B&K Precision 2532B - Manual - Manual (Page 49)

49
Select FFT Window
Windows reduce spectral leakage in the FFT spectrum. The FFT assumes
that the YT waveform repeats forever. With an integral number of cycles,
there are no discontinuities in the signal shape. A non-integral number of
cycles in the YT waveform cause the signal start and end points to be at
different amplitudes. The transitions between the start and end points cause
discontinuities in the signal that introduce high-frequency transients.
Table 10 - FFT Window Instruction
Window Characteristics Applications
Rectangular Best frequency resolution,
worst magnitude
resolution. This is
essentially the same as no
window.
Symmetric transients
or bursts.
Equal-amplitude sine
waves with fixed
frequencies.
Broadband random
noise with a relatively
slowly varying
spectrum.
Hanning
Hamming
Better frequency, poorer
magnitude accuracy than
Rectangular. Hamming has
slightly better frequency
resolution than Hanning.
Sine, periodic, and
narrow-band random
noise. Asymmetric
transients or bursts.
Blackman Best magnitude, worst Single frequency