From 11:00 PM CDT Friday, August 9 - 11:00 AM CDT Saturday, August 10, 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
Did you mean:

Solved!
Go to solution

## how to find the ratio of two frequencies in fft

Hi i am john,

I need to find the ratio of 1st and 2nd frequencies in fft graph.

Already i got information from this site only. Mr. Alten helped me.

Now i have to continue the same problem and need to find the ratio of the frequencies.

I will attach my vi file and text file.

Message 1 of 8
(3,286 Views)
Solution
Accepted by topic author johnsasikennedy@gmil.com

## Re: how to find the ratio of two frequencies in fft

john,

Do you need the ratio of the frequencies or the ratio of the amplitudes of the components at those frequencies?

The Extract Multiple Tone Information.vi from the Signal Processing >> Waveform Measurements palette should do what you want.

The frequency resolution is not very good because you have relatively few cycles of the waveforms (~2 for the lower frequency). I added some zero padding to improve the resolution, although a larger data sample would be better.

Lynn

Message 2 of 8
(3,245 Views)

## Re: how to find the ratio of two frequencies in fft

Thanks a lot  Mr.JohnSold.

But i need to find fft for the other sample of datas. i cant be able to get it through the vi which u have posted. please check it and send me the new program. Sorry for disturbing u.

PFA

Message 3 of 8
(3,182 Views)

## Re: how to find the ratio of two frequencies in fft

Why can't you use the same VI on a different set of data?

Why did you post the exact same response to your other, very similar message trhead about FFT.?

http://forums.ni.com/t5/LabVIEW/How-to-get-fft-for-my-xy-graph/m-p/2685637#U2685637

(PS.  There is no word spelled "u".  There is, however, a word that is spelled "you".)

Message 4 of 8
(3,170 Views)

## Re: how to find the ratio of two frequencies in fft

sorry. But i need it urgent. Please do the needfull

Message 5 of 8
(3,149 Views)

## Re: how to find the ratio of two frequencies in fft

The negative times in the two files you posted may be part of the problem. Shift the time axis so that all the data occurs at non-negative times and see if that helps.

Lynn

Message 6 of 8
(3,115 Views)

## Re: how to find the ratio of two frequencies in fft

Its not coming properly. Will you be able to help with the program

Message 7 of 8
(3,086 Views)

## Re: how to find the ratio of two frequencies in fft

johnsasikennedy@gmil.com wrote:

Its not coming properly. Will you be able to help with the program

The negative times are not a problem, because we only care about dx in the resampled data. You simply need to ensure to trim the leading zeroes due to the non-numeric file header. (or edit it out manually from the file).

(Also please don't use these doule-extension. *.lvm.txt. That only confuses!)

Message 8 of 8
(3,079 Views)