Siemens SIRIUS 3RK3 - Cross-Circuit Detection; Enabling Circuit



4
6
① Mechanical position switches
② Safety relay
Figure 3-4 Single-channel safety-related control system


44
6
6
①Mechanical position switches
②Safety relay
Figure 3-5 Two-channel safety-related control system
3.7.3.2 Cross-circuit detection
Cross-circuit detection is a diagnostic function of a safety relay that detects short circuits and
cross-circuits between the input channels (sensor circuits) during two-channel detecting or
reading. A cross-circuit can be caused, for example, by a cable casing being squashed. In devices
without cross-circuit detection, this can mean that a two-channel emergency stop circuit does
not trip even though only one NC contact is faulty (secondary error).
With the safety relays, a cross-circuit is detected in the sensor circuits by means of signals with
di󹪜erent clock pulses. If the clocked signals overlap, the device detects a cross-circuit. With safety
relays, cross-circuit detection can be deactivated to enable evaluation of electronic sensors (that
monitor themselves as well as the cable to the evaluation unit).
3.7.3.3 Enabling circuit
An enabling circuit provides a safety-related output signal. From an external viewpoint, enabling
circuits usually act as NO contacts.
An individual enabling circuit with two channels that is con󹪝gured accordingly in the safety relay
can be used for applications up to SILCL 3 / PL e / Kat. 4.
Overview
3.7 Safety systems - General information
SIRIUS 3RK3 Modular Safety System
52 Equipment Manual, 07/2020, NEB926253002000/RS-AC/006