Safety sensors with serial diagnostic cable have a serial input and output instead of the conventional diagnostic output.
If RSS / CSS safety sensors are wired in series, the safety channels as well as the inputs and outputs of the diagnostic
channels are wired in series.
Up to 31 safety switchgear devices can be connected in series with serial diagnostics. For the evaluation of the serial
diagnostics line either the PROFIBUS-Gateway SD-I-DP-V0-2 or the Universal-Gateway SD-I-U-… are used. This SD-
Gateway is integrated as a slave in an existing field bus system. In this way, the diagnostic signals can be evaluated by
means of a PLC. The necessary software for the integration of the SD-Gateway is available for download at
products.schmersal.com.
The response data and the diagnostic data are automatically and permanently written in the assigned input byte of the
PLC for each safety sensor in the series-wired chain.
The request data for each safety sensor are transmitted to the device through an output byte of the PLC.
In the event of a communication error between the SD-Gateway and the safety sensor, the switching condition of the
safety output of the safety sensor is maintained.
Bit 0: safety outputs enabled
Bit 1: safety sensor actuated, actuator identified
Bit 4: both safety inputs live
Bit 5: safety sensor actuated in hysteresis area
Bit 6: error warning, switch-off delay activated
Bit 7: error, safety outputs switched off
Error
Errors which no longer guarantee the function of the safety switchgear (internal errors) cause the safety outputs to be
disabled within the duration of risk. The fault is reset, when the cause is eliminated and bit 7 of the request byte
changes from 1 to 0 or the safety guard is opened. Faults at the safety outputs are only deleted upon the next release,
as the fault rectification cannot be detected sooner.
Error warning
A fault that does not immediately endanger the safety function of the safety switchgear (e.g. too high ambient
temperature, safety output at external potential, cross-circuit) leads to delayed shutdown. This signal combination,
diagnostic output disabled and safety channels still enabled, can be used to stop the production process in a controlled
manner.
An error warning is deleted when the cause of error is eliminated.
If the fault warning remains on for 30 minutes, the safety outputs are also switched off (red LED flashes).
Diagnostic error (warning)
If an error (warning) is signalled in the response byte, detailed fault information can be read out.
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