anemometer

An anemometer is a device for measuring wind speed, commonly used in meteorology, climatology, aviation, and wind energy assessment. The name derives from the Greek words anemos (wind) and metron (measure). Instruments may be mechanical or electronic, and some also determine wind direction when paired with a wind vane.

The most familiar form is the mechanical cup anemometer, typically with three or four cups mounted on a horizontal axis. Wind creates drag on the cups, causing rotation; the rotor speed is converted to wind speed through calibration. A vane anemometer uses a propeller or fan-like element with a tail to align with the wind and measures speed via rotational rate, often on the same axis as a separate wind vane.

Electronic and non-mechanical variants include hot-wire (or hot-film) anemometers, where a heated filament loses heat to moving air and the cooling rate provides velocity; these are common in research and fluid dynamics studies for high-frequency measurements. Ultrasonic anemometers determine wind velocity by measuring travel time or phase shifts of sound pulses between transducers; they have no moving parts and can measure multi-axis wind components with rapid response.

Other specialized methods, such as laser Doppler anemometry or particle image velocimetry, are primarily used in laboratory research to study flow fields rather than routine weather monitoring.

Applications encompass weather stations, airports, ships, and wind farms, as well as atmospheric research and environmental monitoring. Readouts are typically expressed in meters per second (m/s), with conversions to kilometers per hour, knots, or miles per hour. Calibration relates sensor output to wind speed under standard conditions. History notes that the cup design was developed in the 19th century by John Thomas Romney Robinson, with ongoing improvements in modern instruments.