The temp transmitter is generally composed of a temperature probe (thermocouple or thermal resistance sensor) and a two-wire solid electronic unit. The temperature measuring probe is directly installed in the junction box in the form of a solid module to form an integrated transmitter. Temperature transmitters are generally divided into two types: thermal resistance and thermocouple.
The thermal resistance temperature transmitter is composed of the reference unit, an R/V conversion unit, linear circuit, reverse connection protection, current limiting protection, V/I conversion unit and so on. After the temperature measuring resistance signal is converted and amplified, the linear circuit compensates for the nonlinear relationship between temperature and resistance. After the V/I conversion circuit, a 4-20mA constant current signal with a linear relationship with the measured temperature will be generated.
An intrinsically safe thermocouple transmitter is generally composed of reference source, cold junction compensation, amplification unit, linearization processing, V/I conversion, broken couple processing, reverse connection protection, current limiting protection and other circuit units. It can amplify the thermoelectric potential generated by the thermocouple through cold junction compensation and then eliminate the nonlinear error between thermoelectric potential and temperature by a linear circuit, and finally amplify and convert it into a 4-20mA current output signal.
The temperature transmitter has a simple structure and can save lead with a large output signal, strong anti-interference ability, good linearity, simple display instrument, solid module anti-vibration and moisture-proof, reverse connection protection and current limiting protection, and reliable operation.
The output of the temperature transmitter is a unified 4-20mA signal and it can be matched with a microcomputer system or other conventional instruments. It can also be made into explosion-proof or fire-proof measuring instruments according to user requirements.