Anemometer - Measurement of Wind Speed

Anemometer

What Is Anemometer?

An anemometer is an instrument used to measure the speed of the wind, which is a common weather station instrument or to calculate any form of current gas. The term is derived from the Greek word anemos meaning wind which was first explained by Leon Battista Alberti who was an Italian artist and an architect in the year 1450. He used a mechanical anemometer which was placed perpendicular to the wind direction such that the wind velocity as indicated by the angle of inclination of the disc.

How To Make An Anemometer?

Anemometer can be easily made by assembling a few basic materials. There are various types of anemometer depending on different situations, measurements, and ecosystems. An anemometer also uses Ultrasonic and Laser techniques to get accurate measurements of the wind.

For the science experiment of 5th grade, the anemometer is prepared with disposable cups. It is commonly called as Robinson Anemometer. It uses disposable cups to catch the wind that induces to spin. To calculate the wind speed, one has to measure the number of spins in a given time interval. This will show how fast the wind is moving.

  • Materials Required
    • 5 small paper cups
    • Empty plastic bottle
    • 3 thin wooden dowels
    • Scissors
    • Hole punch
    • Duct tape
    • Stopwatch
  • Procedure
    • Make a hole on the side of four paper cups using the hole punch.
    • The last cup will be the center of an anemometer, make 4 holes evenly spaced around the rim of the last cup.
    • Slide 2 wooden dowels through the holes in the center cup.
    • Now insert the other end of the wooden dowels into the other cups holes and tape them. Make sure that all cups are facing the same direction.
    • Use the last wooden dowel and attach it to the bottom of the center cup.
    • Put the center wooden dowel into an empty plastic bottle.
  • Observation

The cup anemometer expressed in this experiment is not capable of displaying the wind speed, but it can give an idea of how fast the wind is blowing. However, you can record the speed of wind using this anemometer only by the measuring revolutions per minute. Meanwhile, the higher capacity anemometer that is used in weather forecasting measure the wind speed by kilometer per hour or miles per hour.

You can keep a record of the wind by revolution per minute for a few days and calculate the average wind speed in a week. You can also check the wind speed at different times of the day. Verifying the speed in the morning, afternoon, evening and at night.

Types Of Anemometers

The basic classification of anemometers depends on the measurement of the velocity of wind and measurement of pressure of the wind. The 5 major types of anemometer are:

  • Cup anemometer: This consists of four hemispherical cups that are mounted on one end of the horizontal arms at equal angles on a vertical shaft. The positioning of the cups is such that the air passes through them in the horizontal direction making the cups rotate such that it is proportional to the speed of the wind. By calculating the turns of the cups over a period of time, the average speed of the wind is found. These are used by researchers, meteorologists, and educational institutions for research and commercial activities.
  • Hotwire anemometer: This consists of thin wire which is heated up to a certain temperature slightly more than atmospheric temperature. The wire cools as the air flows past the wire. To calculate the velocity, the relation between the resistance of the wire and the velocity of the wind must be obtained as most metal’s resistance depends on the temperature of the metal. These find applications in HVAC (heating, ventilating and air conditioning) businesses measuring the airflow through the building ducts.
  • Windmill anemometer: This is a mechanical device similar to the regular windmill used to calculate the velocity of the wind. It consists of the axis of rotation running parallel to the direction of the wind. It also has an aerovane as the direction of the wind is not constant helping the axis change the direction. The aerovane consists of a propeller and a tail to obtain precise wind speed and direction measurements.
  • Laser Doppler anemometer: A beam of light is used which is further split into two beams. The velocity is determined by calculating the amount of light that has been reflected off by the moving air particles when one of the two beams is made to enter the anemometer. These find applications in high-tech jet engines and also in river hydrology.
  • Sonic anemometer: Sound waves are used to obtain the speed of the wind. These waves are made to pass through the transducer. These find applications in aircraft and scientific wind turbines.

Uses Of Anemometer

Other than measuring the speed of the wind, the anemometer is used for the following purposes:

  • To measure the wind pressure
  • To measure the flow of the wind
  • To measure the direction of the wind
  • It is used by the drone users or RC plane users to check the weather conditions before testing their devices
  • Also used by long range shooters and pilots
  • Used by skydivers to evaluate wind velocity before they leap into the abyss
  • Used in aerodynamics to measure the airspeed

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Practise This Question

Which type of spherical mirror does the inner surface and the outer surface of a spoon act as?