Programming the FieldDAQ Device
You can use the FieldDAQ device in the following analog input applications:
•
Finite acquisition
•
Continuous acquisition
The FieldDAQ device features the following timing and triggering signals:
•
•
AI Sample Clock Timebase Signal
•
•
For more information about programming analog input applications and triggers in software,
refer to the
NI-DAQmx Help
or the
LabVIEW Help
for more information.
AI Sample Clock Signal
A sample consists of one reading from each channel in the AI task. Sample Clock signals the
start of a sample of all analog input channels in the task. Refer to the following figure for
sample clock source options.
Figure 19. AI Sample Clock Timing Options
Programmable
Clock
Divider
AI Sample Clock
Timebase
AI Sample
Clock
13.1072 MHz Timebase
12.8 MHz Timebase
12.288 MHz Timebase
10.24 MHz Timebase
The FD-11634 is considered a Delta-Sigma device; it contains multiple A/D converters that
require a high-frequency oversample clock to produce accurate, synchronized data. The
FieldDAQ device returns a sample on every Sample Clock pulse.
The oversample clock is used as the AI Sample Clock Timebase. The FieldDAQ device
supplies 13.1072 MHz, 12.8 MHz, 12.288 MHz, and 10.24 MHz timebases. By default,
NI-DAQmx automatically chooses the most suitable timebase for a selected data rate.
The FieldDAQ device automatically issues a synchronization pulse to each bank that resets
their ADCs at the same time. You can also specify a specific time for the synchronization
pulse to occur. Because of the filtering used in the Delta-Sigma FieldDAQ device A/D
converters, these devices exhibit a fixed input delay relative to non-Delta-Sigma devices in the
system. This input delay is specified in the
FD-11634 Specifications
.
When using multiple FieldDAQ devices in a task that contains channels for a Delta-Sigma
device, such as the FD-11634, ensure that one of those channels is the first in your channel list.
FD-11634 User Guide
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© National Instruments
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