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I am using the FFT(mag and Phase) VI in version 6.1. When the sample count sent to the fft vi is increased the magnitudes decrease. What is causing this? Does the VI divide by the sample count?
The resolution of FFT depends on the sampling rate as well as the number of samples used to compute FFT (Fs/N). When you reduce the number of samples, the resolution of FFT comes down. This means that the peak that you detected prevously might have gone undetected.
Yes, I have kept the sampling frequency the same and the amplitude of the noise has increased by ~ 5x. So, if there are noise spikes at a low sample count they will not be "averaged out" by the fft?
