What does an anemometer measure in?

Question:

A brief history of the anemometer

Anemometers are a frequently used tool of meteorologists and amateur weather observers alike; they are instruments used to determine wind speed. Since it is a fairly simple instrument the concept and the design of the anemometer has hardly changed since its invention which occurred around the mid 1400's. This early anemometer, discovered by an Italian architect, Leon Battista Alberti consisted of a flat disk that when placed perpendicular to the wind would rotate and the resulting angle of the disk would correspond to the wind velocity. It wasn't until 1846 that John Thomas Romney Robinson improved on this design by using instead of a disk, four rotating cups. The cups rotated around a fixed pole at a rate that was determined by the wind speed. This type of anemometer is still widely used today. Since then a variety of different anemometers have been developed ranging from weathervane type models to instruments that utilize hot wires or lasers.

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