The anemometer and wind vane are each attached to a horizontal supporting arm at the top of a 10 m mast. Where wind measurements are made in extreme weather conditions, such as on the top of mountains, a heated sonic anemometer is used having no moving parts.
The instrument measures the speed of acoustic signals transmitted between two transducers located at the end of thin arms. Measurements from two pairs of transducers can be combined to yield an estimate of wind speed and direction. The distortion of the air flow by the structure supporting the transducers is a problem which can be minimized by applying corrections based on calibrations in a wind tunnel.
Because wind is an element that varies rapidly over very short periods of time it is sampled at high frequency e v e r y 0. The gust speed and direction are defined by the maximum three second average wind speed occurring in any period. A better measure of the overall wind intensity is defined by the average speed and direction over the ten minute period leading up to the reporting time.
Mean wind over other averaging periods may also be calculated. A gale is defined as a surface wind of mean speed of knots, averaged over a period of ten minutes. Terms such as 'severe gale', 'storm', etc are also used to describe winds of 41 knots or greater. Another one of the types of anemometer are vane anemometers. They are not mounted vertically like the cup anemometers and instead the blades are horizontally mounted and face into the wind.
Vane anemometers must rotate to face in whatever direction the wind is blowing so they often use a wind vane opposite the propeller to shift in the direction of the wind. Like cup anemometers, vane anemometers or propeller anemometers automatically count the number of revolutions per second to calculate wind speed and display that digitally for you.
Some vane anemometers are meant to be mounted on buildings but handheld vane anemometers are also quite common. Hot-wire anemometers or constant current anemometers work by heating a thin wire to a specific temperature and then measuring how much the wire is cooled by the air flow. The hot wire anemometer is able to calculate how fast the wind is blowing by measuring how quickly the wire cools down and how cool it gets.
Each type of wind speed monitor works slightly differently and may be better for some uses than others. Anemometers come with different uses in mind but most handheld wind speed monitors are fairly rugged and most mountable anemometers tend to be weatherproof.
Some anemometers are easy to take with you wherever you go, and others come as part of wireless weather stations that you can place in your backyard and read off an indoor monitor. Additionally some handheld anemometers are compact for portable use and others have long cables for mounting purposes. Still others are designed to be mounted on boats. Some anemometers are better for HVAC installation or repair uses and others still like hot wire air velocity meters are great for measuring the air flow that may be coming in from a drafty door or window.
The propeller blades rotate at a rate proportional to the wind speed. A windsock often is used at airports. A windsock is a cone-shaped bag with an opening at both ends. When it is limp, winds are light; when it is stretched out, winds are strong. Pilots can quickly determine the wind direction and speed along a runway just by observing the shape and direction of a windsock.
Sonic anemometers use sound waves humans cannot hear to measure wind speed and direction. The instrument determines the wind velocity by measuring the time between when the instrument sends a sonic pulse and when it is received. The Weather Guys. Skip to content.
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