An anemometer is the instrument used to measure wind speed. The most recognisable type is the cup anemometer, invented by John Thomas Romney Robinson in 1846: three or four hemispherical cups mounted on horizontal arms spin around a vertical axis, and the rotation speed is proportional to wind speed. Modern cup anemometers use optical or magnetic rotation sensors for precision.
Other types include the vane anemometer (a small propeller aligned with the wind, used in handheld devices), the hot-wire anemometer (an electrically heated wire cooled by the wind — extremely sensitive for laboratory and turbulence research), the sonic anemometer (measuring the speed of ultrasonic pulses between transducers — capable of 3D wind measurement at 20+ Hz, essential for turbulence and flux studies), and Pitot tubes (used in aviation to measure airspeed).
Official weather stations mount their anemometers at a standard height of 10 metres above open terrain, away from buildings and trees, to ensure comparable readings. Wind speeds measured at other heights are corrected to the 10 m standard using logarithmic wind profile equations. Anemometers are typically paired with wind vanes that indicate direction. Modern automated weather stations sample wind every second and report 2-minute mean speeds and instantaneous gusts. The Beaufort scale was the standard before instruments, and remains useful for estimating wind speed from visual clues.