Omron EJ1G User Manual page 91

Setting Control Specifications
70
• Integral action:
tional to the time integral of the control error. An off-
set normally occurs in proportional control, so
proportional action is used in combination with inte-
gral action. As time passes, this offset disappears
and the control temperature (process value) matches
the set point.
• Derivative action:
tional to the rate of change of the input. Since propor-
tional control and integral control correct for errors in
the control result, the control system will be slow to
respond to sudden changes in temperature. The
derivative action performs a corrective action by
increasing the MV in proportion to the slope of the
temperature change.
• Effect of Changes to P (Proportional Band)
Increased P
Decreased P
• Effect of Changes to I (Integral Time)
Increased I
Decreased I
• Effect of Changes to D (Derivative Time)
Increased D
Decreased D
This control action produces an output that is propor-
This control action produces an output that is propor-
The curve rises gradually and the
settling time is long, but overshooting
is prevented.
Overshooting and hunting occur, but
the set point is reached quickly and
the temperature stabilizes.
It takes a long time for the process
value to reach the set point. It takes
time to achieve a stable state, but
overshooting, undershooting, and
hunting are reduced.
Overshooting and undershooting
occur. Hunting occurs. The process
value rises quickly.
Overshooting, undershooting, and
the settling time are reduced, but fine
hunting occurs on the changes them-
selves.
Overshooting and undershooting are
increased and it takes time for the
process value to reach the set point.
Section 5-3