Configuration
3/07 UDC3500 Universal Digital Controller Product Manual 79
Function Prompt
Lower Display
Selections or
Range of Setting
Upper Display
Parameter
Definition
PID A
ATTENTION PID A
should not be used for
Proportional only action;
i.e., no integral (reset)
action. Instead, use
PD+MR with rate set to 0.
PID A—This normally used for three-mode control.
Three mode control means that the output can be
adjusted to be at any point between 0 % and 100 %.
It applies all three control actions—Proportional (P),
Integral (I), and Derivative (D)—to the error signal.
Proportional (Gain)
—Regulates the controller’s
output in proportion to the error signal (the difference
between Process Variable and Setpoint).
Integral (Reset
)—Regulates the controller’s output
to the size of the error and the time the error has
existed. (The amount of corrective action depends
on the value of proportional Gain.)
Derivative (Rate)
—Regulates the controller’s output
in proportion to the rate of change of the error. (The
amount of corrective action depends on the value of
proportional Gain.)
PID B
PID B—Unlike the PID A equation, the controller
gives only an integral response to a setpoint change,
with no effect on the output due to the gain or rate
action, and it gives full response to PV changes.
Otherwise controller action is as described for the
PID A equation. See note on PID A.
PD+MR
PD WITH MANUAL RESET—This is used whenever
integral action is not wanted for automatic control
action. The equation is computed with no integral
contribution. The MANUAL RESET value, which is
operator adjustable, is then added to the present
output to form the controller output.
Switching between manual and automatic mode is
bumpless (output does not change value).
If you select PD with Manual Reset you can also
configure the following variations:
• PD (Two Mode) control,
• P (Single Mode) control.
Set Rate (D) to 0.
ATTENTION Other prompts affected: MAN RSET
in the Tuning Set Up group
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