41
2) Long integral time means the controller corrects for offset over a long
time. If the integral time is too long, the offset will remain inactive,
causing slow response or sluggish control.
Temp
Derivative:
Derivative time is the amount of anticipatory action needed to return a
process back to set point. In the case of a process upset, proportional only
or proportional-integral action alone can’t react fast enough in returning a
process back to set point without overshoot. Derivative action corrects for
disturbances, providing sudden shifts in output which opposes the process
disturbance.
Temp
1) A short derivative time means little derivative action. If the derivative is
too short, the controller would not react quickly to process disturbances
and may not attain set point.
2) A long derivative time means more derivative action. If the derivative
time is too large, the controller would react too dramatically to process
disturbances creating rapid process oscillation (alternating heat and
cool continuously).
"I" is too long
TIME
P.V.
S.P.
P.V.
TIME
P.V.
RATE TIME
(RATE)
DERIVATIVE ACTION
S.P.
Summary of Contents for M2B
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