identification DAQ

[Studentisil]

Hello

i'm trying to identify a process in real time with Labview 7.0.

The process is quite simple : it's made up of 2 aop.

i use recursiv method to identify the process.

i generate a square wave at the input of the process with DAQ ( USB 6008 ) and i read sample from the output i fthe process. A Butterworth filter is used like anti aliasing filter.

The input and output are sent to identification block.

But the model estimate doesn't match with transfer function of the process.

Can someone help me ????

bye

Studentisil