Data source: Beijing Carrier Air Conditioning Repair Phone http://blog.sina.com.cn/kailikongtiaoweixiu.
Carrier Air Conditioning Repair Q&A; How to use a thermocouple thermometer
The conductors in the thermocouple are called thermoelectrodes, and these thermoelectrodes have (+) and (-) poles. By connecting a millivoltmeter to the thermoelectric plate of this thermocouple, the thermoelectric potential value in the circuit can be measured. The high or low value of the thermoelectric potential reflects the change in temperature. The thermocouple thermometer used in air conditioners adopts a copper-constantan thermocouple, where the hot end wire 1 is the positive pole and is connected to the positive (+) pole of the electrical measuring instrument, and the cold end wire 2 is the negative pole and is connected to the negative (-) pole of the electrical measuring instrument. In this case, for every 1℃ change in the measured temperature, the thermoelectric potential changes by approximately 0.041mV. Using this characteristic, a thermocouple thermometer for measuring temperature can be made.