Allen-Bradley 1440-SDM02-01RA, Руководство пользователя, Страница: 152 / 168

150 Rockwell Automation Publication 1440-UM001D-EN-P - September 2016
Appendix B CIP Objects
attribute. In all cases, the spectrum data array values are normalized and must
be converted to floating point to obtain the true values.
The total size of the Spectrum Data structure in DWORD is:
• For Magnitude Data Format: 3 + (Number of Spectrum Lines / 2)
• For Complex Data Format: 3 + (Number of Spectrum Lines)
If the data format is Magnitude Data then the Normalized Value Array is an
array of UINT (16-bit unsigned integers ranging from 0…65535). The number
of UINTs in the spectrum data array is equal to the Number of Spectrum
Lines. To convert the normalized spectrum data into floating point values, use
this equation:
Where Float Data
n
is the value for the nth spectrum bin, and 0 £ n £ Number
of Spectrum Line.
The Float Data value represents an amplitude value if Data Format is real data.
The Float Data represents a power value if Data Format is power data.
If the data format is Complex Data, then the Normalized Value Array is an
array of INT (16-bit signed integers ranging from -32,768…32,767). There are
two INTs (real and imaginary values) in the array for each spectrum bin (the
array size is twice the Number of Spectrum Lines). To convert the normalized
spectrum data into real and imaginary values, use these equations:
Where Real Data
n
and Imaginary Data
n
are the real and imaginary values for
the nth spectrum bin, and 0 £ n £ Number of Spectrum Line.
Table 78 - Spectrum Data Structure
Byte (DWORD) Offset
Within Structure Structure Member Data Type Description
0 (0) Number of Spectrum Lines UDINT Number of lines or bins in the spectrum data. This number must be equal to the
Number of Spectrum Lines attribute setting. It is provided within this structure to
help determine the size of the structure.
4 (1) FMAX REAL The maximum frequency or order of the spectrum data.
This value is the actual FMAX of the spectrum data and does not always match the
FMAX attribute setting.
8 (2) Amplitude Reference REAL Normalization factor
This factor is used to convert the normalized array data into floating point values.
12 (3) Normalized Value Array Array of INT or UINT The normalized spectrum data points
These data points must be converted to floating point values using the Amplitude
Reference value. The Data Format attribute determines whether the values are INT
or UINT and exactly what conversion must be applied.
Float Datan Amplitude Reference
Normalized Datan
65536
------------------------------------------------- =
Real Datan Amplitude Reference
Normalized Data2n
32768
---------------------------------------------------- =