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From: cp617 on 26 Jan 2006 15:43
Hi, I put together a VI to calculate the FFT of a sine wave signal and graph the result in the frequency domain. In theory, if we take the Fourier Series of a 500Hz sine wave signal, we should see a spike at 500 Hz in the frequency domain. However, the result I got is very noisy and there are spikes everywhere. Could you please take a look at the VI and let me know what is missing?
Thanks  everyone for you help in advance.


fft.vi:
http://forums.ni.com/attachments/ni/170/163587/1/fft.vi
From: Nishant on 26 Jan 2006 23:13
Hiiii,
             I think you should use the special kit to take the fft, which will give you the perfect answer, here i am attaching a figure,which will show you that how perfect it is by using the special express vis, bcoz they are also given with the sensor sensitivity and ave. paras, which will give u the exact idea.
i forgot to attach the figure in last response.
Thanks,
Nishant
Message Edited by Nishant on 01-26-2006 10:08 PM


FFT.jpg:
http://forums.ni.com/attachments/ni/170/163635/1/FFT.jpg
From: Nishant on 26 Jan 2006 23:13
Hiiii,
             I think you should use the special kit to take the fft, which will give you the perfect answer, here i am attaching a figure,which will show you that how perfect it is by using the special express vis, bcoz they are also given with the sensor sensitivity and ave. paras, which will give u the exact idea.
Thanks,
Nishant
From: cp617 on 27 Jan 2006 08:13
Thanks everyone for your speedy replies. I can't open the VI from Conseils because I'm still using LabVIEW 6.1. The graph from Nishant's example is what I'm looking for. Nishant, could you attach your VI as well? thanks.
I'm using the 500 Hz wave file as an example. The actual data that will be fed to the VI is coming from the NI 4472 card, which is taken from a speaker of an external device. What I'm trying to do is: Play a sine wave signal in an external device. Then, capture the audio and check to see if there was a pop or a click in the audio. 
Thanks again for your help.
CP


500Hz.zip:
http://forums.ni.com/attachments/ni/170/163691/1/500Hz.zip
From: Nishant on 27 Jan 2006 23:43
Hiii,cp
              It is glad that it is helpful to you and here i am also attaching a vi, but i dont think that you can open it, totaly right, coz u must have the add-on kit called Vibration and moitoring System for this, and another drivers are of my card, from which i am taking the data, i am using the card Ex-92026.
Thanks,
Nishant    
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