What does an anemometer measure?

An anemometer can measure the total velocity magnitude, the velocity magnitude on a horizontal plane, or the velocity component in a particular direction.

Types of anemometers

There is a wide range of anemometers models for directly measuring wind and air velocity. The four most popular anemometer models are: Vane Anemometers, Thermal Anemometers, Thermal Anemometers with Velocity / Temperature Profiling and Cup Anemometers. Anemometers are usually classified as constant-temperature, or constant-power anemometers.

Constant-temperature anemometers are popular because of their high-frequency response, low electronic noise level, immunity from sensor burnout when airflow suddenly drops, compatibility with hotfilm sensors, and their applicability to liquid or gas flows.

Constant-power anemometers do not have a feedback system. Temperature is simply proportional to flow rate. They are less popular because their zero-flow reading is not stable, temperature and velocity response is slow, and temperature compensation is limited.

Most common anemometer applications

An anemometer usually measures gas flows that are in turbulent flow conditions. The vane anemometer, thermal anemometer and cup anemometer (typically used in weather stations) are mostly used to measure the mean velocity, while the hot wire anemometers are usually used when turbulence characteristics are being measured, such as transverse measurements in a cross-section. The term "thermal anemometer" is often used to mean any anemometer that uses a relationship between heat transfer and velocity to determine velocity.

Anemometers for weather stations

The cup anemometer (used in weather stations) measures the air velocity in a plane perpendicular to the axis of its rotation cups. If the cup anemometer is mounted with the shaft perpendicular to the horizontal, it will measure only the component of the wind that is parallel to the ground. Other wind speed meter, such as vane anemometers, are used with the tip aligned with the total velocity vector. Before using an anemometer, it is important to determine how it should be positioned and what component of the total velocity its measurement represents.