JP2005055326A - Conductor current measurement method and magnetic field sensor for measuring conductor current - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure a conductor current with high precision by detecting a magnetic field based on the conductor current with high precision, excluding influence by a noise magnetic field and some shift in the conductor position, by a method of detecting the magnetic field utilizing a magnetic impedance effect. <P>SOLUTION: When the conductor current is measured by detecting the magnetic field based on the conductor current around the conductor utilizing the magnetic impedance effect, two or more magnetic impedance effect element pieces 11-14 are arranged on a circumference surrounding the conductor so as to make the directions of each pair of magnetic impedance effect element pieces 11, 13 (12, 14) interposing the center of the circumference c the same direction. By series-connecting these magnetic impedance effect element pieces, a magnetic impedance effect element is formed, and by serially connected coil pieces 61-64 for magnetic feedback arranged near the individual magnetic impedance effect element pieces, a coil for negative feedback is formed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for measuring a conductor current by magnetic field detection and a magnetic field sensor used for the measurement.

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 to measure the conductor current I by detecting the magnetic field strength H in the surrounding space. 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) of 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, there is a disadvantage 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 r and the axial direction of the magneto-impedance effect amorphous wire is deviated from the tangent line of the circumference. is there.
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 gap in the middle of the annular magnetic core, that is, the magnetic flux passing through the magneto-impedance effect element can be made sufficiently constant, and the magnetic field strength can also be made sufficiently constant. Therefore, the conductor current measurement error 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 the influence of a slight displacement of a conductor position and a noise magnetic field by a method of detecting a magnetic field using the magneto-impedance effect, It is to enable measurement of accuracy.

  In the conductor current measuring method according to claim 1, a magneto-impedance effect element is excited by an exciting current while applying a bias magnetic field, and a detected object corresponding to a detected magnetic field is detected from a magnetic field detection signal generated by the detected magnetic field acting on the magneto-impedance effect element. The negative feedback signal based on the detected amount is negatively fed back to the negative feedback coil arranged in the vicinity of the magneto-impedance effect element to linearize the output-detected magnetic field characteristic, and the polarity can be determined by the bias magnetic field. This is a current measurement method in which a magnetic field based on a conductor current around a conductor is detected by the magnetic field detection method to measure the conductor current, and a magneto-impedance effect element piece is sandwiched around the circumference around the conductor. A plurality of magneto-impedance effect element pieces are arranged in the same direction so that the magnetosensitive direction is the same, The magneto-impedance effect element is constituted by series connection of these magneto-impedance effect element pieces, and the negative feedback coil is constituted by series connection of negative feedback coil pieces arranged in the vicinity of each magneto-impedance effect element piece. It is characterized by comprising.

  A magnetic field sensor for measuring a conductor current according to claim 2 is a magnetic field sensor used in the method for measuring a conductor current according to claim 1, wherein a plurality of magneto-impedance effects are provided on a circumference surrounding a hole of a substrate having a hole for inserting a conductor. A pair of magneto-impedance effect element pieces that have the center of the circumference are mounted in the same direction, and a negative feedback coil piece is arranged near each magneto-impedance effect element piece. A bias magnetic field coil piece is disposed in the vicinity of the element piece, and the magneto-impedance effect element piece and the negative feedback coil piece are connected in series, and an exciting current source circuit for the series-connected magneto-impedance effect element pieces is mounted. A detection circuit is provided to extract the detected amount corresponding to the detected magnetic field from the magnetic field detection signal. And wherein the are.

  A magnetic field sensor for measuring a conductor current according to claim 3 is a magnetic field sensor used in the method for measuring a conductor current according to claim 1, wherein the magneto-impedance effect element piece is disposed on one side of the substrate piece, and the other side of the substrate piece is provided. Magneto-impedance effect units, in which a bias magnetic field coil piece and a negative feedback coil piece are wound, are paired on the circumference surrounding the hole of the substrate having the conductor insertion hole, and a pair of magnetic impedances sandwiching the circumference center The effect element piece is mounted in the same direction, and the magneto-impedance effect element piece and the negative feedback coil piece of the magneto-impedance effect unit are connected in series, respectively, and an exciting current source for the series-connected magneto-impedance effect element pieces A circuit is installed, and a detection circuit for extracting the detected amount corresponding to the detected magnetic field from the magnetic field detection signal Characterized in that it is placing.

The conductor current measuring magnetic field sensor according to claim 4 is the conductor current measuring magnetic field sensor according to claim 3, wherein the magneto-impedance effect element piece is disposed on one surface of the substrate piece, and the magneto-impedance effect is provided on the other surface of the substrate piece. A magnetic impedance effect unit is used in which an iron core is arranged so as to form a loop magnetic circuit with an element piece, and a bias magnetic field coil piece and a negative feedback coil piece are wound around the iron core. It is characterized by.

  The conductor current measuring magnetic field sensor according to a fifth aspect is the conductor current measuring magnetic field sensor according to the second to fourth aspects, wherein the bias magnetic field coil pieces are connected in series.

  A magnetic field sensor for measuring a conductor current according to claim 6 is a magnetic field sensor used in the method for measuring a conductor current according to claim 1, wherein a plurality of magnets are arranged on a circumference surrounding the hole of the substrate having the hole for inserting the conductor. The magneto-impedance effect element pieces are mounted with the magnetosensitive effect direction of the pair of magneto-impedance effect element pieces that lie in the center of the circumference as the same direction, and coil pieces are disposed in the vicinity of each magneto-impedance effect element piece, An element piece and a coil piece are connected in series, and an arithmetic circuit for inputting a superimposed signal of a DC bias signal and a negative feedback signal to the series connected coil piece is provided in the negative feedback circuit. An excitation current source circuit for the strip is mounted, and the detected amount corresponding to the detected magnetic field is extracted from the magnetic field detection signal. Wherein the detection circuit for are mounted.

  A magnetic field sensor for measuring a conductor current according to a seventh aspect is characterized in that the number of magnetic impedance effect element pieces for the magnetic current sensor for measuring a conductor current according to any one of the second to sixth aspects is three or more.

  The conductor current measuring magnetic field sensor according to claim 8 is characterized in that in the conductor current measuring magnetic field sensor according to any one of claims 2 to 6, the number of magneto-impedance effect element pieces is an even number of four or more. And

  When measuring the conductor current by detecting the magnetic field based on the conductor current by the magnetic field detection method using the magneto-impedance effect, the measurement error can be sufficiently reduced even if there is some deviation in the conductor position, and the noise magnetic field such as geomagnetism. Measurement errors due to can be eliminated well.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram showing a magnetic field detection method used in the present invention. A high-frequency power source 2 for applying a high-frequency excitation current to the magneto-impedance effect element 1, a magneto-impedance effect element 1, and an axis of the magneto-impedance effect element 1 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 direction; an amplifying circuit 4 for amplifying the demodulated wave; an output terminal 5; It comprises a 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 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. 3A shows a magnetic field sensor used in the conductor current measuring method according to claim 1, that is, the conductor current measuring magnetic field sensor according to claim 2, and FIG. 3-2 is a circuit diagram of the magnetic sensor for measuring the conductor current. Is shown.
In FIG. 3A, 81 is a substrate having a conductor insertion hole 82, for example, a ceramic substrate, and 821 is a notch with respect to the conductor insertion hole 82. Reference numerals 11 to 14 denote magneto-impedance effect element pieces arranged on a circumference c surrounding the hole 82 and connected in series as shown in FIG. 3-2. The axial directions of these magneto-impedance effect element pieces 11 to 14 are directed in the tangential direction of the circumference c, and are therefore the same direction as one direction of the circumference c (the counterclockwise direction or the right-handed direction). The magneto-impedance effect element pieces 11, 13 (12, 14) are parallel to each other with the pair facing each other about the center of the circumference c.
3A and 3B, 2 is a high-frequency excitation power supply circuit, 3 is a demodulation circuit, 4 is an amplification circuit, and 5 is an output terminal. Reference numerals 61 to 64 denote negative feedback coil pieces arranged in the vicinity of the magneto-impedance effect element pieces 11 to 14, and are connected in series as shown in FIG. 3-2. Reference numerals 71 to 74 are bias magnetic field coil pieces arranged in the vicinity of the magneto-impedance effect element pieces 11 to 14, and are connected in series to the + Vcc power source in the example shown in FIG. Can be connected in parallel.

In FIG. 3-1, 9 is a straight conductor inserted through the conductor insertion hole 82 of the substrate 81 through the notch 821, and the direction of the magnetic field H generated by the conductor current is as described above according to the polarity of the conductor current. Matches the counterclockwise or clockwise direction of the circumference.
Accordingly, in FIGS. 3A and 3B, the directions of all the magneto-impedance effect element pieces 11 to 14 are made to coincide with one direction of the circumference c, and these magneto-impedance effect element pieces are connected in series. As is apparent from FIG. 3-2 in which the conductor current magnetic field H in FIG. 3A is entered, the conductor current generating magnetic field H acts on the magneto-impedance effect element pieces 11 to 14 in the same direction. The output of all the magneto-impedance effect element pieces connected in series with respect to the magnetic field H is substantially proportional to the total length of the magneto-impedance effect element pieces. 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

From this, the conductor current I can be measured.
In this case, in FIG. 3A, since a substantial portion of the circumference circuit of the circumference c where the magneto-impedance effect element pieces 11 to 14 are disposed is occupied by an amorphous magnetic material having a high magnetic conductivity, Even if the magnetic conductivity is sufficiently high and the magnetic field distribution is changed due to the displacement of the conductor 9, the magnetic flux passing through the highly conductive peripheral circuit tends to be maintained as it is, and as a result, the output variation due to the displacement of the conductor. 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, the noise magnetic field component H ₁ ′ passing through the axial center of the pair of magneto-impedance effect element pieces 11 and 13 (12, 14) sandwiching the circumference center with respect to the noise magnetic field H ′. , H ₃ ′ (H ₂ ′, H ₄ ′) are opposite to the axial direction of the magneto-impedance effect element pieces 11, 13 (12, 14), and the magneto-impedance effect element pieces 11, 13 (12, 14). ) Is equal to the noise magnetic field H ′ at the axis, and H ₁ ′ and H ₃ ′ (H ₂ ′ and H ₄ ′) are detected magnetic fields of opposite signs having the same magnitude [± H ₁₃ ( ± H ₂₄₎ next], in (d) of the output 2, for _{± E '13 (± E'} 24) next to the polarity discrimination can output characteristics, will be canceled and the output thereof to one another, not output . Accordingly, it is possible to measure the conductor current with sufficiently high accuracy by eliminating the influence of the noise magnetic field.

In the present invention, it is desirable that the number of magneto-impedance effect element pieces is (a pair with the circumference center) × n, that is, an even number.
In the case of an odd number, the number of magnetoimpedance effect element pieces corresponding to one of [(a pair that rubs the center of the circumference) × n + 1] in the case of [(a pair that holds the center of the circumference) × n + 1] Only an output for a noise magnetic field component acting in the axial direction appears, and even in the case of an odd number, it is sufficiently effective when n is large.

In the present invention, the arrangement intervals of the magneto-impedance effect element pieces on the circumference are set to be equal intervals or to be as narrow as possible in order to stably maintain the magnetic field by the above-described magnetic conducting core. It is effective.
In the present invention, the serial connection of the magneto-impedance effect element pieces may be any connection so long as the sum of the outputs of the magneto-impedance effect element pieces is obtained. For example, the output of the magneto-impedance effect element pieces is used as the detection impedance. It is also possible to provide a detection end for collecting and taking out the detected impedance voltage.

In the present invention, it is preferable to unitize the magneto-impedance effect element piece, the negative feedback coil piece, and the bias magnetic field coil piece to reduce the size of the sensor body.
4A is a side view showing an example of the magneto-impedance effect unit used in the present invention, FIG. 4B is a bottom view, and FIG. 4C is a side view in FIG. -It is C sectional drawing.
In FIG. 4, 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 100 and includes an element piece 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 piece connected between the protrusions 102 and 102 of the electrodes 101 and 101 by soldering or welding, and the above-described zero magnetostriction or negative magnetostriction amorphous wire, amorphous ribbon, sputtered film, etc. can be used. . 103 is a C-shaped iron core, 6x is a negative feedback magnetic field generating coil piece wound around the C-shaped iron core 103, 7x is also a bias magnetic field coil piece (both are usually coated with an insulating paint on a copper wire) And the both ends of the C-shaped iron core 103 are bonded to the other surface of the substrate piece 100 so that the magneto-impedance effect element piece 1x and the C-shaped iron core 103 constitute a loop magnetic circuit. It is fixed with agents.
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-shaped 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-shaped iron core is

R _a = l _a / (S _a μ _a )

In addition, if the length of the magneto-impedance effect element piece portion constituting the magnetic circuit is 1 _b , the cross-sectional area is S _b , and the magnetic permeability is μ _b , the magnetoresistance of the magneto-impedance effect element piece portion R _b is

R _b = l _b / (S _b μ _b )

Further, if the magnetic resistance between the both ends of the C-shaped iron core and the magneto-impedance effect element piece 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

And the self-inductance L ₂ of the bias magnetic field coil piece is 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 piece 100, The length of C Katachitetsushin Suffice the height of the legs of the C Katachitetsushin enough to slightly higher than the diameter of the winding since the possible short, a 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.
In order to configure a magnetic current sensor for measuring a conductor current according to claim 4 using this magnetoimpedance effect unit, the above-described magnetoimpedance effect units U _{1 to} U ₄ have conductor insertion holes 82 as shown in FIG. A plurality of pairs of magneto-impedance effect element pieces sandwiching the center of the circumference are mounted on the circumference surrounding the hole 82 of the substrate 81 as the same direction, and the magnetism of the magneto-impedance effect units U _{1 to} U ₄ is mounted. The impedance effect element piece and the negative feedback coil piece are connected in series, and the excitation current source circuit 2 for the series-connected magnetoimpedance effect element pieces is mounted to extract the detected amount corresponding to the detected magnetic field from the magnetic field detection signal. The demodulating circuit 3 and the amplifying circuit 4 are mounted, and in the same manner as described above, a negative feedback coil piece is connected through a series-connected negative feedback coil piece. Is applied, the bias magnetic field is applied by the bias magnetic field coil, the polarity discrimination can linear output shown in FIG. 2 (d) is adjusted so as to obtain.
When mounting this magneto-impedance effect unit on a substrate, in order to mechanically protect the magneto-impedance effect element piece, the unit's magneto-impedance effect element side is directed to the substrate, and the unit substrate piece is fixed to the substrate with an adhesive. Is desirable.
In FIG. 5, the magnetoresistance Rw of the magneto-impedance effect unit with respect to the conductor current magnetic field H is represented by R _{a as} the magnetoresistance of the C-shaped iron core, and R _b as the magnetoresistance of the magneto-impedance effect element piece portion.

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

Since the magnetic resistance _Rb can be made lower than the magnetoresistive element _{Rb of the} single element of the magneto-impedance effect element, the magnetic conductivity of the peripheral circuit c can be further increased, and the conductor current can be measured by further stabilizing the distribution state of the detected magnetic field H. The accuracy can be improved.

  As another example of the magneto-impedance effect unit, a magneto-impedance effect element piece is arranged on one side of an insulating base plate piece, and a negative feedback coil piece and a bias magnetic field coil piece are printed on the other side of the insulating base plate piece. What was provided can be mentioned.

  In the present invention, a normal high frequency such as a continuous sine wave, a pulse wave, or a triangular wave can be used as the high frequency excitation current. Examples of the high frequency excitation current source include a Hartley oscillation circuit, a Colpitts oscillation circuit, a collector tuning oscillation circuit, and a base tuning oscillation. In addition to a normal oscillation circuit such as an oscillation circuit, a rectangular wave generator that integrates the square wave output of a crystal oscillator through an integration circuit via a DC cut capacitor and amplifies the triangular wave of this integration output by an amplification circuit, and oscillates a CMOS-IC The triangular wave generator etc. which were used as a part can be used.

In the present invention, for example, the demodulating circuit has a configuration in which a modulated wave is half-wave rectified by an operational amplifier circuit 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, A configuration in which the modulated wave is half-wave rectified with a diode and the half-wave rectified wave is processed with 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, but a single coil piece is disposed in the vicinity of each magneto-impedance effect element piece, as shown in FIG. The impedance effect element pieces 11 to 14 are connected in series, the single coil pieces 671 to 674 described above are connected in series, and the superimposed signal of the DC bias signal and the negative feedback signal is connected in series by the arithmetic circuit Q to the coil 671. To 674 to obtain a linear output characteristic capable of discriminating the polarity as shown in FIG.
In the example of FIG. 6, an operational amplifier (negative feedback path insertion impedance Z ₂ , input side insertion impedance Z ₁ ) in which negative feedback is 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 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 the figure can be obtained by adjusting the zero point in the y-axis direction.

  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 the magnetic field measuring method 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 magnetic field sensor for conductor current measurement which concerns on Claim 2. FIG. 3 is a circuit diagram of the magnetic field sensor for measuring a conductor current of FIG. 3-1. It is drawing which shows an example of the magneto-impedance effect unit used for the magnetic field sensor for conductor current measurement concerning Claim 3. It is drawing which shows the Example of the magnetic field sensor for conductor current measurement which concerns on Claim 3. It is drawing which shows the circuit diagram of the Example of the magnetic field sensor for conductor current measurement which concerns on Claim 5.

Explanation of symbols

11-14 Magnetic impedance effect element piece 2 High frequency excitation current source 3 Demodulation circuit 4 Amplification circuit 61-64 Negative feedback coil pieces 71-74 Bias magnetic field coil piece 81 Substrate 82 Conductor insertion hole 9 Conductor

Claims (8)

The magneto-impedance effect element is excited by an excitation current while applying a bias magnetic field, and the detected amount corresponding to the detected magnetic field is extracted from the magnetic field detection signal generated by the detected magnetic field acting on the magneto-impedance effect element and arranged near the magneto-impedance effect element. A negative feedback signal based on the detected amount is negatively fed back to a negative feedback coil provided to linearize the output-detected magnetic field characteristics and to determine the polarity by the bias magnetic field. Is a current measurement method for detecting a magnetic field based on a magnetic field and measuring a conductor current of the magnetic impedance effect element piece on a circumference surrounding the conductor, and a magnetosensitive effect direction of a pair of magnetoimpedance effect element pieces sandwiching the circumference center Are arranged in the same direction, and these magneto-impedance effect elements are arranged. The magneto-impedance effect element is configured by serial connection of the magnetic feedback effect elements, and the negative feedback coil is configured by serial connection of the negative feedback coil pieces disposed in the vicinity of the magneto-impedance effect element pieces. Conductor current measurement method. 2. A magnetic field detection sensor used in the conductor current measuring method according to claim 1, wherein a plurality of magneto-impedance effect element pieces sandwich the center of the circumference on a circumference of the board having a conductor insertion hole. The magneto-impedance effect element pieces are mounted in the same direction, a negative feedback coil piece is disposed in the vicinity of each magneto-impedance effect element piece, and a bias magnetic field coil piece in the vicinity of each magneto-impedance effect element piece The magneto-impedance effect element piece and the negative feedback coil piece are connected in series, and an excitation current source circuit for the series-connected magneto-impedance effect element piece is mounted to convert the magnetic field detection signal into the detected magnetic field. A conductor circuit equipped with a detection circuit for extracting the corresponding detected amount Measurement for magnetic field sensor. A magnetic field sensor used in the conductor current measuring method according to claim 1, wherein the magneto-impedance effect element piece is disposed on one side of the substrate piece, and a bias magnetic field coil piece and a negative feedback coil piece are provided on the other side of the substrate piece. The installed magneto-impedance effect unit is mounted on the circumference surrounding the hole of the board having the conductor insertion hole, and the magneto-sensitive direction of the pair of magneto-impedance effect element pieces surrounding the circumference center is mounted in the same direction. The magneto-impedance effect element piece and the negative feedback coil piece of the magneto-impedance effect unit are connected in series, and an excitation current source circuit for the series-connected magneto-impedance effect element pieces is mounted, and the detected magnetic field is detected from the magnetic field detection signal. Conductor current, which is equipped with a detection circuit to extract the detected amount equivalent to Titration, the magnetic field sensor. A magneto-impedance effect element piece is disposed on one surface of the 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 magneto-impedance effect element piece. 4. A magnetic sensor for measuring a conductor current according to claim 3, wherein a magneto-impedance effect unit in which a coil piece and a negative feedback coil piece are wound is used. 5. The magnetic field sensor for measuring a conductor current according to claim 2, wherein the bias magnetic field coil pieces are connected in series. A magnetic field sensor used in the conductor current measuring method according to claim 1, wherein a plurality of magneto-impedance effect element pieces are sandwiched around the circumference of the circumference of the board having the conductor insertion hole. The magneto-impedance effect element pieces are mounted in the same direction. Coil pieces are disposed in the vicinity of the magneto-impedance effect element pieces, and the magneto-impedance effect element pieces and the coil pieces are connected in series. An arithmetic circuit for inputting a DC bias signal and a negative feedback signal superimposed signal to the series connection coil piece is provided in the negative feedback circuit, and an exciting current source circuit for the magneto-impedance effect element piece connected in series is mounted, and a magnetic field detection signal is provided. It is equipped with a detection circuit to extract the detected amount corresponding to the detected magnetic field from Conductor current measurement magnetic field sensor. The magnetic field sensor for measuring a conductor current according to any one of claims 2 to 6, wherein the number of magneto-impedance effect element pieces is three or more. The magnetic field sensor for measuring a conductor current according to any one of claims 2 to 6, wherein the number of magneto-impedance effect element pieces is an even number of 4 or more.

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