Fisher 546, 546S, and 546NS transducers receive a direct-current input signal and use a torque motor, nozzle-flapper, and pneumatic relay to convert the signal to a proportional pneumatic output signal. Nozzle pressure, which operates the relay, is also piped to the torque motor feedback bellows. This provides a comparison between input signal and nozzle pressure and corrects errors in nozzle pressure.


  • High natural frequency of torque motor moving parts results in negligible vibration influence. Meets typical seismic requirements for nuclear service.
  • Screw driver adjustments for span and zero are conveniently located and have arrows indicating rotation to increase settings.
  • No additional are parts required to reverse action.
  • Integrated pneumatic relay is mounted outside case and can be removed without disturbing electrical or pressure connections or impairing explosion safety.

546  Bulletin  Instruction Manual