Owon SDS series User Manual page 33

FFT function in this oscilloscope transforms 2048 data points of the time-domain signal
into its frequency components mathematically and the final frequency contains 1024
points ranging from 0Hz to Nyquist frequency.
Taking the FFT operation for example, the operation steps are as follows:
1. Press the Math button and call out the Math menu.
2. Press the H2 button and call out the FFT menu.
3. Press the F1 button to choose CH1 as the source.
4. Press F2 button, the windows item will display at the left of the screen, turn the M
knob to select Window, including Rectangle, Hamming, Hanning and Blackman.
5. Press F3 button to choose the Format, including dB, Vrms.
6. Press F4 button, the zoom window will display at the left of the screen, turn the M
knob to zoom in or out the wave of the multiple including ×1, ×2, ×5, ×10.
To select the FFT window
■ There are four FFT windows. Each one has trade-offs 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
Best solution for frequency, worst for magnitude.
Best type for measuring the frequency spectrum of
nonrepetitive signals and measuring frequency
components near DC.
Recommend to use for:
Rectangle
Better solution for magnitude than Rectangle, and
good for frequency as well. It has slightly better
frequency resolution than Hanning.
Recommend to use for:
Hamming
5.Advanced User Guidebook
Characteristics
Transients or bursts, the signal level before and
after the event are nearly equal.
Equal-amplitude sine waves with frequencies
those are very close.
Broadband random noise with a relatively slow
varying spectrum.
Sine, periodic and narrow band random noise.
Transients or bursts where the signal levels
before and after the event are significantly
different.
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Window