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Rockwell Automation Publication 1440-UM001D-EN-P - September 2016 151
CIP Objects Appendix B
The Real Data and Imaginary Data values are converted into magnitude and
phase values with these equations:
The Waveform Data structure contains an array of values that, taken together,
are the output of the sampling that the Spectrum/Waveform Measurement
Object performs on the input signal. The Waveform Data array values are
normalized and must be converted to floating point to obtain the true values.
The total size of the Waveform Data structure in DWORDs is 3 + (Number of
Waveform Points / 2).
The Waveform Data is an array of INT (16-bit signed integers ranging from -
32768…32767). The number of INTs in the Waveform Data array is equal to
the Number of Waveform Points. To convert the normalized Waveform Data
into floating point values, use these equations:
Imaginary Datan Amplitude Reference
Normalized Data 2n 1
+
 
32768
-------------------------------------------------------------------- =
Magnitude Datan Real Datan
2
Imaginary Datan
2
+ =
n
Imaginary Datan
Real Datan
--------------------------------------------
 
 
 
Table 79 - Waveform Data Structure
Byte (DWORD) Offset
Within Structure Structure Member Data Type Description
0 (0) Number of Waveform Points UDINT Number of points in the waveform data. This value must be equal to the Number
of Waveform Points attribute setting. It is provided within this structure to help
determine the size of the structure.
4 (1) Period REAL The period of the waveform.
This value is the actual period of the waveform and does not always match the
Period 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 The normalized waveform data points
These values must be converted to floating point values using the Amplitude
Reference value.
Float Datan Amplitude Reference
Normalized Datan
32768
------------------------------------------------- =