National Semiconductor ADC081500DEV, Instruction Manual

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Histogram Plots
Histogram plots are created by counting the number of times each ADC output code appears in a dataset.
Histograms may be computed by software, or by hardware. A software histogram is computed from a
dataset which is normally 128k samples or smaller. A hardware histogram is collected directly by the
hardware, and may include millions of counts per code. The resulting histogram will show discontinuities
between comparators, gain or offset errors, and other common ADC system problems.
The Histogram plot also displays the number of codes that were never counted (missing codes), followed
by the first ten such missing codes.
Information Viewer
The information viewer is not a plot, but it displays a variety of useful information about the dataset, such
as the sampling rate, and any warnings generated by the software. You may also store comments about
the dataset here, to be saved in a WaveVision file.
Data Import and Export
The WaveVision software provides a variety of means to share data with others, in both textual and
graphical formats.
The most flexible way to import data into the software is from a tab-delimited ASCII text file. The contents
can be either a sample set or a histogram, provided with or without time information. The simplest
example of this would be a file with a single column of samples. You can open tab-delimited text files by
choosing
Open
from the
File
menu; you can interleave data from multiple columns and/or files. You can
choose
ReOpen
to reopen the same file later with the same settings (for example when you update the file
with new data),
There are a variety of ways to export data from the software:
•
Save the file as a normal WV4 (*.wv4) file. WV4 files are ASCII, tab-delimited text files. Samples
are stored one per line in a single column. You can open a WV4 file directly in a spreadsheet
program.
•
Save the file as a TXT (*.txt) file. You will produce a one- or two-column tab-delimited ASCII text
file of samples or histogram information, without the header information that is contained in a WV4
file.
•
You can export the contents of an individual plot by choosing
Export Data…
from the plot’s
Plot Actions
menu. The format of the data is always tab-delimited ASCII text.
•
You can export a plot as either a GIF (*.gif) or Encapsulated Postscript (*.eps) graphic by
choosing
Export Plot as Graphic
from the plot’s
Plot Actions
menu. GIF files are
suitable for the web or for emails. Encapsulated Postscript files are high-resolution scalable files
suitable for direct publication.