Keysight Technologies DSO-X 2014A, User Manual

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Reference
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Keysight InfiniiVision 2000 X-Series Oscilloscopes User's Guide 323
CSV and ASCII XY file structure
In CSV or ASCII XY format the Length control selects the number of points per
segment. All segments are contained in the CSV file or in each ASCII XY data file.
For example: If the Length control is set to 1000 points, there will be 1000 points
(rows in the spreadsheet) per segment. When saving all segments there are three
header rows, so the data for the first segment starts at row 4. The second
segment's data starts at row 1004. The time column shows the time since the
trigger on the first segment. The top row shows the selected number of points per
segment.
BIN files are a more efficient data transfer format than CSV or ASCII XY. Use this
file format for fastest data transfer.
Minimum and Maximum Values in CSV Files
If you are running a Minimum or Maximum measurement, the minimum and
maximum values shown in the measurement display may not appear in the CSV
file.
Explanation: When the oscilloscope's sample rate is 4 GSa/s, a sample will be taken every
250 ps. If the horizontal scale is set to 10 us/div, there will be 100 us of data
displayed (because there are ten divisions across the screen). To find the total
number of samples the oscilloscope will take:
100 us x 4 GSa/s = 400K samples
The oscilloscope is required to display those 400K samples using 640 pixel
columns. The oscilloscope will decimate the 400K samples to 640 pixel columns,
and this decimation keeps track of the min and max values of all the points that
are represented by any given column. Those min and max values will be displayed
in that screen column.
A similar process is used to reduce the acquired data to produce a record usable
for various analysis needs such as measurements and CSV data. This analysis
record (or measurement record ) is much larger than 640 and may in fact contain
up to 65536 points. Still, once the # of acquired points > 65536, some form of
decimation is required. The decimator used to produce a CSV record is configured
to provide a best-estimate of all the samples that each point in the record
represents. Therefore, the min and max values may not appear in the CSV file.