Thermocouple Cold Junction Compensation (Compensation for Grounded Thermocouple)

Cold junction error in thermocouple can be seen as an offset drift that depend on the cold junction temperature. we can use the following circuit to correct this error for grounded thermocouple configuration:

Thermocouple cold junction compensation (compensation for grounded)

Adjustments: compensates for both sensor and resistor tolerances

  • Short 1N4568
  • Adjust R1 for SEEBECK coefficient times the ambient temperature (in K degrees) across R3.
  • Short LM135 and adjust R2 for voltage across R3 corresponding to thermocouple type: J=14.32mV, K=11.17mV, T=11.79mV, and S=1.768mV

[Source: SGS Thomson Application Note]