Magnetometer
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A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of the magnetic B-field at a par
Helium vector magnetometer (HVM) of the Pioneer 10 and 11 spacecraft
A marine technician preparing a towed magnetometer for deployment from a ship
The Magnetometer experiment for the Juno orbiter for Juno can be seen here on the end of a boom. The spacecraft uses two fluxgate magnetometers. (See also Magnetometer (Juno))
The compass is a simple type of magnetometer.
Mu-metal
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Mu-metal, or μ-metal, is a soft nickel–iron ferromagnetic alloy with very high permeability, which is used for shielding sensitive electronic equipment against static or low-frequency magnetic fields.
Assortment of mu-metal shapes used in electronics, 1951
Five-layer mu-metal box. Each layer is about 5 mm thick. It reduces the effect of the Earth's magnetic field inside by a factor of 1500.
Mu-metal shields for cathode-ray tubes (CRTs) used in oscilloscopes, from a 1945 electronics magazine