At the start of a recent Practical Process Control workshop, I asked the attendees what the “D” in PID stood for. One fellow immediately shouted from the back of the room, “Disaster?” Another piped in, “How about Danger?” When the laughter died down, another emphatically stated, “D is for Do not use.” This one got a good laugh out of me. I had not heard it before and thought it was perfect. And here’s why…

Benefits and Drawbacks
Derivative action has its largest influence when the measured process variable (PV) is changing rapidly (when the slope of