Cold junction compensation in thermocouple is needed when the cold junction is not kept on a constant temperature. Rather that to provide temperature stabilizer on the junction, correcting the error by measuring the cold junction temperature is cheaper. Here is one of the circuits for such solution:
We can follow these steps to adjust the circuit:
- Adjust R1 for the voltage across R3 equal to the SEEBECK coefficient times the ambient temperature in degrees Kelvin.
- Adjust R2 for voltage across R4 corresponding to thermocouple: J 14.32mV, K 11.17mV, T 11.79mV, S 1.768mV
[Source: STMicroelectronics Application Note]