7 Acquisition Modes
232 InfiniiVision 7000B Series Oscilloscopes User’s Guide
Realtime Sampling Option
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.
Realtime sampling can be turned on in Normal, Peak Detect, or High
Resolution acquisition modes. It cannot be turned on when the acquisition
mode is Averaging.
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:
• The oscilloscope produces the waveform display from samples collected
from multiple acquisitions. In this case, the reconstruction filter is not
used.
Realtime Sampling and Oscilloscope Bandwidth
To accurately reproduce a sampled waveform, the sample rate 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 edges.
The maximum sample rate for 350 MHz bandwidth oscilloscopes is
2GSa/s.
The maximum sample rate for 1 GHz and 500 MHz bandwidth
oscilloscopes is 4 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
4 GSa/s when channels 1 and 3, 1 and 4, 2 and 3, or 2 and 4 are on.
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