Build your own Anemometer

Build your own Anemometer
Wind speed is measured using a device
called an Anemometer.
Find out how to build your own one by
following the instuctions below.
What you’ll need:
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5x paper or plastic cups
2x long straight plastic straws
A stapler
A pair of scissors
A drawing pin
A sharp pencil with eraser on end
Paint or paper to cover one cup
(any colour different to the cups)
Step 1
Take four of the cups and punch a
small hole into each about 1.5cm
below the rim.
Step 2
Take one of the four cups and push a
drinking straw through the hole. Fold the end of the straw and staple it
onto the inside of the cup to secure. Take another cup and straw and
repeat this procedure.
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Step 3
Take the fifth cup and punch 4 equally
spaced holes about half way down the
cup.
Step 4
Take one of the cup/straw
combinations and slide the other end
of the straw through two holes of the
fifth (central) cup. Step 5
Paint or cover one of the external
cups in coloured paper so that it is
noticeably different from the others.
Push the coloured cup onto the end of
the straw. Ensure that this cup faces in
the opposite direction. Fold the end of
the straw inside the cup and staple as
before.
Step 6
Repeat this process with the remaining
cup/straw combinations.
Push the pin through the middle of
the centre cup and into the end of the
pencil rubber/eraser as far as it will go.
Your anemometer is ready to use!
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How to use your Anemometer
Your anemometer rotates in the wind. To determine how fast it is, watch the coloured cup
and count how many times it rotates in one minute (RPM, revolutions per minute). Next, calculate the circumference of the circle made by the rotating cups (in metres). Multiply the number of rotations per minute (RPM) by the circumference to give metres per
minute. Drag and friction forces have been omitted from this calculation for simplicity.
Investigation
1. Measure the wind speed at different times of the day. Is it the same in the morning;
the afternoon; the evening?
2. Move your anemometer to another location. Is it windier in other places?
3. Do trees or buildings block the wind?
Did you know?
Wind speed is important for wind energy. Wind turbines need a constant, average wind
speed of 14 miles per hour before they can
generate electricity. That’s why wind farms are
located in windy spots!
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Beaufort Scale
Compare your measurements to this Beaufort Scale to see how windy it is.
Beaufort
number
Wind Speed
Description
Land conditions
km/h
mph
m/s
<1
<1
<0.3
Calm. Smoke rises vertically.
0
Calm
1
Light air
1-5
1-3
0.3 - 1.5
Wind motion visible in smoke.
2
Light breeze
6 - 11
3-7
1.5 - 3.3
Wind felt on exposed skin.
Leaves rustle.
3
Gentle breeze
12 - 19
8 - 12
3.3 - 5.5
Leaves and smaller twigs in
constant motion.
4
Moderate breeze
20 - 28
13 - 17
5.5 - 8.0
Dust and loose paper raised.
Small branches begin to sway.
5
Fresh breeze
29 - 38
18 - 24
8.0 - 11
Branches of a moderate size
move. Small trees begin to sway.
11 - 14
Large branches in motion. Whistling
heard in overhead wires. Umbrella
use becomes difficult. Empty plastic
garbage cans tip over.
6
Strong breeze
7
High wind,
Moderate gale,
Near gale
50 - 61
31 - 38
14 - 17
Whole trees in motion. Effort needed to
walk against the wind. Swaying of
skyscrapers may be felt, especially by
people on upper floors.
8
Gale, Fresh gale
62 - 74
39 - 46
17 - 20
Some twigs broken from trees. Cars
veer on road. Progress on foot is
seriously impeded.
21 - 24
Some branches break off trees and some
small trees blow over. Construction
/temporary signs and barricades blow over.
Damage to circus tents and cannopies.
25 - 28
Trees are broken off or uprooted, saplings
bent and deformed. Poorly attached
asphalt shingles in poor condition peel off
roofs.
29 - 32
Widespread damage to vegetation. Many
roofing surfaces are damaged; asphalt tiles
that have curled up and/or fractured due to
age may break away completely.
9
Strong gale
10
Storm [6],
Whole gale
11
12
Violent storm
Hurricane[6]
39 - 49
75 - 88
89 - 102
103 - 117
≥ 118
25 - 30
47 - 54
55 - 63
64 - 72
≥ 73
≥ 33
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Very widespread damage to vegetation.
Some windows may break; mobile homes
and poorly constructed sheds and barns
are damaged. Debris may be hurled
about.
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