Series Connection Of Sensors - Siemens SIRIUS 3SK1 Equipment Manual

More detailed technical information is available in the "SIRIUS 3RM1 motor starters
support.automation.siemens.com/WW/view/en/66295730)" manual on the Internet.
4.3.14

Series connection of sensors

Series connection of EMERGENCY STOP command devices
It is possible to connect EMERGENCY STOP command elements in series up to the highest safety
level level (SILCL 3 in accordance with IEC 62061, SIL 3 in accordance with IEC 61508 and PL e
(Cat. 4) in accordance with ISO 13849-1) because it is assumed that only one EMERGENCY STOP
is operated at a time. This ensures that errors and defects can be detected.
Series connection of mechanical position switches
In general, position switches may be connected in series if measures ensure that several
protective doors are not regularly opened simultaneously (otherwise a fault cannot be detected).
For safety level level SILCL3 in accordance with IEC 62061, SIL3 in accordance with IEC 61508,
and PL e (Cat. 4) in accordance with ISO 13849-1, however, they must never be connected in
series because every hazardous error must be detected (independently of the operating
personnel).
SIRIUS 3SK1 Safety Relays and 3RQ1 Positively-Driven Coupling Relays
Equipment Manual, 05/2021, A5E02526190021A/RS-AE/005
Safety systems - General information
4.3 Basic terminology
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