Zero Speed Switches

Zero speed switch is suitable for detecting the absence or presence of motion of rotating, reciprocating or conveying equipment. Thus, it’s a speed limit switch that gives an indication when the system is at rest. A suitable motion detector probe is provided depending on the application.


When power is initially applied to the zero speed switch, the alarm relay is energized and held by the timing circuit for desired (settable) time duration. Whenever the motion detector sensor detects a target, a signal in the form of pulse re-triggers an internal timing circuit. This action keeps the alarm relay energized providing a fail-safe operation of the contacts. If no target is sensed for desired time duration (that is settable), the timing circuit will not be re-triggered. This will cause the alarm relay to de-energies and the contacts to change state. Thus the relay output contact can be used for signaling / controlling.

Mechanical Specifications

Cable Entries

  • 2 nos.

 Operating Temperature

  • -20°C to +60°C


  • Cast aluminium, weatherproof Stoving enamel painted


  • By potential-free N.O. contact of contactor controlling the motor of
    the monitored equipment

Start-up Time Delay

  • 3 sec to 20 sec

Zero Speed Time

  • 3 ppm to 20 ppm
Electrical Specifications


  • 110 / 230 V AC (-10 to +10%) 50 Hz (as specified in the order)

Power Consumption

  • ____mW


  • One relay with a set of potential-free c.o. contact rated at 6A, 230 V
    AC, 50Hz for non-inductive load


Application Specifications

Zero speed switch is suitable for detecting the absence or presence of motion of rotating, reciprocating or conveying equipment.

Switching Indication
  • 3 LED’s
  • Red: Alarm (relay de-energized), Green: Normal (relay energized), Yellow: Pulse Detection