Programming instructions

Chapter 7 Buffering Your Way through Waveform Acquisition
LabVIEW Data Acquisition Basics Manual 7-4
© National Instruments Corporation
You also can acquire multiple waveforms using the Intermediate VIs.
The Intermediate VIs provide more control over your data acquisition
processes, like being able to read any part of the buffer. An example similar
to Figure 7-4 is the Acquire N Scans VI, located in
labview\examples\
daq\anlogin\anlogin.llb
. With these Intermediate Analog Input VIs,
you must wire a
taskID
to identify the DAQ operation and the set of
channels used in the acquisition and to make sure the VIs execute in the
correct order.
Figure 7-4.
Using the Intermediate VIs to Acquire Multiple Waveforms
With these VIs, not only can you configure triggering, coupling,
acquisition timing, retrieval, and additional hardware, but you also can
control when each step of the data acquisition process occurs. With
the AI Config VI, you can configure the different parameters of the
acquisition, such as the channels to be read and the size of the buffer to use.
In the AI Start VI, you specify parameters used in your program to start the
acquisition, such as number of scans to acquire, the rate at which your VI
takes the data, and the trigger settings. In the AI Read VI, you specify
parameters to retrieve the data from the data acquisition buffer. Then,
your application calls the AI Clear VI to deallocate all buffers and other
resources used for the acquisition by invalidating the
taskID
. If an error
occurs in any of these VIs, your program passes the error through the
remaining VIs to the Simple Error Handler VI, which notifies you of
the error.