Anemometer

What is an anemometer?
An anemometer is a device, a measuring instrument for checking wind speed [gr. Anemos]. Anemometers are available in many different designs and equipment variants. In the following text, you may find some information meant to facilitate the decision when purchasing an anemometer. PCE Instruments is also happy to develop individual measurement solutions for wind monitoring for special applications. Simply contact us.

First of all, to make the right choice of anemometers, the application should be clarified. If this is unclear, just contact us and we’ll give you our assistance. When selecting an anemometer, the design and the measuring principle are primarily in focus. For exact measurements of small wind speeds, the thermal anemometers are often used. In case of a thermal anemometer, also referred to as a hot wire anemometer, an electrical resistor with a defined current and a constant voltage is heated. If a wind flows past the sensor element of the anemometer, this resistor cools down. By measuring the electrical variables of current and voltage, the resistance at a corresponding flow velocity can be calculated. In thermal anemometers, the temperature is often also measured by means of a separate sensor element.
Thermal anemometers are often used to measure the draft flow or to measure flow velocities in ducts. The measurement with a thermal anemometer is often a measurement for directed flows.

Other anemometers used to measure directional flows are the vane anemometers. In contrast to the hot wire anemometer, this wind meter has a wheel, which is driven by the wind. Depending on the model, the actual measurement takes place then via a Hall sensor which registers the individual revolutions, or via an optical sensor, which scans a reflex mark attached to the impeller. A significant difference compared to the hot wire anemometers is that here the moving parts are needed to measure the wind. A disadvantage is that a certain wind speed is required till a measurement is carried out. This initial flow is often between approx. 0.4 m / s ... 0.6 m / s, depending on the design. Thus, it is not possible to measure very small wind speeds with vane anemometers.

Another type of the moving anemometers is the cup anemometer. Anemometers of this type are used when the wind or a flow should be measured regardless of the direction. These anemometers are often applied for stationary wind measurement and wind monitoring.

A special design of the anemometer is the Pitot tube anemometer. A Pitot tube anemometer calculates a flow velocity based on the difference between two pressures. Via a special Pitot tube probe, the anemometer measures the ambient pressure in a duct and the incoming pressure that affects the probe. The difference between the two pressures gives the flow rate. Pitot tube anemometers are often used at very high flow velocities. These anemometers are known from racing or aircraft construction.
If the design and the measuring principle corresponding to the measurement task of the anemometer have been selected, the device with the correct display has to be found.

Here, as well as for many other measuring instruments from the assortment, there are many different models.
For example, there are models which merely display the flow velocity and give the user the information about the measured value. Furthermore, there are anemometers, which have interfaces, which make it possible to transmit the measured value to a PC. In addition, there are anemometers, which can be used as a multifunction device. These anemometers can, for example, additionally determine temperatures or flows in watercourses. Wind warning systems complete the assortment of anemometers. Special anemometers from the assortment of PCE Instruments are able to calculate, besides the wind velocity, also the volumetric flow in ducts.
The user only has to set the duct area in the device and the anemometer displays the volume flow directly. In addition to the anemometers, which consist of the entire measuring chain, i.e. the sensor + display, there are also just sensors available in the range of the PCE Instruments products. The anemometer sensors usually have a signal output, which can be evaluated by external evaluation devices such as data loggers, alarm units, displays or PLCs.
These anemometers are often used for stationary wind measurements. In accordance with the application, we would like to recommend the following anemometer types. This overview can help you find the right anemometer for the current application.

Application Anemometer Type

-Low wind speeds in ducts with little access Hot wire anemometer
-Wind speeds in ducts at vent outlet Vane anemometer High flow velocity in a duct Pitot tube anemometer
-Control of air-conditioning systems Hot wire or vane anemometer
-Leak testing / draft measurement Hot wire anemometer
-Wind qualification for wind power plants Cup anemometer
-Wind testing in sailing Vane or cup anemometer

Should you have any further questions regarding anemometers from PCE Instruments, you can always call the technical consulting hotline of PCE Instruments: UK: 02380 - 987 030 or US: (561) 320-9162. The colleagues will ask you specific questions about your application and suggest the best suited products for the solution of your measurement task. Should the anemometers from our standard range not be suitable for your application, we would be pleased to work out a solution for your task. For example, we are able to develop autarkic anemometers with remote access for stationary wind measurements.

The anemometer (from Greek anemos = wind) is used to measure the wind speed. In standard, the wind speed is measured at a height of 10 m, because the ground speed varies from place to place significantly. Depending on the design of the anemometer, the measurement can be carried out, for example, thermally (thermo-anemometer), by wind cooling of a hot wire or mechanically (impeller anemometer) or via the pressure (Pitot tube anemometer). The latest technology uses ultrasound. These types of devices are still very expensive compared to the value added because of the better result.

In many models, together with the cross-sectional area, for example, of a flow channel, the flow rate may also be indicated directly on the display. This saves the complicated conversion, since the formulas stored in the measuring devices also include the weightings for flow edge areas or core flows. When using the anemometer, please, always pay attention that you hold the probe of the measuring device (the propeller, the thermal flag or the Pitot tube) centrally in the middle of the flow and absolutely in the flow direction. Or cut off the flow cross-section (for devices with mean value formation) in the form of an ellipse to obtain the optimal results. On many of the anemometers, the directional arrows are printed.

Please, always observe the enclosed instructions for handling. If you hold the sensor in the wrong direction, it may lead to destruction. This applies also to the devices with impeller. The impeller wheels have a predetermined direction of rotation. In the case of an anemometer with a thermal operating principle, please, make sure, that the air you want to measure does not contain any dust particles, because the thin flag can be easily destroyed by tiny impacting particles. Since the sensor is the most important and most expensive part of the device, the entire anemometer is unserviceable then. So, for an easily loaded media, use better an impeller anemometer or starting from a minimum flow velocity of 5 m / s – an anemometer with Pitot tube. These devices are very accurate, extremely robust and cover a wide speed range

Each HVAC system must meet the current requirements and in particular, DIN EN 12599, which means that the equipment should pass a series of tests before full commissioning and regular operation. The methods applied as well as the measuring instruments used for the testing purpose must all meet the requirements and be approved. The European standards go through the modifications and tend to change with the time, that is why it is especially important for the producers and users to stay up-to-date, so that the equipment always worked in compliance with the standards. DIN EN 12599 refers to the test procedures before the ventilation system is handed over. The test may vary, from the simplest ones, to the more detailed and comprehensive, if there is a need for that. It means that the systems must be checked in the process of their manufacturing, installation, before and after commissioning and of course, during the operation. Only with the help of the certified auxiliary devices, like, for example, the pitot tube anemometer PCE-HVAC 2 and also the anemometer PCE-PDA 10L, the check may be carried out professionally and quickly. Such devices are capable to efficiently determine the most important characteristics for the HVAC system: airflow, air pressure, air velocity, ambient temperature and detect whether there are deviations from the required parameter ranges. Application of these measuring tools provides confidence that the ventilation system under test is capable to be in operation and provide the best and most comfortable ambient conditions.

Air flow measurements are essential for many spheres of life, even including household (HVAC systems, extract grilles). Depending on the peculiarities of application (high/ mid/very low flow velocity) or location (inside pipes and ducts or outside wind), different types of anemometers may be preferable.

Vane anemometer in its design reminds a small propeller and it suitable for both, measurements of the air flow inside the systems, as well as for wind speed outside. Since wind never has a very stable and monotonous flow direction, vane anemometer is adjustable to following the changing direction of the wind, in order to measure the correct speed. The vanes may be performed in different sizes and thus, be applied in very heavy-to-reach places.

Vane anemometers are characterized by high sensitivity and that is why are perfect for even small speeds measurements. This makes them very suitable for kindergartens, schools or offices where, as a part of health-care system, it is required to monitor whether drafts occur. The same applies to agriculture, since sufficient and correct air conditioning in the stalls and stables is important for successful breeding. For the measurements of hot air flows, vane should be thermoresistant. An advantage of this type of anemometers is that they are resistant to contaminants which may occur in ducts and ventilation systems.

Vane anemometer is a good auxiliary tool during various construction tasks and in mining. The vane itself is reliably protected and thus, damage risk during operation is low. Besides that, modern devices have integrated functions of measuring further important parameters, like air temperature, air humidity or volumetric characteristics of the air masses. Even if the measurements are carried out inside the no-access ducts or HVAC systems, the information can be collected, and due to the possibilities of the digital devices, processed and viewed on the PC in real time or later. The measurement units may be selected, depending on the application (m/s, km/h, FPM or even knots for marine aplications)  .

As many other economical branches, agriculture is a complex mechanism, successful development and functioning of which is determined by a wide range of natural influencing factors. Wind and temperature are among them. In spite of application of new modern technologies and machines, agriculture still is often dependent on the “behavior” of nature. Application of such auxiliary tools as anemometer helps the professional farmers and gardeners to better evaluate the environmental situation and take the corresponding measures in order, for example, to protect the plants, to get prepared for the changes, to carry out the required procedures, for example, fertilizing or spraying, in the most efficient way.

Visual evaluation may be enough for a small garden, but when it goes about big farms, huge fields, significant amounts of crops, application of the professional anemometer is highly recommended. Accurate detection of wind, determination of its strength and direction, as well as the ambient temperature, provides valuable information for the farmers as for when to plant, whether the necessary pollination happens naturally or not, because or the strong wind, when to harvest or how to protect the plants in case of the coming hurricane. Depending on the area, strong wind may cause sand or dust storms which may lead to aggravating consequences in the agricultural sector. Application of the anemometer may also take place on the stage of choosing, for example, the field or place for the future agricultural object, since it helps to get an overview of the typical weather conditions in the area and evaluate the perspective for the future. Prevailing winds for the particular area may tell a lot about what type of plants will be the best and easiest to grow, as well as how to plant them so that the harvest was not destroyed by the seasonal winds. Wind rose should be taken into consideration before the agricultural object is finally selected, especially if it goes about long-term use.

Absence of wind as well extreme wind gusts may be extremely harmful for the plants at different stages: sprouts, plants at the stage of blossom or ready to be harvested (fruits, vegetables, crops). Monitoring of the ambient conditions with the help of the modern anemometers provides the farmer with the information continuously and thus allows for timely adjustment and preparation, which in its turn, helps to do the best possible for the plants and harvest. Agriculture – is a sector requiring a lot of efforts, hard work and dedication as well as involvement of modern expensive machines. The more annoying it is when the uncontrollable weather condition cause damages for no reason. With the help of the measuring tools, many problems may be prevented, and even if not prevented, then significantly minimized, which is of a great importance in this field.

The presence of the ventilation, heating and often air conditioning systems is a standard thing in the modern buildings. Nevertheless, just to install these systems is not enough; more important is to carry out regular control of the systems in operation. Only due to the flawless functioning of the HVAC system, the indoor air of a very good quality may be provided. Of course, there is a number of influencing factors, such as the area of the premises, the outdoor temperature, the ambient temperature, the presence of the natural ventilation, like windows, but a lot still depends on how correctly the air masses move in the ventilation ducts.

The microclimate that is created in a certain space over some time may be a good indicate whether the HVAC system works correctly or not. Not only the air may become “heavy”, sometimes too dry, and sometimes – too humid, but also mold and stains may appear on the walls, the excessive moisture may gather on the windows as condensate, and there may be a permanent unpleasant smell that does not disappear even after a short airing. The most reliable way to check and detect some problems is to apply the corresponding measuring devices that in no time at all may clearly detect the problem and also determine the level of it. Anemometer, depending on the design and specifications, very accurately measures the flow of the air in the duct either by being brought close to the ventilation or by being placed in the duct itself. The choice of the correct model depends also on what type of measurement is required: for heating system, for ventilation of for the air-conditioning, also on the power of the system and the speeds which are expected. Not always the values beyond the range indicate the fault or serious problem. It may be an indication of a dust accumulation in the duct, which can be easily eliminated by regular cleaning.

The reasons for problems in the HVAC system may be numerous, and caused by outer factors, especially if it goes about apartment or office in the multistoried building, or by the local (incorrect choice of the system for the area, dust, dirt or fat accumulation, for example, in the kitchens, breakage). Nevertheless, application of the anemometer may give a timely or even preliminary indication about the growing problem. This provides from one side, the possibility to maintain the most comfortable microclimate, and from the other, sufficient health care for those people who spend a lot of time in the room or building where the HVAC system is under control. By measuring the volume of the air that goes through the system during a certain time period, it is possible to estimate whether the condition comply with the regulations and norms of the Health Organizations.

Anemometer also finds its application even before the system is set into operation, especially at the enterprises and factories. The system should be powerful enough to cope with huge amounts of air and provide qualitative ventilation, and calculation carried out also with the help of anemometers can be taken as the basis for approval or disapproval for commissioning. Air analysis and in particular, monitoring of the condition of the HVAC systems is a complex task, which requires professional approach, when many parameters of air should be accurately measured. Regular routine checks involving the application of such measuring devices, as anemometer, help to keep the system under control and in the best working condition for a long time.