Siemens SIMATIC Operating Instructions Manual page 123

Wiring Diagram for Nonequivalent Connection of Two Single-Channel Sensors to Two Channels
Two single-channel sensors are connected via two channels to two inputs of the F-module
for each process signal (1oo2 evaluation).
The left channels of the F-module (DI 0 through DI 1) return the wanted signals. If no faults
are detected, these signals will be available in the I/O area for inputs on the F-CPU.
The sensors can also be supplied via an external sensor supply.
Figure 8-30
In order to achieve SIL2/Category 3 with this wiring, you must install a suitably qualified
sensor, for example, in accordance with IEC 60947.
Assignable Parameters for Use Case 2.3
Set the "Type of sensor interconnection" parameter to "2-channel nonequivalent" for the
corresponding input.
You can enable or disable the "short-circuit test" parameter. For digital inputs connected to
an external supply, set the "Sensor supply" parameter for the corresponding digital input to
"external". The program will otherwise report a "short circuit" diagnostics event if the "short-
circuit test" is enabled.
ET 200pro Distributed I/O System - Fail-Safe Modules
Operating Instructions, 05/2007, A5E00394073-02
Wiring Diagram for F-Switch - Two One-Channel Sensors Connected Via Two Channels
Nonequivalently, Internal Sensor Supply
WARNING
Fail-Safe Electronic Modules
8.3 F -Switch PROFIsafe Digital Electronic Module
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