Wind Speed Meter

Many people know the red-and-white-striped windsocks as simple wind speed meters. They show how strong the wind is and from which direction it is blowing, and are easily recognizable even from long distances. Each of the three red and two white rings corresponds to 1 wind force according to Beaufort scale. When the wind force is five and above, the windsock is horizontal, at wind force three it bends after the third ring. This indicator, which can be seen over long distances, helps the road users on the road sections and bridges under threat of crosswinds to adapt their driving style to the wind conditions timely. At helipads and airfields, they inform the pilots taking off and landing about the current wind situation.

Digital wind speed meters seldom offer this recognizability over long distances, but they do offer the possibility to show the data digitally on a display, to store it electronically and to transmit it. Some wind speed meters are equipped with interfaces that allow direct control of acoustic warning systems or other devices depending on the wind strength. Electronic wind speed meters can measure either wind direction, wind speed or both.

The wind speed is expressed either as wind force according to Beaufort or in common speed units. These include metres per second, kilometres per hour and, in maritime and aviation nodes. One node corresponds to one nautical mile per hour. In Anglo-Saxon-speaking countries, the units miles per hour and feet per minute are also frequently used. It is practical if the wind speed meter displays the data directly in the required unit.

The wind direction is determined according to the compass direction from which the wind comes. Instead of indicating the cardinal directions with 16 divisions, such as east-northeast, the direction is often indicated as the number of degrees of a 360-degree circle. With the degree indication, the north direction corresponds to zero degrees, the east direction to ninety degrees and the west direction to 270 degrees.

Applications for wind speed meters
Wind speed meters are not only used for accident prevention and traffic control in the road, air and shipping traffic. They are also needed in determining locations for wind power plants and in assessing the emissions from traffic, industry and agriculture. The effects of the noise, exhaust gases and odours on the neighboring areas depend not only on their distance, but also on the wind strength and direction. On the buildings, the wind speed meters are also often used to retract the wind-sensitive attachments such as awnings and external blinds in the event of strong winds. Wind speed meters are also used on some ventilation systems and smoke outlets. There, a fan can be switched on automatically if the natural draught is not sufficient. Wind measurements are also useful before and during certain work in agriculture, such as spreading fertilizers and seeds or mowing light cut material. This makes it easier to assess whether special precautions need to be taken against blowing away or whether it is better to postpone the work to another time. In construction and forestry, certain work must not be carried out in strong winds and the particularly risky because of wind areas must not be entered. These include, for example, roofs, industrial chimneys and cranes, lifting platforms and scaffolding or areas with the trees that are at risk of falling. When assessing the concrete danger situation, not only the wind warnings of the German Weather Service should be taken into account, but also local measurements with the wind speed meter as close as possible to the danger area. The information of the weather service usually refers to a height of 10 m and cannot take into account the local conditions influenced by the buildings and vegetation. Wind speed meters also play an important role in recreational activities, water sports, gliding and ballooning.

Selection criteria for wind speed meters
Wind speed meters work according to different measuring principles. Each of them has advantages and disadvantages and is particularly suitable for certain applications or measuring ranges. A rotatable component – a wind vane – is often used to determine the wind direction. This stable wind vane is aligned by the wind like a textile vane or a weathercock on towers. There are various methods for measuring the speed, three of which are briefly presented here.

Wind speed meters with rotating components
Wind speed meters in which a component is set in rotation can be divided into those that rotate horizontally (with the wind) and those that rotate vertically (at right angles to the wind). The speed is determined by counting the rotational movements. The revolutions are usually recorded without contact via a Hall sensor or via an optical sensor that scans a reflex mark attached to the rotating part. Rotating wind meters require a minimum speed in order to be set in rotary motion. The wind speed meters with horizontally rotating blades or a cup cross are independent of the wind direction. The wind speed meters with vertical blades, on the other hand, must be directed into the wind flow. Permanently installed devices with a stationary impeller can be positioned automatically by combining them with a wind vane. In the case of the handheld devices with a standing impeller, the user must ensure correct alignment. With a suitable rotor design, the rotating wind speed meters are relatively insensitive. They can also be used in the air with a high content of foreign particles.

Wind speed meters with hot wire
Thermal wind speed meters are well suited for measuring low speeds. In these devices, a wire or semiconductor, the electrical resistance of which is temperature-dependent, is heated. The stronger the wind blows, the faster the heat is dissipated. There are two basic methods. Either the heating current is kept constant and the change in voltage is measured by the changed resistance value or the temperature is kept constant and the heating current required for this is measured. The second option is technically more complex, but covers a larger measuring range and automatically measures the temperature of the incoming air as well. Thermal wind meters with several heat sensors can also measure the wind direction in two or even three dimensions. They are thus also suitable for testing flow angles on components and for measuring turbulence.

Wind measurement with special dynamic pressure gauges
Wind speed can also be determined from the pressure difference between still and flowing air. Special Pitot tubes or Prandtl tubes, the measuring tip of which is blown directly by the wind, are used for the measurement. Pitot tubes are particularly suitable for measuring high speeds. These wind speed meters are therefore used for measuring strong winds and gusts as well as on aircraft and racing cars and in the process technlogy.

Mobile or stationary use and storage or transmission of the digital data
In most cases, the field of application already determines whether the wind speed meter is permanently mounted or whether it is used for measurements at different locations. In the case of the wind meters permanently mounted on buildings, the digital measurement data is usually transmitted either via cable or wirelessly to an evaluation unit. Some stationary wind meters also directly control ventilation or shading systems or alarm devices via pulse or analogue outputs when limit values are set. Mobile wind meters are often easy-to-use handheld devices that show the measured value directly on the display. Many of them are equipped with an internal memory so that the measured values can be saved and transmitted later. However, small mobile data loggers without a display are also available. These store the wind speed at set intervals and are later read out on the computer. The setting of these wind meters for continuous measurements and the evaluation of the data are usually done conveniently via the associated software.

Additional measured variables
Many wind meters display the air temperature as an additional value; the other devices also display the air pressure or the air humidity. For orientation measurements at workplaces, there are combined devices that also measure, for example, sound level, humidity and illuminance. For certain environmental measurements, the wind speed meters are also available that can indicate the height above (or below) sea level relatively accurately.

Wind Speed Meter with Vane Sensor
Wind speed meter or anemometer occupies an important position among the measuring equipment when it goes about wind or movement of air mass. Modern anemometers are mechanical or digital up-to-date devices, which are easy to install and easy to use, many of them with an advantage of measuring a raw of other important parameters, such as temperature, pressure and humidity or even determining the wind direction. Anemometers with vane sensor slightly remind the ventilator, which many uses for air cooling. The vanes of the anemometer move under the influence of the air mass, the speed of rotation depends on the speed of the wind, and thus, be measuring the speed of the vane, the speed of the wind may be determined. By counting the number of rotations, the device calculates the speed and the user may see the results on the display. Due to the design of some models, the vane anemometer adjusts to the wind and changes it position correspondingly. For those who are interested in detecting not only the speed of the wind, but also the direction, the vane anemometer is exactly the right choice.
Due to the peculiarity of construction, wind speed meters with vane sensor are suitable for installation in the pipes, channels or ventilation ducts, mines or even application at home. The vane anemometers possess a higher level of sensitivity and that is why the application is meaningful also inside. The vane anemometer is less affected by the presence of dust or contaminating particles in the air that goes through the vanes, nevertheless the blades require regular cleaning to ensure the most accurate measuring results.

Wind Speed Meter with Thermo Sensor
A famous meteorological device, anemometer, or wind speed measuring device finds its application in many spheres where it goes about moving air masses dand where the speed of the air should be measured.
Among the variety of designs there are models that find frequent application and those that are suitable mostly for the laboratory tests. Wind speed meter with thermo-sensor, as follows from the name, is especially suitable for application where not only the speed, but also the temperature of the air is important. It is convenient for both, meteorological measurements as well as targeted measurements at particular locations, for example ventilation systems, or for inspections before the HVAC system’s commissioning. The meter can be applied for maintenance and repair of aerodynamic installations and equipment. Due to the variety of parameters that can be measured with the help of the thermos-sensor, the wind speed meter can also be used for checks of the compliance with the norms and health regulations in the workplace and thus, detection of faults and malfunctions in the ducts and channels, assessment of the condition of engines, for example, in aviation.
The main principle of the thermos-sensor is that the temperature change happens when cooler air mass influences the heated element of the meter, and thus the energy is released. To avoid the temperature drop and to maintain it on the desired level, the regulator is activated. The thermo-sensor may be affected by the air masses coming from different directions, when a so-called turbulence effect happens, and that is why it is often used for this kind of measurements.

Wind Speed Meter with Cup Sensor
Due to a rather simple, but very effective construction of the measuring device, it has become possible to measure the wind speed and many parameters, characterizing moving air masses where it is required or desired. The operating principles of the wind speed sensors lightly differ, but they all perform an important function and wherever it is necessary to check the speed of the wind, or carry out monitoring over a certain period of time, they find an application.
Сup anemometer is one of the most widely spread types of anemometers, the application of which is very versatile, and ranges from meteorological monitoring to sport activities, in which wind plays a decisive role. Outdoor conditions do not depend on people and that is why continuous monitoring of the wind speed with accurate measurement results, especially for particular tasks, is so important. At the same time, wind speed meter with cup sensor is also convenient to use there where the slightest deviations from the norm should be detected and eliminated immediately, since it goes about safety, health and comfort of people, for example, at the enterprises.
In the case of electronic devices, there is no need for the operator to calculate the wind speed, since the devices registers the number of rotations of the cups under the influence of the air mass and displays the final result, which saves a lot of time and excludes the possible errors. Cup sensor is not the best choice for very small speeds, but its advantage is that it copes with wind or air mass blowing from any direction. It is stable and does not require additional adjustment.