Acquisition Control 12
Keysight InfiniiVision 2000 X-Series Oscilloscopes User's Guide 161
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:
• Normal — at slower time/div settings, normal decimation occurs, and there is
no averaging. Use this mode for most waveforms. See “Normal Acquisition
Mode" on page 162.
• Peak Detect — at slower time/div settings, the maximum and minimum
samples in the effective sample period are stored. Use this mode for
displaying narrow pulses that occur infrequently. See “Peak Detect
Acquisition Mode" on page 162.
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