Parameters/address space
4.3 Explanation of parameters
Analog input module F-AI 4xI 0(4)..20mA 2-/4-wire HF (6ES7136-6AA00-0CA1)
28
Manual, 08/2018, A5E41448857-AB
If the process value does not represent the standard value at an instant but is outside the
tolerance window, a discrepancy exists.
Figure 4-2
Example of a relative tolerance window
with
discrepancy (parameter assignment:
standard value = MAX)
The assigned discrepancy time starts as soon as a discrepancy is detected. The discrepancy
time runs as long as the discrepancy exists.
●
During a discrepancy between the two input channels, the last valid standard value prior
to occurrence of the discrepancy is signaled to the F-CPU.
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.
●
There is no valid old value after startup. If the discrepancy is detected during this time,
7FFF
H
is output for S7-300/400 F-CPUs or 0 is output for S7-1200/1500 F-CPUs and the
discrepancy time is started.
If there is no longer a discrepancy between the input channels when the discrepancy time
expires, the standard value is output.
If the discrepancy time has expired, an error is signaled and the process value is set to
7FFF
H
for S7-300/400 F-CPUs or 0 for S7-1200/1500 F-CPUs. In the PII, the substitute
value 0 is set for the safety program.
A discrepancy error is handled by the safety program in the same way as a channel fault.
Additional information is available in the STEP 7 Safety – Configuring and Programming
http://support.automation.siemens.com/WW/view/en/54110126
) manual
.
