| Near-surface atmospheric wind speed and direction are measured by RM Young Wind Monitors mounted atop mass attached to each bridge wing. Having two sensors provide redundancy in case of instrument failure. In addtion, during most periods when both wind sensors are operational, the measurment from the upwind sensor is the one that is reported and used in subsequent analysis since it is the one least influenced by the vessel. The wind speed sensor is a four blade helicoid propeller that turns a multi-pole magnet. Propeller rotation induces a variable frequency signal in a stationary coil, which is measured and converted to wind speed. The wind direction sensor is based on the unit's molded weather vane. The vane angle is detected by an optical encoder. The range of the wind speed sensor is 0-60 m/s (134 mph), with gust survival rated to 100 rn/s (220 mph). The wind speed sensor has a resolution of 0.1 m/s and an accuracy of ±0.3 m/s (0.6 mph). The range of the wind direction sensor is 0-360 degrees, and it has a resolution of 1 degree and an accuracy of ±2 degrees. |
