Thermocouple in the range of industrial applications more widely, and adapt to the environment is also very high, with the continuous development of science and technology, in order to better adapt to all kinds of bad environment, the types of thermocouple is gradually increasing, such as k type thermocouple and s type thermocouple. A, k type thermocouple and the platinum rhodium s type thermocouple advantages k type thermocouple 1, the advantages of high temperature metal thermocouple cheap, cheap, widely used, the annual output accounts for almost half of all the metal thermocouple 2, good reproducibility, approximate linear relationship between thermoelectric potential and temperature 3, thermoelectric potential: 52. 4 mv / 1300 ℃, high rate of thermoelectric potential: 41 uv / 4 ℃, good oxidation resistance can be used in oxidizing atmosphere and air medium and long-term single platinum rhodium s type thermocouple 1, high measuring accuracy, the advantages of single platinum rhodium s type thermocouple of all the thermocouple measurement precision high 2, physical and chemical performance is stable, good reproducibility 3, good oxidation resistance at high temperature, two types of thermocouple faults of k type thermocouple 1, stability is a bit poor, in the 150 - Magnetic change very easily within 200 ℃, 250 - 550 ℃ range, can appear the thermoelectric potential and heating process specification change not ( Back to the poor inconsistent) , if long-term use under high temperature, thermoelectric performance is not stable, not suitable for 2 in a vacuum, carbon, sulfur atmosphere the disadvantage of using single platinum rhodium s type thermocouple 1, precious metal thermocouple, the cost is high, in all thermocouple series, only slightly lower than b type thermocouple price 2, poor mechanical strength, small thermoelectric potential, especially the low temperature side, thermocouple is small, need with high sensitivity instrument, hot wire electrode diameter (3 0. 35mm- 0. 5毫米) Very fine, poor mechanical strength.