Incorrect fft shape in labview

[PGeter]

[PGeter]

I am performing the FFT of a waveform measured by sr860 Lock-in Amplifier. But the FFT shape is wild. It appears to be incorrect. I have attached a screen shot of my Labview front panel and block diagram..Thank you for your assistance.

[mcduff · Accepted solution]

You are taking the FFT of a single point during each iteration. You need to have an array of points. Two options, wait until you collect all the data then do the FFT, or do a point-by-point FFT. I don’t have access to LabVIEW now to see if there is a point by point FFT function.

[PGeter]

Thanks your your reply...it could be helpful if you can give me a guide/example on  how to do the FFT at the end or point by point.. thanks

[GerdW · Accepted solution]

Hi PGeter,

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@PGeter wrote:

it could be helpful if you can give me a guide/example on  how to do the FFT at the end or point by point..

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Use the FFT function from the Point-By-Point functions palette - instead of the FFT you use now…

You should understand the datatypes you use in your VI(s) and know which datatypes are useful for your  task(s):

• a FFT from an array of a single element is mostly useless
• a FFT from an array containing lots of samples is most often preferred…

[PGeter]

Thanks GerdW!

it works