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11
Acquisition Control
Memory Depth and Sample Rate
The number of points of oscilloscope memory is fixed, and there is a
maximum sample rate associated with oscilloscope's analog- to- digital
converter; however, the actual sample rate is determined by the time of
the acquisition (which is set according to the oscilloscope's horizontal
time/div scale).
sample rate = number of samples / time of acquisition
For example, when storing 50 µs of data in 50,000 points of memory, the
actual sample rate is 1 GSa/s.
Likewise, when storing 50 ms of data in 50,000 points of memory, the
actual sample rate is 1 MSa/s.
The actual sample rate is displayed in the right- side information area.
The oscilloscope achieves the actual sample rate by throwing away
(decimating) unneeded samples.
Selecting the Acquisition Mode
When selecting the oscilloscope acquisition mode, keep in mind that
samples are normally decimated at slower time/div settings.
At slower time/div settings, the effective sample rate drops (and the
effective sample period increases) because the acquisition time increases
and the oscilloscope's digitizer is sampling faster than is required to fill
memory.
For example, suppose an oscilloscope's digitizer has a sample period of
1 ns (maximum sample rate of 1 GSa/s) and a 1 M memory depth. At that
rate, memory is filled in 1 ms. If the acquisition time is 100 ms
(10 ms/div), only 1 of every 100 samples is needed to fill memory.
To select the acquisition mode:
1 Press the [Acquire] key on the front panel.
2 In the Acquire Menu, press the Acq Mode softkey; then, turn the Entry
knob to select the acquisition mode.
The InfiniiVision oscilloscopes have the following acquisition modes:
Agilent InfiniiVision 2000 X-Series Oscilloscopes User's Guide
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