Patent ID: 11656299

Abstract:
A near magnetic field variation detection method comprises following steps of: measuring magnetic field by a first magnetic field sensor and a second magnetic field sensor respectively; and calculating a magnetic field measurement difference, wherein the magnetic field measurement difference is (1) a magnitude of a difference of a first-magnetic-field-measurement measured by the first magnetic field sensor and a second-magnetic-field-measurement measured by the second magnetic field sensor, or (2) a magnitude of a difference of a first-magnetic-field-measurement-component measured by the first magnetic field sensor along a characteristic direction and a second-magnetic-field-measurement-component measured by the second magnetic field sensor along the characteristic direction; wherein a near magnetic field variation is occurred when (a) the magnetic field measurement difference is continuously greater than a characteristic-threshold within a characteristic-time-period, or (b) an average value of the magnetic field measurement difference is greater than a characteristic-average-threshold within a characteristic-average-time-period.