Hand-held cup anemometer used in the past for terrain measurement of wind speed based on rotation frequency.
The cup anemometer uses the angular rotation speed of a rotor consisting of cups arranged symmetrically around a usually vertical axis of rotation to measure wind speed. The first cup anemometer dates from 1837 by W. Whewell and was substantially improved by the Irish natural scientist J. T. R. Robinson in 1846. The basis of the bowl anemometer system is a rotor consisting of three or four cups, which are placed with their sides convex with respect to the direction of rotation on equally long arms at identical angular distances. In the 4-dish variant the rotor is known as a Robinson cross, but today the 3-dish variant is the predominant one, which is more convenient according to current knowledge. Due to their hemispherical or conical shape, the bowls impose approximately four times more resistance to the flowing medium with their hollow side than with their convex side, which causes the apparatus to rotate. The entire rotor body must be housed in good quality bearings to allow easy rotation with a low sensitivity threshold.

A bowl anemometer measures the component of wind speed perpendicular to the axis of rotation of the rotor. This is oriented vertically as standard and the instrument is therefore used to measure the horizontal component of the wind speed. To measure the wind direction, it is usually accompanied by a wind direction finder. Together with ultrasonic anemometers, this is the most widely used type of anemometer.

Source: Česká meteorologická společnost [online]: Elektronický meteorologický slovník (eMS) [cit 21.12.2023]. Dostupné z: http://slovnik.cmes.cz