The difference between pressure transmitter and temperature transmitter
1. Integrated temperature transmitter
The integrated temperature transmitter generally consists 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. Integrated temperature transmitters are generally divided into two types: thermal resistance and thermocouple.
Thermal resistance temperature transmitter is composed of reference unit, 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 is output.
Thermocouple temperature 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 is to amplify the thermoelectric potential generated by the thermocouple through cold junction compensation, and then use a linear circuit to eliminate the nonlinear error of thermoelectric potential and temperature, and then amplify and convert it into a 4-20mA current output signal. In order to prevent accidents caused by the failure of temperature control due to the broken wire of the thermocouple in the thermocouple measurement, a power-off protection circuit is also provided in the transmitter. When the thermocouple is broken or poorly connected, the transmitter will output the maximum value (28mA) to make the meter cut off the power supply.
The integrated temperature transmitter has the advantages of simple structure, saving leads, 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 integrated temperature transmitter is a unified 4-20mA signal; 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 as required by users.
