OWON VDS Series - Manual (Page 27)

Figure: Rectangle window
Figure: Blackman window
Figure: Hanning window
Notes for using FFT
 Select "Scale" to magnify the FFT waveform if necessary.
 Use the default dB scale for details of multiple frequencies, even if they have very different amplitudes. Use the Vrms scale to compare
frequencies.
 DC component or offset can cause incorrect magnitude values of FFT waveform. To minimize the DC component, choose AC Coupling on the
source signal.
 To reduce random noise and aliased components in repetitive or single-shot events, set the oscilloscope acquisition mode to average.
What is Nyquist frequency?
The Nyquist frequency is the highest frequency that any real-time digitizing oscilloscope can acquire without aliasing. This frequency is half of the
sample rate. Frequencies above the Nyquist frequency will be under sampled, which causes aliasing. So pay more attention to the relation
between the frequency being sampled and measured.
Note：
In FFT mode, only support to set coupling, voltage division and zero position in Channel window, other operations are prohibited. If you want to
enter other menus, uncheck "FFT" first.
11.How to zoom the waveform
Click to show Function menu, choose "Display".
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