Agilent Technologies Infiniium 90000 Series Programmer's Manual page 932

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Waveform Commands
The WAVeform subsystem is used to transfer waveform data between a
computer and the oscilloscope. It contains commands to set up the
waveform transfer and to send or receive waveform records to or from the
oscilloscope.
Data Acquisition
When data is acquired using the DIGitize command, the data is placed in
the channel or function memory of the specified source. After the DIGitize
command executes, the oscilloscope is stopped. If the oscilloscope is
restarted by your program or from the front panel, the data acquired with
the DIGitize command is overwritten.
You can query the preamble, elements of the preamble, or waveform data
while the oscilloscope is running, but the data will reflect only the current
acquisition, and subsequent queries will not reflect consistent data. For
example, if the oscilloscope is running and you query the X origin, the
data is queried in a separate command, it is likely that the first point in
the data will have a different time than that of the X origin. This is due to
data acquisitions that may have occurred between the queries. For this
reason, Agilent Technologies does not recommend this mode of operation.
Instead, you should use the DIGitize command to stop the oscilloscope so
that all subsequent queries will be consistent.
Function and channel data are volatile and must be read following a DIGitize command or
N O T E
the data will be lost when the oscilloscope is turned off.
Waveform Data
The waveform record consists of two parts: the preamble and the
and Preamble waveform data. The waveform data is the actual sampled data acquired for
the specified source. The preamble contains the information for
interpreting the waveform data, including the number of points acquired,
the format of the acquired data, and the type of acquired data. The
preamble also contains the X and Y increments, origins, and references for
the acquired data.
The values in the preamble are set when you execute the DIGitize
command. The preamble values are based on the current settings of the
oscilloscope's controls.
Data Conversion
Data sent from the oscilloscope must be scaled for useful interpretation.
The values used to interpret the data are the X and Y origins and X and
Y increments. These values can be read using the :WAVeform:XORigin?,
WAVeform:YORigin?, WAVeform:XINCrement?, and WAVeform:YINCreament?
queries.
Conversion from
To convert the waveform data values (essentially A/D counts) to
Data Values to real- world units, such as volts, use the following scaling formulas:
Units
Y- axis Units = data value x Yincrement + Yorigin (analog channels) X- axis
Units = data index x Xincrement + Xorigin,
starts at zero: 0, 1, 2, ..., n- 1.
932 Agilent Infiniium 90000 Series Oscilloscopes Programmer's Reference
where the data index