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HDAS File Format

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The HDAS (Hardened Data Acquisition System) is a self-contained transducer/recording system developed by Dr. Ray Franco of the Instrumentation Services Division at the US Army Engineer Research and Development Center in Vicksburg, Mississippi.

These files consist of voltage samples followed by a footer describing the test data. The footer structure used in these files is defined below:

typedef struct tagFOOTER {

char    Gain[20];

char    Sensitivity[30];

char    Excitation[20];

char    SamplingPeriod[30];

char    CalResistor[20];

char    YAxisUnits[6];

char    SiteLocation[30];

char    GaugeSerialNumber[40];

char    retriggerLocation[6];

char    FullScaleAD[20];

char    XAxisScaler[20];

char    YAxisScaler[20];

char    YAxisZeroOffset[20];

char    XAxisZeroOffset[10];

char    XAxisUnits[6];

char    CA[20];

char    Rg[20];

char    Reserve[138];


Files produced using this format are always 262,620 bytes in size. Calibration data begins at the start of the file. Calibration data is read from the first and fourth blocks of 1024 2-byte values in the file. Raw data, consisting of voltage measurements, begins at offset 8192 in the file. The time step, in microseconds, is read from the SamplingPeriod member of the footer. Time and engineering unit values for the i'th point are determined by:

Time = (-XAxisZeroOffset+4095+i)*SamplingPeriod;

Y = ( float(RawData & 0x07FF) - YAxisZeroOffset ) *

    (CA/(CalResistor+Rg) / (CalTop-CalBottom)

where SamplingPeriod, XAxisZeroOffset, YAxisZeroOffset, CA, CalResistor, and Rg are the floating point equivalents of the corresponding character strings in the footer, and CalTop and CalBottom are the average calibration values read from the 1st and 4th blocks of 1024 calibration values, respectively.



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