Magneto-impedance element and magneto-impedance senor including detection coil.

Abstract

A magneto-impedance element includes a magnetic sensitive member having a form of a line, whose electromagnetic characteristics vary depending on an external magnetic field, a pulse current flowing from one to another end portion thereof in an axial direction. A conductive layer is arranged on an insulating layer provided on an outer surface of the magnetic sensitive member. A connection portion, electrically connecting the magnetic sensitive member and the conductive layer, is arranged on the other end portion in the axial direction of the magnetic sensitive member. A detection coil, outputting an induced voltage corresponding to an intensity of an external magnetic field acting on the magnetic sensitive member when the pulse current flows in the magnetic sensitive member, is wounded around the conductive layer. A direction of the pulse currents flowing in the magnetic sensitive member and in the conductive layer are opposite each other.

Description

TECHNICAL FIELD[0001]The present invention relates to a magneto-impedance element and a magneto impedance sensor having good linearity.BACKGROUND ART[0002]As a conventional magnetic sensor (hereinafter referred to as an MI sensor) using a magneto-impedance element (hereinafter referred to as an MI element), for example, a magnetic sensor having a detection coil wound around an amorphous wire is known. Patent Document 1 discloses a MI sensor which causes a pulse current to pass through an amorphous wire and measures a first pulse of an induced voltage output from a detection coil to make it possible to sensitively detect an external magnetic field Hex. The MI element is also called a giant magneto-impedance element or a GMI element. The MI sensor is also called a giant magneto-impedance sensor or a GMI sensor.[0003]Patent Document 1: Japanese Unexamined Patent Application Publication No. 2000-258517[0004]As will be described below, a principle of magnetic field detection by the MI el...

AI Technical Summary

Benefits of technology

The present invention relates to a magneto-impedance element that reduces dH / dt, which is caused by the pulse current and can weaken the linearity of the induced voltage output, and improves the linearity between the external magnetic field and the induced voltage. The element achieves this by forming a conductive layer around the magnetic sensitive member and connecting them with opposite directions of pulse current flow. This results in a cancelled-out magnetic field outside the magnetic sensitive member and the conductive layer and only the dMθ / dt component varying depending on the external magnetic field can be detected. The element does not require a feedback circuit, reducing power consumption. Overall, the invention provides a magneto-impedance element with improved linearity without using a feedback circuit.

Problems solved by technology

For this reason, when time at which an output voltage of the detection coil reaches a peak is varied by an external magnetic field as shown in FIG. 12, if the external magnetic field is applied, voltages are sampled at a timing deviated from time at which the output voltage reaches a peak value, so that sensitivity and linearity are deteriorated because the output voltage drops.

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