Thermocouple principle of thermocouple is a thermal device, which converts the signal temperature thermoelectric emf signal, through electric instrument converts the temperature of the measured medium. Thermocouple temperature measurement is the basic principle of two kinds of different ingredients of homogeneous conductor closed loop, when temperature gradient is at both ends, the loop will have an electric current passes through, the existed seebeck electromotive force between two ends - thermoelectric emf, this is the so-called seebeck effect. Two different components of homogeneous conductor electrode as heat, the temperature is higher for work at the end of the end, one end of the low temperature as the free end, usually free end under a constant temperature. According to the thermoelectric emf as a function of temperature, the thermocouple indexing table; Indexing table is free end temperature at 0 ℃, under the condition of different thermocouples with different indexing table. Access in the thermocouple loop when the third metal material, the two contacts at the same temperature as long as the material, produced by the thermocouple thermoelectric is set to remain the same, which is not affected by the third metal access in the loop. Therefore, when the thermocouple temperature measurement, can be connected to the measuring instrument, measured after the thermoelectric emfs, can know the temperature of the measured medium. Thermocouple advantages of thermocouple is the temperature of the temperature measuring device is commonly used in industry, has the following features high measuring accuracy: thermocouple direct contact with the object being measured, is not affected by the medium in the middle of the. Fast thermal response time: thermocouple is responsive to temperature changes. Measuring range: thermocouple from - 40 ~ + 1600 ℃ can be continuous temperature measurement. Reliable performance, good mechanical strength. Long service life, easy to install. Thermocouple type and structure ( 1) A thermocouple type thermocouple type k ( Nickel chrome - Nickel silicon) WRN series, n ( Nickel chromium silicon - Nickel silicon magnesium) WRM series, e ( Nickel chrome - Copper and nickel) Wre series, j ( Iron - Copper and nickel) WRF series, t ( Copper - Copper and nickel) WRC series, s ( Platinum rhodium - 10 Platinum) WRP series, r ( Platinum rhodium - 13 Platinum) WRQ series, type b ( Platinum rhodium - 30 Platinum rhodium (6) WRR series and so on. ( 2) The structure of thermocouple, thermocouple is the basic structure of hot electrode, insulation and protection tube; And display instrument and record instrument or computer systems. According to the environment in the field use, developed into a variety of factors such as measured medium is suitable for all kinds of thermocouple. Thermocouple is divided into simple fabricated thermocouple, thermocouple and a special form of thermocouple; Segmentation by using environment with high temperature thermocouples, wear-resistant thermocouple, thermocouple, corrosion resistance to high pressure thermocouple, thermocouple, flame-proof aluminum liquid temperature with thermocouple, circulating fluidized bed with thermocouple, cement rotary kiln with thermocouple, anode baking furnace with thermocouples, high temperature hot blast stove with thermocouple, stove with thermocouples, with thermocouple carburizing furnace, high temperature salt bath furnace with thermocouple, copper, iron and steel with thermocouple, antioxidant tungsten-rhenium thermocouples, vacuum furnace with thermocouple, platinum, rhodium thermocouple, etc.