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 relia‐
bility of the safety function.
NOTE
Monitoring of the series-connected contactors is necessary in order to realize category
4 in accordance with ISO 13849-1.
The external device monitoring (EDM) monitors the status of downstream contactors.
Requirements
Positively guided contactors are used for shutting down the machine.
If the auxiliary contacts of the positively guided contactors are connected to the exter‐
nal device monitoring, the external device monitoring checks whether the contactors
drop out when the safety outputs (relay outputs) are switched off.
Operating principle
If you teach in external device monitoring, the T4000 Multi transponder safety switch
checks the contactors each time the safety outputs are switched off and before the
machine restarts. External device monitoring is then able to detect if one of the contac‐
tor’s contacts is welded, for instance. In this case, the safety outputs remain in the OFF
state.
24 V DC
k2
k1
K1
K2
0 V DC
A
EDM
B
1RCA02/04
Figure 2: Electrical diagram of external device monitoring (EDM)
You must implement external device monitoring electrically so that the two N/C con‐
tacts (k1, k2) close in a positively guided manner when the contactors (K1, K2) reach
their de-energized position once the protective device has responded. 24 V is then
present at the input of external device monitoring. If 24 V is not present when the pro‐
tective device has responded, one of the contactors is defective and external device
monitoring prevents the machine from restarting.
4
PROJECT PLANNING
16
O P E R A T I N G I N S T R U C T I O N S | T4000 Multi
8022726/2019-05-07 | SICK
Subject to change without notice
