Mitsubishi A3A-PLC PID programming

[Francois]

How can I ensure that a PID loop is executed at exactly the same time interval? A program I'm monitoring has a sample time (Ts) of 250mS but is actually +-3 times slower. The integral time is also slower than the value enteres (Ki).

 

[bradal]

What do you mean by 3 times slower, the sample time of 250ms is just how often the PID calculates. Are you comparing two PID loops in one controller??? Well if they are controlling different processes of course they will react differently that why you use PID loops. Clarify what you are asking!!!

 

[Francois]

I am revering to one spesific loop. The PID calculation time is set at 250Ms, but when analising the controler on a looptuning device it shows that the calculation is in fact done only at about every 800mS.