PIDE CV Erratic

tekha63

Member
T
Join Date
Nov 2012
Location
Cambridge
Posts
3
Has anyone experienced a CV spike when the PV is already above the SP using a PIDE in a CompactLogix? Attached picture shows a trend recording with the SP/green, PV/blue and the CV/white.

RH Press1 Lower.jpg
 
welcome to the forum ...

can you post your entire program file? ... tip: if you're allowed to do that, first do a "File Save As" and save the file as an L5K format ... then zip that file and post it right here in this thread ...

also ...

you really need to change the colors on your trends before you post them ... the forum changes your screen shots to a JPG format - and the dark colors get lost on the black background ... old people (like me) can't read your graph ...
 
I don't believe in coincidences. Doesn't anybody see what I do?

Is it a coincidence that the CV is restored to what looks like the exact value it had before? I would look at the PLC code to see where something external to the PIDE block is restoring or reseting state the CV or other state variables that are used to calculate the CV.
 
I would look to see if something is writing to the "Feedforward".

We are just guessing until you post the program, if you can.
 
Based on the chart and his descrition, the CV was pegged at 100% and just started tailing off a short time prior to reaching setpoint. Then it dropped to about 60% before it pegged back up to 100%. Steady state looks like about 55% CV.
 
Mickey said:
I would look to see if something is writing to the "Feedforward".
Click to expand...
This could be but to write exactly the right amount to get to 100% is doubtful. If the feed forwards was 'adjusted' by too much the CV would remain in saturation a little longer while the integrator winds down to bring the CV out of saturation. If the feed forwards adjustment was too little the CV wouldn't have gone bat to 100%. I doubt is is the feed forward.
 
Looks like one of two things. Either an operator put the loop in manual-changed the output-put loop back to auto, OR, there's something goofy going on with the programming/application. From the the tagname of the loop, I suspect the latter.
 

Similar Topics

Ron Beaufort
RSLOGIX 5000 - SIGNAL FLOW FOR PIDE - STATES AND MODES
Greetings ... someone sent me a request for some student handsouts that I developed ... turns out that I had this hosted on my business website...
Replies
0
Views
132
Ron Beaufort
Ron Beaufort
A
PIDE Autotuning for Level Control
Have a logix controller and I'm using the PIDE block for the autotuner. I've got the hang of doing it for direct control things like pressure...
2
Replies
21
Views
1,768
drbitboy
drbitboy
jkerekes
PIDE CVFaulted (Status1.2) Causes
Studio 5000 version 34. Have error on PIDE CVFaulted (Status1.2), Control variable (CV) health bad. No more information online or in...
Replies
3
Views
968
tlf30
tlf30
P
Factory Talk Studio Global Object - PIDE PV communication failed?
Hi everyone, I am trying to add a control loop to my HMI interface however I keep getting the following issue, any idea why this would happen?
Replies
8
Views
1,615
cardosocea
C
R
Logix PIDE Scan
We have a routine that we trigger with a JSR every 10 seconds that has PIDE instructions. This resides in a Periodic task that triggers every...
Replies
6
Views
923
drbitboy
drbitboy
Back
Top Bottom