Widely used in our country at present and the standardization of production standardization of commonly used thermocouple mainly has the following classification, platinum rhodium 30-1 Platinum-rhodium thermocouple 6 this is a kind of precious metal high temperature thermocouple, platinum rhodium 30 as positive, platinum, rhodium 6 for the anode, the index number is b. Since both hot electrode is platinum rhodium, thus increasing the pollution resistance and mechanical strength, its thermal properties are stable at high temperatures, appropriate use in oxidizing and neutral atmosphere, in a vacuum can be used short term. Long-term use of temperature can reach 1600 ℃, short-term use temperature to 1800 ℃. The thermocouple thermoelectric potential and thermoelectric potential rates are small and, therefore, the cold end temperature below 40 ℃, when using the cold end temperature compensation generally don't have to. 2, platinum rhodium - 10 Platinum thermocouple in platinum rhodium - 10 Platinum thermocouple to platinum rhodium 10 silk as the anode, pure platinum wire as cathode, index number is s. Its measuring range is - 20 ~ 1300 ℃, under the good environment can be short-term measure 1600 ℃; Suitable for use in oxidizing or neutral medium, high temperature resistant, unfavorable oxidation; Has good chemical stability; A higher measuring accuracy and can be used for precision temperature measurement and the benchmark thermocouple. 3, nickel chromium - Nickel aluminum or nickel chrome - Nickel silicon thermocouple ( Type) This is a cheap metal thermocouple to measure high temperature, nickel chromium alloy as anode, aluminum nickel ( Or nickel silicon) Alloy anode, its index number is k, it has good resistance to oxidation and corrosion resistance; Its good reproducibility; Thermoelectric potential; Relationship between thermoelectric potential and temperature approximate to linear relationship; The cost is low, although the measuring accuracy is not high, but it can meet the requirements of industrial temperature measurement, is commonly used on industrial thermocouple; The long using temperature is 1000 ℃, short-term use temperature to 1200 ℃. 4, copper - Constantan thermocouple this is a cheap metal thermocouple, with copper as the anode, constantan as cathode, its index number for t. Because of the heat copper electrode extremely easy oxidation, generally should not be used in the oxidizing atmosphere more than 300 ℃. The thermocouple thermoelectric potential rate is bigger, the thermoelectric properties is good, the material quality of a material is uniform, the cost is low, but poor reproducibility. In 0 ~ - 100 ℃ temperature range for second-class standard thermocouple, accuracy of plus or minus 0. 1℃。 Usually copper - Constantan thermocouple used in ℃ range of temperature measurement.