what instrument measures the speed of wind

The instrument used to measure the speed of wind is called an anemometer. An anemometer is a device that measures wind speed and direction. It consists of three or four cups, conical or hemispherical in shape, mounted symmetrically about a vertical spindle. The wind blowing into the cups causes the spindle to rotate, and the rate of rotation is proportional to the speed of the wind. Other types of anemometers use turning blades, pressure plates, sound, and tubes to measure wind speed. Wind speed is normally measured in knots, which is the normal unit of wind speed.