Wind power professionals, meteorologists, physicists, farmers and even NASA scientists use anemometers to measure wind speed and direction. Anemometers come in many different forms, from simple to high-tech, with varying uses and degrees of accuracy.
Anemometers that use cups or propellers are the most prevalent but least high-tech. Cup anemometers have three or four cups mounted on arms that can spin a vertical rod. Other types use propellers instead of cups. Wind will catch the cups or propellers and rotate them -- the rotations will be counted and wind speed calculated. These anemometers generally only measure wind speed.
Ultrasound, or sonic, anemometers use sound waves to measure the velocity and direction of wind. They employ sound transmitters that send information to receivers, usually within a few inches of each other. Wind blowing between the two affects the sound, speeding it up or slowing it down. The changes are measured to calculate wind speed and trajectory. These anemometers are extremely accurate and dependable.
Because many scientific disciplines and industries depend on wind, there are many other types of anemometers that measure wind. Air pressure measured by a tube anemometer can be used to calculate wind data. Laser anemometers use Doppler wave frequency information to determine wind speed and direction. Hot-wire anemometers measure how much wind cools heated wires.