The cup anemometer (used in weather stations) measures the velocity in a plane perpendicular to the axis of its rotation cups. The term anemometer was derived from the Greek words anemos, “wind,” and metron, “measure.” Mechanical anemometers were first developed back in the 15th century to measure wind speed. The term "thermal anemometer" is often used to mean any anemometer that uses a relationship between heat transfer and velocity to determine velocity. ![]() 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. They are less popular because their zero-flow reading is not stable, temperature and velocity response is slow, and temperature compensation is limited.Īn anemometer usually measures gas flows that are in turbulent flow conditions. Temperature is simply proportional to flowrate. Anemometers are usually classified as constant-temperature, or constant-power anemometers.Ĭonstant-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.Ĭonstant-power anemometers do not have a feedback system. The four most popular anemometer models are: Vane Anemometers, Thermal Anemometers, Thermal Anemometers with Velocity / Temperature Profiling and Cup Anemometers. There is a wide range of anemometers models for directly measuring wind and air velocity. While hot wire anemometers are best suited for clean gases at low velocities, venturi meters can also be considered for some liquid (including slurry) flow applications.Īn anemometer can measure the total velocity magnitude, the velocity magnitude on a horizontal plane, or the velocity component in a particular direction. ![]() It consists of an electrically heated, fine-wire element (0.00016 inch in diameter and 0.05 inch long) supported by needles at its ends. The hot wire anemometer is the most popular kind of constant-temperature anemometers. To determine the velocity, an anemometer detects change in some physical property of the fluid or the effect of the fluid on a mechanical device inserted into the flow. Anemometer Introduction to Air Velocity MeasurementĪn anemometer is an instrument used to measure the speed or velocity of gases either in a contained flow, such as airflow in a duct, or in unconfined flows, such as atmospheric wind.
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