52
SC-F70
SC-F70
PID Operation Operating Instructions
3.6 PID Constants Fine-Tuning Method
Determining the best PID constant values needs numerous trials. This
section summarizes the relationship between the PID constants and
control responsiveness. Use the following information to obtain fine-
turned PID constants.
1) Effect of Proportional Band (P)
If you decrease only the P value, responsiveness is affected as
follows:
1. The offset amount decreases when the integral time is set to 0
seconds.
2. The first peak fluctuation of the measured value after controlling
caused by external disturbance decreases.
3. The measured value oscillates more. The oscillation damping
ratio becomes smaller and the measured value finally diverges.
4. The oscillation cycles shorten.
2) Effect of Integral Time (I)
When you decrease only the I value, responsiveness is affected as
follows:
1. The offset amount can be decreased to zero.
2. The first peak fluctuation of the measured value after controlling
caused by external disturbance decreases.
3. Overshooting becomes larger when the target setting is changed.
4. The measured value oscillates more. The oscillation damping
ratio becomes smaller, and the measured value finally diverges.
5. The time the deviated value takes to return to the target value
becomes shorter.
3) Effect of Differential Time (D)
When you decrease only the D value, responsiveness is affected as
follows:
1. The first peak fluctuation of the measured value after controlling
caused by external disturbance decreases.
2. Oscillation becomes suppressed. The oscillation damping ratio
increases, but it decreases again if the D value is increased too
much.
3. The oscillation cycles shorten.
