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How do anemometers measure wind speed?

Posted by HoldPeak on 17th Dec 2019

When you hear weather forecasters warning of how fast the wind is going to blow, do you ever stop to think how they're going to measure it? Wind isn't something you can see very easily, so you can hardly time it with a stopwatch like you'd measure the speed of an Olympic sprinter or a race car! Fortunately, scientists are amazingly inventive people and they've come up with some pretty clever ways of measuring wind speed with gadgets called  anemometers. Let's take a closer look at how they work! 

HoldPeak Anemometer

Thinking about anemometers HoldPeak anemometer

Some people think wind turbines are unsafe because gales and storms could make them spin dangerously fast. That's not actually true: all large wind turbines are fitted with brakes that stop them rotating if the wind blows too hard (and they have built-in anemometers to measure the speed as well). But it's certainly true that wind turbines turn faster—and generate more electricity—the harder the wind is blowing. There you have a clue to how a basic anemometer could work. HoldPeak wind speed guage

Suppose you build yourself a miniature, table-top wind turbine and connect it to an electricity generator (effectively an electric motor wired up backwards so it makes an electric current when you spin its central axle around). The faster the rotor blades turn, the quicker the generator spins, and the higher the electric current it will produce. So if you measure the current, you have a basic way of measuring the wind speed. You have to calibrate an instrument like this before you use it, of course. In other words, you'd need to know how much current is generated by a few winds of known speed. That would help you figure out the mathematical relationship between wind speed and electric current so you could figure out the speed of an unknown wind simply by measuring the current. HoldPeak wind speed meter