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Acquiring Waveforms
3-48
CSA7000 Series, TDS7000 Series, & TDS6000 Series Instruments User Manual
Consider the mode that you want to use to acquire data:
Automatic Selection. Fast Acquisitions automatically selects record length and
sample rate to optimize the displayed image by optimizing live time and
minimizing dead time. Fast Acquisitions selects the sample rates and record
lengths and compresses them to 500 pixels to produce the maximum display
content.
Waveform Capture Rate. Figures 3--13 and 3--14 illustrate how Fast Acquisitions
mode differs from the normal acquisition mode used by digital storage instru-
ments. Note that normal mode follows a “capture waveform-digitize waveform-
update waveform memory-display waveform” cycle. Normal mode misses short
term events occurring during the long dead times. Typical waveform capture
rates are 50 waveforms per second.
Fast Acquisitions mode increases the waveform capture rate to up to 400,000
waveforms per second, updating the waveform array many times between
displays. This very fast capture rate greatly increases the probability that runts,
glitches, and other infrequent events will accumulate in waveform memory. The
instrument then displays the waveform at the normal display rate. You can
control the waveform intensity using adjustable or automatic brightness (see To
adjust the intensity on page 3--53 for more information).
Fast Acquisitions mode adds intensity or gray scale information, like an analog
instrument, to each point in the waveform array. The waveform array is a three
dimensional array, two dimensions of display pixels and a third dimension of
pixel values. Display pixel values are incremented each time they are written by
a waveform acquisition.
Using Fast Acquisitions