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The FD-11613 is specifically designed for measuring signals that vary slowly. Because of their
slow rate, it is not appropriate for these devices to constrain the AI Sample Clock to operate at
or slower than their maximum rate. When using the FD-11613 in the same task as faster
devices, the maximum Sample Clock rate can run faster than the maximum rate for the device.
When operating at a rate faster than the it can support, the FD-11613 returns the same point
repeatedly, until a new conversion completes. In a hardware-timed task, the first point is
acquired when the task is committed. The second point is acquired after the start trigger as
shown in the following figure.
Figure 12. Sample Clock Timing Example
Start Trigger
Data from
A/D Conversion
Sample Clock
Data Returned
to AI Task
1st A/D Conversion
2nd A/D Conversion
3rd A/D Conversion
A
B
C
A
A
A
B
B
B
C
AI Sample Clock Timebase Signal
The AI Sample Clock Timebase signal is divided down to provide a source for Sample Clock.
AI Start Trigger Signal
Use the Start Trigger signal to begin a measurement acquisition. A measurement acquisition
consists of one or more samples. If you do not use triggers, begin a measurement with a
software command. Once the acquisition begins, configure the acquisition to stop in one of the
following ways:
•
In finite mode, when a certain number of points has been sampled
•
In continuous mode, with a software command
You can specify a default delay from the Start Trigger to the first sample.
Use the Start Trigger signal with a time source, by specifying a specific time in NI-DAQmx.
Refer to the
Time Triggering
topic in the
NI-DAQmx Help
for more information on accessing
time-based features in the NI-DAQmx API.
Time-Based Triggers
FieldDAQ devices feature automatic network-based synchronization with compatible
networks and 802.1AS-capable NI Linux Real-Time controllers. The SYNC logo on the
device front panel indicates that the device is capable of hardware-based synchronization over
a network.
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FD-11613 User Guide