PID Less Responsive

I have a A-B PLC5/20 with RSLogix5 and a PID with the values of .1,.005 and .005. I want to make the PID less responsive, it rings too much, too much overshoot and undershoot. Do I make the "P" number larger, such as .2? Is that the right direction?

Greetings bsprowls,



this is like “shooting from the hip - in the dark” ... but to simply answer your question:



you should make the Proportional setting lower (use a smaller value) in order to make the controller less responsive ...



if you need more help than that (and you probably will) then you need to tell us EXACTLY how your PID is set up ... from the values you mentioned, I’m assuming (gosh I hate that word) that you’re using a PD-type control block ... but I don’t know whether you’re using the “Independent/AB” equation - or the “Dependent/ISA” equation ... etc. ... etc. ...



just a tip ... most “nagging type” problems with PID are the result of improper setup and triggering issues ... unless you have some reason not to (proprietary, trade-secret, etc.), I’d strongly suggest that you post your .RSP file ... the initial numbers that you’re quoting make it look like you’re having “issues” with your setup ...

Ron's advice is good. Besides that you could also look at your update time and also by using timed vrs sti will make a difference. I seem to remember last month there was a discussion on PID's. There was a lot of good points made about piping, type of material used, heat PID's vers flow loop PID's, response times, etc.

More PID info

I have attached a .doc. Does it help? It controls a glass furnace.

it's a (little) step in the right direction ... but I can't tell whether (or not) you have a timer's Done bit "trigger" hidden behind the PID windows ... or whether (or not) Ladder File #3 is set up as an STI file ...

it would help a lot to see that .RSP file ... I'm sure someone will be able to help you out - if you can give them enough details ...

as for me, I'm going to be heading home and offline for awhile ... hurricane Ernesto is bearing down on us as I type ... not expecting much other than heavy rain and stiff winds ... but the power will probably be knocked out for a day or two ...