B&K Precision 2552-2559 - Manual - Manual (Page 41)

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Figure 24 - Math Function Screen
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 11 - 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
Set dBVrms to
be the vertical
Scale unit
Time base
scale
Sampling
rate