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An anemometer is a device used for measuring wind speed, and is a common weather station instrument. The term is derived from the Greek word anemos,which means wind, and is used to describe any wind speed measurement instrument used in meteorology . The first known description of an anemometer given by Leon Battista Alberti in 1450.



Velocity anemometers

Cup anemometers

Cup anemometer animation

A simple type of anemometer was invented in 1845 by Dr. John Thomas Romney Robinson, of Armagh Observatory. It consisted of four hemispherical cups, each mounted on one end of four horizontal arms, which in turn were mounted at equal angles to each other on a vertical shaft. The air flow past the cups in any horizontal direction turned the shaft in a manner that was proportional to the wind speed. Therefore, counting the turns of the shaft over a set time period produced the average wind speed for a wide range of speeds. On an anemometer with four cups, it is easy to see that since the cups are arranged symmetrically on the end of the arms, the wind always has the hollow of one cup presented to it and is blowing on the back of the cup on the opposite end of the cross.

When Robinson first designed his anemometer, he asserted that the cups moved one-third of the speed of the wind, unaffected by the cup size or arm length. This was apparently confirmed by some early independent experiments, but it was incorrect. Instead, the ratio of the speed of the wind and that of the cups, the anemometer factor, depends on the dimensions of the cups and arms, and may have a value between two and a little over three. Every previous experiment involving an anemometer had to be repeated.

The three-cup anemometer developed by the Canadian John Patterson in 1926 and subsequent cup improvements by Brevoort & Joiner of the USA in 1935 led to a cupwheel design which was linear and had an error of less than 3% up to 60 mph (97 km/h). Patterson found that each cup produced maximum torque when it was at 45 degrees to the wind flow. The three-cup anemometer also had a more constant torque and responded more quickly to gusts than the four-cup anemometer.


Three-cup anemometers are currently used as the industry standard for wind resource assessment studies.

Vane anemometers

One of the other forms of mechanical velocity anemometer is the vane anemometer. It may be described as a windmill or a propeller anemometer. Contrary to the Robinson anemometer, where the axis of rotation is vertical, the axis on the vane anemometer must be parallel to the direction of the wind and therefore horizontal. Furthermore, since the wind varies in direction and the axis has to follow its changes, a wind vane or some other contrivance to fulfill the same purpose must be employed.

An vane anemometer thus combines a propeller and a tail on the same axis to obtain accurate and precise wind speed and direction measurements from the same instrument.[2] The speed of the fan is measured by a rev counter and converted to a windspeed by an electronic chip. Hence, volumetric flowrate may be calculated if the cross-sectional area is known.


Vane anemometers
A vane style of anemometer 
Helicoid propeller anemometer incorporating a wind vane for orientation. 
Hand-handled low-speed vane anemometer 

Hot-wire anemometers

Hot-wire sensor


Several ways of implementing this exist, and hot-wire devices can be further classified as CCA (constant current anemometer), CVA (constant voltage anemometer) and CTA (constant-temperature anemometer). The voltage output from these anemometers is thus the result of some sort of circuit within the device trying to maintain the specific variable (current, voltage or temperature) constant, following Ohm's law.



An industrial version of the fine-wire anemometer is the thermal flow meter, which follows the same concept but uses two pins or stings to monitor the variation in temperature. The stings contain fine wires, but encasing the wires makes them much more durable and capable of accurately measuring air, gas, and emissions flow in pipes, ducts, and stacks. Industrial applications often contain dirt that will damage the classic hot-wire anemometer.

Drawing of a laser anemometer. The laser light is emitted (1) through the front lens (6) of the anemometer and is backscattered off the air molecules (7). The backscattered radiation (dots) re-enters the device and is reflected and directed into a detector (12).

Laser Doppler anemometers


2D ultrasonic anemometer with 3 paths

Sonic anemometers

3D ultrasonic anemometer

Sonic anemometers, first developed in the 1950s, use ultrasonic sound waves to measure wind velocity. They measure wind speed based on the time of flight of sonic pulses between pairs of transducers. Measurements from pairs of transducers can be combined to yield a measurement of velocity in 1-, 2-, or 3-dimensional flow. The spatial resolution is given by the path length between transducers, which is typically 10 to 20 cm. Sonic anemometers can take measurements with very fine temporal resolution, 20 Hz or better, which makes them well suited for turbulence measurements. The lack of moving parts makes them appropriate for long-term use in exposed automated weather stations and weather buoys where the accuracy and reliability of traditional cup-and-vane anemometers is adversely affected by salty air or large amounts of dust. Their main disadvantage is the distortion of the flow itself by the structure supporting the transducers, which requires a correction based upon wind tunnel measurements to minimize the effect. An international standard for this process, ISO 16622 Meteorology—Sonic anemometers/thermometers—Acceptance test methods for mean wind measurements is in general circulation. Another disadvantage is lower accuracy due to precipitation, where rain drops may vary the speed of sound.

Since the speed of sound varies with temperature, and is virtually stable with pressure change, sonic anemometers are also used as thermometers.

Two-dimensional (wind speed and wind direction) sonic anemometers are used in applications such as weather stations, ship navigation, wind turbines, aviation and weather buoys. Three-dimensional sonic anemometers are widely used to measure gas emissions and ecosystem fluxes using the eddy covariance method when used with fast-response infrared gas analyzers or laser-based analyzers.

There are different technologies solution for Two-dimensional wind sensor.

  • Two ultrasounds paths: These sensors have 4 arms. This design is commonly used by wind sensor manufacturers because it's easier to develop compare to the three ultrasounds paths. The disadvantage of this type of sensor is that when the wind comes in the direction of an ultrasound path, the flow around the arms introduces aerodynamic turbulences which perturb the measurements and the sensor will lose accuracy.
  • Three ultrasounds paths: These sensors have 3 arms. They are developed by some wind sensor manufacturers because they give one path redundancy of the measurement which improves the sensor accuracy and minimizes the aerodynamic turbulences.

Acoustic resonance anemometers

Acoustic resonance anemometer

Acoustic resonance anemometers are a more recent variant of sonic anemometer. The technology was invented by Dr Savvas Kapartis and patented (Acu-Res®) by FT Technologies in 2000.[5] Whereas conventional sonic anemometers rely on time of flight measurement, acoustic resonance sensors use resonating acoustic (ultrasonic) waves within a small purpose built cavity in order to perform their measurement.

Acoustic resonance principle

Built into the cavity is an array of ultrasonic transducers, which are used to create the separate standing-wave patterns at ultrasonic frequencies. As wind passes through the cavity, a change in the wave’s property occurs (phase shift). By measuring the amount of phase shift in the received signals by each transducer, and then by mathematically processing the data, the sensor is able to provide an accurate horizontal measurement of wind speed and direction.

Acoustic resonance technology enables measurement within a small cavity, the sensors therefore tend to be typically smaller in size than other ultrasonic sensors. The small size of acoustic resonance anemometers makes them physically strong and very easy to heat and therefore resistant to icing. This combination of features means that they achieve high levels of data availability and are well suited to wind turbine control and to other uses that require small robust sensors such as battlefield meteorology. One issue with this sensor type is measurement accuracy when compared to a calibrated mechanical sensor. For many end uses, this weakness is compensated for by the sensors’ longevity and the fact that it does not require re-calibrating once installed.

Ping-pong ball anemometers


This type of anemometer is mostly used for middle-school level instruction which most students make themselves, but a similar device was also flown on Phoenix Mars Lander.[6]

Pressure anemometers

Britannia Yacht Club clubhouse tour, burgee, and wind gauge on roof


Plate anemometers


Tube anemometers

Tube anemometer invented by William Henry Dines. The movable part (right) to be put on top of the fixed part (left).
Instruments at Mount Washington Observatory. The pitot tube static anemometer is on the right.
The pointy head is the pitot port. The small holes are connected to the static port.





Pitot tube static anemometers

Modern tube anemometers use the same principle as in the Dines anemometer but using a different design. The implementation uses a pitot-static tube which is a pitot tube with two ports, pitot and static, that is normally used in measuring the airspeed of aircraft. The pitot port measures the dynamic pressure of the open mouth of a tube with pointy head facing wind, and the static port measures the static pressure from small holes along the side on that tube. The pitot tube is connected to a tail so that it always makes the tube's head to face the wind. Additionally, the tube is heated to prevent rime ice formation on the tube.[8] There are two copper lines from the tube down to the devices to measure the difference in pressure of the two lines. The measurement devices can be manometers, pressure transducers, or analog chart recorders.[9]

Effect of density on measurements


Effect of icing

At airports, it is essential to have accurate wind data under all conditions, including freezing precipitation. Anemometry is also required in monitoring and controlling the operation of wind turbines, which in cold environments are prone to in-cloud icing. Icing alters the aerodynamics of an anemometer and may entirely block it from operating. Therefore, anemometers used in these applications must be internally heated.[10] Both cup anemometers and sonic anemometers are nowadays available as a heated version.

Instrument location

In order for wind speeds to be comparable from location to location, the effects of the terrain needs to be considered, especially in regard to height. Other considerations are the presence of trees, and both natural canyons and artificial canyons (urban buildings). The standard anemometer height in open rural terrain is 10 meters.[11]

See also



  1. "History of the Anemometer". Logic Energy. Retrieved 14 April 2013. 
  2. World Meteorological Organization. "Vane anemometer". Eumetcal. Retrieved April 6, 2014. 
  3. "Hot-wire Anemometer explanation". eFunda. Archived from the original on 10 October 2006. Retrieved September 18, 2006. 
  4. Iten, Paul D. (June 29, 1976). "Laser doppler anemometer". United States Patent and Trademark Office. Retrieved September 18, 2006. 
  5. European Patent No. EPO 801311 A and USA Patent No. 5,877,416 (1999)
  6. "The Telltale project." Archived August 13, 2014 at the Wayback Machine
  7. Dines, W H (1892). "Anemometer Comparisons". Quarterly Journal of the Royal Meteorological Society. Royal Meteorological Society (Great Britain), James Glaisher. 18: 168. doi:10.1002/qj.4970188303. Retrieved 14 July 2014. 
  8. "Instrumentation: Pitot Tube Static Anemometer, Part 1". Mt. Washington Observatory. Retrieved 14 July 2014. 
  9. "Instrumentation: Pitot Tube Static Anemometer, Part 2". Mt. Washington Observatory. Retrieved 14 July 2014. 
  10. Makkonen, L. et al. (2001) Anemometry in icing conditions. Journal of Atmospheric and Oceanic Technology 18:1457-1469
  11. Oke, Tim R. (2006). "3.5 Wind speed and direction". Initial Guidance to Obtain Representative Meteorological Observations At Urban Sites (PDF). Instruments and Observing Methods. 81. World Meteorological Organization. pp. 19–26. Retrieved February 4, 2013. 


External links