Thermocouple has to bend, heat resistance to high pressure, fast response time and the advantages of strong and durable, thermocouple, thermocouple and fabricated as measure temperature sensor, thermocouple and usually display instrument, recorder and electronic regulator, at the same time, the thermocouple is also can be used as a prefabricated thermocouple temperature sensing element. Thermocouple can be directly measured from 0 ℃ ~ 1100 ℃ in the process of various production within the scope of the liquid, steam and gas medium, as well as the temperature of the solid surface. The working principle of thermocouple is composed of two different ingredients of conductor on both ends of the welding, forming circuit, direct measure WenDuan call side, the measurement terminal called reference. When when there is a difference in temperature measuring end and reference end will produce thermal current in the circuit, digital display table is connected, digital display table will indicate the thermocouple thermoelectric emf generated by the corresponding temperature value. The thermocouple thermoelectric emfs growth over the course of measuring the temperature, the size of the thermoelectric emfs and thermocouple temperature difference on both ends of the conductor material and, only the length of the hot electrode, the diameter has nothing to do. The structure of the thermocouple is by the conductor, insulation by repeated drawing magnesium oxide and 1 cr18ni9ti stainless steel protecting tube, thermocouple products is mainly composed of junction box, terminal and thermocouple basic structure, and with various mounting device. Thermocouple insulation type and hull type two kinds.