From Friday, April 19th (11:00 PM CDT) through Saturday, April 20th (2:00 PM CDT), 2024, ni.com will undergo system upgrades that may result in temporary service interruption.

We appreciate your patience as we improve our online experience.

LabVIEW

cancel
Showing results for 
Search instead for 
Did you mean: 

Power spectrum VI and number of samples

Please look at the Help in the part where it is explained about the number of samples. 

It is not clear to me what happens if the number of samples is not respecting what is said in the help. 

That is I cannot understand if the results from Power Spectrum VI are reliable or not when the number of samples is not factorable as the product of small prime numbers. 

Is it used zero padding or what? In the block diagram a library is called, so I cannot figure out what it is doing. 

Thanks

 

0 Kudos
Message 1 of 2
(2,094 Views)

You can always compute a Discrete Fourier Spectrum "by hand", one frequency at a time.  Do you understand spectral analysis, and the math behind it?  Do you understand the difference between an FFT (Fast Fourier Transform) and a DFT (Discrete Fourier Transform) (hint -- it boils down to the difference between n ln n and n^2).

 

You might also look at using windowing to transform your set of data points to a (larger) set whose size is a power of two, thereby gaining the efficiency of the FFT at a small cost of the Window filter.

 

Bob Schor

0 Kudos
Message 2 of 2
(2,060 Views)