Problem with bandpass FFT filter

[oleg_ees]

Hi,

I've developed bandpass filter, based on FFT, and faced the problem, that this filter does not work with portions of array less than 3000 samples (sample rate 50 kHz). If the filter is turned on, and the number of samples to read less than 3000, all indicators display zeros.

DAQ test task - data from 12 channels (2xNI9225, 2xNI9227 in cdaq-9188), moved to PXI-8110, so the problem must be in logic, not in physical resources.

Thanks in advance for any suggestions. 

Regards,

Oleg

[BillMe]

What does the signal look like for the 3000 samples? Are you sure there are frequency components inside your pass band? Can you post a file with the data?

[oleg_ees]

The signal is simple sine 50 Hz (I bet, because it's power network), with noises I want to avoid. The bandpass is between 40 and 60 Hz. When the number of samples to read less than 3000 and filter is turned off, I see the correct signal, but with noises. When I turn on the filter, all data on charts, graphs and numeric indicators disappeared. When the portion of array is 3000 and more - everything works well.

[johnsold]

Please post some of your real data.  We cannot tell enything from just the VI.  There is nothing obvious about it which would suggest a 3000 sample limit.  The best way would be for you to run your VI. When you have data present use the Edit menu item: Make Current Values Default. Tehn save the VI and post it with the data.

You also do not need the sequence structure.  The VI will run exactly the same without it.

Lynn

[oleg_ees]

Lynn,

I've attached my project, main file is LR simple.vi

In the first window signal without filter, in the second - with filter. Please, take no notice of the numbers, because it's system no-load state. 

I shall be obliged if you point of other mistakes in my application.

Regards,

Oleg