STI timed PIDs on SLC5/05 to Compactlogix migration

Hello,

I've done several migrations from SLC 5/05's to 5370 L33ER Compactlogix controllers.

I've just encountered my first PID instructions with STI timing parameters. Is this similar to a PID within a scheduled task in new controllers?

Do I need to make any special changes or will the conversion tool translate this fairly seamlessly? I know I'll have to verify the PID from the PCE warnings, but I'm just concerned about the PID executuion once converted.

They control several high output pumps. Any insight from any of the vets out there is as always appreciated.

Thanks,

Ben

Yes, the old STI would be similar to a periodic task in Compact Logix. I never do conversions, only upgrades, so cannot address your other questions.

You will want to be careful with the controller selection and tuning. I would expect the translator to correctly select the dependent gains equation, which will allow for direct copy of the reset time [minutes] and rate time [minutes]. The proportional gain will need some careful examination because in the SLC the instruction set reference implies that scaled error is used in the PID computation, whereas the PLC-5 and Logix processors are based on 0 to 100% scaling. It may be necessary to compensate for this if the SLC was not using default 0-16383 scaling for both the input and output. I find the SLC reference manual a bit confusing on this point, and it is especially important with the dependent gains form.