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Make Your Own Barometer

simple-barometer image
A Simple Barometer

You probably have a thermometer somewhere in your house, but how about a barometer? You can predict the type of weather that’s coming by watching a barometer. This instrument measures the amount of air pressure. Low pressure systems usually mean rainy weather, while high pressure systems mean mild, cool weather. You don’t need to be a professional weather reporter to understand weather patterns. Below, you’ll learn how to make a simple weather barometer.

A Simple Barometer Image - Science for Kids Make Your Own Barometer
A Simple Barometer

Materials Needed for Your Homemade Barometer:

  1. A glass jar (best) or a large metal tin container (like an empty and cleaned large can of baked beans) with straight sides and a wide top/mouth
  2. A balloon (do not use one you already blew up before)
  3. A few rubber bands
  4. A tube of silicon glue
  5. Adhesive tape
  6. 2 plastic drinking straws
  7. Small bit of thick paper (Bristol paper or cardboard paper), best use a nice red or other strong color
  8. A ruler
  9. A pair of Scissors

Directions on How to Make Your Own Barometer:

1)  Set the glass jar on a straight, firm surface.

2)  Cut the balloon so that you have a nice round part left, without the long end.

3)  Stretch the balloon so it fits over the mouth of the jar nice and tight – the tighter the better. We do not want a loose, saggy cover. Jar must be sealed well.

4)  Use the rubber bands to keep the balloon firmly in place over the mouth of the jar and to make sure the jar is sealed well, so no air comes in or leaks out.

5) Cut out a shape of a small arrow head from the thick piece of Bristol paper (or cardboard paper). It needs to fit snugly into the end of the straw, so make it neither too large nor to small. Make sure you have a pointy triangular tip to your arrow. Insert the arrow head into one end of the straw. If it is a bit wobbly and not staying firmly in place, try making another arrow head that’s a bit wider. If it’s too large you can trim the base till it fits well in the straw tip.

6)  A longer straw makes the home-made Barometer reading more accurate. Insert the second drinking straw into the empty end of the straw (the one with the arrow head in it). Insert it by gently squeezing the tip of the straw and then insert it just a little bit, so they become a long, yet stable long straw.

7)  Drip a bit of Silicon glue onto the balloon jar covering, in the very middle. Place the empty end of the long plastic drinking straw on the glue. Gently secure it in place with light pressure and then tape it down for some hours till glue dries and holds the straw in place. (If you use a very fast drying art glue, then you need not use the sticky take to hold it in place till glue dries).

Once your home-made barometer is ready, it should look similar to the image below.

Image of a homemade Barometer
Image of a homemade Barometer

Keep your barometer indoors. Place it near a wall. Use some adhesive tape to tape the ruler to the wall. Arrange the arrowhead to be vertical so it correctly points to ruler markings. Alternative to a ruler is a piece of paper with markings on it.

Watch your straw arrowhead over several days and record what you see in a weather journal. Do a few readings each day at same time during the day, so you can compare changes more accurately.

Why Will Your Homemade Weather Forecasting Barometer Work?

At the time you sealed off the glass jar, you captured air inside it. The air pressure inside your jar was exactly the same as the air pressure outside of the jar. However, as the weather changes, so changes the air pressure in the atmosphere (the outside air).

Since your jar is nicely sealed, the air pressure inside it does not change. However, the air pressure outside changes with the weather. So this causes pressure on the balloon cover to increase or decrease.

Make your own Barometer - why it works!
Make your own Barometer – why it works!

Sunny, clear and warm weather raises in the air pressure around you. This means that outside air is going to press on the balloon cover, since it is stronger than the air inside the jar. And when the air presses upon the balloon cover, it makes it sort of cave in a bit, almost like the air in the jar is sucking in its breath… Because we have the straw on the balloon, it will sink down where it is glued to the balloon, therefore the other tip with the arrowhead shall rise!

As a storm approaches your location, the mass of air around you decreases, causing the air pressure to drop (decrease). This will cause the pressure inside the jug to be higher and your balloon jug cover will bulge out. When this occurs, the end of the straw glued to the balloon goes up, while the end with the arrowhead will go down!

Barometer Pressure Reading Drawing Image
High air pressure makes the water go up. Low air pressure causes the water to go down, and means a storm is moving in.

What Else Influences Barometric Air Pressure Changes?

Decreasing atmospheric pressure predicts stormy weather and the air pressure changes are usually associated with storms. However, the air pressure you measure gets influenced by a few other things….

There are four daily pressure fluctuations in the atmosphere. These air changes are due to the sun heating the atmosphere. This daily change depends also upon the latitude, current season of the year, and the altitude you live in.

The air pressure changes are greatest at the equator. The barometric air pressure decreases toward the north and south poles, where it becomes zero. Also, the higher the altitude, the greater the daily change in the air pressure will be.

Make Your Own Barometer Video:

Watch this neat video – it has tips on how make a do-it-yourself barometer so you can become a weather forecaster!


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