Micrologix 1400 TC module + PID + SCP

Hi,

I have a micrologix 1400 with a 1762-IT4 module. I have channels 1 and 2 set up for "Scaled for PID" because I am using a PID to control temperature.

How do I correctly scale the units to display the temperature in degrees? If I change the data type to "engineering units" I get the correct temperature but I assume this won't work correctly with a PID.

Thanks

Ok, I think I got the scaling issue figured out. Now I need some help with the PID instruction. I am not getting any output variable change, it just stays at 0. Can someone take a look at my set up and help me out?

Your Proportional Gain (Kc)) is zero!
I'd set it at 100 and then increase it in hundreds increments until the output starts oscillating; once there enter 1/2 of the value at which the output starts oscillating.

Ok, I've got it working but how to I tune it? What do you mean by the output starts oscillating? Is that when I am at setpoint?

The adjustment of the Kc is the most basic PID manual loop tuning.
Depending of the application's specific particularities, there is a value of the Kc at which, the PID output = Pv (Process Variable) will start oscillating above and bellow the Setpoint; usually this value will need to be halved and then entered as the PID Proportional Gain Kc.
Refer to http://en.wikipedia.org/wiki/PID_controller
for the PID Loop Manual Tuning theory.

Also some good info at link below, click on sample lessons, scroll down until you see

"What is P in PID"
"What is I in PID"
"What is D in PID"

http://www.ronbeaufort.com/main_frame_page.htm