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does not have this function, it must be implemented in the external control if
required.
•
When using a safety controller, different signal levels of both OSSDs must be
detected depending on applicable national regulations or required reliability of the
safety function. The maximum discrepancy time tolerated by the control must be
selected according to the application.
•
The OSSD1 and OSSD2 output signals must not be connected to each other.
•
In the machine controller, the signals of both OSSDs must be processed sepa‐
rately.
Figure 14: Dual-channel and isolated connection of OSSD1 and OSSD2
•
The 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 (safety 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 15: No potential difference between load and protective device
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PROJECT PLANNING
22
O P E R A T I N G I N S T R U C T I O N S | C4-RD
8025644/19Z2/2021-03-09 | SICK
Subject to change without notice