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© National Instruments Corporation 15 NI cDAQ-9172 User Guide and Specifications
be Continuous?, for more information. To access this KnowledgeBase,
go to
ni.com/info and enter the info code rdcanq.
When the reference trigger occurs, the NI cDAQ-9172 continues to write
samples to the buffer until the buffer contains the number of posttrigger
samples desired. Figure 9 shows the final buffer.
Figure 9. Reference Trigger Final Buffer
Using a Digital Source
To use ai/ReferenceTrigger with a digital source, specify a source and an
edge. Either PFI or one of several internal signals on the NI cDAQ-9172
chassis can provide the source. Refer to Device Routing in MAX in the
NI-DAQmx Help or the LabVIEW Help in version 8.0 or later for more
information.
The NI-DAQmx Help is available after installation from Start»Programs»
National Instruments»NI-DAQ»NI-DAQmx Help. To view the
LabVIEW Help, in version 8.0 or later, select Help»Search the LabVIEW
Help in LabVIEW. Alternately, to download the LabVIEW Help, go to
ni.com/manuals.
You also can specify whether the measurement acquisition stops on the
rising edge or falling edge of ai/ReferenceTrigger.
Using an Analog Source
Some C Series I/O 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.
Reference Trigger
Pretrigger Samples
Complete Buffer
Posttrigger Samples