JP2005061980A - Conductor current measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly precisely measure a current of a conductor by eliminating the effects of some position displacements of the conductor and noise and highly precisely detecting a magnetic field based on the conductor current by a method for detecting magnetic fields through the use of magnetic impedance effects. <P>SOLUTION: 2n-pieces (n is an even number) of magnetic impedance effect elements are provided in n-pairs on a circumference surrounding the conductor (e) with the center of the circumference as the center of symmetry. Groups 11-11' and 12-12' of N/2-pairs of first magnetic impedance effect elements among the n-pairs are connected to each other in such a way as to acquire the output sum of the magnetic impedance effect elements, and groups 13-13' and 14-14' of the remaining N/2-pairs of second magnetic impedance effect elements are connected to each other in such a way as to acquire the output sum of the magnetic impedance effect elements and further that the phase of the former sum output may be reverse to that of the latter sum output. This reverse phase output is subtracted by a subtractor 8, and a current of the conductor is measured on the subtracted output. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for measuring a conductor current by magnetic field detection.

As an amorphous alloy wire, an amorphous alloy wire having zero magnetostriction or negative magnetostriction has been developed that has an outer shell portion in which magnetic domains whose spontaneous magnetization directions are opposite to each other in the circumferential direction of the wire are separated by a domain wall. Yes.
The inductance voltage component in the output voltage across the wire generated when a high frequency excitation current is applied to the zero magnetostrictive or negative magnetostrictive amorphous magnetic wire is generated in the circumferential direction by the circumferential magnetic flux generated in the cross section of the wire. This occurs because the easily magnetizable outer shell is magnetized in the circumferential direction. Therefore, the circumferential magnetic permeability mu _theta depends on the circumferential direction of magnetization of Dosotokara portion.
Therefore, when a detected magnetic field is applied in the axial direction of the amorphous wire being energized, the outer circumferential direction magnetic field is easily magnetized by the synthesis of the circumferential magnetic flux and the detected magnetic flux generated by the energization. shift direction of the magnetic flux acting on the shell from the circumferential direction, correspondingly hardly occur magnetization in the circumferential direction, the circumferential permeability mu _theta changes, the inductance voltage content will vary.
Thus, this fluctuation phenomenon is called a magnetic inductance effect, which can be said to be a phenomenon in which the high-frequency excitation current (carrier wave) is modulated by a detected wave (modulated wave).

Further, when the frequency of the energization current is in the order of MHz, a high-frequency skin effect appears greatly, and the skin depth δ = (2ρ / wμ _θ ) ^1/2 (μ _θ is the circumferential permeability, as described above, ρ is electrical resistivity, w is shows the angular frequency, respectively) is changed by mu _theta, as the mu _theta is the so changed by the detected magnetic field, the resistance voltage division even be detected in the wire between both ends output voltage Fluctuates with a magnetic field.
Thus, this fluctuation phenomenon is called a magnetic impedance effect, which can be said to be a phenomenon in which the high-frequency excitation current (carrier wave) is modulated by a detected wave (modulated wave).

  Therefore, a detected magnetic field detection method using the magneto-impedance effect element (for example, see Patent Document 1) and a detected magnetic field detection method using the magnetic inductance effect (for example, see Patent Document 2) have been proposed.

JP 7-181239 A JP-A-6-283344

  As a method for measuring the conductor current I, it is well known that the conductor current I is measured by detecting the magnetic field strength H of the surrounding space based on the current I. That is, if the magnetic field strength at a point of an arbitrary closed curve c surrounding the conductor is H, the minute length at a point of the closed curve is Δl, and the conductor current is I, the law of the ampere circuit

  ∫cHdl = I

And the magnetic field strength H along the closed curve (circumference) having a radius r centered on the conductor center is

  H = I / (2πr)

If the magnetic field strength H is measured, the conductor current I can be obtained from this equation.
Therefore, it has been proposed to measure the conductor current I by detecting the magnetic field strength H by a magnetic impedance effect magnetic field detection method.

However, the inconvenience that the measurement error is likely to occur because the distance between the magneto-impedance effect amorphous wire and the conductor is deviated from the radius r or the axial direction of the magneto-impedance effect amorphous wire is deviated from the tangent of the circumference. There is.
Therefore, it is considered to provide a magnetic path made of an annular magnetic core around the conductor, provide a gap in the middle of the magnetic path, and dispose the magneto-impedance effect element in the gap. In this case, even if the conductor is displaced from the center of the annular magnetic core and the magnetic field distribution changes with respect to the annular magnetic core, the magnetic flux passing through the annular magnetic core will be maintained in its original state due to the strong magnetic conductivity of the magnetic core. Even if the conductor position is slightly deviated, the magnetic flux in the air gap in the middle of the annular magnetic core, that is, the magnetic flux passing through the magneto-impedance effect element can be kept sufficiently original and the magnetic field strength can be made sufficiently constant. Therefore, the measurement error of the conductor current due to the displacement of the conductor position can be well suppressed.
However, due to the strong magnetic conductivity of the annular magnetic core, a noise magnetic field such as geomagnetism passes and the influence of the noise magnetic field is inevitable.

  An object of the present invention is to detect a magnetic field based on a conductor current with high accuracy by eliminating a slight shift in the conductor position and the influence of noise by a method of detecting a magnetic field using the magneto-impedance effect. In addition to external magnetic field noise such as geomagnetism, the noise includes internal noise caused by a temperature change of the circuit element.

  The conductor current measuring method according to claim 1 detects a peripheral circuit magnetic field based on a conductor current by a magnetic field sensor that detects a magnetic field to be detected with a linear output characteristic capable of discriminating polarity by using a magneto-impedance effect element. This is a method of measuring current, and 2n (n is an even number) magneto-impedance effect elements are provided on the circumference surrounding the conductor in n pairs with the center of the circle as the center of symmetry. N / 2 pairs of the first magneto-impedance effect element groups are obtained so that the sum of the magneto-impedance effect element outputs is obtained, and the remaining n / 2 pairs of the second magneto-impedance effect element groups are also used as the magneto-impedance effect element. Install the former sum output and the latter sum output in opposite phase to obtain the sum of outputs, subtract this opposite phase output, and subtract this And measuring the conductor current based on the force.

The conductor current measuring method according to claim 2 is the conductor current measuring method according to claim 1, wherein a negative feedback coil is provided in the vicinity of each magnetoimpedance effect element to obtain linear output characteristics, and each magnetoimpedance effect element is provided. The negative feedback coils are connected in series, and each sum output of each magnetoimpedance effect element group is negatively fed back to each magnetoimpedance effect element group via each series connected negative feedback coil group.
3. The conductor current measuring method according to claim 1, wherein a bias magnetic field coil is provided in the vicinity of each magnetoimpedance effect element in order to obtain an output characteristic capable of discriminating polarity, and the bias magnetic field coil of each magnetoimpedance effect element. Can be connected in series.

  According to a fourth aspect of the present invention, there is provided a conductor current measuring method for detecting a peripheral circuit magnetic field based on a conductor current by a magnetic field sensor that detects a magnetic field to be detected with a linear output characteristic capable of discriminating polarity using a magneto-impedance effect element. This is a method of measuring current, and 2n (n is an even number) magneto-impedance effect elements are provided on the circumference surrounding the conductor in n pairs with the center of the circle as the center of symmetry. In order to obtain the sum of the output of the magneto-impedance effect element of the n / 2 pairs of the first magneto-impedance effect element group, the remaining n / 2 pairs of the magneto-impedance effect element groups of the n / 2 pairs of magneto-impedance effect elements In order to obtain the sum of outputs, the former sum output and the latter sum output are placed in opposite phases, and this opposite phase output is differentially amplified. And measuring the conductor current based on the dynamic amplification output.

  The conductor current measuring method according to claim 5 is the conductor current measuring method according to claim 4, wherein a negative feedback coil is provided in the vicinity of each magnetoimpedance effect element to obtain linear output characteristics, and each magnetoimpedance effect is measured. The negative feedback coil of the element is connected in series, and the differential amplification output is negatively fed back to the total magneto-impedance effect element group through the series connected negative feedback coil group.

The conductor current measuring method according to claim 6 is the conductor current measuring method according to any one of claims 1 to 5, wherein the magneto-impedance effect element group is installed so as to obtain a sum of magneto-impedance effect element outputs. It is characterized by performing in series connection.
7. The conductor current measuring method according to claim 4, wherein a bias magnetic field coil is provided in the vicinity of each magnetoimpedance effect element to obtain an output characteristic capable of discriminating polarity, and the bias magnetic field coil of each magnetoimpedance effect element. Can be connected in series.

  The conductor current measuring method according to claim 8 is the conductor current measuring method according to any one of claims 1 to 7, wherein the magneto-impedance effect element is disposed on one side of the substrate piece, and the magneto-impedance effect element is provided on the other side of the substrate piece. And using a magnetic field sensor having a magneto-impedance effect unit in which an iron core is arranged so as to constitute a magnetic circuit, and a bias magnetic field coil piece and a negative feedback coil piece are wound around the iron core. Features.

A large number of magneto-impedance effect elements are arranged on the circumference surrounding the conductor, and the group of these magneto-impedance effect elements forms a substantially annular magnetic path. Therefore, the axial direction of the magneto-impedance effect element is determined based on the conductor current. Even if there is a slight change in the magnetic field distribution, the passing magnetic field H can be held as it is by the magnetic conducting ring, and even if there is a slight shift in the conductor position, the conductor current can be kept stable in order to keep the magnetic field H stable. Measurement error can be reduced sufficiently.
In addition, since the magneto-impedance effect elements are arranged in pairs with the center of the circle surrounding the conductor as the center of symmetry, the external noise magnetic field has the same value and opposite phase to two magneto-impedance effect elements in the same pair. Therefore, because of the linear output characteristics that allow polarity discrimination, the sum output of the external magnetic field noise of the paired magneto-impedance effect elements becomes zero and is not output, thereby eliminating the influence of the external magnetic field noise.
Furthermore, since the 2n magneto-impedance effect elements are divided into two groups and the sum output of each set of magneto-impedance effect elements is subtracted or differentially amplified, the internal input to the subtractor or differential amplifier in the same phase Noise is not output and the influence of internal noise can be eliminated.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a basic circuit diagram in the case of detecting a magnetic field using the magneto-impedance effect. The high-frequency power source 2 for applying a high-frequency excitation current to the magneto-impedance effect element 1, the magneto-impedance effect element 1, and the magnetism A demodulating circuit 3 for demodulating the modulated wave obtained by modulating the high-frequency excitation current (carrier wave) with a detected magnetic field (modulated wave) H applied in the axial direction of the impedance effect element 1, an amplifying circuit 4 for amplifying the demodulated wave, It comprises an output end 5, a negative feedback coil 6, a bias magnetic field coil 7, and the like.
For the magneto-impedance effect element, zero magnetostrictive or negative magnetostrictive amorphous wire, amorphous ribbon, amorphous sputtered film or the like can be used.

In the magneto-impedance effect element 1, as described above, the direction of the magnetic flux acting on the outer shell portion that is easily magnetized in the circumferential direction by combining the circumferential magnetic flux based on the excitation current and the axial magnetic flux due to the detected magnetic field. Is shifted from the circumferential direction, the circumferential permeability μ _θ changes, the inductance is changed, and the impedance is changed by the change in the skin depth of the high frequency skin effect of this circumferential permeability μ _θ. . Accordingly, although even the circumferential direction positional shift phi by the synthesized magnetic field by ± of the detected magnetic field becomes ± phi, the circumferential direction of the magnetic field reduction ratio cos (± phi) is unchanged, the degree of reduction in thus mu _theta is of the detected magnetic field It does not change depending on the direction. Accordingly, the detected magnetic field-output characteristics are substantially bilaterally symmetrical with respect to the y axis when the detected magnetic field is taken on the x axis and the output is taken on the y axis as shown in FIG. This detected magnetic field-output characteristic is non-linear. With non-linear characteristics, it is difficult to measure with high sensitivity. Therefore, negative feedback is applied by the negative feedback coil 6 of FIG. 1 to linearize the characteristics as shown in FIG. In FIG. 2B, Δw is a linear range in which the gain A without negative feedback is very large and the gain is determined only by the feedback rate β. However, since the polarity of the detected magnetic field cannot be determined with this output characteristic, the polarity can be determined as shown in FIG. 2C by applying a bias magnetic field with the bias coil 7 of FIG. That is, the characteristic of (b) in FIG. 2 is moved in the negative direction of the x-axis by the bias magnetic field, and the maximum range −Hmax to + Hmax of the detected magnetic field is within the range of the single oblique line region. Further, as shown in FIG. 2 (d), a linear characteristic passing through the origin is obtained by adjusting the zero point. Therefore, in FIG. 2D, when the detected magnetic field is + He, the output is + Eo, and when the detected magnetic field is -He, the output is -Eo, and the detected magnetic field can be accurately measured based on polarity discrimination. .

FIG. 3 is a drawing showing an embodiment of a conductor current measuring method according to claims 1 and 2.
FIG. 3 (a) shows an arrangement pattern of 2n (n is an even number) magneto-impedance effect element, arranged on a circumference c surrounding the conductor e in n pairs of pairs with the circumference center as a symmetrical center. It is.
The direction of the paired magneto-impedance effect elements is set to have the same polarity with respect to the circumferential circuit magnetic field H based on the conductor current I. These n sets of magneto-impedance effect element pairs are divided into two groups of n / 2 pairs as shown in (b) of FIG. 3, and the two groups of magneto-impedance effect element groups are connected in series, and The directions of the two magneto-impedance effect element groups are reversed so that the sum output of one series-connected magneto-impedance effect element group and the sum output of the other series-connected magneto-impedance effect element group are in opposite phases. Reference numeral 2 denotes a high-frequency excitation current source, 3 (3 ′) denotes a demodulator circuit connected to the output terminal of each series-connected magnetoimpedance effect element group, and 4 and 4 ′ denote amplifiers connected to the demodulator circuits 3 and 3 ′.
61, 61 ', 62, 62', ... and 63, 63 ', 64, 64', ... are the magneto-impedance effect elements 11, 11 ', 12, 12', ... and 13, 13 ', 14 , 14 ′,..., 14 ′,... Are connected in series in the same manner as the series-connected magneto-impedance effect element group, and the outputs of the amplifiers 4 and 4 ′ are connected to the series-connected magneto-impedance effect. Negative feedback is made to the element groups 11, 11 ′, 12, 12 ′,..., 13, 13 ′, 14, 14 ′,. 71, 71 ′, 72, 72 ′,..., 73, 73 ′, 74, 74 ′,... Are the magneto-impedance effect elements 11, 11 ′, 12, 12 ′,. , 14 ′,..., 14,..., 14,..., Bias magnetic field coil connected in series like the series-connected magnetoimpedance effect element group, and biased with a polarity corresponding to the polarity of the series-connected magnetoimpedance effect element group A magnetic field is applied. It is also possible to connect the bias magnetic field coils 71, 71 ′, 72, 72 ′,... And 73, 73 ′, 74, 74 ′,.
8 is a subtractor for subtracting the outputs of both amplifiers 4 and 4 '.

In FIG. 3A, when H is a peripheral circuit magnetic field based on the current I of the conductor e, the series-connected magneto-impedance effect element groups 11, 11 ′, 12, 12 ′ as shown in FIG. ,... And 13, 13 ′, 14, 14 ′,... Have the same strength and the same phase, and both series-connected magneto-impedance effect element groups 11, 11 ′, 12, 12 ′, .., 13, 13 ′, 14, 14 ′,... Are opposite in direction, so that the sum output of the two series-connected magneto-impedance effect element groups is only the same value / reverse phase. Therefore, the reverse phase output is input to the subtracter 8 to obtain an output proportional to H.
The sum output of the series-connected magneto-impedance effect element groups 11, 11 ′, 12, 12 ′,... (13, 13 ′, 14, 14 ′,...) For the magnetic field H is the magneto-impedance effect elements 11, 11 ′, 12, 12 ′,... (13, 13 ′, 14, 14 ′,...) Is approximately proportional to the total length, and if the length is w, a magnetic field H is applied to the magneto-impedance effect element having the length w. The output can be easily detected by obtaining in advance the linear output characteristics of the magneto-impedance effect element that can be discriminated in polarity as shown in FIG. If the radius of the circumference c is r,

  I = 2πrH

The conductor current can be measured from

  In this case, in FIG. 3A, since a substantial portion of the circumference circuit of the circumference c where the magneto-impedance effect element is disposed is occupied by an amorphous magnetic material having a high magnetic permeability, the magnetism of the circumference circuit is Is sufficiently high, even if the magnetic field distribution changes due to the displacement of the conductor, the magnetic flux passing through the highly conductive peripheral circuit tends to be kept as it is, and as a result, the output variation due to the displacement of the conductor is well suppressed. Therefore, the measurement error of the conductor current due to the displacement of the conductor can be sufficiently reduced, and the conductor current can be measured with sufficiently high accuracy.

  Further, as shown in FIG. 3A, in the external magnetic field noise H ′, the components acting in the axial direction of the same pair of magneto-impedance effect elements 1m and 1m ′ have the same strength (strength | H ′ cos θ |, θ is the angle between the magnetic field H ′ and the magneto-impedance effect element), and the phase is reversed. Therefore, the output is performed under the linear output characteristics shown in FIG. Therefore, the external noise magnetic field is not output to the output terminal of the subtracter 8.

Even if internal noise based on a temperature change or the like occurs in the demodulation circuits 3 and 3 ′ and the amplifiers 4 and 4 ′, the internal noise generated in the demodulation circuit 3 and the amplification circuit 4, the demodulation circuit 3 ′, and the amplification circuit 4 ′. Are not output to the output terminal of the subtractor 8 because they are in phase with each other.
Therefore, according to the first and second aspects, the conductor current can be measured with sufficiently high accuracy by eliminating the influence of the internal and external noise.

FIG. 4 is a drawing showing an embodiment of a conductor current measuring method according to claims 3-4.
FIG. 4A shows an arrangement pattern of 2n (n is an even number) magneto-impedance effect element. Similarly to the above, on the circumference c surrounding the conductor e, a pair of symmetrical centers of the circumference center is shown. n sets are arranged. The direction of the paired magneto-impedance effect elements is set to have the same polarity with respect to the circumferential circuit magnetic field H based on the conductor current I. These n sets of magnetoimpedance effect element pairs are divided into two groups 11, 11 ′, 12, 12 ′,..., And 13, 13 ′, 14,. 14 ′,... And these two groups of magneto-impedance effect element groups are connected in series, and the sum output of one of the series-connected magneto-impedance effect element groups 11, 11 ′, 12, 12 ′,. The direction of the two magneto-impedance effect element groups is reversed so that the sum output of the other series-connected magneto-impedance effect element groups 13, 13 ′, 14, 14 ′,. Reference numeral 3 (3 ′) denotes a demodulation circuit connected to the output terminal of each series-connected magnetoimpedance effect element group, and reference numeral 40 denotes a differential amplifier connecting the output terminals of both demodulation circuits 3 and 3 ′.
61, 61 ', 62, 62', ... and 63, 63 ', 64, 64', ... are the magneto-impedance effect elements 11, 11 ', 12, 12', ... and 13, 13 ', 14 , 14 ′,..., And negative feedback coils 61, 61 ′, 62, 62 ′,... And 63, 63 ′, 64, 64 ′,. In series connection, the output of the differential amplifier 40 is negatively fed back to the series connection magneto-impedance effect element groups 11, 11 ′, 12, 12 ′,..., 13, 13 ′, 14, 14 ′,. . The direction of the negative feedback magnetic field is opposite to the direction of the detected magnetic field H, and the series-connected magneto-impedance effect element groups 11, 11 ′, 12, 12 ′,..., 13, 13 ′, 14, 14 ′,. Since the direction of the detected magnetic field H with respect to ... is the same, the direction of the negative feedback magnetic field in which the negative feedback coils 61, 61 ', 62, 62', ... are generated and the negative feedback coils 63, 63 ', 64, ... The direction of the negative feedback magnetic field where 64 ', ... is generated is the same direction. 71, 71 ′, 72, 72 ′,..., 73, 73 ′, 74, 74 ′,... Are the magneto-impedance effect elements 11, 11 ′, 12, 12 ′,. , 14 ′,..., 14,..., 14,..., Bias magnetic field coil connected in series like the series-connected magnetoimpedance effect element group, and biased with a polarity corresponding to the polarity of the series-connected magnetoimpedance effect element group A magnetic field is applied. As shown in FIG. 5, the bias magnetic field coils 71, 71 ′, 72, 72 ′,..., And 73, 73 ′, 74, 74 ′,. The bias magnetic field coils 71, 71 ', 72, 72', ... and 73, 73 ', 74, 74', ... are reversed in polarity by reversing the winding direction or the like.
4 (a), if H is a peripheral circuit magnetic field based on the conductor current I, as shown in FIG. 4 (b), the series-connected magnetoimpedance effect element groups 11, 11 ′, 12, 12 ′,. .. And 13, 13 ', 14, 14',... Have the same strength and the same phase, and both series-connected magnetoimpedance effect element groups 11, 11 ', 12, 12',. And 13, 13 ′, 14, 14 ′,... Are opposite in direction, so that the sum output of both series-connected magneto-impedance effect element groups has only the same value and opposite phase components. Therefore, the negative phase output is input to the differential amplifier 40, and an output proportional to H is obtained.
The sum output of the series-connected magneto-impedance effect element groups 11, 11 ′, 12, 12 ′,... (13, 13 ′, 14, 14 ′,...) For the magnetic field H is the magneto-impedance effect elements 11, 11 ′, 12, 12 ′,... (13, 13 ′, 14, 14 ′,...) Is approximately proportional to the total length, and if the length is w, a magnetic field H is applied to the magneto-impedance effect element having the length w. The output can be easily detected by obtaining in advance the linear output characteristics of the magneto-impedance effect element that can be discriminated in polarity as shown in FIG. If the radius of the circumference c is r,

  I = 2πrH

The conductor current can be measured from

In this case, in FIG. 4A, since a substantial portion of the circumference circuit of the circumference c where the magneto-impedance effect element is disposed is occupied by an amorphous magnetic material having a high magnetic permeability, the magnetism of the circumference circuit is Is sufficiently high, even if the magnetic field distribution changes due to the displacement of the conductor, the magnetic flux passing through the highly conductive peripheral circuit tends to be kept as it is, and as a result, the output variation due to the displacement of the conductor is well suppressed. Therefore, the measurement error of the conductor current due to the displacement of the conductor can be sufficiently reduced, and the conductor current can be measured with sufficiently high accuracy.
Further, as shown in FIG. 4A, in the external magnetic field noise H ′, the components acting in the axial direction of the same pair of magneto-impedance effect elements 1m and 1m ′ have the same strength and the opposite phases. Therefore, no output is performed under the linear output characteristics shown in FIG. 2 (d) in which the polarity can be discriminated. Therefore, the external noise magnetic field is not output to the output terminal of the differential amplifier.
Even if internal noise based on a temperature change or the like is generated in the demodulation circuits 3 and 3 ′, the internal noise generated in the demodulation circuit 3 and the demodulation circuit 3 ′ is in phase with each other. Is not output.
Therefore, according to claims 3 to 4, it is possible to measure the conductor current with sufficiently high accuracy by eliminating the influence of the internal and external noise.

In any of the above embodiments, negative feedback is applied to linearize the output characteristics. However, in the case of the differential amplification method, the direction of the bias magnetic field Hb applied to one magnetoimpedance effect element as shown in FIG. And the direction of the bias magnetic field Hb applied to the other magneto-impedance effect element are opposite directions, and demodulated outputs (magnetic field detection signals) having opposite phases to each other are represented by E ₊ and E ₋ , and the difference is represented by E _± . Thus, it is possible to omit the negative feedback.

  In any of the above-described embodiments, the sum output of the magneto-impedance effect element group is obtained by connecting the magneto-impedance effect element group in series. However, the present invention is not limited to this. For example, the magneto-impedance effect element group 11, 11 ′, 12, 12 ′,... (13, 13 ′, 14, 14 ′,...), The output current of each magnetoimpedance effect element 1m (1m ′) is merged into one detection impedance, and this current It is also possible to take out the detected impedance voltage based on.

  The arrangement interval of the magneto-impedance effect elements on the circumference c may be equal intervals in order to stably maintain the magnetic field H by the above-described magnetic conducting ring, and / or may be as narrow as possible. It is valid.

The combination of the n pairs of magneto-impedance effect elements into two groups of pairs is nC2 as long as the pairs are 11-11 ', 12-12', ... 1m-1m ', ... 1N ₁ n'. Yes, when n = 1, there is one set of 11-11 ′ and 12-12 ′. Therefore, when n = 1, the sum output of the magneto-impedance effect element group is the sum output of the magneto-impedance effect element 11 (11 ′) and the magneto-impedance effect element 12 (12 ′).

  FIG. 7 shows an example of a magnetic field sensor (in the case of n = 2) used in the present invention. A hole 92 with a notch 921 for inserting a conductor is formed in an insulating substrate 91, and on the circumference surrounding this hole. Two pairs (11-11 ′, 12-12 ′) of magneto-impedance effect elements having the center of symmetry as the center of symmetry are arranged, and a high-frequency exciting current source 2, demodulating circuits 3, 3 ′, and amplifiers 4, 4 ′ An adder or the like 8 or a high-frequency excitation current source, a demodulation circuit, a differential amplifier and the like are mounted. Reference numerals 61, 61 ', 62 and 62' denote negative feedback coils, 71, 71 ', 72 and 72' denote bias magnetic field coils, and e denotes a conductor.

In this case, it is preferable that the magneto-impedance effect element, the negative feedback coil, and the bias magnetic field coil are unitized to reduce the size of the sensor body and to make the entire magnetic sensor compact.
FIG. 8 is a side view showing an example of the magneto-impedance effect unit, FIG. 8B is a bottom view, and FIG. 8C is a cross-sectional view of FIG.
In FIG. 8, reference numeral 100 denotes a substrate piece, for example, a ceramic plate can be used. Reference numeral 101 denotes an electrode provided on one surface of the substrate piece, and includes an element connecting projection 102. This electrode can be provided by printing and baking a conductive paste, for example, a silver paste. 1x is a magneto-impedance effect element connected between the protrusions 102 and 102 of the electrodes 101 and 101 by soldering or welding, and the above-described zero or negative magnetostrictive amorphous wire, amorphous ribbon, sputtered film, or the like can be used. 103 is a C-type iron core, 6x is a negative feedback coil wound around the C-type iron core, and 7x is also a bias magnetic field coil. The field magnetic impedance effect element piece 1x and the C-type iron core 103 are used as a loop magnetic circuit. Both ends of the C-type iron core 103 are fixed to the other surface of the substrate piece 100 with an adhesive or the like.
The iron core material may be a magnetic material having a small residual magnetic flux density, and examples thereof include permalloy, ferrite, iron, amorphous magnetic alloy, magnetic powder mixed plastic, and the like.

In the above, if the length of the C-type iron core is l _a , the cross-sectional area is S _a , and the magnetic permeability is μ _a , the magnetic resistance R _a of the C-type iron core is

R _a = l _a / (S _a μ _a )

Further, if the length of the magneto-impedance effect element portion that is a component of the magnetic circuit is l _b , the cross-sectional area is S _b , and the magnetic permeability is μ _b , the magneto-resistance R _b of the magneto-impedance effect element portion is given. Is

R _b = l _b / (S _b μ _b )

Further, if the magnetic resistance between the both ends of the C-type iron core and the magneto-impedance effect element is R _c , the magnetic resistance R _m of the magnetic circuit is

R _m = R _a + R _b + R _c

Therefore, the self-inductance L ₁ of the negative feedback magnetic field generating coil is represented by N ₁ as the number of turns of the coil.

L ₁ = N ₁ ² / R _m

The self-inductance L ₂ of the bias magnetic field coil is expressed as N ₂

L ₂ = N ₂ ² / R _m

Given in.
The而Ru, the can reduce the thickness is thin R _c of the substrate 100, also kept the height of the legs of the C-type iron core to an extent that slightly higher than the diameter of the winding of the C-type iron core length since can be shortened, the magnetic resistance R _m of the magnetic circuit be sufficiently low, the results can be correspondingly reduced number of turns N of the coils, the coils themselves can be miniaturized.

The configuration of the magnetic field sensor using the magneto-impedance effect unit is, for example, as shown in FIG. 9 when n = 2, and the magneto-impedance effect units U1, U1 ′, U2, U2 ′ are provided with conductor insertion holes 92. A plurality of pairs U1-U1 ′, U2-U2 ′ sandwiching the center of the circumference on the circumference c surrounding the hole 92 of the substrate 91, and the magnetosensitive effect elements are mounted in the same direction, In each of the pair of magneto-impedance effect units U1-U1 ′ and U2-U, a magneto-impedance effect element, a negative feedback coil, and a bias magnetic field coil are connected in series, and an exciting current source circuit for the series-connected magneto-impedance effect element 2 and a demodulation circuit 3, 3 'for amplifying the detected amount corresponding to the detected magnetic field from the magnetic field detection signal or amplification 2 or 4 ′ or a differential amplifier is mounted, negative feedback is applied through a negative feedback coil connected in series in the same manner as described above, and a bias magnetic field is applied by a bias magnetic field coil as shown in FIG. Such a linear output capable of discriminating the polarity is obtained.
When mounting this magneto-impedance effect unit on a substrate, it is desirable to fix the unit substrate to the substrate with an adhesive so that the magneto-impedance effect element side of the unit faces the substrate for mechanical protection of the magneto-impedance effect element. .
In Figure 8, a magnetic resistance R _w of the magneto-impedance effect units for the conductor current magnetic field H, the magnetic resistance of the C-type iron core R _a, the magnetic resistance of the magneto-impedance effect element portion as R _b

R _w = R _a R _b / (R _a + R _b )

Since the magnetic resistance _Rb of the magneto-impedance effect element alone can be lowered, the conductivity of the peripheral circuit c can be further increased, and the measurement accuracy of the conductor current can be improved by further stabilizing the distribution state of the detected magnetic field H. Can be improved.

  As another example of the magneto-impedance effect unit, a magneto-impedance effect element is provided on the surface of the insulating base plate, and a negative feedback coil and a bias magnetic field coil are provided on the other surface of the insulating base plate by printing. be able to.

  As the high-frequency exciting current, for example, a normal high frequency such as a continuous sine wave, a pulse wave, or a triangular wave can be used. In addition to the normal oscillation circuit, a rectangular wave generator that integrates the square wave output of the crystal oscillator via a DC component cut-off capacitor by an integration circuit and amplifies the triangular wave of the integration output by an amplification circuit, and a CMOS-IC as an oscillation unit The used triangular wave generator etc. can be used.

The demodulating circuit includes, for example, a configuration in which a modulated wave is half-wave rectified by an operational amplifier circuit, and this half-wave rectified wave is processed by a parallel RC circuit or an RC low-pass filter to obtain an envelope output of the half-wave rectified wave. A configuration in which the modulated wave is half-wave rectified by a diode and the half-wave rectified wave is processed by a parallel RC circuit or an RC low-pass filter to obtain an envelope output of the half-wave rectified wave can be used.
In the above embodiment, the detected amount is extracted by demodulating the modulated wave. However, the present invention is not limited to this, and the detected amount corresponding to the detected magnetic field is detected from the magnetic field detection signal by the detected magnetic field acting on the magneto-impedance effect element. Any suitable circuit configuration can be used.

In the above embodiment, the negative feedback coil and the bias magnetic field coil are separated from each other. For example, each magnetic impedance effect is applied to the upper side of the circuit shown in FIG. A single coil 671, 671 ′, 672, 672 ′ is disposed in the vicinity of the elements 11, 11 ′, 12, 12 ′, and each single coil 671, 671 ′, 672 is disposed as shown in FIG. 672 'are connected in series, and the superimposed signal of the DC bias signal and the negative feedback signal is sent to the series-connected coils 671, 671', 672, 672 'by the arithmetic circuit Q, and the series-connected magneto-impedance effect element group 11 is connected. 11 ′, 12 and 12 ′ can be negatively fed back and biased to obtain a linear output characteristic capable of discriminating the polarity as shown in FIG.
In the example of FIG. 10, an operational amplifier (negative feedback path insertion impedance Z ₂ , input side insertion impedance Z ₁ ) with negative feedback applied to the inverting input terminal from the output is used, and the resistance inserted in the series connection coil is R When the number of turns of the series connection coil is N, the length is L, the gain of the demodulation amplification unit B is A, the detected magnetic field is Hex, and the output is Eout,

A >> Z ₁ RL / (Z ₂ N)

Under

Eout = RLZ ₁ Hex / (NZ ₂ ) + VccZ ₁ R / [Z ₂ (Z ₂ + R)]

This output characteristic can be shifted in the ± direction of the x-axis by adjusting the constants (Z ₁ , Z ₂ , resistance R, coil turns N, etc.), and the diagonal straight line portion whose polarity can be discriminated by the adjustment 2 can be positioned within the range of the maximum detected magnetic field ± Hmax, and the linearity output characteristics capable of discriminating the polarity as shown in FIG. 2 (d) can be obtained by adjusting the zero point in the y-axis direction. it can.

  Since the magnetic impedance detection element has a high magnetic field detection sensitivity, it is possible to measure a weak current with high accuracy by high sensitivity detection of a weak magnetic field.

It is a circuit diagram for showing a magnetic field measurement method using a magnetic field impedance effect used in the present invention. It is drawing which shows the output characteristic of the magnetic field measuring method used in this invention. It is drawing which shows the Example of the conductor current measuring method which concerns on Claims 1-2. It is drawing which shows the Example of the conductor current measuring method which concerns on Claims 3-4. It is drawing which shows another Example of the conductor current measuring method which concerns on Claims 3-4. It is drawing which shows the output characteristic of another Example of the conductor current measuring method which concerns on Claim 3. It is drawing which shows an example of the magnetic field sensor used in this invention. It is drawing which shows an example of the magnetic field impedance effect unit used in the conductor current measuring method which concerns on Claim 6. It is drawing which shows an example of the magnetic field sensor used in the conductor current measuring method which concerns on Claim 6. It is drawing which shows another example of the negative feedback and bias means used in the conductor current measuring method which concerns on this invention.

Explanation of symbols

11, 12, ... Magnetic impedance effect element 11 ', 12', ... Magnetic impedance effect element 11-11 ', 12-12' Magnetic impedance effect element pair 2 High frequency excitation current source 3, 3 'Demodulation circuit 4, 4' Amplifying circuit 40 Differential amplifier 61, 62 ... Negative feedback coil 61 ', 62' ... Negative feedback coil 71, 72 ... Bias magnetic field coil 71 ', 72' ... Bias magnetic field coil H Detected magnetic field H 'External noise Magnetic field e conductor

Claims (8)

Surrounding the conductor by detecting the peripheral circuit magnetic field based on the conductor current using a magnetic field sensor that detects the magnetic field to be detected with a linear output characteristic capable of discriminating the polarity using a magneto-impedance effect element. 2n (n is an even number) magneto-impedance effect elements are provided on the circumference as n pairs with the circumference center as the center of symmetry, and n / 2 pairs of first magnetic pairs of the n pairs are provided. In order to obtain the sum of the magneto-impedance effect element outputs for the impedance effect element group, and so as to obtain the sum of the magneto-impedance effect element outputs for the remaining n / 2 pairs of the second magneto-impedance effect element group. Install the sum output and the latter sum output in opposite phase, subtract these opposite phase outputs from each other, and measure the conductor current based on this subtracted output. Conductor current measuring method, characterized in that. In order to obtain linear output characteristics, a negative feedback coil is arranged in the vicinity of each magnetoimpedance effect element, the negative feedback coils of each magnetoimpedance effect element are connected in series, and each sum output of each magnetoimpedance effect element group 2. The method of measuring a conductor current according to claim 1, wherein a negative feedback is fed back to each magnetoimpedance effect element group via each series-connected negative feedback coil group. 2. A bias magnetic field coil is provided in the vicinity of each magnetoimpedance effect element in order to obtain output characteristics that allow polarity discrimination, and the bias magnetic field coil of each magnetoimpedance effect element is connected in series. Or the conductor current measuring method of 2. Surrounding the conductor by detecting the peripheral circuit magnetic field based on the conductor current using a magnetic field sensor that detects the magnetic field to be detected with a linear output characteristic capable of discriminating the polarity using a magneto-impedance effect element. 2n (n is an even number) magneto-impedance effect elements are provided on the circumference as n pairs with the circumference center as the center of symmetry, and n / 2 pairs of first magnetic pairs of the n pairs are provided. In order to obtain the sum of the magneto-impedance effect element outputs for the impedance effect element group, and so as to obtain the sum of the magneto-impedance effect element outputs for the remaining n / 2 pairs of the second magneto-impedance effect element group. Install the sum output and the latter sum output in opposite phase, differentially amplify this opposite phase output, and measure the conductor current based on this differentially amplified output Conductor current measuring method comprising Rukoto. In order to obtain linear output characteristics, a negative feedback coil is arranged in the vicinity of each magnetoimpedance effect element, the negative feedback coil of each magnetoimpedance effect element is connected in series, and the differential amplification output is connected in series for negative feedback. 5. The conductor current measuring method according to claim 4, wherein negative feedback is performed to the total magneto-impedance effect element group via the coil group. 6. The conductor current measuring method according to claim 1, wherein the magneto-impedance effect element group is installed so as to obtain a sum of magneto-impedance effect element outputs by serial connection of the magneto-impedance effect elements. 5. A bias magnetic field coil is provided in the vicinity of each magnetoimpedance effect element in order to obtain polarity distinguishable output characteristics, and the bias magnetic field coil of each magnetoimpedance effect element is connected in series. The conductor current measuring method according to any one of? A magnetic impedance effect element is disposed on one surface of a substrate piece, and an iron core is disposed on the other surface of the substrate piece so as to form a magnetic circuit with the magnetic impedance effect element, and a bias magnetic field coil piece is disposed on the iron core. And a magnetic field sensor having a magneto-impedance effect unit formed by winding a coil piece for negative feedback and a negative feedback coil piece.

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