cupanemometer

A cup anemometer is a device used to measure wind speed. It typically features three or four cups mounted on horizontal arms that are attached to a vertical rotor. When wind blows, the cups catch the air and create torque that causes the rotor to spin. The rotation rate is related to wind speed through calibration that accounts for cup size, number of cups, and air density.

In practice, a cup anemometer is often coupled with a wind vane to provide both speed and direction. Modern units commonly use a magnetic or optical sensor to count rotations, producing electrical pulses that are logged by a weather station or data logger. The output is then converted to wind speed using a device-specific constant or calibration curve. The simple, robust design makes cup anemometers widely used in meteorological stations, aviation meteorology, ships, and field research, where low power consumption and mechanical reliability are advantageous.

Limitations and considerations include sensitivity to wind direction (yaw error) if the device is not properly aligned, effects of turbulence and gusts on readings, and potential drift from wear or icing in cold conditions. Cup anemometers require periodic calibration and maintenance to ensure accuracy, and their linear response can vary with cup size and mounting geometry.

History and development: the concept dates from the 19th century, and the basic three- or four-cup design has remained largely mechanical. Modern variants integrate electronic sensing and data logging, improving ease of use and long-term data quality while preserving the fundamental principle of using cups to translate wind pressure into a measurable rotational speed.