Pan And Zoom - HP 54645A User's And Service Manual

MegaZoom Concepts

Pan and Zoom

Pan and Zoom
The ability to pan (move horizontally) and zoom (expand or compress
horizontally) an acquired waveform is important because of the additional
insight it can reveal about the captured waveform. This additional insight is
often gained from seeing the waveform at different levels of abstraction. You
may want to view both the big picture and the specific little picture details.
The ability to examine scope waveform detail after the waveform has been
acquired is a benefit generally associated with digital oscilloscopes. Often this
is simply the ability to freeze the display for the purpose of measuring with
cursors or printing the screen. Some digital scopes go one step further by
including the ability to further examine the signal details after acquiring them
by panning and zooming through the waveform.
There is no limit imposed on the zoom ratio between the sweep speed used
to acquire the data and the sweep speed used to view the data. There is,
however, a useful limit. This useful limit is somewhat a function of the signal
you are analyzing.
In normal or average display mode, with vectors (connect-the-dots) off, you
can zoom in to the point where there are no samples on the screen.
Obviously, this is far beyond the useful limit. Likewise, with vectors on, you
can see the linear interpolation between the points, but again, this is of very
limited value.
Zoom
The screen will contain a relatively good display if you zoom in horiontally by a
factor of 1000 and zoom in vertically by a factor of 10 to display the information
from where it was acquired. Remember that you can only make automatic
measurements on displayed data.
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