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Posttriggered data acquisition allows you to view only data that is acquired after a trigger event
is received. A typical posttriggered DAQ sequence is shown in Figure 4-14. The sample counter
is loaded with the specified number of posttrigger samples, in this example, five. The value
decrements with each pulse on AI Sample Clock, until all desired samples have been acquired.
Figure 4-14.
Posttriggered Data Acquisition Example
Pretriggered data acquisition allows you to view data that is acquired before the trigger of
interest, in addition to data acquired after the trigger. Figure 4-15 shows a typical pretriggered
DAQ sequence. AI Start Trigger (ai/StartTrigger) can be either a hardware or software signal. If
AI Start Trigger is set up to be a software start trigger, an output pulse appears on the
ai/StartTrigger line when the acquisition begins. When the AI Start Trigger pulse occurs, the
sample counter is loaded with the number of pretriggered samples, in this example, four. The
value decrements with each pulse on AI Sample Clock.The sample counter is then loaded with
the number of posttriggered samples, in this example, three.
Figure 4-15.
Pretriggered Data Acquisition Example
If an AI Reference Trigger (ai/ReferenceTrigger) pulse occurs before the specified number of
pretrigger samples are acquired, the trigger pulse is ignored. Otherwise, when the AI Reference
Trigger pulse occurs, the sample counter value decrements until the specified number of
posttrigger samples have been acquired.
MIO X Series devices feature the following analog input timing signals:
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AI Sample Clock Timebase Signal
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AI Convert Clock Timebase Signal
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Summary of Contents for DAQ X NI 634 Series
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