Patent ID: 9448262
Filing Date: 2016-09-20
CPC Classification: G01R

Claim Text:
1. A current sensor comprising a sensor element and a detector, the sensor element comprising: at least one core member, annularly formed with a magnetic material, and having characteristics such that, corresponding to an external magnetic field that changes due to influence of a signal to be detected that passes through a detection area surrounded by the annularity, a permeability μ decreases from an vertex where the external magnetic field is 0, and such that curvature of a curve, exhibited when a change in the permeability μ is plotted in “a coordinate system defined by the external magnetic field—the permeability μ”, becomes larger corresponding to absolute values of the external magnetic field; at least one exciting coil wound around the at one core member so as to excite the at least one core member; at least one detection coil wound around the at least one core member and used so as to detect the signal to be detected; and at least one cancel coil wound around the at least one core, and fed with a cancel signal so as to cancel out the change in the external magnetic field due to the influence of the signal to be detected, the sensor element being configured such that, while the at least one exciting coil is fed with an excitation signal, comprising a fundamental component, and when the signal to be detected flows, a signal, including a harmonic component, corresponding to the permeability μ of the at least one core member at that point, being superposed on the fundamental component, is outputted from the at least one detection coil, and the sensor element being further configured such that the change in the external magnetic field due to the influence of the cancel signal, fed to the at least one cancel coil, causes a change in the harmonic component superposed on the output signal from the at least one detection coil, and the detector comprising: a component extraction unit that extracts, from the output signal of the at least one detection coil, the harmonic component superposed on the fundamental component among signal components included in the output signal; a cancel control unit that controls feeding of the cancel signal to the at least one cancel coil; a level specification unit that specifies a signal level corresponding to the harmonic component, extracted by the component extraction unit, as a signal level of the signal to be detected at that point based on a corresponding relationship between the harmonic component, potentially included in the output signal, and the signal level of the signal to be detected when the harmonic component is generated; and an information output unit that outputs information externally, indicating the signal level specified by the level specification unit, wherein the cancel control unit performs feedback control of a signal level of the cancel signal so that the harmonic component, extracted by the component extraction unit, becomes small, and wherein the level specification unit specifies the signal level in such a manner that, once the feedback control by the cancel control unit is initiated and when it is determined that the harmonic component extracted by the component extraction unit, is smaller than a predetermined threshold, based on a corresponding relationship between the harmonic component canceled out according to the signal level of the cancel signal and the signal level of the signal to be detected when the harmonic component is generated, the level specification unit specifies the signal level corresponding to the signal level of the cancel signal that initially makes the harmonic component smaller than the threshold as the signal level of the signal to be detected at that point.