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:
- Thermocouple Simulator (of at least four times the accuracy of sensor)
- Two Digital Voltmeters (Five-digit readout) with accuracy of at least ±0.01% with resolution 1mV
- 24 VDC Power Supply of at least 35 – 40mA current output
- Thermocouple wire of the same type of wire the thermocouple transmitter is constructed of.
Below is the equipment set up for the calibration
- Remove the thermocouple transmitter terminal housing cover
- If the transmitter is already connected, remove all the thermocouple lead connections.
- Determine the base and full scale temperatures. Read: How to convert thermocouple millivolt to temperature.
- Turn power supply on.
- Consult the thermocouple simulator manual for instructions on setting the thermocouple type and engineering units.
- Set the simulator to the base (zero) temperature and adjust the zero pot until the output is 4mA or 40mV at the test terminals
- Set the simulator to the full scale temperature and adjust the span pot until the output is 20mA
- Repeat steps (1-7) above until both the 4 and 20mA readings are obtained without re-adjusting the span and zero pots.