Thermocouple is a very important accessory used in heat treatment. Its quality and accuracy directly affect the quality of heat treatment. It must be tested by government agencies before using. Thermocouple can be divided into two types: armoured thermocouple and simple thermocouple. Armoured thermocouple wraps 2 thermo wires with quartz sand filled in a stainless steel tube. The simple thermocouple covers two thermo wires with ceramic tube directly.