Simulating thermocouples and RTDs for calibration and testing
Thermocouples and RTDs are the most common sensors used in process temperature measurements. Simulating a process sensor signal into a process instrument or control system input enables a technician to verify whether the device responds correctly to the temperature measured by the instrument. There are many different ways to simulate these sensors for testing purposes. You can use a mV DC source and a mV versus temperature look up table (below on the left), for simulating thermocouples or a resistance decade box and resistance vs temperature look up table (below on the right), for simulating RTDs. This method, however, has become outdated with modern temperature calibrators that do the conversion for the user. With modern calibrators, simply select the sensor type to simulate, input the temperature to source and connect to the devices under test.
Thermocouple Table – Temperature vs mV
RTD Table – Temperature vs Resistance
°C
0
1
2
3
°C Ohm Diff. 0 100.00 0.39 1 100.39 0.39 2 100.78 0.39 3 101.17 0.39 4 101.56 0.39 5 101.95 0.39 6 102.34 0.39 7 102.73 0.39 8 103.12 0.39 9 103.51 0.39
°C Ohm Diff. 10 103.90 0.39 11 104.29 0.39 12 104.68 0.39 13 105.07 0.39 14 105.46 0.39 15 105.85 0.39 16 106.24 0.39 17 106.63 0.39 18 107.02 0.39 19 107.40 0.38
°C Ohm Diff. 20 107.79 0.39 21 108.18 0.39 22 108.57 0.39 23 108.96 0.39 24 109.35 0.39 25 109.73 0.39 26 110.12 0.39 27 110.51 0.39 28 110.90 0.39 29 111.28 0.38
0
0.000 0.039 0.079 0.119 0.397 0.437 0.477 0.517 0.796 0.838 0.879 0.919 1.203 1.244 1.285 1.326 1.612 1.653 1.694 1.735 2.023 2.064 2.106 2.147 2.436 2.478 2.519 2.561 2.851 2.893 2.934 2.976 3.267 3.308 3.350 3.391
10 20 30 40 50 60 70 80
90 3.682 3.723 3.765 3.806 100 4.096 4.136 4.179 4.220
Suggested test tools
Fluke Calibration 7526A Precision Process
Fluke 726 Precision Multifunction Process
Fluke 754 Documenting Process Calibrator - HART ® See pg 7
Fluke 712B RTD Temperature
Fluke 714B Thermocouple Temperature
Calibrator See pg 22
Calibrator See pg 8
Calibrator See pg 22
Calibrator See pg 7
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Temperature Applications
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