are two effects which can be initiated by the stresses described in thefollowing.

In wire wound resistors, which are not solidly positioned in the carrier body for vibrationresistant, short circuits between the individual windings can occur causing step changereductions in the Ro-resistance value.

The fine wire in the sensor element can be elongated at the connection point by strongvibration loads causing a reduction in the wire cross section. In an extreme case thefine wire can break off. A comparable effect can occur if the resistance thermometer isexposed to continuous large temperature changes and a temperature change resistantdesign was not used. In such applications, the sensor element, if the fit is too tight, ex-periences continuous tension and compression forces (alternating stresses) in the con-nection wires due to the different thermal expansions of the materials.

Element dα (ppm-1)Fe -1.28 x 10-6

Ni -0.16 x 10-6

Ir -0.20 x 10-6

Mn -0.21 x 10-6

Rh -0.09 x 10-6

Cu -0.35 x 10-6

Pd -0.10 x 10-6

Ag -0.15 x 10-6

Au -0.07 x 10-6

Pb -0.90 x 10-6

Cr -3.25 x 10-6

144

Changes in the connection lead resistance

In resistance thermometers using a 2-wire configuration, the connection lead resis-tance is a direct component of the measured value. To correct the measured resistancevalue to its actual temperature dependent value, the connection lead resistance isusually specified so it can utilized by the user to correct the value measured. The con-nection lead resistance can be accounted by the manufacturer by using a resistor withsmaller resistance value (negative actual value deviation from reference value).

If during the course of operation of the temperature sensor the resistance of theconnection leads change (e.g. due to a cross section reduction of the wires, oxidationat the connection locations, etc.), then the deviation of the measured values appear asa drift, which often goes unnoticed. For resistance thermometers connected in 3- and4-wire configurations this effect is automatically compensated.

Tab. 3-26: Measurement error due to connection lead resistance

Tab. 3-27: Wire resistance of Cu-mineral insulated cables at room temperature

MaterialR20

d = 0.6 mm(0.024”)

Rt/Roat 400 °C (752 °F)

Measurement error at 400 °C (752 °F)

for d = 0.6 mm (0.024”)length = 1 m (39”)

in Ω/m uncompensated compensated

Cu 0.06 2.75 0.48 K 0.3 K

Ag 0.06 2.70 0.47 K 0.29 K

NiCr 2.48 1.086 7.8 K 0.62 K

CuNi 1.77 0.996 5.1 K 0.02 K

Wirematerial

Outside diameter din mm (inch)

Number of conductors

R/Iin Ω/m

Cu 3 (0.118) 2 0.111

Cu 3 (0.118) 4 0.107

Cu 4.5 (0.177) 4 0.045

Cu 6 (0.236) 2 0.027

Cu 6 (0.236) 4 0.027

Cu 6 (0.236) 6 0.052

145

Changes in the insulation resistances

The design of resistance thermometers is essentially comparable to thermocoupledesigns. Comparable materials are also used. The electric insulation capabilities of theinsulation materials can change in the application range of the resistance thermometerfor a number of reasons. A change causes parasitic short circuits to be created, whichact as resistors in parallel with the actual sensor resistance as shown in the circuitdiagram below. Electrically they act as voltage dividers.

Fig. 3-64: Electrical circuit diagram for a real resistance thermometer

The resultant shunt current causes a lower, incorrect measurement signal. The effectof “poor“ insulation resistance increases for higher nominal resistances of the sensor(e.g. Pt1000 Ω). For resistance thermometers, which are to be used at high tem-perature, in certain instances it is better to avoid using resistance thermometers withRo-resistance values of 25 Ω or 10 Ω.

RL1.2 RL1.1

RL2.2 RL2.1

Rins RSRWth

RL = Connection lead resistanceRins = Insulation resistanceRs = Sensor resistance

146

Fig. 3-65: Relative negative measurement error caused by a parallel resistance, due to non-optimal insulation.

At this point it should be stressed, that a regular periodic check of the insulation resis-tance during the operating life of the resistance thermometer is one of the most impor-tant quality assurance measures which can be conducted. Especially since themeasurement of Rins requires minimal expense and can be made under actual instal-lation conditions. The requirements according to EN 60751 relative to the insulationresistance limits should, in reality, only be considered as minimal requirements. Adecrease in the insulation resistance can also indicate a tear in the insulation, throughwhich not only moisture but also other contaminants could penetrate changing theresistance thermometer curves.

R = 1000 Ohm0

R = 100 Ohm0

R = 10 Ohm0

1.0E+02

1.0E+02 1.0E+04 1.0E+06

1.0E+01

1.0E+00

1.0E+00

1.0E-01

1.0E-02

1.0E-02

1.0E-03

1.0E-04

1.0E-05

1.0E-06

Relative Negative Measurement Error (%)

Parallel Resistance (kOhm)

147

3.6 Possible Errors and Corrective Measures

General

In this Chapter the most common sources of errors and measures for their correctionare presented. The list does not claim to be complete. The details relate only to the tem-perature sensors and their leads. Any instruments connected for processing the signalswill only be included if they provide feedback about the operation of the temperaturesensor.

Quick checks of the thermocouples (TC) and resistance thermometers (RTD) and their measurement circuits in the installed condition

• Required test instruments:Portable multimeter with mV and Ω ranges, insulation tester with 60...100 V = volt-age; all measurements are made at room temperature.

• At room temperature the continuity and insulation are tested; use “knocking“ to detectwire breaks.

• A TC, under certain circumstances, can probably be considered to be acceptable ifR < 20 Ω (wire > 0.5 mm (0.020”) Ø); the value is a function of the wire diameter andlength Rins ≥ 100 MΩ (for an insulated TC).

• A RTD is also probably acceptable if R ≈ 110 Ω (for Pt100) Rins ≥ 100 MΩ.

Heating a TC or RTD, e.g., with a gas flame to approx. 200...400 °C (392...752 °F)(without a controlled temperature) will provide information regarding breaks, reversedpolarity (for a TC), too low insulation resistance, etc.

Testing in the installed condition

• Additional instruments required:mV-source, resistance decade or a commercially available Pt100-simulator

• TC: Disconnect connection leads; use the mV-source to inject voltages into the mea-suring circuit and check indication. Test determines whether the TC or the connectedmeasuring circuit is in error.

• RTD: Disconnect connection leads at thermometer; connect the resistance decadeand simulate the measurement resistance and check indication. Test determineswhether the RTD or the connected measuring circuit is in error.

• Additional tests were described in the previous section.

If the TC or RTD has a exchangeable measuring inset, replace the inset with a testmeasuring inset with known values. Test determines whether the temperatures sensoror another component in the measuring circuit is the cause of the measurement error.

148

Error Table for Thermocouples and Resistance Thermometers

Error Probable orpossible causes

Corrective measures

Measured signal disturbances (no stable indication)

a) Electrical/magnetic interference

– Install galvanically isolated transmitter– Maintain a distance of least 0.5m (20”)

between signal and power leads when installed in parallel

– Use electrostatic shielding by installing a grounded foil/screen

– Use twist lead (pairs) to eliminate mag-netic coupling

– Cross signal and interfering power leads in right angel

b) Ground loops – Only one ground point in measuring circuit or measuring system “floating“(not grounded)

c) Decrease of theinsulation resistance

– Exchange measuring inset– Dry thermometer/measuring inset,

suspect moisture absorption;remove and reseal (only possible by manufacturer)

Temperature sensorresponds too slowly(response time),Indication in error

a) Incorrect installation– in flow shadow– affected by an inter-

fering heat source

– Select installation site so the medium can transfer its temperature undisturbed to the temperature sensor and eliminate the influence of an interfering heat source

b) Incorrect installation– insertion length too

short– poor heat coupling

– too high heat losse.g. through exten-sion tube

– Insertion length of thermal element should be at least + 5 x d (liquids) up to 20 x d (gases) (d = thermowell outside diameter)

– Assure good heat contact, especially for surface measurements, by using appro-priate contact surfaces and/or heat con-ductive materials (e.g. heat conductive paste, grind surface)

– Reduce effect by suitable insulation

c) Thermowell too thick – Use the smallest technically capable thermowell; response time isproportional to the first power of the cross section or volume of the tempera-tur sensor, dependent on the heat trans-fer coefficient and air gaps in the as-sembly. Fill the latter with contact materials (oil, grease if possible)

d) Deposits on the thermowell (it has athermally insulating effect)

– During inspection, remove– If possible, select a different thermowell,

or another installation location

149

Continuation: Error Table for Thermocouples and Resistance Thermometers

Error Probable orpossible cause

Corrective measures

Break in the temperature sensor

a) Vibrations – Stronger springs for measuring inset– Shorten insertion length– Move measuring location (if possible)– Specially designed measuring inset

and thermowell

b) Thermal shock – Select a temperature change resistantsensor design

Very corroded, abraded or eroded thermowell

– Incorrect thermowell material selected

– Analyze defective thermowell andselect a more suitable material;provide supplementary surface protection (e.g. armoring or eccentrically drilled thermowell, impact rod)

150

Error Table Specifically for Thermocouples

Error Probable orpossible cause

Corrective measures

Temperature indica-tion too low with a very thin thermo-couple

– Instrument with a low input or internal resistance, high lead resistance

– Adjust leads– Select an instrument with a higher input

resistance

Varying temperature indication with other-wise proper operation

– Reference junction temperature or electric simulation not constant(thermal/electricalreference junction)

– Reference junction temperature orreference junction simulation must be maintained constant

Temperature indica-tion error increases with increasing temperatures(indication too low)

– Decreasing insulation resistance (acts as a shunt path, decreases EMF of the thermo-couple)

– Recommended insulation resistance– at 20 °C (68 °F) ≥ 100 MΩ, – at 500 °C (930 °F) ≥ 2 MΩ– Exchange thermocouple measuring

inset, then seal against moisture

Large deviations of the temperature indication from the values in the tables

– Parasitic voltages(thermal voltages,galvanic voltages)

– Incorrect materialcombinations

– Incorrect linearization applied

– Poor electrical contact

– Check thermocouple and leads,exchange if necessary

Large deviations of the temperature indication from the values in the tables

– Incorrect compensating cables or their polarity is reversed

– Check if the correct compensating cable has the correct polarity

– If a compensating cable is used:Temperature of connection terminals max. 200 °C [392 °F).Same temperature of connection terminals at > 100 °C [212 °F]

Indication changes over the course of time

– Chemical effects on the thermocouple especially at higher temperatures

– Exchange defective thermometer,possibly by a suitable thermocouple (e.g. Green rot in Type K → replace with Type N)

– The measuring location wanders with the “healthy“ material into cooler regions, possibly insert thermocouple deeper, install air purge (O2-addition)

– Thermal aging of the thermocouple

– Select larger wire size in order to slow down the aging process

– Generally an aged thermocouple indicates lower temperatures than a new one.

– Check critical measuring locations regularly

– Regular recalibrations

151

Continuation: Error Table Specifically for Thermocouples

Error Probable orpossible cause

Corrective measures

Indicating instrument shows room tempera-ture (reference junction in instrument)

– Lead break – Check continuity

Negative temperature indication

– Incorrect polarity at thermocouple

– Reverse thermocouple polarity

Indication in error by 20...25 °C (68...77 °F)

– Thermocouple Type L linearized as Type J or reverse

– Correct linearization

Indication even though temperature sensor disconnected

– Pick up on the compen-sation cable due to electromagnetic noise

– Parasitic galvanicvoltage (adjacent meter location) due to moisture in the compensation cable

– Dry compensation cable

152

Error Table Specifically for Resistance Thermometers

Error Probable orpossible cause

Corrective measures

Temperature indica-tion generally too high

– Non-negligible lead resistances too high,Not compensated

If still possible:– Install larger wire size cables– Compensate leads– Use sensor head transmitters– Convert to 3- or 4-wire circuits– Reduce connection lead lengths

– Self heating by measur-ing current too high

– Use a smaller measuring current(recommended 1 mA)

Temperature indica-tion changes with changing ambient temperatures

– Thermometer in2-wire circuit; the connection leads are subjected to large a temperature change

– Convert to 3-wire circuit, which essentially eliminates the ambient temperature effects

– Convert to a 4-wire circuit(Connection lead resistance effectscompletely eliminated)

Temperature indica-tion error increases with increasing temperature(indication too low)

– Decreasing insulation resistance, acts as a shunt path for the measured signal

– Rins approx. 0.1 MΩ in parallel with100 Ω gives an error of the same magnitude as Tolerance Class BRecommended:Rins at 20 °C ( 68 °F): ≥ 100 MΩRins at 500 °C (930 °F): ≥ 2 MΩ(Minimum requirements per EN 60751)

– Exchange defective thermometer

Deviations of the tem-perature indication from the values in the tables (parasiticand galvanic EMF’s)

– Poor lead material, contamination, moisture

– Temperature differencebetween the terminals of the connection leads

– Corrosion at the connection terminals in the connection head

– Check installation– Thermally insulate terminals

(same temperature)

Indication changes over the course of time

– Thermal aging(Drift of the measuring resistor)

– Select suitable high temperature design– Recalibrate regularly– Exchange if necessary

153

4 Non-Contacting Temperature Measurements in Field Usage

4.1 Advantages and Uses for Applying Infrared Measuring Technology

Complementing the classical, contacting temperature measurements using thermo-couples and resistance thermometers, more and more applications are making temper-ature measurements using non-contacting infrared-thermometers.

The infrared measuring technology is not a new discovery – it has been utilized inindustry and research for decades – but only recently have innovations reduced thecosts, increased the reliability and appreciably reduced the size of the sensor. All thesefactors have aroused the interest of new user groups and application areas.

Advantages of the non-contacting temperature measurement

• Fast measuring method in the ms-range (saves time) or increases in the number ofconsecutive measurements which can be made in a given time interval, higherinformation rate (e.g. temperature field distribution measurements).

• Measurements on moving objects possible (conveyer processes, rolling mills, etc.).

• Measurements in dangerous or inaccessible locations (objects at high voltage, long distance measurements).

• High measuring temperatures above 1300 °C (2372 °F) are not a problem. In suchapplications, contacting thermometers have a limited life span.

• No reaction on the object, i.e. no energy is removed from the measured object.Especially suitable for poor heat conductors such as plastics and wood, a highermeasuring accuracy than with contacting thermometers plus elimination of the falsemeasuring values.

• No mechanical influences on the surface. Therefore wear free, e.g. painted surfacesare not marred and measurements are possible on soft surfaces (foams, elas-tomers). Contaminations, especially in hygienic applications, are excluded.

154

Having mentioned a number of advantages, the question remains, what must be con-sidered when applying infrared-thermometers:

– The object must by optically visible to theinfrared-thermometer. Large amounts of dust or smoke affect the measurement as well as solid obstructions, e.g. mea-surements cannot be made inside closed metal reaction vessels.

– The optics in the measuring head must be protected from dust and condensing liquids.

– Only surface temperature measurements can be made, while the different radia-tion properties of different material surfaces must be considered.

Summary: The main advantages are fast response, no reaction on the measuredobject and a very large temperature range up to 3000 °C (5432 °F).

4.2 Fundamentals and Operation

An infrared-thermometer can be compared to the human eye. The lens of the eye is theoptic, through which the radiation from the object reaches the light sensitive layer, theretina. There the signal is converted and conducted to the brain. In an infraredthermometer, the lens is responsible for the thermal radiation from the object reachingthe radiation sensitive sensor, where the radiation is converted into a useful electricalvoltage.

Fig. 4-1: Design principle of an infrared measuring (IR) system

Thermal radiationElectronic boardwith μ-ProcessorLens IR-Detector

Microstructurethermocouple

IR-Thermal voltage

Reference temperature

155

4.2.1 Physics of Thermal Radiations

Every body with a temperature (T) above absolute zero, emits, as a function of its tem-perature, infra red radiation, so called self radiation. It is the result of internal molecularmovements. The intensity of these movements is a function of the temperature of thebody. Since the molecular movement simultaneously produces charge motions, anelectromagnetic radiation (Photon particles) is emitted. These Photons move at thespeed of light and behave according to the known Laws of Optics. They can be deflect-ed and focused using lenses or reflected using mirrored surfaces. The spectrum of thisthermal radiation extends from 0.7 to approx.1000 µm wavelengths. This range is notvisible to the human eye, because it is above the red range of visible light. It is know bythe Latin, “infra"-red.

Fig. 4-2: The electromagnetic spectrum, with the usable infrared range

As mentioned previously, all bodies emit this radiation. In Fig. 4-3 typical radiationcurves for a body at various temperatures are shown. One can see, that hot bodies notonly emit radiation in the above described infrared range (> 0.7 µm), but a portion ofthe spectrum lies in the visible range. This is the reason why people can see very hotobjects (over 600 °C (1112 °F)) as red hot to white hot. Experienced steel workers canestimate fairly well the temperature of the hot metal by its color.

The classic Disappearing Filament Pyrometer has been used in the steel and ironindustry since 1930 as a functional measuring system. In Fig. 4-3 one can also see,that the point of maximum radiation shifts to shorter wavelengths as the temperature ofthe object increases and that the curves for a body at various temperatures do notcross each other.

Light

Used infrared range: 0.7...14 μm

Wavelength in μm

Wavelength (μm)

156

These relationships were recognized by the physicists Stefan and Boltzmann in 1879and indicated that a unique temperature determination of the measured object can bemade based on its radiation curve.

Fig. 4-3: Blackbody radiation curve as a function of the temperature

Infrared measuring technology is based on this knowledge. As can be seen in Fig. 4-3,the goal is to design an infrared thermometer so that as much of the energy as possible(corresponds to the area under the curve) or the signal from an object can be used forthe evaluations. At higher temperatures this is possible using a narrow wavelengthrange, at lower ranges the energy of a larger spectrum ranges (e.g. 7...14 µm) is used.

An additional reason for using instruments with different wavelength ranges, is due tothe radiation characteristics of some materials, e.g., those with so called non-graybodyradiation (glass, metals and plastic foils). Fig. 4-3 shows curves for ideal blackbodyradiation. Many bodies emit less radiation at the same temperature. The relationship ofthe real radiation value to blackbody radiation is known as the emissivity e, which hasa maximum value of 1 (body corresponds to an ideal blackbody) and a minimum valueof 0. Bodies, whose emissivity value is less than 1, are called graybody radiators.Bodies whose emissivity value is also a function of the temperature and wavelength,are called non-graybody radiators.

157

Viewed physically, the Conservation of Energy law applies, and therefore the sum ofthe radiation made up of the absorption (A), reflection (R) and transmission (T) equals"one" (see Equation 1 and Fig. 4-4).

Fig. 4-4: Real graybody radiator

Solid bodies do not have any transmission in the infrared range (T = 0). ThereforeEquation 1 becomes for the absorption and also for the emission:

Ideal blackbody radiators have no reflection (R = 0), so that E = 1. Many non-metallicbodies, e.g. wood, plastic, rubber, organic materials, stone or concrete surfaces onlyreflect minimally and therefore have high emissivity values between ε 0.8 and ε 0.95.Metals on the other hand, especially polished and shiny surfaces, have emissivityvalues of approx. ε 0.1. These conditions are taken into account by the infrared thermo-meters by their ability set a selected emissivity factor, see also Fig. 4-5.

(1)

(2)

A R T 1=+ +

A

TE

RI

Object

Thermal source

Thermal source

Sensor

I = Incoming radiationR = Reflected radiationT = Transmitted radiationE = Emitted radiationA = Absorbed energy portion

A E⇔ 1 R–=

158

Fig. 4-5: Specific emissions for various emissivity values

4.2.2 Determining the Emissivity Values

Whether an object is a solid body, a liquid or a gas, it is individual and specific for aninfrared sensor. The reasons are its specific material and surface conditions. There area variety of methods which can be used to determine their effects on the emissivityvalue. The emissivity value can be determined from a table listing the emissivity valuesfor commonly used materials. Emissivity value tables are also a help in selecting thecorrect instrument by listing the appropriate wavelength ranges. The table values,especially for metals, should only be used for orientation, because the surface condi-tion (e.g. polished, oxidized or scaled) can affect the emissivity value more than thetype of metal itself. There are also methods for determining the emissivity value for aspecial material. A pyrometer with an emissivity value setting can be used.

1. A sample of the material is heated to a known temperature, which can be measuredvery accurately using a contacting thermometer (e. g. thermocouple). The tempera-ture of the object is then measured with an infrared thermometer. The emissivityvalue is then changed until the temperature value corresponds to the temperaturemeasured using the contacting thermometer. This emissivity value can then be usedfor all subsequent measurements of objects made from the same material.

2. For relatively low temperatures (up to 260 °C (500 °F)) special plastic labels with anadhesive backing and with a known emissivity values are attached to the object tobe measured and the temperature of the label measured using an infrared thermom-eter set to an emissivity value ε = 0.95. The surface of the object is then measuredwithout the label and the emissivity value changed until the correct temperaturevalue is indicated. The emissivity value determined in this manner can then be usedfor all subsequent measurements of objects made from the same material.

ε = 1.0 (Blackbody radiator)

ε = 0.9 (Graybody radiator)

ε varies with wavelength(Non-graybody radiator)

Spe

cific

Em

issi

on

159

3. A blackbody radiator is manufactured using a test body made of the material to bemeasured. A hole is drilled into the object. The depth of the hole should be at least5 times diameter of the hole. The diameter must correspond to the diameter of thetarget area of the instrument being used. If the emissivity value of the inside walls isgreater than 0.5, then the emissivity value of the cavity radiator is approx. 1 and thetemperature measured in the hole is the correct temperature for the measuredobject. If the infrared thermometer is now pointed at the surface of the object, theemissivity value can be changed until the temperature indication agrees with the val-ue previously determined using the blackbody radiator. The emissivity value deter-mined in this manner can then be used for all subsequent measurements of objectsmade from the same material.

4. If the measured object can be coated, a matte black color is applied, for which anemissivity value of about 0.95 is specified. The temperature of this blackbody radia-tor is measured, and then subsequently the emissivity value is adjusted as de-scribed above for measurements made on the uncoated object.

4.2.3 Measuring Temperatures of Metals

The emissivity value of metals is a function of the wavelength and the temperature.Since metals often reflect, they have a tendency to have lower emissivity values, whichcould result in variable and unreliable measurements. In such applications, select aninstrument which measures the infrared radiation at a specific wavelength and over aspecific temperature range, at which the metal has the highest emissivity value, if pos-sible. For many metals the measurement error increases with the wavelength, so theshortest possible wavelength for the measurement should be used, see Fig. 4-6.

Fig. 4-6: Measurement error for an emissivity value misadjusted by 10 % as a function of the wavelength and object temperature

Mea

sure

men

t E

rro

r [%

]

Object temperature [°C]

160

The optimal wavelengths for measuring high temperatures of metals is betweenapprox. 0.8...1.0 µm at the limit of the visible range. Wavelengths of 1.6, 2.2 and3.9 µm might also be used.

4.2.4 Measuring Temperatures of Plastics

Many plastics are by nature clear and transparent to human eyes, as well as to infraredradiation. The transmission ranges for plastic foils varies with the wavelength and isproportional to the thickness. The transmission is higher in thin materials than in thickermaterials. For optimal temperature measurements of such foils, it is important to selecta wavelength at which the transmission value is near zero. Certain plastics (Polyethyl-ene, Polypropylene, Nylon and Polystyrene) are opaque at 3.43 µm, others (Polyester,Polyurethane, Teflon, FEP and Polyamide) at 7.9 µm. For thicker (> 0.4 mm (0.016“))or heavily pigmented foils, wavelengths between 8 and 14 µm should be selected.

If uncertainty still exists, it is advisable to submit a sample of the plastic to the manu-facturer of the infrared-thermometer to determine the optimal spectral bandwidth. Thereflection value for practically all plastics is between 5 % and 10 % (ε = 0.9...0.95).

Fig. 4-7: Spectral transmissivity of Polyethylene and Polyester plastic foils

Independent of the thickness, Polyethylene is essentially opaque at a wavelength of3.43 µm and Polyester is completely opaque at a wavelength of 7.9 µm.

Polyethylene

Polyester

0.03 mm (0.0012“) thick

0.03 mm (0.0012“) thick

0.13 mm (0.005”) thick

0.25 mm (0.010“) thick

Wavelengths [μm]

Wavelengths [μm]

Tra

nsm

issi

vity

[%]

Tra

nsm

issi

vity

[%]

161

4.2.5 Measuring Temperatures of Glass

When an infrared thermometer is used to measure the temperature of glass, both thereflection and transmission must be considered. By a careful selection of the wave-lengths, it is possible, to not only measure the surface temperature of glass, but alsotemperatures within the glass. For temperature measurements below the surface, asensor for wavelengths 1.0, 2.2 or 3.9 µm should be used. For surface temperaturemeasurements a sensor with a wavelength of 5 µm is recommended. For low temper-atures, 8...14 µm should be used with the emissivity set to 0.85.

Summary:All bodies emit infrared radiation, which is only visible to human eyes above600 °C (1112 °F) (e. g. glowing iron). The wavelength range extends from 0.7 µmto 1000 µm. Blackbody radiators absorb or emit 100 % of the radiation that cor-responds to their temperature. The radiation of all other bodies is ratioed to theblackbody. This ratio is called the emissivity value.

162

4.3 A Typical Infrared Measuring Site

4.3.1 The Measuring Path

Fig. 4-8: Typical infrared measuring site

Normally, atmospheric air fills the measuring path between the detector and measuredobject, whose transmission characteristics must be considered if a reliable measure-ment is to be assured. Atmospheric components such as water vapor or carbon dioxideabsorb infrared radiation of certain wavelengths resulting in transmission losses. Ifthese absorption components are ignored, the temperature which will be indicated, incertain instances, will be lower that the actual temperature of the object. Fortunatelythere are “windows“ in the infrared spectrum which do not contain these absorptionwavelengths. In Fig. 4-9 the transmission curve of a 1 m long air path is shown. Typicalmeasuring windows in which infrared radiation passes essentially unimpeded are1.1...1.7 µm, 2...2.5 µm, 3...5 µm and 8...14 µm. For this reason, commercially avail-able infrared thermometers utilize these wavelengths for evaluating the signals.

Measuredobject

Heatsource

Measured spot

163

Fig. 4-9: Transmissivity of a 1 m (39”) long air path at 32 °C (90 °F) and rel. humidity 75 %

Additional effects such as dust, smoke and suspended matter could contaminate theoptics and lead to incorrect measurements. To prevent particles from adhering, an airstream accessory is offered. It usually has threaded adaptors and a compressed airconnection. The air stream assures a positive pressure in front of the optics preventingparticles from reaching the optics. If during the measuring process, large quantities ofdust or smoke are present which are affecting the measurements, quotient pyrometersshould be used.

Wavelength [μm]

Tra

nsm

issi

vity

[%]

164

4.3.2 Stray Radiation and High Ambient Temperatures

Also thermal radiation sources in the vicinity of the measured object must be consid-ered. It might be possible that temperature measurements of metal pieces in an indus-trial furnace might be affected by the higher temperature of the furnace walls. Thisinfluence of the ambient temperature on the measured value is taken into account bya special compensation. Otherwise, the temperature value indicated for the measuredobject would be too high. A correctly set emissivity value in conjunction with an auto-matic ambient temperature compensation assure an accurate temperature measure-ment.

Fig. 4-10: Ambient radiation source effects on the measured temperature

Infrared sensors are electronic components with a somewhat sensitive nature. Theycan only operate within specific operating temperature ranges. For some sensors theupper limit is 85 °C (185 °F). Above the allowable operating temperature air or watercooling must be used and a special cable suitable for high temperature applicationsmust be provided. When using water cooling, it is often desirable to also install the airstream accessory to prevent condensation on the optics.

Measured object

Ambient radiation

165

4.3.3 Optic Radiation Input, Protection Glass and Window Materials

The optic system of an infrared thermometer catches the infrared radiation energy emit-ted by a circular measured point area and focuses it on the detector.

Care must be exercised to assure that the measured point area is completed filled.Otherwise the infrared-thermometer will also “see“ thermal radiation from the back-ground, causing a measurement error.

Fig. 4-11: Measured point size effects

Optical resolution is defined as the ratio of the distance between the measuring instru-ment and the measured object to the measured point diameter. The larger this valuethe better the instrument and the smaller the measuring object can be for a specificdistance.

Fig. 4-12: a) High performance optics combined with crosslaser sighting for more precisionb) Close focus lens with a spot size of 1 mm and laser sighting for measurement ofsmallest structures

The optics can either be a mirror optic or a lens optic. Lenses, dependent on theirmaterial, can only be used for certain wavelength ranges, but because of designconsiderations, are the preferred solution.

Very good Good Bad

Object and measured point are the same size

Infrared-sensor

Object larger thanmeasured point

Object smaller thanmeasured point

a) b)

166

Latest Trends in Sighting Techniques

New principles of measurement and sighting techniques facilitate an improved and pre-cise use of infrared thermometers. Developments field of solid state lasers are adaptedfor multiple laser arrangements to mark the spot sizes. Thus, the real spot sizes insidethe object field are denoted with the help of laser crosshairs techniques. Different prod-ucts use video camera chips instead of optical sighting systems.

Development of High-Performance Optics combined with Laser Crosshairs Techniques

Simple, cost-effective portable infrared thermometers use single point laser aimers inorder to distinguish the centre of the spot with a parallax default. With that techniquethe user has to estimate the spot size with the help of the spot size diagram and thelikewise estimated measuring distance. If the measuring object takes only a part of themeasuring spot, temperature rises are only displayed as average value of hot area andambient cold area. A higher resistance of an electric connection due to a corroded con-tact results in an unduly heating. Due to small objects and inappropriate big spot sizes,this rise will be shown as a minor heating, only: Thus, potentially dangerous heatingsmay not be recognized in time. In order to display spots in their real size, optical sight-ing systems with a size marking were developed.

They allow an exact targeting. As laser pyrometers are significantly easier and saferthan contact thermometers, engineers have tried to mark the spot size with laser sight-ing techniques independently from the distance – according to the distance-spot-size-ratio in the diagram. Two warped laser beams approximately show the narrowing of themeasuring beam and its broadening in longer distances. The diameter of the spot sizeis indicated by two spots on the outer circumference. Due to the design the angleposition of these laser points on the circuit alternates which makes an aiming difficult.

The Principle of the Crosshairs

New laser sighting techniques support to denote measuring spots of infrared thermom-eters as real-size crosshairs, exactly matching the measuring spot in their dimension.Four laser diodes are arranged in symmetrical order around the infrared optical mea-suring channel. They are connected to line generators, which create a line of definedlength inside the focus distance. The line generators, arranged in pairs, face each oth-er. They overlap the projected laser lines at the focus. That way crosshairs are gener-ated, which exactly display the diameter of the measuring spot. At longer or shorter dis-tances the overlapping is only partly. Thus the user has a changed line length and withthis changed measuring crosshairs. With the help of this technology the precise dimen-sions of a measuring spot can be denoted for the first time. This development improvesthe practical use of products with good optical performance.

167

Protection Glass and Window Materials

For measurements in closed reaction vessels, furnaces or vacuum chambers, it is usu-ally necessary to measure through an appropriate measuring window. When selectinga window material make certain that the transmission value of the window is compatiblewith the spectral sensitivity of the sensor. At higher temperatures, quartz glass is usu-ally the material of choice. At lower temperatures in the 8...14 µm band the use ofspecial infrared transparent materials such as Germanium, Amtir glass or Zinc seleniteare required.

In addition to the spectral sensitivity, other parameters should be considered whenselecting the window material, such as the diameter of the window, temperaturerequirements, maximum pressure differential across window, ambient conditions aswell as the capability of maintaining both sides clean. Just as important a factor is thetransparency in the visual range in order to better aim the instrument at the measuredobject (e. g. in a vacuum chamber).

Tbl. 4-1: Overview of various window materials

The transmission of a window is primarily a function of its thickness. For a window witha 25 mm (1”) diameter, the thickness required to withstand a pressure difference of oneatmosphere is 1.7 mm (0.070”).

Summary: As in a camera, the rating of the optics (e. g. telephoto lens), defines the size ofan object which can be resolved, or measured. The distance relationship (mea-suring distance: target area diameter) defines the rating of the optics in an infra-red thermometer. The target area for accurate measurements must be com-pletely filled by the measured object. If protection windows are installed betweenthe measuring instrument and the measured object, the proper selection of awindow material is important. The effects of wavelength range and installationconditions play an important role.

Window Material/Properties

Sap-phire Al2O3

Quartz glassSiO2

CaF2 BaF2 AMTIR ZnS ZnSe KRS5

Recommended infraredwavelengthrange in µm

1...4 1...2.5 2...8 2...8 3...14 2...14 2...14 1...14

Max. windowtemperature in °C (°F)

1800(3272)

900(1652)

600(1112)

500(932)

300(572)

250(482)

250(482)

no specs.

Transmission in visible range

yes yes yes yes no yes yes yes

Resistance to moisture, acids, ammonia compounds.

verygood

verygood

good some-what

good good good good

Suitable forvacuum applications

yes yes yes yes ·/· yes yes yes

168

4.4 Indication and Interfaces

For the user, the type of indications and available interfaces are important. For some,especially portable instruments, directly available indicators/operating panel combina-tions can be considered as the primary outputs for the measuring instrument. Analogor digital outputs can be used for additional indicators in the control room or for controlfunctions. A direct connection to data recorders, printers or computers is also possible.

Fig. 4-13: Connection example for an infrared measuring system

Industrial bus systems are gaining importance by providing the user with more flexi-bility. Sensors can be set from the control room without the need to interrupt themanufacturing process. It is also possible to change parameters, when differentproducts are manufactured on the same production line. Without the ability to makethese remote sensor parameter adjustments, e.g., emissivity value, measuring rangeor alarm limits, the changes would have to be made manually at each sensor itself.

Since sensors are often installed in inaccessible locations, the intelligent sensorassures continuous process monitoring and control with minimal personnel expendi-tures. If a fault occurs – too high an ambient temperature, cable break, failure of a com-ponent – an error message is displayed automatically.

+

-

0/4...20 mA

250 Ohm

Controller

FSK Modem

Printer

PC

DigitalIndicator

Recorder

169

4.5 Application Examples

In the beginning, only high temperatures above the 700 °C (1300 °F) range encoun-tered in glass and metal production were measured. In recent years however, addi-tional application areas, especially in the lower temperature ranges, have opened up.

• Metal and alloy production(melting, casting, rolling, hardening, forging, annealing, welding, drawing, sintering)

• Cement and lime furnaces, rotary furnaces• Fire chamber measurements in power plants and waste incineration

furnaces• Glass industry (glass crucibles, feeders, float glass line) • Food and beverage industry

(freezing, baking, frying, sterilizing, filling, packaging)• Textile industry (drying, fibers)• Paper industry (coating, drying)• Plastics (casting, forming, granulating)• Automotive industry• Maintenance and service• Chemical industry

170

5 Measurement Signal Processing and Evaluation

5.1 Application of Transmitters in Temperature Measurements

The function of the transmitter is to amplify the electrical signals from the sensor, to cor-rect and if necessary, galvanically isolate them. The conditioned signal can then beeasily transmitted over long distances to the in-/output sections of a process controlsystem or controller. The temperature values differentiate themselves in an essentialmanner from all other measurement values. Since the electrical signal from the temper-ature sensors or resistors is relative large, signal amplification in close proximity to thesensors is not required. As a result, three basically different mounting locations for thetransmitter have evolved:

The Rail Mounted is the oldest known mounting arrangement for the transmitter. Themost common designs include the 19" or DIN rail mount designs as well as integrationdirectly at the in-/output connections of regulators, valves or controllers. Transmittersfor direct Field Mounting are mounted in their own rugged housings. The fieldmounted transmitter can also be used in difficult industrial environments without therequirement for special protective measures and can be mounted in the close proximityto the sensor. In Head Mounting the transmitter is integrally mounted in the connectionhead of the temperature sensor. Transmitters which are used for this mounting designare designated as sensor head transmitters.

Fig. 5-1: The three transmitter mounting designs

➡Head mounted Field mounted Rail mounted/

Panel mounted

171

A temperature sensor is considered to be a complete measuring assembly and con-sists of the thermowell and an exchangeable measuring inset. Dependent on the se-lected mounting method for the transmitter, the temperature sensor includes either ter-minals or an adapter for direct mounting of the sensor head transmitter. The advantageof mounting the transmitter in a control room is easier accessibility should a repair berequired. This advantage is becoming less important as the electronic designs are be-coming more and more reliable.

The trend in modern instrument technology is to install the transmitters near the sensor.The sensitive connection wires are shorter, i.e., the closer the transmitter is to the mea-suring location, the less the danger that noise pickup could interfere with the tempera-ture signal. Short distances between the temperature sensor and transmitter for ther-mocouples also reduce the required wiring for the compensation cables (see chapter5.2). These are definite advantages which are realized when using a head or fieldmounted temperature transmitter. On the other hand, when the transmitter is installedin the vicinity of the sensor, it may require an internal construction suitable higherrequirements and have a more rugged transmitter design due to the harsh ambientconditions which may exist in an industrial environment.

Fig. 5-2: Transmitter in a field mount housing with local indication and operating module plusa large terminal section

172

The decision whether a transmitter should be field or head mounted depends on thelocal conditions of the system. Transmitters for field mounting, e. g. model TTF300,have the advantages of a very rugged design and are service friendly. Since the instal-lation location is usually not at an inaccessible measuring location, all start-up andservice tasks are easier to perform. A large terminal section and the integration of theoperating module underscore these advantages. The required sturdy design of thetransmitter is assured by a number of special measures. First, the electronics assemblyis completely potted, and secondly, it is mounted in an integrated chamber separatedfrom the terminal section. The electronics is protected even when the cover is removed.Transmitters for sensor head mounting, e.g. Model TTH300, are integrated directly inthe head of the temperature sensor. The electronics in this design is also completelypotted and also allows the use of a local indicator. The transmitter, when mounted in-tegrally in the sensor head, does not require the installation of a separate transmitterhousing, appreciably reducing planning and installation expenditures.

173

5.2 Measurements of Thermal Voltages and Resistances

The thermal voltage resulting from the Seebeck-Effect is utilized in a thermocouple asthe measuring principle (see chapter 2.2.3). Measuring the temperature from the ther-mal voltage is actually a difference measurement between the hot end of the thermo-couple and the reference junction temperature. For correct measurements, the elec-trical connection to the reference junction must always be made of the same materialas the thermocouple leg or suitable compensation cables must be used. Copper canbe used for the remaining wiring. Because UM = U1 - (U2+U3) an exact determinationof the measurement voltage U1 can only be made if the reference junction voltageUV = (U2+U3) is known. To measure absolute temperatures, the temperature at thereference junction TR must always be known.

Fig. 5-3: Thermal voltage measurement

When using an external reference junction the connection from the thermocouple orfrom the compensation cable to the copper wires, is located outside of the temperaturetransmitter. The temperature of the reference junction TR is controlled at a constantvalue e.g. by an integrated heater. This value is added to temperature value derivedfrom the voltage UM, to determine the temperature at the hot end of the thermocouple.

Modern temperature transmitters incorporate an internal reference junction, whichgreatly simplifies the measuring system for the user. The thermocouple leg or the com-pensation cables are wired directly to the transmitter. The reference junction is formedby the terminals of the transmitter. Its temperature TR is measured by an integratedtemperature sensor and utilized by the transmitter for the internal corrections. Thetransmitter, in this manner, can determine the temperature of the hot end of the ther-mocouple directly.

TE 1

TE 2

TE 3

U2

U3U1 UM

Thermocouple Compensatingcable

Reference

junction

Copperwire

Connection

transmitter

174

Resistance Measurements

The measurement principle utilized in a resistance thermometer is the temperaturedependence of the resistance of Platinum (see chapter 2.2.4). The resistance ismeasured by applying a constant current and measuring the voltage drop across theresistor. Ohm’s Law defines the proportionality between the resistance and the voltage.Therefore the voltage is a direct measure for the resistance and thereby the tempera-ture. Three different circuit configurations are used.

In a two-wire circuit a current is applied to the temperature dependent resistor RT froma constant current source. The voltage drop across RT is measured by the temperaturetransmitter and converted. The resultant value, however, is incorrect because of theseries resistances of the connection leads (RL1 + RL2) and the contact resistances atthe terminals (RK1 + RK2).

The two-wire circuit, even for sensor head mounted transmitters is only of limited appli-cability. Connection lead lengths and terminal connections can be designed with lowresistances, and utilizing statistical correction factors the measured values can be com-pensated in the transmitter. The temperature dependent portion of the resistance of theconnection leads must always be taken into consideration. Especially for thin wires andlong measuring sensors or connection leads, errors with a magnitude of a number ofdegrees can result. Conclusion: The two-wire circuit is not suitable for exact temperature measurements.

Fig. 5-4: Circuit diagram of a two-wire circuit

In a three-wire circuit two constant current sources are used, in order to compensatefor the disadvantages described above for the two-wire circuits. Similar to the two-wirecircuit the current source IK2 is used to measure the temperature dependent resistanceRT including the connection lead and terminal contact resistances. The additional cur-rent source IK1 together with a third connection lead is used to separately compensatethe connection lead and terminal contact resistances. Assuming the exact same con-nection lead and terminal contact resistances for all three connection leads, the effecton the accuracy of the temperature measurements can be eliminated. Practice has shown that this assumption is not always correct. It is not always possibleto assure that the terminal contact resistances are always identical. Oxidation itself,during the course of operation, can cause the contact resistance of the individual ter-

RT

RL1 RK1

RL2 RK2

UEIK1

UM UM =

(RT+RL1+RK1+RL2+RK2) IK1

RT

RL1 RK1

RL2 RK2

UEIK1

UM UM =

(RT+RL1+RK1+RL2+RK2) IK1

Two-wire circuit

175

minals to vary by differing degrees. This can cause a non-negligible error, even in athree-wire circuit.

Fig. 5-5: Circuit diagram of a three-wire circuit

The four-wire circuit eliminates all the previously described disadvantages. In thisconfiguration a constant current source is used to apply a current to the temperaturedependent resistance RT. The voltage drop across resistance RT used for the temper-ature measurement is measured by two high resistance connection leads. In this waythe voltage drop due to current flowing during the measurement is negligible and theconnection lead and terminal contact resistances RL1, RK1, RL2, RK2 do not impact themeasurement result. The four-wire circuit is therefore always used when highly accu-rate temperature measurements are required.

Fig. 5-6: Circuit diagram of a four-wire circuit

Modern transmitters support the measurement of thermal voltages and resistancesusing the above described circuit configurations in a single instrument. The user canselect the optimal measurement configuration for his application. For thermal voltagemeasurements in industrial applications, the straight forward option using an internalreference junction is used almost exclusively. Use of an external reference junctionmakes sense when a highly precise reference junction temperature of less than 0.1 Kis required. In view of the errors which could result from using the sum of a temperaturemeasuring chain (see chapter 5.10), this approach is reserved for laboratory applica-tions. For resistance measurements, the four-wire circuit should basically be usedbecause of its indisputable advantages. The three-wire circuit, with its disadvantages,should only come into play for resistance measurements when the use of electricalwiring configurations or system conditions are restrictive.

UE

IK2

RT

RL1 RK1

RL3 RK3

RL2 RK2

UM

IK1

UM =

RTIK2+ (RL2+RK2) IK2- (RL3+RK3) IK1IK2

IK1

L2 K2 -

Three-wire circuit

UE

RT

RL1 RK1

RL3 RK3

RL4 RK4

RL2 RK2

IK1 UM UM = RT IK1U

ERT

RL1 RK1

RL3 RK3

RL4 RK4

RL2 RK2

IK1 UM UM = RT IK1

Four-wire circuit

176

5.3 Power Supply of Temperature Transmitters

The transmitter is a measuring instrument, which converts an analog input signal intoan analog and/or digital output signal.

Transmitters contain active electronic components and therefore require power supplyto fulfill their functions. The number of connection wires for the power supply and outputsignals defines the power supply technology for the transmitter. This is designated as2-/3-/4-wire power supply technology and should not by confused with the resistancemeasurement configurations described in chapter 5.2 as 2-/3-/4-wire circuits.

Fig. 5-7: Power supply technology for transmitters

The Four-Wire technology is used exclusively in control cabinets. The typical powersupply values available are 230 V AC, 110 V AC, 24 V AC or 24 V DC. For the powersupply and output signals, four wires are required. The input circuit, output circuit andpower supply for the transmitter are electrically isolated from each other. Typical outputsignals are 0...5 V, 0...10 V, 0...20 mA and 4...20 mA. Additional digital outputs areoften included in transmitters with four- or three-wire power supply, that can be usedfor error or alarm signals.

The Three-Wire technology is also used exclusively in control cabinets. The use of thesame reference wire for all the instruments eliminates the need for a fourth connectionwire. The typical power supply for this option is 24 V DC. Because a connection wirewas eliminated, only the in- and outputs are electrically isolated from each other. Typ-ical output signals are 0...5 V, 0...10 V, 0...20 mA and 4...20 mA.

E A E A E A

Four-wire circuit Three-wire circuit Two-wire circuit

Power supply

Input Outputsignal

Input

Power supply

Output

signal

Referencewire(ground)

Input

Power supply

and

Outputsignal4...20 mA

177

The Two-Wire technology is the standard today for field or sensor head mounted trans-mitters. In this design the same connection wires are used for the power supply and theoutput signal, which reduces the wiring expenses in comparison to three-wire technol-ogy. Because power supply is required for the operation of the transmitter even whenthere is no output signal, the lowest output signal value cannot be zero (true zero), butmust have a value greater than zero (live zero). For this reason, the standard outputcurrent range is 4...20 mA. The live zero signal also allows the connection wires to beeasily monitored (see „Error Monitoring“ on page 181). The typical power supply for thisdesign is 24 V DC.

5.4 Design Principles for a Temperature Transmitter

The transmitter is a measuring instrument which converts an analog input signal into ascaled, analog or digital output signal. Dependent on the requirements, this signal isthen available in the measuring chain for further processing in a controller and/or forindication.

Fig. 5-8: The components in an industrial temperature measuring chain

Temperature transmitters operate based on the current measuring process (Lindeck-Rohte, better stated as a current cross coupled amplifier) which outputs a loadindependent current of 4...20 mA DC. The curves for the resistance thermometers orthermocouples are not linear. An additional function of the transmitter is to linearize theinput signal in order to output a temperature proportional signal. Additional require-ments for a temperature transmitter include selectable measuring ranges, sensorfailure monitoring, measuring circuit signal contact and the electrical isolation betweeninput, output and power supply.

R

S MU A

SensorTrans-mitter

IndicatorProcessinterface

ControllerMeasuredvalue

Temperature

Electricalsignal

Thermalvoltage

ScaledSignal

4...20 mA

178

179

Temperature Transmitter in Four-Wire Technology

The transmitter shown in the following figure is designed to either measure the mV-sig-nals (thermocouples) or make the resistance measurements (Pt100). It converts theinput values into a proportional, load independent DC current signal of 0...20 mA or4...20 mA or into a voltage signal of 0...10 V. The adaptation to the measured valuetype is accomplished by a selection made at the temperature transmitter or by usingexchangeable measuring range modules.

The temperature transmitter in four-wire technology consist of a switched controller (1),which rectifies and stabilizes the supply power. A electrically isolated voltage (2) issupplied to the in- and output circuits. Additional circuit sections are the amplifier (3),measuring range module (4), electrical isolation (6), output stage (7) and alarmsignalling (8).

Fig. 5-9: Schematic of a temperature transmitter in four-wire technology

Transmitters in explosion proof designs incorporate a circuit limiter (5) for the IntrinsicSafety of the input circuit, a power supply limiting circuit (9) and electrical isolation (6).A different explosion proof design has intrinsically safe in- and outputs as well as elec-tronic current and voltage limiters in the output current circuit. In this design a electricalisolation between the input and output is not required.

The input signal is fed through the measuring range module (4) to the amplifier (3)whose output is a load independent DC signal. When a electrical isolation (6) circuit isinstalled, the DC current signal is chopped, decoupled by an isolating repeater and con-

IK

V

19

2 7

6

8

3

45

10

IKIK

V

19

2 7

6

8

3

45

10

180

verted back to a load independent DC current in a rectified circuit with a load converter.This signal is unipolar. For conversion to a bipolar current signal or voltage an outputstage (7) is required.

The reference junction correction (10) for thermocouples, monitors the temperature atthe connection terminals of the temperature transmitter and accounts for its value in themeasurements.

The alarm signal transmitter (8) has an adjustable switching point which can be eithernormally open or normally closed. For a purely analog operating temperature trans-mitter, this switch point can be set using a potentiometer. For digital temperature trans-mitters, the switch point, the temperature measuring ranges, the connected sensor andits connection circuit can be set using programming software.

Temperature Transmitter in Two-Wire Technology

In regard to their electrical functions, these transmitters, viewed from both connectionterminals, can be considered to be passive, equivalent resistance circuits. The trans-mitter behaves as a variable resistor whose resistance changes until the current in themeasuring circuit corresponds to the measured value. As a basic component, the 4 mAcurrent, provides the power supply for the electronic circuits in the transmitter. Thecurrent is a load independent current with a signal range of 16 mA, which contains themeasured value information.

Fig. 5-10: Schematic of a temperature transmitter in two-wire technology

V

UK

UK

97

65

4

2 31

8

V

UK

UKUK

B

97

65

4

2 31

8

This transmitter is designed for the same input signals as the four-wire transmitter. Itconverts the input single values into a load independent DC current signal of 4...20 mA.The selection of the measured value type is made at the factory by adjustments madein the temperature transmitter.

Slope and zero values are also set at the factory in the temperature transmitter usingprecision resistors. The elimination of the potentiometer and the complete encapsula-tion of the electronics with potting material assure an unexcelled, rugged constructionwith long term stability. Transmitters for resistance thermometers or for thermocouplesare built using this design.

The input signal is fed from the input circuit (1), configured based on the measuringmethod and measurement range, to the amplifier (2) and converted in a final stage (3)into a load independent DC current. The constant voltage source provides the circuitcomponents with a stabilized voltage.

Error Monitoring

Error monitoring is an important function of the transmitter. Sensor failure, sensor shortcircuit and reacting when measured values are outside of the range setting must berecognized. These error conditions can also be signalled over the 4...20 mA output.Today the power supply required by the transmitters can be provided by a basic current< 3.5 mA. As a result, transmitters can be designed in which information can be trans-mitted outside of the 4...20 mA range. In the error monitor circuit (4) the output signalduring a short circuit or measuring circuit interruption condition can be selected to besignalled at a current value either above or below the 4...20 mA range.

Measured values outside of the measuring range end values are error conditions, indi-cating an undesirable status of the process. Sensor failure or sensor short circuit incomparison are error conditions indicating that the sensor should be checked orrepaired to rectify this condition. The NAMUR (International User Association of Auto-mation Technology in Process Industries) has published a recommendation definingcurrent ranges, outside of the 4...20 mA measuring range, which provide an adequateseparation, for the indication of a measured range error and for a temperature sensorerror (Fig. 5-11). This allows the appropriate corrective measures to be initiated quickly.

181

Fig. 5-11: NAMUR limits for error signalling of a transmitter in two-wire technology (NAMUR-Recommendation NE 43)

Basically the range > 21 mA, as well as the range < 3.6 mA can be utilized for error sig-naling. Ideally, the behavior during an error condition should be selected so that duringan error condition the alarm monitors connected to the output signal will not be effected.In addition, in programmable transmitters, different error conditions can often be userassigned. For example, an error condition which can turn a system off can be set if thecurrent value is > 21 mA. Error conditions, which should only trigger and alarm, can beset if the current value < 3.6 mA. It should be noted, that during a power outage or abreak in the 4...20 mA loop (not to be confused with a sensor failure) the current valueis always 0 mA. A signalling of this error condition must be made using the analog inputof the monitor.

Linearization

The curves for thermocouples and resistance thermometers are generally not linear.The linearity error is usually larger than all other errors (hysteresis, amplification, agingetc.). Since the curve shapes are known, the measuring error can be compensatedusing an inverse function. In practice it has been sufficient to approximate the curveshape using straight segments. How to select the straight segments depends on theparticular curve shape. In Fig. 5-12 the curve UA (T) is approximated first using astraight line and then two straight lines between equidistant temperature intervals andlastly with three straight lines between optimized temperature intervals for which thedeviations from the curve are minimized.

mA

0

≤ 3.6

> 3.84

20< 20.5

≥ 21

➊ = Internal currentrequirements

➋ = Forbidden outputcurrent range

➌ = Overrange value

➍ = Underrange value

➎ = Dynamic range

➏ = Measuring range

➐ = Selectable errorsignalling range

7

7

2

23

4

56

1

182

For analog transmitters, the method uses an operational amplifier with a definedamplification for each straight section. It is possible using this approach to reduce thetotal error of the temperature transmitter to approx. 0.1 % of the range.

Fig. 5-12: Linearization of a sensor curve using straight line segments

For digital temperature transmitters with a microcontroller, the curve can be linearizedusing software (Firmware) by calculating an inverse function polynomial directly fromthe curve of the standard temperature sensor. As a result of this technology, the linear-ization error for digital transmitters is less than for analog ones.

UA

UME

UMA

TMA TME

T

UA

UME

UMA

TMA TME

T

UA

UME

UMA

TMA TME

T

UA

UME

UMA

TMA TME

T

UA

UME

UMA

TMA TME

T

UA

UME

UMA

TMA TME

T

Two pointwithoutlinearization

Four pointequidistantlinearization

Four pointoptimizeslinearization

183

5.5 Programmable Temperature Transmitters

Analog transmitters are adjusted and set for sensor type and for one measuring range.If a sensor type or measuring range is changed, the transmitter must also beexchanged. A programmable transmitter on the other hand, can be reprogrammed byentering the new parameters for the changed application. When designing a system, itis possible to select transmitters in which the required measuring range can be set atstart-up. This simplifies and reduces the planning and design time and reducesreplacement part inventory costs. Programmable transmitters also clearly reduce ser-vice and maintenance expenditures thus reducing the cost of ownership.

Circuit Block Diagram

The following circuit block diagram shows a typical design for a programmable temper-ature transmitter. The transmitter contains two microcontrollers. In the primary circuitas well as in the secondary circuit the controller operates using the software (Firmware)designed for that circuit. In the primary circuit the multiplexer is controlled, which trans-fers the values from the sensors, the reference and the reference junction. The signalsreach the analog-digital-converter and are read by the microcontroller. Filter functionsand sensor failure monitoring is also carried out by the this controller. The digitized sig-nal is fed by a transducer to the microcontroller in the secondary circuit. The transduceralso provides the electrical isolation between the primary and secondary circuits.

Fig. 5-13: Circuit block diagram of a digital temperature transmitter

The second microcontroller in the secondary circuit controls the digital-analog-con-verter and is responsible for the data exchange between the communication and theprogramming software. The required software (Firmware) is stored in an EEPROM. AnI/U-converter powers the transmitter from the 4...20 mA signal. This same 4...20 mAsignal is used to provide communication with a supervisory system (PC) using a FSK-interface.

µC µC U

FSK

EEPROM

I

4...20 mA

DA

A

D

MUX

Ref. junc-tion Pt100

Reference

Filter

Sensorbreakmonitor

184

As can be recognized in the following figure, two sensors can be connected to thetransmitter. The averages and differences between the two sensor signals can be cal-culated and also transmitted as an output signal.

Fig. 5-14: Software structure of a digital temperature transmitter

Programmed Curves

In a programmable transmitter are all the curves for the most common measuringapplications stored. They include the basic values for the appropriate measurementresistors and thermocouples, which can simply be selected when programming thetransmitter.

A Pt100-resistance thermometer in accuracy class Type B has a temperature depen-dent measuring error at 400 °C (752 °F) of several K (see Fig. 3-5). For measurementswith resistance thermometers the achievable accuracy after selecting the standardcurve can never be better than the allowable measuring deviations of the sensor.Programmable transmitters, such as the TTH300, offer the possibility to use the exactcurve of a previously measured temperature sensor by entering the coefficients for theCallendar Vandusen equation (polynomial see chapter 3.1.5).

+

lin T

1 2

3

4

5

6

Referencejunction Pt100

Input 1

Input 2

Measure-ment val.conditio-ning, wirecompen-sation

Refer-encejunctioncorrec-tion

Lineari-zationaveragediffer-ence

Damping Scaling

FSK

Status

Analogoutput

1 = Sensor signal input2 = Reference junction temperature3 = Linearized measured value4 = Percent of the output span5 = Output value in mA6 = FSK programming

185

For curves with a monotomic curve shape it is possible to enter a free style curve withusing as many as 64 points. In this way a digital transmitter can be matched to any sen-sor or to the calibration or adjustment of the entire measuring chain. To accomplish this,the sensor to be calibrated, together with the transmitter and its power supply instru-ment, are calibrated against a “Standard“. The deviations of the output signal are cor-rected in the transmitter. Deviations from the curve for the entire measuring chain aslow as < ± 0.05 K are possible.

Diagnosis

Programmable transmitters include extensive capabilities to detect and signal errorconditions. In order to provide the user with an effective trouble shooting strategy, theerror types where classified and prioritized by NAMUR based on their cause andimportance to operation. A distinction is made between sensor, transmitter, configura-tion/calibration and measuring range errors. Based on the priority assigned to eacherror, the transmitter selects and signals the error with the highest priority. Processcontrol systems utilize a classification system for display and diagnosis based on theiroperating phase, start-up, operation, monitoring or asset management. In this way theuser is provided with the most important information at the correct location at thecorrect time.

Tbl. 5-1: Diagnosis and error classifications for transmitter TTH300

Standard

• Sensor error (break or short circuit)• Instrument error• Over/under measuring range• Simulation active

Expanded

• Over/under alarm value• Sensor backup active (Sensor 1 or Sensor 2 failure)• Zero or span adjustment active• Low power supply• High transmitter ambient temperature (> 85 °C (185 °F))• Memory• Indicator• Writing protection• “Drag indicator“ for sensor temperature and electronics temperature

186

Drift Warning and Redundancy Circuit

Recalibration and recertification are normal procedures for measuring locations whichare subject to measuring instrument inspections. Two channel transmitters, such as theTTH300, can provide some relief, by increasing the required recalibration interval. Tocheck for drift, a temperature sensor with two integrated measuring locations can beused. In addition to its actual measuring function, the transmitter continuously com-pares the difference between the two measuring locations. If the deviation exceeds aspecified value, an alarm is signalled. Using this signal, the user is advised by the trans-mitter that a recalibration is required. The number of manual inspections are apprecia-bly reduced, because a recalibration will only be conducted when it is really necessary.

To increase the operational availability, two redundant temperature sensors areinstalled. For single channel transmitters the connections can be manual switched tothe other sensor if one fails. Two independent Pt100 measuring locations can beconnected to a two channel transmitter. Using the integrated “hot swap“ function, if amalfunction in one of the measuring locations is recognized by the transmitter, an erroris signalled and the input is immediately switched to the redundant element. The on-time of the measuring location is significantly increased, since the repair of the defec-tive element can made during the next, scheduled service shut down. In summary, twochannel transmitters appreciably reduce service and maintenance expenditures.

187

5.6 Communication Interfaces

Programmable transmitters with a classic 4...20 mA signal transmission are availablewith a digital communication interface. These interfaces are used primarily for diagno-sis or for selecting the required transmitter functions for the application while continuingto use the analog output for fast measured value transmission. There are differentprogrammable transmitters interfaces, suitable for local as well as for remote program-ming. Transmitters with fieldbus interfaces usually no longer include an analog output.The measured signal, diagnosis and parameters are transmitted digitally over the field-bus.

Local Programming

The transmitters with local communication interfaces (LCI) often have, in addition to theconnections for the 4...20 mA signal, a separate, manufacturer specific programmingconnection. An adapter is used to connect the instrument directly to the programmingdevice. A requirement is that the distance between the instrument and the program-ming device is only a few meters (yards).

This type of local programming is found primarily in transmitters designed for installa-tion in control rooms and for the economical sensor head transmitters. The program-ming is usually a one time event, made prior to the start-up of the transmitter, e. g. inthe work shop. Continuous monitoring of the transmitter, because it only has a locallyaccessible interface, is not possible. Changes to the parameters or inspections of thetransmitter by service can only be accomplished using portable programming devices.

Fig. 5-15: Local Communication Interface

Remote Programming

When the transmitter is to be programmed or monitored from large distances, transmit-ters with FSK-communication are used (FSK = Frequency Shift Keying). In this design,a frequency of 1200 Hz or 2200 Hz is superimposed on the analog 4...20 mA signal.This type of data transmission is based on the Bell 202 Communication Standard.

LCITransmitter

LCI Adapter

Field Control room

188

Fig. 5-16: Bell 202 Communication Standard

The two frequencies contain bit information 1 or 0. A real simultaneous communicationwith a response time of approx. 500 ms per measured value can be achieved. Becausethe average value of the frequency is zero, the FSK-communication does not affect theanalog signal. To program the transmitter a FSK-modem is required.

The HART-Protocol

The HART-Protocol (Highway Addressable Remote Transducer, i.e. a protocol for busaddressable field instruments) operates using the above named technology. TheHART-Protocol is an industry tested digital communication method available for fieldinstruments. There is a worldwide HART-User Group. All well known companies in themeasurement and control fields are members. HART conforms to the Open SystemsInterconnection basic reference model (OSI) for open system communications, devel-oped by the International Standards Organization (ISO).

Point-to-point operation is used for simple programming of HART-instruments. Whenprogramming, it is always necessary that the connected HART-instrument is powered.There are suitable programming adapters or transmitter power supplies available forthis purpose. The following figure shows the various point-to-point operating modes.

The Bell 202 Communication Standard

+ 0.5 mA

- 0.5 mA

0

"1" = 1200 Hz "0" = 2200 Hz

Analog Signal

(4...20 mA)

-

189

Fig. 5-17: FSK-programming

The manufacturer specific programming adapters accept the HART-temperature trans-mitter and provide its power supply. The FSK-modem is used to convert the FSK-infor-mation into a PC compatible format. Using this design, the transmitter, prior to start-upin the field, can be programmed from the control room without any large wiringexpenses. If the temperature transmitter is already installed in the field, it is possible toprogram it using a handheld terminal (HHT) without any effect on the 4...20 mA outputsignal. The FSK-modem is integrated in the HHT. The power supply is provided by thetransmitter power supply in the control room.

According to the HART-specifications, a load of at least 250 Ω must always be installedin the 4...20 mA loop. This assures that the low internal resistance of the power supplycannot short out the HART-signal. When using older or simple power supply instru-ments, the connection wire must be opened and a resistor installed. In modern HARTtransmitter power supply instruments this load is integrated. In addition, they are trans-parent to the FSK-signals. A simple connection of a handheld terminal or FSK-modemcan be made either in the field or in the control room. Many of the transmitter powersupplies contain sockets, for connecting terminals or modems so that the current out-put or supply circuit need not be opened. If power supplies are installed instead, whichdo not have the ability to transmit FSK-signals, then an FSK-modem must be installedbetween the transmitter power supply and temperature transmitter. In every HART-in-terconnection two indicating/operating instruments are allowed. A primary one, usuallyin the process control system, and a secondary one, e. g. a handheld terminal or alaptop.

4...20 mA

4...20 mA

FSKTransmitter

FSK Modem

Field ControlRoom

Isolator

FSK Modem

FSK ModemConfigurationAdapter

FSKTransmitter

FSKTransmitter

Isolator

190

HART Multi-Drop-Mode

In the Multi-Drop-Mode the transmitter with a FSK-interface is also bus capable. Thetwo connection wires for the 4...20 mA signal is also used for the bus communication.This operating mode requires only a single pair of wires and a power supply to commu-nicate with up to 15 field instruments. When the connected instruments are configuredfor this operating mode, their output current is frozen at 4 mA. The instruments onlycommunicate digitally. Their analog output signal is no longer used to transmit temper-ature values. The connection of a recorder or an analog indicator is no longer possible.

Fig. 5-18: Bus operating mode Multi-Drop

In this operating mode the transmission of parameters and diagnosis data is in the fore-ground. Since only about 2 measured values can be transmitted digitally over theHART-Protocol per second, this communication method is only used for slower pro-cesses, e. g. the monitoring of very distant systems such as pipelines or tank farms.

HART-Multiplexer

It is also possible using a FSK-multiplexer to connect multiple instruments to a singleprogramming instrument. Several hundred HART-field instruments can be accessedfrom a central location. This simplifies the start-up and maintenance since they can beperformed while the system is operational. It is possible to set a HART-transmitter inthe simulation-mode, so that the 4...20 mA signal can be set to a fixed, user program-mable current value. In this manner, the current loop can be tested without using themeasured value. The measuring location parameter values can be stored in the pro-gramming instrument. This is a practical function for accessing the diagnosis and assetmanagement data. This allows a quick response when service is required. This func-tionality can only be viewed as an intermediate step for fieldbus systems with openfieldbus protocols.

Transmitter1

4 mA 4 mA 4 mA

Transmitter2

Transmitter15

FSK Modem

Power supply

191

Fieldbus Systems

The art of instrumentation was dramatically changed by the introduction of fieldbustechnology. In the past, a two conductor wire had to be connected from each instrumentto the control room for the analog 4...20 mA signals. In the fieldbus only a single twoconnection wire cable is required to connect up to 32 temperature transmitters.

Fig. 5-19: PROFIBUS PA installation using a PROFIBUS PA-profile

This figure shows an example of a PROFIBUS PA installation of 32 temperature trans-mitters. Since this concerns a fieldbus, it is necessary to install a bus termination at theend of the cable. The transmission medium is a twisted two wire copper cable with ashield. Instruments can be exchanged or added during operation. With a commontransfer rate of 31.25 KBaud distances up to 1900 m (6200 ft.) can be spanned.

The temperature transmitters can easily be integrated into PROFIBUS DP-Networksusing a segment coupler. The segment couplers have a simple baudrate conversionfactor of 1:3. Therefore the transmission speed of the PROFIBUS DP when using thesesegment couplers is fixed at 93.75 kbit per second (93.75 KBaud). If one wants to cir-cumvent this fixed transmission ratio between the PA and DP, a DP/PA-Link can beused instead of the segment coupler. This allows, dependent on the transmissionlength of the PROFIBUS DP, the total transmission speed to be realized.

Segment -

koppler

PROFIBUS PA PROFIBUS DP

850°C

100°C

0°C

-200°C

1

3

32

2

Temperature

transmitter

Temperature

transmitter

Temperature

transmitter

Temperature

transmitter

Bus connection

Segment

coupler

PROFIBUS PA Profile (Pt100-Temp.)

Physical Limitation

Measurement LimitUpper Alarm LimitUpper Warning Limit

MeasurementValue

Lower Warning LimitLower Alarm LimitMeasurement Limit

Physical Limitation

192

What has been accomplished in the European markets through the activities of thePNO (Profibus-Nutzer(User)-Organization), is accomplished in the American marketplace by the FF (Fieldbus Foundation). Each organization supports a non-compatiblebus protocol. Only the bus supplied transmission technology per IEC 1158-2 and thedata transmission speed of 31.25 kbit per second are identical for PROFIBUS PA andFOUNDATION Fieldbus.

Fieldbus Profiles

The PROFIBUS PA-Profile enables the exchangeability and interoperability of fieldinstruments from different manufacturers. It is an integral component of PROFIBUS PAand can be obtained from the PROFIBUS-User Organization. The PA-Profile consistsof a framework specification, which contains valid definitions for all instrument types,and instrument specification sheets which include the specific agreements which werereached for each instrument type.

The profiles use standardized function blocks. The description of the instrument behav-ior is accomplished by defining the standard variables, which describe the propertiesof the transmitter in detail. Every instrument must have a GSD (Generic Slave Data)file, which contains the specific instrument data. These files are necessary in order toconnect the instrument described therein into the bus. The procedure is supported bythe software tools from the different manufacturers. Every instrument must make avail-able the parameters defined in the PROFIBUS PA-Profiles.

Measured values are calculated in a Transducer-Block (TR) and transmitted over anAI-Block to the PROFIBUS-Master. The following table lists the most important param-eters of an AI-Block. For actuators, AO-Blocks are used.

Tbl. 5-2: Defined parameters of an AI-Block in the PROFIBUS PA-profiles

Parameter Read Write Function

Out ● Actual measured value of the process variables

PV_SCALE ● ● Scaling of the process variables

PV_FTIME ● ● Rise time of the function block- output in s

ALARM_HYS ● ● Hysteresis of the alarm function in % or range

HI_HI_LIM ● ● Upper alarm limit

HI_LIM ● ● Upper warning limit

LO_LIM ● ● Lower warning limit

LO_LO_LIM ● ● Lower alarm limit

HI_HI_ALM ● Status the upper alarm limit with time stamp

HI_ALM ● Status the upper warning limit with time stamp

LO_ALM ● Status the lower warning limit with time stamp

LO_LO_ALM ● Status the lower warning limit with time stamp

193

For the various parameters it can be seen that not only the measured value, but alsothe alarm and warning information is transmitted. The digital transmission of the mea-sured values allows a higher accuracy to be achieved, because the conversion of themeasuring range to a span of 4...20 mA is no longer necessary. Wider measuringranges can be defined, without sacrificing any accuracy.

Programming Software

For the different instruments from the various manufacturers, special programmingsoftware is available. A number of firms have developed a common programming soft-ware for their entire instrument palette. It can be used, from a common user interface(GMA-Standard), to program the parameters and read the measured values and diag-nosis information from different instrument types.

5.7 Temperature Transmitters in Explosion Hazardous Areas

The ability to install transmitters in explosion hazardous areas is an important require-ment for their use in chemical, petrochemical and process industries. The design, con-struction and operation must be in accord with the generally accepted regulations.Equipment, which is installed in explosion hazardous areas classified as Zone 0 or 1,as well as hazardous dust areas classified as Zone 20 or 21, must have been issued atest examination certificate by a registered, certification body. This certificate is issuedwhen the design of the equipment has been examined and found to be in accord withthe standards for the applicable ignition type.

The concept of explosion protection includes not only the design of the instrument in-stalled in the explosion hazardous area, but also the consequences of the designs ofall the other components in the measuring chain. Fig. 5-20 and Fig. 5-21 show thestructure for typical measuring chains for the installation of temperature transmitters inexplosion hazardous areas.

194

Fig. 5-20: Installation of temperature transmitters in explosion hazardous areas

1

2

4 ... 20 mA 4 ... 20 mA

1

2

4 ... 20 mA4 ... 20 mA 4 ... 20 mA

0/4 ... 20 mA

1

2

3

+

-

+ -

Field (explosion hazardous area) Control room (safe area)

Power supply24 ... 230 V UC

Two-wire design, transmittere. g. II 2(1)G EEx [ia] ib IIC T6

intrinsic safety Active isolator, input intrinsic safetye. g. II (2)G [EEx ib] IIC

Field (explosion hazardous area) Control room (safe area)

Power supply24 ... 230 V UC

Two-wire design, transmitter intrinsic safetye. g. II 2(1)G EEx [ia] ib IIC T6

Ex safety barriere. g. II (2)G [EEx ib] IIC

Active isolatorNon-Ex

Field (explosion hazardous area) Control room (safe area)

Power supply24 V DC

Three-wire design, transmitter inpute. g. II (1)G [EEx ia] IIC or II (2)G [EEx ib] IIC

intrinsic safety

Intrinsically Safe Installation: Ex-temperature transmitter (Two-wire design)with Ex-input transmitter power supply

Intrinsically Safe Installation: Ex-temperature transmitter (Two-wire design)with Ex-safety barriers installed between transmitter and power supply

Intrinsically Safe Installation: Ex-Temperature transmitter (Three-wire design)

195

Fig. 5-21: Installation of temperature transmitters in explosion hazardous areas

1

2

4 ... 20 mA 4 ... 20 mA

0/4 ... 20 mA

1

2

4

+

-

0/4 ... 20 mA

1

2

4 3

3

Field (explosion hazardous area) Control room (safe area)

Power supply24 ... 230 V UC

Two-wire design, transmitter withflameproof enclosure with incident-power-limitation for temperaturesensor, e. g. II 1/2G EEx d IIC T6 Isolator

Non-Ex

Field (explosion hazardous area) Control room (safe area)

Power supply24 ... 230 V UC

Ex safety barriere. g. II (1)G [EEx ia] IIC

Four-wire design, transmitterNon-Ex

Field (explosion hazardous area) Control room (safe area)

Four-wire design, transmitter input intrinsic safetye. g. II (1)G [EEx ia] IIC or II (2)G [EEx ib] IIC

Power supply24 ... 230 V UC

Power supply24 ... 230 V UC

Intrinsically Safe Installation: Ex-temperature transmitter (Four-wire design)

Intrinsically Safe Installation: Ex-temperature transmitter (Four-wire design) with Ex-safety barriers installed ahead of the transmitter

Flameproof enclosure temperature transmitter (Two-wire design) with transmitter power supply

196

If the transmitter is to be installed in an safe area, then all that is required is that anintrinsically safe input circuit be incorporated in the transmitter. If this is not the case,then the required intrinsic safety can be achieved by installing suitable safety barriers,designed specifically for temperature sensors. Transmitters for these applications areoften designs using three- or four-wire technology. Since the power supply is inte-grated, a separate power supply is not required. Transmitters for field or sensor headmounting always use a two-wire design. For the protection type intrinsic safety thepower supply is provided either by power supply with integrated electrical isolation orfrom a network component with barriers installed ahead of it. The function of the powersupplies or barriers is to assure that energy limitation required by the intrinsic safetyregulations is present. For installations using the flameproof enclosure type of protec-tion, ordinary network components and transmitters without special safety measurescan be used, because the explosion protection in this case is provided by the flame-proof enclosure in the field.

To use this measuring technology, the user must follow the requirements without anyqualifications if possible. For example, if exchanging an instrument in the hazardousarea while it is powered is a requirement, then the protection type intrinsic safety hasbeen proven to be advantageous. An intrinsically safe handheld terminal can also beconnected to the transmitter in the field while powered in the explosion hazardous area.Therefore, the communication described earlier can also be utilized in such environ-ments without limitations.

Power Supply for Programmable Transmitters

For non-explosion hazardous areas, a two-wire transmitter can be supplied from a nor-mal power supply source with 12...36 V. Often a load with a connection to ground isincorporated across which the signal voltage can be measured. Due to this connection,galvanic coupling could occur between the measuring circuits of two transmittersresulting in erroneous currents. This is especially true when the temperature trans-mitter does not have electrical isolation between the in- and output circuits. To correctthis situation, the use of power supplies is suggested.

A modern power supply has four principle functions:

• Supplying the intrinsically safe measuring circuits while taking into account the required internal resistances for HART-communication

• Decoupling the intrinsically safe field circuits from the non-intrinsically safe control room circuits

• Electrical isolation • Load conversion

The power supply provides a voltage UM at the input terminals of the transmitter (1)from its output voltage US reduced by the load of lead resistance RL,. The input circuit(3) has a supply input and for explosion proof design includes an Ex-Limiter (2). A cor-rectly sized internal resistance is incorporated in the power supply circuit for the HART-communication so the installation of an external 250 Ohm resistor is not required. The

197

next component, a curve module (4) operates per its setting dependent on the applica-tion, to provide a proportional or linearized output. In the newer transmitter power sup-plies this module is not included because the measured signal has already been linear-ized in the transmitter.

This conditioned signal is fed to the output amplifier (6) through the electrical isolationstage (5). The electrical isolation is transparent to the superimposed HART-Signal. Thesupply voltage is electrically isolated from the input or supply and output circuits by aswitching regulator with rectifier (8), Ex-Limiter (9) and the power supply (10).

Fig. 5-22: Two-wire transmitter and isolator in an explosion proof design

The following conditions must be satisfied when connecting a transmitter to a powersupply:

UM = Minimum operating voltage for the transmitterUS = Minimum supply voltage of the power supplyRL = Connection wire resistance between transmitter and power supply (loop)

UM ≤ US - 22 mA x RL

USUM

RL

t

89

10

654321

USUM

RL

t

89

10

654321

Field (explosionhazardous area)

Control room

198

If additional instruments, e. g. indicators are connected to the 4...20 mA loop, then theinternal resistances (load resistance) of these instruments must be added to the con-nection wire resistance RL. Programmable transmitters, such as the TTH300 or theTTF300, control their integrated indicators over a digital interface. In this case, therequired power is supplied by the operating voltage UM. It must not be considered sep-arately. The maximum possible current is assumed to be 22 mA at the minimum volt-age, since modern transmitters use the current range above 20 mA to signal error con-ditions. (see chapter 5.4).

The intrinsic safety of the interconnections is assured if the following conditions aresatisfied:

The power supplies are available as 19"-cards for installation in 19" housings, in a snapdesign for rail mounting and plug-in designs for card mounting frames. The plug-indesigns are moving into the foreground more and more because they reduce the wiringcosts.

Power Supply of the Fieldbus Transmitters

A fieldbus barrier protects the main segment of the fieldbus from improperly connectedfield instruments and assures continued operation of the fieldbus. It incorporates thefollowing functions and advantages:

• Electrical isolation between the main and branch lines to provide protection from problems which might occur due to potential differences and error currents due to potential equalization.

• The short circuit current limiters on the outputs prevents errors on the fieldbus segment. The segment continues to operate.

• Connections available for up to four intrinsically safe field instruments.

• Cascading of up to four fieldbus barriers per fieldbus segment.

Intrinsically Safe Equipmentplus Cablee.g. ABB-transmitter

Associated Equipmente.g. Transmitter power supplies/SPC input

UiIiPi

Li + Lc (cable)Ci + Cc (cable)

≥≥≥≤≤

UoIoPoLoCo

199

• No additional distribution boxes required. For the last fieldbus barrier a switchable termination resistor is included that can be activate.

• Installation in explosion hazardous areas.

• Easy Ex-Loop-Check using the FISCO-Design.

Fig. 5-23: Fieldbus supply using a fieldbus barrier

Operate

Engineer

Control

Field

EEx ia

PT F

PROFIBUS DP/DPV1

Ethernet

PROFIBUS PA

PROFIBUS PA

Linkingdevice

200

5.8 Electromagnetic Compatibility (EMC)

The EU-Directive 2004/108 EC (formerly 89/336/EWG) is controlling for the EMC(Electromagnetic Compatibility) of a temperature transmitter. The EMC requirementsare defined in the International Standard IEC 61326 . The standards are defined in IEC801-1 to IEC 801-6 and IEC 61000-4-1 to IEC 61000-4-17.

In addition to the basic generic standards, there are also product standards, which mustbe observed for the various instruments. In addition to the requirements in the EMC-Directive there are additional special requirements for the chemical industries, whichare defined in the NAMUR-Guidelines (NE 21) and include or exceed the requirementsin the basic generic standards.

The most common causes of interference are electric or electromagnetic in origin:

• Variations or short term interruptions in the supply voltage

• Static electricity discharges

• Electromagnetic fields

• Transient over voltage pulses (bursts) on the supply or signal connection cables

• Transient over voltage, energy rich individual pulses (spikes)

The originators of interference signals are often electric and electronic switches, relays,circuit breakers, frequency converters, fluorescent tubes, magnetic valves, motors,wireless equipment, as well as atmospheric disturbances such as lightning. In particu-lar, the discharge of static electricity and the generation of electromagnetic fields oftenoccur in the production process itself.

The interference behavior defines the reaction of an instrument to an interference usingthree evaluation criteria:

A. No reduction in functionPrimarily for analog instruments, recognizable effects within the error limits are permis-sible. Pure digital instruments may not exhibit any recognizable effects.

B. Reduction in functionEvaluated is the effect on the function during the period in which the interference effectsoccur. Reduction of function during this time period is permissible. Subsequently, thefunction must return to its original status automatically without any permanent changes.

C. Loss of functionEvaluated is the effect on the loss of function from the start of the interference until it isrestored automatically or manually. For operation outside of the tolerance limits theinstruments must automatically return to normal operation or switch to a start readysafety setting.

201

For suppression of electromagnetic interferences, appropriate measures should beemployed by the user when installing the instrument.

Modern electronic transmitters generally have the best possible disturbance reaction.They comply with the increased NAMUR requirements and guidelines and oftenactually exceed them. When the potential equalization is poor or the installation has ahigh degree of electromagnetic noise, it is not always possible to achieve the desiredresults. In such applications it may help to electrically isolate the low resistance shieldfrom the system potential and only ground the cable shield at one end.

Measures Guidelines and Recommendations

Current supply – electrically isolated– symmetric– ground free

Installation – power and signal cables routed separately– instrument not installed close to electromagnetic interference sources– provide lightning protection if installed outdoors

Cable shield – assure sufficient potential equalization– exclude equalizing currents in shields– provide a cable shield preferably on both sides– ground cable shield to housing in the shortest way using large

area connections

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5.9 Temperature Transmitters using Interface Technology

In many installations the functionality of the in-/output assemblies of Stored Program-mable Controllers (SPC) or Process Control Systems (PCS) is not sufficient, requiringan additional signal adapter stage. This might be the case when temperature measure-ments, transmitter power supply, electrical isolation, load increases or intrinsically safesignal circuits for explosion hazardous areas are required. These functions are per-formed by suitable interface components.

Analog Interface Technology

For the analog Interface Technology, 2 connection wires are required for each signal.The supervisory systems often contain 8 or 16 channel input cards. In order to connectto the input cards in these systems, an internal distribution system is required. If thesignal connection wires have to be routed over a very long distance, the individual pairscan be connected to a larger cable containing multiple pairs of wires. In order to reducethe wiring and connection expenditures, interface components are installed on theprewired module carriers. The wiring level and the function level are thereby separatedfrom each other. Without a module, a quick check of the wiring is possible. Easy plug-in technology allows quick connection to the module carrier or individual socket.

Digital Interface Technology

In the automation and process technology, the required field signals are often gatheredfrom distant systems. In the classical, analog point-to-point wiring scheme, in which allsignals are usually carried over 2 connection wires, long cable runs, many distributionboxes are required. Expenses are appreciably reduced when using a decentralized,digital interface technology (Remote I/O).

All in-/output modules are designed to be bus capable, so they can be connected to anopen fieldbus over a bus coupler (gateway). In the module carrier the data is ex-changed between the bus coupler and the I/O modules over a fast, redundant internalbus. The assignment of the field signals, is done using the software. The plug-in buscoupler allows adaptation to the fieldbus being used. Every bus coupler contains acomplete process picture of all the connected field signals. The supervisory processcontrol system or the controller communicate with the external fieldbus over the buscouplers. Expensive wiring in no longer necessary.

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Fig. 5-24: Digital interface components S900

Bus coupler and the connected in-/output modules constitute one node. Larger num-bers of participants are incorporated by adding additional nodes. The cycle time for theinternal communication bus is in the range of a few milliseconds. The number of nodes,bus length and cycle time of the external bus structure depend upon the bus systemused. Every bus coupler represents one participant. In order to increase the number ofparticipants, the bus is extended from one bus coupler (bus node) to the next buscoupler. In order to increase the availability of the in-/output modules, the fieldbusconnections can be designed to be redundant. The analog in-/output components aredesigned for HART-communication. All important measured values, diagnosis andconfiguration information from the connected HART field instruments are available overthe bus and can be transmitted to the process control system. The programming of theHART-transmitters can be done directly from the process control system over the field-bus, through the remote-I/O-level to the HART-instruments, without any problems. Thetemperature or HART-transmitters connected to a remote-I/O-system are thereforecomparable to fieldbus transmitters in their function.

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Fig. 5-25: Decentralized redundancy capable fieldbus interface components(with integrated HART or fieldbus communication)

The sensors or actuators to be connected are power supplied directly from the mod-ules. The wiring for separate power supplies is no longer necessary. The highest pos-sible degree of safety and noise insensitivity is assured by an power supply electricallyisolated from the bus and short circuit proof in- and outputs. Modern remote-I/O-sys-tems, such as the S900, also incorporate a comprehensive redundancy concept.

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For applications in explosion hazardous areas an Ex-isolation module can also be usedas the decentralized interface component for direct installation in Zone 1 areas.

Fig. 5-26: Compact remote I/O-system CB220 for zone 1 installation

5.10 High Accuracy Temperature Measurements with Programmable Transmitters

If an absolute accuracy of 0.1 K (± 0.05 K) is required, it is only possible if the entiremeasuring chain is calibrated as a unit. This will become clear after all the measuringvalues in the measuring chain are evaluated.

Fig. 5-27: Industrial temperature measuring chain from sensor to digitizer

In a typical measuring chain the temperature is measured by a sensor (1). The temper-ature signal is then fed to a transmitter (3) over the compensating cable (2). There thesignal is amplified and fed to transmitter power supply (5) over another pair of connec-tion wires (4). The signal is transmitted to an analog/digital converter (7) over moreconnection wires (6). Only after this conversion is the measured value in digital form

t

S AGL L L

A

D

1 2 3 4 5 6 7

tt

S L L

A

D

1 2 3 4 5 6 7

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and in no longer subject to changes. Tbl. 5-3 shows the typical, statistical errors occur-ring in the process industry for a 0...400 °C (32..752 °F) measurement with a resistancethermometer in a three-wire circuit.

Tbl. 5-3: Uncertainty of an industrial temperature measurement 0...400 °C (32...752 °F)

Additional errors due to the compensation cable and reference junction, when makingmeasurements with thermocouples, must also be considered. The compensationcables has the same thermal voltage as the element material itself at a specific tem-perature. Above 100 °C (212 °F) appreciable differences may occur. This is especiallytrue if the materials of the compensation cable are so called special alloys. Even withintheir allowable ambient temperature range, the compensating cables have a tolerance.In EN 60584 the deviation limits for the individual compensating cables are listed. Thislist indicates that for each element, and therefore each cable type, the deviation limitsare a number of µV and therefore a deviation of number of K is possible. Dependent onthe accuracy as well as the achievable thermal coupling of the reference junction anadditional measurement error of 0.1 to 0.5 K must be considered.

In addition to these statistical errors, there are dynamic errors based on the finiteresponse time of industrial temperature sensors (see chapter 3.4.4) and of the ambienttemperature dependent errors due to measurement type used which must also be con-sidered. The largest contribution to the ambient temperature errors can be attributed tothe usually high temperature changes in the field at the transmitter. Typical values forthe assumed example are 0.02K per 10K ambient temperature change.

Sensor head mounted transmitters, because of their proximity to the sensor, have theleast interference on the sensitive signal connection wires. Their use, due to their notnegligible ambient effects, only comes into play when the temperature variations at thesensor head are expected to be small. Otherwise, field mounted transmitters are pre-ferred for high accuracy measurements. When the digital signal output from a fieldbus

MeasurementUncertainty

Cause Typical Error

1 Sensor Tolerance Class A according to EN 60751, at 40 °C (104 °F)

0.95 K

2 Heat loss Ratio insertion depth to diameter = 7(see chapter 6.1.4, Fig. 6-2)

0.4 K

3 Self heating Measurement current 0.3 mA 0.05 K

4 Signal connection wires

Three-wire circuit, noise 0.1 K

5 Transmitter Accuracy 0.1 % 0.4 K

6 4...20 mA loop Noise 0.05 K

7 Transmitter power supplies

Accuracy 0.25 % 1 K

8 4...20 mA loop Noise 0.05 K

9 input to PCS/SPC Accuracy 0.1 % 0.4 K

Total uncertainty Error sum, root mean square 1.55 K

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transmitter is used, the errors due to the analog signal processing in the transmitterpower supplies or in the analog input circuits of the data processing instruments areeliminated. Since the largest contribution to the statistical errors comes from the sensoritself, fieldbus transmitters cannot make any appreciable improvement to the total ac-curacy. High accuracy measurements can only be achieved with temperature transmit-ters, if the statistical measurement uncertainty of the entire measuring chain is compen-sated.

Recalibration and recertification are common procedures for measuring locations thatare subject to measuring equipment testing. To compensate for the statistical errors thetemperature sensor is calibrated at many different temperature reference points. Thecurve produced by the comparison calibration in a precision temperature measurementsystem is stored in the non-volatile memory of the sensor head mounted transmitter.The calibration of field mounted transmitters is somewhat more complex, because thesensor and the transmitter must always be calibrated as a matched pair, if all the errorsin the measuring chain are to be compensated.

Stated more precisely, for analog measuring circuits the input circuit of the data pro-cessing system, and the transmitter power supply, if used, must be connected duringthe calibration, because they make a significant contribution to the total error. In prac-tice this is not done very often because of the complexity it entails. Calibrated fieldbustransmitters have a distinct advantage, because the use of digital signal transmissioneliminates the additional signal errors.

The remaining measurement uncertainty is then only a function of the calibrationequipment and the resolution of the correction curve. The achievable measurementuncertainty of the temperature sensors in the temperature range from 0...400 °C(32...752 °F) is ± 50 mK. This measuring accuracy can be documented by a DKD-Cer-tificate (German Calibration Service) (see chapter 6.2).

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6 Accuracy, Calibration, Verification, Quality Assurance

6.1 Accuracy

6.1.1 Basic Fundamentals

As with the measurements of all variables, temperature measurements cannot bemade at any arbitrary accuracy. The result of the measurement is not only dependenton the variable being measured, but also on the measuring process being used, whichis affected by very many other factors, which in turn also influence the measurementresults.

Error effects may include:

• errors due to the incompleteness of the measuring instrument used,

• errors due to the influence on the (undisturbed) measured value by the measurement instrument (sensor),

• errors due to effects caused by deficiencies in the test model (especially during the evaluation),

• errors of a random type due to unforeseen factors resulting from predictable interference effects of an “experimental environment“.

If an “error free value“ is defined as the measured “true value“ (an unknown which is tobe determined by the measurement), then all the measurement values which resultfrom repeated measurements under the same conditions and with a measurementsetup of high enough resolution, will lie around the true value within a specific range(variation range). The measurement error of the individual measurements is defined asthe difference between the measured value and the (actually unknown) true value.

Measuring error = measured value - true value

This raises the question, which of the measured values is closest to the true value andcan serve as the result of the measurement? The simplest assumption states that thearithmetic average of all the measurements taken is very close to the true value andcan be used as measured result. This value is the called the correct value, or some-times the best estimate and can be calculated by the following equation:.

The magnitude of its variation range within which the measured results are found,depends on the quality of the measurements and makes an approximate statementabout the inherent uncertainty of the measurement results (measuring uncertainty).

qn

qii

n

==∑1

1

n = number of individual measurements

qi = result of individual measurements

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The know-how of the technician is used to solve the measurement task in a mannerthat minimizes the number and scope of the undesirable interference effects on themeasurement. In a qualitatively high quality measurement, the variation range mea-surements will be small as will be the measurement uncertainty.

6.1.2 Determining (Estimating) the Measurement Uncertainties

When measuring results are compared, e. g. during a certification test, statements, inaddition to the measured value itself, regarding their reliability are also important. Thespecification of the measurement uncertainty has become established as a measure ofthe quality of the measurement. The determinations the measurement uncertaintymust, in every case, be based on fundamental technical knowledge, i.e. on objectivefacts. Even then the results are subjective, because they are based on judgments usinga number of assumptions and estimates. Such quality judgements will generally beaccepted if the method used to make the judgements is clear. To estimate the mea-surement uncertainty, they are usually divided into two categories:

• Random measurement uncertainties (statistical error effects) and• Systematic measurement uncertainties.

Systematic measurement uncertainties are predictable and correctable. They al-ways occur under the same measuring conditions with the same magnitude and sign.A typical example of a systematic error is calibrating with uncalibrated test equipment.A digital multimeter, which has an error of 0.1 % in its 0.2 V measuring range, willalways indicate a voltage of 199.8 mV when measuring exactly 200 mV; the readingwill be low by -0.2 mV.

A measurement made with this instrument will produce an incorrect result. This mea-surement result can, using the specifications in the instrument’s calibration certificate,be corrected eliminating the systematic measuring error.

Statistical measurement uncertainties are random measurement uncertainties andtherefore their direction and magnitude cannot be predicted or corrected. The magni-tude of the effects can be determined from repeated measurements under the sameconditions can be defined by calculating a distribution curve from the measured results.If the measurement is subject to multiple random error effects, then this fact will alsohave an impact on the distribution curve for the measured values. For three or morerandom error effects it is probable that a normal distribution curve (Gaussian bell curve)will be approached. The descriptor values for a normal distribution curve are its aver-age μ and its standard deviation σ.

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Fig. 6-1: Normal distribution curve (Gaussian bell curve)

Fig. 6-1 shows the typical shape of a normal distribution curve for a constant μ at dif-ferent σ-values. The distribution function p(x) defines the frequency (probability), withwhich the individual measured values Xi will occur within the range of the average μ.For all curves, 68.3 % of all the measured values in the range of ±σ are around theaverage μ; σ therefore makes a qualified statement about the spread of the individualmeasured results. If the σ-range is extended by a factor k (k > 1, confidence factor),then more measured values can be expected to be within this range about the average.

It is customary to use a confidence factor k = 2 for the measurement uncertainty. Usingthis value, one can expect that 95.4 % of all measured values will be within this range(coverage probability of 95.4 %).

Values for the coverage probability P as a function of k

The measurement uncertainty from the viewpoint of GUM (Guide to the Expression of Uncertainty in Measurement)

All previous considerations started from the basis that for every measured value a truevalue exists. In practical measurements true values do not exist, or at last, are un-known. Around 1980, on the initiative of the CIPM (Comité International des Poids etMesures = International Bureau of Weights and Measures, in Sevres near Paris,France) an approach was defined (Recommendation INC-1 (1980)), which is basedtotally on experimentally determined measurements. Therefore, for every measuredresult, there exists a value for a correction to the systematic measurement uncertainty,

k = 1 2 3 4

P(σ) in % 68.3 95.4 99.73 99.994

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always consisting of a value and its associated uncertainty. GUM uses a so-called stan-dard measurement uncertainty and sets it essentially equal to the basic distributioncurve for the measured value. To differentiate, the standard measurement uncertaintyper GUM is designated by the letter u while for the standard deviation, the normaldistribution is usually designated by the symbol σ.

The total measurement uncertainty of a measurement, which is composed of a numberof factors, is usually calculated as the geometric sum (square root of the sum of thesquares) of the individual standard measurement uncertainties. The calculated totalmeasurement uncertainty is usually stated with a confidence interval k, in order toachieve the desired coverage probability.

The GUM method differentiates between two categories for calculating the measure-ment uncertainties:

Type A-Uncertainties are all the uncertainty components of a measurement, whichresult from the repeated measurements method (n independent, observations madeunder the same measuring conditions) and can be described by specifying a numericalstandard deviation (σ-value). Included in the Type A-uncertainties are, e. g. correctionspecifications contained in the calibration reports, for which the distribution function forthe calibration is known or is specified (generally a normal distribution).

Type B-Uncertainties are all the uncertainty components of a measurement, whichcannot be defined after repeated measurements and analysis from the resultant distri-bution function, because of the inability to make repeated measurements. Typical B-uncertainty specifications include, e. g., the measurement accuracy specifications in adata sheet. Here one only knows, that with such an instrument the maximum deviationof the measured values from the true value will be within the error limits stated in thedata sheet. What the probability of a measured value being in the middle or at the limitsof the range is unknown to the user.

Type B-uncertainties are always assumed when concrete value specifications cannotbe made regarding the uncertainties and one therefore has to rely on estimationsbased on experience. Hereby it is necessary that a realistic distribution function isestablished by an analysis of the measuring procedure

Thus GUM uses not only a measurement uncertainty interval to describe contributionsto a measurement uncertainty, but even more probability distributions.

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6.1.3 Measurement Uncertainty Estimations using a Practical Example

A simplified example would be the estimation of the measurement uncertainty for themeasurement of the “true“ temperature in a tube furnace. The temperature of the tubefurnace is determined using a Type S (Pt10%Rh-Pt) thermocouple. The thermocouplewas calibrated and a calibration report is available. The furnace is controlled to atemperature of 1000 °C (1832 °F) by an electronic controller.

The thermal voltage generated by the thermocouple is measured using a digital volt-meter using a measuring location selector switch. The thermocouple has a referencejunction temperature of 0 °C (32 °F). For the thermal voltage measurements a 7 1/2digit instrument with a measuring range of 200 mV is used. The voltmeter was calibrat-ed and a calibration report is available.

The total measurement uncertainty consists of the following measurement uncertainty components

Type B-measurement uncertainty components:

1. The accuracy and stability of the reference junction temperature is estimated at0 °C (32 °F) to be ± 0.1 K. The distribution function of the uncertainties has auniform distribution.

2. The uncertainty, consisting of the non-homogeneities of the thermocouple is esti-mated (results from previous evaluations) to be ± 0.3 K (uniform distribution).

4. The measuring location selector switch produces parasitic thermal voltages (con-tact resistance), which cause errors in the measured value. From the data sheet forthe instrument, maximum parasitic thermal voltage uncertainties of ± 3 μV areused. These correspond to a temperature uncertainty of ± 0.2 K.

5. The uncertainty of the calibration of the thermocouple is specified in the calibrationreport as ± 0.8 K. For this value, a confidence interval of k = 2 has been specified,which yields a probability of > 95 %.

6. The uncertainty in the calibration of the voltmeter is ± 3 μV (k = 2, standard distribu-tion).

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Type A-measurement uncertainty components:

7. The thermal voltage is measured 20 times at approximately 1 minute intervals. Anaverage and the standard deviation of the measured values are calculated.

The resultant standard deviation is ± 4 μV. This value is used as the standarduncertainty of the measurement value acquisition in determining the total measure-ment uncertainty. The variation range of ± 4 μV is caused, among other things, byrandom interferences (electromagnetic interferences, thermal noise, etc.), and alsoincludes time dependent effects due to controller loop variations.

From the calculated average, using the specifications in the calibration reports ofthe thermocouple, the exact oven temperature can be calculated.

Tbl. 6-1: Uncertainty estimation for tube furnace temperature measurements

The measurement uncertainties calculated for the tube furnace from the values spe-cified in the calibration report is ≅ ± 1.3 K. At a confidence factor of k = 2 (coveragerange = 95 %), gives a measurement uncertainty of ± 2.6 K.

No. Description Uncer-tainty(Xi)

k Distribu-tion

Factor for standard

uncertainty

Standard uncertainty

U(Xi)

SensitivityCi

Uncertainty contribu-tion (K)Ui(y)

1 Accuracy and stabilityof the reference junction

0.1 K 1 Normal 1/1.73 0.06 K 1.0 0.06

2 Non-homogeneity of the thermocouple

0.3 K 1 Normal 1/1.73 0.17 K 1.0 0.17

4 Parasitic thermal voltagesof the selector switch

3 μV 1 Normal 1/1.73 1.7 μV 0.05 K/μV 0.09

5 Uncertainty of the thermocouple calibration

0.8 K 2 Standard 1 0.4 K 1.0 0.4

6 Uncertainty of the voltmeter calibration

3 μV 2 Standard 1 1.5 μV 0.1 K/μV 0.15

7 Uncertainty of the measured value acquisition

4 μV 2 Standard 1 4 μV 0.1 K/μV 0.4

1.27

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6.1.4 Error Effects for Temperature Measurements

Basic Considerations

Users always raise the question, what tolerance class is required for a temperaturesensor in order to make the temperature measurements within the required accuracy?Every real temperature sensor has a curve, which deviates more or less from the idealcurve, as it is defined in the standards. Since temperature sensors cannot be manufac-tured to any arteriolar accuracy, the standards define the deviation limits from the stan-dard curves within which the measurements made by a real temperature sensor mustlie. Basically two tolerance classes are defined, an expanded tolerance class (Class Bor Class 2) and a more restrictive tolerance class (Class A or Class 1). There can alsobe other tolerance specifications which are agreed to between the user and the manu-facturer and defined in the purchase order.

Temperature sensors, which meet the requirements for a specific tolerance class, areusually “picked“ from a manufacturing batch. Even the more restrictive toleranceclass A (e. g. for measurement resistors Pt100 according to DIN EN 60751) alwaysinclude some measurement uncertainties (e.g. ± 0.35 K at 100 °C (212 °F) or ± 0.75 Kat 300 °C (572 °F)), which could be unacceptable for precision measurements.

If a special tolerance classification is defined in the purchase order, which is even morerestrictive, it becomes more and more difficult to find a temperature sensor, which canfulfill these requirements. This is especially true if the tolerance limits are to be main-tained over a wide temperature range. Sensors with such narrow tolerance limits aretherefore very expensive.

The accuracy requirements to temperature measurements has increased dramaticallyin recent times. A few years ago, the measurement uncertainty achieved by a Class Asensor element was still “considered to be the one to beat“. Now these accuracies areno longer satisfactory for many applications. The following requirements have becomemore important in recent years:

• Measuring smaller temperature differences between the in- and outlet temperatures of cooling towers (increasing the efficiency of the cooling tower). At the same time, certain maximum outlet temperatures may not be exceeded.

• Measuring the temperature difference between the reactants added in a chemical reactor and the end product of the reaction, for continuous energy balancing as a preventative measures for explosion/process interruption protection.

• Measuring more exactly process temperatures in the pharmaceutical industries during the manufacture and processing of temperature sensitive products.

• Measuring more exactly process temperatures in the sterilization procedures in the milk and dairy product industries (UHT milk).

• Measuring more exactly processing temperatures for sterilization in biochemical systems.

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A very effective method for satisfying the application requirements described above isoffered by the precision calibration of a temperature sensor which initially has somearbitrary tolerance (e. g. Class B). In the calibration report, the relationship between thetemperature and the resistances or thermal voltages established during the calibrationare documented and can be utilized by the user to correct the measuring results.

If the temperature sensor is connected to a programmable transmitter, then the cor-rection factors can be stored in the transmitter. For the user this combination, whoseinput is the temperature measurement itself and whose transmitter output value in mA,behaves like an ideal temperature sensor in accord with the standard. The remainingerror is reduced by an order of magnitude and is only limited by the accuracy of thecalibration itself and the digital resolution of the transmitter (typically between 0.05 Kand 0.1 K). This method provides a cost effective alternative to the expensive selectionof highly precise temperature sensors.

Error effects due to “natural“ uncertainty components of yet unused sensors

As already mentioned, temperature sensors cannot be manufactured to any arbitraryaccuracy. This is in part due to the manufacturing processes and to the purity of thematerials used.

Particularly for non-precious metal thermocouples, the non-homogeneities in the com-position or structure of the alloys can lead to appreciable measurement uncertainties.Non-homogeneities can only have an effect on the measured results when they are inthe range of the temperature gradient. Non-homogeneities can be manufacturing relat-ed, they can be operation related or they can be first noticed in the application phase.Non-homogeneities can lead to errors of several K, and in some special cases, up toseveral hundred K.

Strong mechanical stresses, e. g. severe bending or kinking of the thermocouple wire,can produce non-homogenous sections by changing the material structure. A suitableannealing procedure for the thermocouple wire, in some instances, can reverse thenon-homogeneities to a certain degree.

For thermocouples Type K (NiCr-Ni), as well as for all other thermocouples, which havea NiCr-leg, the effect of the so-called K-Condition should be considered. Before apply-ing, assure that the Type K thermocouples are installed only after they have been sub-jected to a stabilizing annealing (see also chapter 3.5). The measuring error caused bythe K-Condition can be in the order of 2 K to 5 K.

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Error effects, which occur during the operation of the sensor

The accuracy of an unused temperature sensor unfortunately does not remain constantduring its operating life. The temperature sensor experiences aging (drift) (see chapter3.5).

Measurement uncertainty effects, caused by drift, are very difficult for the user torecognize, because their effects occur very slowly and usually go unnoticed. The startof a drift processes and its effects can only be determined by regularly monitoring thetemperature sensor (periodic recalibrations) and quantifying by magnitude and direc-tion (see chapter 6.2.10).

Other contributors to the measurement uncertainties when operating thermocouplesare the small internal resistances of other connected instruments. Thermocouples arehigh resistance sources, thermocouple wires may have resistances of several kΩ.

Connection lead resistances when using resistance thermometers in a 2-wire circuitmust be considered, when they are a non-negligible component of the sensor resis-tance (see chapter 3.6).

The ohmic resistance of the connection leads between the measuring instrument andthe measurement resistor add to the actual measured sensor value. The temperatureindications will be too high. Compensation measures include adjusting the measuringcircuit, or accounting for the connection lead resistance during the signal evaluation. Itis for this reason, that for a resistance thermometer in 2-wire circuit, the connection leadresistance from the sensor element to the connection socket are included in the spec-ifications. It is assumed, that the correction value for the connection lead resistancedoes not vary over the measuring temperature range. The connection leads, howeverare subjected to certain temperature effects, which could change the resistance valueof the connection lead. Therefore this correction may include a certain error compo-nent.

The order of magnitude of real connection lead resistances is shown in the followingtable. Listed are the lead resistance for a 1 m (39”) long pair of connection leads (in andout), made of copper, as a function of the wire cross section.

Tbl. 6-2: Ohmic resistance of a Cu-wire (dblm = double meter) and the resultant measuring error

Wire cross section (mm2) 0.14 0.22 0.5 0.75 1.5

Resistance (Ohm/dblm) 0.638 0.406 0.179 0.119 0.06

Resultant error for Pt100 (K) +1.7 +1.1 +0.5 +0.3 +0.2

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If the connection lead resistances are known, they can be considered when themeasured signal is evaluated. The hard to estimate temperature effect of the connec-tion lead resistance remains as a measurement uncertainty component. This effect canbe essentially eliminated by utilizing resistance thermometers in 3- or 4-wire circuit de-signs.

Parasitic thermal voltages are undesirable voltage components, which are generatedby the different metals and alloys in the measuring circuits at the connection points,when these are in a temperature gradient. They cause errors not only in the resistancemeasurements, but also in the thermal voltage measurements. These metal transitionsoccur primarily at the connection or extension locations for the connection leads of thetemperature sensors.

They can introduce an appreciable temperature load and generate parasitic voltagesat the connection sockets, especially for short measuring insets. A measurement of theparasitic thermal voltages, or a systematic estimation of the errors they cause for apossible correction, is hardly possible. Dependent on the polarity of the generated volt-ages, the measuring error will result in indications too high or too low.

For resistance measurements a polarity reversal of the measuring current is a simplemethod to check the effect of parasatic voltages on the measurement. Two measure-ments are made, one immediately after the other, with the same measuring current, butwith a reversed polarity. If there is an appreciable difference between the two measure-ments, then it is due to parasitic thermal voltage effects. The arithmetic average of thesum of the absolute values of the two measurements is then the error corrected mea-sured value. High precision instruments offer special methods for compensating para-sitic thermal voltages occurring during resistance measurements. Parasitic thermalvoltage effects for resistance measurement can also be completely eliminated by usingan AC voltage bridge.

Error components due to “incorrect“ compensating cables

Thermocouples with long cable lengths, beyond a certain point (ambient temperatures< 200 °C (392 °F) or < 100 °C (212 °F)), are usually elongated with more economicalmaterials, the compensation cables.

The thermal voltages generated by the legs of the thermocouple can differ appreciablyfrom those made of the compensating cable materials. As long as both legs at the con-nection locations to the compensation cables are at the same temperature, no measur-ing error is introduced. However, if the connection locations are in a temperature gra-dient, then errors due the incorrect thermal voltages can result. The extension ofthermocouples using compensating cables is only successful, when compensationcables matched to the thermocouple are installed with the correct polarity.

218

Measuring errors, caused by improperly selected or incorrectly connected compensa-tion cables, can lead to errors of several tens of K. For precision thermal voltage mea-surements, the use of “extended“ thermocouples is generally not recommended.

Error effects when evaluating the measuring signal

All temperature sensors have a nonlinear curve. When converting the measured signalinto a corresponding temperature value, this nonlinearity must be considered. Incorrector not-considered nonlinearities in the curve can lead to measuring errors of several K.If curves are approximated, linearity errors whose magnitude is a function of the degreeof linearization may occur.

An incorrect or not-considered reference junction is a classical error when employingthermocouples. The output signal of a thermocouple is always proportional to the tem-perature difference between the hot and cold ends. Only after the requirement that thetemperature at one end is known can the temperature at the other end be determined.The reference junction is the connection location (the one end of the thermocouple), atwhich a known temperature exists. The reference junction is usually maintained at atemperature of 0 °C (32 °F) by using an ice/water mixture. Other reference junctiontemperatures (20 °C (68 °F), 50 °C (122 °F)) are also common.

For thermocouple measurements with direct indicating measuring instruments, a refer-ence junction is usually integrated in the instrument. The temperature at the connectionterminals of the instrument is continually measured and added to the temperature valuecalculated from the thermal voltage measurements. If the reference junction is not con-sidered, then the measured temperature value is incorrect by the amount equal to theambient temperature.

If an estimated value for the temperature to be measured is not available, then the notconsidered reference junction temperature often remains completely unknown. If thereference junction is taken into account, but with an incorrect value, then the differencebetween the true and the assumed reference temperature values causes an error withthe same order of magnitude on the measured result. The exact measuring error how-ever, is still dependent on the value of the measured temperature.

219

Error effects due to the practical implementation of the measurement task

All considerations to this point have been based on the fact that the temperature of thesensor is the temperature that is to be measured. Thermocouples and resistance ther-mometers are contacting thermometers and must be in good thermal contact with themedium in order to assume its temperature. Contacting thermometers can only mea-sure their own temperature! This seems to be a trivial observation, but it is an importantconsideration when selecting the measurement location in the process.

If the temperature measurements are made at an unsuitable location, then even thoughthe temperature is measured very precisely, the measured value will be of questionablevalue. If the measurement is made at the correct (representative) location, this is stillnot a guarantee that the measurement will be free of systematic error effects.

Incorrect sensor temperatures can result from other reasons. If temperatures which arechanging with time are to be measured, then the dynamics of the temperature sensormust be capable of following the changes. The time response is generally defined bythe response time (τ0) parameter. If the response time is large in comparison to the rateof change of the temperature to be measured, then the result will be a systematic errorbecause the temperature sensor always “lags“ the changing temperature being mea-sured by a certain amount.

The problem of excessive heat loss is also an error source that can occur in actualmeasurements. Behind this occurrence is that fact that contacting temperature sensorscontinuously remove heat from the measured medium to the temperature sensor (hotmeasuring location) and from there to the ambient temperature (through the cold end)of the temperature sensor. In other words, energy is constantly being withdrawn at themeasuring location: it cools. If temperatures are to be measured that are less than thetemperature of the “cold end“, then this process is reversed and energy is added at themeasuring location, it warms.

The magnitude of this heating or cooling is primarily dependent on:

• the insertion depth of the temperature sensor,• the diameter / cross section ratio of the temperature sensor,• the heat transfer of the materials used,• the heat transfer between the medium and sensor,• the temperature difference between the measuring location and the ambient

temperature.

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Fig. 6-2: Dependence of the thermal loss errors to the ratio of the insertion depth to the diameter of a temperature sensor for liquids

From the curve it can readily be seen that a temperature sensor must have a minimuminsertion depth, in order not to exceed a prescribed thermal loss error. In the example,the minimum insertion depth of 5 x the diameter of the inserted temperature sensor isrequired for thermal loss errors of <1 %. For temperature measurements in gases, therecommended value should be at least doubled because of the poorer heat transfer.

Measurement resistors are passive sensors. They must be supplied with a measure-ment current in order to produce a resistance proportional measuring voltage. The cur-rent generates in the measurement resistor a definite power loss with the magnitude

The measurement resistor is actually a small heater element and converts this powerloss into heat. The result is an undesirable temperature increase in the sensor, calledself heating. Therefore the temperature sensor detects a temperature which is higherthan the actual temperature of the medium.

Ploss = I2 * R

0 2 4 6 8 10 12 14

n times insertion depth of the thermometer Ø

Mea

sure

men

t er

ror

[%] 100%

1%

0.1%

0.01%

0.001%

0.0001%

10%

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The magnitude of the self heating is a function of a number of factors:

• the measurement current setting,• the thermal mass of the sensor element,• the removal of the temperature increase by the medium.

For typical measurement currents of 1 mA, the power loss in a 100 Ω measurementresistor is 0.1 mW. For sensors well insulated from the ambient, a self heating effectlarger than 0.5 K can result. This is particularly true in non-moving gases, because theheat transfer to the medium being measured is very low.

In recent times, there is a tendency towards higher standard measurement resistors(Pt200, Pt500, Pt1000), because these, at the same measurement current, producehigher voltages, but also generated more self heating. The errors effects on the mea-sured value increase.

Generally the self heating effects can be reduced by lowering the measurementcurrent. Precision measurements (e. g. for quality calibrations) as a rule are conducedat two different measurement currents, which are different by a factor of √2. The mea-surements are conducted at single and doubled power losses, from which the mea-sured value can be extrapolated to a measurement current of zero. Specifications ofthe self heating behavior for the more common sensor or measurement resistordesigns are given by the manufacturer in the data sheets. The user can then easilyestimate the magnitude of the self heating error for a particular measuring current.There are no self heating effects in a thermocouple.

Temperature sensors, used for the measurement of flowing media, are subjected toappreciable vibration loads. For continuous vibration excitations, the effects of exces-sive resonance conditions can lead to destruction of the entire sensor. Even if noexternal damage is visible on the temperature sensor, vibration loads can prematurelydamage the sensor element. A subtle measuring value deviation (drift) is usually theresult of sensors exposed to high vibration conditions (e. g. exhaust gas sensors forlarge Diesel motors indicate such typical behavior). Special vibration resistant designs,in combination with regular recalibrations, provide corrective measures and operationalsecurity.

The term electromagnetic interferences (EMI) means the presence of undesirableinterference voltages in the measuring circuit, generated by time changing externalelectric or magnetic fields, emanating from electric motors, transformers, power linesor thyristors. Also high frequency radiation can generate electromagnetic interferences.Leak currents, due to damaged electrical heaters, or so-called ground loops can alsoproduce electromagnetic interference in the measuring circuit. The ability to withstandor suppress such interferences is defined as electromagnetic compatibility (EMC).

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The interference due to electrical AC fields can be reduced by adequately shielding theconnection wires. The effects of magnetic induced EMI intervenes on the other handcan hardly be reduced using shielding methods, unless the shield materials are verythick. The only possible solution is to space the measuring circuit and the EMI-sourcesas far apart as possible. If interference is still present, the measurement connectionleads should be routed very close to each other and in parallel if possible. Twisted pairsor coaxial cables provide good protection against AC magnetic fields. Another methodto reduce the interference signals is to shorten the interference sensitive signal pathand transmit the signal over the remaining distance using the mA output signals froma transmitter.

At higher temperatures even the best insulation materials lose their insulation resis-tance properties. The insulation behavior of an ceramic oxide e. g. is reduced byapprox. an order of magnitude for every temperature increase of 100 °C (212 °F).Leakage currents are the result. They are superimposed on the measuring signal andcause errors. Here the use of temperature sensors with grounded metallic protectionsheath is recommended. The leakage current then flows through the grounded sheathand not through the sensor element and its measuring circuit.

The influence of ground loop effects, which are caused by the compensating currentsflowing as a result of the differing ground potentials in a measuring circuit, can also beeffectively suppressed by using grounded metallic sheaths for the temperature sen-sors.

Fig. 6-3: Use of shields to prevent leakage currents

Magnetic field

Large inductionloop area

Twisted connection leads (twisted pairs)

Leak current flows through metallic sheath to earth

Leak current flows in the measuring circuit

Shielded connection lead (coaxial cable)

Small cross section of the induction loop

Reducing the induction loop area reduces the sensitivity to magnetic field interference

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6.2 Calibration and Verification

Temperature sensors are prone to a general aging phenomenon which is usually calleddrift. The magnitude and size of the drift cannot be defined without detailed specifica-tions about the actual installation conditions. Even if these specifications are available,quantifying the drift process is extremely difficult. As a last resort, cyclic measurementtests of the temperature sensor are required to assure, that after long term use, therequired specifications relative to the accuracy are still applicable.

These measurement tests are usually called calibrations. Calibrations are conductedto assure that the high quality level of the temperature sensor is maintained for therequired measurement tasks, even though the sensor itself is subject to a continuousaging process.

6.2.1 Definitions

Calibration in the metrology field:Determination of the deviations of a finished product from the defined design values.The design values are either defined in applicable standards, directives or in otherspecification documents. They can also be defined by separate agreements betweenthe contracting partners.

During the calibration no changes are made to the instrument being tested!

Calibration of a temperature sensor is understood to mean the determination of theirmeasurement deviation. This is the deviation between the output signal of the temper-ature sensor at the calibration temperature, and its design value at that temperature.The calibration only provides information about the deviations of the test object at thetime of the calibration. Information about the time dependency of the accuracy of thetest object during its operating time cannot be provided based on the reasons men-tioned earlier. The calibration results are documented in a calibration report.

Adjusting a measuring instrument:Making changes in an instrument with the goal of either adjusting the settings so thatthe measurement deviation found during the calibration:

• are as small as possible, or

• that their contribution to the measurement deviation after the adjustment no longer exceed the specified error limits.

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Care must be exercised when changing the settings to protect against unintentionalchanges (labels, seal marks, seal paint etc.). Documentation of the adjustments in theform of certificate is absolutely necessary.

Verification according to national standards is understood to be an accredited calibra-tion. Verifications can only be conducted by approved calibration bodies or by test fa-cilities designated by them. Verifications may only be conducted on products whichhave been approved under the verification laws and calibration regulations. Products,which are to be verificated, must have been undergone a design type examination(Test Examination Certificate).

The intent of such a test is to ascertain whether the measurement stability can be main-tained for the duration of the certificate (long term stability) and that protection againstmanipulation exists. The type tests include tests conducted on a number of represen-tative instruments of the same design (first sample tests). If the test objects satisfy therequirements, the product is issued a type examination certificate. The design is then“frozen“.

The actual verification procedure corresponds to a calibration, but only the adherenceto the allowable error limits is measured. The verification is identified by a stamp on theinstrument. Although verification certificate is usually issued, this is not mandatory forall verifications. The values resulting from the calibration are recorded in the verificationcertificate.

6.2.2 Calibration Methods for Temperature Sensors

There are two basic methods for calibrating temperature sensors.

For Fixed Point Calibrations the temperature sensors are exposed to a known tem-perature. This is produced in high purity materials (e. g. metals) which are heated untilthey are completely molten and then cooled slowly. A constant temperature exists dur-ing the transition stage beginning at the moment of solidification. Under ideal processconditions, this equilibrium status, and thereby a constant temperature, can be main-tained for several hours.

In the specifications of ITS-90 values are assigned to these fixed points, which arepractically identical to the thermodynamic temperatures. For the solidification point ofAluminum e.g. the fixed point temperature t90 = 660.323 °C (1220.5814 °F). Fixed pointcalibrations are calibration methods with the smallest measurement uncertainties.However, they are very expensive to conduct.

For Comparison Calibrations (also called comparison measurements) the test objectis exposed to an unknown temperature. This temperature is produced in a so-calledcalibrator. Calibrators can be stirred liquid baths (to approx. max. 550 °C (1022 °F)) or

225

so-called block calibrators. At higher temperatures (especially for thermocouple cali-brations) tube furnaces are usually employed, whose limited thermal properties can beappreciably improved through the use of so-called compensation bodies (metal inserts)or heat pipes.

The function of these calibrators is to produce a selectable temperature within a definedcalibration volume, stable with time, and spatially homogeneous. A so-called compari-son standard is exposed to the temperature together with the test object. The outputsignal from the comparison standard and the test object are measured over an extend-ed period of time. The output signal from the comparison standard is used as a mea-sure of the existing calibration temperature.

Comparison calibrations by nature have higher measurement uncertainties than fixedpoint calibrations. The calibration expense, however, is appreciably less and calibra-tions can be conducted at practically any temperature.

6.2.3 The Traceability of the Calibration

Looking at the comparison calibration it can be recognized, that in a certain sense it isthe transfer of the “accuracy“ (measurement uncertainty) of the comparison standardto the test object. Of course, other measurement uncertainty components also comeinto play. They result e. g. from the measured data acquisition during the calibration orfrom non-homogeneous calibration bath temperatures. The resulting measurement un-certainties of the test object must by necessity be larger than those of the comparisonstandard used. It should be possible to use this test object at another location as a com-parison standard. Each step entails an increase in the measurement uncertainty.

The comparison standards with the least measurement uncertainties, the nationalcomparison standards, are maintained and made available in Germany by PTB, theNational Institute of Technology and Science (Physikalisch-Technische Bundesan-stalt). PTB calibrates to customer order the so-called reference comparison standardagainst the national comparison standard. The reference comparison standards arecomparison standards of the highest order e. g. used in DKD (German CalibrationService) certified calibration laboratories. The factory comparison standards, i.e., thecomparison standards used to continuously conduct the calibrations, are calibratedagainst the reference comparison standards.

The factory comparison standards are used, as a rule, to calibrate the production testequipment used for the manufacturing inspections. A calibration hierarchy exists madeup of a definite number of calibration levels. This calibration hierarchy assures that theresults measured by the production test calibration equipment can be traced back, overa complete set of links, to the national comparison standards. The comparability of allthe calibration results is thereby assured. This concept is called “traceability“. Thetraceability of the measured results is a fundamental requirement of QA Systemsaccording to EN ISO 9000.

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Fig. 6-4: Calibration hierarchy

6.2.4 Suitable Standards

For the test instruments in the various levels of the hierarchy, there are specific require-ments relative to their technical specifications. This is particularly true relative to theirlong term stability and freedom from hysteresis. Towards the peak of the triangle therequirements always become more stringent. Therefore the resistance thermometers,to be used as standard thermometers for representing ITS-90 (the highest level of thepyramid), may only be made of spectral pure Platinum material. Thermometers in thisdesign, are usually used as reference comparison standards in laboratories.

If thermocouples are used as reference comparison standards, only precious metalthermocouples (preferably Type S (Pt10%Rh-Pt)) come into consideration. These ther-mocouples must have an especially homogeneous alloy composition, so that any non-homogeneous temperature distributions which may exist in the calibration oven outsideof the actual calibration area, cannot affect the measured result.

For use as a factory comparison standard resistance thermometers according toEN 60751 are completely acceptable. Even so, they should be selected after an inten-sive preliminary test from the best samples, relative to their stability, freedom from hys-teresis and high insulation resistance, from the spread of normal production runs.Especially in regard to their insulation resistance, the requirements of EN 60751 shouldonly be considered as minimum requirements. A usable thermometer, which shouldprovide good service as a comparison standard, must definitely exceed these require-ments. The industry offers for such applications special designs.

Calibration center

Reference comparison standard

Inner company calibration laboratory

Working comparison standardor factory comparison standard

Test euqipment of the company

Nat.Institutefor me-

trologicalnational

standards

Accreditedcalibration laboratory

Referencecomparison standard

227

6.2.5 The Water Triple Point

Fixed point calibrations are calibrations with the smallest measurement uncertainties.Typical for such measurements are measurement uncertainties in the range from0.5 mK to 5 mK (in temperature ranges: 0.01...660 °C (32.02...1220 °F)). They are alsocalibrations requiring the highest expenditures in equipment and time. Fixed point cal-ibrations are only used in a few calibration laboratories.

The triple point of water is the only fixed point that can be found in practically all highquality calibration laboratories. It is the most important definition point in the ITS-90scale and is used for regular testing of the comparison standard thermometers (refer-ence comparison standards) in the laboratory. The triple point of water has a definedtemperature t90 = 0.01 °C (32.02 °F) at a high precision (measurement uncertainty< 5 mK) and is therefore especially suited for finding the smallest deviations of theresistance of the comparison standard from its design value. Based on the magnitudeof such a deviation, a decision can be made if the comparison standard should berecalibrated or if it can continue to remain in service.

To produce the water triple point a triple point cell is used.

Fig. 6-5: Triple point cell

Since its introduction, ITS-90, has replaced the previously used value for the freezingpoint of water (0 °C (32 °F)) by the water triple point.

Inner tube for thermo-meter insertion

Glass body

Water steam

Water

Ice

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6.2.6 Documenting the Calibration Results

A calibration without documentation is practically worthless. A report or certificateshould be used to document the results of the calibration and its traceability to theNational standards and be in agreement with the International System of Units (SI). Itis the proof of the quality of the calibration object.

In the industrial sector, it also provides quality assurance in a variety of forms. The bestknown is the certificate according to EN 10204 (formerly DIN 50049), which is the rec-ognized form for material configuration and material testing. In addition, quality certifi-cates according to DIN 55350 Part 18, form the certification basis when special qualityrequirements of any type were agreed upon in the purchase order. The named stan-dards regulate which results are to be included in a particular certificate and who hasthe authority to issue such a certificate, but they make no statements regarding its for-mat or any additional contents of the certificate. The contents and formats for the Cal-ibration Certificates of the German Calibration Service DKD however are regulated inscript “DKD-5“.

DKD calibration certificates consist of a cover page, with general specifications for theitem being calibrated, information about the customer and the laboratory performingthe tests. In addition, there are statements relative to the international acceptance ofthe DKD calibration certificates within the framework of the EA (European Cooperationfor Accreditation), which is based on multilateral agreements. The following pages ofthe calibration certificate document the type and calibration method, names the stan-dards used and their traceability, descriptions of the ambient conditions and the resultsof the calibrations.

A complete description of the calibration results includes the measured variable, themeasured value and the measured uncertainty and the total measurement uncertainty.Supplementary statements about the conformity (maintaining the tolerances) can beincluded.

229

A DKD calibration can be recognized by:

DKD-Logo (blue or black)

German Eagle (black)

DKD - Calibration Mark (red)

Laboratory Seal

The DKD calibration mark is also affixed to the calibrated object.

5092

DKD-K-05701

06-01

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6.2.7 The German Calibration Service (DKD)

The German Calibration Service (DKD) is an association of calibration laboratories ofindustrial companies, research institutes, technical authorities, inspection and testinginstitutes. These laboratories are accredited and supervised by the Accreditation Bodyof the German Calibration Service (DKD). They calibrate measuring instruments andmaterial measures for measurands and measurement ranges specified within theframework of accreditation. The DKD calibration certificates issued by these laborato-ries prove traceability to national standards as required by the “standards family” ISO9000 and by ISO/IEC 17025.

The reason for the formation of the DKD in 1977 was an increased demand for trace-able calibrations, which PTB could no longer satisfy, particularly in a timely manner.

The functions are distributed as follows:

Functions of the Accreditation Body:

• Accreditation and monitoring of calibration laboratories:Processing and decisions regarding accreditation requests; monitoring the accredited calibration laboratories; planning, conducting and evaluating round robin comparisons.

• Representing the German Calibration Service (DKD):Cooperation with board, technical committees and expert panels.Cooperation with committees of the German Accreditation Council (DAR), the European Cooperation for Accreditation (EA) and the International Laboratory Accreditation Cooperation (ILAC).Cooperation with national and international standards and control committees for measurement metrology.

• Implementation of new developments:Cooperation in the development of progressive, new monitoring instrumentation (virtual laboratory control; measuring and test equipment); Unified presentation of measurement uncertainties.

Functions of the DKD-Laboratories:

• The calibration laboratories calibrate order based measurement and test equipments.

• They prepare calibration certificates, which numerically document the results of the calibration.

• The calibration laboratories assume responsibility for any resultant damages which can be traced back the errors in the calibration.

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6.2.8 DKD-Laboratories at ABB

The ABB factory in Alzenau, Germany has a DKD calibration laboratory, that wasestablished for the calibration of temperature sensors and is registered under theapproval number DKD-K-05701.

Fig. 6-6: View into the DKD calibration laboratory

DKD calibrations in a temperature range from -35...1200 °C (-31...2192 °F) can beconducted. Included are stirred liquid baths as well as tube ovens with compen-sation blocks. Naturally, water triple point cells are available. For low temperaturerequirements, the possibility of a DKD calibration using liquid Nitrogen (approx. -196 °C(-320.8 °F)) exists.

The most important capital is the experience of the technicians in the laboratory, whohave access to many years of company know how in the field of temperature measure-ment technology.

The laboratory is accredited for calibrations of the following equipment:

• Measurement resistors with suitable extensions (Pt100 and other Ro nominal values according to DIN EN 60751)

• Resistance thermometers according to DIN EN 60751• Thermocouples according to EN 60584 and DIN 43710

(or comparable international standards)• Temperature sensor with connected transmitter• Temperature sensor with direct indicator• Entire measuring chain (sensors + transmitter + transmitter power supply +

indicator).

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The following table provides information regarding the smallest, achievable measure-ment uncertainties, with which the calibrations can be conducted.

Tbl. 6-3: Accreditation scope

Measured variable or calibration equipment

Measuring range°C (°F)

Measuring conditions

Measure-mentuncertainty

Comments

Temperatureresistance thermometers

0.010 (32.018) Water triple point cell 5 mK Triple point of water

-196 (-320.8) Boiling point of liquid Nitrogen (LN2)

100 mK Comparisonagainst standard resistancethermometer

-35...180 (-31...356) Stirred thermostatic liquid bath

20 mK

180...350 (356...662) 20 mK

350...500 (662...932) 50 mK

Precious metal thermocouples

-35...500 (-31...932) 0.5 K

Base metal thermocouples

400...500 (752...932)200...400 (392...752)0...200 (32...392)

1.0 K0.4 K0.2 K

Resistance thermometers

500...850 (932...1562)

Measurement in tube oven (calibration in Na-heat tube in a range 550...1000 °C(1022...1832 °F))

1.0 K Comparison measurement against thermocoupleType S

Precious metal thermocouples

500...1000(932...1832)

1.0 K

1000...1200(1832...2192)

1.5 K

Base metal thermocouples

500...1000(932...1832)

Measurement in tube oven (calibration in Na-heat tube in a range 550...1000 °C(1022...18320 °F))

2.0 K Comparison measurement against thermocouple Type S

1000...1200(1832...2192)

3.0

Precious metal thermocouples with a wire design (dmax ≤ 1 mm)

1554 (2829) Fixed point calibration at the temperature of molten Palladium

2.5 K Melting method

Contacting surface thermometers (resistance ther-mometers and thermocouples)

50...500 (122...932)

Calibration fixture for surface thermometers

0.008 K· t/°C Method of the Ilmenau Inst. with individual test bodyt = temp. in °C

Transmitter with connected resistance thermometer

-35...850 (-31...1562)

Such as resistance thermometers

Uprt + 0.1 K Uprt and UTe are the expan-ded measure-ment uncer-tainties for resistance ther-mometers or thermocouples

Transmitter with connected thermocouple

-35...1200 (-31...2192)

Such as thermo-couples

UTe + 0.1 K

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6.2.9 Conducting a Calibration

A resistance thermometer calibration will be used as an example to describe the actualsteps required by the calibration specifications.

If the aging characteristic of the test object are unknown, then it is checked first. Theresistance of the test object is measured at the water triple point. The test object is heldat a temperature 10...20 K above the highest calibration temperature for several hours.After it is cooled in air, the resistance at the water triple point is measured again. Ifdifferences are observed, which are below a specific stability limit (max. 1 mK for com-parison standard resistance thermometers, approx. 20-30 mK for industrial resistancethermometers), then the actual calibration may be conducted on the test object. If thedifferences are greater than the specified limits, the complete cycle, heating, coolingand measuring of the resistance at the water triple point are repeated a number of times(approx. 3...5 times). The differences of the resistance value must tend towards zero.Thermometers, that do not meet the stability criteria after the aging procedures havebeen conducted, are not, or are only calibrated for a reduced accuracy classification.

For the actual calibration, the test object is installed in the calibration thermostatstogether with the appropriate comparison standard, so that their measuring tips (tem-perature sensitive lengths) are as close together as possible in the middle of thecalibration area. After a temperature equilibrium has become established between thetest objects and the bath, the measured values are recorded. For precision calibrations,the measurements are made using an AC bridge. This method is advantageousbecause it operates by matching the resistances to those of the external comparisonstandards, where the best resolution of the instrument occurs, and also because theparasitic thermal voltages in the measuring circuit are compensated when using an ACcurrent.

The measured values of the test objects and the comparison standards are measuredcyclically. The switching between the measuring channels is made using a low thermalvoltage meter location selector switch. For each measuring channel, a continuos aver-age value is calculated over a defined number of measurements and a standard devi-ation calculated. If the standard deviations for all the measured channels is less than adefined stability criterion, then the measurements values are accepted as the calibra-tion values. This procedure is repeated at each of the calibration temperatures. For on-site calibrations (inspections) an additional comparison standard resistance thermo-meter with know resistance values can be incorporated into the complete measure-ment setup.

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6.2.10 User Advantages offered by the DKD

DKD calibration certificates are recognized by all important industrial countries. Thisfact, from the viewpoint of a global market place, is gaining in importance for exportingcountries. Also, the DKD certificates are recognized as unconditional evidence that thecalibrations were conducted with instrumentation subject to quality audit monitoring.This applies not only to the audits based on the standard family DIN EN ISO 9000 butalso to the audits specified in other standards, for example, KTA 1401, AQAP 4a, MIL-Standard, ASME VDA, QS9000 etc.

With accreditation by the Accreditation Body of the DKD the correctness of the calibra-tion results is assured. DKD calibration certificates provide completely recognizedevidence for legal relief in cases of product liability. The allowed measurement uncer-tainties ascribed to the laboratory must have been certified by measurements (cali-brations of unknown thermometers) within the framework of the accreditation by theAccreditation Body.

The systematic measurement instrumentation calibrations in conjunction with anaccredited DKD calibration laboratory assures the user, among others:

• higher measurement accuracies,• better reproducibility,• possibility for precise setting of the process parameters

(higher process output, reduction of defective product),• preventing process down time,• reducing interruptions.

The calibration of measuring equipment by an approved DKD calibration laboratory isnot a luxury, which one utilizes in conjunction with Quality-Management-System, butprovides the user with tangible financial advantages.

Summary:

Use of a correctly calibrated temperature sensor means reducing defects! Every lot,every batch, every oven charge can only be used in a restricted manner if the cali-brations are conducted using faulty measuring equipment. This costs money andincreases losses.

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Recommendations for Recalibration Intervals for Temperature Sensors

Important Information:The listed time intervals are only recommendations. Dependent on the installation conditions(temperature changes, vibration stresses etc.) and the design of the temperature sensor, recali-brations may be required at other time intervals.

Tempera-ture sensor type

Ambient at-mospheric conditions

Tempe-rature changes

Special conditions

Design Maximum operating tempera-ture°C (°F)

Guidelines for recalibra-tion intervals (months)

Resistancethermo-meter according to EN 60751(wire wound measuring resistors)

Reducing, inert or oxidizing

Noextreme temperature change stresses

Novibration stresses

Metallic or 200 (392) 24

ceramic thermowell

420 (788) 12

In metallicthermowell

660 (1220) 6

850 (1562) 3

In ceramicthermowell

660 (1220) 9

850 (1562) 6

Vibration stresses

Metallic or 200 (392) 12...15

ceramic thermowell

420 (788) 12

In metallicthermowell

660 (1220) 9

850 (1562) 3

In ceramicthermowell

660 (1220) 6...9

850 (1562) 6

Strong orextremetemperature changestresses (tempera-ture-shock)

Novibrationstresses

metallic or 200 (392) 18

ceramic thermowell

420 (788) 12

In metallicthermowell

660 (1220) 6

850 (1562) 3

In ceramicthermowell

660 (1220) 6

850 (1562) 3

Vibrationstresses

Metallic or 200 (392) 12

ceramicthermowell

420 (788) 9...12

In metallicthermowell

660 (1220) 6

850 (1562) 3

In ceramicthermowell

660 (1220) 6

850 (1562) 3

236

Important Information:The listed time intervals are only recommendations. Dependent on the installation conditions(temperature changes, vibration stresses etc.) and the design of the temperature sensor, recali-brations may be required at other time intervals.

Tempera-ture sensortype

Ambient at-mosphericconditions

Tempe-rature changes

Special conditions

Design Maximumoperatingtempera-ture°C (°F)

Guidelines for recalibra-tion intervals(months)

Resistancethermo-meters according toEN 60751(film mea-suring resistors)

Reducing,inert oroxidizing

Noextremetemperaturechangestresses

Novibrationstresses

Metallic or 200 (392) 18

ceramicthermowell

420 (788) 9

In metallicthermowell

660 (1220) 3...6

In ceramicthermowell

660 (1220) 6

Vibrationstresses

Metallic or 200 (392) 12

ceramicthermowell

420 (788) 9

In metallicthermowell

660 (1220) 6

In ceramicthermowell

660 (1220) 6

Strong orextremetemperaturechange stresses (tempera-ture-shock)

Novibrationstresses

Metallic or 200 (392) 15

ceramicthermowell

420 (788) 9...12

In metallicthermowell

660 (1220) 3...6

In ceramicthermowell

660 (1220) 3...6

Vibrationstresses

Metallic or 200 (392) 12

ceramicthermowell

420 (788) 9

In metallicthermowell

660 (1220) 6

In ceramicthermowell

660 (1220) 3...6

237

Important Information:The listed time intervals are only recommendations. Dependent on the installation conditions(temperature changes, vibration stresses etc.) and the design of the temperature sensor, recali-brations may be required at other time intervals.

Temperaturesensor type

Ambientatmosphericconditions

Design Maximumoperatingtemperature°C (°F)

Guidelines for recalibration intervals(months)

Precious metalthermocouplesaccording to EN 60584(Type S (Pt10%Rh-Pt)Type R (Pt13%Rh-Pt))

Reducing,inert oroxidizing

Metallic or

ceramicthermowell

800 (1472) 24

In metallic 1000 (1832) 12

thermowell 1250 (2282) 6...8

In ceramic 1000 (1832) 18

thermowell 1250 (2282) 12

Base metalthermocouplesaccording to EN 60584(Type K (NiCr-Ni)Type N (NiCrSi-NiSi))

Metallic or

ceramicthermowell

700 (1292) 24

In metallic 1000 (1832) 12

thermowell 1150 (2102) 6

In ceramic 1000 (1832) 18

thermowell 1150 (2102) 9...12

Base metal thermocouplesaccording to EN 60584(Type J (Fe-CuNi))

Metallic or

ceramicthermowell

700 (1292) 12...15

In metallic 1000 (1832) 6

thermowell 1150 (2102) 1)

In ceramic 1000 (1832) 9...12

thermowell 1150 (2102) 1)

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6.3 Quality Assurance Measures

Temperature sensors cannot always be brought into contact with the objects to bemeasured without special precautions. Generally, special measures are required toprevent exposure of the sensor to excessive mechanical forces, pressure, impact, ero-sion or vibration and to protect it from chemical attack. In addition, errors due to shuntcurrents or external voltages must be avoided. The temperature sensor is enclosed byprotective materials (connection head, extension tube, thermowell with threaded orflanged connections), that more or less resist the impact of chemical and mechanicalforces. The medium contacting parts, such as the thermowells, must especially be con-sidered.

In the following, the important measures are described. Detailed measures and re-quirements should be discussed with the suppliers of the temperature sensors. Lead-ing manufacturers have experts available and approvals for quality assuring measures.

Confirmation Steps for Special Applications

The applicable German and European regulations, the user and the design specifica-tion require an evaluation of the components. The goal of these evaluations and testsis to prove the quality of the instrument, the safety of its materials and connection joints,and to detect weak spots in the welds of the components.

Requirements and designs for temperature sensors are defined by the specificationsin the regulations. At the very top of the hierarchy are the regulations in the EuropeanPressure Equipment Directive 97/23/EC (AD2000). It has been mandatory since May2002.

Thermowells with threaded and flanged connections or welded thermowells etc. mustmeet the requirements in the Pressure Equipment Directive 97/23/EC (AD2000). Forthese components the directive requires a Certificate of Compliance, see also NAMUR-Recommendation NE80.

239

Regulations – System Based Qualifications

AD Specification Sheet HP 0/TRD201 details the general fundamentals for the design, manufacture and testing of pressurevessels and pressure vessel parts (e. g. thermowells). The manufacturer of pressurevessels or pressure vessel parts must have a HP 0/TRD 201 approval.

EN 10 204:20004Metallic products, types of test certificates

DIN 55 350-18Concepts for certifying the results of quality tests, quality test certificates

ZFP – PersonnelQualification and continued training of ZFP-Personnel relative to test technology fornon-destructive testing and radiation protection

Welder testsaccording to EN 287-1, DGRL 97/23/EG and TRD 201 / AD 2000 HP3

Welding procedure testsaccording to AD2000-HP 5/2

Specifications – Product Based Qualifications

In addition to the general regulations in the national and international standards a num-ber of institutions have issued regulations applicable for special sectors and applicationconditions relative to product and design approvals.

Some examples:

PTB German Institute of Technology and ScienceType test examinations (Ex-Protection) and official monitoring of the measurements (comparison standards)

DKD German Calibration Service is the accreditation body for inspectingthe DKD laboratories

EXAM Mine Experimental Test Section Dortmund-Derne, Germanytype test examinations for explosion protection

VDA German Association of the automotive industry

KTA 1401 Nuclear plants

240

Maritime Approval Associations

GL Germanic Lloyd

LRS Lloyds Register of Shipping

DNV Norske Veritas (Norwegian)

BV Bureau Veritas

NK Nippon Kaiji Kyokai (Japanese)

ABS American Bureau of Shipping

Special Tests (Non-Destructive and Metrological Tests)

Mechanical Tests:

• Vibration tests according to customer and design specificationse. g. for type test examinations with simulated earthquakes and airplane crashes forinstallations in nuclear power plants, determination of the resonance points for instal-lation in flows with vortex shedding, type tests at the resonance points within pre-scribed frequency ranges for shipboard sensor approvals.

• Radiographic testing with max. 200 KV output according to DIN 54111 Part 1, Test-ing Metallic Materials with Roentgen and Gamma Rays. The Roentgen tests are de-signed to detect porosities, voids, cracks, etc. in the basic material and/or the weldseam. The evaluation of the test results for fusion welds in pressure vessels andpressure containing parts is made according to the AD-Specification Sheets HP 5/3and/or EN 25817. The regulations define the criteria for acceptance of defects.

• Pressure tests using gas (up to 200 bar) and water (up to 3000 bar). The externaland internal pressure tests are used to confirm the strength and impermeability of thethermowells and process connections.

• Seal tests using Helium leak test with a leak rate of 1 x 10-9 mbar x 1 x s –1, e. g. forceramic feedthrus. Defects are detected using a leak detector, sniffer probe, meas-uring the pressure drop or drop formation.

• Surface crack detection using fluorescent or dye penetrants according to AD-Speci-fication Sheet HP 5/3

• Hardness test according to Vickers (HV) and Rockwell (HRC) as well as Shore A forelastomers

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Electrical Tests:

• DKD-calibrations from -40...1200 °C (-40...2192 °F), plus the ability to calibrate usingliquid Nitrogen (-195.8 °C (-320.44 °F)) or Palladium at its melting point (1554 °C(2829.2 °F)).

• Factory calibrations from -195.806 (N2) °C (-320.451 °F) to 1554 (Pd) °C (2829.2 °F)

• Response time measurements in water at v = 0.6 m/s and in air at v = 3.0 m/s

• Insulation test to max. 3000 V AC

Test Certifications

• According to DIN EN 10 204Certificates specified in this standard, as a rule, define the material traceability forchemical and physical properties, but can also confirm the properties through tests(e. g. impermeability of pressure strength, temperature tests).

• Test Report 2.1Certification by the manufacturer, that the delivered products are in accord with thespecifications in the order, without information regarding the test results.

• Test Report 2.2Certification by the manufacture of the non-specific (not specified in the order) testresults. Tests can be conducted by production personnel (non-specific tests).

• Inspection Certificate 3.1 Certification of the materials and their testing per the customer specifications or legalregulations by factory specialists, who are designated by the malefactors and areindependent of the production department.

• Inspection Certificate 3.2 Certification by an inspector, who is independent of the production department,designated by the manufacturer and an inspector commissioned by the customer oran inspector named in the legal regulations of the results from the specific tests.

• According to DIN 55350 Part 18Quality test certificates in accord with this standard confirm all possible quality criteriabased on the tests and measurements conducted. Only the most common certifi-cates are described below.

• Quality Test Certificate DIN 55350-18-4.1.1Manufacturer certificate O, without information regarding the test results for non-specific (not specified in the order) tests, e. g. batch values or spot tests, preparedby test personnel designated by the manufacturer (factory specialists).

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• Quality Test Certificate DIN 55350-18-4.1.2Manufacturer certificate O, without information regarding the test results for specific(specified in the order) tests, e. g. batch values or spot tests, prepared by test per-sonnel designated by the manufacturer (factory specialists).

• Quality Test Certificate DIN 55350-18-4.2.1Manufacturer certificate O without information regarding the test results for specific(specified in the order) tests, prepared by test personnel designated by the manufac-turer (factory specialists).

• Quality Test Certificate DIN 55350-18-4.2.2Manufacturer certificate M with information regarding the test results for specific(specified in the order) tests, prepared by test personnel designated by the manufac-turer (factory specialists).

Information: For all test certificates according to DIN 55350 Part 18 the scope of thetest is to defined ahead of time.

Additional Certifications

• Manufacturer DeclarationCertificate of Compliance by the manufacturer for simple electrical equipment ac-cording to EN 50020 Par. 5.4 for intrinsically safe measuring circuits including spec-ifications for the corresponding conditions.

• DKD-CertificateCalibration certificate for temperature sensors, which can only be prepared by des-ignated personnel in accredited DKD-Laboratories (Calibration Laboratories accord-ing to DIN EN ISO/IEC 17025). Tests may only be conducted within the accreditedrange for the specific instruments and comparison standards.

Materials and Procedures

They correspond to the specific, valid international standards, such as e. g. DIN, BS,ASTM, etc. They are also delivered to the customer based on special test and inspec-tion specifications (DIN EN 10204:2005). The inspections can be conducted by thecustomer, by an independent inspection organization (TÜV, LRS, DNV etc.) or by anindependent factory specialist. A very comprehensive quality assurance system existsto assure compliance with the international standards.

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7 Explosion Protection

7.1 Introduction

The explosion protection is regulated worldwide by country specific standards. The glo-bal ABB sales products satisfy these requirements with minor product variations, whichare necessary to satisfy the particular national requirements for explosion protection.This means: the same basic design with approvals for various countries. Using thisapproach, minor product variations for worldwide marketing, the user can install thesame product worldwide. This strategy leads to cost reductions on the customer’s part,e.g. training, planning and maintenance of these products.

Tbl. 7-1: Overview of the more important country specific standards, approvals and approval agencies

At their core, the requirements for the approvals are very similar and have a commongoal, that, based on the present state of the technology, an explosion cannot occur ina system, in which instrumentation was used which was designed in accord with thenational requirements for explosion protection.

EuropeanUnion

USA Canada Russia Ukraine Australia

Regulations/Standard/ApprovalAgency

ATEX– PTB– EXAM

BBG– KEMA– TÜV North– ZELM– IBExU...

FM EXApprovalUL EXApproval

CSACertificate

GOSTRussia

GOSTUkraine

IECEX

Validity No restrictions

No restrictions

No restrictions

Approx. 5 years

Approx. 5 years

No restrictions

ProductionMonitoring/Audits

Yes Yes Yes No No Yes

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7.2 Terms and Definitions

ExplosionExplosion means an exothermic reaction of a material which occurs at a high reactionrate. This requires the presence of an explosive mixture/atmosphere and an ignitionsource, as well as external impetus to initiate the explosion.

Explosion hazardExplosion hazard means the presence of an explosive mixture/atmosphere, without ig-nition occurring from an ignition source from an external impetus.

Explosive gas atmosphereMixture with air, under atmospheric conditions, of flammable substances in the form ofgas or vapour, in which, after ignition, permits self-sustaining flame propagation.

Explosion limitsThe lower (LEL) and upper (UEL) explosion limit defines the range of a mixture in whichit is explosive. The limits can be found in the appropriate literature for the particularmaterials.

Explosion groups according to EN-standardsThe ignition and ignition penetration characteristics of an explosive mixture are typicalmaterial properties. These specifications are especially important in the design ofequipments. For Intrinsic Safety electrical equipments the ignition energy is the crite-rion for the ignitability. The smaller the required ignition energy, the more dangerous isthe mixture. The ignition penetration characteristics provides information relative to theflame path width and length limits for the equipments with flameproof enclosure.

Tbl. 7-2: Explosion groups according to the EN-standards

Explosion Group Ignition Energy Test Gas Area

I < 200 μJ1) Methane in air Firedamp protection(Mining)

II AII BII C

< 160 μJ1)

< 60 μJ1)

< 20 μJ1)

Propane in airEthylene in airHydrogen in air

Explosion protection

1) Doubling of the energy values is permissible, when the charging voltage < 200 V.

245

Gases and vapors are classified by the criteria listed below. The table ranks a numberof materials. The equipment to be used for these materials must be qualified accord-ingly.

Tbl. 7-3: Material rankings according to explosion group

Flash PointIs the lowest temperature at which the liquid under test, under defined conditions,produces vapors in a quantity sufficient to form a flammable mixture above the liquidsurface when combined with air.

Ignition Energy The minimum ignition energy is the energy contained in a spark which is sufficient toignite the surrounding explosive atmosphere.

Ignition Temperature according to EN-standardsThe ignition temperature of a flammable material is the lowest temperature, determinedin a test instrument with a heated wall, at which the mixture of a flammable materialmixed with just ignites.

The ignition temperatures of liquids and gases are determined by the proceduresdescribed in DIN 51794. For determining the ignition temperature of flammable dust,no standardized procedures exist at this time. There are a number of procedures listedin In the relevant literature.

ExplosionGroup

Ignition Temperature

T1 T2 T3 T4 T5 T6

I Methane

II A AcetoneEthaneEthyl acetateAmmoniaBenzine (pure)Acetic acidMethanolPropaneToluene

Ethyl alcoholi-Amylacetaten-Butane n-Butyl alcohol

BenzineDiesel fuelAircraft fuelHeating oiln-Hexane

AcetaldehydeEthyl ether

II B Carbon monoxide

Ethylene Sulphurdi-Hydrogen

Ethyl etherButyl ether

II C Hydrogen Acetylene Carbon disulphide

246

The flammable gases and vapors of flammable liquids are classified in TemperatureClasses by their ignition temperatures, and equipment by its surface temperature.

Tbl. 7-4: Temperature classes

Ignition SourcesThe following list showes some of the common ignition sources found in applications:

• hot surfaces (heaters, hot equipment, etc.),• flames and hot gases (from fires),• mechanically produced sparks (by rubbing, impact and grinding processes),• arcs from electrical equipment,• compensation currents,• static electricity,• lightning, ultrasonic,• optic ignition sources,• electric fields from radio waves,• ...

Primary and Secondary Explosion Protection When preventing explosions the terms primary and secondary explosions are used.

The primary explosion protection is based on preventing the formation of a dangerousexplosive atmosphere, i.e.:

• avoiding flammable liquids and gases,• increasing the flash point,• prevention of an explosive mixture by concentration limitations,• ventilation or open area installations,• concentration monitoring with emergency shut down procedures.

Temperature Class Maximum allowablesurface temperature ofthe equipment in °C (°F)

Ignition temperaturesof the flammable materials in °C (°F)

T1T2T3T4T5T6

450 (842)300 (572)200 (392)135 (275)100 (212)85 (185)

> 450 (842) ...> 300 (572) ≤ 450 (842)> 200 (392) ≤ 300 (572)> 135 (275) ≤ 200 (392)> 100 (212) ≤ 135 (275)> 85 (185) ≤ 100 (212)

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The secondary explosion protection encompasses all measures which prevent or avoidthe ignition of a hazardous atmosphere, i.e.:

• No active ignition source- Intrinsically safe equipment- Encapsulating the ignition source to prevent external ignition

Powder filledFlameproofPressurized

Area/zones categories according to IEC standard (EN 60079-10)

Hazardous areas are classified into zones based upon the frequency of the occurrenceand duration of an explosive gas atmosphere, as follows:

For Gases, Vapors and MistsZone 0: place in which an explosive atmosphere consisting of a mixture with air of

flammable substances in the form of gas, vapour or mist is present continu-ously or for long periods or frequently.Category: 1 G

Zone 1: place in which an explosive atmosphere consisting of a mixture with air offlammable substances in the form of gas, vapour or mist is likely to occur innormal operation occasionally.Category: 2 G

Zone 2: place in which an explosive atmosphere consisting of a mixture with air offlammable substances in the form of gas, vapour or mist is not likely to occurin normal operation but, if it does occur, will persist for a short period only.Category: 3 G

For DustZone 20: area in which an explosive atmosphere consisting of a flammable dust and

air in the form of a cloud is always present, over long periods of time, or isoften present.Category: 1 D

Zone 21: area in which during normal operation an explosive atmosphere consistingof a flammable dust and air in the form of a cloud can form.Category: 2 D

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Zone 22: area in which during normal operation an explosive atmosphere consistingof a flammable dust and air in the form of a cloud generally does not formand if it does, then only for a short time.Category: 3 D

Comments:Coatings, deposits and settling of flammable dust, as well as every other cause,must be considered because they can lead to the formation of a hazardous,explosive atmosphere.

The status for normal operation is defined as operation within the design para-meters for the system.

Apparatus for Category 1G/1D, Instrument Group II

Categories 1G (gas) and 1D (dust) include apparatus, that is designed so that it can beoperated to correctly measure the variables required by the user and provide a veryhigh degree of safety.

Apparatus for these categories are suitable for use in Zone 0 (1G apparatus) and inZone 20 (1D apparatus). Apparatus in these categories must, even for rarely occurringinstrument faults, assure that the required degree of safety exists and therefore mustinclude explosion protection measures so that

• even if one type of protection fails, at least the other type of protection assure the required safety,or

• if two types of protection fails the required safety is assured.

The apparatus in this category must also comply with the extensive requirements inAnnex II, Number 2.1 of the EU-Directive 94/9/EG.

Apparatus for Category 2G/2D, Instrument Group II

Categories 2G (gas) and 2D (dust) include apparatus, that is designed so that it can beoperated to correctly measure the variables required by the user and provide basic de-gree of safety.

Apparatus for these categories is suitable for use in Zone 1 (2G apparatus) and inZone 21 (2D apparatus). The explosion protection measures for this category assuresthat even during frequent instrument failures or fault conditions, which can usually beexpected, the required degree of safety is assured.

249

Apparatus for Category 3G/3D, Instrument Group II

Categories 3G and/or 3D include apparatus, that is designed so that it can be operatedto correctly measure the variables required by the user and provide basic degree ofsafety.

Apparatus for these categories is suitable for use in Zone 2 (3G apparatus) and inZone 22 (3D apparatus) for a short period of time. Apparatus for the category assuresthe required degree of safety during normal operation.

DIV Categories according to NEC500 (USA) and CEC Annex J (Canada)

In addition to the categories Zone 0 and Zone 1 for European instrumentation forexplosion hazardous areas, there are Division categories defined in NEC500 and CECAnnex J. The following table provides an overview of the Zones and Divisions.

Tbl. 7-5: Comparison of Zone and Division Classifications

IEC Classifications according to IEC 60079-10EU Classifications according to EN60079-10US Classifications according to ANSI/NF PA70 National Electrical Code Article 500 and/or 505CA Classifications according to CSA C22.1 Canadian Electrical Code (CEC)Section 18 and/or Annex J

Explosion Groups according to NEC500 (USA) and CEC Annex J (Canada)

Tbl. 7-6: Explosion groups according to US/CA-standards

IEC / EU Zone 0 Zone 1 Zone 2

US NEC505 Zone 0 Zone 1 Zone 2

US NEC500 Division 1 Division 2

CA CEC Section 18 Zone 0 Zone 1 Zone 2

CA CEC Annex J Division 1 Division 2

Explosion groupsUS NEC500CA CEC Annex J

Explosion groupsUS NEC505CA CEC section 18EU IEC

Test gas Area

Mining I Methane Firedamp protection(Mining)

Class I Group DClass I Group CClass I Group AClass I Group B

II AII BII CII B + Hydrogen

PropaneEthyleneAcetyleneHydrogen

Explosion protection

250

Temperature Classes according to NEC500 (USA) and CEC Annex J (Canada)

Tbl. 7-7: Temperature classes according to US/CA-standards

Max. surface temperatures US NEC505CA CEC section 18EU IEC

US NEC 500CA CEC Annex J

450 °C (842 °F)300 °C (572 °F)280 °C (536 °F)260 °C (500 °F)230 °C (466 °F)215 °C (419 °F)200 °C (392 °F)180 °C (356 °F)165 °C (329 °F)160 °C (320 °F)135 °C (275 °F)120 °C (248 °F)100 °C (212 °F) 85 °C (185 °F)

T1T2

T3

T4

T5T6

T1T2T2AT2BT2CT2DT3T3AT3BT3CT4T4AT5T6

251

7.3 Types of Protection in Europe and in North America

Ignition Type “Intrinsic Safety - Ex i“ according to EN 50020 or EN 60079-11

Type of protection based on the restriction of electrical energy within apparatus and ofinterconnecting wiring exposed to the potentially explosive atmosphere to a level belowthat which can cause ignition by either sparking or heating effects.

Fig. 7-1: Intrinsic safety schematic

There are two categories of Intrinsic Safety.

Category "ia" for installations in Zone 0:The instruments must be designed so that during a fault condition or during all possiblecombinations of two fault conditions, ignition is impossible.

Category "ib" for installations in Zone 1:The instruments must be designed so that during one fault condition ignition is impos-sible.

R L

U C

Explosionhazardous atmosphere

252

Ignition Protection Type “Flameproof Enclosure Ex - d“ according to EN 50018 or EN 60079-1

Enclosure in which the parts which can ignite an explosive atmosphere are placed andwhich can withstand the pressure developed during an internal explosion of an explo-sive mixture, and which prevents the transmission of the explosion to the explosiveatmosphere surrounding the enclosure.

Fig. 7-2: Flameproof enclosure schematic

Ignition Protection Type “Increased Safety Ex e“ according to EN 50019 or EN 60079-7

Type of protection applied to electrical apparatus in which additional measures are ap-plied so as to give increased security against the possibility of excessive temperaturesand of the occurrence of arcs and sparks in normal service or under specified abnormalconditions.

Fig. 7-3: Increased safety schematic

s wl

Explosionhazardous atmosphere

Chink s

Explosionhazardous atmosphere

253

Ignition Protection Type “Potted Encapsulation Ex m“ according to EN 50028 or EN 60079-18

Type of protection whereby parts that are capable of igniting an explosive atmosphereby either sparking or heating are enclosed in a compound in such a way that the explo-sive atmosphere cannot be ignited under operating or installation conditions.

Fig. 7-4: Potted encapsulation schematic

Ignition Protection Type “Non-Sparking Equipment – n“ according to EN 50021 or EN 60079-15

Type of protection applied to electrical apparatus such that, in normal operation and incertain specified abnormal conditions, it is not capable of igniting a surrounding explo-sive gas atmosphere.

Fig. 7-5: Non-sparking electrical equipment schematic

Explosionhazardous atmosphere

Zone 2

n

254

Approvals according to FM Approval Standard Class Number 3610, 3611 and 3615

Temperature products from ABB satisfy, dependent on the specific certification andapplication area, one or more of the following FM standards:

• Intrinsically Safe Apparatus and Associated Apparatus for use in Class I, II, and III, Division 1, and Class I, Zone 0 and 1. Hazardous (Classified) Locations. Approval Standard Class Number 3610.

• Non-incendive Electrical Equipment for use in Class I and II, Division 2, and Class III, Divisions 1 and 2.Hazardous (Classified) Locations. Approval Standard Class Number 3611.

• Explosion proof Electrical Equipment General Requirements.Approval Standard Class Number 3615.

The corresponding operating instructions and control drawings are to be consideredwhen installing the instrument. In addition, the requirements of the National ElectricalCode (NEC) must be observed.

Approvals according to CSA-standards

Temperature products from ABB satisfy, dependent on the specific certification andapplication area, one or more of the following CSA standards.

• CAN/CSA-E60079-11:02 Electrical apparatus for explosive gas atmospheres -Part 11: Intrinsic safety "i" C22.2 No.213-M1987 (Reaffirmed 1999) Non-incendive Electrical Equipment for use in Class I, Division 2. Hazardous Locations.

• C22.2 No. 30-M1986 (Reaffirmed 1999) Explosion-proof Enclosures for use in Class I. Hazardous Locations.

The corresponding operating instructions and control drawings are to be consideredwhen installing the instrument. In addition the requirements of the Canadian ElectricalCode (CEC) Part I (Safety Standard for Electrical Installation) must be observed.

Approvals according to GOST and other Approvals

The certifications according to these national standards are based on the EC-TypeExamination Certificates and their associated test reports. Generally, additional testsare not required. The different agencies and institutes recognize the test reports. Somecertificates however, have expiration limits, requiring increased efforts to maintain thecertifications current for the products.

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7.4 Marking of the Apparatus

Apparatus for use in explosion hazardous areas must be clearly marked by themanufacturer. The following marking according to EN 50014 or EN 60079-0/EN 50020or EN 60079-11 are to be used:

• Name and address of the manufacturer• CE-Mark • Identification of the series and the type• If applicable, the serial number• Year of manufacture • Special mark for preventing explosions, in conjunction with the mark which

identifies the category• For the Group II the letter “G“ (for explosive gas atmosphere) and/or the letter “D“

(for explosive dust atmosphere).

Up to three nameplates are used on the temperature products from ABB for identifyingthe required marks:

• Typeplate with the important information for the product• Approval typeplate with all the applicable explosion marks• Optional label for additional information.

256

Design and Content of Typeplates for Temperature Products from ABB

[Company Logo, Manufacturer] [Product name] [Country of manufacture] [Year of manufacture]

[Product name + Order Code] [Order No.+ Item No.] [Instr. Man. Logo] [CE Logo][Serial No.] [HW-Revision][Technical Specifications U, I, P ] [SW-Revision][Transmitter CFG][Sensor CFG][Ambient temperature range, standard] [Protection Class]

Information: The temperature specifications are only listed on the typeplate fornon-Ex-versions.

Example: Temperature transmitter type TTH300

Example: Temperature sensor type TSP121

AutomationProducts GmbH 2008

TTH300

U = +11...42 V, I = 4...20 mA, HART

CFG: 2 x TC; Type K; 0°C...300°CS a

T = -40°C...+85°Camb

O-Code: TTH300-Y0/OPT 8323455672

Ser.-No: 3452345673

www.abb.com/temperature

Made in Germany

HW-Rev: 1.05SW-Rev: 01.00.00

2008

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Design and Content of an Approval Typeplate for Temperature Products from ABB

• Company Logo• Manufacturer information• Product name (+ Approval name, if different than product name)• Approval specifications incl. Approval Logo

– ATEX EEx i; Approval specifications according to EC-Type Examination Certificate

– ATEX EEx d; Approval specifications according to EC-Type Examination Certificate

– ATEX EEx D; Dust Ex, Approval specifications according to EC-Type Examination Certificate

– FM; Approval specifications according to Certificate of compliance– CSA; Approval specifications according to Certificate of compliance– GOST; Approval specifications according to Certificate of compliance

• CE 0102 Logo with No. of the Test Agency for ATEX typeplates• Allowed ambient temperatures

Example: Temperature transmitter TTH300 in design EEX "i"

Example: Temperature sensor TSP121 in design Dust-EX

AutomationProducts GmbH TTH300

Tamb. = -40°C ... +84°C (Zone0) ... +85°C (Zone1)Tamb. = -40°C ... +56°C (Zone0) ... +71°C (Zone1)Tamb. = -40°C ... +44°C (Zone0) ... +56°C (Zone1)

PTB 05 ATEX 2017 XII 1 G EEx ia IIC T6II 2(1) G EEx [ia]ib IIC T6II 2G (1D) Ex [iaD] ib IIC T6

2008

Made in Germany

0102

T1...T4T5T6

2008

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7.5 Evidence of the Intrinsic Safety

When interconnecting intrinsically safe circuits according to EN60079-14 an evidenceof the Intrinsic Safety is to be maintained.

There are two categories:

1. Simple intrinsically safe circuit with only one active, associated and one passiveintrinsically safe apparatus without additional power supply.

2. Multiple active apparatus, which during normal operation or during a fault condition can supply electric energy to the intrinsically safe circuit.

Simple Intrinsically Safe Circuits

They can be checked by an authorized person by comparing the electrical connectionvalues from the respective EC-Type Examination Certificate.

The Intrinsic Safety of the connections is maintained, when the following conditions aresatisfied:

Fig. 7-6: Schematic of a simple intrinsically safe circuit

Intrinsically safe equipment plus cablee.g. ABB-transmitter

Associated equipmente.g. transmitter power supplies/SPC input

UiIiPi

Li + Lc (cable)Ci + Cc (cable)

≥≥≥≤≤

UoIoPoLoCo

Field (explosion hazardous area) Control room (safe area)

Transmitter Isolated transmitterpower supply/SPC-Input

259

The verification should be clearly documented. In addition to the date and name of thetester, system specific documentation should be included, i.e., circuit description, ter-minal strips, cable routing, switch and terminal housings, etc.

Interconnection of Multiple Active Apparatus

This differs fundamentally from the previous case. For example, if the interconnectionof multiple active, category “ia“ intrinsically safe circuits results in the combined circuitbeing classified as a category “ib“ circuit, then operation in Zone 0 is no longer possible.

A detailed explanation of this type of connection can be found in Annexes A and B ofEN60079-14. Additionally, the ignition limit curves in EN 60079-11 or EN50020 will berequired. See also EN 60079-25.

The advanced handling of this subject is usually the responsibility of qualified per-sonnel and is not included in this handbook.

Connection of Intrinsically Safe Circuits with Non-Linear Curves

Here special procedures must be followed. They are described in detail in EN 60079-25.

The advanced handling of this subject is usually the responsibility of qualified personnel and is not included in this handbook.

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8 SIL - Functional Safety in Process Automation

The standards IEC 61508 and IEC 61511 provide risk assessment methods for thedesign of safety loops. They define four safety levels, which describe the measures forrisk assessment for the system elements. In order to determine the SIL-Level (SafetyIntegrity Level) of an instrument, all field instruments are subjected to rigorous test re-quirements and analysis by IEC.

The European Union sets the EU-Directive 96/82/EU (Sevesco II-Directive) as the legalbasis for the operation of systems with hazard potentials. The implementation of theDirective 96/82/EU follows from the Incident Regulation in the Federal Imission ControlLaw (12.BlmSchV) dated 26 April 2000.

The Incident Regulation required reference, prior to the issuance of the safety relevantequipment, to DIN 19250 and 19251 until 31 July 2004, in which the requirementclasses AK 1-8 are described. After 1 August, the Incident Regulation references DINEN 61508 as well as DIN EN 61511, whose content corresponds to the Standards(IEC 61508/IEC 61511). They define four Safely Levels (SIL1 to SIL4), which define therisk assessment of system elements and from which the field instruments and actuatorsmust be designed.

In order to estimate, if an instrument is satisfactory for a specific SIL-Level in the safetychain, the field instruments are tested and analyzed by an independent Institution.

In the FMEDA-Test (Failure Mode, Effect and Diagnosis) the hardware structure of theelectronics is investigated. Together with the considerations of the (electro) mechanicalcomponents, the failure rate for the instrument, e.g. temperature transmitter can bedetermined. Essentially, the basic characteristics are utilized, which are calculatedfrom the FMEDA: the Hardware Fault Tolerance (HFT), the percentage of safe failures(SFF Safe Failure Fraction) and the Probability of Failure on Demand (PFD).

The software development process of SIL certified temperature transmitters is definedin IEC 61508 which, in addition, utilizes the requirements in ICE 61511.

Additional general safety considerations for the field instruments are evaluated. In theSIL-Certificate of Compliance, which is issued by the manufacturer, in order to supportthe customers in the selection of suitable instruments for the safety circuits, the classi-fications are always based on the lowest SIL level.

261

To safely operate a system, an additional step is required by the IEC regulations whichtakes into account the entire safety circuit, consisting of the sensor/transmitter, con-troller and actuators, and assigns a SIL level. Before a safety circuit is designed andcalculated, a SIL assessment is carried out, which is used to determine the requiredsafety level for the safety circuit (e. g. SIL2). ABB offers a software program which canbe used for all aspects of the system certification from a SIL assessment up to thedesign and calculation of the safety circuit according to IEC 61508. It also records andstores all decisions and basic calculations.

For operation, the safety circuits must also be regularly checked relative to their safetyfunctions and the results recorded. For these checks, it is required that the test routinesare defined, conducted and recorded. An expensive process, but which in the end isbeneficial to humans and the environment. In addition to an extensive portfolio of in-struments, ABB offers a software program, which manages and processes the data forstatistical analysis for all the test routines and test results prescribed in IEC 61508.

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9 Standards and Regulations for Temperature Measurements

The standardization of electrical thermometers is difficult because of their wide spreaduse in process measurement technology and the large variety of design types, butextremely important. The standardization of electrical thermometers is therefore prima-rily limited to the specification of:

• Basic values• Electrical interfaces• Mechanical interfaces (process connections)• Special characteristics

For the process measurement sector, the creation of national standards for tempera-ture sensors is the responsibility (in Germany) of Subcommittee 961.1 “ElectricalTransmitters“ of the Committee 9.61 “Sensors and Devices“ in Department 9 “ControlTechnology“ associated with the German Electrical Commission (DKE). For very spe-cial applications other bodies are in part responsible.

Standards are prepared at the European (CENELEC) or international (IEC) level aswell at other comparable bodies (see Tbl. 9-1).

Tbl. 9-1: Classification of national and international standards activities for temperature sensors

International European National (Germany)

International Electrical Commission (IEC)

Technical Bureau (BT)CENELEC

German Electrical Commission (DKE)

Technical Committee (TC) 65:“Industrial Process

Measurement and Control“

Reporting SecretariatFor IEC TC 65

Department (FB) 9:“Process Control“

Subcommittee (SC) 65B:“Devices“

Working Group (BTWG) orTask Force (BTTF)

(Project based)

Committee (K) 961:“Sensors and Devices“

Working Group (WG) 5:“Temperature Sensors“

Subcommittee (UK) 961.1:“Electr. Measuring Primaries“

263

The most important national standard bodies for other countries:

USA ANSI American National Standards InstituteCanada CSA Canadian Standards AssociationFrance NF Normalisation FrancaiseGr. Britain BSI British Standards InstitutionJapan JIS Japanese Industrial StandardsRussia GOST National Standards of the Russian FederationItaly UNI Uniticazione Nazionale Italiano

Standards Temperature Measurements:

EN 50112 Measurement, control, regulation – Electrical temperature sensors – Metal Thermowells for Thermocouples Assemblies

EN 50212 Connectors for Thermoelectric Sensors

New draft: Draft proposal for DIN EN 50466 Straight Thermocouples withMetal or Ceramic Thermowells and AccessoriesTo replace the following standards:DIN 43729 , DIN 43733, DIN 43734

EN 60751 Industrial Platinum Resistance Thermometers and Platinum Resistance Wires

New draft: Draft proposal for DIN IEC 60751 2005, being voted on

EN 60584-1 Thermocouples Part 1: Reference Tables: Basic values for the thermal voltages

EN 60584-2 Thermocouples Part 2: Tolerances

New draft: Draft proposal for DIN IEC 60584-3 Thermocouple Wires and Compensating Cables

EN 61152 Dimensions of Metal-Sheathed Thermometer Elements EN 61515 Mineral Insulated Thermocouple Cables and sheathed

Thermocouples

DIN 16160 Thermometers; ConceptsDIN 43710 Thermal Voltage and Materials for ThermocouplesDIN 43712 Thermal Wires for ThermocouplesDIN 43713 Wires and Stranded Wires for Compensation and Extension

CabIesDIN 43714 Compensating Cables for ThermocouplesDIN 43720 Metal Thermowells for ThermocouplesDIN 43722 Thermocouples; Part 3: Thermocouple Wires and Compensating

Cables; Tolerances and Identification System

264

DIN 43724 Measurement and Control; Electrical Temperature Sensors; Ceramic Thermowells and Holding Rings for Thermocouples

DIN 43725 Electrical Temperature Sensors; Thermocouple Insulating TubesDIN 43729 Measurement and Control; Electrical Temperature Sensors;

Connection Heads for Thermocouples and Resistance Thermometers

DIN 43732 Measurement and Control; Electrical Temperature Sensors;Thermocouple Wires for Thermocouples

DIN 43733 Measurement and Control; Electrical Temperature Sensors;Straight Thermocouple without Exchangeable Measurement Insets

DIN 43734 Measurement and Control; Electrical Temperature Sensors;Stop Flanges for Thermocouples and Resistance Thermometers

DIN 43735 Measurement and Control; Electrical Temperature Sensors;Measurement Insets for Thermocouple Sensors

DIN 43762 Measurement and Control; Electrical Temperature Sensors;Measurement Insets for Resistance Thermometers

DIN 43764 Measurement and Control; Electrical Temperature Sensors;Straight Thermometers with Interchangeable Measurement Inset

DIN 43765 Measurement and Control; Electrical Temperature Sensors;Threaded Stem Thermometers with G 1/2 Mounting Threads

DIN 43766 Measurement and Control; Electrical Temperature Sensors;Threaded Stem Thermometers with G 1 Mounting Threads

DIN 43767 Measurement and Control; Electrical Temperature Sensors;Welded-Stem Thermometers

DIN 43769 Measurement and Control; Electrical Temperature Sensors;Thermometers not Fitted with Thermowells

DIN 43771 Measurement and Control; Electrical Temperature Sensors;Thermometers with Fast Response

DIN 43772 Control Technology - Thermowells and Extension Tubes forLiquid-in-Glass Thermometers, Dial Thermometers, Thermocouples and Resistance Thermometers - Dimensions,Materials, Testing

DIN 43772 Control Technology - Thermowells and Extension Tubes forSupplement 1 Liquid-in-Glass Thermometers, Dial Thermometers,

Thermocouples and Resistance Thermometers - General Review - Assignment Thermowell/Temperatur Sensor

VDI/VDE 3511-1 Technical Temperature Measurements - Basics and Overviewfor Special Temperature Measurement Procedures

VDI/VDE 3511-2 Technical Temperature Measurements - Contacting Temperature Sensors

VDI/VDE 3511-3 Technical Temperature Measurements - Measuring Proceduresand Measurement Processing for Electric Contacting Temperature Sensors

265

VDI/VDE 3511-4 Technical Temperature Measurements - Radiation ThermometryVDI/VDE 3511-5 Technical Temperature Measurements - Installation of

Temperature SensorsVDI/VDE 3522 Time Performance of Contacting Temperature Sensors

Explosion Protection Standards, Safety Standards for Combustion Plants, Heat Quantity Measurements

EN 60079-10 Electrical Apparatus for Explosive Gas Atmospheres Part 10:Classification of Hazardous Areas

EN 60079-14 Electrical Apparatus for Explosive Gas Atmospheres Part 14:Electrical Installations in Hazardous Areas (Other than Mines)

EN 60079-17 Electrical Apparatus for Explosive Gas Atmospheres Part 17:Inspection and Maintenance of Electrical Installations inHazardous Areas (other than mines)

EN 1434-1 Heat Meters - Part 1: General RequirementsEN 1434-2 Heat Meters - Part 2: Construction RequirementsEN 1434-3 Heat Meters - Part 3: Data Exchange and InterfacesEN 1434-4 Heat Meters - Part 4: Type Approval TestsEN 1434-5 Heat Meters - Part 5: Initial Verification TestsEN 1434-6 Heat Meters - Part 6: Installation, Commissioning, Operational

Monitoring and MaintenanceEN 14597 Temperature Control Devices and Temperature Limiters for

Heat Generating SystemsReplaces DIN 3440

DIN 3440 Temperature Control and Limiting Devices for Heat GeneratingSystems; Safety Requirements and Testing

International Standards

IEC 60584-1 Thermocouples - Part 1: Reference tablesIEC 60584-2 Thermocouples - Part 2: TolerancesIEC 60584-3 Thermocouples - Part 3: Extension and Compensating Cables -

Tolerances and identification systemIEC 60751 Industrial Platinum Resistance Thermometer SensorsIEC 61152 Dimensions of Metal Sheathed Thermometer ElementsIEC 61515 Mineral Insulated Thermocouple Cables and Thermocouples

266

10 Appendix 1

Application conditions for thermowell materials

Material Max. Temp.no pressure°C (°F)

Advantages Disadvantages

Metal thermowells

1.0305 550 (1022) Good resistance to reducing gases

Minimum resistance to oxidizers and acids

1.4301 (304) 800 (1472) Heat and corrosion resistant Minimum resistance to reducing flames and Sulphur

1.4306 (304L) 800 (1472) Good resistance to grain boundary corrosion

1.4401 (316) 800 (1472) Good resistance to acids and alkalis

1.4404 (316L) 800 (1472) Good resistance to grain boundary corrosion

1.4435 (316L) 800 (1472) Good resistance to grain boundary corrosion

1.4541 (321) 800 (1472) Good resistance to grain boundary corrosion after welding

1.4571 (316Ti) 800 (1472) Good resistance especially to grain boundary corrosion

1.4762 (446) 1200 (2192) Good resistance to oxidizing and reducing flames, Sulphur containing gases

Minimum resistance to Nitrogen containing gases

1.4749 (446) 1150 (2102) Good resistance to oxidizing and reducing flames, Sulphur containing gases, applications in salt baths and metal smelting

Minimum resistance to Nitrogen containing gases

1.4772 1250 (2282) Use for Copper - brass smelting

1.4821 1350 (2462) Use for Salt Peter, Chloride and Cyanide containing salt baths

1.4841 (314) 1150 (2102) Good resistance to Nitrogen and Oxygen poor gases

Minimum resistance to Sulphur containing gases

1.4845 (310S) 1050 (1922) Higher NiCr content, resistant to high temperature corrosion

1.4876 (Incoloy) 1100 (2012) Resistant to high temperature corrosion and thermal shock

2.4360 (Monel) 600 (1112) Good resistance to steam, high pressure and corrosion

2.4665 (Hastelloy X) 1100 (2012) Good resistance to oxidizing and carburizing atmospheres at high temperatures

267

2.4810 (Hastelloy B) 1100 (2012) Good resistance to heat and corrosion, especially to HCI and H2SO4 attack

2.4811 (Hastelloy C-276)

1100 (2012) Good resistance to oxidizing and reducing atmospheres and to CI2 gas

2.4816 (Inconel) 1150 (2102) Good resistance to oxidizing and reducing atmospheres at high temperatures

Sulphur containing atmospheres must be avoided

Inconel MA 754 1250 (2282) Good mechanical resistance and corrosion resistance at high temperatures in oxidizing atmospheres

3.7035 (Titanium) 600 (1112) Good low temperature corrosion resistance

At high temperatures light oxidation and embrittlement

Stellite 6 1200 (2192) Good resistance to heat, corrosion, abrasion

Tantalum 250 (482) Good resistance to heat and acids

Light oxidation and tendency toward embrittlement at high temperatures in air

Molybdenum 2100 (3812) Good mechanical resistance to inert, reducing and vacuum conditions, resistant to metal vapors at high temperatures

Reacts with Carbon in air and oxidizing gases

Cast iron 700 (1292) Babbitt, Lead, Aluminum, Zinc melts

Metal ceramic thermowells

1.4765 Kanthal 1300 (2372) Good resistance to high temperature oxidation

Tends toward embrittlement through recrystallization

Kanthal Super (MoSi2)

1700 (3092) Resistance to abrasion, thermal shock, surface vitrifies, chemical resistant, well suited for waste incinerators and fluidized bed ovens

Brittle at lower temperatures, ductile above 1400 °C (2552 °F)

UCAR LT1 (CrAI2O2 77/23)

1400 (2552) Resistant to abrasion, thermal shock, oxidation, recommended for iron and non-ferrous metal smelting, cement kilns, resistant Sulphur compounds and acids

Coated thermowells

1.0305 enameled 600 (1112) Corrosive applications in the dew point range for smokestack gases

Impact and bend susceptible

Application conditions for thermowell materials

Material Max. Temp.no pressure°C (°F)

Advantages Disadvantages

268

1.0305 Glass coated 450 (842) Good oxidation and gas protection

Thermal shock susceptible

1.0305 Teflon coated 200 (392) Applications in concentrated hydrochloric, sulphuric and nitric acids

Ceramic thermowells

AI2O3 80% (C530) 1500 (2732) Temperature change resistant, applications in industrial ovens

Fine porosity, not gas tight, shock susceptible

AI2O3 60% (C610) 1600 (2912) Average temperature change resistance, gas tight, high fire resistance, applications in industrial ovens

Lower purity, shock susceptible

AI2O3 99% (C799) 1800 (3272) Gas tight, fire resistant, applica-tions in steel, scoriaceous and glass smelting

AI2O3 99.7% (AL23) 1950 (3542) Fine grain, absolutely gas tight, high purity and strength at high temperatures, resistant to hydrofluoric acid, alkalis, metal oxide vapors

Average thermal shock resistance

AI2O3 99.7% (AL24) 1950 (3542) Porous, thermal shock resistant, high temperature strength; waste incinerators and fluidized bed ovens

Recrystallized SiC 99%

1600 (2912) Good resistance to acids and alkalis, Applications in neutral atmospheres to 1500 °C (2732 °F); applications in non-ferrous metal smelting

Porous

Self-bound SiC 99%

1350 (2462) Minimum porosity, good resis-tance to thermal shock, corro-sion, abrasion and high temperatures; recommended for applications for oxidizing and reducing atmospheres to 1500 °C (2732 °F)

SiSiC (Protect, Silit SK)

1320 (2408) Gas tight, high thermal shock resistance, hard, abrasion resistant; recommended for applications for regenerative air heaters, coal pulverizers, smokestack gases, Zinc, Tin and lead smelting

Average deflections at higher temperatures, not for AI, Cu, Ni, Fe smelting

Application conditions for thermowell materials

Material Max. Temp.no pressure°C (°F)

Advantages Disadvantages

269

SiC62 (TCS) 1100 (2012) High thermal shock resistance, hard, abrasion resistant; recommended for applications for cement kilns, waste incinera-tors, Zinc, Copper, Aluminum, brass and bronze smelting

Porous

Si3N4 (Ekatherm) 1000 (1832) Thermal shock resistant, not wetted during smelting, recommended for brass and bronze smelting

Shock susceptible

Si3N4+AI2O3 (Syalon) 1300 (2372) Thermal shock resistant, recommended for Copper and Aluminum smelting

Graphite 1250 (2282) Oxygen free Copper, brass and Aluminum smelting

High oxidation in air

Application conditions for thermowell materials

Material Max. Temp.no pressure°C (°F)

Advantages Disadvantages

270

11 Appendix 2

Materials, Resistance Table

The selection of the materials to be used for the temperature sensor is a component ofthe selection process. Of primary interest are the materials which will be in contact withthe medium whose temperature is to be measured. The ambient atmospheres may notbe neglected, in which, the humidity is usually the most common factor.

In general, the user knows the medium he wants to measure well enough that thematerial selection is routine. The following table can be used as an aid for the materialselection. The specifications are taken from manufacturer’s corrosion resistance lists.A guarantee for the completeness and correctness cannot be assumed.

Additional information is available from our application engineers.

Gas

/Liq

uid

Ele

ctric

al c

ondu

ctiv

ity

Con

cent

ratio

n (%

)

Tem

pera

ture

°C

(°F

)

Metals Non-Metals1.

4301

(33

04)

1.45

39

1.45

41 (

321)

1.45

71 (

316T

i)H

aste

lloy

BH

aste

lloy

CT

itani

umT

anta

lum

Pla

tinum

Har

d R

ubbe

rS

oft R

ubbe

rP

FA

PT

FE

EP

DM

Bun

a N

Vito

n A

PV

DF

PV

CG

lass

AI 2

O3

Acetic acid L + 50 80 (176) + + + + + + + + + - - + + + + - + +

Acetic anhydride L + 100 20 (68) + + + + + + + + + + + + + +

Acetone L - 100 40 (104) + + + + + + + + + - - + + + - - - - + +

Acetylene G - 100 20 (68) + + + + + + + + + + + + + + + +

Alum. chloride solution L + 30 70 (158) - - - - + - - + + + + + + + + +

Alum. chloride solution L + 80 70 (158) - - - - + - - + + + + + + +

Alum. sulfate solution L + 20 50 (122) - - - + - + + + + + + + + + +

Alum. sulfate solution L + 50 50 (122) - - - + - + + + + - - + + + +

Ammonia G - 100 50 (122) + + + + + + + - + - - + + + + - - - + +

Ammonia solution L + 25 50 (122) + + + + + + + - + - - + + + + + + + +

Aniline L - 100 25 (77) + + + + - + + + + - - + + - + +

Argon G - 100 100 (212) + + + + + + + + + + + + + + + + + + + +

Beer L + 10 (50) + + + + + + + + + + + + + + + +

Benzine L - 100 20 (68) + + + + + + + + + - - + + - + + - + +

Benzol L - 100 50 (122) + + + + + + + + + - - + + - - - - + +

Blood L + + + + + + + + + + + + + + + + + +

Brine L + 20 (68) - - - - - + - + + + + + - + + + +

Bromine L - 100 20 (68) - - - - - + - + + + + + - + +

Butane G - 100 50 (122) + + + + + + + + + + + - + + - - + +

Butyl acetate L 100 50 (122) + + + + + + + + + + + + - + - + +

271

Butyl alcohol L - 100 20 (68) + + + + + + + + + + + + + + + +

Butylene G - 100 20 (68) + + + + + + + + + + + + + + + + +

Calcium chloride soln. L + 100 20 (68) + + + + + + + + + + + + + + + + + +

Calcium hydroxide soln. L + 50 50 (122) + + + + + + + - - + + + + + + + + +

Calcium hypochloride sol L + 20 50 (122) - - - - - + + + + + + + + + +

Caprolactam L - 50 50 (122) + + + + + - + +

Carbolic acid L - 90 50 (122) - + + + + + + + + - - + + - - - + - + +

Carbon dioxide G - 100 50 (122) + + + + + + + + + + + + + + + + + + +

Carbon tetrachloride L - 100 50 (122) + + + + + + + + - - + + + - + + - + +

Carbonic acid L + 50 (122) + + + + + + + + + + + + + + + + + - + +

Carboxylic acid, diluted L - 50 (122) + + + + + + + + + + - + +

Chlorine dioxide, dry G - 100 20 (68) + + + + - - + + + + +

Chlorine hydrogen G - 100 20 (68) - + + + + + + + - - + + + + + + +

Chlorine water L + 100 20 (68) - - - + + - - + + + + + - + +

Chlorine, damp G - 100 20 (68) - + - - - + + - - + + - + + + + +

Chlorine, dry L - 100 20 (68) + + + + - + + + - - + + - + + - + +

Chlorine, dry G - 100 20 (68) + + + + - + + + - + + - + + + + +

Citric acid L + 60 50 (122) + + + - + + - + + + + + - + +

Copper chloride soln L + 50 20 (68) - - - + - + + + + + + + + + + + + +

Copper sulfate solution L + 50 80 (176) + + + + - + + + + + - + + + + + + - + +

Copper sulfate solution L + 100 80 (176) + + + + - + + + + + - + + + + + + - + +

Deionized water L - + + + + + + + + + - - + + + + + + + + +

Diesel L - 100 50 (122) + + + + + + + + + - - + + - + + - + +

Ethane G - 100 50 (122) + + + + + + + + + + + + + - + - - + +

Ethanol L - 96 50 (122) + + + + + + + + + + + + + + + + - +

Ethyl acetate L - 100 50 (122) + + + + + + + + + - - + + - - + - + +

Ethyl alcohol L - 100 78 (172) + + + + + + + + + + + + + - + +

Ethyl ether L - 100 20 (68) + + + + + + + + + - - + + - + + - + +

Ethylene G - 100 50 (122) + + + + + + + + + + + + + - + + + + +

Ethylene chloride L - 100 50 (122) - + - + + + + + + - - + + - + - - + +

Ethylene glycol L + 100 50 (122) + + + + + + + + + + + + - - + +

Fatty acid L - 100 50 (122) + + + + + + + + + - - + + + + + +

Fluorine G - 100 20 (68) + + + + - + - + + - + + - -

Gas

/Liq

uid

Ele

ctric

al c

ondu

ctiv

ity

Con

cent

ratio

n (%

)

Tem

pera

ture

°C

(°F

)

Metals Non-Metals

1.43

01 (

3304

)1.

4539

1.

4541

(32

1)1.

4571

(31

6Ti)

Has

tello

y B

Has

tello

y C

Tita

nium

Tan

talu

mP

latin

umH

ard

Rub

ber

Sof

t Rub

ber

PF

AP

TF

EE

PD

MB

una

NV

iton

AP

VD

FP

VC

Gla

ssA

I 2O

3

272

Formaldehyde solution L + 40 50 (122) + + + + + + + + + - - + + - + + + + +

Formic acid L + 100 80 (176) - + - + - + - + + - - + + - + + - + +

Gelatin L + 50 (122) + + + + + + + + + + + + + + + + + + + +

Glycerine L - 100 100 (212) + + + + + + + + + - + + - + - - + +

Glycol L - 100 50 (122) + + + + + + + + + + + +

Heating oil L - 100 80 (176) + + + + + + + - + + + +

Helium G - 100 80 (176) + + + + + + + + + + + + + - + +

Heptane L - 100 50 (122) + + + + + + + + - - + + - - + + - + +

Hexane L - 100 50 (122) + + + + + + + + + + - + + - + +

Hydrazine solution L + 25 20 (68) + - + - + - - + + + - + + - -

Hydrobromic acid L + 48 50 (122) - - - - + - - + + + + + + - + + + +

Hydrochloric acid L + 10 50 (122) - - - - + - + + + + - + + - - + + + + +

Hydrochloric acid L + 37 20 (68) - - - - + + - + + + - + + - - + + + + +

Hydrocyanic acid L + 100 20 (68) + + + + + + + + + - - + + + + + +

Hydrofluoric acid L + 40 20 (68) - - - - - + - - + + - + + - - - + + - -

Hydrofluoric acid L + 70 20 (68) - - - - - + - - + - - + + - - - + - - -

Hydrogen G - 100 50 (122) + + + + + + + + + + + + + + + + +

Hydrogen peroxide soln. L + 40 20 (68) + + + + + - + - - - + + + + + - +

Hydrogen sulphide dry. G - 100 20 (68) + + + + - + + + + + + + + + + + - + +

Iron-III chloride soln. L + 3 20 (68) - + - - - + + + + + + + + + + + + +

Iron-III chloride soln. L + 10 20 (68) - - - - - + + + + + - + + + + + + + + +

Iron-III sulfate soln. L + 10 20 (68) + + + + + + + + + + + + + + + + + + +

Kerosine L - 100 20 (68) + + + + + + +

Krypton G - 100 50 (122) + + + + + + + + + + + + + - + - - + +

Magnesium chloride soln. L + 50 20 (68) - - - - + + + + + + + + + + + + + + + +

Magnesium sulfate soln. L + 20 50 (122) + + + + + - + + + + + + + + + + + + +

Malic acid L + 50 50 (122) + + + + + + + + + + + + + + + + + + +

Methane G - 100 50 (122) + + + + + + + + + + + + + - + + - - + +

Methyl alcohol L - 100 50 (122) + + + + + + + + + + + + + + + - + - + +

Methyl benzol = Toluol L - 100 50 (122) + + + + + + - - + + - - + + - + +

Methylene chloride G - 100 20 (68) + + + + + + + + + - - + + - - - - - + +

Mono chlorine acetic acid L + 70 50 (122) + + + + + + - - + + + - - - + +

Gas

/Liq

uid

Ele

ctric

al c

ondu

ctiv

ity

Con

cent

ratio

n (%

)

Tem

pera

ture

°C

(°F

)

Metals Non-Metals

1.43

01 (

3304

)1.

4539

1.

4541

(32

1)1.

4571

(31

6Ti)

Has

tello

y B

Has

tello

y C

Tita

nium

Tan

talu

mP

latin

umH

ard

Rub

ber

Sof

t Rub

ber

PF

AP

TF

EE

PD

MB

una

NV

iton

AP

VD

FP

VC

Gla

ssA

I 2O

3

273

Natural gas, dry G - 100 40 (104) + + + + + + + + + - - + + - + + + + +

Neon G - 100 100 (212) + + + + + + + + + + + + + +

Nitric acid L + 20 40 (104) + + + + - + + + + - - + + - - - + + + +

Nitric acid L + 70 50 (122) - + + + - - + + + - - + + - - - + - + +

Nitrogen G - 100 50 (122) + + + + + + + + + + + + + + - - + +

Oleum L + 10 50 (122) - - - - + - - - + - - + - - + - - + +

Oleum L + 20 20 (68) - - - - + - - + + - - + - - + - - + +

Olive oil L - 50 (122) + + + + + + + + + + - + + + + + - + +

Oxalic acid solution L + 10 50 (122) - + - + + + - + + + - + + + + + - + +

Oxygen G - 100 50 (122) + + + + + + + + + + + + - - + +

Ozone G - 10 20 (68) + + + + + + + + - - + + + - + + + +

Perchloroethylene L - 100 50 (122) + + + + + + + + + - - + + - - + + - + +

Petroleum L - 100 20 (68) + + + + + + + + - - + + - + + + + + +

Phenol L - 90 50 (122) - + + + + + + + + - - + + - - - + - + +

Phosgene L - 100 20 (68) + + + + + + + + + - - + + + - - + +

Phosphoric acid L + 30 50 (122) - + - + + + - + + - - + + + - + + - + +

Phosphoric acid L + 80 20 (68) - + - + + + - + + + + + + - - + + + + +

Photo emulsion L + 20 (68) + + + + + + + + + +

Phthalic acid anhydride L - 20 (68) - - - - + + + + + + - + + - + + + + +

Potassium chloride soln. L + 30 20 (68) - - - + + + + + + + + + + + + + + + + +

Potassium hydroxide sol L + 50 20 (68) + + + + + + - - + + + + - + + + +

Potassium permang. L. L + 50 20 (68) + + + + + + + - - + + + + + - +

Potassium sulfate soln L + 20 50 (122) + + + + + + + + + + + + + + + + +

Propane G - 100 50 (122) + + + + + + - - + + - - + - - + +

Sea water L + 50 (122) - + - - - + + + + + + + + + + + + - + +

Sodium bicarbonate soln. L + 20 50 (122) + + + + + + + + + + + + + +

Sodium bisulfate soln. L + 10 50 (122) - - - + + + + + + + + + + + + + + + +

Sodium bisulfate soln. L + 50 50 (122) + + + + + + + + + + + + + + + +

Sodium carbonate soln. L + 50 50 (122) - - - - + + + + + + + + + + + + + + +

Sodium chloride soln. L + 10 20 (68) - + - - - + + + + - - + + + + + + + + +

Sodium chloride soln. L + 20 20 (68) - - - - - + + + + - - + + + + + + + + +

Sodium hydroxide soln. L + 20 50 (122) + + + + + + + - + - + + + - - + + - +

Sodium hydroxide soln. L + 50 50 (122) + + + + + + - - + + + + - - - + + - -

Gas

/Liq

uid

Ele

ctric

al c

ondu

ctiv

ity

Con

cent

ratio

n (%

)

Tem

pera

ture

°C

(°F

)

Metals Non-Metals

1.43

01 (

3304

)1.

4539

1.

4541

(32

1)1.

4571

(31

6Ti)

Has

tello

y B

Has

tello

y C

Tita

nium

Tan

talu

mP

latin

umH

ard

Rub

ber

Sof

t Rub

ber

PF

AP

TF

EE

PD

MB

una

NV

iton

AP

VD

FP

VC

Gla

ssA

I 2O

3

274

Symbols in resistance table:

+ means usable material- means unsuitable material

blank cells indicate unknown resistance

Sodium hypo chloride sol L + 20 50 (122) - - - - + + - + - - + + + + + - + +

Sodium nitrate solution L + 30 50 (122) + + + + + + + + + + + + + + + - + +

Sodium silicate solution L + 30 50 (122) + + + + + + + + + + + + + + + + + +

Sodium sulfate solution L + 20 50 (122) + + + + + + + + + + + + + + + + - + +

Sodium vanadate soln. L + 10 50 (122) + + + + + + + + + + + + + +

Spin bath L + 50 (122) + + - - + - - + + - + - + +

Sulphur dioxide, dry G - 100 50 (122) + + + + - + + + + + + + + + + - + +

Sulphuric acid L + 10 50 (122) - + - - + + - + + + + + + + + + + + +

Sulphuric acid L + 50 20 (68) - + - - + + - + + + + + + - + + - + +

Sulphuric acid L + 96 20 (68) - + - + + + - + + - - + + - + + - + +

Sulphurous acid L + 10 20 (68) + + - + - + + + - + + + + + +

Tannic acid L + 50 50 (122) + + + + + + + - - + +

Tartaric acid L + 20 50 (122) - - - - + + + + + + + + + + + +

Toluol L - 100 50 (122) + + + + + + - - + + - - + + - + +

Trichlorethylene L - 100 50 (122) + + + + + + + + + - - + + - - + + - + +

Tricresyl phosphate L 100 50 (122) + + + + + + - - + + + - - - + +

Urea L + 30 50 (122) + + + + + + + + + + + + - + +

Vinyl acetate L 100 20 (68) + + - + - - + + + + + + +

Vinyl chloride L 100 20 (68) + + + + + + - - + + - + +

Wort (beer) L + 5 (41) + + + + + + + + + + + + + + + +

Xylene L - 100 50 (122) + + + + + + - - + + - - + - + +

Yeast L + 20 (68) + + + + + + + + + + + + + + + + + + +

Zinc chloride solution L + 60 20 (68) - - - - + + + + + + + + + + + + + + +

Gas

/Liq

uid

Ele

ctric

al c

ondu

ctiv

ity

Con

cent

ratio

n (%

)

Tem

pera

ture

°C

(°F

)

Metals Non-Metals

1.43

01 (

3304

)1.

4539

1.

4541

(32

1)1.

4571

(31

6Ti)

Has

tello

y B

Has

tello

y C

Tita

nium

Tan

talu

mP

latin

umH

ard

Rub

ber

Sof

t Rub

ber

PF

AP

TF

EE

PD

MB

una

NV

iton

AP

VD

FP

VC

Gla

ssA

I 2O

3

275

12 Bibliography

W.W. Wendlandt Thermochimica actaVolume 73, Amsterdam, 1984

Nicholas, White Traceable TemperaturesJ. Wiley, Sussex, 1994

Asimov Exakte Geheimnisse unserer WeltDroemer Knaur, 1984(Exact Secrets of Our World)

Paul H. Dyke Thermoelectric ThermometryLeeds & Northrup Company, 1955

F. Henning TemperaturmessungJ.A. Barth Verlag, Leipzig, 1951(Temperature Measurements)

F. Lieneweg Temperaturmessungakademische Verlagsgesellschaft, Leipzig, 1950(Temperature Measurements)

M.K. Juchheim Elektrische Temperaturmessung5. Auflage, Fulda, 1996(Electrical Temperature Measurements)

Körtvélyessy Thermoelement Praxis2. Ausgabe, Vulkan-Verlag, Essen, 1987(Thermocouple Practice)

J. W. Murdock Power Test Code Thermometer WellsJournal of Engineering Power, Oct. 1959

AD-Merkblätter, Taschenbuch-Ausgabe 1998Carl Heymanns Verlag, Beuth Verlag, 1998(AD Data Sheets, Pocket Book edition)

TRD Technische Regeln für Dampfkessel, Taschenbuch-Ausgabe 1997Carl Heymanns Verlag, Beuth Verlag, 1998(TRD Technical Regulations for Steam BoilersPocket Book Edition)

F. Lieneweg Handbuch der technischen Temperaturmessung, Abschnitt 6.3 (Hrsg./Editor) Die mechanische Beanspruchung von Thermometern

(Autor: P. Dittrich) Vieweg Verlag, 1976)(Handbook for Temperature Measurements, Chapter 6.3The Mechanical Forces on Thermometers)

276

O. Uhrig Beitrag zur Berechnung und Gestaltung von hochbeanspruchtenSchutzrohren. VDI-Fortschrittsberichte, VDI-Verlag, 1981(Article for Calculations and Designs for Highly Stressed Thermowells)

Hütte Die Grundlagen der IngenieurwissenschaftenSpringer-Verlag, 1996(Basics for Engineering Sciences)

S. Schwaigerer Festigkeitsberechnung im Dampfkessel-, Behälter- und Rohrleitungsbau. Springer-Verlag, 1978(Manufacturing Calculations for Steam Boilers, Tanks and Pipeline Designs

Temperatursensoren – Prinzipien und ApplikationenExpert Verlag, ISBN 3-8169-1261, 1995(Temperature Sensors – Principles and Applications)

Temperaturmessung in der TechnikExpert Verlag, ISBN 3-8169-0200-6(Temperature Measurements in Technology)

TemperatursensorenFirmenpublication, Hartmann & Braun, 8123 D/E(Temperature Sensors - Company Publication)

Metall Forschung und EntwicklungDegussa, Frankfurt 1991(Metal Research and Development)

Harald Jacques Industrielle Messtechnik mit Pt-Schichtmesswiderständen(Industrial Measurements with Pt Film Resistors)

Joachim Scholz Temperatusensoren für den industriellen EinsatzDegussa-Sonderdruck Nr.8206 aus industrie-elektik + elektronik 29.Jahrgang 1984, Nr.11Dr. Alfred Hüthig-Verlag / Heidelberg(Temperature Sensors for Industrial Applications)

Dr. Harald Jacques Hochstabile Temperatursensoren für vielfältige AnwendungenDegussa-Sonderdruck Nr.8215(High Stability Temperature Sensors for Multiple Applications)

VDI/VDE 2600: Metrologie (Messtechnik),Blatt 1 bis 6 (Sheets 1 to 6)(Metrology)

DIN IEC 381: Analoge Signale für Regel- und Steueranlagen(Analog Signals for Control Systems)

277

J.Sturm, B.Winkler MSR in der Chemischen Technik, Band 1Springer Verlag(Measuring and Control in Chemical Technology, Vol. 1)

Bell System Technical Reference: PUB 41212Data Sets 202S and 202T

HART-NutzerorganisationHART Feld-Kommunikations-Protokoll, Stand 09/92(HART-User Organization Field Communication Protocol)

VDI Berichte 982, Temperatur 92VDI-Verlag, Stand 1992 (VDI Reports 982, Temperature 92)

Mess-, Analysen- und ProzessleittechnikDECHEMA e.V/ACHEMA, Stand 1994(Measuring, Analyzing and Process Control Technology)

PROFIBUS, Technische KurzbeschreibungPNO, Stand 97(PROFIBUS, Condensed Technical Description)

Fieldbus FOUNDATION, Application GuideFieldbus FOUNDATION AG-163 Rev. 1.0

DKD-3 Angabe der Messunsicherheiten bei KalibrierungenVerlag für neue Wissenschaften GmbH, Bremerhaven(Tolerance Specifications for Calibrations)

DKD-3-E1 Angabe der Messunsicherheit bei Kalibrierungen, BeispieleVerlag für neue Wissenschaften GmbH, Bremerhaven(Specifications for Measuring Uncertainties for Calibrations, Examples)

Dr. W. Kessel Messunsicherheitsanalyse – fundamentaler Bestandteil derPrüfmittelüberwachung(Measurement Uncertainty Analysis, Fundamental Componentof Test Equipment Monitoring)

Franz Adunka Messunsicherheiten: Theorie und PraxisVulkan Verlag, Essen, 1998(Measurement Uncertainities, Theory and Practice)

Bernhard, F. Handbuch der technischen Temperaturmessung, (Hrsg..Editor): Springer-Verlag Berlin

(Handbook for Temperature Measurements)

VDI-Wärmeatlas, 8. Auflage, Springer-Verlag Berlin, 1998(VDI-Heat Atlas, 8th Edition)

278

Weichert, Lother Temperaturmessung in der TechnikVAE Kontakt & Studium Band 9; Expert Verlag(Temperature Measurements in Technology)

H. E. Bennett Noble Metal ThermocouplesJohnson, Matthey & Co, 1958

Horst Böhm Einführung in die MetallkundeBI Hochschultaschenbücher(Introduction to Metal Science)

Dr. A. Schulz Metallische Werkstoffe für ThermoelementeN.E.M.-Verlag Berlin, Heft 10(Metal Materials for Thermocouples)

PTB-Texte, Band 7, 20 Jahre Deutscher Kalibrierdienst,Wirtschaftsverlag NW, 1998(PTB Texts, Vol. 7, 20 Years German Calibration Service)

Ch. Diedrich PROFIBUS PAVerlag Oldenbourg, ISBN 3-8350-3056-3

P. Westerfeld Die Entwicklung der betrieblichen Temperaturmesstechnikin der Prozessautomatisierungin:Elektrotechnik – Signale, Aufbruch, Perspektiven;Geschichte der Elektrotechnik 7VDE-Verlag Offenbach, 1988(The Development of Industrial Temperature MeasurementTechnology in Process Automation)

Optris GmbH Basics of Non-contact Infrared Temperature Measurement, 2006

279

13 Basic Values for Thermocouples and Resistance Thermometers

Based on the International Temperature Scale ITS-90

According to EN 60584/IEC 584:Thermocouples Types T, E, J, K, N, S, R, BAccording to EN 60751/IEC 751:Resistance Thermometers Pt100

Based on the Temperature Scale IPTS-68

According to DIN 43710 (repealed since 1994. No new editions):Thermocouples Types U and LAccording to DIN 43760:Resistance Thermometers Ni100

Resistance thermometers with special measurement resistorsPt50, Pt200, Pt500, Pt1000

The standardized measurement resistor Pt100 according to EN 60751/IEC 751 has anominal resistance of 100 Ω at 0 °C (32 °F). Based on these standards, measurementresistors with fractional or whole number multiples of these nominal resistance valuesare commercially available. Based on the statements from the manufacturer the follow-ing conversion factors apply.

For Ni-resistance thermometers, a similar procedure applies.

Designation Nominal Resistance0 °C (32 °F)

Factor Resistance Value

Pt50 50 Ω 0.5 0.5 x Pt100 EN 60751/IEC 751

Pt200 200 Ω 2 2 x Pt100 EN 60751/IEC 751

Pt500 500 Ω 5 5 x Pt100 EN 60751/IEC 751

Pt1000 1000 Ω 10 10 x Pt100 EN 60751/IEC 751

280

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

-270-269-268-267-266

-6.258-6.256-6.255-6.253-6.251

-9.835-9.833-9.831-9.828-9.825

-6.458-6.457-6.456-6.455-6.453

-4.345-4.345-4.344-4.344-4.343

-454.0-452.2-450.4-448.6-446.8

-265-264-263-262-261

-6.248-6.245-6.242-6.239-6.236

-9.821-9.817-9.813-9.808-9.802

-6.452-6.450-6.448-6.446-6.444

-4.342-4.341-4.340-4.339-4.337

-445.0-443.2-441.4-439.6-437.8

-260-259-258-257-256

-6.232-6.228-6.223-6.219-6.214

-9.797-9.790-9.784-9.777-9.770

-6.441-6.438-6.435-6.432-6.429

-4.336-4.334-4.332-4.330-4.328

-436.0-434.2-432.4-430.6-428.8

-255-254-253-252-251

-6.209-6.204-6.198-6.193-6.187

-9.762-9.754-9.746-9.737-9.728

-6.425-6.421-6.417-6.413-6.408

-4.326-4.324-4.321-4.319-4.316

-427.0-425.2-423.4-421.6-419.8

-250-249-248-247-246

-6.180-6.174-6.167-6.160-6.153

-9.718-9.709-9.698-9.688-9.677

-6.404-6.399-6.393-6.388-6.382

-4.313-4.310-4.307-4.304-4.300

-418.0-416.2-414.4-412.6-410.8

-245-244-243-242-241

-6.146-6.138-6.130-6.122-6.114

-9.666-9.654-9.642-9.630-9.617

-6.377-6.370-6.364-6.358-6.351

-4.297-4.293-4.289-4.285-4.281

-409.0-407.2-405.4-403.6-401.8

-240-239-238-237-236

-6.105-6.096-6.087-6.078-6.068

-9.604-9.591-9.577-9.563-9.548

-6.344-6.337-6.329-6.322-6.314

-4.277-4.273-4.268-4.263-4.258

-400.0-398.2-396.4-394.6-392.8

-235-234-233-232-231

-6.059-6.049-6.038-6.028-6.017

-9.534-9.519-9.503-9.487-9.471

-6.306-6.297-6.289-6.280-6.271

-4.254-4.248-4.243-4.238-4.232

-391.0-389.2-387.4-385.6-383.8

-230-229-228-227-226

-6.007-5.996-5.985-5.973-5.962

-9.455-9.438-9.421-9.404-9.386

-6.262-6.252-6.243-6.233-6.223

-4.226-4.221-4.215-4.209-4.202

-382.0-380.2-378.4-376.6-374.8

-225-224-223-222-221

-5.950-5.938-5.926-5.914-5.901

-9.368-9.350-9.331-9.313-9.293

-6.213-6.202-6.192-6.181-6.170

-4.196-4.189-4.183-4.176-4.169

-373.0-371.2-369.4-367.6-365.8

281

-220-219-218-217-216

-5.888-5.876-5.863-5.850-5.836

-9.274-9.254-9.234-9.214-9.193

-6.158-6.147-6.135-6.123-6.111

-4.162-4.154-4.147-4.140-4.132

-364.0-362.2-360.4-358.6-356.8

-215-214-213-212-211

-5.823-5.809-5.795-5.782-5.767

-9.172-9.151-9.129-9.107-9.085

-6.099-6.087-6.074-6.061-6.048

-4.124-4.116-4.108-4.100-4.091

-355.0-353.2-351.4-349.6-347.8

-210-209-208-207-206

-5.753-5.739-5.724-5.710-5.695

-9.063-9.040-9.017-8.994-8.971

-8.095-8.076-8.057-8.037-8.017

-6.035-6.021-6.007-5.994-5.980

-4.083-4.074-4.066-4.057-4.048

-346.0-344.2-342.4-340.6-338.8

-205-204-203-202-201

-5.680-5.665-5.650-5.634-5.619

-8.947-8.923-8.899-8.874-8.850

-7.996-7.976-7.955-7.934-7.912

-5.965-5.951-5.936-5.922-5.907

-4.038-4.029-4.020-4.010-4.000

-337.0-335.2-333.4-331.6-329.8

-200-199-198-197-196

-5.603-5.587-5.571-5.555-5.539

-8.825-8.799-8.774-8.748-8.722

-7.890-7.868-7.846-7.824-7.801

-5.891-5.876-5.861-5.845-5.829

-3.990-3.980-3.970-3.960-3.950

-5.70-5.68-5.66-5.64-5.62

-8.15-8.12-8.09-8.06-8.03

18.5218.9519.3819.8220.25

-328.0-326.2-324.4-322.6-320.8

-195-194-193-192-191

-5.523-5.506-5.489-5.473-5.456

-8.696-8.669-8.643-8.616-8.588

-7.778-7.755-7.731-7.707-7.683

-5.813-5.797-5.780-5.763-5.747

-3.939-3.928-3.918-3.907-3.896

-5.60-5.59-5.57-5.55-5.53

-8.00-7.98-7.95-7.92-7.89

20.6821.1121.5421.9722.40

-319.0-317.2-315.4-313.6-311.8

-190-189-188-187-186

-5.439-5.421-5.404-5.387-5.369

-8.561-8.533-8.505-8.477-8.449

-7.659-7.634-7.610-7.585-7.559

-5.730-5.713-5.695-5.678-5.660

-3.884-3.873-3.862-3.850-3.838

-5.51-5.49-5.47-5.45-5.43

-7.86-7.83-7.80-7.77-7.74

22.8323.2523.6824.1124.54

-310.0-308.2-306.4-304.6-302.8

-185-184-183-182-181

-5.351-5.334-5.316-5.297-5.279

-8.420-8.391-8.362-8.333-8.303

-7.534-7.508-7.482-7.456-7.429

-5.642-5.624-5.606-5.588-5.569

-3.827-3.815-3.803-3.790-3.778

-5.41-5.40-5.38-5.36-5.34

-7.71-7.68-7.65-7.62-7.59

24.9725.3925.8226.2526.67

-301.0-299.2-297.4-295.6-293.8

-180-179-178-177-176

-5.261-5.242-5.224-5.205-5.186

-8.273-8.243-8.213-8.183-8.152

-7.403-7.376-7.348-7.321-7.293

-5.550-5.531-5.512-5.493-5.474

-3.766-3.753-3.740-3.728-3.715

-5.32-5.30-5.28-5.26-5.24

-7.56-7.53-7.50-7.47-7.44

27.1027.5227.9528.3728.80

-292.0-290.2-288.4-286.6-284.8

-175-174-173-172-171

-5.167-5.148-5.128-5.109-5.089

-8.121-8.090-8.059-8.027-7.995

-7.265-7.237-7.209-7.181-7.152

-5.454-5.435-5.415-5.395-5.374

-3.702-3.688-3.675-3.662-3.648

-5.22-5.20-5.18-5.16-5.14

-7.40-7.37-7.34-7.31-7.28

29.2229.6430.0730.4930.91

-283.0-281.2-279.4-277.6-275.8

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

282

-170-169-168-167-166

-5.070-5.050-5.030-5.010-4.989

-7.963-7.931-7.899-7.866-7.833

-7.123-7.094-7.064-7.035-7.005

-5.354-5.333-5.313-5.292-5.271

-3.634-3.621-3.607-3.593-3.578

-5.12-5.10-5.08-5.06-5.04

-7.25-7.22-7.19-7.15-7.12

31.3431.7632.1832.6033.02

-274.0-272.2-270.4-268.6-266.8

-165-164-163-162-161

-4.969-4.949-4.928-4.907-4.886

-7.800-7.767-7.733-7.700-7.666

-6.975-6.944-6.914-6.883-6.853

-5.250-5.228-5.207-5.185-5.163

-3.564-3.550-3.535-3.521-3.506

-5.02-4.99-4.97-4.95-4.93

-7.09-7.06-7.03-6.99-6.96

33.4433.8634.2834.7035.12

-265.0-263.2-261.4-259.6-257.8

-160-159-158-157-156

-4.865-4.844-4.823-4.802-4.780

-7.632-7.597-7.563-7.528-7.493

-6.821-6.790-6.759-6.727-6.695

-5.141-5.119-5.097-5.074-5.052

-3.491-3.476-3.461-3.446-3.431

-4.91-4.89-4.87-4.84-4.82

-6.93-6.90-6.86-6.83-6.80

35.5435.9636.3836.8037.22

-256.0-254.2-252.4-250.6-248.8

-155-154-153-152-151

-4.759-4.737-4.715-4.693-4.671

-7.458-7.423-7.387-7.351-7.315

-6.663-6.631-6.598-6.566-6.533

-5.029-5.006-4.983-4.960-4.936

-3.415-3.400-3.384-3.368-3.352

-4.80-4.78-4.76-4.73-4.71

-6.76-6.73-6.70-6.66-6.63

37.6438.0638.4738.8939.31

-247.0-245.2-243.4-241.6-239.8

-150-149-148-147-146

-4.648-4.626-4.604-4.581-4.558

-7.279-7.243-7.206-7.170-7.133

-6.500-6.467-6.433-6.400-6.366

-4.913-4.889-4.865-4.841-4.817

-3.336-3.320-3.304-3.288-3.271

-4.69-4.67-4.64-4.62-4.60

-6.60-6.56-6.53-6.50-6.46

39.7240.1440.5640.9741.39

-238.0-236.2-234.4-232.6-230.8

-145-144-143-142-141

-4.535-4.512-4.489-4.466-4.443

-7.096-7.058-7.021-6.983-6.945

-6.332-6.298-6.263-6.229-6.194

-4.793-4.768-4.744-4.719-4.694

-3.255-3.238-3.221-3.205-3.188

-4.58-4.55-4.53-4.51-4.48

-6.43-6.39-6.36-6.33-6.29

41.8042.2242.6343.0543.46

-229.0-227.2-225.4-223.6-221.8

-140-139-138-137-136

-4.419-4.395-4.372-4.348-4.324

-6.907-6.869-6.831-6.792-6.753

-6.159-6.124-6.089-6.054-6.018

-4.669-4.644-4.618-4.593-4.567

-3.171-3.153-3.136-3.119-3.101

-4.46-4.43-4.41-4.38-4.36

-6.26-6.22-6.19-6.15-6.11

43.8844.2944.7045.1245.53

-220.0-218.2-216.4-214.6-212.8

-135-134-133-132-131

-4.300-4.275-4.251-4.226-4.202

-6.714-6.675-6.636-6.596-6.556

-5.982-5.946-5.910-5.874-5.838

-4.542-4.516-4.490-4.463-4.437

-3.084-3.066-3.048-3.030-3.012

-4.33-4.31-4.28-4.26-4.23

-6.08-6.04-6.01-5.97-5.93

45.9446.3646.7747.1847.59

-211.0-209.2-207.4-205.6-203.8

-130-129-128-127-126

-4.177-4.152-4.127-4.102-4.077

-6.516-6.476-6.436-6.396-6.355

-5.801-5.764-5.727-5.690-5.653

-4.411-4.384-4.357-4.330-4.303

-2.994-2.976-2.958-2.939-2.921

-4.21-4.18-4.16-4.13-4.11

-5.90-5.86-5.82-5.79-5.75

48.0148.4248.8349.2449.65

-202.0-200.2-198.4-196.6-194.8

-125-124-123-122-121

-4.052-4.026-4.000-3.975-3.949

-6.314-6.273-6.232-6.191-6.149

-5.616-5.578-5.541-5.503-5.465

-4.276-4.249-4.221-4.194-4.166

-2.902-2.883-2.865-2.846-2.827

-4.08-4.05-4.03-4.00-3.98

-5.71-5.68-5.64-5.60-5.57

50.0650.4750.8851.2951.70

-193.0-191.2-189.4-187.6-185.8

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

283

-120-119-118-117-116

-3.923-3.897-3.871-3.844-3.818

-6.107-6.065-6.023-5.981-5.939

-5.426-5.388-5.350-5.311-5.272

-4.138-4.110-4.082-4.054-4.025

-2.808-2.789-2.769-2.750-2.730

-3.95-3.92-3.90-3.87-3.84

-5.53-5.49-5.45-5.41-5.38

52.1152.5252.9353.3453.75

-184.0-182.2-180.4-178.6-176.8

-115-114-113-112-111

-3.791-3.765-3.738-3.711-3.684

-5.896-5.853-5.810-5.767-5.724

-5.233-5.194-5.155-5.116-5.076

-3.997-3.968-3.939-3.911-3.882

-2.711-2.691-2.672-2.652-2.632

-3.81-3.79-3.76-3.73-3.71

-5.34-5.30-5.26-5.22-5.19

54.1554.5654.9755.3855.79

-175.0-173.2-171.4-169.6-167.8

-110-109-108-107-106

-3.657-3.629-3.602-3.574-3.547

-5.681-5.637-5.593-5.549-5.505

-5.037-4.997-4.957-4.917-4.877

-3.852-3.823-3.794-3.764-3.734

-2.612-2.592-2.571-2.551-2.531

-3.68-3.65-3.62-3.60-3.57

-5.15-5.11-5.07-5.03-4.99

56.1956.6057.0157.4157.82

-166.0-164.2-162.4-160.6-158.8

-105-104-103-102-101

-3.519-3.491-3.463-3.435-3.407

-5.461-5.417-5.372-5.327-5.282

-4.836-4.796-4.755-4.714-4.674

-3.705-3.675-3.645-3.614-3.584

-2.510-2.490-2.469-2.448-2.428

-3.54-3.51-3.48-3.46-3.43

-4.95-4.91-4.87-4.83-4.79

58.2358.6359.0459.4459.85

-157.0-155.2-153.4-151.6-149.8

-100- 99- 98- 97- 96

-3.379-3.350-3.322-3.293-3.264

-5.237-5.192-5.147-5.101-5.055

-4.633-4.591-4.550-4.509-4.467

-3.554-3.523-3.492-3.462-3.431

-2.407-2.386-2.365-2.344-2.322

-3.40-3.37-3.34-3.31-3.28

-4.75-4.71-4.66-4.62-4.58

60.2660.6661.0761.4761.88

-148.0-146.2-144.4-142.6-140.8

- 95- 94- 93- 92- 91

-3.235-3.206-3.177-3.148-3.118

-5.009-4.963-4.917-4.871-4.824

-4.425-4.384-4.342-4.300-4.257

-3.400-3.368-3.337-3.306-3.274

-2.301-2.280-2.258-2.237-2.215

-3.25-3.23-3.20-3.17-3.14

-4.54-4.50-4.45-4.41-4.37

62.2862.6863.0963.4963.90

-139.0-137.2-135.4-133.6-131.8

- 90- 89- 88- 87- 86

-3.089-3.059-3.030-3.000-2.970

-4.777-4.731-4.684-4.636-4.589

-4.215-4.173-4.130-4.088-4.045

-3.243-3.211-3.179-3.147-3.115

-2.193-2.172-2.150-2.128-2.106

-3.11-3.08-3.05-3.02-2.99

-4.33-4.28-4.24-4.20-4.15

64.3064.7065.1165.5165.91

-130.0-128.2-126.4-124.6-122.8

- 85- 84- 83- 82- 81

-2.940-2.910-2.879-2.849-2.818

-4.542-4.494-4.446-4.398-4.350

-4.002-3.959-3.916-3.872-3.829

-3.083-3.050-3.018-2.986-2.953

-2.084-2.062-2.039-2.017-1.995

-2.96-2.93-2.90-2.87-2.84

-4.11-4.06-4.02-3.98-3.93

66.3166.7267.1267.5267.92

-121.0-119.2-117.4-115.6-113.8

- 80- 79- 78- 77- 76

-2.788-2.757-2.726-2.695-2.664

-4.302-4.254-4.205-4.156-4.107

-3.786-3.742-3.698-3.654-3.610

-2.920-2.887-2.854-2.821-2.788

-1.972-1.950-1.927-1.905-1.882

-2.81-2.78-2.75-2.72-2.69

-3.89-3.84-3.80-3.75-3.71

68.3368.7369.1369.5369.93

-112.0-110.2-108.4-106.6-104.8

- 75- 74- 73- 72- 71

-2.633-2.602-2.571-2.539-2.507

-4.058-4.009-3.960-3.911-3.861

-3.566-3.522-3.478-3.434-3.389

-2.755-2.721-2.688-2.654-2.620

-1.859-1.836-1.813-1.790-1.767

-2.66-2.62-2.59-2.56-2.53

-3.66-3.62-3.57-3.53-3.48

70.3370.7371.1371.5371.93

-103.0-101.2-99.4-97.6-95.8

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

284

- 70- 69- 68- 67- 66

-2.476-2.444-2.412-2.380-2.348

-3.811-3.761-3.711-3.661-3.611

-3.344-3.300-3.255-3.210-3.165

-2.587-2.553-2.519-2.485-2.450

-1.744-1.721-1.698-1.674-1.651

-2.50-2.47-2.44-2.40-2.37

-3.44-3.39-3.35-3.30-3.25

72.3372.7373.1373.5373.93

-94.0-92.2-90.4-88.6-86.8

- 65- 64- 63- 62- 61

-2.316-2.283-2.251-2.218-2.186

-3.561-3.510-3.459-3.408-3.357

-3.120-3.075-3.029-2.984-2.938

-2.416-2.382-2.347-2.312-2.278

-1.627-1.604-1.580-1.557-1.533

-2.34-2.31-2.28-2.24-2.21

-3.21-3.16-3.12-3.07-3.02

74.3374.7375.1375.5375.93

-85.0-83.2-81.4-79.6-77.8

- 60- 59- 58- 57- 56

-2.153-2.120-2.087-2.054-2.021

-3.306-3.255-3.204-3.152-3.100

-2.893-2.847-2.801-2.755-2.709

-2.243-2.208-2.173-2.138-2.103

-1.509-1.485-1.462-1.438-1.414

-2.18-2.15-2.11-2.08-2.05

-2.98-2.93-2.88-2.84-2.79

76.3376.7377.1277.5277.92

69.570.070.570.971.4

-76.0-74.2-72.4-70.6-68.8

- 55- 54- 53- 52- 51

-1.987-1.954-1.920-1.887-1.853

-3.048-2.996-2.944-2.892-2.840

-2.663-2.617-2.571-2.524-2.478

-2.067-2.032-1.996-1.961-1.925

-1.390-1.366-1.341-1.317-1.293

-2.02-1.98-1.95-1.92-1.88

-2.74-2.70-2.65-2.60-2.56

78.3278.7279.1179.5179.91

71.972.372.873.373.8

-67.0-65.2-63.4-61.6-59.8

- 50- 49- 48- 47- 46

-1.819-1.785-1.751-1.717-1.683

-2.787-2.735-2.682-2.629-2.576

-2.431-2.385-2.338-2.291-2.244

-1.889-1.854-1.818-1.782-1.745

-1.269-1.244-1.220-1.195-1.171

-0.236-0.232-0.228

-0.224-0.219

-0.226-0.223-0.219-0.215-0.211

-1.85-1.81-1.78-1.74-1.71

-2.51-2.46-2.41-2.36-2.32

80.3180.7081.1081.5081.89

74.374.775.275.776.2

-58.0-56.2-54.4-52.6-50.8

- 45- 44- 43- 42- 41

-1.648-1.614-1.579-1.545-1.510

-2.523-2.469-2.416-2.362-2.309

-2.197-2.150-2.103-2.055-2.008

-1.709-1.673-1.637-1.600-1.564

-1.146-1.122-1.097-1.072-1.048

-0.215-0.211-0.207-0.203-0.199

-0.208-0.204-0.200-0.196-0.192

-1.67-1.64-1.60-1.57-1.53

-2.27-2.22-2.17-2.12-2.08

82.2982.6983.0883.4883.87

76.777.277.778.178.6

-49.0-47.2-45.4-43.6-41.8

- 40- 39- 38- 37- 36

-1.475-1.440-1.405-1.370-1.335

-2.255-2.201-2.147-2.093-2.038

-1.961-1.913-1.865-1.818-1.770

-1.527-1.490-1.453-1.417-1.380

-1.023-0.998-0.973-0.948-0.923

-0.194-0.190-0.186-0.181-0.177

-0.188-0.184-0.180-0.175-0.171

-1.50-1.46-1.43-1.39-1.36

-2.03-1.98-1.93-1.88-1.83

84.2784.6785.0685.4685.85

79.179.680.180.681.1

-40.0-38.2-36.4-34.6-32.8

- 35- 34- 33- 32- 31

-1.299-1.264-1.228-1.192-1.157

-1.984-1.929-1.874-1.820-1.765

-1.722-1.674-1.626-1.578-1.530

-1.343-1.305-1.268-1.231-1.194

-0.898-0.873-0.848-0.823-0.798

-0.173-0.168-0.164-0.159-0.155

-0.167-0.163-0.158-0.154-0.150

-1.32-1.28-1.25-1.21-1.18

-1.78-1.73-1.68-1.63-1.58

86.2586.6487.0487.4387.83

81.682.182.683.183.6

-31.0-29.2-27.4-25.6-23.8

- 30- 29- 28- 27- 26

-1.121-1.085-1.049-1.013-0.976

-1.709-1.654-1.599-1.543-1.488

-1.482-1.433-1.385-1.336-1.288

-1.156-1.119-1.081-1.043-1.006

-0.772-0.747-0.722-0.696-0.671

-0.150-0.146-0.141-0.136-0.132

-0.145-0.141-0.137-0.132-0.128

-1.14-1.10-1.07-1.03-0.99

-1.53-1.48-1.43-1.38-1.32

88.2288.6289.0189.4089.80

84.184.785.285.786.2

-22.0-20.2-18.4-16.6-14.8

- 25- 24- 23- 22- 21

-0.940-0.904-0.867-0.830-0.794

-1.432-1.376-1.320-1.264-1.208

-1.239-1.190-1.142-1.093-1.044

-0.968-0.930-0.892-0.854-0.816

-0.646-0.620-0.595-0.569-0.544

-0.127-0.122-0.117-0.113-0.108

-0.123-0.119-0.114-0.109-0.105

-0.95-0.92-0.88-0.84-0.81

-1.27-1.22-1.17-1.12-1.07

90.1990.5990.9891.3791.77

86.787.287.788.388.8

-13.0-11.2

-9.4-7.6-5.8

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

285

- 20- 19- 18- 17- 16

-0.757-0.720-0.683-0.646-0.608

-1.152-1.095-1.039-0.982-0.925

-0.995-0.946-0.896-0.847-0.798

-0.778-0.739-0.701-0.663-0.624

-0.518-0.492-0.467-0.441-0.415

-0.103-0.098-0.093-0.088-0.083

-0.100-0.095-0.091-0.086-0.081

-0.77-0.73-0.69-0.66-0.62

-1.02-0.97-0.92-0.87-0.81

92.1692.5592.9593.3493.73

89.389.890.390.991.4

-4.0-2.2-0.41.43.2

- 15- 14- 13- 12- 11

-0.571-0.534-0.496-0.459-0.421

-0.868-0.811-0.754-0.697-0.639

-0.749-0.699-0.650-0.600-0.550

-0.586-0.547-0.508-0.470-0.431

-0.390-0.364-0.338-0.312-0.286

-0.078-0.073-0.068-0.063-0.058

-0.076-0.071-0.066-0.061-0.056

-0.58-0.54-0.50-0.47-0.43

-0.76-0.71-0.66-0.61-0.56

94.1294.5294.9195.3095.69

91.992.593.093.594.0

5.06.88.6

10.412.2

- 10- 9- 8- 7- 6

-0.383-0.345-0.307-0.269-0.231

-0.582-0.524-0.466-0.408-0.350

-0.501-0.451-0.401-0.351-0.301

-0.392-0.353-0.314-0.275-0.236

-0.260-0.234-0.209-0.183-0.157

-0.053-0.048-0.042-0.037-0.032

-0.051-0.046-0.041-0.036-0.031

-0.39-0.35-0.31-0.27-0.23

-0.51-0.46-0.41-0.36-0.31

96.0996.4896.8797.2697.65

94.695.195.796.296.7

14.015.817.619.421.2

- 5- 4- 3- 2- 1

-0.193-0.154-0.116-0.077-0.039

-0.292-0.234-0.176-0.117-0.059

-0.251-0.201-0.151-0.101-0.050

-0.197-0.157-0.118-0.079-0.039

-0.131-0.104-0.078-0.052-0.026

-0.027-0.021-0.016-0.011-0.005

-0.026-0.021-0.016-0.011-0.005

-0.19-0.16-0.12-0.08-0.04

-0.25-0.20-0.15-0.10-0.05

98.0498.4498.8399.2299.61

97.397.898.498.999.5

23.024.826.628.430.2

0 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.00 0.00 100.00 100.0 32.0

12345

0.0390.0780.1170.1560.195

0.0590.1180.1760.2350.294

0.0500.1010.1510.2020.253

0.0390.0790.1190.1580.198

0.0260.0520.0780.1040.130

0.0050.0110.0160.0220.027

0.0050.0110.0160.0210.027

0.0000.000

-0.001-0.001-0.001

0.040.080.120.160.20

0.050.100.160.210.26

100.39100.78101.17101.56101.95

100.5101.1101.7102.2102.8

33.835.637.439.241.0

6789

10

0.2340.2730.3120.3520.391

0.3540.4130.4720.5320.591

0.3030.3540.4050.4560.507

0.2380.2770.3170.3570.397

0.1560.1820.2080.2350.261

0.0330.0380.0440.0500.055

0.0320.0380.0430.0490.054

-0.001-0.001-0.002-0.002-0.002

0.240.280.320.360.40

0.310.360.420.470.52

102.34102.73103.12103.51103.90

103.3103.9104.4105.0105.6

42.844.646.448.250.0

1112131415

0.4310.4700.5100.5490.589

0.6510.7110.7700.8300.890

0.5580.6090.6600.7110.762

0.4370.4770.5170.5570.597

0.2870.3130.3400.3660.393

0.0610.0670.0720.0780.084

0.0600.0650.0710.0770.082

-0.002-0.002-0.002-0.002-0.002

0.440.480.520.560.60

0.570.630.680.730.78

104.29104.68105.07105.46105.85

106.1106.7107.2107.8108.4

51.853.655.457.259.0

1617181920

0.6290.6690.7090.7490.790

0.9501.0101.0711.1311.192

0.8140.8650.9160.9681.019

0.6370.6770.7180.7580.798

0.4190.4460.4720.4990.525

0.0900.0950.1010.1070.113

0.0880.0940.1000.1050.111

-0.002-0.002-0.003-0.003-0.003

0.640.680.720.760.80

0.840.890.941.001.05

106.24106.63107.02107.41107.79

109.0109.5110.1110.7111.2

60.862.664.466.268.0

2122232425

0.8300.8700.9110.9510.992

1.2521.3131.3731.4341.495

1.0711.1221.1741.2261.277

0.8380.8790.9190.9601.000

0.5520.5780.6050.6320.659

0.1190.1250.1310.1370.143

0.1170.1230.1290.1350.141

-0.003-0.003-0.003-0.003-0.002

0.840.880.920.961.00

1.101.161.211.261.31

108.18108.57108.96109.35109.73

111.8112.4113.0113.5114.1

69.871.673.475.277.0

2627282930

1.0331.0741.1141.1551.196

1.5561.6171.6781.7401.801

1.3291.3811.4331.4851.537

1.0411.0811.1221.1631.203

0.6850.7120.7390.7660.793

0.1490.1550.1610.1670.173

0.1470.1530.1590.1650.171

-0.002-0.002-0.002-0.002-0.002

1.051.091.131.171.21

1.371.421.471.531.58

110.12110.51110.90111.29111.67

114.7115.3115.9116.5117.1

78.880.682.484.286.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

286

3132333435

1.2381.2791.3201.3621.403

1.8621.9241.9862.0472.109

1.5891.6411.6931.7451.797

1.2441.2851.3261.3661.407

0.8200.8470.8740.9010.928

0.1790.1850.1910.1970.204

0.1770.1830.1890.1950.201

-0.002-0.002-0.002-0.002-0.001

1.251.291.341.381.42

1.631.691.741.791.84

112.06112.45112.83113.22113.61

117.6118.2118.8119.4120.0

87.889.691.493.295.0

3637383940

1.4451.4861.5281.5701.612

2.1712.2332.2952.3572.420

1.8491.9021.9542.0062.059

1.4481.4891.5301.5711.612

0.9550.9831.0101.0371.065

0.2100.2160.2220.2290.235

0.2070.2140.2200.2260.232

-0.001-0.001-0.001-0.0010.000

1.461.501.551.591.63

1.901.952.002.062.11

114.00114.38114.77115.15115.54

120.6121.2121.8122.4123.0

96.898.6

100.4102.2104.0

4142434445

1.6541.6961.7381.7801.823

2.4822.5452.6072.6702.733

2.1112.1642.2162.2692.322

1.6531.6941.7351.7761.817

1.0921.1191.1471.1741.202

0.2410.2480.2540.2600.267

0.2390.2450.2510.2580.264

0.0000.0000.0000.0000.001

1.671.711.761.801.84

2.162.222.272.332.38

115.93116.31116.70117.08117.47

123.6124.2124.8125.4126.0

105.8107.6109.4111.2113.0

4647484950

1.8651.9081.9501.9932.036

2.7952.8582.9212.9843.048

2.3742.4272.4802.5322.585

1.8581.8991.9411.9822.023

1.2291.2571.2841.3121.340

0.2730.2800.2860.2920.299

0.2710.2770.2840.2900.296

0.0010.0010.0020.0020.002

1.881.921.972.012.05

2.432.492.542.602.65

117.86118.24118.63119.01119.40

126.7127.3127.9128.5129.1

114.8116.6118.4120.2122.0

5152535455

2.0792.1222.1652.2082.251

3.1113.1743.2383.3013.365

2.6382.6912.7442.7972.850

2.0642.1062.1472.1882.230

1.3681.3951.4231.4511.479

0.3050.3120.3190.3250.332

0.3030.3100.3160.3230.329

0.0030.0030.0030.0040.004

2.092.142.182.222.26

2.702.762.812.872.92

119.78120.17120.55120.94121.32

129.7130.3131.0131.6132.2

123.8125.6127.4129.2131.0

5657585960

2.2942.3382.3812.4252.468

3.4293.4923.5563.6203.685

2.9032.9563.0093.0623.116

2.2712.3122.3542.3952.436

1.5071.5351.5631.5911.619

0.3380.3450.3520.3580.365

0.3360.3430.3490.3560.363

0.0040.0050.0050.0060.006

2.312.352.392.442.48

2.973.033.083.143.19

121.71122.09122.47122.86123.24

132.8133.5134.1134.7135.3

132.8134.6136.4138.2140.0

6162636465

2.5122.5562.6002.6432.687

3.7493.8133.8773.9424.006

3.1693.2223.2753.3293.382

2.4782.5192.5612.6022.644

1.6471.6751.7031.7321.760

0.3720.3780.3850.3920.399

0.3690.3760.3830.3900.397

0.0070.0070.0080.0080.009

2.522.572.612.652.69

3.243.303.353.413.46

123.63124.01124.39124.78125.16

136.0136.6137.2137.9138.5

141.8143.6145.4147.2149.0

6667686970

2.7322.7762.8202.8642.909

4.0714.1364.2004.2654.330

3.4363.4893.5433.5963.650

2.6852.7272.7682.8102.851

1.7881.8171.8451.8731.902

0.4050.4120.4190.4260.433

0.4030.4100.4170.4240.431

0.0090.0100.0100.0110.011

2.742.782.822.872.91

3.513.573.623.683.73

125.54125.93126.31126.69127.08

139.2139.8140.4141.1141.7

150.8152.6154.4156.2158.0

7172737475

2.9532.9983.0433.0873.132

4.3954.4604.5264.5914.656

3.7033.7573.8103.8643.918

2.8932.9342.9763.0173.059

1.9301.9591.9882.0162.045

0.4400.4460.4530.4600.467

0.4380.4450.4520.4590.466

0.0120.0120.0130.0140.014

2.953.003.043.093.13

3.783.843.893.954.00

127.46127.84128.22128.61128.99

142.4143.0143.7144.3145.0

159.8161.6163.4165.2167.0

7677787980

3.1773.2223.2673.3123.358

4.7224.7884.8534.9194.985

3.9714.0254.0794.1334.187

3.1003.1423.1843.2253.267

2.0742.1022.1312.1602.189

0.4740.4810.4880.4950.502

0.4730.4800.4870.4940.501

0.0150.0150.0160.0170.017

3.173.223.263.313.35

4.054.114.164.224.27

129.37129.75130.13130.52130.90

145.6146.3146.9147.6148.3

168.8170.6172.4174.2176.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

287

8182838485

3.4033.4483.4943.5393.585

5.0515.1175.1835.2495.315

4.2404.2944.3484.4024.456

3.3083.3503.3913.4333.474

2.2182.2472.2762.3052.334

0.5090.5160.5230.5300.538

0.5080.5160.5230.5300.537

0.0180.0190.0200.0200.021

3.393.443.483.533.57

4.324.384.434.494.54

131.28131.66132.04132.42132.80

148.9149.6150.2150.9151.6

177.8179.6181.4183.2185.0

8687888990

3.6313.6773.7223.7683.814

5.3825.4485.5145.5815.648

4.5104.5644.6184.6724.726

3.5163.5573.5993.6403.682

2.3632.3922.4212.4502.480

0.5450.5520.5590.5660.573

0.5440.5520.5590.5660.573

0.0220.0220.0230.0240.025

3.623.663.713.753.80

4.604.654.714.774.82

133.18133.57133.95134.33134.71

152.2152.9153.6154.3154.9

186.8188.6190.4192.2194.0

9192939495

3.8603.9073.9533.9994.046

5.7145.7815.8485.9155.982

4.7814.8354.8894.9434.997

3.7233.7653.8063.8483.889

2.5092.5382.5682.5972.626

0.5800.5880.5950.6020.609

0.5810.5880.5950.6030.610

0.0260.0260.0270.0280.029

3.843.893.933.984.02

4.874.934.985.045.09

135.09135.47135.85136.23136.61

155.6156.3157.0157.7158.3

195.8197.6199.4201.2203.0

96979899

100

4.0924.1384.1854.2324.279

6.0496.1176.1846.2516.319

5.0525.1065.1605.2155.269

3.9313.9724.0134.0554.096

2.6562.6852.7152.7442.774

0.6170.6240.6310.6390.646

0.6180.6250.6320.6400.647

0.0300.0310.0310.0320.033

4.074.114.164.204.25

5.155.205.265.325.37

136.99137.37137.75138.13138.51

159.0159.7160.4161.1161.8

204.8206.6208.4210.2212.0

101102103104105

4.3254.3724.4194.4664.513

6.3866.4546.5226.5906.658

5.3235.3785.4325.4875.541

4.1384.1794.2204.2624.303

2.8042.8332.8632.8932.923

0.6530.6610.6680.6750.683

0.6550.6620.6700.6770.685

0.0340.0350.0360.0370.038

4.304.344.394.434.48

5.425.485.535.595.64

138.88139.26139.64140.02140.40

162.5163.2163.9164.6165.3

213.8215.6217.4219.2221.0

106107108109110

4.5614.6084.6554.7024.750

6.7256.7946.8626.9306.998

5.5955.6505.7055.7595.814

4.3444.3854.4274.4684.509

2.9532.9833.0123.0423.072

0.6900.6980.7050.7130.720

0.6930.7000.7080.7150.723

0.0390.0400.0410.0420.043

4.534.574.624.664.71

5.705.755.815.875.92

140.78141.16141.54141.91142.29

166.0166.7167.4168.1168.8

222.8224.6226.4228.2230.0

111112113114115

4.7984.8454.8934.9414.988

7.0667.1357.2037.2727.341

5.8685.9235.9776.0326.087

4.5504.5914.6334.6744.715

3.1023.1333.1633.1933.223

0.7270.7350.7430.7500.758

0.7310.7380.7460.7540.761

0.0440.0450.0460.0470.048

4.764.804.854.904.94

5.976.036.086.146.19

142.67143.05143.43143.80144.18

169.5170.2170.9171.6172.4

231.8233.6235.4237.2239.0

116117118119120

5.0365.0845.1325.1805.228

7.4097.4787.5477.6167.685

6.1416.1966.2516.3066.360

4.7564.7974.8384.8794.920

3.2533.2833.3143.3443.374

0.7650.7730.7800.7880.795

0.7690.7770.7850.7920.800

0.0490.0500.0510.0520.053

4.995.045.095.135.18

6.256.306.366.426.47

144.56144.94145.31145.69146.07

173.1173.8174.5175.2176.0

240.8242.6244.4246.2248.0

121122123124125

5.2775.3255.3735.4225.470

7.7547.8237.8927.9628.031

6.4156.4706.5256.5796.634

4.9615.0025.0435.0845.124

3.4053.4353.4663.4963.527

0.8030.8110.8180.8260.834

0.8080.8160.8240.8320.839

0.0550.0560.0570.0580.059

5.235.275.325.375.41

6.536.586.646.696.75

146.44146.82147.20147.57147.95

176.7177.4178.2178.9179.6

249.8251.6253.4255.2257.0

126127128129130

5.5195.5675.6165.6655.714

8.1018.1708.2408.3098.379

6.6896.7446.7996.8546.909

5.1655.2065.2475.2885.328

3.5573.5883.6193.6493.680

0.8410.8490.8570.8650.872

0.8470.8550.8630.8710.879

0.0600.0620.0630.0640.065

5.465.515.565.605.65

6.816.866.926.977.03

148.33148.70149.08149.46149.83

180.4181.1181.8182.6183.3

258.8260.6262.4264.2266.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

288

131132133134135

5.7635.8125.8615.9105.959

8.4498.5198.5898.6598.729

6.9647.0197.0747.1297.184

5.3695.4105.4505.4915.532

3.7113.7423.7723.8033.834

0.8800.8880.8960.9030.911

0.8870.8950.9030.9110.919

0.0660.0680.0690.0700.072

5.705.755.795.845.89

7.097.147.207.257.31

150.21150.58150.96151.33151.71

184.1184.8185.6186.3187.1

267.8269.6271.4273.2275.0

136137138139140

6.0086.0576.1076.1566.206

8.7998.8698.9409.0109.081

7.2397.2947.3497.4047.459

5.5725.6135.6535.6945.735

3.8653.8963.9273.9583.989

0.9190.9270.9350.9420.950

0.9270.9350.9430.9510.959

0.0730.0740.0750.0770.078

5.945.996.036.086.13

7.377.427.487.537.59

152.08152.46152.83153.21153.58

187.8188.6189.4190.1190.9

276.8278.6280.4282.2284.0

141142143144145

6.2556.3056.3556.4046.454

9.1519.2229.2929.3639.434

7.5147.5697.6247.6797.734

5.7755.8155.8565.8965.937

4.0204.0514.0834.1144.145

0.9580.9660.9740.9820.990

0.9670.9760.9840.9921.000

0.0790.0810.0820.0840.085

6.186.236.286.336.37

7.657.707.767.817.87

153.96154.33154.71155.08155.46

191.7192.4193.2194.0194.7

285.8287.6289.4291.2293.0

146147148149150

6.5046.5546.6046.6546.704

9.5059.5769.6479.7189.789

7.7897.8447.9007.9558.010

5.9776.0176.0586.0986.138

4.1764.2084.2394.2704.302

0.9981.0061.0131.0211.029

1.0081.0161.0251.0331.041

0.0860.0880.0890.0910.092

6.426.476.526.576.62

7.937.988.048.098.15

155.83156.20156.58156.95157.33

195.5196.3197.1197.9198.6

294.8296.6298.4300.2302.0

151152153154155

6.7546.8056.8556.9056.956

9.8609.931

10.00310.07410.145

8.0658.1208.1758.2318.286

6.1796.2196.2596.2996.339

4.3334.3654.3964.4284.459

1.0371.0451.0531.0611.069

1.0491.0581.0661.0741.082

0.0940.0950.0960.0980.099

6.676.726.776.826.87

8.218.268.328.378.43

157.70158.07158.45158.82159.19

199.4200.2201.0201.8202.6

303.8305.6307.4309.2311.0

156157158159160

7.0067.0577.1077.1587.209

10.21710.28810.36010.43210.503

8.3418.3968.4528.5078.562

6.3806.4206.4606.5006.540

4.4914.5234.5544.5864.618

1.0771.0851.0941.1021.110

1.0911.0991.1071.1161.124

0.1010.1020.1040.1060.107

6.926.977.027.077.12

8.498.548.608.658.71

159.56159.94160.31160.68161.05

203.4204.2205.0205.8206.6

312.8314.6316.4318.2320.0

161162163164165

7.2607.3107.3617.4127.463

10.57510.64710.71910.79110.863

8.6188.6738.7288.7838.839

6.5806.6206.6606.7016.741

4.6504.6814.7134.7454.777

1.1181.1261.1341.1421.150

1.1321.1411.1491.1581.166

0.1090.1100.1120.1130.115

7.177.227.277.337.37

8.778.828.888.938.99

161.43161.80162.17162.54162.91

207.4208.2209.0209.8210.6

321.8323.6325.4327.2329.0

166167168169170

7.5157.5667.6177.6687.720

10.93511.00711.08011.15211.224

8.8948.9499.0059.0609.115

6.7816.8216.8616.9016.941

4.8094.8414.8734.9054.937

1.1581.1671.1751.1831.191

1.1751.1831.1911.2001.208

0.1170.1180.1200.1220.123

7.437.487.537.587.63

9.059.109.169.219.27

163.29163.66164.03164.40164.77

211.5212.3213.1213.9214.8

330.8332.6334.4336.2338.0

171172173174175

7.7717.8237.8747.9267.977

11.29711.36911.44211.51411.587

9.1719.2269.2829.3379.392

6.9817.0217.0607.1007.140

4.9695.0015.0335.0665.098

1.1991.2071.2161.2241.232

1.2171.2251.2341.2421.251

0.1250.1270.1280.1300.132

7.687.737.797.847.89

9.339.389.449.499.55

165.14165.51165.89166.26166.63

215.6216.4217.3218.1218.9

339.8341.6343.4345.2347.0

176177178179180

8.0298.0818.1338.1858.237

11.66011.73311.80511.87811.951

9.4489.5039.5599.6149.669

7.1807.2207.2607.3007.340

5.1305.1625.1955.2275.259

1.2401.2491.2571.2651.273

1.2601.2681.2771.2851.294

0.1340.1350.1370.1390.141

7.947.998.058.108.15

9.619.669.729.779.83

167.00167.37167.74168.11168.48

219.8220.6221.5222.3223.2

348.8350.6352.4354.2356.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

289

181182183184185

8.2898.3418.3938.4458.497

12.02412.09712.17012.24312.317

9.7259.7809.8369.8919.947

7.3807.4207.4607.5007.540

5.2925.3245.3575.3895.422

1.2821.2901.2981.3071.315

1.3031.3111.3201.3291.337

0.1420.1440.1460.1480.150

8.208.258.318.368.41

9.899.94

10.0010.0510.11

168.85169.22169.59169.96170.33

224.0224.9225.7226.6227.4

357.8359.6361.4363.2365.0

186187188189190

8.5508.6028.6548.7078.759

12.39012.46312.53712.61012.684

10.00210.05710.11310.16810.224

7.5797.6197.6597.6997.739

5.4545.4875.5205.5525.585

1.3231.3321.3401.3481.357

1.3461.3551.3631.3721.381

0.1510.1530.1550.1570.159

8.468.518.578.628.67

10.1710.2210.2810.3310.39

170.70171.07171.43171.80172.17

228.3229.2230.0230.9231.8

366.8368.6370.4372.2374.0

191192193194195

8.8128.8658.9178.9709.023

12.75712.83112.90412.97813.052

10.27910.33510.39010.44610.501

7.7797.8197.8597.8997.939

5.6185.6505.6835.7165.749

1.3651.3731.3821.3901.399

1.3891.3981.4071.4161.425

0.1610.1630.1650.1660.168

8.728.788.838.888.93

10.4510.5010.5610.6110.67

172.54172.91173.28173.65174.02

232.7233.5234.4235.3236.2

375.8377.6379.4381.2383.0

196197198199200

9.0769.1299.1829.2359.288

13.12613.19913.27313.34713.421

10.55710.61210.66810.72310.779

7.9798.0198.0598.0998.138

5.7825.8155.8475.8805.913

1.4071.4151.4241.4321.441

1.4331.4421.4511.4601.469

0.1700.1720.1740.1760.178

8.999.049.099.159.20

10.7310.7810.8410.8910.95

174.38174.75175.12175.49175.86

237.1238.0238.9239.8240.7

384.8386.6388.4390.2392.0

201202203204205

9.3419.3959.4489.5019.555

13.49513.56913.64413.71813.792

10.83410.89010.94511.00111.056

8.1788.2188.2588.2988.338

5.9465.9796.0136.0466.079

1.4491.4581.4661.4751.483

1.4771.4861.4951.5041.513

0.1800.1820.1840.1860.188

9.259.319.369.429.47

11.0111.0611.1211.1711.23

176.22176.59176.96177.33177.69

241.6242.5243.4244.3245.2

393.8395.6397.4399.2401.0

206207208209210

9.6089.6629.7159.7699.822

13.86613.94114.01514.09014.164

11.11211.16711.22311.27811.334

8.3788.4188.4588.4998.539

6.1126.1456.1786.2116.245

1.4921.5001.5091.5171.526

1.5221.5311.5401.5491.558

0.1900.1920.1950.1970.199

9.529.589.639.699.74

11.2911.3411.4011.4511.51

178.06178.43178.79179.16179.53

246.1247.0247.9248.9249.8

402.8404.6406.4408.2410.0

211212213214215

9.8769.9309.984

10.03810.092

14.23914.31314.38814.46314.537

11.38911.44511.50111.55611.612

8.5798.6198.6598.6998.739

6.2786.3116.3456.3786.411

1.5341.5431.5511.5601.569

1.5671.5751.5841.5931.602

0.2010.2030.2050.2070.209

9.799.859.909.96

10.01

11.5711.6211.6811.7311.79

179.89180.26180.63180.99181.36

250.7251.7252.6253.5254.5

411.8413.6415.4417.2419.0

216217218219220

10.14610.20010.25410.30810.362

14.61214.68714.76214.83714.912

11.66711.72311.77811.83411.889

8.7798.8198.8608.9008.940

6.4456.4786.5126.5456.579

1.5771.5861.5941.6031.612

1.6111.6201.6291.6391.648

0.2120.2140.2160.2180.220

10.0710.1210.1810.2310.29

11.8511.9011.9612.0112.07

181.72182.09182.46182.82183.19

255.4256.3257.3258.2259.2

420.8422.6424.4426.2428.0

221222223224225

10.41710.47110.52510.58010.634

14.98715.06215.13715.21215.287

11.94512.00012.05612.11112.167

8.9809.0209.0619.1019.141

6.6126.6466.6806.7136.747

1.6201.6291.6381.6461.655

1.6571.6661.6751.6841.693

0.2220.2250.2270.2290.231

10.3510.4010.4610.5110.57

12.1312.1812.2412.2912.35

183.55183.92184.28184.65185.01

260.2261.1262.1263.0264.0

429.8431.6433.4435.2437.0

226227228229230

10.68910.74310.79810.85310.907

15.36215.43815.51315.58815.664

12.22212.27812.33412.38912.445

9.1819.2229.2629.3029.343

6.7816.8146.8486.8826.916

1.6631.6721.6811.6901.698

1.7021.7111.7201.7291.739

0.2340.2360.2380.2410.243

10.6210.6810.7410.7910.85

12.4112.4612.5212.5712.63

185.38185.74186.11186.47186.84

265.0266.0266.9267.9268.9

438.8440.6442.4444.2446.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

290

231232233234235

10.96211.01711.07211.12711.182

15.73915.81515.89015.96616.041

12.50012.55612.61112.66712.722

9.3839.4239.4649.5049.545

6.9496.9837.0177.0517.085

1.7071.7161.7241.7331.742

1.7481.7571.7661.7751.784

0.2450.2480.2500.2520.255

10.9110.9611.0211.0711.13

12.6912.7412.8012.8512.91

187.20187.56187.93188.29188.66

269.9270.9271.8272.8273.8

447.8449.6451.4453.2455.0

236237238239240

11.23711.29211.34711.40311.458

16.11716.19316.26916.34416.420

12.77812.83312.88912.94413.000

9.5859.6269.6669.7079.747

7.1197.1537.1877.2217.255

1.7511.7591.7681.7771.786

1.7941.8031.8121.8211.831

0.2570.2590.2620.2640.267

11.1911.2411.3011.3511.41

12.9713.0213.0813.1313.19

189.02189.38189.75190.11190.47

274.8275.8276.8277.9278.9

456.8458.6460.4462.2464.0

241242243244245

11.51311.56911.62411.68011.735

16.49616.57216.64816.72416.800

13.05613.11113.16713.22213.278

9.7889.8289.8699.9099.950

7.2897.3237.3577.3927.426

1.7941.8031.8121.8211.829

1.8401.8491.8581.8681.877

0.2690.2710.2740.2760.279

11.4711.5211.5811.6411.69

13.2513.3013.3613.4113.47

190.84191.20191.56191.92192.29

279.9280.9281.9282.9284.0

465.8467.6469.4471.2473.0

246247248249250

11.79111.84611.90211.95812.013

16.87616.95217.02817.10417.181

13.33313.38913.44413.50013.555

9.99110.03110.07210.11310.153

7.4607.4947.5287.5637.597

1.8381.8471.8561.8651.874

1.8861.8951.9051.9141.923

0.2810.2840.2860.2890.291

11.7511.8111.8711.9211.98

13.5313.5813.6413.6913.75

192.65193.01193.37193.74194.10

285.0286.0287.1288.1289.2

474.8476.6478.4480.2482.0

251252253254255

12.06912.12512.18112.23712.293

17.25717.33317.40917.48617.562

13.61113.66613.72213.77713.833

10.19410.23510.27610.31610.357

7.6317.6667.7007.7347.769

1.8821.8911.9001.9091.918

1.9331.9421.9511.9611.970

0.2940.2960.2990.3010.304

12.0412.0912.1512.2112.26

13.8113.8613.9213.9714.03

194.46194.82195.18195.55195.91

483.8485.6487.4489.2491.0

256257258259260

12.34912.40512.46112.51812.574

17.63917.71517.79217.86817.945

13.88813.94413.99914.05514.110

10.39810.43910.48010.52010.561

7.8037.8387.8727.9077.941

1.9271.9361.9441.9531.962

1.9801.9891.9982.0082.017

0.3070.3090.3120.3140.317

12.3212.3812.4412.4912.55

14.0914.1414.2014.2514.31

196.27196.63196.99197.35197.71

492.8494.6496.4498.2500.0

261262263364265

12.63012.68712.74312.79912.856

18.02118.09818.17518.25218.328

14.16614.22114.27714.33214.388

10.60210.64310.68410.72510.766

7.9768.0108.0458.0808.114

1.9711.9801.9891.9982.007

2.0272.0362.0462.0552.064

0.3200.3220.3250.3280.330

12.6112.6712.7212.7812.84

14.3714.4214.4814.5414.59

198.07198.43198.79199.15199.51

501.8503.6505.4507.2509.0

266267268269270

12.91212.96913.02613.08213.139

18.40518.48218.55918.63618.713

14.44314.49914.55414.60914.665

10.80710.84810.88910.93010.971

8.1498.1848.2188.2538.288

2.0162.0252.0342.0432.052

2.0742.0832.0932.1022.112

0.3330.3360.3380.3410.344

12.9012.9613.0113.0713.13

14.6514.7114.7614.8214.88

199.87200.23200.59200.95201.31

510.8512.6514.4516.2518.0

271272273274275

13.19613.25313.31013.36613.423

18.79018.86718.94419.02119.098

14.72014.77614.83114.88714.942

11.01211.05311.09411.13511.176

8.3238.3588.3928.4278.462

2.0612.0702.0782.0872.096

2.1212.1312.1402.1502.159

0.3470.3490.3520.3550.358

13.1913.2513.3013.3613.42

14.9414.9915.0515.1015.16

201.67202.03202.39202.75203.11

519.8521.6523.4525.2527.0

276277278279280

13.48013.53713.59513.65213.709

19.17519.25219.33019.40719.484

14.99815.05315.10915.16415.219

11.21711.25911.30011.34111.382

8.4978.5328.5678.6028.637

2.1052.1142.1232.1322.141

2.1692.1792.1882.1982.207

0.3600.3630.3660.3690.372

13.4813.5413.5913.6513.71

15.2215.2715.3315.3815.44

203.47203.83204.19204.55204.90

528.8530.6532.4534.2536.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

291

281282283284285

13.76613.82313.88113.93813.995

19.56119.63919.71619.79419.871

15.27515.33015.38615.44115.496

11.42311.46511.50611.54711.588

8.6728.7078.7428.7778.812

2.1512.1602.1692.1782.187

2.2172.2262.2362.2462.255

0.3750.3770.3800.3830.386

13.7713.8313.8913.9514.00

15.5015.5515.6115.6615.72

205.26205.62205.98206.34206.70

537.8539.6541.4543.2545.0

286287288289290

14.05314.11014.16814.22614.283

19.94820.02620.10320.18120.259

15.55215.60715.66315.71815.773

11.63011.67111.71211.75311.795

8.8478.8828.9188.9538.988

2.1962.2052.2142.2232.232

2.2652.2752.2842.2942.304

0.3890.3920.3950.3980.401

14.0614.1214.1814.2414.30

15.7815.8315.8915.9416.00

207.05207.41207.77208.13208.48

546.8548.6550.4552.2554.0

291292293294295

14.34114.39914.45614.51414.572

20.33620.41420.49220.56920.647

15.82915.88415.94015.99516.050

11.83611.87711.91911.96012.001

9.0239.0589.0949.1299.164

2.2412.2502.2592.2682.277

2.3132.3232.3332.3422.352

0.4040.4070.4100.4130.416

14.3614.4214.4814.5414.60

16.0616.1116.1716.2216.28

208.84209.20209.56209.91210.27

555.8557.6559.4561.2563.0

296297298299300

14.63014.68814.74614.80414.862

20.72520.80320.88020.95821.036

16.10616.16116.21616.27216.327

12.04312.08412.12612.16712.209

9.2009.2359.2709.3069.341

2.2872.2962.3052.3142.323

2.3622.3712.3812.3912.401

0.4190.4220.4250.4280.431

14.6614.7214.7814.8414.90

16.3416.3916.4516.5016.56

210.63210.98211.34211.70212.05

564.8566.6568.4570.2572.0

301302303304305

14.92014.97815.03615.09515.153

21.11421.19221.27021.34821.426

16.38316.43816.49316.54916.604

12.25012.29112.33312.37412.416

9.3779.4129.4489.4839.519

2.3322.3412.3502.3602.369

2.4102.4202.4302.4402.449

0.4340.4370.4400.4430.446

14.9615.0215.0815.1415.20

16.6216.6716.7316.7816.84

212.41212.76213.12213.48213.83

573.8575.6577.4579.2581.0

306307308309310

15.21115.27015.32815.38615.445

21.50421.58221.66021.73921.817

16.65916.71516.77016.82516.881

12.45712.49912.54012.58212.624

9.5549.5909.6259.6619.696

2.3782.3872.3962.4052.415

2.4592.4692.4792.4882.498

0.4490.4520.4550.4580.462

15.2615.3215.3815.4415.50

16.9016.9517.0117.0617.12

214.19214.54214.90215.25215.61

582.8584.6586.4588.2590.0

311312313314315

15.50315.56215.62115.67915.738

21.89521.97322.05122.13022.208

16.93616.99117.04617.10217.157

12.66512.70712.74812.79012.831

9.7329.7689.8039.8399.875

2.4242.4332.4422.4512.461

2.5082.5182.5282.5382.547

0.4650.4680.4710.4740.478

15.5615.6215.6815.7415.80

17.1817.2317.2917.3417.40

215.96216.32216.67217.03217.38

591.8593.6595.4597.2599.0

316317318319320

15.79715.85615.91415.97316.032

22.28622.36522.44322.52222.600

17.21217.26817.32317.37817.434

12.87312.91512.95612.99813.040

9.9109.9469.982

10.01810.054

2.4702.4792.4882.4972.507

2.5572.5672.5772.5872.597

0.4810.4840.4870.4900.494

15.8615.9215.9816.0416.10

17.4617.5117.5717.6217.68

217.74218.09218.44218.80219.15

600.8602.6604.4606.2608.0

321322323324325

16.09116.15016.20916.26816.327

22.67822.75722.83522.91422.993

17.48917.54417.59917.65517.710

13.08113.12313.16513.20613.248

10.08910.12510.16110.19710.233

2.5162.5252.5342.5442.553

2.6072.6172.6262.6362.646

0.4970.5000.5030.5070.510

16.1616.2216.2816.3416.40

17.7417.7917.8517.9017.96

219.51219.86220.21220.57220.92

609.8611.6613.4615.2617.0

326327328329330

16.38716.44616.50516.56416.624

23.07123.15023.22823.30723.386

17.76517.82017.87617.93117.986

13.29013.33113.37313.41513.457

10.26910.30510.34110.37710.413

2.5622.5712.5812.5902.599

2.6562.6662.6762.6862.696

0.5130.5170.5200.5230.527

16.4616.5216.5816.6416.70

18.0218.0718.1318.1818.24

221.27221.63221.98222.33222.68

618.8620.6622.4624.2626.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

292

331332333334335

16.68316.74216.80216.86116.921

23.46423.54323.62223.70123.780

18.04118.09718.15218.20718.262

13.49813.54013.58213.62413.665

10.44910.48510.52110.55710.593

2.6092.6182.6272.6362.646

2.7062.7162.7262.7362.746

0.5300.5330.5370.5400.544

16.7616.8216.8816.9417.00

18.3018.3518.4118.4618.52

223.04223.39223.74224.09224.45

627.8629.6631.4633.2635.0

336337338339340

16.98017.04017.10017.15917.219

23.85823.93724.01624.09524.174

18.31818.37318.42818.48318.538

13.70713.74913.79113.83313.874

10.62910.66510.70110.73710.774

2.6552.6642.6742.6832.692

2.7562.7662.7762.7862.796

0.5470.5500.5540.5570.561

17.0717.1317.1917.2417.31

18.5818.6318.6918.7418.80

224.80225.15225.50225.85226.21

636.8638.6640.4642.2644.0

341342343344345

17.27917.33917.39917.45817.518

24.25324.33224.41124.49024.569

18.59418.64918.70418.75918.814

13.91613.95814.00014.04214.084

10.81010.84610.88210.91810.955

2.7022.7112.7202.7302.739

2.8062.8162.8262.8362.846

0.5640.5680.5710.5750.578

17.3717.4317.4917.5517.61

18.8618.9118.9719.0219.08

226.56226.91227.26227.61227.96

645.8647.6649.4651.2653.0

346347348349350

17.57817.63817.69817.75917.819

24.64824.72724.80624.88524.964

18.87018.92518.98019.03519.090

14.12614.16714.20914.25114.293

10.99111.02711.06411.10011.136

2.7482.7582.7672.7762.786

2.8562.8662.8762.8862.896

0.5820.5850.5890.5920.596

17.6817.7417.8017.8617.92

19.1419.1919.2519.3019.36

228.31228.66229.02229.37229.72

654.8656.6658.4660.2662.0

351352353354355

17.87917.93917.99918.06018.120

25.04425.12325.20225.28125.360

19.14619.20119.25619.31119.366

14.33514.37714.41914.46114.503

11.17311.20911.24511.28211.318

2.7952.8052.8142.8232.833

2.9062.9162.9262.9372.947

0.5990.6030.6070.6100.614

17.9818.0418.1018.1618.22

19.4219.4719.5319.5819.64

230.07230.42230.77231.12231.47

663.8665.6667.4669.2671.0

356357358359360

18.18018.24118.30118.36218.422

25.44025.51925.59825.67825.757

19.42219.47719.53219.58719.642

14.54514.58714.62914.67114.713

11.35511.39111.42811.46411.501

2.8422.8512.8612.8702.880

2.9572.9672.9772.9872.997

0.6170.6210.6250.6280.632

18.2918.3518.4118.4718.53

19.7019.7519.8119.8619.92

231.82232.17232.52232.87233.21

672.8674.6676.4678.2680.0

361362363364365

18.48318.54318.60418.66518.725

25.83625.91625.99526.07526.154

19.69719.75319.80819.86319.918

14.75514.79714.83914.88114.923

11.53711.57411.61011.64711.683

2.8892.8992.9082.9172.927

3.0073.0183.0283.0383.048

0.6360.6390.6430.6470.650

18.5918.6518.7118.7718.83

19.9820.0320.0920.1420.20

233.56233.91234.26234.61234.96

681.8683.6685.4687.2689.0

366367368369370

18.78618.84718.90818.96919.030

26.23326.31326.39226.47226.552

19.97320.02820.08320.13920.194

14.96515.00715.04915.09115.133

11.72011.75711.79311.83011.867

2.9362.9462.9552.9652.974

3.0583.0683.0793.0893.099

0.6540.6580.6620.6650.669

18.8918.9619.0219.0819.14

20.2620.3120.3720.4220.48

235.31235.66236.00236.35236.70

690.8692.6694.4696.2698.0

371372373374375

19.09119.15219.21319.27419.335

26.63126.71126.79026.87026.950

20.24920.30420.35920.41420.469

15.17515.21715.25915.30115.343

11.90311.94011.97712.01312.050

2.9832.9933.0023.0123.021

3.1093.1193.1303.1403.150

0.6730.6770.6800.6840.688

19.2019.2619.3319.3919.45

20.5420.5920.6520.7020.76

237.05237.40237.74238.09238.44

699.8701.6703.4705.2707.0

376377378379380

19.39619.45719.51819.57919.641

27.02927.10927.18927.26827.348

20.52520.58020.63520.69020.745

15.38515.42715.46915.51115.554

12.08712.12412.16012.19712.234

3.0313.0403.0503.0593.069

3.1603.1713.1813.1913.201

0.6920.6960.7000.7030.707

19.5119.5719.6419.7019.76

20.8220.8720.9320.9821.04

238.79239.13239.48239.83240.18

708.8710.6712.4714.2716.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

293

381382383384385

19.70219.76319.82519.88619.947

27.42827.50727.58727.66727.747

20.80020.85520.91120.96621.021

15.59615.63815.68015.72215.764

12.27112.30812.34512.38212.418

3.0783.0883.0973.1073.116

3.2123.2223.2323.2423.253

0.7110.7150.7190.7230.727

19.8219.8919.9520.0120.07

21.1021.1521.2121.2621.32

240.52240.87241.22241.56241.91

717.8719.6721.4723.2725.0

386387388389390

20.00920.07020.13220.19320.255

27.82727.90727.98628.06628.146

21.07621.13121.18621.24121.297

15.80615.84915.89115.93315.975

12.45512.49212.52912.56612.603

3.1263.1353.1453.1543.164

3.2633.2733.2843.2943.304

0.7310.7350.7380.7420.746

20.1320.1920.2620.3220.38

21.3821.4321.4921.5421.60

242.26242.60242.95243.29243.64

726.8728.6730.4732.2734.0

391392393394395

20.31720.37820.44020.50220.563

28.22628.30628.38628.46628.546

21.35221.40721.46221.51721.572

16.01716.05916.10216.14416.186

12.64012.67712.71412.75112.788

3.1733.1833.1923.2023.212

3.3153.3253.3353.3463.356

0.7500.7540.7580.7620.766

20.4420.5020.5720.6320.69

21.6621.7121.7721.8221.88

243.99244.33244.68245.02245.37

735.8737.6739.4741.2743.0

396397398399400

20.62520.68720.74820.81020.872

28.62628.70628.78628.86628.946

21.62721.68321.73821.79321.848

16.22816.27016.31316.35516.397

12.82512.86212.89912.93712.974

3.2213.2313.2403.2503.259

3.3663.3773.3873.3973.408

0.7700.7740.7780.7820.787

20.7520.8120.8820.9421.00

21.9421.9922.0522.1022.16

245.71246.06246.40246.75247.09

744.8746.6748.4750.2752.0

401402403404405

29.02629.10629.18629.26629.346

21.90321.95822.01422.06922.124

16.43916.48216.52416.56616.608

13.01113.04813.08513.12213.159

3.2693.2783.2883.2983.307

3.4183.4283.4393.4493.460

0.7910.7950.7990.8030.807

21.0621.1221.1921.2521.31

22.2222.2722.3322.3822.44

247.44247.78248.13248.47248.81

753.8755.6757.4759.2761.0

406407408409410

29.42729.50729.58729.66729.747

22.17922.23422.28922.34522.400

16.65116.69316.73516.77816.820

13.19713.23413.27113.30813.346

3.3173.3263.3363.3463.355

3.4703.4803.4913.5013.512

0.8110.8150.8190.8240.828

21.3721.4321.5021.5621.62

22.5022.5522.6122.6622.72

249.16249.50249.85250.19250.53

762.8764.6766.4768.2770.0

411412413414415

29.82729.90829.98830.06830.148

22.45522.51022.56522.62022.676

16.86216.90416.94716.98917.031

13.38313.42013.45713.49513.532

3.3653.3743.3843.3943.403

3.5223.5333.5433.5533.564

0.8320.8360.8400.8440.849

21.6821.7521.8121.8721.93

22.7822.8322.8922.9523.00

250.88251.22251.56251.91252.25

771.8773.6775.4777.2779.0

416417418419420

30.22930.30930.38930.47030.550

22.73122.78622.84122.89622.952

17.07417.11617.15817.20117.243

13.56913.60713.64413.68213.719

3.4133.4233.4323.4423.451

3.5743.5853.5953.6063.616

0.8530.8570.8610.8660.870

22.0022.0622.1222.1922.25

23.0623.1223.1823.2323.29

252.59252.93253.28253.62253.96

780.8782.6784.4786.2788.0

421422423424425

30.63030.71130.79130.87130.952

23.00723.06223.11723.17223.228

17.28517.32817.37017.41317.455

13.75613.79413.83113.86913.906

3.4613.4713.4803.4903.500

3.6273.6373.6483.6583.669

0.8740.8780.8830.8870.891

22.3122.3822.4422.5022.56

23.3523.4023.4623.5223.57

254.30254.65254.99255.33255.67

789.8791.6793.4795.2797.0

426427428429430

31.03231.11231.19331.27331.354

23.28323.33823.39323.44923.504

17.49717.54017.58217.62417.667

13.94413.98114.01914.05614.094

3.5093.5193.5293.5383.548

3.6793.6903.7003.7113.721

0.8960.9000.9040.9090.913

22.6322.6922.7522.8222.88

23.6323.6923.7423.8023.86

256.01256.35256.70257.04257.38

798.8800.6802.4804.2806.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

294

431432433434435

31.43431.51531.59531.67631.756

23.55923.61423.67023.72523.780

17.70917.75217.79417.83717.879

14.13114.16914.20614.24414.281

3.5583.5673.5773.5873.596

3.7323.7423.7533.7643.774

0.9170.9220.9260.9300.935

22.9423.0123.0723.1323.19

23.9223.9724.0324.0924.14

257.72258.06258.40258.74259.08

807.8809.6811.4813.2815.0

436437438439440

31.83731.91731.99832.07832.159

23.83523.89123.94624.00124.057

17.92117.96418.00618.04918.091

14.31914.35614.39414.43214.469

3.6063.6163.6263.6353.645

3.7853.7953.8063.8163.827

0.9390.9440.9480.9530.957

23.2623.3223.3823.4523.51

24.2024.2624.3224.3724.43

259.42259.76260.10260.44260.78

816.8818.6820.4822.2824.0

441442443444445

32.23932.32032.40032.48132.562

24.11224.16724.22324.27824.333

18.13418.17618.21818.26118.303

14.50714.54514.58214.62014.658

3.6553.6643.6743.6843.694

3.8383.8483.8593.8693.880

0.9610.9660.9700.9750.979

23.5723.6423.7023.7723.83

24.4924.5424.6024.6624.71

261.12261.46261.80262.14262.48

825.8827.6829.4831.2833.0

446447448449450

32.64232.72332.80332.88432.965

24.38924.44424.49924.55524.610

18.34618.38818.43118.47318.516

14.69514.73314.77114.80914.846

3.7033.7133.7233.7323.742

3.8913.9013.9123.9223.933

0.9840.9880.9930.9971.002

23.8923.9624.0224.0924.15

24.7724.8324.8924.9425.00

262.82263.16263.50263.84264.18

834.8836.6838.4840.2842.0

451452453454455

33.04533.12633.20733.28733.368

24.66524.72124.77624.83224.887

18.55818.60118.64318.68618.728

14.88414.92214.96014.99815.035

3.7523.7623.7713.7813.791

3.9443.9543.9653.9763.986

1.0071.0111.0161.0201.025

24.2124.2824.3424.4124.47

25.0625.1125.1725.2325.28

264.52264.86265.20265.53265.87

843.8845.6847.4849.2851.0

456457458459460

33.44933.52933.61033.69133.772

24.94324.99825.05325.10925.164

18.77118.81318.85618.89818.941

15.07315.11115.14915.18715.225

3.8013.8103.8203.8303.840

3.9974.0084.0184.0294.040

1.0301.0341.0391.0431.048

24.5324.6024.6624.7324.79

25.3425.4025.4625.5125.57

266.21266.55266.89267.22267.56

852.8854.6856.4858.2860.0

461462463464465

33.85233.93334.01434.09534.175

25.22025.27525.33125.38625.442

18.98319.02619.06819.11119.154

15.26215.30015.33815.37615.414

3.8503.8593.8693.8793.889

4.0504.0614.0724.0834.093

1.0531.0571.0621.0671.071

24.8524.9224.9825.0525.11

25.6325.6825.7425.8025.85

267.90268.24268.57268.91269.25

861.8863.6865.4867.2869.0

466467468469470

34.25634.33734.41834.49834.579

25.49725.55325.60825.66425.720

19.19619.23919.28119.32419.366

15.45215.49015.52815.56615.604

3.8983.9083.9183.9283.938

4.1044.1154.1254.1364.147

1.0761.0811.0861.0901.095

25.1825.2425.3125.3725.44

25.9125.9726.0326.0826.14

269.59269.92270.26270.60270.93

870.8872.6874.4876.2878.0

471472473474475

34.66034.74134.82234.90234.983

25.77525.83125.88625.94225.998

19.40919.45119.49419.53719.579

15.64215.68015.71815.75615.794

3.9473.9573.9673.9773.987

4.1584.1684.1794.1904.201

1.1001.1051.1091.1141.119

25.5025.5725.6325.7025.76

26.2026.2526.3126.3726.42

271.27271.61271.94272.28272.61

879.8881.6883.4885.2887.0

476477478479480

35.06435.14535.22635.30735.387

26.05326.10926.16526.22026.276

19.62219.66419.70719.75019.792

15.83215.87015.90815.94615.984

3.9974.0064.0164.0264.036

4.2114.2224.2334.2444.255

1.1241.1291.1331.1381.143

25.8325.8925.9526.0226.09

26.4826.5426.6026.6526.71

272.95273.29273.62273.96274.29

888.8890.6892.4894.2896.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

295

481482483484485

35.46835.54935.63035.71135.792

26.33226.38726.44326.49926.555

19.83519.87719.92019.96220.005

16.02216.06016.09916.13716.175

4.0464.0564.0654.0754.085

4.2654.2764.2874.2984.309

1.1481.1531.1581.1631.167

26.1626.2226.2926.3526.42

26.7726.8226.8826.9426.99

274.63274.96275.30275.63275.97

897.8899.6901.4903.2905.0

486487488489490

35.87335.95436.03436.11536.196

26.61026.66626.72226.77826.834

20.04820.09020.13320.17520.218

16.21316.25116.28916.32716.366

4.0954.1054.1154.1254.134

4.3194.3304.3414.3524.363

1.1721.1771.1821.1871.192

26.4926.5526.6226.6826.75

27.0527.1127.1727.2227.28

276.30276.64276.97277.31277.64

906.8908.6910.4912.2914.0

491492493494495

36.27736.35836.43936.52036.601

26.88926.94527.00127.05727.113

20.26120.30320.34620.38920.431

16.40416.44216.48016.51816.557

4.1444.1544.1644.1744.184

4.3734.3844.3954.4064.417

1.1971.2021.2071.2121.217

26.8226.8826.9527.0127.08

27.3427.3927.4527.5127.56

277.98278.31278.64278.98279.31

915.8917.6919.4921.2923.0

496497498499500

36.68236.76336.84336.92437.005

27.16927.22527.28127.33727.393

20.47420.51620.55920.60220.644

16.59516.63316.67116.71016.748

4.1944.2044.2134.2234.233

4.4284.4394.4494.4604.471

1.2221.2271.2321.2371.242

27.1527.2127.2827.3427.41

27.6227.6827.7427.7927.85

279.64279.98280.31280.64280.98

924.8926.6928.4930.2932.0

501502503504505

37.08637.16737.24837.32937.410

27.44927.50527.56127.61727.673

20.68720.73020.77220.81520.857

16.78616.82416.86316.90116.939

4.2434.2534.2634.2734.283

4.4824.4934.5044.5154.526

1.2471.2521.2571.2621.267

27.4827.5427.6127.6827.74

27.9127.9728.0228.0828.14

281.31281.64281.98282.31282.64

933.8935.6937.4939.2941.0

506507508509510

37.49137.57237.65337.73437.815

27.72927.78527.84127.89727.953

20.90020.94320.98521.02821.071

16.97817.01617.05417.09317.131

4.2934.3034.3134.3234.332

4.5374.5484.5584.5694.580

1.2721.2771.2821.2881.293

27.8127.8827.9528.0128.08

28.2028.2628.3128.3728.43

282.97283.31283.64283.97284.30

942.8944.6946.4948.2950.0

511512513514515

37.89637.97738.05838.13938.220

28.01028.06628.12228.17828.234

21.11321.15621.19921.24121.284

17.16917.20817.24617.28517.323

4.3424.3524.3624.3724.382

4.5914.6024.6134.6244.635

1.2981.3031.3081.3131.318

28.1528.2128.2828.3528.41

28.4928.5528.6028.6628.72

284.63284.97285.30285.63285.96

951.8953.6955.4957.2959.0

516517518519520

38.30038.38138.46238.54338.624

28.29128.34728.40328.46028.516

21.32621.36921.41221.45421.497

17.36117.40017.43817.47717.515

4.3924.4024.4124.4224.432

4.6464.6574.6684.6794.690

1.3241.3291.3341.3391.344

28.4828.5528.6228.6828.75

28.7828.8428.8928.9529.01

286.29286.62286.95287.29287.62

960.8962.6964.4966.2968.0

521522523524525

38.70538.78638.86738.94839.029

28.57228.62928.68528.74128.798

21.54021.58221.62521.66821.710

17.55417.59217.63017.66917.707

4.4424.4524.4624.4724.482

4.7014.7124.7234.7344.745

1.3501.3551.3601.3651.371

28.8228.8928.9529.0229.09

29.0729.1329.1829.2429.30

287.95288.28288.61288.94289.27

969.8971.6973.4975.2977.0

526527528529530

39.11039.19139.27239.35339.434

28.85428.91128.96729.02429.080

21.75321.79621.83821.88121.924

17.74617.78417.82317.86117.900

4.4924.5024.5124.5224.532

4.7564.7674.7784.7894.800

1.3761.3811.3871.3921.397

29.1629.2329.2929.3629.43

29.3629.4229.4729.5329.59

289.60289.93290.26290.59290.92

978.8980.6982.4984.2986.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

296

531532533534535

39.51539.59639.67739.75839.839

29.13729.19429.25029.30729.363

21.96622.00922.05222.09422.137

17.93817.97718.01618.05418.093

4.5424.5524.5624.5724.582

4.8114.8224.8334.8444.855

1.4021.4081.4131.4181.424

29.5029.5729.6329.7029.77

29.6529.7129.7629.8229.88

291.25291.58291.91292.24292.56

987.8989.6991.4993.2995.0

536537538539540

39.92040.00140.08240.16340.243

29.42029.47729.53429.59029.647

22.17922.22222.26522.30722.350

18.13118.17018.20818.24718.286

4.5924.6024.6124.6224.632

4.8664.8774.8884.8994.910

1.4291.4351.4401.4451.451

29.8429.9129.9730.0430.11

29.9430.0030.0530.1130.17

292.89293.22293.55293.88294.21

996.8998.6

1000.41002.21004.0

541542543544545

40.32440.40540.48640.56740.648

29.70429.76129.81829.87429.931

22.39322.43522.47822.52122.563

18.32418.36318.40118.44018.479

4.6424.6524.6624.6724.682

4.9224.9334.9444.9554.966

1.4561.4621.4671.4721.478

30.1830.2530.3230.3930.45

30.2330.2930.3430.4030.46

294.54294.86295.19295.52295.85

1005.81007.61009.41011.21013.0

546547548549550

40.72940.81040.89140.97241.053

29.98830.04530.10230.15930.216

22.60622.64922.69122.73422.776

18.51718.55618.59518.63318.672

4.6924.7024.7124.7224.732

4.9774.9884.9995.0105.021

1.4831.4891.4941.5001.505

30.5230.5930.6630.7330.80

30.5230.5830.6330.6930.75

296.18296.50296.83297.16297.49

1014.81016.61018.41020.21022.0

551552553554555

41.13441.21541.29641.37741.457

30.27330.33030.38730.44430.502

22.81922.86222.90422.94722.990

18.71118.74918.78818.82718.865

4.7424.7524.7624.7724.782

5.0335.0445.0555.0665.077

1.5111.5161.5221.5271.533

30.8730.9431.0131.0831.14

30.8130.8730.9230.9831.04

297.81298.14298.47298.80299.12

1023.81025.61027.41029.21031.0

556557558559560

41.53841.61941.70041.78141.862

30.55930.61630.67330.73030.788

23.03223.07523.11723.16023.203

18.90418.94318.98219.02019.059

4.7934.8034.8134.8234.833

5.0885.0995.1115.1225.133

1.5391.5441.5501.5551.561

31.2131.2831.3531.4231.49

31.1031.1631.2131.2731.33

299.45299.78300.10300.43300.75

1032.81034.61036.41038.21040.0

561562563564565

41.94342.02442.10542.18542.266

30.84530.90230.96031.01731.074

23.24523.28823.33123.37323.416

19.09819.13619.17519.21419.253

4.8434.8534.8634.8734.883

5.1445.1555.1665.1785.189

1.5661.5721.5781.5831.589

31.5631.6331.7031.7731.84

31.3931.4531.5031.5631.62

301.08301.41301.73302.06302.38

1041.81043.61045.41047.21049.0

566567568569570

42.34742.42842.50942.59042.671

31.13231.18931.24731.30431.362

23.45823.50123.54423.58623.629

19.29219.33019.36919.40819.447

4.8934.9044.9144.9244.934

5.2005.2115.2225.2345.245

1.5951.6001.6061.6121.617

31.9131.9832.0532.1232.19

31.6831.7431.7931.8531.91

302.71303.03303.36303.69304.01

1050.81052.61054.41056.21058.0

571572573574575

42.75142.83242.91342.99443.075

31.41931.47731.53531.59231.650

23.67123.71423.75723.79923.842

19.48519.52419.56319.60219.641

4.9444.9544.9644.9744.984

5.2565.2675.2795.2905.301

1.6231.6291.6341.6401.646

32.2632.3332.4032.4732.54

31.9732.0332.0832.1432.20

304.34304.66304.98305.31305.63

1059.81061.61063.41065.21067.0

576577578579580

43.15643.23643.31743.39843.479

31.70831.76631.82331.88131.939

23.88423.92723.97024.01224.055

19.68019.71819.75719.79619.835

4.9955.0055.0155.0255.035

5.3125.3235.3355.3465.357

1.6521.6571.6631.6691.675

32.6132.6832.7532.8232.89

32.2632.3232.3732.4332.49

305.96306.28306.61306.93307.25

1068.81070.61072.41074.21076.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

297

581582583584585

43.56043.64043.72143.80243.883

31.99732.05532.11332.17132.229

24.09724.14024.18224.22524.267

19.87419.91319.95219.99020.029

5.0455.0555.0665.0765.086

5.3695.3805.3915.4025.414

1.6801.6861.6921.6981.704

32.9633.0333.1033.1733.24

32.5532.6132.6632.7232.78

307.58307.90308.23308.55308.87

1077.81079.61081.41083.21085.0

586587588589590

43.96344.04444.12544.20644.286

32.28732.34532.40332.46132.519

24.31024.35324.39524.43824.480

20.06820.10720.14620.18520.224

5.0965.1065.1165.1275.137

5.4255.4365.4485.4595.470

1.7091.7151.7211.7271.733

33.3233.3933.4633.5333.60

32.8432.9032.9633.0233.08

309.20309.52309.84310.16310.49

1086.81088.61090.41092.21094.0

591592593594595

44.36744.44844.52944.60944.690

32.57732.63632.69432.75232.810

24.52324.56524.60824.65024.693

20.26320.30220.34120.37920.418

5.1475.1575.1675.1775.188

5.4815.4935.5045.5155.527

1.7391.7451.7501.7561.762

33.6733.7433.8133.8833.95

33.1433.2033.2633.3233.38

310.81311.13311.45311.78312.10

1095.81097.61099.41101.21103.0

596597598599600

44.77144.85144.93245.01345.093

32.86932.92732.98533.04433.102

24.73524.77824.82024.86324.905

20.45720.49620.53520.57420.613

5.1985.2085.2185.2285.239

5.5385.5495.5615.5725.583

1.7681.7741.7801.7861.792

34.0334.1034.1734.2434.31

33.4333.4933.5533.6133.67

312.42312.74313.06313.39313.71

1104.81106.61108.41110.21112.0

601602603604605

45.17445.25545.33545.41645.497

33.16133.21933.27833.33733.395

24.94824.99025.03325.07525.118

20.65220.69120.73020.76920.808

5.2495.2595.2695.2805.290

5.5955.6065.6185.6295.640

1.7981.8041.8101.8161.822

33.7333.7933.8533.9133.97

314.03314.35314.67314.99315.31

1113.81115.61117.41119.21121.0

606607608609610

45.57745.65845.73845.81945.900

33.45433.51333.57133.63033.689

25.16025.20325.24525.28825.330

20.84720.88620.92520.96421.003

5.3005.3105.3205.3315.341

5.6525.6635.6745.6865.697

1.8281.8341.8401.8461.852

34.0234.0834.1434.2034.26

315.64315.96316.28316.60316.92

1122.81124.61126.41128.21130.0

611612613614615

45.98046.06146.14146.22246.302

33.74833.80733.86633.92533.984

25.37325.41525.45825.50025.543

21.04221.08121.12021.15921.198

5.3515.3615.3725.3825.392

5.7095.7205.7315.7435.754

1.8581.8641.8701.8761.882

34.3234.3834.4434.5034.56

317.24317.56317.88318.20318.52

1131.81133.61135.41137.21139.0

616617618619620

46.38346.46346.54446.62446.705

34.04334.10234.16134.22034.279

25.58525.62725.67025.71225.755

21.23721.27621.31521.35421.393

5.4025.4135.4235.4335.443

5.7665.7775.7895.8005.812

1.8881.8941.9011.9071.913

34.6134.6734.7334.7934.85

318.84319.16319.48319.80320.12

1140.81142.61144.41146.21148.0

621622623624625

46.78546.86646.94647.02747.107

34.33834.39734.45734.51634.575

25.79725.84025.88225.92425.967

21.43221.47121.51021.54921.588

5.4545.4645.4745.4855.495

5.8235.8345.8465.8575.869

1.9191.9251.9311.9371.944

34.9134.9735.0335.0935.15

320.43320.75321.07321.39321.71

1149.81151.61153.41155.21157.0

626627628629630

47.18847.26847.34947.42947.509

34.63534.69434.75434.81334.873

26.00926.05226.09426.13626.179

21.62821.66721.70621.74521.784

5.5055.5155.5265.5365.546

5.8805.8925.9035.9155.926

1.9501.9561.9621.9681.975

35.2035.2635.3235.3835.44

322.03322.35322.67322.98323.30

1158.81160.61162.41164.21166.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

298

631632633634635

47.59047.67047.75147.83147.911

34.93234.99235.05135.11135.171

26.22126.26326.30626.34826.390

21.82321.86221.90121.94021.979

5.5575.5675.5775.5885.598

5.9385.9495.9615.9725.984

1.9811.9871.9931.9992.006

35.5035.5635.6235.6835.74

323.62323.94324.26324.57324.89

1167.81169.61171.41173.21175.0

636637638639640

47.99248.07248.15248.23348.313

35.23035.29035.35035.41035.470

26.43326.47526.51726.56026.602

22.01822.05822.09722.13622.175

5.6085.6185.6295.6395.649

5.9956.0076.0186.0306.041

2.0122.0182.0252.0312.037

35.8035.8635.9235.9836.04

325.21325.53325.84326.16326.48

1176.81178.61180.41182.21184.0

641642643644645

48.39348.47448.55448.63448.715

35.53035.59035.65035.71035.770

26.64426.68726.72926.77126.814

22.21422.25322.29222.33122.370

5.6605.6705.6805.6915.701

6.0536.0656.0766.0886.099

2.0432.0502.0562.0622.069

36.1036.1636.2236.2836.34

326.79327.11327.43327.74328.06

1185.81187.61189.41191.21193.0

646647648649650

48.79548.87548.95549.03549.116

35.83035.89035.95036.01036.071

26.85626.89826.94026.98327.025

22.41022.44922.48822.52722.566

5.7125.7225.7325.7435.753

6.1116.1226.1346.1466.157

2.0752.0822.0882.0942.101

36.4036.4636.5236.5836.64

328.38328.69329.01329.32329.64

1194.81196.61198.41200.21202.0

651652653654655

49.19649.27649.35649.43649.517

36.13136.19136.25236.31236.373

27.06727.10927.15227.19427.236

22.60522.64422.68422.72322.762

5.7635.7745.7845.7945.805

6.1696.1806.1926.2046.215

2.1072.1132.1202.1262.133

36.7036.7636.8236.8836.95

329.96330.27330.59330.90331.22

1203.81205.61207.41209.21211.0

656657658659660

49.59749.67749.75749.83749.917

36.43336.49436.55436.61536.675

27.27827.32027.36327.40527.447

22.80122.84022.87922.91922.958

5.8155.8265.8365.8465.857

6.2276.2386.2506.2626.273

2.1392.1462.1522.1582.165

37.0137.0737.1337.1937.25

331.53331.85332.16332.48332.79

1212.81214.61216.41218.21220.0

661662663664665

49.99750.07750.15750.23850.318

36.73636.79736.85836.91836.979

27.48927.53127.57427.61627.658

22.99723.03623.07523.11523.154

5.8675.8785.8885.8985.909

6.2856.2976.3086.3206.332

2.1712.1782.1842.1912.197

37.3037.3637.4237.4837.55

333.11333.42333.74334.05334.36

1221.81223.61225.41227.21229.0

666667668669670

50.39850.47850.55850.63850.718

37.04037.10137.16237.22337.284

27.70027.74227.78427.82627.869

23.19323.23223.27123.31123.350

5.9195.9305.9405.9505.961

6.3436.3556.3676.3786.390

2.2042.2102.2172.2242.230

37.6137.6737.7337.7937.85

334.68334.99335.31335.62335.93

1230.81232.61234.41236.21238.0

671672673674675

50.79850.87850.95851.03851.118

37.34537.40637.46737.52837.590

27.91127.95327.99528.03728.079

23.38923.42823.46723.50723.546

5.9715.9825.9926.0036.013

6.4026.4136.4256.4376.448

2.2372.2432.2502.2562.263

37.9137.9738.0438.1038.16

336.25336.56336.87337.18337.50

1239.81241.61243.41245.21247.0

676677678679680

51.19751.27751.35751.43751.517

37.65137.71237.77337.83537.896

28.12128.16328.20528.24728.289

23.58523.62423.66323.70323.742

6.0246.0346.0446.0556.065

6.4606.4726.4846.4956.507

2.2702.2762.2832.2892.296

38.2238.2838.3538.4138.47

337.81338.12338.44338.75339.06

1248.81250.61252.41254.21256.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

299

681682683684685

51.59751.67751.75751.83751.916

37.95838.01938.08138.14238.204

28.33228.37428.41628.45828.500

23.78123.82023.86023.89923.938

6.0766.0866.0976.1076.118

6.5196.5316.5426.5546.566

2.3032.3092.3162.3232.329

38.5338.5938.6638.7238.78

339.37339.69340.00340.31340.62

1257.81259.61261.41263.21265.0

686687688689690

51.99652.07652.15652.23652.315

38.26538.32738.38938.45038.512

28.54228.58428.62628.66828.710

23.97724.01624.05624.09524.134

6.1286.1396.1496.1606.170

6.5786.5896.6016.6136.625

2.3362.3432.3502.3562.363

38.8438.9038.9739.0339.09

340.93341.24341.56341.87342.18

1266.81268.61270.41272.21274.0

691692693694695

52.39552.47552.55552.63452.714

38.57438.63638.69838.76038.822

28.75228.79428.83528.87728.919

24.17324.21324.25224.29124.330

6.1816.1916.2026.2126.223

6.6366.6486.6606.6726.684

2.3702.3762.3832.3902.397

39.1539.2239.2839.3439.41

342.49342.80343.11343.42343.73

1275.81277.61279.41281.21283.0

696697698699700

52.79452.87352.95353.03353.112

38.88438.94639.00839.07039.132

28.96129.00329.04529.08729.129

24.37024.40924.44824.48724.527

6.2336.2446.2546.2656.275

6.6956.7076.7196.7316.743

2.4032.4102.4172.4242.431

39.4739.5339.5939.6639.72

344.04344.35344.66344.97345.28

1284.81286.61288.41290.21292.0

701702703704705

53.19253.27253.35153.43153.510

39.19439.25639.31839.38139.443

29.17129.21329.25529.29729.338

24.56624.60524.64424.68424.723

6.2866.2966.3076.3176.328

6.7556.7666.7786.7906.802

2.4372.4442.4512.4582.465

39.7839.8539.9139.9740.04

345.59345.90346.21346.52346.83

1293.81295.61297.41299.21301.0

706707708709710

53.59053.67053.74953.82953.908

39.50539.56839.63039.69339.755

29.38029.42229.46429.50629.548

24.76224.80124.84124.88024.919

6.3386.3496.3606.3706.381

6.8146.8266.8386.8496.861

2.4722.4792.4852.4922.499

40.1040.1640.2240.2940.35

347.14347.45347.76348.07348.38

1302.81304.61306.41308.21310.0

711712713714715

53.98854.06754.14754.22654.306

39.81839.88039.94340.00540.068

29.58929.63129.67329.71529.757

24.95924.99825.03725.07625.116

6.3916.4026.4126.4236.434

6.8736.8856.8976.9096.921

2.5062.5132.5202.5272.534

40.4140.4840.5440.6040.67

348.69348.99349.30349.61349.92

1311.81313.61315.41317.21319.0

716717718719720

54.38554.46554.54454.62454.703

40.13140.19340.25640.31940.382

29.79829.84029.88229.92429.965

25.15525.19425.23325.27325.312

6.4446.4556.4656.4766.486

6.9336.9456.9566.9686.980

2.5412.5482.5552.5622.569

40.7340.8040.8640.9340.98

350.23350.54350.84351.15351.46

1320.81322.61324.41326.21328.0

721722723724725

54.78254.86254.94155.02155.100

40.44540.50840.57040.63340.696

30.00730.04930.09030.13230.174

25.35125.39125.43025.46925.508

6.4976.5086.5186.5296.539

6.9927.0047.0167.0287.040

2.5762.5832.5902.5972.604

41.0441.1141.1741.2341.30

351.77352.08352.38352.69353.00

1329.81331.61333.41335.21337.0

726727728729730

55.17955.25955.33855.41755.497

40.75940.82240.88640.94941.012

30.21630.25730.29930.34130.382

25.54825.58725.62625.66625.705

6.5506.5616.5716.5826.593

7.0527.0647.0767.0887.100

2.6112.6182.6252.6322.639

41.3641.4341.4941.5641.62

353.30353.61353.92354.22354.53

1338.81340.61342.41344.21346.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

300

731732733734735

55.57655.65555.73455.81455.893

41.07541.13841.20141.26541.328

30.42430.46630.50730.54930.590

25.74425.78325.82325.86225.901

6.6036.6146.6246.6356.646

7.1127.1247.1367.1487.160

2.6462.6532.6602.6672.674

41.6941.7541.8241.8841.95

354.84355.14355.45355.76356.06

1347.81349.61351.41353.21355.0

736737738739740

55.97256.05156.13156.21056.289

41.39141.45541.51841.58141.645

30.63230.67430.71530.75730.798

25.94125.98026.01926.05826.098

6.6566.6676.6786.6886.699

7.1727.1847.1967.2087.220

2.6812.6882.6962.7032.710

42.0142.0842.1442.2142.27

356.37356.67356.98357.28357.59

1356.81358.61360.41362.21364.0

741742743744745

56.36856.44756.52656.60656.685

41.70841.77241.83541.89941.962

30.84030.88130.92330.96431.006

26.13726.17626.21626.25526.294

6.7106.7206.7316.7426.752

7.2327.2447.2567.2687.280

2.7172.7242.7312.7382.746

42.3442.4042.4742.5342.60

357.90358.20358.51358.81359.12

1365.81367.61369.41371.21373.0

746747748749750

56.76456.84356.92257.00157.080

42.02642.09042.15342.21742.281

31.04731.08931.13031.17231.213

26.33326.37326.41226.45126.491

6.7636.7746.7846.7956.806

7.2927.3047.3167.3287.340

2.7532.7602.7672.7752.782

42.6642.7342.7942.8642.92

359.42359.72360.03360.33360.64

1374.81376.61378.41380.21382.0

751752753754755

57.15957.23857.31757.39657.475

42.34442.40842.47242.53642.599

31.25531.29631.33831.37931.421

26.53026.56926.60826.64826.687

6.8176.8276.8386.8496.859

7.3527.3647.3767.3897.401

2.7892.7962.8032.8112.818

42.9943.0543.1243.1843.25

360.94361.25361.55361.85362.16

1383.81385.61387.41389.21391.0

756757758759760

57.55457.63357.71257.79157.870

42.66342.72742.79142.85542.919

31.46231.50431.54531.58631.628

26.72626.76626.80526.84426.883

6.8706.8816.8926.9026.913

7.4137.4257.4377.4497.461

2.8252.8332.8402.8472.854

43.3143.3843.4443.5143.57

362.46362.76363.07363.37363.67

1392.81394.61396.41398.21400.0

761762763764765

57.94958.02858.10758.18658.265

42.98343.04743.11143.17543.239

31.66931.71031.75231.79331.834

26.92326.96227.00127.04127.080

6.9246.9346.9456.9566.967

7.4737.4857.4987.5107.522

2.8622.8692.8762.8842.891

43.6443.7043.7743.8343.90

363.98364.28364.58364.89365.19

1401.81403.61405.41407.21409.0

766767768769770

58.34358.42258.50158.58058.659

43.30343.36743.43143.49543.559

31.87631.91731.95832.00032.041

27.11927.15827.19827.23727.276

6.9776.9886.9997.0107.020

7.5347.5467.5587.5707.583

2.8982.9062.9132.9212.928

43.9744.0344.1044.1644.23

365.49365.79366.10366.40366.70

1410.81412.61414.41416.21418.0

771772773774775

58.73858.81658.89558.97459.053

43.62443.68843.75243.81743.881

32.08232.12432.16532.20632.247

27.31627.35527.39427.43327.473

7.0317.0427.0537.0647.074

7.5957.6077.6197.6317.644

2.9352.9432.9502.9582.965

44.3044.3644.4344.4944.56

367.00367.30367.60367.91368.21

1419.81421.61423.41425.21427.0

776777778779780

59.13159.21059.28959.36759.446

43.94544.01044.07444.13944.203

32.28932.33032.37132.41232.453

27.51227.55127.59127.63027.669

7.0857.0967.1077.1177.128

7.6567.6687.6807.6927.705

2.9732.9802.9872.9953.002

44.6344.6944.7644.8244.89

368.51368.81369.11369.41369.71

1428.81430.61432.41434.21436.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

301

781782783784785

59.52559.60459.68259.76159.839

44.26744.33244.39644.46144.525

32.49532.53632.57732.61832.659

27.70827.74827.78727.82627.866

7.1397.1507.1617.1717.182

7.7177.7297.7417.7537.766

3.0103.0173.0253.0323.040

44.9645.0245.0945.1545.22

370.01370.31370.61370.91371.21

1437.81439.61441.41443.21445.0

786787788789790

59.91859.99760.07560.15460.232

44.59044.65544.71944.78444.848

32.70032.74232.78332.82432.865

27.90527.94427.98328.02328.062

7.1937.2047.2157.2267.236

7.7787.7907.8027.8157.827

3.0473.0553.0623.0703.078

45.2945.3545.4245.4845.55

371.51371.81372.11372.41372.71

1446.81448.61450.41452.21454.0

791792793794795

60.31160.39060.46860.54760.625

44.91344.97745.04245.10745.171

32.90632.94732.98833.02933.070

28.10128.14028.18028.21928.258

7.2477.2587.2697.2807.291

7.8397.8527.8647.8767.888

3.0853.0933.1003.1083.116

45.6245.6845.7545.8245.89

373.01373.31373.61373.91374.21

1455.81457.61459.41461.21463.0

796797798799800

60.70460.78260.86060.93961.017

45.23645.30145.36545.43045.494

33.11133.15233.19333.23433.275

28.29728.33728.37628.41528.455

7.3027.3127.3237.3347.345

7.9017.9137.9257.9387.950

3.1233.1313.1383.1463.154

45.9546.0246.0946.1546.22

374.51374.81375.11375.41375.70

1464.81466.61468.41470.21472.0

801802803804805

61.09661.17461.25361.33161.409

45.55945.62445.68845.75345.818

33.31633.35733.39833.43933.480

28.49428.53328.57228.61228.651

7.3567.3677.3787.3887.399

7.9627.9747.9877.9998.011

3.1613.1693.1773.1843.192

46.2946.3546.4246.4946.56

376.00376.30376.60376.90377.19

1473.81475.61477.41479.21481.0

806807808809810

61.48861.56661.64461.72361.801

45.88245.94746.01146.07646.141

33.52133.56233.60333.64433.685

28.69028.72928.76928.80828.847

7.4107.4217.4327.4437.454

8.0248.0368.0488.0618.073

3.2003.2073.2153.2233.230

46.6246.6946.7646.8246.89

377.49377.79378.09378.39378.68

1482.81484.61486.41488.21490.0

811812813814815

61.87961.95862.03662.11462.192

46.20546.27046.33446.39946.464

33.72633.76733.80833.84833.889

28.88628.92628.96529.00429.043

7.4657.4767.4877.4977.508

8.0868.0988.1108.1238.135

3.2383.2463.2543.2613.269

46.9647.0347.0947.1647.23

378.98379.28379.57379.87380.17

1491.81493.61495.41497.21499.0

816817818819820

62.27162.34962.42762.50562.583

46.52846.59346.65746.72246.786

33.93033.97134.01234.05334.093

29.08329.12229.16129.20029.239

7.5197.5307.5417.5527.563

8.1478.1608.1728.1858.197

3.2773.2853.2923.3003.308

47.3047.3747.4347.5047.57

380.46380.76381.06381.35381.65

1500.81502.61504.41506.21508.0

821822823824825

62.66262.74062.81862.89662.974

46.85146.91546.98047.04447.109

34.13434.17534.21634.25734.297

29.27929.31829.35729.39629.436

7.5747.5857.5967.6077.618

8.2098.2228.2348.2478.259

3.3163.3243.3313.3393.347

47.6447.7147.7747.8447.91

381.95382.24382.54382.83383.13

1509.81511.61513.41515.21517.0

826827828829830

63.05263.13063.20863.28663.364

47.17347.23847.30247.36747.431

34.33834.37934.42034.46034.501

29.47529.51429.55329.59229.632

7.6297.6407.6517.6627.673

8.2728.2848.2968.3098.321

3.3553.3633.3713.3793.386

47.9848.0548.1148.1848.25

383.42383.72384.01384.31384.60

1518.81520.61522.41524.21526.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

302

831832833834835

63.44263.52063.59863.67663.754

47.49547.56047.62447.68847.753

34.54234.58234.62334.66434.704

29.67129.71029.74929.78929.828

7.6847.6957.7067.7177.728

8.3348.3468.3598.3718.384

3.3943.4023.4103.4183.426

48.3248.3948.4648.5348.60

384.90385.19385.49385.78386.08

1527.81529.61531.41533.21535.0

836837838839840

63.83263.91063.98864.06664.144

47.81747.88147.94648.01048.074

34.74534.78634.82634.86734.908

29.86729.90629.94529.98530.024

7.7397.7507.7617.7727.783

8.3968.4098.4218.4348.446

3.4343.4423.4503.4583.466

48.6648.7348.8048.8748.94

386.37386.67386.96387.25387.55

1536.81538.61540.41542.21544.0

841842843844845

64.22264.30064.37764.45564.533

48.13848.20248.26748.33148.395

34.94834.98935.02935.07035.110

30.06330.10230.14130.18130.220

7.7947.8057.8167.8277.838

8.4598.4718.4848.4968.509

3.4743.4823.4903.4983.506

49.0149.0849.1549.2249.29

387.84388.14388.43388.72389.02

1545.81547.61549.41551.21553.0

846847848849850

64.61164.68964.76664.84464.922

48.45948.52348.58748.65148.715

35.15135.19235.23235.27335.313

30.25930.29830.33730.37630.416

7.8497.8607.8717.8827.893

8.5218.5348.5468.5598.571

3.5143.5223.5303.5383.546

49.3549.4249.4949.5649.63

389.31389.60389.90390.19390.48

1554.81556.61558.41560.21562.0

851852853854855

65.00065.07765.15565.23365.310

48.77948.84348.90748.97149.034

35.35435.39435.43535.47535.516

30.45530.49430.53330.57230.611

7.9047.9157.9267.9377.948

8.5848.5978.6098.6228.634

3.5543.5623.5703.5783.586

49.7049.7749.8449.9149.98

1563.81565.61567.41569.21571.0

856857858859860

65.38865.46565.54365.62165.698

49.09849.16249.22649.29049.353

35.55635.59635.63735.67735.718

30.65130.69030.72930.76830.807

7.9597.9707.9817.9928.003

8.6478.6598.6728.6858.697

3.5943.6023.6103.6183.626

50.0450.1150.1850.2550.32

1572.81574.61576.41578.21580.0

861862863864865

65.77665.85365.93166.00866.086

49.41749.48149.54449.60849.672

35.75835.79835.83935.87935.920

30.84630.88630.92530.96431.003

8.0148.0268.0378.0488.059

8.7108.7228.7358.7488.760

3.6343.6433.6513.6593.667

50.3950.4650.5350.6050.67

1581.81583.61585.41587.21589.0

866867868869870

66.16366.24166.31866.39666.473

49.73549.79949.86249.92649.989

35.96036.00036.04136.08136.121

31.04231.08131.12031.16031.199

8.0708.0818.0928.1038.114

8.7738.7858.7988.8118.823

3.6753.6833.6923.7003.708

50.7450.8150.8850.9551.02

1590.81592.61594.41596.21598.0

871872873874875

66.55066.62866.70566.78266.860

50.05250.11650.17950.24350.306

36.16236.20236.24236.28236.323

31.23831.27731.31631.35531.394

8.1258.1378.1488.1598.170

8.8368.8498.8618.8748.887

3.7163.7243.7323.7413.749

51.0951.1651.2351.3051.37

1599.81601.61603.41605.21607.0

876877878879880

66.93767.01467.09267.16967.246

50.36950.43250.49550.55950.622

36.36336.40336.44336.48436.524

31.43331.47331.51231.55131.590

8.1818.1928.2038.2148.226

8.8998.9128.9258.9378.950

3.7573.7653.7743.7823.790

51.4451.5151.5851.6551.72

1608.81610.61612.41614.21616.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

303

881882883884885

67.32367.40067.47867.55567.632

50.68550.74850.81150.87450.937

36.56436.60436.64436.68536.725

31.62931.66831.70731.74631.785

8.2378.2488.2598.2708.281

8.9638.9758.9889.0019.014

3.7983.8073.8153.8233.832

51.7951.8651.9352.0052.08

1617.81619.61621.41623.21625.0

886887888889890

67.70967.78667.86367.94068.017

51.00051.06351.12651.18851.251

36.76536.80536.84536.88536.925

31.82431.86331.90331.94231.981

8.2938.3048.3158.3268.337

9.0269.0399.0529.0659.077

3.8403.8483.8573.8653.873

52.1552.2252.2952.3652.43

1626.81628.61630.41632.21634.0

891892893894895

68.09468.17168.24868.32568.402

51.31451.37751.43951.50251.565

36.96537.00637.04637.08637.126

32.02032.05932.09832.13732.176

8.3488.3608.3718.3828.393

9.0909.1039.1159.1289.141

3.8823.8903.8983.9073.915

52.5052.5752.6452.7152.79

1635.81637.61639.41641.21643.0

896897898899900

68.47968.55668.63368.71068.787

51.62751.69051.75251.81551.877

37.16637.20637.24637.28637.326

32.21532.25432.29332.33232.371

8.4048.4168.4278.4388.449

9.1549.1679.1799.1929.205

3.9233.9323.9403.9493.957

52.8652.9353.0053.0753.14

1644.81646.61648.41650.21652.0

901902903904905

68.86368.94069.01769.09469.171

51.94052.00252.06452.12752.189

37.36637.40637.44637.48637.526

32.41032.44932.48832.52732.566

8.4608.4728.4838.4948.505

9.2189.2309.2439.2569.269

3.9653.9743.9823.9913.999

1653.81655.61657.41659.21661.0

906907908909910

69.24769.32469.40169.47769.554

52.25152.31452.37652.43852.500

37.56637.60637.64637.68637.725

32.60532.64432.68332.72232.761

8.5178.5288.5398.5508.562

9.2829.2949.3079.3209.333

4.0084.0164.0244.0334.041

1662.81664.61666.41668.21670.0

911912913914915

69.63169.70769.78469.86069.937

52.56252.62452.68652.74852.810

37.76537.80537.84537.88537.925

32.80032.83932.87832.91732.956

8.5738.5848.5958.6078.618

9.3469.3599.3719.3849.397

4.0504.0584.0674.0754.084

1671.81673.61675.41677.21679.0

916917918919920

70.01370.09070.16670.24370.319

52.87252.93452.99653.05753.119

37.96538.00538.04438.08438.124

32.99533.03433.07333.11233.151

8.6298.6408.6528.6638.674

9.4109.4239.4369.4499.462

4.0934.1014.1104.1184.127

1680.81682.61684.41686.21688.0

921922923924925

70.39670.47270.54870.62570.701

53.18153.24353.30453.36653.427

38.16438.20438.24338.28338.323

33.19033.22933.26833.30733.346

8.6858.6978.7088.7198.731

9.4749.4879.5009.5139.526

4.1354.1444.1524.1614.170

1689.81691.61693.41695.21697.0

926927928929930

70.77770.85470.93071.00671.082

53.48953.55053.61253.67353.735

38.36338.40238.44238.48238.522

33.38533.42433.46333.50233.541

8.7428.7538.7658.7768.787

9.5399.5529.5659.5789.591

4.1784.1874.1954.2044.213

1698.81700.61702.41704.21706.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

304

931932933934935

71.15971.23571.31171.38771.463

53.79653.85753.91953.98054.041

38.56138.60138.64138.68038.720

33.58033.61933.65833.69733.736

8.7988.8108.8218.8328.844

9.6039.6169.6299.6429.655

4.2214.2304.2394.2474.256

1707.81709.61711.41713.21715.0

936937938939940

71.53971.61571.69271.76871.844

54.10254.16454.22554.28654.347

38.76038.79938.83938.87838.918

33.77433.81333.85233.89133.930

8.8558.8668.8788.8898.900

9.6689.6819.6949.7079.720

4.2654.2734.2824.2914.299

1716.81718.61720.41722.21724.0

941942943944945

71.92071.99672.07272.14772.223

54.40854.46954.53054.59154.652

38.95838.99739.03739.07639.116

33.96934.00834.04734.08634.124

8.9128.9238.9358.9468.957

9.7339.7469.7599.7729.785

4.3084.3174.3264.3344.343

1725.81727.61729.41731.21733.0

946947948949950

72.29972.37572.45172.52772.603

54.71354.77354.83454.89554.956

39.15539.19539.23539.27439.314

34.16334.20234.24134.28034.319

8.9698.9808.9919.0039.014

9.7989.8119.8249.8379.850

4.3524.3604.3694.3784.387

1734.81736.61738.41740.21742.0

951952953954955

72.67872.75472.83072.90672.981

55.01655.07755.13855.19855.259

39.35339.39339.43239.47139.511

34.35834.39634.43534.47434.513

9.0259.0379.0489.0609.071

9.8639.8769.8899.9029.915

4.3964.4044.4134.4224.431

1743.81745.61747.41749.21751.0

956957958959960

73.05773.13373.20873.28473.360

55.31955.38055.44055.50155.561

39.55039.59039.62939.66939.708

34.55234.59134.62934.66834.707

9.0829.0949.1059.1179.128

9.9289.9419.9549.9679.980

4.4404.4484.4574.4664.475

1752.81754.61756.41758.21760.0

961962963964965

73.43573.51173.58673.66273.738

55.62255.68255.74255.80355.863

39.74739.78739.82639.86639.905

34.74634.78534.82334.86234.901

9.1399.1519.1629.1749.185

9.99310.00610.01910.03210.046

4.4844.4934.5014.5104.519

1761.81763.61765.41767.21769.0

966967968969970

73.81373.88973.96474.04074.115

55.92355.98356.04356.10456.164

39.94439.98440.02340.06240.101

34.94034.97935.01735.05635.095

9.1979.2089.2199.2319.242

10.05910.07210.08510.09810.111

4.5284.5374.5464.5554.564

1770.81772.61774.41776.21778.0

971972973974975

74.19074.26674.34174.41774.492

56.22456.28456.34456.40456.464

40.14140.18040.21940.25940.298

35.13435.17235.21135.25035.289

9.2549.2659.2779.2889.300

10.12410.13710.15010.16310.177

4.5734.5824.5914.5994.608

1779.81781.61783.41785.21787.0

976977978979980

74.56774.64374.71874.79374.869

56.52456.58456.64356.70356.763

40.33740.37640.41540.45540.494

35.32735.36635.40535.44435.482

9.3119.3239.3349.3459.357

10.19010.20310.21610.22910.242

4.6174.6264.6354.6444.653

1788.81790.61792.41794.21796.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

305

981982983984985

74.94475.01975.09575.17075.245

56.82356.88356.94257.00257.062

40.53340.57240.61140.65140.690

35.52135.56035.59835.63735.676

9.3689.3809.3919.4039.414

10.25510.26910.28210.29510.308

4.6624.6714.6804.6894.698

1797.81799.61801.41803.21805.0

986987988989990

75.32075.39575.47175.54675.621

57.12157.18157.24057.30057.360

40.72940.76840.80740.84640.885

35.71435.75335.79235.83135.869

9.4269.4379.4499.4609.472

10.32110.33410.34810.36110.374

4.7074.7164.7254.7344.743

1806.81808.61810.41812.21814.0

991992993994995

75.69675.77175.84775.92275.997

57.41957.47957.53857.59757.657

40.92440.96341.00241.04241.081

35.90835.94635.98536.02436.062

9.4839.4959.5069.5189.529

10.38710.40010.41310.42710.440

4.7534.7624.7714.7804.789

1815.81817.61819.41821.21823.0

996997998999

1000

76.07276.14776.22376.29876.373

57.71657.77657.83557.89457.953

41.12041.15941.19841.23741.276

36.10136.14036.17836.21736.256

9.5419.5529.5649.5769.587

10.45310.46610.48010.49310.506

4.7984.8074.8164.8254.834

1824.81826.61828.41830.21832.0

10011002100310041005

58.01358.07258.13158.19058.249

41.31541.35441.39341.43141.470

36.29436.33336.37136.41036.449

9.5999.6109.6229.6339.645

10.51910.53210.54610.55910.572

4.8434.8534.8624.8714.880

1833.81835.61837.41839.21841.0

10061007100810091010

58.30958.36858.42758.48658.545

41.50941.54841.58741.62641.665

36.48736.52636.56436.60336.641

9.6569.6689.6799.6919.703

10.58510.59910.61210.62510.639

4.8894.8984.9084.9174.926

1842.81844.61846.41848.21850.0

10111012101310141015

58.60458.66358.72258.78158.840

41.70441.74341.78141.82041.859

36.68036.71836.75736.79636.834

9.7149.7269.7379.7499.761

10.65210.66510.67810.69210.705

4.9354.9444.9544.9634.972

1851.81853.61855.41857.21859.0

10161017101810191020

58.89958.95759.01659.07559.134

41.89841.93741.97642.01442.053

36.87336.91136.95036.98837.027

9.7729.7849.7959.8079.818

10.71810.73210.74510.75810.771

4.9814.9905.0005.0095.018

1860.81862.61864.41866.21868.0

10211022102310241025

59.19359.25259.31059.36959.428

42.09242.13142.16942.20842.247

37.06537.10437.14237.18137.219

9.8309.8429.8539.8659.877

10.78510.79810.81110.82510.838

5.0275.0375.0465.0555.065

1869.81871.61873.41875.21877.0

10261027102810291030

59.48759.54559.60459.66359.721

42.28642.32442.36342.40242.440

37.25837.29637.33437.37337.411

9.8889.9009.9119.9239.935

10.85110.86510.87810.89110.905

5.0745.0835.0925.1025.111

1878.81880.61882.41884.21886.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

306

10311032103310341035

59.78059.83859.89759.95660.014

42.47942.51842.55642.59542.633

37.45037.48837.52737.56537.603

9.9469.9589.9709.9819.993

10.91810.93210.94510.95810.972

5.1205.1305.1395.1485.158

1887.81889.61891.41893.21895.0

10361037103810391040

60.07360.13160.19060.24860.307

42.67242.71142.74942.78842.826

37.64237.68037.71937.75737.795

10.00510.01610.02810.04010.051

10.98510.99811.01211.02511.039

5.1675.1765.1865.1955.205

1896.81898.61900.41902.21904.0

10411042104310441045

60.36560.42360.48260.54060.599

42.86542.90342.94242.98043.019

37.83437.87237.91137.94937.987

10.06310.07510.08610.09810.110

11.05211.06511.07911.09211.106

5.2145.2235.2335.2425.252

1905.81907.61909.41911.21913.0

10461047104810491050

60.65760.71560.77460.83260.890

43.05743.09643.13443.17343.211

38.02638.06438.10238.14138.179

10.12110.13310.14510.15610.168

11.11911.13311.14611.15911.173

5.2615.2705.2805.2895.299

1914.81916.61918.41920.21922.0

10511052105310541055

60.94961.00761.06561.12361.182

43.25043.28843.32743.36543.403

38.21738.25638.29438.33238.370

10.18010.19110.20310.21510.227

11.18611.20011.21311.22711.240

5.3085.3185.3275.3375.346

1923.81925.61927.41929.21931.0

10561057105810591060

61.24061.29861.35661.41561.473

43.44243.48043.51843.55743.595

38.40938.44738.48538.52438.562

10.23810.25010.26210.27310.285

11.25411.26711.28011.29411.307

5.3565.3655.3755.3845.394

1932.81934.61936.41938.21940.0

10611062106310641065

61.53161.58961.64761.70561.763

43.63343.67243.71043.74843.787

38.60038.63838.67738.71538.753

10.29710.30910.32010.33210.344

11.32111.33411.34811.36111.375

5.4035.4135.4225.4325.441

1941.81943.61945.41947.21949.0

10661067106810691070

61.82261.88061.93861.99662.054

43.82543.86343.90143.94043.978

38.79138.82938.86838.90638.944

10.35610.36710.37910.39110.403

11.38811.40211.41511.42911.442

5.4515.4605.4705.4805.489

1950.81952.61954.41956.21958.0

10711072107310741075

62.11262.17062.22862.28662.344

44.01644.05444.09244.13044.169

38.98239.02039.05939.09739.135

10.41410.42610.43810.45010.461

11.45611.46911.48311.49611.510

5.4995.5085.5185.5285.537

1959.81961.61963.41965.21967.0

10761077107810791080

62.40262.46062.51862.57662.634

44.20744.24544.28344.32144.359

39.17339.21139.24939.28739.326

10.47310.48510.49710.50910.520

11.52411.53711.55111.56411.578

5.5475.5565.5665.5765.585

1968.81970.61972.41974.21976.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

307

10811082108310841085

62.69262.75062.80862.86662.924

44.39744.43544.47344.51244.550

39.36439.40239.44039.47839.516

10.53210.54410.55610.56710.579

11.59111.60511.61811.63211.646

5.5955.6055.6145.6245.634

1977.81979.61981.41983.21985.0

10861087108810891090

62.98263.04063.09863.15663.214

44.58844.62644.66444.70244.740

39.55439.59239.63039.66839.706

10.59110.60310.61510.62610.638

11.65911.67311.68611.70011.714

5.6435.6535.6635.6725.682

1986.81988.61990.41992.21994.0

10911092109310941095

63.27163.32963.38763.44563.503

44.77844.81644.85344.89144.929

39.74439.78339.82139.85939.897

10.65010.66210.67410.68610.697

11.72711.74111.75411.76811.782

5.6925.7025.7115.7215.731

1995.81997.61999.42001.22003.0

10961097109810991100

63.56163.61963.67763.73463.792

44.96745.00545.04345.08145.119

39.93539.97340.01140.04940.087

10.70910.72110.73310.74510.757

11.79511.80911.82211.83611.850

5.7405.7505.7605.7705.780

2004.82006.62008.42010.22012.0

11011102110311041105

63.85063.90863.96664.02464.081

45.15745.19445.23245.27045.308

40.12540.16340.20140.23840.276

10.76810.78010.79210.80410.816

11.86311.87711.89111.90411.918

5.7895.7995.8095.8195.828

2013.82015.62017.42019.22021.0

11061107110811091110

64.13964.19764.25564.31364.370

45.34645.38345.42145.45945.497

40.31440.35240.39040.42840.466

10.82810.83910.85110.86310.875

11.93111.94511.95911.97211.986

5.8385.8485.8585.8685.878

2022.82024.62026.42028.22030.0

11111112111311141115

64.42864.48664.54464.60264.659

45.53445.57245.61045.64745.685

40.50440.54240.58040.61840.655

10.88710.89910.91110.92210.934

12.00012.01312.02712.04112.054

5.8875.8975.9075.9175.927

2031.82033.62035.42037.22039.0

11161117111811191120

64.71764.77564.83364.89064.948

45.72345.76045.79845.83645.873

40.69340.73140.76940.80740.845

10.94610.95810.97010.98210.994

12.06812.08212.09612.10912.123

5.9375.9475.9565.9665.976

2040.82042.62044.42046.22048.0

11211122112311241125

65.00665.06465.12165.17965.237

45.91145.94845.98646.02446.061

40.88340.92040.95840.99641.034

11.00611.01711.02911.04111.053

12.13712.15012.16412.17812.191

5.9865.9966.0066.0166.026

2049.82051.62053.42055.22057.0

11261127112811291130

65.29565.35265.41065.46865.525

46.09946.13646.17446.21146.249

41.07241.10941.14741.18541.223

11.06511.07711.08911.10111.113

12.20512.21912.23312.24612.260

6.0366.0466.0556.0656.075

2058.82060.62062.42064.22066.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

308

11311132113311341135

65.58365.64165.69965.75665.814

46.28646.32446.36146.39846.436

41.26041.29841.33641.37441.411

11.12511.13611.14811.16011.172

12.27412.28812.30112.31512.329

6.0856.0956.1056.1156.125

2067.82069.62071.42073.22075.0

11361137113811391140

65.87265.92965.98766.04566.102

46.47346.51146.54846.58546.623

41.44941.48741.52541.56241.600

11.18411.19611.20811.22011.232

12.34212.35612.37012.38412.397

6.1356.1456.1556.1656.175

2076.82078.62080.42082.22084.0

11411142114311441145

66.16066.21866.27566.33366.391

46.66046.69746.73546.77246.809

41.63841.67541.71341.75141.788

11.24411.25611.26811.28011.291

12.41112.42512.43912.45312.466

6.1856.1956.2056.2156.225

2085.82087.62089.42091.22093.0

11461147114811491150

66.44866.50666.56466.62166.679

46.84746.88446.92146.95846.995

41.82641.86441.90141.93941.976

11.30311.31511.32711.33911.351

12.48012.49412.50812.52112.535

6.2356.2456.2566.2666.276

2094.82096.62098.42100.22102.0

11511152115311541155

66.73766.79466.85266.91066.967

47.03347.07047.10747.14447.181

42.01442.05242.08942.12742.164

11.36311.37511.38711.39911.411

12.54912.56312.57712.59012.604

6.2866.2966.3066.3166.326

2103.82105.62107.42109.22111.0

11561157115811591160

67.02567.08267.14067.19867.255

47.21847.25647.29347.33047.367

42.20242.23942.27742.31442.352

11.42311.43511.44711.45911.471

12.61812.63212.64612.65912.673

6.3366.3466.3566.3676.377

2112.82114.62116.42118.22120.0

11611162116311641165

67.31367.37067.42867.48667.543

47.40447.44147.47847.51547.552

42.39042.42742.46542.50242.540

11.48311.49511.50711.51911.531

12.68712.70112.71512.72912.742

6.3876.3976.4076.4176.427

2121.82123.62125.42127.22129.0

11661167116811691170

67.60167.65867.71667.77367.831

47.58947.62647.66347.70047.737

42.57742.61442.65242.68942.727

11.54211.55411.56611.57811.590

12.75612.77012.78412.79812.812

6.4386.4486.4586.4686.478

2130.82132.62134.42136.22138.0

11711172117311741175

67.88867.94668.00368.06168.119

47.77447.81147.84847.88447.921

42.76442.80242.83942.87742.914

11.60211.61411.62611.63811.650

12.82512.83912.85312.86712.881

6.4886.4996.5096.5196.529

2139.82141.62143.42145.22147.0

11761177117811791180

68.17668.23468.29168.34868.406

47.95847.99548.03248.06948.105

42.95142.98943.02643.06443.101

11.66211.67411.68611.69811.710

12.89512.90912.92212.93612.950

6.5396.5506.5606.5706.580

2148.82150.62152.42154.22156.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

309

11811182118311841185

68.46368.52168.57868.63668.693

48.14248.17948.21648.25248.289

43.13843.17643.21343.25043.288

11.72211.73411.74611.75811.770

12.96412.97812.99213.00613.019

6.5916.6016.6116.6216.632

2157.82159.62161.42163.22165.0

11861187118811891190

68.75168.80868.86568.92368.980

48.32648.36348.39948.43648.473

43.32543.36243.39943.43743.474

11.78211.79411.80611.81811.830

13.03313.04713.06113.07513.089

6.6426.6526.6636.6736.683

2166.82168.62170.42172.22174.0

11911192119311941195

69.03769.09569.15269.20969.267

48.50948.54648.58248.61948.656

43.51143.54943.58643.62343.660

11.84211.85411.86611.87811.890

13.10313.11713.13113.14513.158

6.6936.7046.7146.7246.735

2175.82177.62179.42181.22183.0

11961197119811991200

69.32469.38169.43969.49669.553

48.69248.72948.76548.80248.838

43.69843.73543.77243.80943.846

11.90211.91411.92611.93911.951

13.17213.18613.20013.21413.228

6.7456.7556.7666.7766.786

2184.82186.62188.42190.22192.0

12011202120312041205

48.87548.91148.94848.98449.021

43.88443.92143.95843.99544.032

11.96311.97511.98711.99912.011

13.24213.25613.27013.28413.298

6.7976.8076.8186.8286.838

2193.82195.62197.42199.22201.0

12061207120812091210

49.05749.09349.13049.16649.202

44.06944.10644.14444.18144.218

12.02312.03512.04712.05912.071

13.31113.32513.33913.35313.367

6.8496.8596.8696.8806.890

2202.82204.62206.42208.22210.0

12111212121312141215

49.23949.27549.31149.34849.384

44.25544.29244.32944.36644.403

12.08312.09512.10712.11912.131

13.38113.39513.40913.42313.437

6.9016.9116.9226.9326.942

2211.82213.62215.42217.22219.0

12161217121812191220

49.42049.45649.49349.52949.565

44.44044.47744.51444.55144.588

12.14312.15512.16712.17912.191

13.45113.46513.47913.49313.507

6.9536.9636.9746.9846.995

2220.82222.62224.42226.22228.0

12211222122312241225

49.60149.63749.67449.71049.746

44.62544.66244.69944.73644.773

12.20312.21612.22812.24012.252

13.52113.53513.54913.56313.577

7.0057.0167.0267.0377.047

2229.82231.62233.42235.22237.0

12261227122812291230

49.78249.81849.85449.89049.926

44.81044.84744.88444.92144.958

12.26412.27612.28812.30012.312

13.59013.60413.61813.63213.646

7.0587.0687.0797.0897.100

2238.82240.62242.42244.22246.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

310

12311232123312341235

49.96249.99850.03450.07050.106

44.99545.03245.06945.10545.142

12.32412.33612.34812.36012.372

13.66013.67413.68813.70213.716

7.1107.1217.1317.1427.152

2247.82249.62251.42253.22255.0

12361237123812391240

50.14250.17850.21450.25050.286

45.17945.21645.25345.29045.326

12.38412.39712.40912.42112.433

13.73013.74413.75813.77213.786

7.1637.1737.1847.1947.205

2256.82258.62260.42262.22264.0

12411242124312441245

50.32250.35850.39350.42950.465

45.36345.40045.43745.47445.510

12.44512.45712.46912.48112.493

13.80013.81413.82813.84213.856

7.2167.2267.2377.2477.258

2265.82267.62269.42271.22273.0

12461247124812491250

50.50150.53750.57250.60850.644

45.54745.58445.62145.65745.694

12.50512.51712.52912.54212.554

13.87013.88413.89813.91213.926

7.2697.2797.2907.3007.311

2274.82276.62278.42280.22282.0

12511252125312541255

50.68050.71550.75150.78750.822

45.73145.76745.80445.84145.877

12.56612.57812.59012.60212.614

13.94013.95413.96813.98213.996

7.3227.3327.3437.3537.364

2283.82285.62287.42289.22291.0

12561257125812591260

50.85850.89450.92950.96551.000

45.91445.95145.98746.02446.060

12.62612.63812.65012.66212.675

14.01014.02414.03814.05214.066

7.3757.3857.3967.4077.417

2292.82294.62296.42298.22300.0

12611262126312641265

51.03651.07151.10751.14251.178

46.09746.13346.17046.20746.243

12.68712.69912.71112.72312.735

14.08114.09514.10914.12314.137

7.4287.4397.4497.4607.471

2301.82303.62305.42307.22309.0

12661267126812691270

51.21351.24951.28451.32051.355

46.28046.31646.35346.38946.425

12.74712.75912.77112.78312.796

14.15114.16514.17914.19314.207

7.4827.4927.5037.5147.524

2310.82312.62314.42316.22318.0

12711272127312741275

51.39151.42651.46151.49751.532

46.46246.49846.53546.57146.608

12.80812.82012.83212.84412.856

14.22114.23514.24914.26314.277

7.5357.5467.5577.5677.578

2319.82321.62323.42325.22327.0

12761277127812791280

51.56751.60351.63851.67351.708

46.64446.68046.71746.75346.789

12.86812.88012.89212.90512.917

14.29114.30514.31914.33314.347

7.5897.6007.6107.6217.632

2328.82330.62332.42334.22336.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

311

12811282128312841285

51.74451.77951.81451.84951.885

46.82646.86246.89846.93546.971

12.92912.94112.95312.96512.977

14.36114.37514.39014.40414.418

7.6437.6537.6647.6757.686

2337.82339.62341.42343.22345.0

12861287128812891290

51.92051.95551.99052.02552.060

47.00747.04347.07947.11647.152

12.98913.00113.01413.02613.038

14.43214.44614.46014.47414.488

7.6977.7077.7187.7297.740

2346.82348.62350.42352.22354.0

12911292129312941295

52.09552.13052.16552.20052.235

47.18847.22447.26047.29647.333

13.05013.06213.07413.08613.098

14.50214.51614.53014.54414.558

7.7517.7617.7727.7837.794

2355.82357.62359.42361.22363.0

12961297129812991300

52.27052.30552.34052.37552.410

47.36947.40547.44147.47747.513

13.11113.12313.13513.14713.159

14.57214.58614.60114.61514.629

7.8057.8167.8277.8377.848

2364.82366.62368.42370.22372.0

13011302130313041305

52.44552.48052.51552.55052.585

13.17113.18313.19513.20813.220

14.64314.65714.67114.68514.699

7.8597.8707.8817.8927.903

2373.82375.62377.42379.22381.0

13061397130813091310

52.62052.65452.68952.72452.759

13.23213.24413.25613.26813.280

14.71314.72714.74114.75514.770

7.9147.9247.9357.9467.957

2382.82384.62386.42388.22390.0

13111312131313141315

52.79452.82852.86352.89852.932

13.29213.30513.31713.32913.341

14.78414.79814.81214.82614.840

7.9687.9797.9908.0018.012

2391.82393.62395.42397.22399.0

13161317131813191320

52.96753.00253.03753.07153.106

13.35313.36513.37713.39013.402

14.85414.86814.88214.89614.911

8.0238.0348.0458.0568.066

2400.82402.62404.42406.22408.0

13211322132313241325

53.14053.17553.21053.24453.279

13.41413.42613.43813.45013.462

14.92514.93914.95314.96714.981

8.0778.0888.0998.1108.121

2409.82411.62413.42415.22417.0

13261327132813291330

53.31353.34853.38253.41753.451

13.47413.48713.49913.51113.523

14.99515.00915.02315.03715.052

8.1328.1438.1548.1658.176

2418.82420.62422.42424.22426.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

312

13311332133313341335

53.48653.52053.55553.58953.623

13.53513.54713.55913.57213.584

15.06615.08015.09415.10815.122

8.1878.1988.2098.2208.231

2427.82429.62431.42433.22435.0

13361337133813391340

53.65853.69253.72753.76153.795

13.59613.60813.62013.63213.644

15.13615.15015.16415.17915.193

8.2428.2538.2648.2758.286

2436.82438.62440.42442.22444.0

13411342134313441345

53.83053.86453.89853.93253.967

13.65713.66913.68113.69313.705

15.20715.22115.23515.24915.263

8.2988.3098.3208.3318.342

2445.82447.62449.42451.22453.0

13461347134813491350

54.00154.03554.06954.10454.138

13.71713.72913.74213.75413.766

15.27715.29115.30615.32015.334

8.3538.3648.3758.3868.397

2454.82456.62458.42460.22462.0

13511352135313541355

54.17254.20654.24054.27454.308

13.77813.79013.80213.81413.826

15.34815.36215.37615.39015.404

8.4088.4198.4308.4418.453

2463.82465.62467.42469.22471.0

13561357135813591360

54.34354.37754.41154.44554.479

13.83913.85113.86313.87513.887

15.41915.43315.44715.46115.475

8.4648.4758.4868.4978.508

2472.82474.62476.42478.22480.0

13611362136313641365

54.51354.54754.58154.61554.649

13.89913.91113.92413.93613.948

15.48915.50315.51715.53115.546

8.5198.5308.5428.5538.564

2481.82483.62485.42487.22489.0

13661367136813691370

54.68354.71754.75154.78554.819

13.96013.97213.98413.99614.009

15.56015.57415.58815.60215.616

8.5758.5868.5978.6088.620

2490.82492.62494.42496.22498.0

13711372137313741375

54.85254.886

14.02114.03314.04514.05714.069

15.63015.64515.65915.67315.687

8.6318.6428.6538.6648.675

2499.82501.62503.42505.22507.0

13761377137813791380

14.08114.09414.10614.11814.130

15.70115.71515.72915.74315.758

8.6878.6988.7098.7208.731

2508.82510.62512.42514.22516.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

313

13811382138313841385

14.14214.15414.16614.17814.191

15.77215.78615.80015.81415.828

8.7438.7548.7658.7768.787

2517.82519.62521.42523.22525.0

13861387138813891390

14.20314.21514.22714.23914.251

15.84215.85615.87115.88515.899

8.7998.8108.8218.8328.844

2526.82528.62530.42532.22534.0

13911392139313941395

14.26314.27614.28814.30014.312

15.91315.92715.94115.95515.969

8.8558.8668.8778.8898.900

2535.82537.62539.42541.22543.0

13961397139813991400

14.32414.33614.34814.36014.373

15.98415.99816.01216.02616.040

8.9118.9228.9348.9458.956

2544.82546.62548.42550.22552.0

14011402140314041405

14.38514.39714.40914.42114.433

16.05416.06816.08216.09716.111

8.9678.9798.9909.0019.013

2553.82555.62557.42559.22561.0

14061407140814091410

14.44514.45714.47014.48214.494

16.12516.13916.15316.16716.181

9.0249.0359.0479.0589.069

2562.82564.62566.42568.22570.0

14111412141314141415

14.50614.51814.53014.54214.554

16.19616.21016.22416.23816.252

9.0809.0929.1039.1149.126

2571.82573.62575.42577.22579.0

14161417141814191420

14.56714.57914.59114.60314.615

16.26616.28016.29416.30916.323

9.1379.1489.1609.1719.182

2580.82582.62584.42586.22588.0

14211422142314241425

14.62714.63914.65114.66414.676

16.33716.35116.36516.37916.393

9.1949.2059.2169.2289.239

2589.82591.62593.42595.22597.0

14261427142814291430

14.68814.70014.71214.72414.736

16.40716.42216.43616.45016.464

9.2519.2629.2739.2859.296

2598.82600.62602.42604.22606.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

314

14311432143314341435

14.74814.76014.77314.78514.797

16.47816.49216.50616.52016.534

9.3079.3199.3309.3429.353

2607.82609.62611.42613.22615.0

14361437143814391440

14.80914.82114.83314.84514.857

16.54916.56316.57716.59116.605

9.3649.3769.3879.3989.410

2616.82618.62620.42622.22624.0

14411442144314441445

14.86914.88114.89414.90614.918

16.61916.63316.64716.66216.676

9.4219.4339.4449.4569.467

2625.82627.62629.42631.22633.0

14461447144814491450

14.93014.94214.95414.96614.978

16.69016.70416.71816.73216.746

9.4789.4909.5019.5139.524

2634.82636.62638.42640.22642.0

14511452145314541455

14.99015.00215.01515.02715.039

16.76016.77416.78916.80316.817

9.5369.5479.5589.5709.581

2643.82645.62647.42649.22651.0

14561457145814591460

15.05115.06315.07515.08715.099

16.83116.84516.85916.87316.887

9.5939.6049.6169.6279.639

2652.82654.62656.42658.22660.0

14611462146314641465

15.11115.12315.13515.14815.160

16.90116.91516.93016.94416.958

9.6509.6629.6739.6849.696

2661.82663.62665.42667.22669.0

14661467146814691470

15.17215.18415.19615.20815.220

16.97216.98617.00017.01417.028

9.7079.7199.7309.7429.753

2670.82672.62674.42676.22678.0

14711472147314741475

15.23215.24415.25615.26815.280

17.04217.05617.07117.08517.099

9.7659.7769.7889.7999.811

2679.82681.62683.42685.22687.0

14761477147814791480

15.29215.30415.31715.32915.341

17.11317.12717.14117.15517.169

9.8229.8349.8459.8579.868

2688.82690.62692.42694.22696.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

315

14811482148314841485

15.35315.36515.37715.38915.401

17.18317.19717.21117.22517.240

9.8809.8919.9039.9149.926

2697.82699.62701.42703.22705.0

14861487148814891490

15.41315.42515.43715.44915.461

17.25417.26817.28217.29617.310

9.9379.9499.9619.9729.984

2706.82708.62710.42712.22714.0

14911492149314941495

15.47315.48515.49715.50915.521

17.32417.33817.35217.36617.380

9.99510.00710.01810.03010.041

2715.82717.62719.42721.22723.0

14961497149814991500

15.53415.54615.55815.57015.582

17.39417.40817.42317.43717.451

10.05310.06410.07610.08810.099

2724.82726.62728.42730.22732.0

15011502150315041505

15.59415.60615.61815.63015.642

17.46517.47917.49317.50717.521

10.11110.12210.13410.14510.157

2733.82735.62737.42739.22741.0

15061507150815091510

15.65415.66615.67815.69015.702

17.53517.54917.56317.57717.591

10.16810.18010.19210.20310.215

2742.82744.62746.42748.22750.0

15111512151315141515

15.71415.72615.73815.75015.762

17.60517.61917.63317.64717.661

10.22610.23810.24910.26110.273

2751.82753.62755.42757.22759.0

15161517151815191520

15.77415.78615.79815.81015.822

17.67617.69017.70417.71817.732

10.28410.29610.30710.31910.331

2760.82762.62764.42766.22768.0

15211522152315241525

15.83415.84615.85815.87015.882

17.74617.76017.77417.78817.802

10.34210.35410.36510.37710.389

2769.82771.62773.42775.22777.0

15261527152815291530

15.89415.90615.91815.93015.942

17.81617.83017.84417.85817.872

10.40010.41210.42310.43510.447

2778.82780.62782.42784.22786.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

316

15311532153315341535

15.95415.96615.97815.99016.002

17.88617.90017.91417.92817.942

10.45810.47010.48210.49310.505

2787.82789.62791.42793.22795.0

15361537153815391540

16.01416.02616.03816.05016.062

17.95617.97017.98417.99818.012

10.51610.52810.54010.55110.563

2796.82798.62800.42802.22804.0

15411542154315441545

16.07416.08616.09816.11016.122

18.02618.04018.05418.06818.082

10.57510.58610.59810.60910.621

2805.82807.62809.42811.22813.0

15461547154815491550

16.13416.14616.15816.17016.182

18.09618.11018.12418.13818.152

10.63310.64410.65610.66810.679

2814.82816.62818.42820.22822.0

15511552155315541555

16.19416.20516.21716.22916.241

18.16618.18018.19418.20818.222

10.69110.70310.71410.72610.738

2823.82825.62827.42829.22831.0

15561557155815591560

16.25316.26516.27716.28916.301

18.23618.25018.26418.27818.292

10.74910.76110.77310.78410.796

2832.82834.62836.42838.22840.0

15611562156315641565

16.31316.32516.33716.34916.361

18.30618.32018.33418.34818.362

10.80810.81910.83110.84310.854

2841.82843.62845.42847.22849.0

15661567156815691570

16.37316.38516.39616.40816.420

18.37618.39018.40418.41718.431

10.86610.87710.88910.90110.913

2850.82852.62854.42856.22858.0

15711572157315741575

16.43216.44416.45616.46816.480

18.44518.45918.47318.48718.501

10.92410.93610.94810.95910.971

2859.82861.62863.42865.22867.0

15761577157815791580

16.49216.50416.51616.52716.539

18.51518.52918.54318.55718.571

10.98310.99411.00611.01811.029

2868.82870.62872.42874.22876.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

317

15811582158315841585

16.55116.56316.57516.58716.599

18.58518.59918.61318.62718.640

11.04111.05311.06411.07611.088

2877.82879.62881.42883.22885.0

15861587158815891590

16.61116.62316.63416.64616.658

18.65418.66818.68218.69618.710

11.09911.11111.12311.13411.146

2886.82888.62890.42892.22894.0

15911592159315941595

16.67016.68216.69416.70616.718

18.72418.73818.75218.76618.779

11.15811.16911.18111.19311.205

2895.82897.62899.42901.22903.0

15961597159815991600

16.72916.74116.75316.76516.777

18.79318.80718.82118.83518.849

11.21611.22811.24011.25111.263

2904.82906.62908.42910.22912.0

16011602160316041605

16.78916.80116.81216.82416.836

18.86318.87718.89118.90418.918

11.27511.28611.29811.31011.321

2913.82915.62917.42919.22921.0

16061607160816091610

16.84816.86016.87216.88316.895

18.93218.94618.96018.97418.988

11.33311.34511.35711.36811.380

2922.82924.62926.42928.22930.0

16111612161316141615

16.90716.91916.93116.94316.954

19.00219.01519.02919.04319.057

11.39211.40311.41511.42711.438

2931.82933.62935.42937.22939.0

16161617161816191620

16.96616.97816.99017.00217.013

19.07119.08519.09819.11219.126

11.45011.46211.47411.48511.497

2940.82942.62944.42946.22948.0

16211622162316241625

17.02517.03717.04917.06117.072

19.14019.15419.16819.18119.195

11.50911.52011.53211.54411.555

2949.82951.62953.42955.22957.0

16261627162816291630

17.08417.09617.10817.12017.131

19.20919.22319.23719.25019.264

11.56711.57911.59111.60211.614

2958.82960.62962.42964.22966.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

318

16311632163316341635

17.14317.15517.16717.17817.190

19.27819.29219.30619.31919.333

11.62611.63711.64911.66111.673

2967.82969.62971.42973.22975.0

16361637163816391640

17.20217.21417.22517.23717.249

19.34719.36119.37519.38819.402

11.68411.69611.70811.71911.731

2976.82978.62980.42982.22984.0

16411642164316441645

17.26117.27217.28417.29617.308

19.41619.43019.44419.45719.471

11.74311.75411.76611.77811.790

2985.82987.62989.42991.22993.0

16461647164816491650

17.31917.33117.34317.35517.366

19.48519.49919.51219.52619.540

11.80111.81311.82511.83611.848

2994.82996.62998.43000.23002.0

16511652165316541655

17.37817.39017.40117.41317.425

19.55419.56719.58119.59519.609

11.86011.87111.88311.89511.907

3003.83005.63007.43009.23011.0

16561657165816591660

17.43717.44817.46017.47217.483

19.62219.63619.65019.66319.677

11.91811.93011.94211.95311.965

3012.83014.63016.43018.23020.0

16611662166316641665

17.49517.50717.51817.53017.542

19.69119.70519.71819.73219.746

11.97711.98812.00012.01212.024

3021.83023.63025.43027.23029.0

16661667166816691670

17.55317.56517.57717.58817.600

19.75919.77319.78719.80019.814

12.03512.04712.05912.07012.082

3030.83032.63034.43036.23038.0

16711672167316741675

17.61217.62317.63517.64717.658

19.82819.84119.85519.86919.882

12.09412.10512.11712.12912.141

3039.83041.63043.43045.23047.0

16761677167816791680

17.67017.68217.69317.70517.717

19.89619.91019.92319.93719.951

12.15212.16412.17612.18712.199

3048.83050.63052.43054.23056.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

319

16811682168316841685

17.72817.74017.75117.76317.775

19.96419.97819.99220.00520.019

12.21112.22212.23412.24612.257

3057.83059.63061.43063.23065.0

16861687168816891690

17.78617.79817.80917.82117.832

20.03220.04620.06020.07320.087

12.26912.28112.29212.30412.316

3066.83068.63070.43072.23074.0

16911692169316941695

17.84417.85517.86717.87817.890

20.10020.11420.12720.14120.154

12.32712.33912.35112.36312.374

3075.83077.63079.43081.23083.0

16961697169816991700

17.90117.91317.92417.93617.947

20.16820.18120.19520.20820.222

12.38612.39812.40912.42112.433

3084.83086.63088.43090.23092.0

17011702170317041705

17.95917.97017.98217.99318.004

20.23520.24920.26220.27520.289

12.44412.45612.46812.47912.491

3093.83095.63097.43099.23101.0

17061707170817091710

18.01618.02718.03918.05018.061

20.30220.31620.32920.34220.356

12.50312.51412.52612.53812.549

3102.83104.63106.43108.23110.0

17111712171317141715

18.07318.08418.09518.10718.118

20.36920.38220.39620.40920.422

12.56112.57212.58412.59612.607

3111.83113.63115.43117.23119.0

17161717171817191720

18.12918.14018.15218.16318.174

20.43620.44920.46220.47520.488

12.61912.63112.64212.65412.666

3120.83122.63124.43126.23128.0

17211722172317241725

18.18518.19618.20818.21918.230

20.50220.51520.52820.54120.554

12.67712.68912.70112.71212.724

3129.83131.63133.43135.23137.0

17261727172817291730

18.24118.25218.26318.27418.285

20.56720.58120.59420.60720.620

12.73612.74712.75912.77012.782

3138.83140.63142.43144.23146.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

320

17311732173317341735

18.29718.30818.31918.33018.341

20.63320.64620.65920.67220.685

12.79412.80512.81712.82912.840

3147.83149.63151.43153.23155.0

17361737173817391740

18.35218.36218.37318.38418.395

20.69820.71120.72420.73620.749

12.85212.86312.87512.88712.898

3156.83158.63160.43162.23164.0

17411742174317441745

18.40618.41718.42818.43918.449

20.76220.77520.78820.80120.813

12.91012.92112.93312.94512.956

3165.83167.63169.43171.23173.0

17461747174817491750

18.46018.47118.48218.49318.503

20.82620.83920.85220.86420.877

12.96812.98012.99113.00313.014

3174.83176.63178.43180.23182.0

17511752175317541755

18.51418.52518.53518.54618.557

20.89020.90220.91520.92820.940

13.02613.03713.04913.06113.072

3183.83185.63187.43189.23191.0

17561757175817591760

18.56718.57818.58818.59918.609

20.95320.96520.97820.99021.003

13.08413.09513.10713.11913.130

3192.83194.63196.43198.23200.0

17611762176317641765

18.62018.63018.64118.65118.661

21.01521.02721.04021.05221.065

13.14213.15313.16513.17613.188

3201.83203.63205.43207.23209.0

17661767176817691770

18.67218.68218.693

21.07721.08921.101

13.20013.21113.22313.23413.246

3210.83212.63214.43216.23218.0

17711772177317741775

13.25713.26913.28013.29213.304

3219.83221.63223.43225.23227.0

17761777177817791780

13.31513.32713.33813.35013.361

3228.83230.63232.43234.23236.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

321

17811782178317841785

13.37313.38413.39613.40713.419

3237.83239.63241.43243.23245.0

17861787178817891790

13.43013.44213.45313.46513.476

3246.83248.63250.43252.23254.0

17911792179317941795

13.48813.49913.51113.52213.534

3255.83257.63259.43261.23263.0

17961797179817991800

13.54513.55713.56813.58013.591

3264.83266.63268.43270.23272.0

18011802180318041805

13.60313.61413.62613.63713.649

3273.83275.63277.43279.23281.0

18061807180818091810

13.66013.67213.68313.69413.706

3282.83284.63286.43288.23290.0

18111812181318141815

13.71713.72913.74013.75213.763

3291.83293.63295.43297.23299.0

18161817181818191820

13.77513.78613.79713.80913.820

3300.83302.63304.43306.23308.0

°C

t90

Type TCu-

CuNimV

Type ENiCr-CuNimV

Type JFe-

CuNimV

Type KNiCr-

NimV

Type NNiCrSi-

NiSimV

Type SPt10Rh-

PtmV

Type RPt13Rh-

PtmV

Type BPt30Rh-Pt6Rh

mV

Type UCu-

CuNimV

Type LFe-

CuNimV

Pt100

Ω

Ni100

Ω

°F

t90

322

The most important methods for measuring temperature and their basic principles are described.

Numerous practical details provide the user with valuable information about temperature measurement in industrial applications.

03/T

EM

P-E

N R

ev.

B 0

4.20

11