User Manual of Smart Digital Storage Oscilloscope
30
Fig.5-11 Hamming window
Quick Tips
If desired, use the zoom feature to magnify the FFT waveform.
Use the default
dB
scale to see a detailed view of multiple frequencies, even if they
have very different amplitudes. Use the
Vrms
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.
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
：
In FFT mode, the following settings are prohibited:
1)
Window set;
2)
XY Format in Display SET;
3)
“SET 50%” (the triggering level at the vertical point of signal amplitude) in Trigger
setting;
4)
Measure.
