What issues should be paid attention to in the application of thermocouples
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Two conductors of different components (called thermocouple wire or thermoelectrode) are connected at both ends to form a loop. When the temperature of the junction is different, an electromotive force will be generated in the loop. This phenomenon is called the thermoelectric effect, and this electromotive force is called the thermoelectric potential. Thermocouples use this principle to measure temperature. Among them, the end directly used to measure the temperature of the medium is called the working end (also called the measuring end), and the other end is called the cold end (also called the compensation end); the cold end is connected to the display surface or the matching surface, and the display surface will indicate the thermoelectric potential generated by the thermocouple.
A thermocouple is actually an energy converter that converts thermal energy into electrical energy and uses the generated thermoelectric potential to measure temperature. Regarding the thermoelectric potential of a thermocouple, the following issues should be noted:
(1) The thermoelectric potential of a thermocouple is the difference between the temperature functions at both ends of the thermocouple, not the function of the temperature difference at both ends of the thermocouple;
(2) When the material of the thermocouple is uniform, the size of the thermoelectric potential generated by the thermocouple has nothing to do with the length and diameter of the thermocouple, but only with the composition of the thermocouple material and the temperature difference at both ends;
(3) When the material composition of the two thermocouple wires of the thermocouple is determined, the size of 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 remains constant, then the thermoelectric potential of the thermocouple is only a single-valued function of the working end temperature.
