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Waveform Commands
Waveform Commands
The WAVeform subsystem is used to transfer waveform data between a computer and the
analyzer. It contains commands to set up the waveform transfer and to send or receive wave-
form records to or from the analyzer.
Data Acquisition When the 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, the analyzer is
stopped. If the analyzer is restarted over GPIB or 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 analyzer is running, but the data will reflect only the current acqui-
sition, and subsequent queries will not reflect consistent data. For example, if the analyzer is
running and you query the X origin, the data is queried in a separate GPIB command, and 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 does not recommend this mode of operation. Instead, you should use the DIGitize
command to stop the analyzer so that all subsequent queries will be consistent. Function data
is volatile and must be read following a DIGitize command or the data will be lost when the
analyzer is turned off.
Waveform Data
and Preamble
The waveform record consists of two parts: the preamble and the waveform data. The wave-
form data is the actual sampled data acquired for the specified source. The preamble con-
tains 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 settings of controls in the ACQuire subsystem. Although you can change pream-
ble values with a GPIB computer, you cannot change the way the data is acquired. Changing
the preamble values cannot change the type of data that was actually acquired, the number of
points actually acquired, etc.
NOTE The waveform data and preamble must be read or sent using two separate commands: WAVeform:DATA and
WAVeform:PREamble. When changing any waveform preamble values, be sure to set the points in the preamble
to the same value as the actual number of points in the waveform. Otherwise, inaccurate data will result.
Data Conversion Data sent from the analyzer must be scaled for useful interpretation. The values used to
interpret the data are the X and Y origins, X and Y increments, and X and Y references. These
values can be read from the waveform preamble.