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October 2014
Page
37
Figure 32.
Hanning window.
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Quick Tips
If desired, use the zoom feature to magnify the FFT waveform.
Use the default dBV RMS scale to see a detailed view of multiple
frequencies, even if they have very different amplitudes. Use the linear
RMS scale to see an overall view of how all frequencies compare to each
other.
Signals that have a DC component or offset can cause incorrect FFT
waveform component magnitude values. 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.
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Term interpretation
Nyquist frequency
: The highest frequency that any Real Time Digital
Oscilloscope can measure is exactly half of the sampling rate under the
condition of no mistakes, which is called Nyquist frequency. If under-
sampling occurs when the frequency sampled is higher than Nyquist
frequency, "False Wave" phenomenon will appear. So pay more attention to
the relation between the frequency being sampled and measured.
Note:
While FFT mode is turned on, DO NOT USE THESE SETTINGS:
Horizontal window setting.
Change source channel in CH1/CH2 Setup menu.
Turn on XY Format.
Trigger control "SET 50%".
Auto-scale function.