External Device Monitoring (EDM)
External device monitoring functionality is used to ensure that external contactors controlled by the safety module outputs are able to interrupt the safety circuit. This functionality is implemented by adding the external contactor feedback to the start condition of the safety module.
The external contactor must provide a feedback through a normally closed auxiliary contact forcibly guided by its normally open safety contact. The start condition is valid only when the external feedback (normally closed) is closed.
External device monitoring can be performed on:
o1 channel.
External feedback is provided to the start condition.
o2 channels for short circuit detection.
External feedback is provided to the start condition and to the S4 input.
NOTE: The state of the external device is only monitored when the safety module is analyzing the start condition validity. When outputs are activated, the external device is not monitored.
EDM Configuration With One Channel
This figure shows an example of 1 channel EDM with the external feedback (K3 and K4) added to the start condition, and S41 directly connected to S42:
K3 External contactor with a normally closed feedback and normally open safety contact
K4 External contactor with a normally closed feedback and normally open safety contact
S2 Start switch
(1) Safety outputs
EDM Configuration With Two Channels
This figure shows an example of 2 channels EDM with one external feedback added to the start condition (K3), and the other feedback (K4) connected to S41 and S42:
K3 External contactor with a normally closed feedback and normally open safety contact
K4 External contactor with a normally closed feedback and normally open safety contact
S2 Start switch
(1) Safety outputs
