Discrepancy Behavior - Siemens SIMATIC ET 200SP Equipment Manual

4.2.3.2

Discrepancy behavior

Function
For the "Discrepancy behavior", you assign the value that is supplied to the safety program in
the F-CPU during a discrepancy between two relevant input channels, which means while
discrepancy time is running. You assign the discrepancy behavior as follows:
• "Supply last valid value"
• "Supply value 0"
Requirements
You have assigned the following:
• "Sensor evaluation": "1oo2 evaluation, equivalent" or "1oo2 evaluation, non-equivalent"
"Supply last valid value"
The most recent valid value (old value) before the discrepancy occurred is made available to
the safety program in the F-CPU as soon as a discrepancy is detected between the signals of
the two affected input channels. This value is supplied until the discrepancy disappears or the
discrepancy time expires and a discrepancy error is detected. The sensor-actuator response
time is correspondingly increased by this time.
This means the discrepancy time of connected sensors with 1oo2 evaluation must be
adjusted to short response times. It makes no sense, for example, if connected sensors with a
discrepancy time of 500 ms trigger a time-critical shutdown. In the worst possible case, the
sensor-actuator response time is extended by the discrepancy time:
• For this reason, position the sensors in the process in such a way as to minimize
discrepancy.
• Then select the shortest possible discrepancy time which is also sufficient to compensate
for faulty triggering of discrepancy errors.
"Supply value 0"
As soon as a discrepancy between the signals of the two relevant input channels is detected,
the value "0" is made available to the safety program in the F-CPU.
If you have set "Supply value 0", the sensor-actuator response time is not affected by the
discrepancy time.
Digital input module F-DI 8x24VDC HF (6ES7136-6BA01-0CA0)
Equipment Manual, 10/2021, A5E50578307-AA
Parameters/address space
4.2 Explanation of parameters
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