Precise Magnetic Sensors for Navigation and Prospection

Abstract

Navigation, position tracking, search for unexploded ammunition, and geophysical prospection of magnetic or conducting ore are key applications where very small magnetic field signatures and field increments should be detected in the presence of the Earth's magnetic field, typically 50,000 nT. The industry calls for a new generation of portable vectorial magnetic sensors with a precision better than 0.1 nT. This error requirement includes not only sensor noise but also linearity, cross-field error, hysteresis, and perming and also temperature drift of the sensitivity and mainly the offset drift. For application on moving platform, the sensors should also have fast response. We will show that these requirements can be met only by fluxgate sensors. On the other hand, mass market requires cheap, low-power, and small magnetic sensors for portable gadgets; the typical application is compass in mobile phone, with precision of several degrees, corresponding to a 100-nT precision. For these applications, anisotropic magnetoresistance (AMR) sensor is dominant, while integrated fluxgates may penetrate the high-end market.