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4.Advanced User Guidebook
22
Kaiser
The frequency resolution whe
n 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.
Bartlett
The Bartlett window is a slightly narrower variant
of the triangular window, with zero weight at both
ends.
Notes for using FFT
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 aliasing. So pay more
attention to the relation between the frequency being sampled and measured.
Use Vertical Position and Scale Knobs
1. The Vertical Position knob is used to adjust the vertical positions of the
waveforms.
The analytic resolution of this control knob changes with the vertical division.
2. The Vertical Scale knob is used to regulate the vertical resolution of the wave
forms. The sensitivity of the vertical division steps as 1-2-5.
The vertical position and vertical resolution is displayed at the left bottom corner of
the screen (see Figure 4-1).
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