Abstract
This paper presents a new magnetic field sensor of core type. The resolving power arrives at the order of 10-13T/√Hz at the room temperature. The sensor is composed of two bar type cores of which the B-H loop is desirable to have a high rectangularity ratio.
The detection principle is analogous to the operation on a kind of equilibrium condition in ordinary bridge circuit. Each core is previously DC-biased in the opposite direction regarding the unknown magnetic field to be detected. A high frequency excitation field is superimposed onto each of DC field in anti-phase as an auxiliary signal and resultant search coil voltage induced by the auxiliary signal is null when the unknown field is zero. When the field is impressed to each core, the equilibrium condition is broken out and the voltage appears in proportion to it. Thus, we can detect the unknown field. For reduction of the noise in electronic circuit itself, some numbers of high frequency amplifier of the same characteristics are connected in parallel and a tuning amplifier is added to the output side of these amplifiers.
By adopting the above approach, such the maximum possible resolving power can be achieved.
