Parameters/address space
4.3 Explanation of parameters
Analog input module F-AI 4xI 0(4)..20mA 2-/4-wire HF (6ES7136-6AA00-0CA1)
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Manual, 08/2018, A5E41448857-AB
4.3.2.3
Standard value
Function
If you have selected "1oo2 evaluation (max. SIL3/Cat.4/PLe)", you can choose for each input
channel pair which of the two F-CPU values is provided.
●
"MIN": the lesser of the two values.
●
"MAX": the greater of the two values.
During a discrepancy between the two input channels, the last valid standard value prior to
the occurrence of the discrepancy is made available to the F-CPU.
4.3.2.4
Discrepancy time
Function
If you have selected "1oo2 evaluation (max. SIL3/Cat.4/PLe)", you can enter the discrepancy
time for each channel pair here in milliseconds.
The discrepancy time does not start until the standard value is outside the assigned
tolerance window (relative or absolute). If the two redundant input channels of the channel
pair differ by more than the specified tolerance and for longer than the specified discrepancy
time but no longer than the duration of the maximum response time, the F-module detects a
discrepancy error and triggers a diagnostic interrupt. If the input channels fall below the
specified tolerance prior to expiration of the discrepancy time (input channels are no longer
discrepant), the discrepancy time is cleared and is restarted only when a new discrepancy is
detected.
You can find additional information about configuring the discrepancy analysis under
Parameter assignment of discrepancy analysis for 1oo2 evaluation (Page 27).
A discrepancy error is handled by the safety program in the same way as a channel fault.
Additional information is available in the SIMATIC Safety – Configuring and Programming
http://support.automation.siemens.com/WW/view/en/54110126
) manual.
