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Symptom:
Are
your tank levels not performing as desired? Are you unable to predict the
time required for the level to return to setpoint?
Probable cause:
Controller
tuning is probably not set with the best gain and reset to achieve your
objectives.
Corrective action: The controller tuning is based on the open
loop response test results. (See Loop Tip #13).
This test will determine the process gain in terms of ______ /time.
The calculations shown
here are based on conservative tuning.
Controller gain = 2 (or 50% proportional band)
 Controller
reset =
2 = _______ time/repeat
Process gain
Settling time
= 6 = ________ time
Process gain
The settling is the
time required for the process variable to return to setpoint. There will
probably be some minor overshoot of PV past SP, but this should not be
significant. If a shorter settling time is desired, more aggressive tuning
of gain and reset can be used.
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