Thermocouple temperature measurement is widely used in the temperature of the device, its main characteristic is the wide temperature range, stable performance, simple structure and good dynamic response at the same time, to facilitate the automatic control and centralized control. International application of thermocouple with a standard specification, the provisions on international thermocouple is divided into eight different degree, respectively b, r, s, k, n, e, j and t, its measuring temperature low measurable minus 270 degrees Celsius, higher up to 1800 degrees Celsius, including b, r, s belong to platinum series thermocouple, because platinum are precious metals, so they are also known as precious metal thermocouple and the remaining few called cheap metal thermocouple. There are two kinds of structure of the thermocouple, regular and type. Ordinary thermocouples generally by the hot electrode, insulation tube, to protect casing and junction box parts, and the type of thermocouple is the thermocouple wire, insulation material and metal protective casing combination after assembly, after stretching processing from a combination of a solid. But it takes a special electrical signal of thermocouple wires to pass, this kind of wire we called compensation conductor. Different thermocouples require different compensation conductor, its main function is connected to the thermocouple, away from the power of the reference junction of the thermocouple, so that the reference temperature stability. Compensation wire is divided into compensation type and extended type two kinds, extend the chemical composition of the wire and the compensation of thermocouple is the same, but in practice, to extend the type of wire is not used is the same as the thermocouple material of metal, usually use and thermocouple wires to replace with the same electron density.