Keysight DSOX3012T, User Manual

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228 Keysight InfiniiVision 3000T X-Series Oscilloscopes User's Guide
13
Acquisition Control
This setting only has an effect when sweep speeds are 20 ns/div or faster. At
slower sweep speeds, there are enough sample points in a trigger (acquisition, in
other words) to render a waveform on the display.
Realtime sampling specifies that the oscilloscope produce the waveform display
from samples collected during one trigger event (that is, one acquisition).
Use Realtime sampling to capture infrequent triggers, unstable triggers, or
complex changing waveforms, such as eye diagrams.
When Realtime sampling is on (as in the default setup):
• When less than 1000 samples can be collected in the time spanned by the
screen, a sophisticated reconstruction filter is used to fill-in and enhance the
waveform display.
• If you press the [Stop] key, and pan and zoom through the waveform using the
Horizontal and Vertical controls, only the last trigger's acquisition will be
displayed.
When Realtime sampling is off (equivalent time mode):
• Instead of the reconstruction filter, a technique known as random repetitive
sampling is used to build-up and draw one waveform using multiple triggers
(acquisitions).
• Equivalent time sampling mode requires a repetitive waveform with a stable
trigger.
See Also • “Realtime Sampling and Oscilloscope Bandwidth" on page 228
Realtime Sampling and Oscilloscope Bandwidth
To accurately reproduce a sampled waveform, the sample rate should be at least
2.5 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 edges.
The maximum sample rate for the 3000T X-Series oscilloscopes is 5 GSa/s for a
single channel in a channel pair. Channels 1 and 2 constitute a channel pair, and
channels 3 and 4 constitute another channel pair. For example, the sample rate of
a 4-channel oscilloscope is 5 GSa/s when channels 1 and 3, 1 and 4, 2 and 3, or 2
and 4 are on.
Whenever both channels in a channel pair are on, the sample rate for all channels
is halved. For example, when channels 1, 2, and 3 are on, the sample rate for all
channels is 2.5 GSa/s.