An anemometer is a device used to measure wind speed or pressure. They are a common fixture at weather stations, providing accurate measurements for forecasts. Because they are a scientific tool, you may think they are complex, but it is easy to make a simple DIY anemometer for your own casual use. You may not get elaborate, detailed information with a completely accurate wind speed, but the concept is the same for a primitive cup anemometer as for a technologically advanced one. The cups catch the wind and then rotate around a base.
five plastic cups
one pencil with eraser
single-hole hole punch
Take four of the plastic cups and poke a hole in them about a half-inch from the rim using the hole-punch.
Punch two holes in the fifth cup across from one another about a half-inch from the rim. Then punch two more holes in the cup, equally spaced between the first holes, and put them about a quarter-inch from the rim.
With the pushpin make a hole in the bottom of the cup with four holes from step 2. Make the hole large enough to fit the pencil through it with the scissors.
Slide one straw through a cup with one hole in it. Bend the end of the straw down about a half-inch and tape it in place inside of the cup so that it is secure.
Insert the other end of the straw through two of the holes in the cup with four holes and then through another cup with one hole. Bend and tape the end of the straw to the inside of the latter cup as you did in step 4.
Repeat both step 4 and step 5 with the remaining two cups, making sure the bottom of each cup is sideways and no openings of any cup are facing one another.
Put the pencil, eraser up, through the bottom of the cup with four holes until it is touching the straw then push the pushpin through the straws and into the eraser, securing them in place.
Draw an X on the bottom of one of the cups with the marker.
The simple anemometer can be taken outside to a place where the wind is blowing. Watch for the cup with the X on the bottom and count how many times it spins around in 10 seconds. If it has two to four revolutions in 10 seconds, the wind speed is approximately 1 mph (2 kph). If there are five to seven revolutions in 10 seconds, the wind speed is approximately 2 mph (3 kph) and so on.
Though not technologically advanced, a simple DIY anemometer is similar to the first anemometers that were invented. It can give you a nice general idea of wind speed and you can use more sturdy materials if you desire, but the design outlined above is a great place to start.