What are the output units of the Power Spectrum VI, and how are they calculated?
The output units of the Power Spectrum VI are in Volts RMS squared (Vrms^2), but this power is halved between the positive and negative frequency components. If the input signal unit is not in Volts, the output spectrum unit will be RMS-squared of the input signal unit.So, if the peak amplitude (Vpk) of the input sinusoidal signal is 1 Vpk, its RMS value is:Vrms = 1/sqrt(2) = 0.7071067, so Vrms^2 = (0.7071067)^2 = 0.5 But because the Power Spectrum computes the "double-sided" FFT power spectrum, the resulting expected value is half of the Vrms^2 value. For the example above, we would expect a power spectrum value of 0.5/2 = 0.25 Vrms^2 at the array index corresponding to the frequency of the sinusoidal signal.
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