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Incorrect Binary Data with a NI 4472 using AI Read VI

Primary Software: LabVIEW Development Systems>>Full Development System
Primary Software Version: 7.1
Primary Software Fixed Version: N/A
Secondary Software: LabVIEW Development Systems
Hardware: Modular Instruments>>Dynamic Signal Acquisition and Analysis (DSA)>>NI 4472 for IEEE 1394, Modular Instruments>>Dynamic Signal Acquisition and Analysis (DSA)>>PXI-4472

Problem:
The binary datatype out of the Traditional NI-DAQ (Legacy) AI Read.vi is 16 bits. The bit resolution of the NI 4472 board is 24-bits, therefore a sample is 24 bits wide. When choosing a datatype such as binary, each sample in memory can only be 16 bits wide. If you try to store 24 bits of information (4472) in a 16-bit element, information is lost. The eight least significant bits of the number will be lost in this case.

Solution:
An alternative solution is to use a 32-bit size datatype (scaled data for the AI Read VI) to store the data from the NI 4472 and convert it to a 32-bit binary number after the acquisition. Also, if you use the NI DAQmx driver with DAQmx Read and select the Raw 1D I32 instance, you can read in the 32-bit binary data. Both options will preserve the least significant bits.

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Report Date: 08/22/2002
Last Updated: 04/19/2007
Document ID: 2OLB4EJT

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