You can configure the data rate at which your DAQ device acquires data by
customizing the data ranges and setting the values for analog (slow, medium, and fast)
and digital data rate levels. For devices that support downsampling, you can
use an anti-aliased filter to downsample at 100 Hz.
Complete the following steps to configure the available data rates for your DAQ device:
- Click the Configure Data Rates button
on the toolbar, or click
Configure from the Data Rate
Level pull-down selector.
- Specify each frequency in Hz or s (seconds, for intervals) for the desired slow,
medium, fast, counter, or digital rates. Available data rate types vary by
- Click Done to apply the rates for the module.
You can configure any
analog input device to use Slow,
Medium, or Fast data rates.
Counter input modules, however, require the use of the data rate resource that is
assigned to the Medium data rate level. If a counter input
module is added to a chassis and any module(s) are using the
Medium data rate level, you will be prompted to change
the data rate on the affected module(s) in the chassis to use the
Slow or Fast data rate.
Why is my module not sampling at the
rate I specified?
The data rate for your module may be different than the
rate you configure for one of the following reasons:
- Modules support specific rates—You can configure your module to sample at almost any rate,
but the limitations of the hardware itself may prevent it from sampling at
that rate. If your module does not support the rate you configure,
FlexLogger coerces it to the closest supported rate.
The coerced rate
is faster than the rate you specify. For example, if you configure 11 Hz
for a module that supports 10 Hz and 20 Hz, FlexLogger uses 20
- Modules sample at the lowest common rate—If you configure multiple modules in the same
chassis to the same rate and they support different data rates, FlexLogger
sets a common, supported rate. Using a common rate ensures data is not
missed and is synchronized. For example, if you have a NI-9219 and NI-9236
set to Medium (200 Hz), the NI-9236 cannot sample slow enough to meet the
200 Hz configuration. This results in both modules using the actual rate of
about 793 Hz because it is the common rate closest to the rate you
To ensure a module uses a supported rate you configure, you must either
set your modules in the same chassis to different timing rates or separate the
modules into different chassis.
my module say the rate is downsampled?
Many modules support downsampling
in software to meet a lower data rate than the modules support. Downsampling occurs
when all of the modules set to the same rate support downsampling. The available
downsampling rate is 100 Hz.
Why is my module rate not
If your module meets the requirements, but is not
downsampling, check the following items:
- An existing downsampling preview feature interferes with the default, anti-aliased
downsampling filter—Navigate to Enable downsampling from a coerced
hardware sample rate to slower sample rate feature is
and ensure the
The existing preview
feature supports arbitrary data rates, but does not provide
- C Series Slow Sample Devices do not support downsampling—Refer to C Series Device Groupings in the NI-DAQmx Manual for a list of
slow sample devices. If you have one slow sample device set to the same rate
as modules that support downsampling, it prevents downsampling for all of