Operating principle of platinum-rhodium thermocouple with high temperature resistance: two different conductors (called thermocouple wires or thermoelectrodes) are connected at two ends to form a circuit. When the temperature of the junction points is different, electromotive force will occur in the circuit. This phenomenon is called thermoelectric effect, and this electromotive force is called thermoelectric force.

Thermocouples use this principle to measure temperature. In the meantime, one end directly used to measure medium temperature is called the operating end (also called the measuring end), the other end is called the cold end (also known as the compensation end). The cold end is connected with the appearances or matching appearances, and the appearances indicate the thermoelectric potential of the thermocouple.

Thermocouple is actually an energy converter. It converts heat energy into electricity. Temperature is measured by the thermal potential of the thermocouple. Regarding the thermal potential of the thermocouple, the thermal potential of the thermocouple is the difference of the temperature function between the two ends of the thermocouple, not the function of the temperature difference between the two ends of the thermocouple. When the data of the thermocouple are uniform, it has nothing to do with the length and diameter of the thermocouple, only with the composition of the data of the thermocouple and the temperature difference between the two ends.

When the two thermocouple wire data components of the thermocouple are confirmed, the thermoelectric potential of the thermocouple is only related to the temperature difference of the thermocouple; if the temperature of the cold end of the thermocouple is constant, the thermoelectric potential of the thermocouple is only a single function of the temperature of the working end. Two kinds of conductors or semiconductors A and B are welded together to form a closed loop.

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