Process Control Instructions
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018 99
CV Rate-of-Change Limiting
The PIDE instruction limits the rate-of-change of CV when in Auto or
Cascade/Ratio mode or when in Manual mode and CVManLimiting is set. A
value of zero disables CV rate-of-change limiting.
The CV rate-of-change is calculated as:
where DeltaT is in seconds.
Once CV rate-of-change has been calculated, the CV rate-of-change alarms are
determined as follows:
(1) During instruction first scan, the instruction clears the alarm output. The
instruction also clears the alarm output and disables the CV rate-of-change
algorithm when CVInitializing is set.
(2) When in Auto or Cascade/Ratio mode or when in Manual mode and
CVManLimiting is set, the instruction limits the change of CV.
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