HP 54645A, User'S And Service Manual

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Capturing Data
In the HP 54645A Oscilloscope, an 8-bit A/D converter converts the
input waveform into an evenly-spaced series of voltage readings.
These readings are made once for each sample, and are stored into
memory in time-voltage pairs.
Main and Delayed Sweep
The delayed sweep display function magnifies the contents of sample
memory—data used by the main and delayed sweep windows is acquired on
a single acquisition; the data corresponds to the same trigger event. Using the
delayed sweep window, you can zoom in on a portion of the waveform and
examine it in greater detail. In delayed sweep, with HP 54645D, if scope
channels are on, 8 logic channels can also be on. If scope channels are off, 16
logic channels can be on.
The delayed sweep operation in the HP 54645A/D is based on HP MegaZoom
technology. Unlike analog oscilloscopes, the MegaZoom oscilloscope’s
delayed sweep is not a second acquisition, but an expansion of the same data
displayed in the main sweep. MegaZoom technology makes this possible
because of its deep memory. Also because of the deep memory in MegaZoom
technology, it is possible to capture the main display at 1 ms/div, and
redisplay the same trigger in the delayed display at 1
µ
s/div—a 1000:1 zoom
ratio.
When you enable the delayed sweep view, the oscilloscope divides the
window into two portions. The upper part shows the waveform according to
the main time base; the lower shows a small portion of the waveform
magnified according to a second time base (the delayed sweep window). In
the delayed sweep window, the Time/Div knob adjusts the magnification of
the delayed sweep portion. The delayed sweep time base must be at least
twice as fast the main time base, and can vary up to the maximum sweep
speed of 2 ns/div for HP 54645A and 5 ns/div for HP 54645D. For example, at
a main time base setting of 500
µ
s/div, the delayed sweep time base will be
adjustable from 200
µ
s/div to 5 ns/div.
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