Siemens SIRIUS 3RK3 - Guidelines for Wiring the MSS 3 RK3

5.3.2.2 Guidelines for wiring the MSS 3RK3
Cross-circuit detection
Cross-circuit detection enables detection of an inadmissible connection between a sensor cable
and another sensor cable (= cross-circuit), a ground cable (= short circuit to ground) or a power
supply cable (= short circuit to P). The test outputs are available for this purpose.
Cross-circuit detection
To ensure reliable cross-circuit detection, note the following points when wiring the individual
devices:
1. All components, that is, all devices including the sensors, must be operated on the same
power supply.
2. Cross-circuit detection is not possible with single-channel sensors. Exception: Single-
channel acknowledgment button
3. A two-channel sensor must only be connected to a single (expansion) module.
4. A two-channel sensor must be connected to test outputs T1/T2 to ensure cross-circuit
detection.
If a cross-circuit is detected, this applies to the entire module.
5. Test output T1 must always be combined with an odd-numbered sensor input (IN1, IN3, IN5,
IN7).
6. Test output T2 must always be combined with an even-numbered sensor input (IN2, IN4, IN6,
IN8).
7. Non-󹪞oating sensors cannot be connected to test outputs T1/T2. Cross-circuit detection of
non-󹪞oating sensors with a safety relay is therefore not possible. These sensors must be able
to monitor and evaluate themselves and also the cable to the evaluation unit to ensure the
safety of the application. In this case, cross-circuit detection must be deactivated in the
Safety ES software.
8. Cross-circuit detection between three, four, or more inputs on one sensor is not possible. For
this reason, the cables for the two buttons must be routed separately to prevent a cross-
circuit (in two-hand operation, for example).
9. If a safety shutdown mat (cross-circuit principle) is connected to a device, cross-circuit
detection must be deactivated for the remaining inputs on this device because otherwise the
monitoring functions con󹪝gured for these inputs will also signal a cross-circuit when
somebody steps on the safety shutdown mat.
10.Since a cross-circuit is a fault that requires acknowledgment, a cross-circuit that has been
recti󹪝ed must be acknowledged by resetting.
Wiring sensors
Chapters "Connecting safety-related inputs (Page 138)" and "Connecting non-safety-related
inputs (Page 139)" describe how to connect the sensors to the safety relay.
Description of the hardware
5.3 Connecting / wiring
SIRIUS 3RK3 Modular Safety System
136 Equipment Manual, 07/2020, NEB926253002000/RS-AC/006