Magnetometer, << `mag` nuh TOM uh tuhr, >> is a device that measures magnetic fields. A magnetic field is the influence that a magnet or an electric current creates in the region around it. Some magnetometers measure only the strength of a field. Others, called vector magnetometers, also measure the field’s direction.
The simplest magnetometer consists of a coil of wire. This device operates by means of electromagnetic induction: If a magnetic field is present, turning the coil 180 degrees will cause electric charge to flow through the coil. The amount of charge that flows will depend on the field strength.
The most sensitive magnetometers are called superconducting quantum interference devices (SQUID’s). These use superconductors, materials that carry electric current without resistance at very low temperatures. A SQUID magnetometer can even detect weak magnetic fields produced by the human brain.
