Tuesday, October 6, 2009

A New Look At PID Loops

My latest at ECN Magazine.


kurt9 said...

You ever used Eurotherm's 818 loop controllers?

I've used them in semiconductor applications where I needed temperature control of 0.1degC resolution.

Yokogawa's "green" series are a nice cheap loop controller as well. They're not as accurate as Eurotherm's but are very cheap and easy to interface them with your PLC or control PC.

M. Simon said...


No. As I recall though most temp. controllers are based on the Gain/Time factors the chemical folks use.

kurt9 said...

Yes, they are. Nonetheless, they work quite well once they are properly tuned.

M. Simon said...

Kurt. I think that was my point. That Gain/Time tuning is more physical.

When I dis my original work on auto-tuning I looked at a number of temp. controllers in order to get a handle on the algorithms they used. Not much help.

What I found the most useful was a book on control theory from one of the engineering societies which had a number of fundamental papers including Ziegler-Nichols and some of the initial papers on "shock" tuning. I wish I could remember which society. Might have been the Society Of Chemical Engineers.