3.8Determining PID Constants (AT, ST, manual setup)
E5GN
3–17
• When P (proportional band) is adjusted
When P is
increased
Set
Value
The curve rises gradually, and a long
stable time is achieved, preventing
overshoot.
When P is
decreased
Set
Value
Overshoot and hunting occur, how-
ever the set point is quickly reached
after which the curve stabilizes.
• When I (integral time) is adjusted
When I is
increased
Set
Value
It takes a long time for the process
value to reach the set point. It takes
time to achieve a stable state, how-
ever there is little overshoot/under-
shoot and hunting.
When I is
decreased
Set
Value
Overshoot/undershoot and hunting
occur, and the curve rises quickly.
• When D (derivative time) is adjusted
When D is
increased
Set
Value
Overshoot/undershoot and stable
time are reduced, however, fine hunt-
ing occurs on changes in the curve
itself.
When D is
decreased
Set
Value
Overshoot/undershoot increase, and
it takes time for the process value to
reach the set point.
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