Thermocouple is a kind of temperature sensing element, is a form of instrument. It can be directly used to measure the temperature, and convert the temperature signal into a thermoelectric signal, which can be converted into the temperature of the medium through the electrical instrument. The basic principle of thermocouple temperature measurement is that two different components of the material body composed of a closed loop, when there is a temperature gradient at both ends, there will be a current through the loop, at this time there is a thermoelectric motive force between the two ends, this phenomenon is called Seebeck effect. The conductor of different components is a thermal electrode, the higher temperature end is the working end, the lower temperature end is the free end, and the free end is usually in a constant temperature. According to the mathematical relationship between thermoelectric motive force and temperature, the index table of thermocouple is made.

Access a third metal material in the thermocouple loop, as long as the temperature of the two contacts of this material is the same, the heat generated by the thermocouple remains unchanged, that is, it is not affected by the third metal access loop. Therefore, in the thermocouple temperature measurement, you can access the measuring instrument, after measuring the thermoelectric motive force, you can know the temperature of the measured medium.

When the thermocouple measures the temperature, the temperature at the cold end of the thermocouple is required to remain constant, and its thermoelectric potential is proportional to the measured temperature. If the ambient temperature of the cold end changes during measurement, the accuracy of measurement will be seriously affected. At the cold end, some measures must be taken to compensate.

Thermocouple characteristics

1, simple assembly, easy to replace

2, pressure spring temperature sensing element, good seismic performance

3, large measuring range (-200℃ ~ 1300℃, under special circumstances -270℃ ~ 2800℃)

4, high mechanical strength, good pressure resistance

5, high temperature resistance (2800℃)