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Chapter 2
Analog Input
Pretriggered Acquisition be Continuous?
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and enter the Info Code
rdcanq
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When the reference trigger occurs, the cDAQ controller continues to write samples to the buffer
until the buffer contains the number of posttrigger samples desired. Figure 2-3 shows the final
buffer.
Figure 2-3.
Reference Trigger Final Buffer
Using a Digital Source
To use Reference Trigger with a digital source, specify a source and a rising or falling edge.
Either PFI or one of several internal signals on the cDAQ controller can provide the source.
Refer to the
Device Routing in MAX
topic in the
NI-DAQmx Help
or the
LabVIEW Help
for more
information.
Using an Analog Source
Some C Series modules can generate a trigger based on an analog signal. In NI-DAQmx, this is
called the Analog Comparison Event.
When you use an analog trigger source, the acquisition stops on the first rising or falling edge of
the Analog Comparison Event signal, depending on the trigger properties.
Note
Depending on the C Series module capabilities, you may need two modules
to utilize analog triggering.
Routing the Reference Trigger Signal to an Output Terminal
You can route Reference Trigger to any output PFI terminal. Reference Trigger is active high by
default.
Reference Trigger
Pretrigger
Sa
mple
s
Complete B
u
ffer
Po
s
ttrigger
Sa
mple
s
