Rockwell Automation 1440-VSE02-01RA XM-122 gSE Vibration Module - Manual (Page 178)

Publication GMSI10-UM013D-EN-P - May 2010
168 DeviceNet Objects
normalized spectrum data into real and imaginary values, use the following
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.
The Real Data and Imaginary Data values are converted into magnitude and
phase values with the following equations:
The Waveform Data structure contains an array of values that, taken together,
are the output of the sampling performed by the Spectrum/Waveform
Measurement Object on the input signal. The Waveform Data array values are
normalized and must be converted to floating point to obtain the true values.
Real Data
n
Amplitude Reference
Normalized Data
2n
32768
-------------------------------------------------- =
Imaginary Data
n
Amplitude Reference
Normalized Data
2n 1 +
( )
32768
------------------------------------------------------------------ =
Magnitude Data
n
Real Data
n
2
Imaginary Data
n
2
+ =
Phase Data
n
arctan
Imaginary Data
n
Real Data
n
-------------------------------------------
⎝ ⎠
⎜ ⎟
⎛ ⎞
=
Table C.55 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 should be
equal to the Number of Waveform Points attribute
setting. It is provided within this structure to assist in
determining the size of the structure.
4 (1) Period REAL The period of the waveform.
This is the actual period of the waveform and may vary
from 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 must be converted to floating point values using
the Amplitude Reference value.