Fft - Rigol DS8000-R Series User Manual

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FFT

FFT (Fast Fourier Transform) is used to transform time-domain signals to
frequency-domain components (frequency spectrum). DS8000-R oscilloscope
provides FFT operation function which enables you to observe the time-domain
waveform and spectrum of the signal at the same time. FFT operation can facilitate
the following works:
Measure harmonic components and distortion in the system;
⚫
Display the characteristics of the noise in DC power;
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Analyze vibration.
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Click Math → Math1 → Operator to select "FFT":
Click Operation continuously to enable or disable the FFT operation function.
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When enabled, the operation results are displayed as purple waveforms on the
screen. At the same time, the parameters such as vertical scale, center
frequency, and resolution are displayed at the bottom of the screen, as shown in
the following figure. Of which, FFT resolution is the quotient of the sample rate
and the number of FFT points. If the number of FFT points is a fixed value
(65535 at most), then the higher the sample rate, the higher the resolution.
Vertical Scale
Click Source to select the channel. The available channels are CH1, CH2, CH3,
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and CH4.
Click Offset to set the vertical offset of the operation results. For setting
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methods, refer to the descriptions in "Parameter Setting Method".
Click Scale to set the vertical scale of the operation results. For setting methods,
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refer to the descriptions in "Parameter Setting Method". If the source
channel unit is set to "V", then the unit of the vertical scale is displayed as dBV.
If you select other source channel units, then the unit of the vertical scale is
displayed as dB.
Click AutoSetting to adjust the vertical scale and offset of the operation results
⚫
to the optimal value according to the current configuration, so as to better
observe.
Click More → Unit to select the vertical unit. The vertical unit can be set to
⚫
dBm/dBV or Vrms. The vertical amplitude can be expressed both in log form and
linear form, with dBm/dBV and Vrms as the unit respectively. If you need to
display the FFT spectrum within a larger dynamic range, dBm/dBV is
recommended.
6-6
Sample Rate Center Frequency Span
Chapter 6 Operations and Measurements
DS8000-R User Guide
Resolution