JPH083499B2 - Current detector - Google Patents

Description

Detailed Description [Table of Contents] Outline Industrial field of application Conventional technology Problems to be solved by the invention Means for solving problems Problems Working Example First Working Example Second Working Example Third Working Example -Embodiment 10 Effect of the Invention [Outline] In order to obtain a small-sized current detector applicable to both AC and DC, the present invention applies a current to a conductor wire close to a pair of magnetoelectric conversion elements, It is a current detector that differentially synthesizes outputs with each other to easily detect a current value.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detector that detects a current value by changing the strength of a magnetic field generated when a current flows.

Conventional current detectors often require dedicated ones for DC and AC, and are relatively large. Especially for direct current, it was requested to develop a small insulated current detector.

[Prior Art] A transformer is used as the simplest means for isolating an ammeter from a measurement system for AC current measurement.
At this time, the commercial frequency device is about the size of a child's fist, even if it is small, and the frequency characteristics greatly affect the operation of the transformer.

In addition, a differential type current transformer is used in the leakage sensor. FIG. 21 is a diagram showing a schematic configuration in that case.Currents I ₁ and I ₂ flowing in the center of the ring-shaped yoke generate a magnetic flux in the high μ yoke, and the change over time is observed from the coil wound around the yoke. I am taking it out. Since the currents I ₁ and I ₂ are in opposite directions, only magnetic flux is generated by the difference current, and the sensitivity is good.

In DC measurement, the voltage drop across the standard resistance is measured with a DC potentiometer. A shunt meter is used for large currents.

It is also possible to measure the direct current using the Hall effect of the semiconductor.

A magnetic field generated by an electric current can be detected by using a magnetoresistive element, which is known from Japanese Patent Laid-Open No. 59-79860. As shown in FIG. 22, the substrate 5 provided with the magnetic metal film 2 on its surface is placed at a position slightly separated from the electric wire 1. The magnetic metal film 2 is formed of nickel-iron alloy or the like, and terminals 3 and 4 are provided on both ends of the substrate in the longitudinal direction. The substrate 5 uses an electrically insulating material such as ceramic. A magnetic core (yoke) 6 is provided between the terminals 3 and 4, and the magnetic core 6 and the magnetic metal film 2 constitute a magnetic loop 7. The magnetic field generated when a direct current flows through the electric wire 1 forms a magnetic loop 7 via the magnetic core 6 and the resistance value between the terminals 3 and 4 of the magnetic metal film 2 changes. The current value can be obtained.

A movable iron piece type / ammeter type can be used for both AC and DC.

[Problems to be Solved by the Invention] When measuring an alternating current using a transformer, it was difficult to reduce the size. In addition, since the transformer has an inductance component, it is difficult to measure accurately with a current having many high frequency components such as a pulse current.

In the case of an earth leakage sensor, a working current and an annular core of a size suitable for it are required, and the applicable range is not so wide.

When a direct current is measured using a resistance element, there is unnecessary power consumption in the resistance element, and it is necessary to select and use a current value, a resistance value of the resistance element, and a DC potentiometer each time. At this time, if an unwanted signal is mixed in the current circuit,
It directly affects the measurement. In general, there has been no small device capable of detecting by isolating a conducting wire through which a direct current flows from a detector.

Furthermore, when using a Hall effect element, there is a drawback that the device becomes large because a yoke that eliminates the influence of an external magnetic field is used.Since it is a configuration that measures the magnetic field, a means for eliminating the influence of the earth's magnetism is required. The device became complicated and large as a detector.

Further, in the known technology described in the above-mentioned patent publication,
Since a magnetic core having a shape surrounding an electric wire is provided between both terminals of the magnetic metal film 2, it is necessary to use a large component.
When an external magnetic field other than the magnetic field generated by the wire acts, its effect is detected in proportion to the reciprocal of μ determined by the material of the magnetic core, so in order to avoid the effect of the external magnetic field, use a magnetic core with a large μ. There was a drawback that it was necessary and expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly accurate current detector capable of improving the above-mentioned drawbacks and capable of high-speed response from direct current to high frequency alternating current with a simple and compact structure.

[Means for Solving the Problems] FIG. 1 is a diagram showing the principle configuration of the present invention. In FIG. 1, 11 is a direct conductor wire, 12 is a current flowing through the conductor wire, 13 is a magnetic loop showing a magnetic field generated concentrically around the conductor wire 11 when a current 12 flows through the conductor wire 11, 14,1
Reference numeral 5 denotes a magnetoelectric conversion element, 16 a combining portion, 17 a disturbance magnetic field given from the outside, 18 a substrate, and 19 a through hole.

In order to achieve the above-mentioned object, the present invention provides a conductor 11 through which a current 12 to be measured flows, and a magnetic field 13 generated around the conductor 11 when the current 12 to be measured flows through the conductor 11. The magnetoelectric conversion elements 14 and 15 that perform the magnetoelectric conversion in the facing region and the combining unit 16 that combines the magnetoelectric conversion outputs of the respective magnetoelectric conversion elements 14 and 15 are formed.
The conductor wire 11 is passed through a through hole 19 provided on the substrate 18 at a predetermined position of the substrate 18.

[Operation] The magnetoelectric conversion elements 14 and 15 shown in FIG. 1 have the same characteristics, and the magnetic loop 13 generated when a current 12 flows through the conductor 11
On the other hand, they are receiving magnetic fields in the same direction but in different directions. Therefore, the outputs extracted from the elements 14 and 15 have opposite phases, and when differentially combined in the combining section 16, the output of the combining section 16 is approximately twice the output of the element alone. On the other hand, when the external magnetic field 17 affects the entire current detector, the outputs of the magnetoelectric conversion elements 14 and 15 are in phase with the external magnetic field 17. Therefore, the output signal based on the external magnetic field 17 is canceled by the differentially combined output in the combining unit 16.

At this time, the effect of canceling the external magnetic field can be similarly obtained by one element in which the magnetoelectric conversion elements 14 and 15 are formed in a common pattern.

Example A Hall effect element or a magnetoresistive element can be used as the magnetoelectric conversion element used in the present invention.
In particular, a detector provided with a barber pole type magnetoresistive element on a substrate is effective in operation.

First Embodiment As an embodiment of the present invention, it is constructed as shown in an explanatory view of FIG. 2, and more specifically, a magnetoresistive element is provided on a substrate as a barber pole type pattern as shown in FIG. FIG. 4 is a cross sectional view of FIG. 3, FIG. 5 is an enlarged view of part A in FIG. 3, and FIG. 6 is an enlarged view of part B in FIG. FIG. 7 is a diagram showing a modification of the pattern shown in FIG. The whole detector including the conductor is constructed as shown in FIG. The first embodiment of the present invention and its modifications will be described below in the order of the drawings.

In the explanatory view shown in FIG. 2, the magnetoresistive elements 14-1, 14
-2 and 15-1 and 15-2 are examples of paired magnetoresistive elements. A barber pole type is suitable as the magnetoresistive element, and each element is brought into contact with the bridge, the details of which will be described later. Further, 18 is a glass or silicon substrate, and 19 is a through hole, which is punched in the central portion of each magnetoresistive element and through which the conducting wire 11 passes. Reference numeral 20 is a constant current source for supplying a constant current from one diagonal apex of the bridge of the magnetoresistive element, and 21 is a circuit for differentially combining the outputs taken out from the other diagonal apex of the bridge by an operational amplifier. Reference numerals 14-3 and 15-3 indicate those for compensating for some variations generated in the four elements 14-1 to 15-2 when the magnetoresistive element is formed on the substrate 18 by vapor deposition or the like with a trimming pattern. . When a current flows through the lead wire 11 as shown by the arrow 12 in FIG. 2, the generated magnetic field affects the magnetoresistive elements 14-1 and 14-2, 15-1 and 15-2 in the opposite directions, and the resistance value changes. give. Therefore, the constant current from the constant current source 20 applied between the diagonal vertices of one of the bridge-connected elements changes, and the outputs extracted from between the other diagonal vertices are differentially combined by the operational amplifier 21. Therefore, if the change in the strength of the magnetic field and the output voltage of the operational amplifier 21 are calibrated in advance, the current value can be immediately obtained from the output voltage value of the operational amplifier 21.

When an alternating current flows through the conductor 11, a change in the magnetic field strength corresponding to the alternating current peak value can be taken out from between the other diagonal vertices of the bridge.

Next, the pattern of the substrate and the magnetoresistive element on the substrate shown in FIG. 3 will be described. This pattern is suitable as an embodiment of the present invention. FIG. 3 is a top view, and FIG. 4 is a cross sectional view taken along the chain line IV-IV in FIG. 3 and seen in the direction of the arrow. Show. The cross-sectional view is drawn with the vertical direction enlarged as compared with the horizontal direction for easy understanding. In Fig. 3, 22-
Reference numerals 1 to 22-4 denote bonding pads for resistance elements, which are also connected to the diagonal vertices of the bridge connection. Other than that, the same reference numerals as those in FIG. 2 indicate the same parts. The serpentine barber pole type magnetoresistive element pattern itself shown in FIGS. 3 and 4 is formed by a known technique. That is, an insulating layer 23 such as silicon dioxide formed on a substrate 18 such as silicon.
A magnetic thin film 24 such as an iron-nickel alloy (permalloy) is adhered and formed on the above, and then patterned by a lithography technique to form a zigzag magnetic thin film 24. In FIGS. 3 and 4, the folded portion (circumferential length) is different between the side closer to the through hole 19 through which the conductor wire 11 penetrates and the side farther from it. That is, although an enlarged view of the portion A in FIG. 3 is shown in FIG. 5, the strip-shaped portion of the permalloy 24 is closer to the side closer to the through hole 19. The situation is shown in FIG. 6 as an enlarged view of part B in FIG. The dashed-dotted line in FIG. 6 is a straight line drawn from the through hole 19, and the magnetic thin film 24 is further inclined by a predetermined angle α with respect to the straight line. The pattern is formed symmetrically with respect to the center of the through hole 19 as a whole. The description will be given later.

Including FIG. 5 and FIG. 6, uniaxial anisotropy is given to the magnetic thin ribbon 24 of permalloy in the direction away from the through hole 19, and then the conductive strip 26 is provided through the adhesion layer 25 (tantalum molybdenum TaMo or chromium). (For example, gold) is obliquely attached at regular intervals. The width w of the conductive band 26 is, for example, 4.24 μ, and the gap G is 5.
66 μ, the width ω of the permalloy 24 is about 16 μ, and the size of the pattern is such that one side can be placed on a substrate of about 5 mm. The directions of the conductive bands 26 are different from each other on the adjacent bridge sides, and are inclined by about 45 degrees with respect to the lines drawn from the through holes. A protective film 27 is attached to the upper surface of the conductive band 26. Also a pad for bonding
22-1 to 22-4 are provided with lead patterns 28 for connection at four positions as shown in FIG.

Next, the permalloy pattern shown in FIG. 6 will be described. Since the permalloy portion in FIG. 6 has only shape anisotropy when it is vapor-deposited on the substrate, it gives induced anisotropy if a large current is passed through the conductor after vapor deposition.
Since the magnetic field Hi obtained by the current acts in the direction shown in the figure with respect to the permalloy, if the permalloy is orthogonal to the Hi, the component force of the Hi does not remain in the left direction in the figure. Therefore, if the side line 29 forming the permalloy pattern is inclined by α (for example, several degrees) with respect to the line 30 drawn out from the through hole and about 800 Oe is given as Hi, a magnetic field component Hp of 4 to 5 Oe remains in the permalloy and induces anisotropy. Gender is given. Note that the barber pole type inclined by 45 degrees in this way is convenient because it is possible to obtain a magnetoelectric conversion output proportional to the external magnetic field without using a bias magnetic field.

Through holes 19 are drilled before permalloy is deposited on the substrate 18. Spaces corresponding to the size of the substrate when it is used as a current detector by micromachining technology, for example, diamond-shaped holes with a side of 0.5 mm for every 5 mm, on a [1,1,0] surface of a silicon substrate. Good to wear.

FIG. 7 is a view showing a modification of the pattern of the magnetic thin film such as permalloy, and is an enlarged view of the C portion in FIG. Of course, the pattern formed by the magnetic thin film covers the entire portion including the C portion. In the pattern shown in FIG. 3, the magnetic thin film 24 is formed with the same pattern width on the side close to the through hole 19 and on the side far from the through hole 19, and has a zigzag shape.
In the case of FIG. 7, the pattern width ω of the magnetic thin film 24 becomes wider as the distance from the through hole 19 increases. At this time, the width W and the gap G of the conductive band 26 shown by hatching are constant, and are inclined by about 45 degrees with respect to the radial line from the through hole 19, as in the case of FIG. Therefore, the conductive band 26 on the magnetic thin film 24 increases in length when it is separated from the through hole 19. With this pattern, the magnetic thin film separated from the through hole 19 receives a smaller magnetic field, but the pattern length is increased to increase the magnetoelectrically converted output, and a substantially uniform electric output is obtained from the entire surface of the magnetic resistance pattern.

Then, a modularized current detector is constructed as shown in FIG. In FIG. 8, the lead frame 30 serves as a terminal for connection with a differential synthesizing circuit or the like, and the lead frame 31 is used for coupling the substrate 18 and the exterior 32. Lead wire
It is sufficient to read the change in resistance value of the magnetoresistive element when the current to be measured is caused to flow through the through hole 19 of the substrate 18.

Second Embodiment FIG. 9 is an explanatory diagram of the second embodiment of the present invention.
FIG. 10 is a diagram showing a magnetoresistive element pattern in the second embodiment. Reference numerals 11 to 20 in FIG. 3 are the same as those in FIG. In FIG. 9, each magnetoresistive element 14,15
Are arranged so as to be present in the area facing the periphery of the conductor 11, and are combined so that the magnetoelectric conversion outputs of the respective elements are connected in series. That is, since the resistance elements 14 and 15 are connected in series to the constant current source 20 and the voltage across the constant current source 20 is taken out, no special component is required as a combining unit.

FIG. 10 shows a magnetoresistive element pattern embodying the configuration of FIG. Fig. 10 shows a barber pole type magnetoresistive element 1
4, 15 are arranged symmetrically with respect to the through hole 19, and the direction of initial magnetization is determined as indicated by a thick arrow. All thick arrows indicate the direction of gathering in the through holes 19 or the direction of going away. A constant current source is connected to the bonding pads 22-1 and 22-2 shown in FIG. 10 and is connected to an amplifier circuit or the like. First
The pattern shown in FIG. 10 has the same value even if the width ω of the magnetic thin film (permalloy) goes away from the through hole 19 as shown in FIG. 5, and has a slight inclination as shown in FIG. Alternatively, it is also possible to adopt a configuration in which ω is changed as shown in FIG.

Further, when the second embodiment is viewed as an overall view, it can have the same configuration as that of FIG.

The configuration of the second embodiment has a feature that the resistance element pattern is easily manufactured as compared with the configuration of the first embodiment.

Third Embodiment Since the following description of the embodiment is made by emphasizing only the characteristic part of the first embodiment and the description of the second embodiment, the first embodiment or the second embodiment will be described. The description of the same parts as is omitted.

FIG. 11 shows a detector as a third embodiment of the present invention when a multi-phase alternating current is applied to the conductor. In FIG. 11, the lead wire that penetrates the through hole of the substrate 18 is a coaxial type 33. FIG. 11A shows a two-layer coaxial wire 33-1 used in the case of two-phase alternating current,
FIG. 11B shows a three-layer coaxial cable 33-2 used in the case of three-phase alternating current. In the case of the two-layer coaxial line 33-1, the same operation as in FIG. 2 is performed, but in the case of the three-layer coaxial line 33-2, there are currents that cancel each other due to the relationship of each AC phase, and no magnetic field is generated in the surroundings. Therefore, when it is used as a leakage detection sensor, it is possible to detect the existence of different flows for each phase, which is effective as a leakage detection sensor for the alternating current of the first current.

Fourth Embodiment FIG. 12 shows a fourth embodiment of the present invention in which the conductor wire 11 is placed in parallel with the surface of the magnetoresistive element with a very small distance between them, and FIG. 12A is a plan view and FIG. B is a side view. The pattern of the magnetoresistive elements 14-1 to 15-3 is preferably formed in parallel with the conductor wire 11, and as a place to place the conductor wire 11,
The vicinity of the center of the magnetoresistive element pattern is good. In FIG. 12B, a graph of the relationship between the current flowing in the conductor and the output of the differential amplifier circuit is measured for the same magnetoresistive element as in FIG. Show. In FIG. 12C, the horizontal axis represents the measured current of the conducting wire, and at 1.0 A, a magnetic field of about 5.6 Oe was obtained for the magnetoresistive element, and the bridge output was 0.4 V, for example. The bridge output was about 0.2 V when a current of 0.5 A was applied to the conductor.

Fifth Embodiment FIG. 13 is a diagram showing a fifth embodiment of the present invention. FIG. 13 is a plan view showing a case where the conducting wire is on the coil on the surface of the magnetoresistive element. Since a plurality of routes of electric current are passed in parallel with the longitudinal direction of the conductor, the change in the magnetic field applied to the magnetoresistive element is larger than that in the case of a single conductor. Even if a plane conductor is used instead of the coil-shaped conductor, there is an effect that the detection efficiency of the magnetic field is improved as compared with the case of a single conductor.

Sixth Embodiment FIG. 14 is a diagram showing a sixth embodiment of the present invention, showing a case where two sets of magnetoresistive element bridges having substantially the same operating characteristics are opposed to each other, and a conducting wire 11 through which a current flows is placed between them. ing. First
In Fig. 14, 21 is a differential amplifier, 34 and 35 are bridge-connected barber pole type magnetoresistive elements, and 36 and 37, respectively.
Shows an operation circuit for each resistance element. The output of one operation circuit 36 and the output of the other operation circuit 37 are differentially taken out by the differential amplifier circuit 21. As a result, the outputs of the bridges 34 and 35 act differentially with respect to the current of the conductor 11, so that differential amplification of them will eventually result in addition. Therefore, compared to the case where a single bridge is used, approximately twice the output can be obtained, while the external magnetic field and other disturbance magnetic fields have the same amount of influence on each bridge output, so differential amplification cancels it. To be done. That is, the signal-to-noise ratio is remarkably improved.

Seventh Embodiment FIG. 15 is a diagram showing a seventh embodiment of the present invention. In FIG. 15, reference numeral 38 denotes a magnetoresistive element bridge, which is different from the bridge 34 in its saturation magnetic field Hd, for example, a larger one,
Those provided separately on the front and back of the substrate 18 are shown. Here, the saturation magnetic field Hd means the value shown in FIG. That is, in FIG. 16, when the strength of the magnetic field applied to the magnetoresistive element bridge is plotted on the horizontal axis and the change in resistance value ΔR / R is plotted on the vertical axis, an S-shaped curve passing through the origin is obtained. When the strength of the magnetic field is changed, the S-shaped curve is not constant and changes like 34S and 38S depending on the element. The reason is that there are differences in the width and film thickness of the magnetic film pattern. When the applied magnetic field is larger than a predetermined value, there is a point where the resistance value changes from positive to negative, and the magnitude of the magnetic field at that time is called the saturation magnetic field Hd.
An element with a small saturation magnetic field Hd is suitable for detecting a small current, and an element with a large Hd is suitable for detecting a large current. Therefore, when the current amount is slightly changed at the beginning of the operation of the current detector, the resistance change is larger. One, for example 38, is operated as it is, and the one with a smaller resistance change is placed with the output terminal disconnected. When detecting a large current, the used magnetoresistive element bridge should be switched from 38 to 34.

Eighth Embodiment FIG. 17 is a diagram showing an eighth embodiment of the present invention, in which the saturation magnetic field Hd of the magnetoresistive element bridge is gradually increased, and the substrate through which the current conducting wire passes is , 38,39,40 ……
As shown in the above, they are arranged side by side in a beaded shape and are sequentially switched depending on the magnitude of the detected current. As a result, even if the range of the current to be detected is large and small, it is possible to cope with it.

Ninth Embodiment FIG. 18 is a diagram showing the configuration of the ninth embodiment of the present invention, showing a case where a plurality of magnetoresistive element bridges are arranged in a donut annular shape. At this time, the saturation magnetic field Hd of each bridge may be the same or different. Since the magnetic field generated by the current conducting wire 11 becomes weaker around the substrate 18, each bridge is switched and used depending on the magnitude of the current. A configuration in which the saturation magnetic field Hd gradually decreases on the outer circumference is suitable for operation.

10th Embodiment FIG. 19 is a diagram showing the structure of a 10th embodiment of the present invention, in which a magnetoresistive element forming a bridge is divided into a fan shape from a through hole through which a current conducting wire passes, and the magnetic fields on the respective sides of the bridge are staggered. It constitutes a resistance element. For example, 14-1a, 14-2a, 15-1a, 15
-2a bridge and 14-1b, 14-2b, 15-1b, 15
A bridge composed of −2b. Since two sets of separate bridges are formed on the substrate 18, this is effective when the bridges have different saturation magnetic fields Hd. Further, the number of bridge sets can be increased.

○ Eleventh embodiment Figure 20 is a diagram showing the configuration of the eleventh embodiment of the present invention, a substrate 18 including a magnetoresistive element and a portion of the current conductor 11 in a shield case 41 of high permeability such as iron. This is the case when stored.
According to this embodiment, it is possible to prevent the saturation magnetic field of the magnetoresistive element from being substantially reduced by the external magnetic field.

[Effects of the Invention] As described above, according to the present invention, since two magnetoelectric conversion elements are arranged in pairs symmetrically with respect to a linear conductor, a change in magnetic field strength based on a current flowing through the conductor is suppressed. The proportional change in the output value of the magnetoelectric conversion element can be effectively taken out to facilitate the current detection. In addition, since it is possible to change the output value of the magnetoelectric conversion element for alternating current as in the case of direct current, it is possible to detect current even for high frequency alternating current or pulse waveforms with a frequency of 1 NHz or more. .

[Brief description of drawings]

FIG. 1 is a diagram showing the principle configuration of the present invention, FIGS. 2 to 8 are diagrams showing the configuration and a partially enlarged view of the first embodiment of the present invention, and FIGS. 9 and 10 are the present invention. Of the second embodiment of the present invention, an illustration of its configuration and an element pattern, FIGS. 11 to 15 are diagrams showing the configurations of the third to seventh embodiments of the present invention, and FIG. 16 is a saturation magnetic field. 17 to 20 are diagrams showing the configurations of the eighth to eleventh embodiments of the present invention, and FIG. 21 is a diagram showing a configuration example of a conventional earth leakage sensor. The figure is a diagram showing the configuration of a conventional current detector using a single magnetoresistive element. 11 …… Current conductor, 13 …… Magnetic loop 14,15 …… Magnetic conversion element 16 …… Composite, 17 …… External magnetic field 18 …… Board, 19 …… Through hole 20 …… Constant current source 34,35, 38, 39, 49 …… Magnetoresistive element bridge 36, 37 …… Operating circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michiko Endo 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Yuji Ojima 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited ( 72) Inventor Akira Tanaka 1015 Kamiodanaka, Nakahara-ku, Kawasaki, Kanagawa, Fujitsu Limited (72) Inventor Hideaki Yoda 1015, Kamikodanaka, Nakahara-ku, Kawasaki, Kanagawa Fujitsu Limited (56) References JP 57 -128854 (JP, A)

Claims (14)

[Claims] 1. A conductor wire (11) through which a current to be measured (12) flows, and a magnetic field (13) generated around the conductor wire (11) when the current to be measured (12) flows through the conductor wire (11). ) Is magnetoelectrically converted in the area facing the periphery of the conducting wire (11).
(15) and the magnetoelectric conversion element (14) (15) are arranged on a substrate (18), and a through hole (1) provided at a predetermined position of the substrate (18).
A current detector characterized by comprising a conductor (11) penetrating through 9), and a synthesizing section (16) for synthesizing respective magnetoelectric conversion outputs. 2. A magnetoresistive element is used as the magnetoelectric conversion element (14) (15), and the magnetoresistive element includes a zigzag-shaped magnetic thin film (24) formed in an arc shape on the circumference of a conductor. A barber pole type magnetoresistive element pattern having a conductive band (26) obliquely attached to a magnetic thin film (24), the pattern being arranged in the longitudinal direction of the conductor (11) so as to surround the conductor (11). The current detector according to claim 1, wherein the current detector is arranged in a vertical plane. 3. A plurality of sets of magnetoresistive elements are formed into a barber pole type and are bridge-connected, and when a voltage is applied to one diagonal apex of the bridge, an output from an output terminal connected to the other diagonal apex is output. The current detector according to claim 1, wherein the current detector is applied to a differential amplifier circuit. 4. A barber pole type magnetoresistive element is symmetrical with respect to a conducting wire (11) passing through a through hole (19) provided in a substrate (18) and has a radial shape centered on the through hole (19). The line (30) extending in the peripheral direction by being drawn out from the through hole (19) and the side line (29) forming the pattern are inclined at a predetermined angle. The current detector according to any one of items 1 to 3. 5. The barber pole type magnetoresistive element is formed in a radial pattern centered on the through hole, and the width of the magnetoresistive element is not changed by the distance from the through hole. The current detector according to the item. 6. The barber pole type magnetoresistive element is formed in a radial pattern centered on the through hole, and the width of the magnetoresistive element is changed by the distance from the through hole. The current detector according to the item. 7. A magnetoresistive element is formed around a through hole (19) perforated on a silicon substrate (18) by a micromachining technique, as claimed in any one of claims 1 to 6. The current detector according to claim 1. 8. A pulse current for obtaining a magnetic field required for initial magnetization for a pattern forming a magnetoresistive element is passed through the conducting wire (11) or an external magnetic field is applied so that the initial magnetization direction is outward from the through hole. The current detector according to any one of claims 1 to 4, wherein the current detector is directed toward the through hole or the through hole. 9. A magnetoresistive element, wherein a plurality of elements having different saturation magnetic field characteristics are used, and an element corresponding to a current strength of a current conducting wire commonly affecting each element is selected and used. The current detector according to claim 1. 10. The current detector according to claim 1, wherein the magnetoresistive element is formed in a donut ring shape having different radii from the through hole on the substrate in the outer peripheral direction. 11. The current detector according to claim 1, wherein the magnetoresistive element is formed on the substrate in the direction perpendicular to the conducting wire and in parallel with each other. 12. The current detector according to claim 1, wherein the conducting wire for passing a current is a multilayer coaxial wire. 13. The current detector according to claim 1, wherein the conducting wire for passing a current is arranged in a folded coil shape outside the outer periphery of the substrate. 14. A magnetic conversion element and a synthesizing circuit housed in a shield case.
The current detector according to the item.