Operating Deflection Shapes: Extracting ODS from Cross Channel Phase Data
QUESTION
How do I obtain an operating deflection shape from cross channel phase data?
ANSWER
You can enter the raw data points into a spreadsheet program such as Microsoft® Excel, perform a few calculations, then plot the results as an operating shape chart. This procedure is described below.
Setup
This example uses 12 roving readings away from the reference point.
|
Measurement |
Reference |
Roving |
Phase |
|
1 |
0.1148 |
0.2183 |
40 |
|
2 |
0.1149 |
0.1891 |
135 |
|
3 |
0.1151 |
0.1787 |
330 |
|
4 |
0.1147 |
0.2378 |
180 |
|
5 |
0.1152 |
0.2177 |
220 |
|
6 |
0.1151 |
0.2989 |
315 |
|
7 |
0.1147 |
0.2288 |
1 |
|
8 |
0.1156 |
0.1278 |
125 |
|
9 |
0.1152 |
0.1676 |
215 |
|
10 |
0.1149 |
0.1377 |
230 |
|
11 |
0.1145 |
0.1879 |
140 |
|
12 |
0.1145 |
0.2481 |
215 |
- Take the raw data across a machine member.
- Normalize the data by taking the ratio of the Roving/Reference data and multiplying the resulting number by the average Reference value.
- Pick the point of highest amplitude (#6).
- Re-reference all phase angles to this point (315 degrees).
- Take the normalized amplitudes and multiply them by the Cosine of the re-referenced phase angle.
- Plot the results.
The resulting plot then shows the shape, with the peak deflection being at the point with highest amplitude.
FAQ ID: 18012 Last Reviewed: 3 October 2006