A first approximation of wind direction can be obtained simply by determining which sensor is returning the greatest absolute value (primary sensor) and its sign, then looking at the sensor arrangement. This divides the compass into 10 regions, each region being 36 degrees wide
| Wind Direction (first approximation) +/- 18 | |
|---|---|
| Primary Sensor | Wind Direction |
| -5 | 108 |
| -4 | 36 |
| -3 | 324 |
| -2 | 244 |
| -1 | 180 |
| +1 | 0 |
| +2 | 72 |
| +3 | 144 |
| +4 | 216 |
| +5 | 288 |
Resolution can be doubled by using the secondary sensor (second greatest absolute value) to split the primary region. Each secondary region is 18 degrees wide.
| Wind Direction (second approximation) +/- 9 | ||
|---|---|---|
| Primary Sensor | Secondary Sensor | Wind Direction |
| -5 | 2 | 99 |
| -5 | 3 | 117 |
| -4 | 1 | 27 |
| -4 | 2 | 45 |
| -3 | 5 | 315 |
| -3 | 1 | 333 |
| -2 | 4 | 235 |
| -2 | 5 | 253 |
| -1 | 3 | 171 |
| -1 | 4 | 189 |
| +1 | -3 | 351 |
| +1 | -4 | 9 |
| +2 | -4 | 63 |
| +2 | -5 | 81 |
| +3 | -5 | 135 |
| +3 | -1 | 153 |
| +4 | -1 | 207 |
| +4 | -2 | 225 |
| +5 | -2 | 279 |
| +5 | -3 | 297 |
Once the secondary region has been determined, further resolution can be obtained by comparing the primary and secondary values. Although the sensor values change in amplitude with changes in wind velocity, the ratio of primary:secondary should be fixed for any given angle.
#define _SECTION_ Bearing #define _PAGE_TITLE_ The Pitot Anemometer #include head.h # include tail.h ------head.h #include "std_dir.h"