Need help with PID control please!

[Mickey]

I don't know how to re-initialize the PD block, never done that before. I saved the program and uploaded its current saved state.

PID Initialized

Each time you change a value in the control block, the PID instruction takes over twice as long to execute (until initialized) on the first scan. Displays one of the following:

NO - PID instruction not initialized after you changed control block values

YES - PID instruction remains initialized because you did not change any control block values

Caution: Do not change the range of input or engineering units when running. If you must do this, then you must reset this bit to re-initialize. Otherwise, the instruction will malfunction with possible damage to equipment and injury to personnel.

Going from run to program and back to run will do this.
Or open the PID configuration screen and click on PID Initialize and change it to no, the next time the rung is scanned it will reinitialize. See picture below.

You are going to have to change your "Scale Low"/ Scale High" on the input card back to 0-32767.

Also in the program you posted the loop update is still at 2 sec.

 

[sparkytex]

Ok, so I change the MAX and MIN to 0-32767 in the I/O and change the update time to .5 seconds then click on the PID setup screen and click No on Initialize PID?

"Caution: Do not change the range of input or engineering units when running. If you must do this, then you must reset this bit to re-initialize. Otherwise, the instruction will malfunction with possible damage to equipment and injury to personnel"

the valve is in manual at 15% open right now, changing the scaling of the input shouldn't affect the valve in any way, correct?

 

[Mickey]

the valve is in manual at 15% open right now, changing the scaling of the input shouldn't affect the valve in any way, correct?

No, not as long as its in manual.

If you want a bumpless transfer going back and forth "Auto/Manual" then consider enabling "PV Tracking"

PV Tracking

Select "Yes" or "No" for PV tracking. Select no tracking if the algorithm can tolerate a bump when switching from manual to automatic control. Select PV tracking if you want the setpoint to track the PV in manual control for bumpless transfer to automatic control.

 

[sparkytex]

AND WE HAVE A WINNER!!! I changed the I/O min max to 0-32767. PID update time is now .5 seconds. The MINS is 0 and the MAXS is left unchanged at 100. Once I clicked on the re-initialize it magically went to 40 degrees and is now updating correctly. A very big thank you to every one who has helped out in this nightmare for me.

Would also like to know further about what exactly the re-initialize is doing!!

Thanks, Tex