Working principle of high temperature resistant platinum rhodium thermocouple: two conductors with different components (called thermocouple wire or thermoelectric pole) are connected to form a circuit. When the temperature of the junction is different, electromotive force will occur in the circuit. This phenomenon is called thermoelectric effect, and this electromotive force is called thermoelectric potential.

 

　　

The thermocouple uses this principle to measure the temperature. In this process, one end directly used to measure the temperature of the medium is called the working end (also known as the measuring end), and the other end is called the cold end (also known as the compensation end). The cold end is connected with the appearance or matching appearance, and the appearance will indicate the thermoelectric potential of the thermocouple.
Thermocouple is actually a kind of energy converter, which converts heat energy into electric energy, and measures the temperature with the thermoelectric potential. As for the thermoelectric potential of thermocouple, the thermoelectric potential of thermocouple is the difference between the temperature functions of two ends of thermocouple, not the function of the temperature difference between two ends of thermocouple. The thermoelectric potential of thermoelectric couple is large and small. When the data of thermocouple is uniform, the length of thermocouple is the same as that of thermocouple It has nothing to do with the diameter, only with the composition of the thermocouple data and the temperature difference between the two ends.
When the data components of two thermocouple wires 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 certain, the thermoelectric potential of the thermocouple is only a single value function of the temperature of the working end. Two kinds of conductors or semiconductors A and B with different materials are welded together to form a closed circuit.

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