Siemens SIMATIC PCS 7 Operating Manual page 52

Configuring S7F/FH hardware
6.4 Setting system parameters for F-signal modules
Short-circuit test
You can use this parameter to activate short-circuit detection for the F signal module.
The short-circuit test can only be activated for sensors that are supplied by the F signal
module.
Short-circuit detection disconnects the sensor supply briefly and tests the input signal. In so
doing, a cross circuit is detected between the channels and an "L+" fault at the active inputs.
Whenever a short-circuit is detected, the F signal module will trigger a diagnostics interrupt
on the CPU and send a corresponding process control message to the OS.
Sensor evaluation
● 1oo1 (1v1) evaluation
A sensor connected to the F signal module via a single channel.
● 1oo2 (2v2) evaluation
For a process signal one or two sensors are connected to two opposite inputs of an F
signal module. The signal states of inputs (equivalence or non-equivalence) are
compared internally.
The following safety classes can be achieved:
● 1-channel – SIL 2; in the case of multiple channels, SIL 3 can be achieved by means of
voting in the CPU.
● 2-channel – SIL 3 (voting on module)
Type of sensor interconnection
If "1oo2 sensor evaluation" is selected, you can select the type of sensor interconnection for
each input channel (exception: SM 326; DI 8 x NAMUR, for which this parameter does not
exist. For this module, only 2-channel equivalent sensor interconnection can generally be
selected where "1oo2 evaluation" is concerned.):
● "2-channel equivalent"
A two-channel sensor or two single-channel sensors (2-channel connection) is/are
connected to two opposite input channels
● "2-channel non-equivalent"
One non-equivalent sensor or two single-channel, non-equivalent sensors (2-channel
connection) is/are connected to two opposite input channels
● "1-channel"
A sensor (1-channel) is connected to two opposite inputs.
Note
If you are using the "2-channel non-equivalent" or "1-channel" type of sensor
interconnection, and the internal sensor supply and the short-circuit test are
parameterized, the Vss supply voltage from the left-hand side of the F signal module
must be used.
52
Compendium Part B - Process Safety (V8.2)
Operating Manual, 07/2016, A5E35031794-AB