An anemometer is a device calibrated to measure the velocity or pressure of fluids (e.g. air). The etymology of the word "anemometer" can be traced back to the Greek word "Anemos" meaning wind. There are two types of anemometers; one which calculates wind speed and the other which shows wind pressure. However, a device geared to measure any one of the wind attributes can show the other measurement as well. Anemometers are used in airplanes, runways, farmhouses and meteorological sites.
Simple Anemometer
Anemometers have been around for a long time. There are many varieties of anemometers from simple designs to the more modern and accurate ultrasonic and pulse laser devices. A very simple anemometer you can make at home consists of a ping pong paddle and a ping pong ball. Tie the ball to the center of the paddle and suspend the ball in air. Since it is very light the string will bend in the direction of the wind. The angle of bend in the string will give you a rough idea about the wind speed.
Vane Anemometer
Vane anemometers have been around for hundreds of years. You can see them even today in rural settings on top of farm houses and churches. These primitive devices do not provide an accurate read of wind velocity but when coupled with the feel and taste of air, you can accurately forecast rain. This is how peasants of the past would the weather. Today, people use vane anemometers as a decorative ornament.
Windmill Anemometer
Another anemometer uses fans to measure wind speed and some can even swivel and therefore can show the wind direction as well. These windmill anemometers are used for rural runways and on farms.
Cup Type Anemometer
An anemometer that gained popularity in the age of hot air ballooning is the cup type anemometer. This anemometer consists of usually four cups arranged all perpendicular to each other and free to rotate under the influence of air. The speed with which the cups spin correspond to the speed of wind.
Pilot Tube Anemometer
Pilot tube anemometers are used on aircraft to measure wind speed. This device determines wind speed by measuring the pressure on a tube within it. This kind of anemometer, however, fails in a stormy weather. Suddenly varying wind speed and direction make an accurate reading difficult.
Thermal Anemometer
Another type of anemometer measures the speed of gas flow in a pipe. These are called thermal anemometers. It consists of two very fine wires. These wires are heated to a certain temperature and then put in the path of liquid or a gas. The gas flowing around the wires will have a cooling effect on them and the temperature drop registered can be calibrated to show wind speeds.
Modern-day Anemometers
Some modern day anemometers are the laser-Doppler anemometer and the ultrasonic anemometer. The laser-Doppler anemometer uses a beam of light and the Doppler effect to measure the speed of air. Ultrasonic anemometers give a burst of ultrasonic waves and by recording the time it takes to travel between two points, determine what the speed and direction of wind is.
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