Table of Contents:
1) Introduction:
2) Background:
3) Objective:
4) Materials:
5) Procedures:
6) Errors: 7) Links: 8) Data: 9)Return to the research page

I) Introduction:

The anemometer is a probe(like the accelerometer and the motion detector) that measures the velocity of wind. Wind blown through the propeller causes the fan to rotate. By recording how many times the propeller passes a specific point inside the anemometer wind velocity is recorded in meters per second.

Wind is usually the term that is given to the natural horizontal motion of the atmosphere. The vertical motion is generally termed current. Winds are produced by differences in atmospheric pressure, which are primarily attributable to differences in temperature. Variations in the distribution of pressure and temperature are caused largely by unequal distribution of heat from the sun, together with other factors such as the thermal properties of land and ocean surfaces. When the heating of regions become unequal, the warmer air tends to rise and flow over the cooler air. Winds initiated in this manner are usually greatly modified by the earth’s rotation.

After searching the internet and learning from scientists like Marty Jones and numerous internet sources, I realized that there was a drastic range on the types of anemometers that can be purchased in the market. I couldn’t believe how simplified some of the models were and how extreme others were. For an example the simplest one that I found was an anemometer that was created from just a piece of string, a protractor, and a pin pong ball. You would first attach the string to the middle of the protractor, and on the other end of the string attach the ball. You would position the sting to the protractor so that it started out on zero degrees, and as the wind blows on it, the angle that the string makes with the protractor is the velocity of the wind. A more complex model that you could either purchase or build would be one of the electronic ones where they not only measure the exact wind velocity, but temperature, direction, revolutions, and much much more. The more complex models have a devised ticker built into them that would measure the number of revolutions that the model makes. I took Mr. Murray’s advice and devised a cupped anemometer with a ticker. My hypothesis was that if the car was going at a faster speed, then the more revolutions the model would make, which would indicate a higher wind velocity.

II) Background:

Through the ages weather forecasting were based on local observations made by the human senses. Accurate measurements of temperature and atmospheric pressure were not available until after the thermometer and the barometer were perfected in the 17^th century. Comprehensive weather forecasting did not become practical until the telegraph was invented in the 19^th century.

The first systematic weather observation in the United States dates back to 1738. In 1816 the German scientist Heinrich Brandes drew one of the world’s first known weather maps. Then in 1849 a man named Joseph Henry established a telegraphic network of observation for the preparation of daily weather maps.

One of the most common methods of weather forecasting today is synoptic forecasting. It is based on a summary of the total weather picture at a given time. The development and movement of weather systems is shown on a sequence of charts or maps. These weather systems then are projected into the future. The weather observations used for synoptic charts are made at thousands of weather stations around the world four times a day: at midnight, 6AM, noon, and 6PM.

Another method, statistical forecasting, employs mathematical equations based on examinations of the past behavior of the atmosphere. For forecasts of up to five days, numerical methods are most often used; for somewhat longer periods, statistical methods are more accurate.

We’ve revolutionized so much that computer -drawn maps now predict wind, temperature, and humidity patterns for many atmospheric levels. Statistical methods are then used to map probable max. and min temperatures and precipitation.

III) Objective:

When I first set out to do this physics project I thought that I would do my project on wind. I was interested in how wind actually worked and where it originated. I was always fascinated by wind and wanted to devise a model that would be capable of measuring the velocity of wind by comparing the number of revolutions the model made relative to the various speeds that the car traveled. To be truthful, I wasn’t all that familiar with the properties of wind and how it worked. At first I had a hard time thinking up of a model that would be able to record the velocity until Mr. Murray gave me the idea of using a cupped anemometer.

IV) Materials:

• Thin cardboard sheets
• Dowel stock
• 2 glass beads
• one long strand of yarn
• hot glue gun
• several nails
• hammer
• drill
• 2 thin wooden dowel sticks, 18" x ½"
• Pencil
• one index card
• stapler
• bolts (optional)
• compass

• First, I went to Home Depot and bought one thin wooden dowel stick and sawed it in half to make two sticks (18" x1/2"). In addition I also bought a slightly larger (thicker) dowel stick to use as the dowel stock.
• After sawing the two sticks apart I figured that I had to connect the two ticks together so that it would rotate (together). With my intellectual ability with tools I thought that all I had to do was join the two sticks as follows: nail, bead, cross sticks, bead, and dowel stick. The beads will act as a bearing so the wind will turn the anemometer freely.
• Boy was I wrong. =) Once I nailed the nail into the wood I found out soon enough that something was wrong. =) I realized that the dowel sticks were pretty thing to start off with and in addition the wood was pretty dense. With every hammering the wood automatically split apart. It was during this time that I started to panic because I knew of no other ways of connecting the two dowels. I found out how stupid that I was soon enough.
• I never realized how such a simple model could be so complicated. I ended up calling my Dad and requested that he help me put my model together. He ended up giving me this big lecture about how to nail and deal with tools…and so I found out how stupid I was soon enough. =)
• He told me that my problem was that I wasn’t suppose to nail the nail straight down to start off with. In doing so I would just crack the wood. In addition, the two dowels would be stiff and that would totally undermine my whole project considering that they are suppose to spin in order for me to count the number of revolutions!!! Duh!!!!!=)
• By drilling into the wood you would take some of that stuff out and that means that there would be space for the nail to go in. Also it creates more space which would mean less friction. Thus the dowels will be able to spin freely.
• After the dowels were attached, I cut two circles about 4" in diameter ( measure with compass) from the cardboard. Then I ended up cutting that in half so that I would end up with 4 half circles of equal size. I joined (or overlapped) the straight edges together by stapling them and then hot gluing down the sides. I then nailed the cups onto the ends of the dowel sticks. To make sure that they were all going in the same direction, I added a little bit of the hot glue to it to hold it in place or to prevent it from spinning.
• Them to make sure that the two dowels will spin together and not run into each other I used the yarn to wrap up the middle section and hot glued the yarn down too.
• Afterwards, I decided that I should add a ticker on to this model so that I would be able to record the number of revolutions. I drilled a little whole off to the side and added a pencil there. Attached to the pencil would be a piece of cardboard paper that the dowels would hit every time that it would hit.
• In order to test this model I decided that it would be necessary to find a straight road to test it on. This is necessary because you have to measure the wind that is coming from one direction only. If it were on a curvy road then the gusts of wind would change as the road changes and thus your data would be inaccurate. I also decided that since wind and rain in Oregon are so inconsistent that I would have to do two trials (one going forward and the other going the other directions) and average the two in order to get the true wind velocity.
• I was the one behind the wheel and my brother (which I dragged into this) held the anemometer out the window and counted the number of revolutions. I wanted to see the difference of wind speed in comparison with the speed of the car so I decided to start at a constant 5mph and notch it up 5 miles each time. So I was trying to drive and time and not hit any pedestrians or cars while my brother held the model out the window and recorded the revolutions at the same time.

I eventually found out that there were numerous errors in my data. For one thing, wind in itself is not constant which makes it very difficult to measure. I first started out driving in a parking lot and turned a lot which would have contributed to the many errors. Scientist Marty Jones suggested that I attach my anemometer to the roof of my car or something so that it won’t be shifting around as it would when somebody is holding it, which would reduce the chances of errors. I personally have a very difficult time trying to drive at the designated constant speed. I’m sure that I wasn’t going at the required speed the whole entire time. The biggest factor that effected my project was the fact that I live in Oregon and thanks to Oregon rain I had to cut my project short. Internet sources emphasized aluminum sheets to make the cups, but because they did not specify on how thick the aluminum had to be, I decided to use cardboard. Cardboard tends to be heavier and also they totally fall apart when introduced to rain. Because of the extra weight that was introduced by the rain, my anemometer did not turn as fast as I predicted at higher speeds. For some trials we had to do it over and over because at a certain point it just didn’t turn at all. I think it is because of the extra weight caused by the rain and because of the effect that rain has on wood with metal. Obviously it created my friction once the wood was wet because I noticed that the model couldn’t turn as easily and became totally inefficient. (The Cups ended up getting ruined and fell off) =(
 
 

* I converted mph to m/sec, then I stuck that into the speed = d/t formula and solved for the distance. Distance was not constant, time was.
 
 

VII) Links:

1) Anemometers: http://www.time-weather.com/time-weather/anemometers.html

2) Aeronautics: Making a Wind Anemometer: http://www.allstar.fiu.edu/aero/Experiment10.htm

3) Anemometer 840003: http://204.127.238.82/s840003i.htm

4) Weather Anemometer: http://208.161.180.245/ISk12mac/gsh/harness/_LIB/_MODELS/HOLLISTR/ANEMOMET.HTM

5) Anemometer: http://www.thiesclima.com/wind_e.htm

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