Make a tool to measure the wind

By February 10, 2011

If you have ever wondered how fast the wind blows in a pleasant breeze or in tree-toppling gusts (like those from earlier this week), make a simple tool that measures wind speed and use it whenever wind curiosity strikes.

The instructions below guide you to make something called an anemometer that you can take anywhere to find out how fast the wind is blowing at a particular place and time.

Anemos means “wind” in Greek, and anemometers are devices that measure the speed of wind. Commercial anemometers that meteorologists use can be very accurate, but even the simple plan below gets you pretty close.

To make an anemometer, you will need string, fishing line, tape, scissors, a ruler, a protractor, a ping pong ball, a piece of cardboard and a pen.

The ping pong ball will hang down from the protractor on fishing line, so that when the wind blows the ball, the fishing line will line up with an angle on the protractor. From the angle, you will be able to estimate wind speed.

Tape one end of the fishing line to the ping pong ball. From the spot where the tape meets the ball, measure 11 ¾ inches along the fishing line, and hold your fingers on that spot to mark where you should tape the other end of the fishing line.

The protractor should be upside down, so the arc looks like a smile. Across the top, straight part of the protractor, there will be a center-line. Tape the fishing line to this center-line of the protractor.

To attach fishing line more securely, fold the loose end of the fishing line over the top of the protractor and tape it again on the opposite side from the first piece of tape. Cut off any extra.

Check that when your protractor’s straight side is horizontal, the fishing line hangs straight down the center, past the 90-degree mark on the arc.

Tape the protractor to a piece of cardboard to make it easier to hold. Write on your cardboard the wind speeds that correspond to certain angles on the protractor, listed below.

Angle (degrees) 90 86 75 59 43 31 23
Speed (mph) 0 5 10 15 20 25 30

Bring a piece of string outside and watch it hang from your hand for several seconds, moving around in the wind. The direction the string spends most of its time in is the direction of the wind.

Hold on to the edge of the cardboard and point your anemometer into the wind. This will be the exact opposite direction that the string was pointing, since you want to face into the wind.

Notice what angle on the protractor the fishing line lines up with, and find the corresponding approximate speed on the chart that you made. Repeat on different days.

When using your anemometer, you might want to put your numbers in context by thinking about other speeds you are familiar with. For example, an average person walks about 2 mph and runs about 6 mph. Winds above 40 mph can knock trees and signs over.

On windless days, your anemometer can also be fun to see how fast you can blow air out of your mouth. A sneeze comes out of a person’s nose and mouth at between 35 to 100 mph.

No time to make an anemometer? No room in your wallet, purse or backpack? You can use the Beaufort Wind Force Scale, online at http://www.spc.noaa.gov/faq/tornado/beaufort.html, to describe wind speed based on observable land or sea conditions.


Tomorrow, Astronomy Club: A free meeting, suitable for all ages, will begin at 7 p.m. at Explorit’s Nature Center, 3141 Fifth St., Davis.  This month, the group will discuss NASA’s Space Shuttle program as the space shuttles’ final flights are slated for this year. Telescopes will be set up outside, weather permitting, for viewing after the main presentation is over.

— Explorit Science Center’s 3141 Fifth St. site is the location for programs for groups, astronomy club meetings, birthday parties and Summer Science Camp. It is also the hub for Explorit’s traveling programs that reach an 18-county region.  The site is open to the public for special events and to groups by reservation. For more information, call (530) 756-0191 or visit http://www.explorit.org.

Liz Shenaut

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