Magnetometers

Magnetometers are scientific instruments that measure the strength and/or direction of a magnetic field. Magnetism describes how, on a microscopic level, materials respond to an applied magnetic field. These magnetic fields surround magnetic materials and are detected by the force they exert on other magnetic materials and moving electric charges. Types of magnetism include ferromagnetism, ferrimagnetism, antiferromagnetism, paramagnetism, and diamagnetism. Typically, magnetometers measure a magnetic field or flux density in metric units of gauss (G) or the international system (IS) unit of a tesla (T).

There are two basic types of magnetometers: scalar and vector. Scalar magnetometers are used to measure the total strength of a magnetic field. Planar magnetometers are used to measure a component of a magnetic field in a particular direction. Both types of scientific instruments use many different technologies. Search coil magnetometers, magnetometer arrays, magnetometer networks, and magnetic anomaly detectors are also available.

Scalar magnetometers may be divided into rotating coil, hall effect, and proton precession devices. Rotating coil magnetometers induce a sign wave in an electromagnetic coil. Hall effect magnetometers use sensors that produce a voltage that is proportional to magnetic field. These devices also sense polarity. Finally, proton precession magnetometers or proton magnetometers use nuclear magnetic resonance (NMR) to measure the resonance frequency of protons in the magnetic field.

Planar magnetometers use orthogonal vector technology to determine magnetic field strength as well as inclination and declination. Device categories include flux gates (fluxgates, fluxgate magnetometers), superconducting quantum interference devices (SQUIDs), and atomic spin exchange relaxation-free (SERF) magnetometers. Flux gates consist of a small, magnetically-susceptible core with two coils of wire. They may be arranged in a gradiometer configuration. SQUID devices are designed to measure very small magnetic fields. Atomic SERF magnetometers contain potassium, cesium or rubidium vapor. They are operationally similar to cesium magnetometers.

Because magnetism varies by location and with differences in the Earth’s magnetic field or magnetosphere, magnetometers are used to provide orientation, navigation, and leveling information. For example, combination compasses and magnetometers are used on satellites and aboard airplanes that map the local structure of the Earth's magnetic field. Navies use compasses and magnetometers to detect submarines under water. Surveyors can use these magnetometers to locate boundary stakes buried in the ground or hidden by vegetation.

• Magneto-Inductive Sensors
  Magneto-inductive sensors incorporate a coil surrounding a ferromagnetic core whose permeability changes within the earth's magnetic field. The coil serves as the inductive element in an oscillator,...
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Part Numbers for Magnetometers