Chapter 3
Using the NI PXI-4204
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Adjusting Timing and Triggering
There are several timing properties that you can configure either through
the DAQ Assistant or programmatically using function calls or property
nodes in your application. If you create a task in the DAQ Assistant, you
still can modify the timing properties of the task programmatically in your
application.
When programmatically adjusting timing settings, you can set the task to
acquire continuously, acquire a buffer of samples, or acquire one point at a
time. For continuous and buffered acquisitions, you can set the acquisition
rate and the number of samples to read. By default, the clock settings are
automatically set by an internal clock based on the requested sample rate.
You also can select advanced features, such as clock settings, that specify
an external clock source, internal routing of the clock source, or select the
active edge of the clock signal.
Configuring Channel Properties
All of the different ADEs used to configure the NI PXI-4204 access an
underlying set of NI-DAQmx properties. Table 3-3 lists some of the
properties that configure the NI PXI-4204. You can use this list to
determine what kinds of properties you need to set to configure the device
for your application. If you created the task and channels using the DAQ
Assistant, you can still modify the channel properties programmatically.
For a complete list of NI-DAQmx properties, refer to your ADE help file.
Table 3-3.
NI-DAQmx Properties
Property
Short Name
Description
Analog Input»
General Properties»
Input Configuration»
Coupling Property
AI.Coupling
DC—Allows NI-DAQmx to
measure the input signal.
GND—Removes the signal
source from the measurement
and measures only ground.
Analog Input»General
Properties»Filter»Analog
Lowpass»Cutoff Frequency
AI.Lowpass.CutoffFreq
Specifies in hertz the frequency
corresponding to the –3 dB cutoff
of the filter. You can specify either
6.0 or 10000.0.
