4.5.8
External device monitoring (EDM)
Overview
The external switching elements (external device monitoring, EDM) must be inspected
in line with the regulations which apply at the place of installation or the required
reliability of the safety function.
External device monitoring (EDM) monitors the status of downstream contactors.
Prerequisites
•
Positively guided contactors are used for shutting down the machine.
Functionality
If you configure external device monitoring, then the safety laser scanner checks the
contactors before each time an OSSD pair is switched on. External device monitoring
is then able to detect if one of the contactor’s contacts is welded, for instance. In this
case, the OSSDs remain in the OFF state.
24 V DC
k2
k1
K1
0 V DC
OSSD A
EDM
OSSD B
K2
Figure 33: Electrical diagram of external device monitoring (EDM)
When the contactors (K1, K2) reach their rest position after the protective device has
tripped, the two N/C contacts (k1, k2) close in a positively guided manner. 24 V is
then present at the input of external device monitoring. If 24 V is not present before
the OSSD pair is switched on, then one of the contactors is faulty and external device
monitoring is preventing the OSSD pair from switching to the ON state.
In addition, external device monitoring checks the contactors after the OSSD pair
is switched on. If both N/C contacts (k1, k2) remain closed after the OSSD pair is
switched on, the OSSD pair switches back to the OFF state.
Complementary information
Each OSSD pair in the safety laser scanner is equipped with a configurable internal
EDM.
4.5.9
Connection diagrams
Restart interlock and external device monitoring (EDM)
The safety laser scanner can be connected directly to relays/contactors. It is operated
with restart interlock and external device monitoring.
PROJECT PLANNING
4
8023152/1G5N/2022-06-28 | SICK
O P E R A T I N G I N S T R U C T I O N S | outdoorScan3 Core I/O
55
Subject to change without notice