estimate frequency response

[xf]

Hello, i've some questions regarding how to use SI Estimate Frequency Response.vi. For example, I use the sample data C:\Program Files\National Instruments\ExpressWorkbench\System Identification Assistant\Examples\dc_motor\dc_motor_test1.lvm.This data has 2 sets of data, both sample sizes of 5000.

Actually I use System Ident Assistant and then convert the workbench proj to vi. See try.vi, why is there an error? Err -41201: The signal length is too small for computation, or the stimulus and response signals are not of the same length. I tried the window length of 1024 and 256 for the freq bin. Since the window frame is shorter than the sample, shouldn't it be alright?

[Barp]

The error is because the VI "Load from LVM" VI is not finding the file expected and it is giving zero out. Try to see if the files was correctly saved and you can browse this file from LabVIEW.

Hope this helps.

[xf]

Hi thank you..

But my error isn't from the load. Its from SI estimate frequency response.

I have that file and the file can be loaded. Its just at that the 2 signals entering SI estimate frequency response vi.

For this case, using the test data given by Labview example, the dc_motor_test data has 5000 samples, what should i set for channel length and freq bin?

🙂

[BCho]

Hey xf,

Thanks for your post. If you run your try.vi twice you will see that the code executes the loop the first time without an error. Then you will notice that the second time the loop executes the error is through because you are not getting zero out as Barp pointed out. If you take your structure out of the while loop, you should be able to run your code without an error. Is there any particular reason you are using the while loop?

Let us know if this helps.

Ben

Application Engineering

National Instruments

[xf]

Hello all,

Thank you for all your help... Removing the while loop helps. Run once is enough.

xf.