A temperature transmitter is an electrical instrument that interfaces a temperature sensor for example a thermocouple, RTD, or thermistor sensor to a measurement or control device like a PLC, DCS, PC, loop controller, data logger, display, recorder, etc.
Typically, temperature transmitters isolate, amplify, filter noise, linearize, and convert the input signal from the sensor then send or transmit a standardized output signal to the control device. Common electrical output signals used in manufacturing plants are 4-20mA or 0-10V DC ranges. For example, 4mA could represent 0°C and 20mA means 100°C.
Temperature Transmitter Inputs
A thermocouple sensor is a pair of dissimilar metal wires joined at one end. The junction produces a low level voltage proportional to the difference in temperature between the open and closed ends.
An RTD or Resistance Temperature Detector is a passive circuit element whose resistance increases with increasing temperature in a predictable manner.