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X Series SMIO On Demand Sampling Returns Stale Data

Hardware: Multifunction DAQ (MIO)>>X Series>>NI PXIe-6368, Multifunction DAQ (MIO)>>X Series>>NI PXIe-6358, Multifunction DAQ (MIO)>>X Series>>NI PXIe-6356, Multifunction DAQ (MIO)>>X Series>>NI PXIe-6366

Problem:
I'm performing On Demand Sampling with my X Series SMIO board and it appears to be returning stale/old data. How can I resolve this issue?

Solution:
National Instruments recently discovered issue with DAQmx 9.0 that causes erroneous samples to be inserted into the FIFO approximately every 43 seconds. This issue affects X Series SMIO boards that are using On Demand Sampling.

 

This issue results in three different user related symptoms.

1. Stale Data - Regardless of the user defined sample rate, once the DAQmx task has started, every 43 seconds data will be incorrectly pushed into the FIFO. This data is added to the FIFO in addition to user requested samples. Refer to the illustration below.
   
2. ADC Overrun Error - If the user tries to read data just before or just after (i.e. sample at 43.1 seconds) the sample clock pushes data into the FIFO, the ADC will error out and the user will be notified.
3. Since data is being added to the FIFO faster than it is being removed, the FIFO will overflow in approximately 3 days.

To resolve the issue, upgrade no NI-DAQmx 9.0.2 on your host computer.

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Report Date: 09/23/2009
Last Updated: 10/06/2009
Document ID: 51M9BDSK

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