Transmitters come in two standard formats, head mounting (above image) or din rail mounting.
They are normally used where there is a need to run the sensor signal for a distance that could otherwise be subject to resistance error from sensor extension cable or otherwise where the instrumentation cannot read the standard sensor signal.
Input & output signals
Standard head transmitters are available for thermocouple or resistance (Pt100) input signals giving a 4-20mA current output via an in-line 24Vdc voltage source.
Din rail transmitters offer wider ranges including thermocouple, resistance, current and voltage inputs and current or voltage outputs. As they are powered by either Vac or Vdc supplies they do not need an in-line 24Vdc voltage source to produce outputs.