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6-7
not need to divide the signal, then you should use DI Sample Clock rather than DI Sample Clock
Timebase.
DI Start Trigger Signal
Use the DI Start Trigger (di/StartTrigger) signal to begin a measurement acquisition. A
measurement acquisition consists of one or more samples. If you do not use triggers, begin a
measurement with a software command. Once the acquisition begins, configure the acquisition
to stop:
•
When a certain number of points are sampled (in finite mode)
•
After a hardware reference trigger (in finite mode)
•
With a software command (in continuous mode)
An acquisition that uses a start trigger (but not a reference trigger) is sometimes referred to as a
posttriggered acquisition.
Retriggerable DI
The DI Start Trigger is configurable as retriggerable. When the DI Start Trigger is configured as
retriggerable, the timing engine generates the sample and convert clocks for the configured
acquisition in response to each pulse on a DI Start Trigger signal.
The timing engine ignores the DI Start Trigger signal while the clock generation is in progress.
After the clock generation is finished, the timing engine waits for another Start Trigger to begin
another clock generation. Figure 6-4 shows a retriggerable DI of four samples.
Figure 6-4.
Retriggerable DI
Note
Waveform information from LabVIEW does not reflect the delay between
triggers. They are treated as a continuous acquisition with constant t0 and dt
information.
Reference triggers are not retriggerable.
Using a Digital Source
To use DI Start Trigger with a digital source, specify a source and an edge. The source can be
any of the following signals:
•
PFI <0..15>
•
RTSI <0..7>
•
Counter
n
Internal Output
DI
S
t
a
rt Trigger
DI
Sa
mple Clock
Содержание DAQ X NI 634 Series
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