What is Cold Junction Compensating (CJC)?

A thermocouple measurement always needs information from joined wire end (hot junction) and open wire end (cold junction). The cold junction is also called reference point. Variations of reference point temperature are compensated with CJC measuring (Cold Junction Compensation). Temperature transmitters CJC measuring can be an internal function or a measuring resistor integrated in connectors. If the reference point is far away from the transmitter, a separate temperature measuring of that point has to be implemented and wired to transmitter as compensation signal. More details on page How does a thermocouple (TC sensor) work?