A magnetic field sensor based on fluxgate magnetometric principles includes a magnetic core having an elongated oblong configuration and accordingly defining a closed magnetic flux path. The core includes a rigid bobbin which defines the core's shape, and about which amorphous magnetic material is wrapped....http://www.google.com.au/patents/US6278272?utm_source=gb-gplus-sharePatent US6278272 - Integrating fluxgate magnetometer
