In this post, we focuss on tuning of the pH loop because this case was rather typical for what process technologists experience in practice, and where the PID Tuner is used in off-line mode.
Figure 1: User interface for tuning the pH loop (PID parameters)
Figure 2: Closed loop response to setpoint change, with original PID settings (XP = 25%, TI = 30 s).
Figure 3: Simulated and measured MV (= PID output). Kp Scaling is computed by the PID Tuner so that it fits the measured MV best (which turned out to be Kp Scaling = 10)
Figure 4: Measured PV (=pH value) and simulated PV.
Figure 5: Measured closed loop response and simulated closed response. Here, we simulate both the PID and the pH model, using the setpoint as the only model input. Hence, the model also simulated the MV response
Figure 6: Measured closed loop response and simulated closed response after retuning of the PID with XP = 2.5, TI = 240s (as obtained from the PID Tuner).