06-04-2009 02:12 AM
Hi everyone,
I know this subject has ever been treated but it's not been solved so here's my question :
First I want to make an FFT on datas. Then I want to filter values (replacing the values I want to filter by 0) and finally make an inverse FFT to get back the time signal without the high frequencies.
Now my question is, how do I modify complex datas or how do I make my modified array acceptable for the inverse FFT vi ?
Thanks a lot 😉
David
06-04-2009 02:46 AM
06-04-2009 02:58 AM - edited 06-04-2009 02:58 AM
Hi ! here's a little bit of coding i've done. I tried to get the real part to see what it was like but I just can't get it ! How do you get from that a frequency/amplitude spectrum ?
06-04-2009 03:29 AM
I think your problem is that you need some more FFT information. You are uncertain on how the output from the FFT VI is organized. Or more specific how to map the array content to different frequencies 😉
I suggest you read this http://zone.ni.com/devzone/cda/tut/p/id/4278, and this http://zone.ni.com/devzone/cda/tut/p/id/4541. In the last one they used an older labview version. Some of the functions mentioned has minor changes in newer Labview versions. But the theory still apply
If you can answer this question I can help you some more.
If I sample a 5Hz sine wave with 1Khz sample rate for 1 second, and then perform a FFT, at which array indexes will I find information about the 5Hz sine wave