An anemometer is a device for measuring the force or speed of the wind. This instrument has been around since at least 1450. Many different types of anemometers are on the market, each with unique characteristics. Some of the devices measure more than just wind speed. Some people for fun build their own anometers -- that's something you might want to try as well.
The cup or rotational anemometer is one of the oldest types of anemometers. The cups are placed onto a vertical axis, and when the wind presses against them, this causes the cups to rotate around. The faster the cups rotate, the faster the wind speed. Cup anemometers usually have digital readouts. Researchers, educational institutions and meteorologists worldwide use this type of anemometer for research and commercial activities.
Hot wire or thermal flow anemometers measure both the wind speed and pressure. The device is a long rod and at the tip is a hot wire or hot bead. The anemometer is placed into a location and as wind moves over the hot wire, the wire is cooled. A direct relationship exists between the rate at which the wind is flowing and how cool the wire becomes. You can find this type of anemometer in the heating, ventilating and air-conditioning businesses -- it measures the airflow through building ducts.
The windmill anemometer measures both wind speed and direction. The anemometer has a propeller located at the front of the device and a large tail section. As the wind blows, it presses against the propeller, making it spin. The rotational speed of the propeller indicates how fast the wind is moving at any time.
A pressure tube anemometer is called a wind sock. These devices are found around airports. Material is made into a tube shape and is connected to wires. As the wind blows, it catches the larger end of the tube. This anemometer provides wind direction because the larger end of the sock will move into the wind. The faster the wind blows, the higher the tube raises off the ground. Pressure tubes do not provide readouts but are relative measurements of wind speed.
Ultrasonic anemometers send sonic pulses across a path to a sensor on the opposite side. As the wind moves more quickly, the pulses are disrupted. A measurement of this disruption provides accurate wind data. An ultrasonic anemometer has no moving parts and can detect even small changes in the wind. The device typically has four sensors arranged in a square pattern. Some units come with built-in heaters.
Laser Doppler anemometers utilize the Doppler effect to determine the flow of air. Commonly used for high-tech applications such as in jet engines, the laser Doppler can measure even the slightest changes in airflow. This type of anemometer is also used in river hydrology.