Owon tds series, Руководство пользователя

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5.Advanced User Guidebook
29
Hamming
Better solution for magnitude than Rectangle, and
good for frequency as well. It has slightly better
frequency resolution than Hanning.
Recommend to use for:

Sine, periodic and narrow band random noise.

Transients or bursts where the signal levels
before and after the event are significantly
different.
Blackman
Best solution for magnitude, worst for frequency.
Recommend to use for:

Single frequency waveforms, to find higher
order harmonics.
Bartlett
The Bartlett window is a slightly narrower variant
of the triangular window, with zero weight at both
ends.
Kaiser
The frequency resolution when using the Kaiser
window is fair; the spectral leakage and amplitude
accuracy are both good.
The Kaiser window is best used when frequencies
are very close to the same value but have widely
differing amplitudes (the side lobe level and shape
factor are closest to the traditional Gaussian RBW).
This window is also good for random signals.
Notes for using FFT

Use Zoom function to magnify the FFT waveform if necessary, see " Zoom the
Waveform " on P31.

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