FX5U - Problem

[Kobz 0]

Hello,

I have struggled with temperature control in FX5U based on emded PID. I set up allmost all parameters from manual and my problem is that output of my regulator increase from 0 to 40 and then reaching max. value. After that output is reseting and things going once again. The strengest thing is when my measured value is greater than preset value. In this case PID output has min and max and still want to increase temperature  although he should stop. At the below I attache link to my program.  Heaters are controlled by SSR output  ,temperature sensor is thermocouple switch in to FX5-8AD input. 

Thanks for your help in advance !!!

PID-Problem.rar

p.s Regulator is inside TempControl POU

Edited 30 Apr 2020 by Kobz

[DWIM 1]

Hi Kobz

Just as input (you may be well aware of) : With PID, if you have a slight difference between target and current value, PID goes to MAX correction by definition. Because it fails to correct the difference and wants to correct that.

Maybe this is the nature of the problem. I don't know your setup exactly. Testing PID without real reaction is not practical.

[Kobz 0]

Thanks for your response DWIM !!! 

Yesterday I carry out some tests. If I leave only P part and switch off limits by rst b5 of S3+1  then PID will work correctly. I think the problem lies on limits but I have no idea where exactly. 

[DWIM 1]

My text from above was just an idea in general regarding PID. To be honest, I never did PID on FX5U. So far I have enough problems with Networking  Never mind PID !!!

You poor soul! Does that help  ?

Edited 1 May 2020 by DWIM