What is cold junction compensation?

IEC 60584-1/JIS C1602 specifies Thermocouple characteristics when TC = 0°C.
However, it is not realistic to operate a system with sensor input devices cooled to 0°C.

For this reason, the TC temperature is measured using a "Cold Junction Sensor" installed in the sensor input device.
The thermoelectromotive force (VOUT) from the thermocouple is compensated for by taking TC into account, and the temperature (TH) at the measurement location is calculated.

We call this method cold junction compensation.
The figure below is an overview of the cold junction compensation function.

You may get ADC fault when an error has occurred in the ADC (Analog to Digital Converter) installed in the sensor input device.