External device monitoring (EDM) monitors the status of downstream contactors.
Prerequisites
•
P
ositively guided contactors are used for shutting down the machine.
If the auxiliary contacts of the positively guided contactors are connected to the
e
xternal device monitoring, the external device monitoring checks whether the
contactors drop off when the OSSDs are switched off.
Principle of operation
If you configure external device monitoring, the safety light curtain then checks the
contactors after every interruption to the light path and before the machine restarts.
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
K2
0 V DC
OSSD 1
EDM
OSSD 2
r
Figure 28: Electrical diagram of external device monitoring (EDM)
Y
ou must implement external device monitoring electrically so that the two N/Cs (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 are then present
at the input of external device monitoring. If 24 V are not present once the protective
device has responded, one of the contactors is defective and external device monitor‐
ing prevents the machine from restarting.
4.4.3 Application diagnostic output
The safety light curtain has an application diagnostic output on the system connection
and on t
he extension connection.
Depending on the configuration, the application diagnostic output signals a certain
status of the safety light curtain, e.g. if the reset pushbutton must be engaged or if
there is a weak signal at the receiver.
For a signal of the safety light curtain to be displayed, a light can be connected to
the application diagnostic output or the signal can be transmitted to the machine
controller.
Figure 29: Electrical diagram of the application diagnostic output
Further topics
•
"C
onfiguring application diagnostic output", page 97
4 P
ROJECT PLANNING
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O P E R A T I N G I N S T R U C T I O N S | deTec4 Ex II 3GD 8023872/18YZ/2021-01-14 | SICK
Subject to change without notice
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