This helped me understand PID better

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Joined Oct 3, 2010
I've been tuning PID for various industrial applications (mostly heat controllers, VFD speed loops, etc) for years now and had the minimum practical level of understanding of what was actually going on such that I could accomplish the task (even if it took a while). But it always seemed a bit nebulous. Some big algorithm I didn't understand was at the root of it. I never saw it explained in terms of something intuitive. That changed last night as I was lying awake cooking my brains with ideas of a DIY proportional valve that could control a pneumatic cylinder with near-servo-actuator accuracy using a PID loop. Googling some combination of words from that last sentence landed me on this video of a pneumatic (no electronics, no electricity!) PID controller from 1943.

This took me on a tangential quest to understand how that worked, and I happened upon these videos:

Now I have finally seen PID explained in terms of something tangible, intuitive (air pressure). Next time I tune PID I will come back to this for a refresher and see if it helps me to tune more effectively. Already it improved my understanding, and if it helped me, I figure it might help some of you too.
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Joined Jun 7, 2009
Flash from the past. North American hydraulic valves incorporated a hydraulic nozzle as the ‘flapper’, which in our case , drove mixing valves for swirl jet burner nozzles and furnace stack damper. Gas and air were the pneumatics for the controller side. Each burner was tuned to maintain a specific flame profile while overall furnace pressure maintained by the stack.