Agilent Technologies 54622A User Manual page 40

Front-Panel Overview
Important Oscilloscope Considerations
Peak Detect acquire mode In Peak Detect acquisition mode, any noise,
peak, or signal wider than 5 ns will be displayed, regardless of sweep speed. In
Normal acquisition mode, at sweep speeds faster than 2 µs/div, you would see
a 5-ns peak, so peak detect has no effect at sweep speeds faster than 2 µs/div.
Using Peak Detect and infinite persistence together is a powerful way to find
spurious signals and glitches.
Average acquire mode Averaging is a way to pull a repetitive signal out of
noise. Averaging works better than either a bandwidth limit or a brightness
control because the bandwidth is not reduced.
The simplest averaging is smoothing (number of averages = 1). For example,
the sample rate at a Time/Div setting of 2 ms/div allows the extra 5-ns samples
to be smoothed together, smoothing the data into one sample, which is then
displayed. As with Peak Detect, smoothing has no effect at less than 2 µs/div.
Smoothing works on a single acquisition (even untriggered and single-shot).
Averaging (number of averages > 1) needs a stable trigger, because in this mode
multiple acquisitions are averaged together. See the "MegaZoom Concepts and
Oscilloscope Operation" chapter for more information about smoothing.
Realtime acquire mode
In Realtime mode, the oscilloscope acquires all of the waveform samples during
one trigger event. To accurately reproduce a sampled waveform, the sample
rate (200 MSa/s for single channel or 100 MSa/s with channel pairs 1 and 2, 3
and 4, or pod 1 and pod 2 running) should be at least four times the highest
frequency component of the waveform. If not, it is possible for the
reconstructed waveform to be distorted or aliased. Aliasing is most commonly
seen as jitter on fast digital edges.
Use Realtime to capture infrequent triggers, unstable triggers, or complex
changing waveforms, such as eye diagrams. Realtime mode is only necessary
at sweep speeds of 200 ns/div and faster.
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