Post on 15-Jul-2015
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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.
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Semih Dogan, Kocaeli University, 06.11.2014
Type of temperature measuring devices
– Thermometers
– Thermocouples
– Resistance Temperature Detectors (RTD’s)
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Semih Dogan, Kocaeli University, 06.11.2014
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
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Semih Dogan, Kocaeli University, 06.11.2014
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.
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Semih Dogan, Kocaeli University, 06.11.2014
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.
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Semih Dogan, Kocaeli University, 06.11.2014
Thermocouples
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A construction of a J type Thermocouple
Semih Dogan, Kocaeli University, 06.11.2014
Thermocouples
– The table belows shows the different types of thermocouples with construction of
non-similar metals.
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Semih Dogan, Kocaeli University, 06.11.2014
Thermocouples
– This chart shows the characteristics different types of thermocouples.
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Semih Dogan, Kocaeli University, 06.11.2014
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.
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Semih Dogan, Kocaeli University, 06.11.2014
Resistance temperature detectors ( RTD )
– RTD’s has different wiring and connection type for sensitivity of application.
– Lead and reference pins are depending on measurement sensitivity.
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Semih Dogan, Kocaeli University, 06.11.2014
Resistance temperature detectors ( RTD )
– 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
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Public
Semih Dogan
Kocaeli University
06.11.2014
Experiment with PT100 (RTD) Controlled Heat and Cool Operation of A Medium
Semih Dogan, Kocaeli University, 06.11.2014
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.
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Semih Dogan, Kocaeli University, 06.11.2014
RTD Controlled Heat&Cool of Medium
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Semih Dogan, Kocaeli University, 06.11.2014
Construction of Block and Electrical Panel
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Semih Dogan, Kocaeli University, 06.11.2014
Electrical Connections of Panel
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Semih Dogan, Kocaeli University, 06.11.2014
RTD Controlled Heat&Cool of Medium
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– Endress Hauser RIA 250
Semih Dogan, Kocaeli University, 06.11.2014
RTD Controlled Heat&Cool of Medium
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Semih Dogan, Kocaeli University, 06.11.2014
RTD Controlled Heat&Cool of Medium
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Semih Dogan, Kocaeli University, 06.11.2014
RTD Controlled Heat&Cool of Medium
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Semih Dogan, Kocaeli University, 06.11.2014
Conclusion
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– 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.
Semih Dogan, Kocaeli University, 06.11.2014
Thank you very much
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