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Functional Description
4-Channel SPO Digital Oscilloscopes
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And using the
“Y1” manual cursor we can determine the amplitude (Vrms)
Y1=316mVrms
≈ (896mV/2)x0,707 = 316,7mVrms)
3) Selecting the
FFT window
The FFT window reduces spectral leakage in the FFT spectrum. The
FFT
assumes that the Y(t) waveform repeats indefinitely. With an integer number of
cycles, the Y(t) waveform starts and ends at the same amplitude and there are
no discontinuities in the signal shape. A non-integer number of cycles in the Y(t)
waveform causes the signal start and end to be at different amplitudes. The
transition between the start and end points causes discontinuities in the signal
that introduce high frequency transients.
Window
Speciality
Adapted to
Rectangular
Best frequency resolution,
worst magnitude resolution.
This is essentially the same
as no window.
Symmetric transients or
bursts.
Equal amplitude sine
waves with fixed
frequency. Broadband
ramdon noise with
relatively slowly varying
spectrum.
Hanning
Hamming
Better frequency resolution
and poorer magnitude
accuracy than Rectangular.
Hamming has slightly better
frequency resolution than
Hanning.
Sine, periodic, and narrow-
band random noise.
Asymmetric transient or
bursts.
Blackman
Best magnitude and worst
frequency resolution.
Single frequency
waveforms, to find higher
order harmonics