User Manual of
OWON
Color Mixed Signal Digital Storage Oscilloscope
28
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The FFT feature provides four windows. Each one is a trade-off between frequency
resolution and magnitude accuracy. What you want to measure and your source signal
characteristics help you to determine which window to use. Use the following guidelines
to select the best window.
Type Description
Window
Rectangle
This is the best type of window for resolving
frequencies that are very close to the same value
but worst for accurately measuring the amplitude of
those frequencies. It is the best type for measuring
the frequency spectrum of nonrepetitive signals and
measuring frequency components near DC.
Use rectangle for measuring transients or bursts
where the signal level before and after the event are
nearly equal. Also, use this window for
equal-amplitude sine waves with frequencies that
are very close and for broadband random noise with
a relatively slow varying spectrum.
Hamming
This is a very good window for resolving
frequencies that are very close to the same value
with somewhat improved amplitude accuracy over
the rectangle window. It has a slightly better
frequency resolution than the Hanning.
Use Hamming for measuring sine, periodic and
narrow band random noise. This window works on
transients or bursts where the signal levels before
and after the event are significantly different.
Hanning
This is a very good window for measuring
amplitude accuracy but less so for resolving
frequencies.
Use Hanning for measuring sine, periodic, and
narrow band random noise. This window works on
transients or bursts where the signal levels before
and after the event are significantly different.
Blackman
This is the best window for measuring the
amplitude of frequencies but worst at resolving
frequencies.
Use Blackman-Harris for measuring predominantly
single frequency waveforms to look for higher
order harmonics.
Fig.5-9,5-10,5-11,5-12
show four kinds of window function referring to sine wave of
