Siemens SIRIUS 3RK3 - Dark Test

6.2.2.1 Dark test
Dark test
The dark test is the brief deactivation of an activated safety-related output of the MSS 3RK3 to
ensure that the output can be deactivated at any time in the event of a safety requirement. To
this end, the chosen test pulse is so short that a connected actuator does not shut down as a
result. The dark test is repeated cyclically
Maximum read-back time of the dark test
The maximum read-back time of the dark test determines its maximum duration. The restart
standby time is also determined by the maximum read-back time. An output must not be
reactivated until it has been detected as having been deactivated.
Maximum read-back time
The maximum read-back time is di󹪜erent on di󹪜erent devices:
Device Maximum read-back time
MSS 3RK3 central units 1 ms
2/4 F-DI 2F-DO expansion module 1 ms
4F-DO expansion module 5 ms
Operation
6.2 Selection of sensors and actuators
SIRIUS 3RK3 Modular Safety System
Equipment Manual, 07/2020, NEB926253002000/RS-AC/006 189