Patent ID: 7015691

Claim:
A weak-magnetic field sensor using printed circuit board technology, comprising: a first magnetic core having first and second cores connected in parallel to each other; a first surface disposed above said first magnetic core; a second surface disposed below said first magnetic core; first and second exciting coils, each exciting coil including a first set of exciting patterns formed on said first surface, a second set of exciting patterns formed on said second surface and exciting interconnecting members interconnecting said first and second set of exciting patterns, said first and second exciting coils being formed of respective first and second exciting turns wound around the first and second cores with the first exciting turns being wound around only the first core and the second exciting turns being wound only around said second core, respectively, to supply alternating excitation current to the first magnetic core; and a first detecting coil alternately arranged between the first exciting coils, said first detecting coil including a first set of detection patterns formed on said first surface, a second set of detection patterns formed on said second surface and detection interconnecting members interconnecting said first and second set of exciting patterns to define detecting turns wound around both the first and second cores, in order to detect variation of magnetic fluxes generated in the first magnetic core; wherein the detecting turns are alternating with the first and second exciting turns; and wherein the first exciting coils are formed of metallic materials to be solenoidal for alternating current excitation and differential excitation and the first detecting coil is formed of a metallic material to be solenoidal for detecting the variation of the magnetic fluxes generated in the first magnetic core; wherein the first magnetic core is formed in a direction in which the magnetic fluxes are detected to reduce demagnetizing field components.