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8 PARAMETER FUNCTIONS
8-50
(5) Adjustment
In Pr. 129, 130 and 134, set the proportional band (P), integral time (I) and differential time (D). First
set the proportional band a little larger, the integral time a little longer, and the differential time a
little shorter. While looking at the system operation, reduce the proportional band, decrease the
integral time, and increase the differential time.
1) PI control
A combination of proportional control action (P) and integral control action (I) for providing a
manipulated variable in response to deviation and changes with time.
[Operation example for stepped changes of process value]
Note: PI action is the sum of P and I actions.
Time
Time
Time
Process value
P action
I action
PI action
Deviation
Set point
2) PD control
A combination of proportional control action (P) and differential control action (D) for providing
a manipulated variable in response to deviation speed to improve the transient characteristic.
[Operation example for proportional changes of process value]
Note: PD action is the sum of P and D actions.
Time
Time
Time
Deviation
PD action
P action
D action
Set point
Process
value
3) PID control
The PI action and PD action are combined to utilize the advantages of both actions for control.
Note: The PID action is the sum of P and I and D actions.