SICK safeVisionary2 - Control Inputs; Dual-Channel and Isolated Connection of an OSSD Pair; No Potential Difference between Load and Protective Device

Prerequisites
•
T
he machine switches to the safe state if, at any time, at least one OSSD in an
OSSD pair switches to the OFF state.
•
When using a safety controller: The safety controller detects different signal levels
of the two OSSDs of an OSSD pair (depending on national regulations or required
reliability of the safety function). The maximum discrepancy time tolerated by the
control is selected according to the application.
•
The output signals from an OSSD pair are not connected to each other.
•
The machine controller processes both signals of an OSSD pair separately.
OSSD A OSSD B OSSD A OSSD B
Figure 25: Dual-channel and isolated connection of an OSSD pair
•
N
o potential difference can occur between the load and the protective device. The
0V connections of the load and those of the associated protective device are
connected 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 protec‐
tive device. This is particularly important for loads that switch even if they are
activated with negative voltage (e.g. electromechanical contactor without reverse
polarity protection diode).
OSSD A OSSD B OSSD A OSSD B
Figure 26: No potential difference between load and protective device
Further topics
•
"C
ourse of the OSSD test over time", page 94
4.4.4 Control inputs
Overview
T
he control inputs accept signals for switching between different monitoring cases.
Static control inputs are used for information about machine status.
PROJECT PLANNING 4
8025919/1I9E/2023-01-09 | SICK O P E R A T I N G I N S T R U C T I O N S | safeVisionary2
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Subject to change without notice