Measurement Computing Data Translation DT3034, User Manual

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Chapter 6
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Figure 23 illustrates the same example using triggered scan mode (either a software or
external retrigger source). The multiscan count is 2 indicating that the channel list will be
scanned twice per trigger or retrigger. In this example, post-trigger analog input data is
acquired on each clock pulse of the A/D sample clock until the channel list has been scanned
twice; then, the board waits for the retrigger event. When the retrigger event occurs, the board
scans the channel list twice more, acquiring data on each pulse of the A/D sample clock. The
process repeats continuously with every specified retrigger event.
Figure 23: Continuous Post-Trigger Mode with Triggered Scan
Pre-Trigger Acquisition
Use pre-trigger acquisition mode when you want to acquire data before a specific external
event occurs.
Using software, specify the following parameters:
• The dataflow as ContinuousPreTrigger.
• The pre-trigger source as Software.
• The post-trigger source as the external digital (TTL) trigger or the external analog
threshold trigger.
• If you are using triggered scan mode, the retrigger source as the software retrigger.
Refer to page 76 for more information on the supported conversion modes; refer to page 79 for
information on the supported trigger sources.
Note: When using pre-trigger acquisition, you cannot use an external retrigger in triggered
scan mode; refer to page 77 for more information on triggered scan mode.
Pre-trigger acquisition starts when you start the operation and stops when the board detects
the selected post-trigger source, indicating that the first post-trigger sample was acquired (this
sample is ignored).
Post-trigger event occurs;
post-trigger data acquired
for two scans of the CGL.
Chan 0
Chan 1
Chan 2 Chan 0
Chan 1
Chan 2
A/D
Sample
Clock
Chan 0
Chan 1
Chan 2 Chan 0
Chan 1
Chan 2
Retrigger event occurs;
post-trigger data acquired for
two scans of the channel list.
Board waits for
retrigger event.