Error type
Identifi‐
cation
Diagnos‐
tics
Loss of
SF
1
Notes
Error in actuator
Even though it was witched off, the
actuator does not go into the safe
state (e.g. not opening a contact)
No
None
No
The safety function is not lost, as the second switch‐
ing element of the dual-channel actuator can be
switched off.
Install an error detection by external monitoring. Im‐
plement a restart inhibit for this error case. Observe
all errors that can occur in the actuator.
Test the switch-off capability of the actuator in rea‐
sonable intervals.
Actuator cannot be switched on
(e.g. interruption)
No
None
No
Install an error detection by external monitoring. Ob‐
serve all errors that can occur in the actuator.
Ensure that this error does not cause a delayed sys‐
tem startup.
More errors (depending on the ac‐
tuator)
Consider all errors that can occur in the actuator.
Error in wiring
Interruption
Interrupting the wire between out‐
put and actuator or between actua‐
tor and ground
No
None
No
Install an error detection by external monitoring. Ob‐
serve all errors that can occur in the actuator.
Ensure that this error does not cause a delayed sys‐
tem startup.
Cross-fault
Output against output
Yes
(limited)
All LEDs
OUT: Red
on
No
Cross-fault between the outputs is only detected if
the outputs are in a switched-off state when the test
pulses are switched on. If an error is detected, the
module disables all its outputs.
If the test pulses are switched off, test the circuit and
the external wiring regularly by switching on the out‐
puts.
Short circuit
Output against ground or output
against FE
Yes
Short cir‐
cuit or
overload,
OUTx
2
No
The error is detected in enabled state. The output is
disabled (safe state). It can only be switched on
again at a rising edge from "0" to "1" after trouble‐
shooting and acknowledgement.
Warning: Unexpected machine startup due to an
"Operator Acknowledgement"
Note that an "Operator Acknowledgement" can
cause the outputs to be switched on again.
1
SF = Safety function
2
OUTx = Diagnostic message (LED) per output X
Tab. 7-4:
Dual-channel
DOK-CONTRL-S20*SSDO*8*-AP02-EN-P
Bosch Rexroth AG
39/85
IndraControl S20 Module With Safe Digital Outputs S20-SSDO-8/3
Connection examples of the safe outputs