EDM Switch-OFF Timer Elapsed

What does FB EDM Bit 0 mean?

The switch-OFF timer for the EDM (External Device Monitoring) function block has elapsed. This means that the feedback signal from the monitored device (e.g., safety contactor) did not transition to its expected OFF state within the configured time after the EDM output commanded it. This indicates a delay or failure in the monitored device's deactivation, posing a safety risk if the device fails to open.

• External Device Monitoring (EDM) switch-off timer expired.
• Safety contactor feedback signal not received within the allowed time.
• Interrupted connection to the EDM monitoring circuit.
• EDM monitoring device has failed.
• Safety relay failed to open the circuit.

Click steps to track your progress.

1. 1

   Verify the wiring of the feedback loop from the monitored device (e.g., NC contact of a safety contactor) to the EDM input; check for opens or shorts.

2. 2

   Check the mechanical and electrical functionality of the monitored device; ensure it de-energizes and its contacts open promptly and reliably.

3. 3

   Measure the actual switching time of the monitored device using a multimeter or oscilloscope to compare with configured parameters.

4. 4

   Review and potentially adjust the 'tSwitchOff' parameter in the FB EDM configuration if the device's inherent switching time is legitimately longer than configured.