FFT problem

[Vovich]

My Question is – I need to know how does “Extract Single Tone Information.vi” work, because it gives only information about one harmonic of the signal. But I have Signal with few harmonics and need to know their frequencies and amplitudes. So I need to rebuild it somehow to get not only one value of the signal with highest amplitude but to get two arrays of signals amplitudes and their frequencies.
The other way to do it , I think, It’s to use FFT. But as an output signal of FFT I get Power Spectrum (V^2 rms). And I don’t know how to convert V^2 rms value to normal V. I don’t Know formulas conversion. I think there’re inside of “Extract Single Tone Information.vi” but I cann’t look inside because
of password.
Probably It is the other solution.
Please help me with my problem.

[Nadav_Chernin]

What is about to use "Harmonic Analyzer" that founds in Analyze/Signal Processing/Frequency Domain?

[Vovich]

The problem is that when i use Harmonic Analyzer i get data but in V (rms). But i need them normal in V.
I probably I don't understand good how FFT works but Is there any possibility to convert data that i get from Harmonic Analyzer to normal data in V?

[JRA]

If you use the Harmonic Distortion Analyzer VI, there is an output called "components level." The Help File states the following:

components level contains the array of amplitudes of the measured harmonics in volts if the signal in is in volts. The array index is the harmonic number including 0 (DC), 1 (fundamental), 2 (second harmonic),... n (nth harmonic), up to and including the highest harmonic.

It sounds like you would get an array in Volts. You may want to try this out.

[Sam Shearman]

One straightforward (but somewhat inefficient) approach would be to wire
the tone-detection VIs together serially and use the residual signal
output as the input to the next VI. Each new call will detect the next
highest peak.

Hope this helps...

--Sam

Vovich wrote in news:506500000008000000D0610000-
1031838699000@exchange.ni.com:

> My Question is – I need to know how does “Extract Single
> Tone Information.vi” work, because it gives only information
> about one harmonic of the signal. But I have Signal with few harmonics
> and need to know their frequencies and amplitudes. So I need to
> rebuild it somehow to get not only one value of the signal with
> highest amplitude but to get two arrays of signals amplitudes and
> thei
r frequencies.
> The other way to do it , I think, It’s to use FFT. But as an
> output signal of FFT I get Power Spectrum (V^2 rms). And I don’t
> know how to convert V^2 rms value to normal V. I don’t Know
> formulas conversion. I think there’re inside of “Extract
> Single Tone Information.vi” but I cann’t look inside
> because of password.
> Probably It is the other solution.
> Please help me with my problem.