Programming instructions

Chapter 7 Buffering Your Way through Waveform Acquisition
© National Instruments Corporation 7-11 LabVIEW Data Acquisition Basics Manual
Figure 7-10.
Continuously Acquiring Data with the Intermediate VIs
Because this uses Intermediate VIs, you also can control parameters such
as triggering, coupling, and additional hardware.
Asynchronous Continuous Acquisition Using DAQ Occurrences
The main advantage of the last section is that you are free to manipulate
your data between calls to
AI Read.vi
. One limitation, however,
is that the acquisition is synchronous. This means that once you call
AI Read.vi
, you cannot perform any other tasks until
AI Read.vi
returns your acquired data. If your DAQ device is still busy collecting data,
you will have to sit idle until it finishes.
If you need the efficiency of not having to wait for
AI Read.vi
, then
asynchronous acquisition is for you. You can acquire asynchronous
continuous data from multiple channels using the same intermediate
DAQ VIs by adding DAQ Occurrences. Figure 7-11 shows an
example of how to do this. This is the diagram of the Cont Acq&Chart
(Async Occurrence) VI, located in
labview\examples\daq\
anlogin\anlogin.llb
. Notice that it is very similar to Figure 7-10.
The difference is that here you will use the DAQ Occurrence Config VI
and the Wait on Occurrence function to control the reads. The first
DAQ Occurrence Config VI sets the DAQ Event. In this example the
DAQ Event
is to
set the occurrence every time a number of
scans is acquired equal to the value of general value A
,