Accession Number : ADD012423

Title :   Fiber-Optic Magnetic Gradiometer with Variable Magnetic Biasing Fields.

Descriptive Note : Patent,

Corporate Author : DEPARTMENT OF THE NAVY WASHINGTON DC

Personal Author(s) : Koo,Kee P ; Sigel,George H , Jr

Report Date : 27 May 1986

Pagination or Media Count : 10

Abstract : This patent discloses a fiber optic magnetic gradiometer for measuring both ac and dc magnetic field gradient. The gradiometer utilizes an optical interferometer with magnetostrictive magnetic field sensing elements in each of the interferometer arms. Ac and dc magnetic field biasing is achieved by disposing each of the magnetic field sensing elements within its own magnetic field coil and utilizing a variable dc current source for applying dc current to each magnetic coil. An ac current source at frequency w sub o connected across the circuits of the dc current sources is used in conjuction with a variable attenuator to control the ac bias to the respective magnetic coils. The detected output from the interferometer is processed either by bandpass filters or a spectrum analyzer to obtain the signal component w sub o, which is proportional to the external dc gradient magnetifc field, and at w sub o + w sub s, (where w sub s is external ac magnetic field frequency), which is proportional to the external ac magnetic field gradient.

Descriptors :   *PATENTS, *GRADIOMETERS, *FIBER OPTICS, OPTICAL CIRCUITS, MAGNETOSTRICTIVE ELEMENTS, OPTICAL INTERFEROMETERS, SPECTRUM ANALYZERS, BANDPASS FILTERS, BIAS

Subject Categories : Magnetic & Electric Fld Detection & Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE