pid autotuning wizard settings

[Fibo]

I'm having a heck of a time using the autotuning wizard... I have my sytem set up with PID gain values that get pretty close to where I want to be, now when I use the autotune vi to try and get better gain values, it gets stuck on the screen I'm showing here... my PV range is 0-750.... I chose my relay setpoint amplitude to be 5 (I grabbed this value out of the air)... and I told the vi that my noise is about 5.... I set my sampling time on the VI at .75 seconds.... I just kept messing with the sampling time until I got a good response from my controller, but I'm not sure what the logic is to picking a sampling time... I'm using this to control a valve and the valve moves pretty slowly

how long should I have to wait for this to calculate new gains?  does anything in the picture seem off to you?

much thanks!

Message Edited by Fibo on 03-12-2010 04:22 PM

[nitad54448]

hi

can you put a positive value for Kc  ?

N