Anemometer: what is it and how does it work?
The anemometer is an instrument that measures the wind (speed, direction and pressure). Wanting to be more precise, an anemometer is able to calculate the speed of gases in a controlled flow (for example the flow of air in a duct) or uncontrolled (such as the atmospheric wind).
The
term anemometer is Greek, from
anemos (wind) and
metron (measure). The authorship is attributed to the Italian architect Leon Battista Alberti (in 1450).
What is an anemometer?
An anemometer is a
wind detector device that identifies speed, direction and pressure. In fact, they are important tools for
meteorologists at their stations.
In order to evaluate the speed the anemometer analyzes the
changes in the properties of the fluid or the effect of the same on a mechanical device put into contact.
How does an anemometer work?
The most common anemometer has several cups (three or four) attached to horizontal arms. When the wind blows the cups rotate and turn a rod to which they are connected. The more the wind blows, the more the barrel turns. In this way the anemometer counts the number of rotations and consequently calculates the average wind speed in a given period.
Other types of anemometers calculate the wind speed in very different ways (read later).
You may have heard the term anemometer when describing a particularly adverse weather event.
Have you wondered
what an anemometer is and how does it work? Read on to learn more.
What is an anemometer used for?
A wind anemometer is a
sensor for measuring the speed in a certain direction on a certain plane.
They are also important for the
work of physicists , who among their skills also study the way air moves.
Who Uses Anemometers? Pilots, engineers and climatologists
Wind speed allows you to predict changes in weather patterns, such as an approaching storm.
An anemometer is a fundamental tool for any job
is
affected by the weather .
Those who fly drones, planes or helicopters must constantly measure the wind speed to prevent accidents. Anemometers are also important on ships (wind speed determines the size of the waves).
Finally, anemometers are used in every
meteorological station , at whatever latitude it is.
Anemometers in space
Aerospace engineers and physicists use special
laser anemometers , for example in speed experiments. In fact, laser anemometers are able to measure the wind speed around spacecraft. The goal is to make these vehicles more aerodynamic in carrying out their missions.
NASA is planning a mission to the planet Venus with an anemometer to evaluate the wind speed and evaluate the characteristics of the atmosphere of that area.
Difference between anemometer and wind vane
Weathervanes also show wind direction, but are mostly decorative tools. The difference is that a wind vane, unlike an anemometer, is not able to provide such precise information on wind speed.
Brief history of the anemometer
The anemometer instrument
has changed very little since its first development during the 15th century:
- In 1450 the Italian inventor Leon Battista Alberti designed it;
- In 1846, John Thomas Romney Robinson improved the design;
- In 1926, Canadian meteorologist John Patterson designed a three-cup anemometer;
- In 1991 Derek Weston introduces the possibility of measuring the direction of the wind;
- In 1994 Andreas Pflitsch invented the sonic anemometer.
Types of wind meters
On the market there is a
wide choice of types of anemometer to directly measure wind and air speed.
We can start immediately by making a macro distinction between two groups:
- Vane, thermal and cup anemometers calculate the average speed;
- Hot wire anemometers evaluate turbulence characteristics as transverse measurements.
Cup anemometer for meteorological stations
The simplest type of anemometer is the cup anemometer.
It consists of three or four hemispherical cups, each mounted at the end of horizontal arms, which in turn are mounted at regular distances on a vertical shaft. The flow of air passing over the cups in a horizontal direction causes the cups to rotate according to the wind speed.
By counting the revolutions of the cups in a predetermined time, the average wind speed can be estimated.
Three-cup anemometers are currently used as an industry standard for wind resource assessment studies, such as in sensors attached to
window control units .
The cup wind meter is used in meteorological stations and measures the speed on a plane perpendicular to the axis of the rotation cups.
Hot wire or vane anemometer?
Sometimes called wind or air speed meters, anemometers are normally classified as hot wire or vane.
- The hot wire anemometer is the best choice for accurate measurement of air flows at very low speeds (e.g. below 2000 ft / min). Some models are designed to measure speeds of 15,000 ft / min, while still maintaining very accurate measurement capability at significantly lower speeds. To measure the air speed, the vane anemometer relies on an impeller;
- Vane anemometers are only the best choice for measuring wind speed. Many have user selectable units of measurement: feet / min, m / s, MPH, km / h and knots, to allow for a wide range of applications. A thermo anemometer is a hot-wire or vane wind sensor capable of also measuring the air temperature;
- The hygrothermometer anemometers have the characteristics of a thermo anemometer and a humidity sensor that provides the customer with complete environmental information.
Portable vane anemometer
The
rotating mechanical anemometer can be classified as vane or propeller. With this type of sensor the rotation axis must be horizontal like the wind flow. In open spaces the wind changes direction and the axis must take this into account.
The vane anemometer is also available with various additional functions.
Portable thermal anemometers
Thermal anemometers use a very thin wire or a heated element. The air flow has a cooling effect. Since the electrical resistance of most metals depends on the temperature of the metal, a relationship can be obtained between the resistance of the wire and the flow velocity.
The hot wire anemometer is delicate and has a high frequency response and good spatial resolution compared to other measurement methods.
Thermal anemometers with speed and temperature analysis
Thermal anemometers have the smallest sensor. Thermal sensors are capable of measuring both speed and temperature. The data recording systems allow the user to analyze (also graphically) the characteristics of the flow and the data.
They are often used in wind tunnels to evaluate circuit boards and heat sinks.
