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Chapter 6 MATH and Measurements
2. Select Window Function
Spectral leakage can be considerably decreased when a window function is used.
DS2000E provides four kinds of FFT window functions. Different window
functions have different characteristics, and are applicable to the measurements
of different waveforms. You need to select the window function according to the
waveform to be measured and its characteristics. Press Window to select the
desired window function and the default is "Rectangle".
Table 6-1 Window Functions
Window
Rectangle
Hanning
Hamming
Blackman
3. Set the Display Mode
Press Display to select "Split" (default) or "Full Screen" display mode.
Split: the source channel and the FFT operation results are displayed separately.
The time domain and frequency domain signals are displayed clearly.
Full Screen: the source channel and the FFT operation results are displayed in
DS2000E User's Guide
Characteristics
The best frequency
resolution;
the poorest amplitude
resolution;
similar to the situation
when no window is
multiplied.
Better frequency
resolution;
poorer amplitude
resolution.
A little bit better
frequency resolution
than Hanning
The best amplitude
resolution;
the poorest frequency
resolution
Waveforms Suitable for
Measurement
Transient or short pulse, the signal
levels before and after the
multiplication are basically the same;
Sine waveforms with the same
amplitude and rather similar
frequencies;
Wide band random noise with
relatively slowly changing waveform
spectrum.
Sine, periodic and narrow band
random noise.
Transient or short pulse, the signal
levels before and after the
multiplication are rather different.
Single frequency signal, search for
higher order harmonics.
RIGOL
6-5
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