User manual

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Agilent 1000 Series Oscilloscopes User’s Guide 55
5 Press Window, and continue pressing the softkey or turn the entry
knob to select the desired window:
There are four FFT windows. Each window has trade-offs between
frequency resolution and amplitude accuracy. What you want to
measure and your source waveform characteristics help determine
which window to use. Use the guidelines in Table 4 to select the best
window.
6 Press Display to toggle between a “Split” screen display and a
“Full Screen” display.
7 Press and turn the entry knob to adjust the vertical
position of the FFT waveform.
8 Press and turn the entry knob to adjust the vertical scale
of the FFT waveform.
9 Press Scale to toggle between “V
RMS
” and “dBV
RMS
” units.
Table 4 FFT Window Characteristics
Window Characteristics Best for measuring
Rectangle Best frequency resolution, worst
magnitude resolution. This is
essentially the same as no window.
Transients or bursts, the waveform
levels before and after the event are
nearly equal. Equal-amplitude sine
waves with fixed frequencies.
Broadband random noise with a
relatively slow varying spectrum.
Hanning,
Hamming
Better frequency, poorer magnitude
accuracy than Rectangular. Hamming
has slightly better frequency resolution
than Hanning.
Sine, periodic, and narrow-band
random noise. Transients or bursts
where the waveform levels before and
after the events are significantly
different.
Blackman Best magnitude, worst frequency
resolution.
Single frequency waveforms, to find
higher order harmonics.
NOTE
To display FFT waveforms with a large dynamic range, use the dBVrms scale. The dBVrms
scale displays component magnitudes using a log scale.