OWON SDS Series - Manual (Page 35)

5.Advanced User Guidebook
Figure 5-10 Rectangle window
Notes for using FFT
 Use Zoom function 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, the following settings are prohibited:
1) Window set;
2) XY Format in Display SET;
3) Measure.
Use VERTICAL POSITION and VOLTS/DIV Knobs
1. The VERTIVAL POSITION knob is used to adjust the vertical positions of the
waveforms, including the captured waveforms and calculated waveforms.
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