Figure 18: Dual-channel and isolated connection of OSSD1 and OSSD2
•
T
he machine must switch to the safe state at any time if at least one of the two
OSSDs switches to the OFF state
•
Prevent the formation of a potential difference between the load and the protec‐
tive device. If you connect loads to the OSSDs (switch outputs) that then also
switch if controlled with negative voltage (e.g., electro-mechanical contactor with‐
out reverse polarity protection diode), you must connect the 0 V connections of
these loads and those of the corresponding protective device individually and
directly to the same 0 V terminal strip. In the event of a fault, this is the only way to
ensure that there can be no potential difference between the 0 V connections of
the loads and those of the corresponding protective device.
Figure 19: No potential difference between load and protective device
DANGER
H
azard due to lack of effectiveness of the protective device
In the case of non-compliance, it is possible that the dangerous state of the machine
may not be stopped or not stopped in a timely manner.
Downstream contactors must be positively guided and monitored depending on appli‐
cable national regulations or required reliability of the safety function.
b
Make sure that downstream contactors are monitored (external device monitoring,
EDM).
PROJECT PLANNING 4
8027140/2021-11-04 | SICK O P E R A T I N G I N S T R U C T I O N S | deTec4
31
Subject to change without notice
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