cold junction compensation

What is 'cold junction compensation'? What does 'cold junction compensation' mean?

The thermo-electromotive force of the thermocouple is generated according to the temperature difference between the hot and cold junctions. If the cold junction temperature fluctuates, the measurement data will fluctuate even if the hot junction temperature remains stable. For this reason, a separate sensor built into the controller is used to monitor any changes in the cold junction (terminal connected to the thermocouple), and the controller automatically compensates for these changes to keep the cold end of the device at 0 °C. This is called cold junction compensation.

Temperature Controllers