CMG Series Self-powered Go No-Go AC Current Monitoring Relay

The CMG Series Self-powered Go No-Go AC Current Monitoring Relay from the ATC Diversified Electronics division of Marsh Bellofram is self-powered solid state go-no-go current monitoring relay, designed to detect the presence of AC current. No physical connection is required as the line to be monitored is magnetically coupled by passing the conductor through the protruding current monitor transformer. As a self-generating device, units have no external power supply requirements.  When the monitored current exceeds the trip point for longer than 400 msec, the internal relay energizes (pick-up). When monitored current drops below the trip point for longer than 50 msec, the internal relay de-energizes (drop-out).  The current trip point specified is with one turn through the transformer. Each time the number of turns through the transformer doubles, the trip point effectively halves. Example: CMG-0100-20 will trip at 20 amps with one turn passing through the transformer. By placing two turns through the transformer, the relay will trip at 10 amps. Likewise, four turns will cause the relay to trip at 5 amps.



  • Self-powered AC current monitoring relay
  • No external power requirements for operation
  • No physical connection to monitored AC line needed
  • Automatic reset function
  • Easy installation


  • Current demand level monitoring
  • Conveyor or motor load jam detection
  • Dull bit or blade detection
  • Remote motor sensing
  • Broken fan belt or chains detection
  • Feed rate to keep two loads at their most efficient point