Temperature Sensors

Public

Semih Dogan

Kocaeli University

06.11.2014

Temperature Sensors

Public

Semih Dogan

Kocaeli University

06.11.2014

Introduction to Temp. Sensors

Semih Dogan, Kocaeli University, 06.11.2014

What is Temp. Sensors?

– Temperature Sensors are devices that can sense the difference amount of heat

between application space and reference.

– They are used to measure temperature and change of heat transfer of a medium.

Public, Temperature Sensors, Introduction to Temp. Sensors3


Type of temperature measuring devices

– Thermometers

– Thermocouples

– Resistance Temperature Detectors (RTD’s)



Thermometers

– Filled Thermometers are filled with a liquid such as heat can cause expansion or

evoporation on it. So that, liquid can pressurized. The pressure is related to the

temperature and it may be indicated on a simple gauge.

– Advantage: low cost, simple

– Disadvantage: no remote measurement



Thermometers

– Bimetal thermometers are constructed by bonding two metals with different

coefficients of thermal expansion.

– If heat is applied to the end of strip, the metal with the higher coefficient of expansion

will bend more than lower one.



Thermocouples

– A thermocouple consist of two pieces of dissimilar metals with their ends joined

together. (twisting, soldering, welding)

– When the heat is applied to the junction, a voltage (emf) in the range of mV is

generated.

– The voltage of emf produced depends on;

– 1. Types of material used

– 2. Temperature of junction, measuring and referance.



Thermocouples


A construction of a J type Thermocouple


Thermocouples

– The table belows shows the different types of thermocouples with construction of

non-similar metals.



Thermocouples

– This chart shows the characteristics different types of thermocouples.



Resistance temperature detectors ( RTD )

– RTD’s are the resistance of a conductor usually increase as the temperature

increase.

– If the properties of that conductor are known, the temperature can be calculated from

the measured resistance.

– The most common RTD’s are PT100, PT 1000 and Ni100

– The different RTD’s analyse 0°C with different resistive values. For example, PT 100

is 100Ω at 0°C.

– The temperature can be found by using The Callender Van-Dusen equations.




– RTD’s has different wiring and connection type for sensitivity of application.

– Lead and reference pins are depending on measurement sensitivity.




– Stability in the temperature range to measured. The material must be not

melt,correde,embattle or change electrical characteristics when subjected to the

environment in which it will operate.

– Linearitiy the resistance change with temperature should be as linear as possible

over the range of interest to simplfy readout.

– Response Time If the process requires a very fast response to temperature changes,

RTD’s are the best choice. Time response is measured around e.g. 2.5ms to 10ms

– Workability the material must be suitable for configurating for insertation into media.

– Range most RTD’s can operate -200 to 600°C


Public

Semih Dogan

Kocaeli University

06.11.2014

Experiment with PT100 (RTD) Controlled Heat and Cool Operation of A Medium


Experiment

– By the reference of RTD, we can control the temperature of a medium in a specified

range.

– PT 100 is connected to the Endress-Hauser which is a universal indicator by the

output of this process indicator, cooling for Fan or heating cartridge heaters will be

activated.

– Relay outputs of RTD analyser can control 2 contactors of heat and cool operation.

– Delay time, set point, hysteresis, output functions, display operations can be

programmed by EEPROM inside of indicator.



RTD Controlled Heat&Cool of Medium



Construction of Block and Electrical Panel



Electrical Connections of Panel





– Endress Hauser RIA 250


Conclusion


– In general, thermocouples are cheaper, more durable and can measure a bigger

range of temperature while RTD’s produce better and more reliable measurements.

– Both temp. Sensors are versatile that have high accuracy over a wide range of

industrial applications.


Thank you very much


Temperature Sensors

Engineering

Transcript of Temperature Sensors