Simple Gauss Meter (Magnetometer)

by Peter Balch

40921

Intro: Simple Gauss Meter (Magnetometer)

Magnets are complicated. You are taught about them at school and you think you understand them but they're way more complicated than that. How "strong" is a magnet? How big is the force between a magnet and a paper clip? Or between two magnets? Is repulsion as big as attraction? (No!) I've got a box full of magnets - what do I know about them? I was playing with a hall sensor and decided to make a simple Gauss meter.

This meter will take you about 15 minutes to make. Making a nice case for it will take a lot longer.

The meter has a range of +/- 1000 Gauss. For comparison, the Earth's magnetic field where I live is 0.5 Gauss.

STEP 1: Building It

The circuit is very simple. The 9V from the battery goes to the 7805 regulator input. The 5V output from the 7805 powers the A1301. The output from the A1301 goes though a resistor to the meter.

I printed a scale showing 1000-0-1000 gauss and glued it on to the meter. I labelled the "0mA" end of the scale "N" to mean that the sensor is near a North pole of a magnet. And I labelled the "FSD" end of the scale "S". That was with the curved face of the A1301 facing outwards towards the magnet. You could check how yours works with a compass.

People express magnetic fields in several different ways. Some useful numbers are:

  • 1 Gauss = 100 uTesla
  • 1 Gauss = 100,000 gamma
  • 1 Oersted = 1 Gauss in a vacuum
  • one ampere per metre = 4pi mOersted
  • Earth's magnetic field = 25uT to 65uT
  • Solar magnetic field = around 20nT
  • fridge magnet = 100G
  • Neodymium magnet = 1000G

Different kinds of sensors have different sensitivity. Of the ones you can build yourself, a Hall sensor can measure down to maybe 10,000nT, a Fluxgate sensor can measure maybe 1nT and a proton precession sensor can measure maybe 0.1nT. So a Fluxgate sensor is perhaps not quite sensitive enough for an archaeologist to do a geomagnetic survey.

STEP 2: Making a Case

It took far longer to design and 3D-print the case than to build the circuit. I quite enjoy CAD design work but printing, sanding and finishing things is much more annoying. Maybe I should buy a better quality printer.

The "probe" is the barrel of a ballpoint pen. The sensor is hot-glued into the end with the curved side outwards.

The STL files and source files are here. I don't imagine they'll be much use to you as they're specific to the meter I used.

Comments

AjarDesign 4 months ago

Great contraption! One of those projects I probably don't need, but can't wait to try!