what is the difference between SMT zoom FFT, FFT spectrum, SVT FFT spectrum, complex FFT vi, real FFT vi in the labview functions palette. I am getting different spectrums on performing the above mentioned ffts on the same time domain data
Complex FFT takes a complex input array and gives a complex output array. Real FFT assumes the input data is real valued only, ie imaginary parts are zero. It can be computed quicker than the complex FFT so if data is real it is better to use this. There is a Power Spectrum vi that computes normalised power of the complex output of the FFT for a real input sequence(sum of squares of real and imaginary parts). Auto Power spectrum gives a single sided output ie positive frequencies only. This is normalised as well. Just check the help on the vis for the normalisation factor. The Zoom FFT isn't in the professional edition of LV. I know zoom FFT comes with the S&V toolkit. It allows one to measure the spectrum of a signal with improved frequency re solution over a limited band. I think SVT stands for Sound and Vibration Toolset.
