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make your own magnetometer


Outdoors, we can see the light and feel the heat of the Sun. We can also feel the movement of the Earth’s atmosphere - the wind. But we can't see or feel the Earth's magnetic field so how do we know it's there?


We use a magnetometer


Magnetometers have been placed all around the world to record the Earth's magnetic field. These records allow us to build up a complete picture of how the magnetic field changes from one place to another. We can even watch magnetic waves as they wiggle (propogate) along the magnetic field.

One important collection of magnetometers is called SAMNET, a network of thirteen magnetometers run by scientists from the UK, Finland, Russia, the Faroe Islands, Sweden and Iceland.


This is a picture of the SAMNET logo. Can you see from the design what the letters ‘SAMNET’ stand for)

Samnet Logo


In my work I've used the SAMNET magnetometers to look at the waves that occur during geomagnetic storms. Because of the effect of the fast solar wind, I've seen some really big waves in the Earth's magnetic field. So I reckon it's pretty important we carry on looking out for big waves so we can tell people when to look out for the killer electrons!


Surprisingly, it's easy to make your own magnetometer from a plastic bottle and a few other bits and bobs. Take a look at these instructions from York University.


York University’s 'Pop Bottle Magnetometer'

The 'Pop Bottle Magnetometer'- instructions:

The 'Pop Bottle Magnetometer' is a very simple piece of equipment. It measures changes of the magnetic field at the Earth's surface, which occur due to Geomagnetic storms or other space weather. A 'pop bottle' magnetometer works just as well using a glass jar.


- a clear (and clean) plastic 2-litre pop bottle with its label removed and a plastic lid.
- thread.
- a bar magnet shorter than the width of the bottle.
- a small craft mirror, mirrored sequin or piece of mirror-card.
- a piece of card.
- sand or rice to stop the bottle falling over.
- blu-tac.
- a drinking straw or copper wire.
- sticky tape, scissors and glue




Carefully cut around the pop bottle to remove the top 1/3.
Fill approximately the bottom 1/3 of the bottle with sand or rice. You need to make something to suspend the magnet by. This can be done in one of two ways,
EITHER using the drinking straw OR using the copper wire


Drinking straw
Cut the straw slightly shorter than the magnet and stick it to the magnet using glue or sticky tape.
Cut a 50cm length of thread and thread this through the straw.
Make a triangular loop of this thread, keeping the long piece of thread attached to this triangle.


Copper wire
Cut a 20cm length of fairly strong copper wire.
Wrap the ends of the copper wire around the ends of the magnet and
pull the wire in the
middle to form a triangle.
Cut a 30cm length of thread and attach this to the point of the triangle.


Cut a rectangular piece of card. It must be able to move freely within the bottle when hanging vertically. Use glue to stick the magnet to the middle of the top edge of this.
Stick the mirror to the middle of the other side of the magnet. Make sure this is in line with the thread from which the magnet is hanging. It is important to make sure that the magnet hangs horizontally. If the magnet isn't quite horizontal stick a small piece of blu-tac to the cardboard to rebalance it.

Make a small hole in the centre of the bottle top and screw the top back on.
Feed the thread through the hole and adjust the length of the thread so that it does not scrape on the sand. Also, the mirror should be at least 2cm below the cut edge of the bottle. Secure the thread to the top of the bottle to stop it slipping. Use sticky tape or glue, or tie the thread to a matchstick lying across the hole. Tape the top of the bottle to the bottom.


Set up your magnetometer in a place where it will not be disturbed by any vibrations. Arrange to be able to shine a light onto the mirror using a light source that is firmly fixed in place or whose position can be reliably repeated. By monitoring the position of the reflected light, you will be able to detect any rotation of the bar magnetic. Since the bar magnet is responding to changes in the Earth’s magnetic field, you can see any effect magnetic storms are having.


Now you have a magnetometer ready to use.




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