A review of magnetic sensors

Eleven of the most common technologies used for magnetic field sensing are described and compared. These are the search coil, flux-gate, optically pumped, nuclear precession, SQUID, Hall-effect, magnetoresistive, magnetodiode, magnetotransistor, fiber optic, and magnetooptic technologies. The use of these sensors in relation to working with or around the Earth's magnetic field is addressed. Three classes of applications and a specific application from each are examined: low-sensitivity (noncontact switching), medium-sensitivity (magnetic anomaly detection and magnetic compassing), and high-sensitivity (brain-function mapping).