Controllogix PID in very slow reacting loop

[TimSaunders]

Use the IMC instruction. It is like a PIDE except it's meant for long dead time loops like this one. I have personally used it on waste water aeration and it works great.
Here's a link to a RA knowledgebase article explaining the Advanced Process Instructions
https://rockwellautomation.custhelp.com/app/answers/detail/a_id/54859

 

[terry56]

Thanks for the idea Tim, I would have to change from ladder PID to Function Block PIDE to do this.

Looks like I found a solution that the customer is happy with: Flow*1440*chlorine SetPoint*8.34/1000000

This gives Pounds Per Day. I suspect it will need a tweak for demand.