Differentially DC biased type magnetic field sensor of high sensitivity

The detection principle of a novel magnetic field sensor called the differentially-DC-biased magnetic field sensor which uses a magnetic core is described. The detectable lower limit is extended up to the order of 10^-13/√Hz by virtue of the detection principle used, which is analogous to the equilibrium condition of ordinary bridge circuits. By using two cores, a kind of bridge circuit is constituted. The field to be detected breaks the equilibrium condition, which leads to the variation of incremental permeability. The means adapted to detect the variation with high sensitivity are described