Re: [foxboro] pH control
- From: "Gillis, Dale" <Dale.Gillis@xxxxxxxxxxxxxxx>
- To: "'foxboro@xxxxxxxxxxxxx'" <foxboro@xxxxxxxxxxxxx>
- Date: Mon, 15 Mar 2010 11:07:53 -0500
"We made the loop as "feed forward" as possible. Instead of adding base to
control the pH, we add the chemical based on a ratio of chemical flow to the
water flow. The pH loop determines the ratio. The flow control loop is tuned
to give near a immediate response. The chemical flow is very small and this
part of the loop is now quite successful. It is not a perfect solution, but it
solved the problem of response time to rapid flow changes in the main stream."
I would implement the above like "Chuck" did and maybe make the PIDA a
non-linear controller with a high gain once you get out side the Control Zone.
We use this scheme on all our pH Loop Controls. Seems to work quite well for
most Applications we have. Good luck
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