Magnetometer is a scientific instrument used to measure the magnetic field strength and direction. Magnetograph is a special magnetometer that continuously records data. The Earth’s magnetic field (the magnetosphere) varies from place to place, for various reasons such as inhomogeneity of rocks and the interaction between charged particles from the Sun and the magnetosphere. Magnetometers are a frequent component instrument on spacecraft that explore planets. Spacecraft magnetometers are magnetometers used aboard spacecraft and satellites, mostly for scientific investigations. Latest smartphones and PDA cell phones are coming with magnetometers and software applications to help users earth navigation. Some smartphones use magnetometers for touchless 3D interaction such as for recognition of hand gestures by wearing a magnetic strap on hand.

Magnetometer Applications

  • Magnetometers are used in ground-based electromagnetic geophysical surveys (such as magnetotellurics and magnetic surveys) to assist with detecting mineralization and corresponding geological structures.
  • Airborne geophysical surveys use magnetometers that can detect magnetic field variations caused by mineralization, using airplanes like the Shrike Commander.
  • Magnetometers are used to detect archaeological sites, shipwrecks and other buried or submerged objects, and in metal detectors to detect metal objects, such as guns in security screening.
  • Magnetic anomaly detectors detect submarines for military purposes.
  • Magnetometers are used in directional drilling for oil or gas to detect the azimuth of the drilling tools near the drill bit. They are most often paired up with accelerometers in drilling tools so that both the inclination and azimuth of the drill bit can be found.
  • Magnetometers can give an indication of possible auroral activity before one can see the light from the aurora. A grid of magnetometers around the world constantly measures the effect of the solar wind on the Earth’s magnetic field.

Types of Magnetometers

  • Rotating Coil Magnetometer – The magnetic field induces a sine wave in a rotating coil. The amplitude of the signal is proportional to the strength of the field, provided it is uniform, and to the sine of the angle between the rotation axis of the coil and the field lines.
  • Hall Effect Magnetometer – Solid-state Hall effect sensors produce a voltage proportional to the applied magnetic field and also sense polarity.
  • Proton Precession Magnetometer – Proton precession magnetometers, also known as proton magnetometers, measure the resonance frequency of protons in the magnetic field to be measured, due to nuclear magnetic resonance (NMR).
  • Magnetic Gradiometers – Magnetic gradiometers are pairs of magnetometers with their sensors separated by a fixed distance. The readings are subtracted in order to measure the difference between the sensed magnetic fields, which measures the field gradients caused by magnetic anomalies.
  • Fluxgate Magnetometer – fluxgate magnetometer consists of a small, magnetically susceptible, core wrapped by two coils of wire. Fluxgate magnetometers measure the direction and magnitude of magnetic fields.
  • Spin-Exchange Relaxation-Free (SERF) Atomic Magnetometers – SERF magnetometers only operate in small magnetic fields.
  • Caesium Vapor Magnetometers – The caesium magnetometer is typically used where a higher performance magnetometer than the proton magnetometer is needed in archaeology and geophysics.
  • SQUID Magnetometer – SQUIDs, or superconducting quantum interference devices, measure extremely small magnetic fields. They are very sensitive vector magnetometers.