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Integral Time is the speed at which the controller corrects for offset. A
short integral time means the controller corrects for offset quickly. If the
integral time is too short, the controller would react before the effects
of previous output shifts– due to lead time or lagtime, could be sensed,
causing oscillation. A long Integral time means the control corrects for
offset over a long time. If the integral time is too long, the offset will
remain for some time causing slow responding or sluggish control. See
the diagram below.
Derivative Time
In the case of a process upset, proportional only or proportional-inte-
gral action cannot react fast enough in returning a process back to set-
point without overshoot. The derivative action corrects for disturbances
providing sudden shifts in output which oppose the divergence of the
process from setpoint. See the diagram below.
Setpoint
Output
PV
Offset
Time
Short Integral Time
Long Integral Time
Time
Proportional Action Only
