Agilent Technologies InfiniiVision 3000 X- Series, Advanced Training Manual, Page: 32 / 128

32 3000 X-Series Oscilloscopes Advanced Training Guide
2
Oscilloscope Familiarization Labs
When we attempt to capture multiple RF bursts that are separated by
4.0 ms, the scope under- samples and shows varying amplitudes of the
signal as shown in
Figure 16 . Again, this is because the scope
automatically reduced its sample rate in order to capture a longer
time- span with its limited amount of acquisition memory. Let’s now
zoom- in and take a closer look at this under- sampled data.
10 Press
[Run/Stop]
to stop repetitive acquisitions (
[Run/Stop]
key will turn
red).
11
Now set the scope’s timebase to 200.0 ns/div .
After acquiring the waveform at the slower timebase setting, and then
zooming in, we can clearly see that our waveform was under- sampled as
evidenced by the triangular shaped waveforms shown in
Figure 17 .
Remember, this should be a burst of sine waves.
Although using the scope’s Peak Detect mode would provide us with a
more accurate measure of the peak amplitudes of each burst when
captured at the slower timebase setting (
Figure 16 ), we would see that the
waveform would still be under- sampled after zooming in on a stored trace.
Another solution would be to purchase a scope with much deeper
memory. Let’s now use the scope’s Segmented Memory acquisition mode to
capture multiple bursts with high resolution.
12 Press
[Run/Stop]
to begin repetitive acquisitions again with the timebase
still set at 200.0 ns/div (
[Run/Stop]
should turn green).
Figure 17 Zooming in reveals an under-sampled waveform.