Thermocouple is mainly the use of electric potential difference between the two electrodes to implement measuring, two electrodes to form a loop, so the choice of electrode is very important in the thermocouple is also essential. Commonly used thermocouple could be divided into two types: standard thermocouple and non-standard thermocouple. Standardized thermocouple from January 1, 1988, thermocouple and thermocouple were manufactured according to iec international standard, and specify the s, b, e, k, r, j, t seven standardization thermocouple type thermocouple for China unified design. Thermocouple indexing number, heat the positive negative electrode materials s 10 pure platinum and platinum rhodium r 13 pure platinum and platinum rhodium platinum rhodium platinum rhodium 30 6 b, nickel chromium nickel silicon, k t pure copper, copper nickel j iron copper and nickel, n nickel chrome silicon, silicon nickel e nickel chromium copper nickel, in theory, any two different conductors ( Or a semiconductor) Can be made into thermocouple, but as a practical temperature measurement component, is various to the requirement of it. In order to guarantee the reliability of engineering, as well as the measuring accuracy of enough, not all materials can form a thermocouple. General electrode materials of thermocouple, basic requirements is within the scope of the temperature measurement, thermoelectric properties of stability, not change with time, have physical and chemical stability, less susceptible to corrosion and oxidation; Small temperature coefficient of resistance, high electrical conductivity, specific heat; Temperature of thermoelectric ShiYao is big, and between thermoelectric potential and temperature is linear or close to linear single valued function relation; Material replication is good, high mechanical strength, simple manufacturing process, the price is cheap.