Chapter 2
Analog Input
©
National Instruments Corporation
2-37
Using an Analog Source
When you use an analog trigger source, the internal sample clock pauses
when the Analog Comparison Event signal is low and resumes when the
signal goes high (or vice versa). Refer to Chapter 10,
, for more
information on analog triggering.
Note
Pause triggers are only sensitive to the level of the source, not the edge.
AI Sample Clock Signal
You can use the AI Sample Clock (ai/SampleClock) signal to initiate a set
of measurements. Your E Series device samples the AI signals of every
channel in the scan list once for every ai/SampleClock. A measurement
acquisition consists of one or more samples.
The source of the ai/SampleClock signal can be internal or external. You
specify whether the measurement sample begins on the rising edge or
falling edge of the ai/SampleClock signal.
Using an Internal Source
By default, ai/SampleClock is created internally by dividing down the
ai/SampleClockTimebase. Refer to the
AI Sample Clock Timebase Signal
section for more information.
Several other internal signals can be routed to the sample clock. Refer to
Device Routing in MAX
in the
NI-DAQmx Help
or the
LabVIEW 8.x Help
for more information.
Using an External Source
You can use a signal connected to any PFI or RTSI <0..6> pin as the source
of ai/SampleClock. Figure 2-24 shows the timing requirements of the
ai/SampleClock source.
