Q241 : Units of Forward Fourier Transform in FFTSES
Question When working with FFTSES in Forward mode, what is the meaning of the units (1/Hz) on the Y-axis for the frequency-domain signal.
AnswerThe quantity displayed on the Y axis in FFTSES is the forward Fourier transform of the signal. As such, its units should be those of the original signal multiplied by time (or divided by frequency). FFTSES assumes that the input signal has no units: basically, it is a per-unit value. This is why the units are displayed as 1 / Hz.
The actual units of the signal are given once you define an energization in the corresponding HIFREQ (or MALZ) model. If you use a current energization, the actual units will be Amps / Hz; if you use a voltage energization, the units will be Volts / Hz. This is done so that FFTSES can be used with several types of energization sources.