A Complete Guide to Anemometers

An anemometer is an instrument that measures wind speed, air pressure and air velocity, and is sometimes referred to as a wind speed meter. The first ones were invented hundreds of years ago to roughly measure wind, whereas today they’re highly accurate monitors which can provide a variety of data.

They’re available in manual and digital forms, and can be used to measure both the speed and velocity of gases in a contained flow, as well as in unconfined flows, such as atmospheric wind.

Did you know? The word ‘anemometer’ comes from the Greek word for wind, which is ‘anemos’.

In a scenario that requires information on the speed and direction of the wind, this device is vital.

Whether monitoring the safety of tall structures, controlling wind turbines, manoeuvring ships, or studying the effects of wind, there are significant benefits to using this tool.

That’s why they’re used at almost every weather station – from the Arctic through to hot equatorial regions. That’s because wind speed helps indicate a change in weather patterns, for example, an approaching storm, which is important for pilots, engineers, and climatologists.

This means they’re extremely important for meteorologists, who study weather patterns, as well as physicists, who study the way air moves.

Large wind turbines even have built-in anemometers to measure the wind speed, which can activate the brakes to stop them rotating if the wind blows too fast.

Other uses:

• Sailors or windsurfers wanting to measure wind speed or wind direction
• People paragliding or flying drones and remote-controlled planes can check to see if weather conditions are safe
• Scientists who monitor environmental conditions
• For HVAC installation and repair, as a scientific way to measure airflow in an air conditioning, heating or ventilation unit
• Monitoring cranes in construction work, as unsuitable weather conditions can pose a risk to staff and equipment
• Weather always needs to be considered for outdoor events, especially if there are temporary structures, so they ensure safety by monitoring weather conditions
• As weather forecasts don’t provide live data, these devices are useful for monitor airfields and airports to reduce risk to planes flying at low altitude during take-off and landing

These are the simplest type and among the most accurate.

They feature a set of either two, three or four cups which spin on a mounted pole by the wind.

As wind levels pick up, the cups spin faster, with the instrument capturing the speed of the wind which is then shown on a digital display.

They’re mostly designed to be mounted on structures such as buildings or sailboats, but some handheld models are available.

Invented in 1994 by geologist Dr Andreas Pflitsch, these devices determine instantaneous wind speed and air velocity by measuring the sound waves travelling between a pair of transducers.

An ultrasonic anemometer doesn’t have any moving parts and uses sensors to detect even small changes in the wind. They typically feature four sensors arranged in a square.

Anemometers have been around for hundreds of years, with the first model created by Italian architect Leon Battista Alberti in 1450 to show wind velocity.

It featured a disk placed perpendicular to the wind, which would rotate from the force of the wind and incline as the wind moved.

This initial design from the 15th century was then reinvented by astronomer and physicist John Thomas Romney Robinson in 1846. This model was the prototype for the modern-day version, featuring a vertical spindle with four arms. Cups were then attached to each of these arms, and when the wind blew the cups captured it, which caused the spindle to rotate to show the wind speed.

Most digital models have different measurement options. This allows calculations of the wind speed to be displayed in either mph, km/hour, mi/hour, ft/second, ft/minute, or knots. On the instrument, press the unit button to view the range of measurement options and select the relevant one.

Once it’s showing the correct unit of measurement, it’s ready to calculate the speed. Simply hold the device in the air, ensuring the device is facing the direction of the wind.

The instrument will then calculate the wind speed and it’ll appear on the easy-to-read digital display. When measuring the airflow outside, the reading will change as the wind naturally speeds up and slows down with each gust.

This type is simple to use and easy to understand and offers a high level of accuracy thanks to the electronic circuits and computers which are included. This means they’re widely used across a variety of industries, as well as for outdoor activities such as hiking or camping.

This is the most common and well-recognised type, featuring four cups arranged at 90-degree angles. Unlike digital models which have a display screen, this type does require some mathematical skill.

Start by marking one of the cups as a reference point, as this will be the cup to count in order to determine how fast they’re rotating around the axis.

Hold the device in the wind, and count the number of times it spins per minute. Record the number of times it spins on a piece of paper, and do this four times to get enough information to calculate the average number of spins per minute.

Calculate the average wind speed by adding up the recorded numbers and then divide that number by four. This will calculate the average number of rotations per minute.

Accuracy is an important quality of an anemometer. A high-quality device will provide a wind speed reading accurate to approximately ±0.5 m/s (±2km/h or ±1mph).

It’s important to remember that environmental wind speed isn’t constant, as it’s changing all the time. When monitoring a wind tunnel, the speed will be constant and precise measurements can be counted, however when outside any measurement is going to be a rough guide.

For a range of alternative products for gas and air measurement, click here.

To make sure anemometers are reliable and precise, they should be regularly calibrated.

This is the procedure of checking the accuracy of a measuring instrument – as well as the adjustment to align it with the standard. The process allows equipment to produce more accurate results than would’ve otherwise been possible.

It’s vital to regularly calibrate devices, as their accuracy will reduce over time and with use. The permitted frame of calibration error is 5% – with any error beyond that potentially affecting the performance of the tool quite seriously, which could lead to liability for product failure.