# Anemometers: Accurate determination of wind speed

An anemometer is indispensable for calculating a flow field in an air duct or for calculating the temperature in industrial ventilation systems.

Here, a distinction is made between thermal anemometers and vane anemometers. The latter is the oldest type of anemometer and works similar to a windmill: The air flowing through drives the vanes, which are set in rotation as a result.

Anemometers can be used in a variety of applications:

• Monitoring air conditioning systems
• Monitoring flow fields in technical installations
• Measuring the dimensioning of different ducts
• Determining the air velocity in wind turbines
• Ventilation for underground working places (e.g. mines)

## Vane anemometer

For flow measurements at air outlets and in ventilation ducts as well as for checking the supply and exhaust air at ventilation grills, plate outlets and swirl outlets.

## Thermal anemometer

For flow measurements in ventilation ducts as well as for checking the exhaust air at ventilation grilles, plate outlets and laboratory fume cupboards.

### Multifunction measuring instruments

For all air conditioning and ventilation measurements.

## This is how the measurement works

The amount of time the vanes need for a full revolution gives the wind speed. The velocity of the measured air flow is derived from the measured time. A thermal anemometer, on the other hand, heats up a heating wire that is cooled via an air flow. A higher electricity feed prevents or compensates for the cooling.

The flow velocity is related to the quantity of electricity required, because the heat transfer changes with the flow velocity. Put simply: The higher the flow velocity, the more electric current is flowing.

Do you have any questions?

## Flow measurement: Particularly needed in duct measurement

Flow measurement using an anemometer is particularly important for duct measurements. These check how high the air velocity is in the relevant duct. This reading is particularly indispensable when it comes to ventilation and air-conditioning systems, because each system can only be actually effective and efficient with an air flow at an appropriate speed.

A wind speed measuring device is also used for duct outlets, and here the outlet measurement is relevant. The anemometer reveals small changes that are crucial for the entire system. These changes relate, for example, to the velocity of the air flow and to the volume flow.

The air speed is often underestimated in rooms, yet it has a key influence on the climate in the room. In addition to air velocity, temperature and humidity also play a major role in achieving a pleasant indoor climate, so all three values should always be monitored. The values can be measured using a thermal anemometer.

It’s useful if the selected anemometer for flow measurement provides various additional functions, which allow the mean value of the measured values to be determined, for example. In addition, storage of the latest data is indispensable in order to get a realistic overview of the development of the values.

The advantages of using high-performance anemometers (vane or thermal anemometers) for flow measurement are obvious:

• Air velocities can be monitored
• Simultaneous measurement of temperature and humidity
• Various flow meters available for different applications
• Ensuring the efficiency of systems and equipment
• Easy evaluation of data possible

### Multifunction instruments

For all air conditioning and ventilation measurements.

## Anemometers: Suitable instruments for all applications

Measurement of wind speed and other values is only realistically possible if you use the appropriate instrument and can rely on the capabilities of the instruments. When purchasing a new anemometer, you should therefore check in advance whether the instrument is able to measure the required wind speed and whether it is possible to evaluate the data to the required extent.

In this regard, it is important to be aware that anemometers are equipped differently and that a volume flow hood is used differently from a thermal anemometer. The following instrument features are important when selecting:

• Simple application and operation
• High sensitivity
• Collection of the required data
• Rapid evaluation of the data
• Calculation of mean values

## Measuring wind speed: Conversion of different units

Not only can the anemometers for wind measurement offered by Testo carry out a measurement at only one point and therefore offer so-called spot measurement. Those using appropriate programs can also carry out multi-point measurements. These so-called grid measurements are based on international standards (DIN/ISO/Ashrae).

You can also convert the measured results into different units and display them. With the vane anemometer, for example, you can display the wind speed in Beaufort as well as the wind chill. The values can be displayed in the units m/s, km/h or kts, while conversion to mph and fpm is possible.

### Flow meters from Testo

Testo focuses on the anemometer – that and the required values that need to be collected and calculated. Different anemometer variants are available, so you can find the right anemometer for both indoor and outdoor use. Using the individual instruments is made much easier thanks to the utilization of a smartphone and the associated app.

Moreover, multifunction measuring instruments from Testo are available which allow the simultaneous determination of all relevant data.

### Measuring flow

A flow meter is not only needed as a wind gauge or anemometer for outdoor use, but is also used indoors, as mentioned already. The instrument can significantly simplify numerous measurements and it is possible to combine different measuring instruments with each other. A normal anemometer can be supplemented by a vane probe, so that the volume flow can also be calculated subsequently. Furthermore, it can be used to determine the flow velocity.

The measuring ranges displayed in each case determine the extent to which the various flows are to be recorded. The differential pressure measuring instrument, which is attached directly to the ventilation duct, can also be used for the purpose of flow measurement. Testo offers the right measuring instrument and the necessary accessories for all applications!

You can use the anemometer:

• To carry out measurements indoors and outdoors