peak detection with coresponding frequencies

[jonhelpmejon]

I'm using the Peak Detect VI to list peaks in a certain frequency range from an fft spectrum. I get the list of peaks but the frequencies are listed as indexes of locations. How can I get the peaks to list with their true coresponding frequencies. Thank You in advance.

[Labviewguru]

You just have to associate those indexes back to the frequencies. I believe that since the output if the FFT is linear, that you can just directly associate the indices with the frequencies.

Good luck

[BruceAmmons]

When you calculate the FFT, one of the outputs is the frequency step size, dF. If you multiply this by your index values, you will have the frequency for each peak.

Bruce

[Guig]

Hello!

My company ask me to create a software with Labview that can dectect the resonants frequencies of a mecanical system (in fact, it is a CNC).
For that, I have the frequency response of that system, given under a transfert function (see attachment).
For example, I would have to find the frequency cercled by red.
I have tried to use differential or derivative functions, but seeing the "noise" of the waveform, it is unusable.
I have also the frequency response given by accelerometers, under a FFT.
It is simply to detect frequencies but it's less accurate in the lowest frequencies (above 20Hz-30Hz).
If you can tell me how i should process, it's very hopeful.
Thank you.

[shoneill]

Guig,

If you go to the trouble of renaming a BMP to JPG, then why don't you simply save the graphic as JPG in the first place.

BMPs are very large and take a long time to load.  If you're afraid of JPG losing too much detail, try PNG instead.

You do know that simply renaming a picture file doesn't change it's format, don't you?

Shane.