A wind speed sensor is part of an instrument that is used to measure the velocity of the wind. The scientific name for this instrument is an anemometer, a device that typically includes both a wind direction and a wind speed sensor. The word "anemometer" is from the Greek anemos, for wind. Anemometers are part of the standard equipment in a weather observation station and are used to measure the velocity of the wind at a specific height in the atmosphere. In addition, a wind speed sensor can also be used to measure the speed of airflow in a wind tunnel or for other applications involving the measurement of the velocity of a gas flow.
One of the simplest ways of estimating wind speed is with a wind sock, a fabric tube attached to a flagpole that indicates wind direction and allows for a relative visual estimate of velocity. Another common type of wind speed sensors is the cup anemometer, a rotational sensor with cups that revolve in the wind, driving a generator and producing an electrical output measured by a meter that has been calibrated to wind speed. Friction makes calibrating a cup anemometer difficult and will affect the accuracy of the measurement. Cup anemometers are affordable and are the most commonly used wind speed sensors for a wide variety of applications.
There are more sophisticated types of wind speed sensors that are useful for applications where accurate measurements are required. Thermoelectric wind speed sensors calculate velocity by measuring the rate at which wind cools a heated wire, and they are often used when the average velocities being measured are low. Pressure tubes relate differences in air pressure to wind speed and are used on airplanes and for other applications where the air streams are steady and the average velocities being measured are high. Ultrasonic and laser anemometers use the Doppler effect to estimate wind speed by detecting the phase shift of sound or light reflected from the air molecules.
A mechanical wind speed sensor, such as a cup anemometer, can be affected by weather conditions, including cold temperatures that might lead up to the buildup of ice. Hand-held anemometers are lightweight and portable, but they tend to be less accurate and are mostly used for firefighting or other situations when portability is essential, as well as for educational or recreational purposes. Professional wind speed sensors that have been calibrated can be very expensive and can be delicate. These types of professional precision sensors are essential for highly technical applications, such as estimating energy production when designing wind turbine projects, and for storm forecasting.