Why Does My NI 9237 Not Sample Below 3.846 kHz?Hardware: CompactRIO>>Analog Input Modules>>NI 9237
Problem: I am trying to program my NI 9237, in a CompactDAQ, to use a sample rate below 3.846 kHz. The actual sample rate is coerced to 3.846 kHz and the one that I programmed is not used. I know that the NI 9237 supports lower sample rates, so why can't I set the NI 9237 to sample below 3.846 kHz? Solution: The NI 9237 supports data rates of 50/n kS/s where n =1, 2, ... 31. However, NI-DAQmx only supports timebase division from 1 to 13 for this module for versions 8.1 through 8.3.1 (versions of NI-DAQmx prior to NI-DAQmx 8.1 do not have support for the NI 9237). Versions 8.5 and later of NI-DAQmx do not have this limitation and allow this module to be sampled at all supported rates (i.e. clock divisors from 1 to 31). If you experience this limitation in versions of NI-DAQmx prior to NI-DAQmx 8.5, you should upgrade to the most recent, compatible NI-DAQmx driver, if possible. You can download the newest version from from the NI-DAQmx homepage. If upgrading the driver is not an option for you, another way to lower the sampling rate involves acquiring large chunks of samples and averaging them to reduce the number of samples effectively acquired. Refer to the figure below and the corresponding attached VI.  Related Links: Product Manuals: NI 9237 Operating Instructions and Specifications (August 2008) Drivers & Updates: NI-DAQmx Attachments:  - block_diagram.JPG
Report Date: 11/28/2006 Last Updated: 06/10/2009 Document ID: 43RF2MQ0 |
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