what does a temperature transmitter do
A temperature transmitter works by connecting to it some form of temperature sensor. For example a RTD (Resistance temperature device) or Thermocouple. In the case of a RTD connected to the transmitter the transmitter measures a change in resistance of the RTD proportional to the change in temperature measured.The transmitter then derives a current output (generally 4-20mA) which can be measured by an instrument, such as a PLC, loop indicator ect. degrees = 4mA, 100 degrees = 20mA. A excitation supply will be connected to the transmitter and the 4-20mA will flow in this loop back to the measuring instrument. It is necessary to use the correct type of sensor for the application to get the best accuracy when measuring.