MANUAL TUNING FOR PID CONTROL
In some unusual cases, the Auto-Tune function may not yield acceptable control results. In this case, the controller can be manually tuned to optimize the PID setting according to the process and the desired control requirements.
Manual Tuning Procedure
A chart recorder or data logging device is necessary to measure the time between process cycles.
1. Set the Proportional Band (ProP) from the Unprotected Parameter Mode to
10.0% for T48 models and 100.0% for P48 models.
2. Set the Integral Time (Intt) and Derivative Time (dErt) to 0 seconds.
3. Set Output Power Dampening Time (OPdP) in Output Parameter Module
(2-OP) to 0 seconds.
4. Set Output Cycle Time (CYCt) in Output Parameter Module (2-OP) to no higher than 1/10 of the process time constant (when applicable).
5. Place controller in Manual Control and set % Power from the Normal
Display Mode to drive the process value to the desired value. Make certain that the controller can drive the process to the setpoint. Allow the process to stabilize after setting the % Power.
6. Place controller into Automatic Control. If the process will not stabilize and starts to oscillate, set the Proportional Band 2x higher and go back to step 5.
7. If the process is stable, decrease Proportional Band setting by 2x and change the setpoint value a small amount to excite the process. Continue with this step until the process oscillates in a continuous nature.
8. Fix the Proportional Band to 3x the setting that just caused the oscillations.
9. Set the Integral Time to 2x the period of the oscillations.
10. Set the Derivative Time to 1/8 (0.125) the Integral Time.
11. Set Output Power Dampening Time to 1/40 (0.025) the period of the oscillation.
Note: This procedure is an alternate to the controller’s Auto-tune function. It will not provide acceptable results if system problems exist.
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