BECKHOFF TwinSAFE - Manual (Page 87)

Circuit examples
Application Guide TwinSAFE 85
2.14 Light curtain (Category 4, PL e)
The light curtain has two OSSD outputs (Output-Signal-Switching-Device), which are wired to safe inputs
of an EL1904. The testing of the inputs is not active, since the OSSD outputs carry out their own test.
Furthermore, the signals are checked for discrepancy (200 ms). The feedback loop is read via a safe
input. Testing is active for this input. The contactors K1 and K2 are connected in parallel to the safe
output. Current measurement and testing of the output are active for this circuit.
Logical connection in
the EL6900
K1 K2
K1
K2
OSSD 1
OSSD 2
2.14.1 Parameters of the safe input and output terminals
EL1904
Parameter Value
Sensor test channel 1 active No
Sensor test channel 2 active No
Sensor test channel 3 active Yes
Sensor test channel 4 active Yes
Logic channel 1 and 2 OSSD asynchronous analysis
Logic channel 3 and 4 Single Logic
EL2904
Parameter Value
Current measurement active Yes
Output test pulses active Yes