pid loops

hi I am new at programming pid loops we are trying to write a program maintaning a .5 inch water column of pressure using a 4-20 ma input and a 0-10 v out to a freq drive any hints, sample programs or any useful info would be greatly appreciated.

Do you have a PLC selected? PID loop programing is different for most PLCs even though the process and end result is the same. I have used Allen Bradley and Modicon extensively for PID process control.

yes I'm sorry i forgot to post that we are using an micrologix1200 and a 1762 if20fs analog module 2 in 2 out

I don't know if this would be helpful for your situation but, many modern drives have internal PID capabilities which would keep the whole system inside the drive instead of splitting it between the drive and the PLC.

You didn't mention which drive you are using but, check with the manufacturer or the Instruction Manual for the drive. It usually makes the whole thing a lot simpler.

the drive is an AB 1336 plus 2

The reference manual (PN956500) for programming the SLC 500 has a pretty good section on the PID function in Section 10. It essentially operates like any other PID algorithm. The tuning constants are entered in the PID control block, accessed by clicking on the Setup Screen field in the instruction block. There are examples in the manual.