This project uses a tape wound core of amorphous metal ribbon driven alternately into saturation.  The magnetic field of the Earth causes a bias so the magnetic core saturates slightly earlier in one polarity vs. the other.  A closed loop feedback system applies a separate magnetic field through another coil to cancel the effect of the ambient field, driving the error to zero.  The amplitude of the feedback signal is then used as a measurement of the Earth field along one axis. The fluxgate sensor is directional.  Using three fluxgates, the magnitude and direction of the Earth's field can be calculated with a high resolution.

For initial experiments, a single channel PCB and sensor were built with the plan to duplicate them for the other two axes.  Low noise analog circuitry and closed-loop temperature control are used to minimize the effects of drift.  A precision 24-bit ADC is used to read the analog output.

The goal is to fuse the output of this vector magnetometer, which has less absolute accuracy, with the output of a scalar magnetometer (the proton precession magnetometer) which has better absolute accuracy but no ability to sense direction.  This combination should provide a more accurate result overall.  This is currently a work in progress.