GB1388875A - Magnetic field sensing apparatus - Google Patents

Abstract

1388875 Magnetometers MISHIMA KOSAN CO Ltd 1 May 1972 [30 April 1971] 20224/72 Heading G1N In a magnetometer comprising a non-linear inductance sensing element connected to a capacitor 8 to form a resonance circuit, the external magnetic field being measured Hex is nulled by a current negatively fed back to the resonance circuit, the magnitude and polarity of the external magnetic field being indicated from the negative feedback current. Construction of sensing element. The non- linear inductance comprises a core conductor of copper wire surrounded by magnetic material 5 and a coil 7. The magnetic substance may be Permalloy deposited directly on the wire or may be a magnetic thin film wound or laminated on the wire. Glass insulating material (6) may be present between the wire and the magnetic material, and the magnetic material may be isotropic or anisotropic. The coil 7 may be wound directly on the core or on a glass tube surrounding the core. The magnetic circuit may be open or closed. The coil 7 may include turns in opposite directions Figs.1b and 1c, (not shown). Circuit details. Alternating current from oscillator 21 is fed to the core conductor of the sensing element. The resulting resonance signal in the resonance circuit is detected at 23 and integrated at 25 and negatively fed back via an impedance 11. The ambient magnetic field (Hu) may be cancelled by current from source 20.