About Anemometers

History

• Before devices that measure wind speed were developed, scales such as the popular Beaufort scale were used for estimations. These take advantage of the effects of wind that can be seen, such as blowing trees and smoke as well as ocean wave height. While there is debate about who invented the first anemometer, the Italian Renaissance figure Leon Battista Alberti is most often cited as inventing a swinging plate device around 1450, which is thought to be the first mechanical anemometer. Many new and different versions have since been developed.
  
  

Function

• Predicting and recording wind at different levels of the atmosphere for meteorological purposes is only one use of the anemometer. Scientists also use them to measure properties of flows of different gasses. Increasingly, hand-held units are used in energy audits to determine leaks near windows, doors and other potential energy loss areas in buildings. Heating, ventilation and air conditioning (HVAC) units are often tested and analyzed using anemometers.
  
  

Types

• There are various types of anemometers, include mechanical varieties, of which the cup type is the most common, and non-mechanical, such as ultrasonic types. The cup variety usually has three or four cups that rotate around a vertical axis. Rotation is correlated to wind speed. The ultrasonic variety has two rods, one of which shoots a sound wave toward the other. The time it takes to close the gap is electronically measured and translated to air velocity. There are also laser anemometers, which are extremely accurate and used for measuring gas flow speed as well as air velocity.
  
  

Considerations

• Wind vanes measure direction and not speed. However, directional instruments are sometimes combined with those that record velocity and are called anemometers.
  
  

Expert Insight

• Some weather stations record evaporation rates through the use of evaporation pans. Measuring wind speed over these pans allows for accounting of air flow affect on evaporation. This requires proper citing of the anemometer, which involves mounting a three-cup device on a stand about half a foot above the top of the evaporation pan. In comparison, anemometers typically used for regular velocity measurements are placed at a height of 23 to 30 feet above the surface.