How to Calibrate a Thermocouple Transmitter ~ Learning Instrumentation And Control Engineering Learning Instrumentation And Control Engineering

How to Calibrate a Thermocouple Transmitter

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To calibrate a thermocouple transmitter will require a thermocouple simulator with an accuracy of at least four times greater than the thermocouple sensor we desire to calibrate. 

Equipment and Materials Required
The following equipment/materials are required to successfully calibrate a thermocouple transmitter:
  1. Thermocouple Simulator (of at least four times the accuracy of sensor)
  2. Two Digital Voltmeters (Five-digit readout) with accuracy of at least ±0.01% with resolution 1mV
  3. 24 VDC Power Supply of at least 35 – 40mA current output
  4. Thermocouple wire of the same type of wire the thermocouple transmitter is constructed of.

Equipment Setup
Below is the equipment set up for the calibration


Calibration Procedure
  1. Remove the thermocouple transmitter terminal housing cover
  2. If the transmitter is already connected, remove all the thermocouple lead connections.
  3. Determine the base and full scale temperatures. Read: How to convert thermocouple millivolt to temperature.
  4. Turn power supply on.
  5. Consult the thermocouple simulator manual for instructions on setting the thermocouple type and engineering units.
  6. Set the simulator to the base (zero) temperature and adjust the zero pot until the output is 4mA or 40mV at the test terminals
  7. Set the simulator to the full scale temperature and adjust the span pot until the output is 20mA
  8. Repeat steps (1-7) above until both the 4 and 20mA readings are obtained without re-adjusting the span and zero pots.