Fluxgate Magnetometer Wrap-Up (For now)

Per lots of emails and requests I’m going to post what I have from the design of the fluxgate magnetometer mentioned in several previous posts (like this one).  The schematic attached at the bottom is a rough draft, but should provide some guidelines for designing and building a version of this instrument.  I’ve also attached links to several PDFs that I found very helpful when building this demo.

It should be noted that this design doesn’t have a plain readout with XXXXXX nT magnetic field, but displays a waveform on the oscilloscope.  Could one be made? Absolutely! Since this was more of a demonstration of the underlying physics I didn’t bother, but it would be a good weekend project.

First off let me list a few things I would build differently were I building this again:

-       Use shielded lead wires to reduce crosstalk to the coil.

-       Use a simple Analog-to-Digital converter so this output is projected from a laptop to the classroom screen (much easier than gathering students around an oscilloscope).  I think an Arduino might do the trick.  Raspberry Pi would be a good choice too.

-       Add gain adjustment knobs to the control panel.

-       I would again use the Velleman kit for the signal generator instead of re-designing the wheel.

When using this in the classroom I laid it alongside commercial magnetometers on the table.  We discussed the physical principles behind the instrument, and then students would use the demo fluxgate to generate an output wave.  Afterwards we used the commercial magnetometers to do simple tasks like finding conduits and keys. 

It would also be nice to have a first-principles proton-precession magnetometer.  There is a book “Signals from the Subatomic World: How to Build a Proton PrecessionMagnetometer” that describes one such instrument, but significant improvements in the instrument could be made with modern programming languages and ADC devices. 

I still welcome questions on the fluxgate and will probably update the instrument next time I teach an Intro Geophysics course (undetermined).  Thank you for all the interest and if you build one, please send your results and we’ll put them up here for all to benefit.