When a third metal material is introduced into a thermocouple circuit, as long as the temperatures of the two junctions of this material are the same, the thermoelectric potential generated by the thermocouple will remain unchanged, i.e., it will not be affected by the introduction of the third metal into the circuit. Therefore, when measuring temperature with a thermocouple, a measuring instrument can be connected to measure the thermoelectric potential, and then the temperature of the measured medium can be determined. Thermocouple temperature measurement requires that the temperature of the cold junction (the measuring end is the hot junction, and the end connected to the measuring circuit through the lead wires is called the cold junction) remains constant, so that the magnitude of the thermoelectric potential is proportional to the measured temperature. If the cold junction (ambient) temperature changes during measurement, it will seriously affect the accuracy of the measurement. Taking certain measures to compensate for the effects caused by changes in cold junction temperature is called thermocouple cold junction compensation. Special compensating wires are used to connect to the measuring instrument.
Thermocouple Cold Junction Compensation Calculation Method:
From millivolts to temperature: Measure the cold junction temperature, convert it to the corresponding millivolt value, add it to the thermocouple's millivolt value, and then convert it to temperature;
From temperature to millivolts: Measure the actual temperature and the cold junction temperature, convert them to millivolt values separately, subtract them to obtain the millivolt value, and then obtain the temperature.
