Temperature Control with Micrologix 1200

I have a Micrologix 1200 Cat# 1762-L40AWA. I have a card from Spectrum Controls Cat# 1762-SC-1F40F4 this card has a theromcouple input and analog outputs. I have a J type thermoucouple, and I am running about 550 degrees F. I have a damper to control the heat that is controlled by 4-20mA signal. There is currently an Athena Temperature controller doing the job right now. We need to be able to enter a setpoint temperature into the PLC and let it maintain the setpoint. I was told by Rockwell that I need to use a PI control to accomplish this.
If anyone has any experience with this, your input would be greatly appreciated!

Thanks!

You should use the PID instruction. See Chapter 19, page 255, of your MicroLogix 1200 and MicroLogix 1500 Programmable Controller Instruction Set Reference Manual. If you only want to use the PI part of the control equation, leave the "Rate Td" (Derivitive term) in the PID Setup Screen set to 0.

Lancie1 said:

You should use the PID instruction. See Chapter 19, page 255, of your MicroLogix 1200 and MicroLogix 1500 Programmable Controller Instruction Set Reference Manual. If you only want to use the PI part of the control equation, leave the "Rate Td" (Derivitive term) in the PID Setup Screen set to 0.

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Thank you ! I found the page that you mentioned, I'll see if I can make it work.

Great! Setting up the PID block is not easy the first time. You almost always have to add some front-end logic to scale your Setpoint and Process Variable to the proper ranges. You might also need a rung after your PID instruction to scale the PID Control Variable output to the proper range for your damper controller.

There have been many examples of the PID instruction posted on this site that you can search and read.