Standard temperature transmitters generally send a 4–20 ma. signal to indicate the temperature. They are calibrated for a specific range of temperature such as 0 to 100 degrees. Standard transmitters are designed to operate with one type of sensor such as RTD, thermocouple, etc. Any changes to the setting require a recalibration of the unit.
Smart transmitters contain an internal microprocessor and can be calibrated from the control room by sending a signal to the transmitter. It is also possible to check the transmitter for problems from a remote location.