Anemometer Lind was not the first it was the most practical and best known anemometer of this type. If the wind blows into the mouth of a tube it causes an increase of pressure on one side of the manometer. The wind over the open end of a vertical tube causes little change in pressure on the other side of the manometer. The resulting elevation difference in the two legs of the U tube is an indication of the wind speed. However, an accurate measurement requires that the wind speed be directly into the open end of the tube; small departures
Anemometer cups and arms, and may have a value between two and a little over three. Every previous experiment involving an anemometer had to be repeated after the error was discovered. The three-cup anemometer developed by the Canadian John Patterson in 1926 and subsequent cup improvements by Brevoort & Joiner of the United States in 1935 led to a cupwheel design with a nearly linear response and had an error of less than 3% up to . Patterson found that each cup produced maximum torque when it was at 45° to the wind flow. The three-cup anemometer also had a more