Since I last checked in, John has added two more tips: The Tricky Transmitter, and The Process that Changes its Mind.
The tricky transmitter tip deals with the case where you might perform transmitter zero and span calibration (or re-ranging.) The operators may notice a change in the loop performance which changes the gain in the transmitter. John shows the math and the corrective action to take (changing the controller gain for those of you who don’t follow hyperlinks J. )
In the process that changes its mind, John discusses the case where loops behave differently at different times, going between stable and unstable operation. Most processes have changing process gains. Adjustments to controller gain can be done manually (for very slow changing processes) or through adaptive gain control strategies.
As software continues to get more sophisticated, it can help monitor control performance in each of the loops. By identifying and diagnosing problem loops, recommending tuning and maintenance improvements and continuously adapting to these changing process conditions the effects of nonlinear gain can be mitigated. DeltaV InSight is an example of this type of control performance software.
I need to work with the team to figure out how we can get an RSS feed of these great tips so that anyone interested in keeping up with these tips can subscribe to John’s excellent work. There I go again harping about RSS!