A vane anemometer is a type of instrument, commonly used in meteorology, that combines two instruments, a wind vane and an anemometer, into one unit. An anemometer is an instrument that measures wind speed. A wind vane determines the direction of airflow. By combining the two instruments into one unit, it is possible to measure both speed and the directional component of wind along with any changes in either component as they occur.
Many types of anemometers are capable of measuring wind speed. A vane anemometer is only one type of instrument used for this purpose. A typical vane anemometer has a distinct design, however, that sets it apart from other types of anemometer. It consists of two elements: the anemometer itself and a wind vane.
The anemometer portion of a vane anemometer is usually of the propeller type. A propeller anemometer is calibrated in such a way as to measure wind speed by the speed at which the wind causes the propeller to spin. This type of anemometer may use mechanical or electronic means to record and calculate this data. The wind vane portion may use mechanical or electronic means to transmit data on wind direction as well.
The wind vane element of a vane anemometer is used to determine wind direction. It is simply a device that always faces into any wind. Aerodynamic principles and the design of the vane dictate that it will always turn to face any wind, regardless of wind strength or direction. Many old fashioned windmills operated on this principle as well. Incorporating a vane and mounting the assembly on a swivel capable of turning in any direction, ensures that the windmill is always facing the wind and operating at maximum efficiency.
Visually, vane anemometers tend to resemble airplanes with no wings, mounted on swivel bases that allow them to freely spin in any direction. They are often mounted some distance above ground, such as on a rooftop or instrument tower, and are common sights at weather observation stations, airports, or ships. Hand held anemometers are often called vane anemometers, but this can be misleading, as many are not capable of measuring wind direction. They are sometimes called vanes because they use a propeller anemometer, which is the most common type of anemometer in a vane anemometer. True hand held vane anemometers are capable of rotating to face the wind.
Meteorologists often use instruments of this type to gather data about local weather conditions. They can use the data for a number of purposes, including weather forecasting, research on weather patterns, or climatology. Airports use data from vane anemometers to help manage airplane departures and landings, as wind speed and direction can strongly influence how these operations are carried out. In addition, ships of all sizes often use data from vane anemometers to help manage navigation, particularly when under sail.