Slc 500 5/04 processor

There is a lot of useless information in your post. Please ask specific questions, and we will do our best to help you. What are your input and output devices, specific cards, what you are trying to achieve. The best thing would be to post your sample code (zip it first, or change the extenstion to zip). Don't worry if it isn't complete or polished, but it should have all the pieces in place relevant to your question.

To answer what I can understand your question is in general, the PID Input Process Variable must be scaled from 0 to 16383 and your PID Output Control Variable will range from 0 to 16383. These must be scaled from the Raw Input Data before being used in the PID Instruction, and the Control Variable scaled to your final Output device. The actual scaling details will depend on what they are, and we don't have that information.

I generally don't scale the Setpoint, because the PID Instruction can do it for you. Enter your minimum and maximum Setpoint in the Setup Screen. You can enter negative numbers for the minimum Setpoint, but make sure it matches you actual Raw Data Input, and it still has to be scaled to 0 to 16383.

Check out Chapter 9 of the Instruction Reference.
http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1747-rm001_-en-p.pdf

The more information you give us, the more we can help you.

Stu.....

1746-NIO4I I/O MODULE
1746-NR4 INPUT MODULE RTD
What I'm trying to do is enter the sp Set point value Via HMI
The set point will range from -328 to 1562

The rtd module input is Set for "scale for Pid"

Adam303 said:

1746-NIO4I I/O MODULE
1746-NR4 INPUT MODULE RTD
What I'm trying to do is enter the sp Set point value Via HMI
The set point will range from -328 to 1562

The rtd module input is Set for "scale for Pid"

Click to expand...

Ok, having the RTD Module set up for PID Scaling, you don't have to add a separate Scaling Instruction. That won't always be the case, as not all I/O Cards have that feature. You will need one for the Analog out in this case.

Attached is a short example, the cards may not be in the correct slots, so you might have to change the addresses to suite. I also put in the S5 Unlatch from your other thread. Change the extension from zip to rss, and you should be able to open it in RSLogix 500. I also included a pdf, but it will not be as useful for the nitty gritty details.

Read throught the PID Chapter of the Instruction Manual I gave the link to in my previous post, and it will explain what all the PID Control Block Words and Bits are for. Also, don't forget the RSLogix 500 Instruction Help, under the Help Menu.

Stu......

I had to reboot while I was writing the last post, so a couple of additional details. The second word of the PID Control Block is the Setpoint, so in the example, it would be N10:2. Write to the proper address from your HMI. You should do limit checking for out of range values at the HMI or the PLC, or better yet, both. So that the Operator can't input incorrect data. Screwing up a PID can fault your Processor on AB PLCs.

Stu.....