Today's industrial production process control and measuring temperature, thermocouple is indispensable to a device. Standard thermocouple and no unified standard score table, but according to iec standard production, specify s, b, e, k, r, j, t seven sexual type thermocouple for unified design. Thermocouple used index number: s, r, b, n, k, e, j, t, we nine. S, r, b belong to precious metal thermocouple, n, k, e, j, t belong to cheap metal thermocouple. Number 1, s degree is characterized by strong antioxidant properties, appropriate continuous use in oxidation, the inert atmosphere, the long-term use of temperature 1400 ℃, 1600 ℃ in the short term. Number 2, r degree compared with s degree, in addition to the thermoelectric emfs big by about 15%, other properties are almost identical; Number 3, b dividing minimal thermoelectric emfs at room temperature, so the general without compensation conductor when measuring. Its long using temperature is 1600 ℃, 1800 ℃ in the short term. Can be used in the oxidation or neutral atmosphere, and also can be used under vacuum conditions in short term. Number 4, n index under 1300 ℃ is the feature of high temperature oxidation resistance is strong, the long-term stability of the thermoelectric emfs and short-term thermal cycle of good repeatability, nuclear radiation resistance and low temperature resistance, can partially replace # s dividing thermocouple; No. 5, k index is characterized by strong antioxidant properties, appropriate continuous use in oxidation, the inert atmosphere, the long-term use of temperature 1000 ℃, 1200 ℃ in the short term. Widely used in all thermocouple; Number 6, e index is in commonly used thermocouple, the characteristics of the thermoelectric emfs, namely high sensitivity. Appropriate continuous use in oxidation, the inert atmosphere, using temperature 0 800℃; No. 7, j dividing is characteristic of both can be used for oxidizing atmosphere ( Using the maximum temperature 750 ℃) , also can be used in a reducing atmosphere ( Using the maximum temperature 950 ℃) And resist the corrosion of gas h2 and co, used in refining and chemical industry; Number 8, t index of all the cheap metal thermocouple is the feature of high precision grade, usually used to measure the temperature under 300 ℃ in all thermocouples, s degree, high precision grade, usually used as a standard thermocouple.