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.  

6 responses to “Fluxgate Magnetometer Wrap-Up (For now)

  1. The post gave me some relevant information, I was searching for a magnetometer for suiting my new air ride and can use with a GPS for fixing camera on it, hope this one will work, Thanks.

  2. Glad it helped! Feel free to contact me at any time!

  3. Hi! I am very interested in building this project for a class but am having trouble deciding which components are needed for the amplifiers and the bandpass filter as I'm fairly new to building electronics

    • Hi Matt,

      It's a huge topic. For something like this most op-amps will work. I'd strongly consider something like the INA105 though, I'd probably use it myself now. Check books like "The Art of Electronics" on filters. Depending on what you're needing to do, I'd check out ready-built sensors like those from Adafruit and Sparkfun that can hook into an Arduino. If your goal is to measure the magnetic field, those are a lot easier to implement.

      • Thanks for the quick reply!
        I'll definitely take a look at that book. The most important part is building the instrument in this project rather than just needing a sensor to measure the magnetic field so I am going to try my best to build the circuits myself. Thank you very much for your help!

        • I'm glad you want to build the sensor, it's a fun exercise. I need to revisit mine and update it somewhat. Good luck and thanks for reading the blog 🙂 Stay tuned for updates sometime after the new year (2016)

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