How Do Ultrasonic Wind Sensors Work?


Ultrasonic Wind Sensor at Work

Youre standing on the sailboats bow on a windy day, facing the helm and yelling There is a rock ahead. Youre doing this while youre turning forward to look again. What the helmsman hears is There is a…..

Sound waves propagate through the air, and as you turned your mouth (the speaker) away from the direction of the helmsman, the wind blew those sound waves away. Ultrasonic wind sensors can measure this effect.

The distances between the sensors are close enough together that the sound waves arent blown away, and in windless conditions, the speed of sound is consistent and known. Each of the three sensors takes a turn at high frequency yelling while the other two listen.

The time it takes for each listener to hear the yelling is very accurately measured. Apply a lot of calculations, and you can derive both apparent wind direction and speed. As an example, if the wind is from aft of a transceiver, it will push the sound waves a little faster and they arrive earlier. Inversely, if the wind is blowing toward the transceiver, it slows down the sound waves, and it takes them longer to reach the other listeners. The difference in the time it takes to reach each listener is used to triangulate the direction the wind is traveling. This is a very simple explanation of a complex process.

Darrell Nicholson, editor of Practical Sailor, grew up boating on Miami’s Biscayne Bay on everything from prams to Morgan ketches. Two years out of Emory University, after a brief stint as a sportswriter, he set out from Miami aboard a 60-year-old wooden William Atkin ketch named Tosca. For 10 years, he and writer-photographer Theresa Gibbons explored the Caribbean, crossed the Pacific, and cruised Southeast Asia aboard Tosca, working along the way as journalists and documenting their adventures for various travel and sailing publications, including Cruising World, Sail, Sailing, Cruising Helmsman, and Sailing World. Upon his return to land life, Darrell became the associate editor, then senior editor at Cruising World magazine, where he worked for five years. Before taking on the editor’s position at Practical Sailor, Darrell was the editor of Offshore magazine, a boating-lifestyle magazine serving the New England area. Darrell has won multiple awards from Boating Writer’s International, including the Monk Farnham award for editorial excellence. He holds a U.S. Coast Guard 100-ton Master license and has worked as a harbor pilot and skippered a variety of commercial charter boats.


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