Thermocouple and thermocouple temperature transmitter, as a new generation of temperature measuring meter, can be widely applied to metallurgy, petroleum, chemical, power, light industry, textile, food, national defense and scientific research and other industries, can be directly installed on the thermocouple, thermocouple terminal box and the formation of integration of the structure. And commonly used integrated temperature transmitter is usually divided into two kinds: thermocouple temperature transducer and thermocouple temperature transmitter. Then the two temperature transmitter in everyday use, how do we distinguish between. Thermocouple temperature transmitter by the reference source, cold junction compensation, amplifier unit, linearization, v/I conversion, broken accidentally processing, reverse connect protection, current limiting circuit protection units. It is the cold junction compensation of thermocouple thermoelectric potential enlarged, cap again by linear circuit to eliminate nonlinear error, the thermoelectric potential and temperature after amplification into 4 ~ 20 ma current output signal. In order to prevent the thermocouple measurement by thermocouple wire break and make the temperature control failure caused by accident, transmitter will also include a power protection circuit. When the thermocouple wire break or pick up solution, transducer outputs larger values ( 28ma) In order to make the instrument to cut off the power supply. Thermocouple temperature transmitter is the r/v conversion unit, the benchmark unit, linear circuit, reverse connect protection, current limiting protection, v/I conversion unit, etc. Temperature measuring thermocouple signal amplification, and then by linear circuit of temperature compensate nonlinear relationship with the resistance, after the v/I conversion circuit outputs a measured a linear relationship with temperature and constant current signal of 4 ~ 20 ma.