HP 16534A User Reference page 32

Time Base Functions
s/Div Field
At sweep speeds of 100 ms/div and slower, the time to acquire the 32768
sample points for acquisition memory is greater than 1 second. At these
sweep speeds the screen displays the message "Waiting for Prestore" when
acquiring the sample points prior to the trigger. It displays the message
"Waiting for Poststore" when acquiring the sample points after the trigger.
These messages advise you that the oscilloscope is still actively acquiring
data. Acquisition time and sample rate, as they compare to sweep time, are
shown in the table at the end of this chapter.
The default value for the s/Div field is 500 ns.
Zooming (Acquisition Stopped)
When acquisitions are stopped, the oscilloscope displays the sample points
stored in acquisition memory on the screen. When you change the sweep
speed, the new screen display is a different presentation of the data retained
in acquisition memory when acquisitions were stopped. Presenting the same
data in a different form (zooming) is normally used on a waveform acquired
in Single mode.
Zooming while in repetitive mode will change the sample rate and the
display because the hardware is reprogrammed between acquisitions in
response to the new timebase settings. Zooming is done by adjusting the
value in the s/Div field. It causes the waveform to either expand horizontally
(decrease sweep time value) or compress horizontally (increase sweep time
value).
When used in conjunction with panning (see "Delay Field"), zooming is very
useful in displaying waveforms.
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