AI Pause Trigger Signal
You can use the Pause Trigger to pause and resume a measurement acquisition. The internal
sample clock pauses while the external trigger signal is active and resumes when the signal is
inactive. You can program the active level of the pause trigger to be high or low.
Using a Digital Source
To use the Pause Trigger, specify a source and a polarity. The source can be either from PFI or
one of several other internal signals on your cRIO controller. 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 internal sample clock pauses when the Analog
Comparison Event signal is low and resumes when the signal goes high (or vice versa).
Note
Pause triggers are only sensitive to the level of the source, not the edge.
AI Convert Clock Signal Behavior For Analog Input Modules
Refer to the Scanned Modules, Simultaneous Sample-and-Hold Modules, Delta-Sigma
Modules, and Slow Sample Rate Modules sections for information about the AI Convert Clock
signal and C Series analog input modules.
Scanned Modules
Scanned C Series analog input modules contain a single A/D converter and a multiplexer to
select between multiple input channels. When the module interface receives a Sample Clock
pulse, it begins generating a Convert Clock for each scanned module in the current task. Each
Convert Clock signals the acquisition of a single channel from that module. The Convert
Clock rate depends on the module being used, the number of channels used on that module,
and the system Sample Clock rate.
The driver chooses the fastest conversion rate possible based on the speed of the A/D
converter for each module and adds 10 µs of padding between each channel to allow for
adequate settling time. This scheme enables the channels to approximate simultaneous
sampling. If the AI Sample Clock rate is too fast to allow for 10 µs of padding, NI-DAQmx
selects a conversion rate that spaces the AI Convert Clock pulses evenly throughout the
sample. NI-DAQmx uses the same amount of padding for all the modules in the task. To
explicitly specify the conversion rate, use the
ActiveDevs
and
AI Convert Clock Rate
properties using the
DAQmx Timing
property node or functions.
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cRIO-904x User Manual
