PROBLEM TO BE SOLVED: To solve the problem of a resistance value shift of a MR sensor according to a secular change.;SOLUTION: An output of the MR sensor is standardized at the time of magnetic field measurement based on the sensor output as a standard when the MR sensor is under specific condition. As an embodiment, a magnetic field is generated by passing a current in a magnetization coil 5, and this magnetic field is applied to the MR sensors 1, 2. Thereby, the MR sensors 1, 2 are set on a selected specific condition, wherein the MR sensor 2 is enclosed by a magnetic shield structure 3 which cuts off the magnetic field except the magnetic field from the magnetization coil 5. After interrupting the current to the magnetization coil 5, an unknown magnetic field is estimated by obtaining the difference between the output voltage of the MR sensor 1 under the unknown magnetic field originating from an external source and the output voltage of the MR sensor 2 which is not influenced by the unknown magnetic field.;COPYRIGHT: (C)2011,JPO&INPIT
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