In equivalent-time sampling mode, the HP 54720 time base resolution is
limited only by the resolution of the interpolator hardware. Each sample is
plotted on the screen at the point corresponding to the precise time
determined by the time base hardware, limited to the resolution of the
display. In the internal memory of the HP 54720, the full time resolution for
each sample is retained, regardless of memory depth. The automatic
measurement routines and the waveform tracking markers in the HP 54720
use this high-resolution time data. Therefore equivalent-time sampling gives
better resolution and accuracy for time-interval measurements. Of course
equivalent-time sampling cannot be used for single-shot measurements.
Bandwidth affects the accuracy of time-interval measurements, and the
HP 54720 has the highest bandwidth when operated in the equivalent-time
sampling mode with the HP 54711A plug-in.
Advantages of equivalent-time sampling include the following:
•
Higher bandwidth than real-time sampling
•
The range of negative time is not limited by the combination of sampling
rate and memory depth
•
The time-interval measurement resolution is not limited by the memory
depth
•
Not susceptible to aliasing on repetitive signals
The major disadvantage of equivalent-time sampling is that it is not suitable
for single-shot measurements
Measurements
Time-interval measurements
13–48
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