Programming instructions

Chapter 8 Controlling Your Acquisition with Triggers
LabVIEW Data Acquisition Basics Manual 8-4
© National Instruments Corporation
Digital Triggering Examples
A common example of digital triggering in LabVIEW is the Acquire N
Scans Digital Trig VI, found in
labview\examples\daq\anlogin\
anlogin.llb
. This VI, as shown Figure 8-3, uses the Intermediate VIs to
perform a buffered acquisition, where LabVIEW stores data in a memory
buffer during acquisition. After the acquisition completes, the VI retrieves
all the data from the memory buffer and displays it. Figure 8-3 shows the
block diagram of this example VI.
Figure 8-3.
Block Diagram of the Acquire N Scans Digital Trig VI
For more information on buffered acquisitions, refer to Chapter 7,
Buffering Your Way through Waveform Acquisition
.
You must tell your device the conditions on which to start acquiring data.
For this example, the
choose trigger type
Boolean should be set to
START
OR STOP TRIGGER
. You should only use the
START & STOP TRIGGER
when you have two triggers: start and stop. In addition, if you use a
DAQ device with PFI lines (e.g., E-series 5102 devices), you can specify
the trigger signal condition in the
trigger channel
control in the
analog
chan & level
cluster. For more information on valid trigger channel names,
refer to the AI Trigger Config VI description, in Chapter 18,
Advanced
Analog Input VIs
, of the
LabVIEW Function and VI Reference Manual
, or
to the LabVIEW
Online Reference
, available by selecting
Help»Online
Reference…
. This chapter only describes applications that use one digital
trigger. For more information on two-triggered applications, look at the
description for the AI Trigger Config VI, found in Chapter 18,
Advanced
Analog Input VIs
, in the
LabVIEW Function and VI Reference Manual
, or