Because of this asymmetrical force, torque is generated on the anemometer's axis, causing it to spin. 38 on the spherical side and 1.42 on the hollow side, more force is generated on the cup that presenting its hollow side to the wind. Since a hollow hemisphere has a drag coefficient of. With a four-cup anemometer, the wind always has the hollow of one cup presented to it, and is blowing on the back of the opposing cup. This type of instrument is also called a rotational anemometer. Therefore, counting the shaft's revolutions over a set time interval produced a value proportional to the average wind speed for a wide range of speeds.
The air flow past the cups in any horizontal direction turned the shaft at a rate roughly proportional to the wind's speed. It consisted of four hemispherical cups on horizontal arms mounted on a vertical shaft. Velocity anemometers Cup anemometersĪ simple type of anemometer was invented in 1845 by Rev Dr John Thomas Romney Robinson of Armagh Observatory. In 1994, Andreas Pflitsch developed the sonic anemometer. In 1991, Derek Weston added the ability to measure wind direction. In 1926, Canadian meteorologist John Patterson (1872–1956) developed a three-cup anemometer, which was improved by Brevoort and Joiner in 1935. In 1846, John Thomas Romney Robinson (1792–1882) improved the design by using four hemispherical cups and mechanical wheels. (1635–1703), developed their own versions, with some mistakenly credited as its inventor. In the ensuing centuries numerous others, including Robert Hooke Alberti is said to have invented it around 1450. The anemometer has changed little since its development in the 15th century.
The earliest known description of an anemometer was by Italian architect and author Leon Battista Alberti (1404–1472) in 1450. It is a common instrument used in weather stations. In meteorology, an anemometer (from Greek άνεμος (anemos) 'wind', and μέτρον (metron) 'measure') is a device that measures wind speed and direction. A hemispherical-cup anemometer of the type invented in 1846 by John Thomas Romney Robinson.
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