What is the intermediate temperature law of thermocouples?

The intermediate temperature law of thermocouples means that in a thermocouple loop, if a conductor of a third material is connected, as long as the temperature of both ends of the third conductor is the same and the conductor is in a uniform temperature field, the thermoelectric potential generated by the thermocouple has nothing to do with the material and length of the intermediate conductor, but only with the temperature of both ends of the thermocouple.
For example, in a temperature measurement loop composed of thermocouples A, B and connecting wire C, as long as the temperature of both ends of connecting wire C (i.e., the cold end of the thermocouple) is the same, no matter what the material of wire C is or what temperature field it is in, the thermoelectric potential of the entire loop depends only on the temperature of the hot and cold ends of the thermocouple, and has nothing to do with connecting wire C.
This law provides an important basis for the practical application of thermocouples, so that various instruments, connecting wires and other intermediate components can be connected to the thermocouple temperature measurement loop without affecting the accuracy of the measurement results, which greatly facilitates the use of thermocouples and the design of temperature measurement systems.