An anemometer measures the pressure and force of the wind. There are several different types of anemometers: cup or propeller anemometers electronically measure the wind by counting the revolutions per minute; ultrasonic or laser anemometers detect light that is reflected from lasers off air molecules; hot wire anemometers detect wind speed through temperature differences between wires placed in the wind and away from the wind. The most common is the cup anemometer.
The anemometer measures in feet per minute, or FPM. The rotation is sensed by a magnetic or optical sensor that converts the signal to FPM measurement.
An arrow on the vane head identifies the direction the airflow must travel through the vane to obtain proper measurements. An average measurement range for anemometers is 50 feet to 6,000 feet per minute. One thousand feet per minute is equal to about 11 miles per hour.
Uses of Anemometers
Anemometers can be used in weather stations, airports, on ships, oil rigs or for personal use. Most anemometers are attached to wind vanes to detect wind direction.
Readings of airflow measurement are in actual feet of air, meaning the measurement is taken at the height where the anemometer is located. This measurement results in actual feet per minute. Anemometers are placed on the roofs of houses or on top of towers that can be 20 to 50 feet tall. High elevations may give higher wind-speed readings.
Accuracy of the readings can be affected by the angle of the vane and minimum air velocity needed to rotate the vane. Factors that can affect wind source are elevation, nearby landforms such as valleys or mountains, and trees or buildings that may block wind. Anemometers near mountains, valleys or canyons may have increased wind flow.