create FFT size

[celynn]

this is the data file which the spreadsheet reads.

[celynn]

Hi altenbach,Thanks for replying.

i wonder if you understand wat i was trying to do over here...

Suppose i got 4 input signals i used only two of them to calculate the coherent function.  

[celynn]

Hi Altenbach,

i have problem in using the power spectrum and cross power spectrum. Can you help me?

[altenbach]

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@celynn wrote:
i have problem in using the power spectrum and cross power spectrum. Can you help me?

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Sorry, I have no idea what you are trying to do here. What kind of problems are you having?

You should say what the problem is! (e.g.: (1) My program crashes, (2) the result is wrong, (3) I don't understand the theory, (4) etc.)) 😉

What kind of data is this? What are you trying to measure?

[celynn]

Thanks for replying.

ok these datas contain 4 columns of sampled data. I am trying to measure the mulit-coherence between these signals. 

i need PSD and CSD as building blocks to build the coherence but the problem i am facing is i have no idea how to create the CSD from the FFT cross power.vi. mainly because i have no idea how the values of the PSD came about from the FFT power spectrum.vi

or do you have any suggestions in buliding the PSD from the FFT power spectrum vi other then using PSD.vi

(How do i attached multiple vi in an attachment?)    

[Megan B.]

Hi celynn,

There is a tutorial on The Fundamentals of FFT-Based Signal Analysis and Measurement in LabVIEW and LabWindows/CVI which I think you will find very helpful.  You can read the tutorial here: http://zone.ni.com/devzone/conceptd.nsf/2d17d611efb58b22862567a9006ffe76/c045a890751303a686256865006....  Take a look at it and let us know if you have further questions.

Good luck!
Megan B.
National Instruments