Precise vectorial magnetic sensors

Precise magnetic sensors are required in many fields: besides the traditional geophysical magnetorneters they serve for navigation, position tracking, military and security. First a short review of basic practical rules and sensor parameters is given. Next the most important semiconductor magnetic sensors (Hall sensors and semiconductor magnetoresistors) are discussed. Following sections describe the most important precise magnetic sensors: ferromagnetic magnetoresistors (AMR, GMR and SDT). and fluxgate sensors. Other types of magnetic sensors (SQUIDS, Magnetooptic sensors, GMI and Magnetostrictive sensors) are described briefly. Section 6 is devoted to current sensors based on magnetic principles: Instrument current transformers, Rogowski coil (di/dt sensor), Fluxgate DC current sensors, Hall current sensors, and Magnetoresistive current sensor. Other applications of magnetic sensors are reviewed in Section 7. They include position sensors, Compass, Security and military applications, Geophysics and Space research, Biomagnetism and medical applications, and Non-destructive testing. Final section compares the described sensor types. Fluxgates are the most precise vectorial sensors, followed by AMRs, which become great competitors of Hall sensors. Until now, GMR and SDT sensors are rather nonlinear. GMI sensors are recently commercially available, but their present accuracy is not competitive. Common problem of magnetic sensors containing ferromagnetic material is perming (remanence). This was solved only with fluxgates and flipped AMRs.