convert time domain to frequency domain

[lyn]

Inputs are as follows for testing;

input signal 1 : sinewave 50Hz, amplitude 10V
input signal 2 : sawtooth 800Hz,amplitude 1V

the 2 signals are added and fed into amplitude and phase spectrum.vi.
1. how to display the x-axis in frequency rather than time for the above setup? (amplitude spectrum magnitude output)

2. why is the magnitude attenuated. (~7V instead of 10V)

[Christopher Mitchell]

There are several FFT example VI's that come with LabVIEW that might help you out. One in particular, "Power Spectrum Example.vi", might be really helpful. This VI uses the 'FFT Power Spectrum.vi'. If you replace this with 'FFT Spectrum (Mag-Phase).vi' you might get the results you need.

[lyn]

thks,

1. however why is the amplitude of the 2 frequency component different even if i sent both signal be 10V?

2. why can't i get 10V for the amplitude? even if i run the power spectrum examples(with the FFT power spectrum replace with FFT spectrum mag-phase) the amplitude was attenuated.