RSTune Software for PID Loops

[SCRUFF]

I have a PID loop controlling the stroke on a Soda Ash Dosing Pump to control pH on a water treatment plant. There is an extrememly long deadtime and I cannot successfully tune this PID loop. Not only that but I have trended the pH and it seems to drop out every now and then to basically nothing.

Thus, I was wondering if RSTune Software could assist in controlling this pH PID Loop as well as does anybody know the ~cost of this software and where I can get a copy of it?

THANKS!!!

 

[CroCop]

PH is logorathmic.
PID alone will have a tough time.
If you can linearize your PH signal, that should make tuning MUCH easier.

 

[finski2]

I'm not sure if RSTune has the characterizer funtionality, but I know that RSLoopOptimizer does.

For a typical non-linear loop where PV/CV is not constant you would use an output characterizer based on test data points. However, for the pH loop, you would use an input characterizer.

I haven't done any pH loop tuning, but if you find the literature/user guide for the software, it will explain it all better than I can.

 

[Sheldn]

You can linearize the signal by developing a titration curve. This is process dependant.

If you are using a Control Logix PLC function block you can try using the FGEN function to linearize the pH signal before using the PIDE instruction.


Some resources from the experts that you may find interesting.
http://www.expertune.com/Advanced.html#pH
http://www.expertune.com/artCharact.html#pH
http://www.controlsoftinc.com/mantra-ph.shtml
http://chemware.co.nz/tcurves3.htm

 

[SCRUFF]

I am not familiar w/ the FGEN Block and not quite sure even after reading the help file how to set it up? Can anyone help me out???