How to Build an Anemometer

Meteorologists use anemometers to measure wind speed. In addition to having the fun of making their own anemometer, amateur meteorologists can use readings from their anemometers to keep track of patterns in wind speed as high and low pressure areas move over their location and to gauge the intensity of pressure gradients, an indicator of approaching weather. But mostly, it's just fun to build something that you can use to measure something that we always feel but never see.

Things You'll Need

• 4 paper cups with sturdy straws or school rulers
• (or 4 coffee scoops)
• Pins, nails or paper clips
• 1/4-inch Plywood scraps
• Sewing thimble
• Cyanoacrylate adhesive (instant bond glue) or hot craft glue

Instructions

1. Build wind scoops for your anemometer. Use sturdy paper (foam cups would crumble) cups and drill holes straight through both sides about one quarter to one third of the distance from the rim to the base. Insert a straw through each cup to make the scoop arm. Secure the cups with bits of glue so they can't slip and turn up when you mount them. As an alternative scoop-arm assembly, you could use school rulers (the simple flat kind) and staple the cups to one end. Or bypass all of this assembly by using plastic coffee scoops (the kind with the handle) for your wind scoops.

2. 

   Assemble the armature. Cut two small (one- to two-inch) squares of 1/4-inch plywood and drill a hole the diameter of a thimble in the center of both for a center block. Glue the thimble to the bottom piece and glue the ends of the straw "arms" into the thimble at 90 degree angles to the center. Lay in each straw at the halfway point on each side of the center block. Lay the second square on top of the first and glue down to the straws and thimble, taking care not to bend the straws. If you choose to use rulers, don't bother drilling the top piece, glue the rulers in the same pattern, standing them on end and attach the top piece with glue, adding a few thumbtacks or pins through the wood into the rulers from the top and bottom for stability. Plastic coffee scoops can just be glued on end. Make sure that the cups all follow each other. If they point in opposite directions, your armature won't turn.

3. Build a base for your armature. This can be as simple as a stand with a nail in the top for the thimble to sit on. It could even be a sharpened pencil, held up in the wind with the armature perched on top of it.

4. Calibrate your anemometer. There are a number of suggestions for doing this, including holding it out the window of a moving car while counting revolutions. The simplest way to get an approximate wind speed is to count revolutions per minute. Paint one of the wind scoops of your anemometer in a contrasting color (such as red or yellow) so that you can count each time it circles the anemometer. You can keep track of wind speed this way or use a formula to determine approximately how many miles an hour the wind is gusting.

Tips & Warnings

• To determine wind speed in miles per hour (mph), use this formula: calculate the circumference of your anemometer by multiplying the diameter (or distance between opposing scoops) in feet times pi (or 3.14). Multiply this number times the number of revolutions per minute to get the number of feet per minute (fpm) one scoop travels. By multiplying rpm by 60 (minutes per hour) and dividing this number by 5280 (feet per mile), you will get an approximate wind speed in miles per hour.

• There are dozens of anemometer projects for everyone from elementary school students to the really serious enthusiast on the web. A few are listed below.

• This anemometer is not scientifically accurate and should not be confused with instruments specifically built and calibrated to measure wind speeds.

Resources

• Simple pencil-paper cup anemometer with recording sheet
• Science project-grade anemometer
• Science unit with construction directions
• Simple construction with conversion formula