JP4660709B2 - Extended differential fluxgate sensor - Google Patents

Description

  The present invention relates to an extended differential fluxgate sensor, and more particularly, to an extended differential fluxgate sensor capable of extending the length of a region where a magnetic field can be detected while keeping a baseline length small.

  Conventionally, a differential magnetic field detection coil comprising a racetrack-shaped core, an excitation coil wound around the core in a toroidal shape, and two differential windings wound in opposite directions with a gap between the linear portions of the core. A common magnetic field detection coil comprising one common winding wound between two differential windings, a first feedback circuit that feeds back a feedback signal to the output of the differential magnetic field detection coil, and common magnetic field detection A differential fluxgate sensor including a second feedback circuit that feeds back a feedback signal to the output of a coil is known (for example, see Non-Patent Document 1).

P.Ripka, K.Draxler and P.Kaspar "RACE-TRACK FLUXGATE GRADIOMETER" ELECTRONICS LETTERS 24th June 1993 Vol.29 No.13 pp.1193-1194

In the conventional differential fluxgate sensor, the interval between the differential windings (hereinafter referred to as the baseline length) defines the length of the region where the magnetic field can be detected.
However, in order to eliminate the influence of the external magnetic field, it is necessary to keep the baseline length small, and there is a problem that the length of the region where the magnetic field can be detected is limited to several centimeters at most. In other words, if the base line length is increased in order to extend the length of the region where the magnetic field can be detected, there is a problem that it is easily affected by the external magnetic field.
Accordingly, an object of the present invention is to provide an extended differential fluxgate sensor that can extend the length of a region where a magnetic field can be detected while keeping the baseline length small.

In the first aspect, the present invention provides a core, an excitation coil wound around the core, and 2 × N (N is an integer of 2 or more) wound around the core alternately in a reverse direction at a pitch L. Feedback signal is fed back to the output of the differential magnetic field detection coil consisting of a differential magnetic field detection coil, the common magnetic field detection coil consisting of one or more common windings wound around the core in one direction, and the differential magnetic field detection coil There is provided an extended differential type fluxgate sensor comprising: a first feedback circuit configured to perform feedback; and a second feedback circuit configured to feed back a feedback signal to the output of the common magnetic field detection coil.
In the extended differential fluxgate sensor according to the first aspect, the base line length, that is, the interval between adjacent differential windings wound in the reverse direction is the pitch L. On the other hand, the length of the region where the magnetic field can be detected is the interval between the differential windings at both ends, and is “(2 × N−1) × L”. That is, the length of the region in which the magnetic field can be detected can be extended to “2 × N−1” times the base line length, and at least three times the base line length. That is, the length of the region where the magnetic field can be detected can be extended while keeping the baseline length small.

In a second aspect, the present invention provides the extended differential fluxgate sensor according to the first aspect, wherein the core has two parallel straight portions longer than “(2 × N−1) × L”. An extended differential fluxgate sensor characterized by having a track shape is provided.
In the extended differential fluxgate sensor according to the second aspect, the core has a racetrack shape having two parallel straight portions longer than “(2 × N−1) × L”. 2 × N differential windings can be suitably wound so as to surround them.

In a third aspect, the present invention is the extended differential fluxgate sensor according to the second aspect, wherein the common magnetic field detection coil is a single common coil wound uniformly distributed on the straight portion of the core. An extended differential fluxgate sensor characterized by comprising windings is provided.
In the extended differential fluxgate sensor according to the third aspect, since the common magnetic field detection coil is uniformly distributed and wound around the linear portion of the core, the common magnetic field applied to all the differential windings is common. Can be detected efficiently.

  According to the extended difference type fluxgate sensor of the present invention, the length of the region where the magnetic field can be detected can be extended to three times or more the baseline length. That is, the length of the region where the magnetic field can be detected can be extended while keeping the baseline length small.

  Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited thereby.

FIG. 1 is a configuration diagram illustrating an extended differential fluxgate sensor 10 according to the first embodiment.
This extended differential type fluxgate sensor 10 includes a racetrack-shaped core 1 having two parallel straight portions having a length of 3 × L or more, an excitation coil 2 wound around the core 1 in a toroidal shape, and a core 1. The differential magnetic field detection coil 3 composed of four differential windings 3a, 3b, 3c, and 3d, which are alternately wound in the reverse direction at a pitch L so as to surround the two linear portions, and the two linear portions of the core 1 The feedback signal D is negatively fed back to the common magnetic field detection coil 4 composed of a single common winding wound in one direction with a uniform distribution so as to surround the differential magnetic field detection signal B from the differential magnetic field detection coil 3. A first feedback circuit 5 and a second feedback circuit 6 that negatively feeds back the feedback signal F to the common magnetic field detection signal E from the common magnetic field detection coil 4 are provided.

The first feedback circuit 5 includes a capacitance 51 that extracts an AC component from the sum signal of the differential magnetic field detection signal B and the feedback signal D, an amplifier 52 that amplifies the AC component, a detector 53 that extracts the signal component, and a low-frequency component. Is provided with a low-pass filter 54 that extracts the low-frequency component, an integrator 55 that integrates a low-frequency component, and a voltage-current converter 56 that converts the output voltage of the integrator 55 into a feedback signal D for feedback.
Here, the voltage-current converter 56 has a strength corresponding to a value obtained by dividing the magnitude of the differential magnetic field detection signal B when there is no feedback by the number of differential windings 2 × N, and the differential magnetic field detection signal B is It is assumed that a feedback signal D having a magnitude that causes the differential windings 3a, 3b, 3c, and 3d to generate magnetism in the direction opposite to the generated magnetism is generated.

The second feedback circuit 6 includes a capacitance 61 that extracts an AC component from the sum signal of the common magnetic field detection signal E and the feedback signal F, an amplifier 62 that amplifies the AC component, a detector 63 that extracts the signal component, and a low-frequency component. A low-pass filter 64 that extracts the low-frequency component, an integrator 65 that integrates a low-frequency component, and a voltage-current converter 66 that converts the output voltage of the integrator 65 into a feedback signal F and feeds it back.
Here, the voltage-current converter 66 has a strength corresponding to the magnitude of the common magnetic field detection signal E when there is no feedback and converts the magnetism in the opposite direction to the magnetism that generated the common magnetic field detection signal E to the common magnetic field. It is assumed that a feedback signal F having a magnitude generated by the detection coil 4 is generated.

  As shown in FIG. 2, it is assumed that a weak magnetic field α from a magnetic source in the vicinity is applied only to the first differential winding 3a, and an external magnetic field β from a magnetic source at a long distance is applied. Also, α << β.

  As shown in FIG. 3, the output of the second feedback circuit 6 is a signal corresponding to the external magnetic field β. The feedback signal F generates a feedback magnetic field f having the same strength as the external magnetic field β and in the opposite direction. As a result, the external magnetic field β is canceled by the feedback magnetic field f, and the operating point on the BH curve of the core 1 can be fixed. Further, the input of the amplifier 62 can be maintained near zero with good linearity.

  On the other hand, the external magnetic field β is canceled by the feedback magnetic field f, and the weak magnetic field α is applied only to the first differential winding 3a. Therefore, the output of the first feedback circuit 5 is a signal corresponding to the weak magnetic field α. Further, the feedback signal D generates a feedback magnetic field a having a strength α / 4 at the first differential winding 3a and opposite to the weak magnetic field α, and has a strength α / 4 at the second differential winding 3b and is weak. A feedback magnetic field b having the same direction as the magnetic field α is generated, a feedback magnetic field c having a strength α / 4 and a direction opposite to the weak magnetic field α is generated by the third differential winding 3c, and the strength is generated by the fourth differential winding 3d. A feedback magnetic field d that is α / 4 and has the same direction as the weak magnetic field α is generated. Thereby, in the first differential winding 3a, a magnetic field “α-a” having a strength of 3α / 4 and the same direction as the weak magnetic field α is detected by the clockwise winding, and the electromotive force is equivalent to 3α / 4. In the second differential winding 3b, the magnetic field b having the strength α / 4 and the same direction as the weak magnetic field α is detected by the counterclockwise winding, and the electromotive force is equivalent to −α / 4. In 3c, a magnetic field c having a strength α / 4 and opposite to the weak magnetic field α is detected by a clockwise winding, and the electromotive force is equivalent to −α / 4. In the fourth differential winding 3d, the strength α / 4 and the magnetic field d in the same direction as the weak magnetic field α is detected by the counterclockwise winding, the electromotive force is equivalent to −α / 4, and the total difference magnetic field signal B becomes zero, and the input of the amplifier 52 Can be maintained near zero with good linearity.

According to the extended differential fluxgate sensor 10 according to the first embodiment, the following effects can be obtained.
(A) The length of the region where the magnetic field can be detected can be extended to three times the baseline length L. That is, the length of the region where the magnetic field can be detected can be extended while keeping the baseline length L small.
(B) Since the core has a racetrack shape having two parallel straight portions longer than 3 × L, the four differential windings 3a, 3b, 3c, and 3d are preferably arranged so as to surround the two straight portions. Can be wound.
(C) Since the common magnetic field detecting coil 4 is uniformly distributed and wound around the straight portion of the core 1, the common magnetic field applied to all the differential windings 3a, 3b, 3c, 3d is efficiently used. It can be detected well.

  As shown in FIG. 4, common windings 4a, 4b, and 4c are wound in the same direction between the four differential windings 3a, 3b, 3c, and 3d, and are connected in series. It is good.

  The number of differential windings is not limited to four, and may be 6, 8, 10,.

  The extended differential fluxgate sensor of the present invention can be used as a magnetic sensor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram illustrating a configuration of an extended differential fluxgate sensor according to a first embodiment. It is explanatory drawing which shows the magnetic field concerning the extended difference type flux gate sensor which concerns on Example 1. FIG. It is explanatory drawing which shows the magnetic field which generate | occur | produces from the extended difference type | mold fluxgate sensor which concerns on Example 1. FIG. FIG. 6 is a configuration explanatory view showing an extended differential fluxgate sensor according to a second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core 2 Excitation coil 3 Differential magnetic field detection coil 3a, 3b, 3c, 3d Differential winding 4 Common magnetic field detection coil 4a, 4b, 4c Common winding 5 1st feedback circuit 6 2nd feedback circuit 10 Extended differential type flux Gate sensor

Claims (3)

Differential magnetic field detection comprising a core, an excitation coil wound around the core, and 2 × N (N is an integer of 2 or more) differential windings wound alternately around the core in a reverse direction at a pitch L A common magnetic field detection coil comprising a coil, one or more common windings wound around the core in one direction, a first feedback circuit for feeding back a feedback signal to the output of the differential magnetic field detection coil, and the common An extended differential fluxgate sensor comprising: a second feedback circuit that feeds back a feedback signal to the output of the magnetic field detection coil. 2. The extended differential fluxgate sensor according to claim 1, wherein the core has a racetrack shape having two parallel straight portions longer than “(2 × N−1) × L”. Differential fluxgate sensor. 3. The extended differential fluxgate sensor according to claim 2, wherein the common magnetic field detection coil is composed of one common winding wound uniformly distributed on the straight portion of the core. Differential fluxgate sensor.

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