Bk-precision 2532B - Manual Bedienungsanleitung PDF herunterladen (Seite 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

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Bk-precision 2532B - Manual Bedienungsanleitung Seite 49