CN103123369A - Current sensing device - Google Patents

Abstract

The invention discloses a current induction device, which comprises a magnetic field collecting ring, a magnetic field collecting ring and a magnetic field generating device, wherein the magnetic field collecting ring is used for collecting a magnetic field generated by a current-carrying wire passing through the magnetic field collecting ring; a current sensor unit formed in the gap for sensing the magnetic field collected by the magnetic field collecting ring; and at least one magnetic field shielding component for shielding the magnetic field collecting ring and forming a gap with the magnetic field collecting ring so as to prevent the external magnetic field from being collected by the magnetic field collecting ring. The invention can detect and measure weak current with high accuracy and eliminate the influence of external magnetic field on measurement.

Description

current sensing device

technical field

The invention relates to a current sensing device, in particular to a current sensing device capable of sensing weak current with high accuracy.

Background technique

Currently, current sensors are widely used in the electronics industry. Generally, such sensors include a Hall effect (Hall effect) generator for sensing a magnetic field generated by a current, thereby generating a Hall effect output voltage proportional to the magnetic field.

Hall-effect generators usually consist of the same semiconductor material as a Hall plate formed on an insulating substrate, as is common. An excitation current is applied to the Hall chip, and when the Hall effect generator is placed in a magnetic field and the excitation current is applied to it, the output voltage can be measured.

In the past, a variety of sensing devices utilizing the Hall effect phenomenon have been used. As shown in FIG. 1 , a conventional current sensor 100 includes an amplifier 102, a constant current power supply 104, A gapped toroidal core (not shown) on the component side, a Hall effect generator 106 extending from the output leads of the PCB to the gap of the toroidal magnet, and an induction coil 108 placed on the edge of the gap of the toroidal core. Specifically, the Hall effect generator 106 is a standard design, and its package includes a semiconductor Hall plate (not shown) mounted on an insulating substrate (not shown), and extends the constant current line 112 and Hall Hall effect output voltage line 114.

In operation, an electrical conductor is inserted into a hole in the PCB, and current flows through the electrical conductor, thereby generating a magnetic field on the toroidal core, which passes through the gap of the toroidal core. Hall effect generator 106 and induction coil 108 are constrained by this magnetic field. The constant current power supply 104 provides a temperature-compensated constant current to the Hall plate, so that the Hall effect generator 106 produces an output voltage that varies proportionally to the magnetic field concentrated on the Hall plate, and the output voltage is provided to the amplifier 102 and amplified to available level, and finally measure the current value.

With the rapid development of the electronics industry, such as in gate control systems, the need for current sensors to sense weak currents is becoming more and more important. However, the aforementioned current sensor 100 can only detect relatively large currents due to the low sensitivity of the Hall effect. Therefore, a weak current of, for example, 0.1 mA˜100 mA cannot be detected by the current sensor 100 . Moreover, since the conventional current sensing device with the current sensor 100 does not have any magnetic field shield to prevent the external magnetic field, the external magnetic field will also be induced by the Hall effect generator 106 of the current sensor 100, which will cause the Hall effect The output signal of the generator 106 is unstable; moreover, due to the influence of the external magnetic field, the measurement accuracy is also reduced accordingly. Therefore, current current sensing devices cannot meet the demand for sensing weak currents.

Therefore, there is an urgent need for an improved current sensing device to overcome the above defects.

Contents of the invention

The purpose of the present invention is to provide a current sensing device, which can detect and measure weak current with high accuracy, and eliminate the influence of external magnetic field on the measurement.

To achieve the above object, the current sensing device of the present invention includes a magnetic field collection ring for collecting the magnetic field generated by the current-carrying wire passing through the magnetic field collection ring, and the magnetic field collection ring has a gap; a current sensor unit forms In the gap, it is used to induce the magnetic field collected by the magnetic field collection ring; and at least one magnetic field shielding component is used to shield the magnetic field collection ring and form a gap with the magnetic field collection ring, thereby preventing the external magnetic field from being The magnetic field collection ring collects.

Preferably, an insulator is provided between the magnetic field shielding component and the magnetic field collecting ring.

Preferably, the magnetic field collecting ring and the magnetic field shielding component are made of ferrite material.

Optionally, the magnetic field collecting ring and the magnetic field shielding component are made of manganese-zinc ferrite material, nickel-zinc ferrite material or permalloy material.

As an embodiment, the magnetic field shielding assembly includes a first shielding part and a second shielding part assembled together.

Preferably, a housing covering the magnetic field shielding component is also included. More preferably, the housing includes a first housing part and a second housing part respectively connected to the first shielding part and the second shielding part.

As another embodiment, the magnetic field shielding component has a slot for receiving the magnetic field collecting ring.

Preferably, the height of the slot is greater than the thickness of the magnetic field collecting ring.

Optionally, the magnetic field shielding component is in the shape of a ring or a rectangle.

As a preferred embodiment, it also includes a calibration unit connected with a calibration system of the current sensing device.

Preferably, the calibration unit includes a coil wound on the magnetic field collection ring and connected to the calibration system.

As another embodiment, the current sensor unit includes a Wheatstone bridge circuit, the Wheatstone bridge circuit has two pairs of magnetoresistive elements connected together and four connection terminals, each pair of magnetoresistive elements has two opposite pinned direction.

More preferably, the current sensor unit further includes a calibration wire with two connection terminals, the calibration wire is arranged between the two pairs of magnetoresistive elements, and the direction of the calibration wire is perpendicular to each of the The pinning direction of the MR element.

Preferably, the current sensor unit further includes a substrate body, and the Wheatstone bridge circuit and the calibration wire are laminated on different layers of the substrate body.

Optionally, the alignment wires are laminated on a flexible printed circuit or a printed circuit board.

Optionally, the current sensor unit includes a giant magnetoresistance element, a tunnel junction magnetoresistance element or a Hall effect element.

Compared with the prior art, the magnetic field shielding assembly of the present invention covers the magnetic field collecting ring and forms a gap with the magnetic field collecting ring, so the magnetic field shielding assembly will collect and absorb the external magnetic field, so the external magnetic field will not enter the magnetic field The collecting ring, and in turn, the current sensor unit in the magnetic field collecting ring does not sense an external magnetic field, but only the magnetic field generated by the current-carrying wire and collected by the magnetic field collecting ring. Therefore, the measurement accuracy of the current sensor unit is not affected by the external magnetic field, thereby improving. Furthermore, the measurement sensitivity of the current sensing device of the present invention is relatively high.

In addition, the current sensing device of the present invention has at least one calibration unit for calibrating the current sensor unit, which can prevent hysteresis of the magnetoresistive element of the current sensor unit, thereby improving the performance and stability of the current sensing device.

The present invention will become clearer through the following description in conjunction with the accompanying drawings, which are used to explain the embodiments of the present invention.

Description of drawings

Figure 1 is a block diagram of a conventional current sensor.

FIG. 2 is an exploded perspective view of an embodiment of the current sensing device of the present invention.

FIG. 3 is a top view of the current sensing device shown in FIG. 2 .

FIG. 4 is an exploded perspective view of a wire inserted into the current sensing device shown in FIG. 2 .

FIG. 5 a is a partial perspective exploded view of the current sensing device shown in FIG. 2 .

Fig. 5b is a cross-sectional view of the magnetic field shielding assembly and the magnetic field collecting ring shown in Fig. 2 .

6 is a perspective view of another embodiment of the magnetic field shielding component of the current sensing device of the present invention.

7a-7d are perspective views of various alternative embodiments of a magnetic field shield assembly.

Fig. 8a is a cross-sectional view of a GMR element of a current sensor unit.

Fig. 8b is a detailed structure diagram of another embodiment of the current sensor unit.

Fig. 9a is a graph showing the relationship between the GRM element and the magnetic field.

Fig. 9b is a graph showing the relationship between the output voltage of the Wheatstone bridge circuit and the magnetic field.

Fig. 10a is a perspective view of an embodiment of the current sensing unit of the present invention.

Fig. 10b is a perspective view of another embodiment of the current sensing unit of the present invention.

Figure 11a is a simplified perspective view of the substrate body of the current sensor unit prior to connection to the PCB.

Figure 11b is a simplified perspective view of the substrate body of the current sensor unit after connection to the PCB.

Detailed ways

Several different preferred embodiments of the present invention will now be described with reference to the accompanying drawings, wherein like reference numerals in different drawings represent like parts. As mentioned above, the essence of the present invention lies in a current sensing device, which has a magnetic field shielding component that shields the magnetic field collecting ring, thereby eliminating the influence of the external magnetic field, thereby improving measurement accuracy. Moreover, the current sensing device of the present invention has at least one calibration unit for calibrating the current sensor unit, which can prevent hysteresis of the magnetoresistive element of the current sensor unit, thereby improving the performance and stability of the current sensing device.

2 to 4 illustrate a preferred embodiment of the current sensing device of the present invention. As shown in FIG. 2 , the current sensing device 200 includes a magnetic field collection ring 210 with a gap 211 , a current sensor unit 220 disposed in the gap 211 , and a housing 230 covering the magnetic field collection ring 210 and the current sensor unit 220 . Specifically, after the current sensing device 200 is assembled, a channel 21 is formed for the current wire 26 to pass through.

Under the conception of the present invention, as shown in FIGS. gaps between. In this embodiment, two ring-shaped magnetic field shielding components 240 are included, including a ring-shaped upper magnetic field shielding component 241 and a ring-shaped lower magnetic field shielding component 242 that respectively shield the top and bottom of the magnetic field collection ring 210 . Preferably, the upper magnetic field shielding assembly 241 includes a semi-annular first shielding portion 241a and a second shielding portion 241b, and the lower magnetic field shielding assembly 242 includes a semi-annular first shielding portion 242a and a second shielding portion 242b. After the upper and lower magnetic field shielding components 241 and 242 are assembled, an accommodation space (not best shown in the figure) is formed to accommodate the magnetic field collecting ring 210, as shown in FIG. 5b. As mentioned above, the magnetic field shielding component 240 is separated from the magnetic field collecting ring 210 to form a gap 27 therebetween. Optionally, an insulator may be provided in the gap 27 to enhance the shielding effect on the external magnetic field.

Under the conception of the present invention, the magnetic field shielding assembly 240 and the magnetic field collecting ring 210 are made of magnetic materials, such as ferrite material, manganese-zinc ferrite material, nickel-zinc ferrite material or permalloy material. As a better choice, the magnetic field shielding component 240 and the magnetic field collecting ring 210 are made of ferrite material, so as to obtain a better effect and reduce the cost.

Optionally, the magnetic field shielding component 240 and the magnetic field collecting ring 210 may be composed of a mixture of ferrite material, manganese-zinc ferrite material, nickel-zinc ferrite material or permalloy material.

Specifically, please refer to FIGS. 3 and 4 again, the housing 230 includes a first housing part 231 covering the first shielding parts 241a and 242a respectively, and a housing part covering the second shielding parts 241b and 242b respectively. The second housing portion 232 . Specifically, the first housing part 231 has a stepped part 2311, and the second housing part 232 has a stepped part 2321. When the first and second housing parts 231, 232 are assembled, the two stepped parts 2311, 2321 form a channel. 21 (please refer to Figure 3). Therefore, when measuring, for example, a current-carrying grid line of the grid in the power grid is inserted from one side of the current sensing device 200, passes through the gap 211 of the magnetic field collection ring 210, and finally enters the channel 21, and is stopped by the first , The stepped portions 2311, 2321 of the second housing portions 231, 232. Therefore, there is no need to disassemble the casing 230 , and the operation is very simple and quick.

Optionally, the shape of the upper magnetic field shielding component 241 and the lower magnetic field shielding component 242 is an integral ring, as shown in FIG. 6 .

Optionally, as another embodiment, as shown in FIG. 7 a , the first shielding parts 241 a and 242 a integrally form a magnetic field shielding component 243 , and the second shielding parts 241 b and 242 b also integrally form a magnetic field shielding component 244 . The magnetic field shielding components 243 , 244 have slots 2431 , 2441 for receiving the magnetic field collecting ring 210 . Specifically, the height of the slots 2431 , 2441 is greater than the thickness of the magnetic field collecting ring 210 , so as to ensure the formation of a gap between the magnetic field shielding components 243 , 244 and the magnetic field collecting ring 210 .

Of course, the shape of the magnetic field shielding components 243, 244 is not limited here, it may be rectangular or tubular, as shown in Figs. 7b-7d. The number of magnetic field shielding components is not limited, it is only necessary to ensure that the shielding components can provide slots or spaces to accommodate and shield the magnetic field collecting ring 210 .

In summary, since the magnetic field shielding assembly 240 covers the magnetic field collecting ring 210 and forms a gap with the magnetic field collecting ring 210, the magnetic field shielding assembly 240 can collect and absorb an external magnetic field; The gap 27 is formed between the magnetic field collecting rings 210 so that the external magnetic field loop is only kept within the structure of the magnetic field shielding assembly 240 . Therefore, the external magnetic field loop will not enter the magnetic field collection ring 210 , so the current sensor unit 220 will not sense the external magnetic field, but only the magnetic field generated by the current-carrying wire and collected by the magnetic field collection ring 210 . Therefore, the measurement accuracy of the current sensing device 200 is not affected by the external magnetic field, thereby being improved.

The current sensor unit 220 of the present invention is composed of a GMR element, a TMR element or a Hall effect element. In this embodiment, the current sensor unit 220 uses a GMR element.

FIG. 8 a shows a laminated structure of a GMR element, which includes a substrate layer 301 , a buffer layer 302 , a fixed layer 307 and a capping layer 306 laminated in sequence. Specifically, the pinned layer 307 includes a pinned layer 305 for pinning the magnetization direction in a fixed direction, a free layer 303 having a magnetization direction that varies with an external magnetic field, and a layer laminated on the pinned layer 305 and the free layer. 303 between spacer layers 304 . The spacer layer 304 acts as a non-magnetic electrical conductor. As is well known, the resistance of a GMR element varies with the angle between the pinning direction of the pinned layer 305 and the magnetization direction of the free layer 303 . When the GMR device is placed in an external magnetic field, the magnetization direction of the free layer 303 will change due to the external magnetic field, that is, the angle between the pinning direction of the pinned layer 305 and the magnetization direction of the free layer 303 changes. Therefore, the resistance of the GMR element also changes, which in turn generates an output voltage.

A detailed structure of the current sensor unit 220 will now be described. As shown in FIG. 8 b , specifically, the current sensor unit 220 includes a Wheatstone bridge circuit 222 composed of four GMR elements, namely G1 , G2 , G3 and G4 . Specifically, G1 and G4 have the same pinning direction (not numbered, indicated by the arrow in the figure) and magnetization direction (not shown in the figure), and G2 and G3 have the same pinning direction (not numbered, indicated by the arrow in the figure). arrows) and magnetization directions (not shown), wherein, the pinning directions of G1 and G4 are opposite to those of G1 and G4. The four GMR elements G1 - G4 are connected together and terminated at four connection terminals: Vcc, Gnd, Vout+ and Vout−. Connect terminals Vcc and Gnd as input terminals, and connect terminals Vout+ and Vout- as output terminals. Therefore, the voltages at the output terminals Vout+ and Vout- vary with the change of the magnetization direction and the pinning direction of the resistances of G1-G4 under the action of the external magnetic field.

Thus, when the current carrying wire 26 is inserted into the current sensing device 200 , a magnetic field is generated around the current carrying wire 26 which is then collected 210 by the magnetic field collecting ring. Therefore, the magnetic field by the magnetic field collecting ring 210 is sensed by the current sensor unit 220 disposed in the gap 211 . Specifically, the GMR elements G1 - G4 of the Wheatstone bridge circuit 222 of the current sensor unit 220 vary with the magnetic field, so that output terminals Vout+ and Vout− output differential voltages matching the magnetic field. After the differential voltage is converted and calculated, the corresponding current value can be measured.

After multiple measurements, the pinning directions and magnetization directions of the GMR elements G1-G4 will shift and change from the initial directions, thereby generating hysteresis of the resistance of the GMR elements, as shown in FIG. 9a. Ideally, the relationship between the resistance and the magnetic field of a GMR element is shown in curve C1. However, due to the aforementioned problems, hysteresis occurs as shown by curves C2, C3. Therefore, the output signal of the current sensor unit 220 is extremely unstable and deviates from an accurate value, as shown in FIG. 9b, resulting in low measurement accuracy.

Accordingly, a preferred embodiment of the present invention aims at improving measurement accuracy. As shown in FIGS. 2 and 4 again, the current sensing device 200 of the present embodiment includes a magnetic field collecting ring 210 having a gap 211, a current sensor unit 220 disposed in the gap 211, covering the magnetic field collecting ring 210 and the current sensor unit 220 The housing 230, and a calibration unit. The calibration unit includes a coil 251 wound around the magnetic field collection ring 210 and connected to a calibration system (not shown) of the current sensing device 200 . Before the measurement process starts, the calibration system sends a calibration signal/voltage, such as an AC signal, to the coil 251, and the calibration signal/voltage generates a calibration magnetic field around the coil 251, and the calibration magnetic field will go back and forth at the same fixed frequency as the calibration signal/voltage change direction. Since the coil 251 is wound around the magnetic field collecting ring 210, and the current sensor unit 220 is arranged in the gap 211 of the magnetic field collecting ring 210, the magnetic field collecting ring 210 will absorb the calibration magnetic field, and the current sensor unit 220 will also sense the calibration magnetic field, and Calibrate or refresh the magnetization direction of the free layer of the GMR element so that it rotates back and forth along the pinned direction and finally returns to its original position direction, thereby eliminating the above-mentioned offset and hysteresis problems, thereby improving the current sensor unit 220. performance, improved stability and precision. Optionally, the calibration signal/voltage may be a DC or AC/DC mixed signal with a controllable or variable frequency.

In addition, the present invention also provides a better embodiment to further improve the measurement accuracy. As shown in FIG. 8 b , the current sensing device 200 further includes a calibration system or structure disposed in the current sensor unit 220 . Specifically, the calibration system or structure includes a calibration wire 223 arranged between the GMR elements G, G2 and G3, G4 of the Wheatstone bridge circuit 222, and the direction of the calibration wire 223 is perpendicular to the GMR elements G1-G4. Pinning direction. Specifically, the two connection terminals of the calibration wire 223 are V+ and V-.

The Wheatstone bridge circuit 222 is calibrated by the calibration wire 223 before the current sensing device 200 starts measuring. First, the calibration system applies a calibration signal/voltage, such as an AC signal, to the calibration wire 223 through two connection terminals, and the calibration signal/voltage generates a calibration magnetic field around the calibration wire 223 . Since the calibration wire 223 is arranged between the GMR elements G1, G2 and G3, G4 of the Wheatstone bridge circuit 222, and its arrangement direction is perpendicular to the pinning direction of the GMR elements G1-G4, therefore, the magnetic field generated by the calibration signal Under the influence of , the magnetization directions of the free layers of the GMR elements G1-G4 change along the pinned direction. Moreover, since the calibration signal is an AC signal, the direction of the calibration signal changes back and forth with a fixed frequency, therefore, the direction of the calibration magnetic field also always changes back and forth with a fixed frequency. The calibration magnetic field will calibrate or refresh the magnetization direction of the free layer of the GMR element, so that it rotates back and forth along the pinned direction and finally returns to its original position direction, thereby eliminating the above-mentioned offset and hysteresis problems, thereby increasing the current The performance of the sensor unit 220 improves stability and precision. Optionally, the calibration signal/voltage may be a DC or AC/DC mixed signal with a controllable or variable frequency.

10a-10b show the lamination of Wheatstone bridge circuit 222 and calibration wire 223 in a substrate body 221 . Due to the manufacturing process, the Wheatstone bridge circuit 222 and the calibration wire 223 cannot be disposed on the same layer. As shown in FIG. 10a, the calibration wire 223 is laminated under the Wheatstone bridge circuit 222, so the calibration wire 223 is connected to the connection terminals V+ and V- through through holes (not shown), so that the connection terminals V+, V- and four connection terminals Vcc, Gnd, Vout+, Vout- of the Wheatstone bridge circuit 222 are formed on the same surface. This structure makes the assembly steps of the current sensing device 200 simpler, thereby saving costs. Figure 10b shows another embodiment, the calibration wire 223 is laminated on the Wheatstone bridge circuit 222, so that the Wheatstone bridge circuit 222 is terminated by via holes and connected to the connection terminals Vcc, Gnd, Vout+, Vout- , and the connection terminal of the calibration wire 223 is formed on the same surface.

11a-11b show another embodiment, in this embodiment, the calibration wire 223 can be provided on the sensor element mounting board, such as a flexible circuit (FPC) or a printed circuit board (PCB). The Wheatstone bridge front circuit 222 is mounted on the mounting board such that the calibration wire 223 is located under the Wheatstone bridge circuit 222 . As shown in the figure, a through slot 41 is provided on the PCB 40, and its shape and size correspond to the substrate body 221 on which the Wheatstone bridge circuit 222 is laminated. The substrate body 221 is inserted into the through groove 41 and welded together with epoxy glue. Specifically, a plurality of connection points 411, 412, 413, 414, 415, 416 are provided on the surface of the PCB 40 close to the through groove 41, wherein the connection points 414, 415 are connected to the calibration wire 223. The connection terminals Vcc, Gnd, Vout+ and Vout− of the Wheatstone bridge circuit 222 are connected to connection points 411, 412, 413, 414, respectively. V+ and V- are connected to connection points 415 and 416 through jumpers. After the substrate body 221 is installed on the PCB 40, the calibration wire 223 is arranged between the two pairs of GMR elements, and its arrangement direction is perpendicular to the pinning direction of each GMR element.

Therefore, when a calibration system (not shown) applies a calibration signal/voltage, such as an AC signal, to the calibration wire 223 through the two connection points, the calibration signal/voltage generates a calibration magnetic field around the calibration wire 223 . Since the calibration wire 223 is arranged between the GMR elements G1, G2 and G3, G4 of the Wheatstone bridge circuit 222, and its arrangement direction is perpendicular to the pinning direction of the GMR elements G1-G4, therefore, the magnetic field generated by the calibration signal Under the influence of , the magnetization directions of the free layers of the GMR elements G1-G4 change along the pinned direction. Moreover, since the calibration signal is an AC signal, the direction of the calibration signal changes back and forth with a fixed frequency, therefore, the direction of the calibration magnetic field also always changes back and forth with a fixed frequency. The calibration magnetic field will calibrate or refresh the magnetization direction of the free layer of the GMR element, so that it rotates back and forth along the pinned direction and finally returns to its original position direction, thereby eliminating the above-mentioned offset and hysteresis problems, thereby increasing the current The performance of the sensor unit 220 improves stability and precision. Optionally, the calibration signal/voltage may be a DC or AC/DC mixed signal with a controllable or variable frequency.

The above disclosures are only preferred embodiments of the present invention, and certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the patent scope of the present invention still fall within the scope of the present invention.

Claims (18)

1. A current sensing device, characterized in that, comprising: A magnetic field collection ring for collecting the magnetic field generated by the current-carrying wire passing through the magnetic field collection ring, the magnetic field collection ring has a gap; a current sensor unit formed in the gap for sensing the magnetic field collected by the magnetic field collecting ring; and At least one magnetic field shielding component is used to shield the magnetic field collecting ring and form a gap with the magnetic field collecting ring, so as to prevent external magnetic fields from being collected by the magnetic field collecting ring. 2. The current sensing device according to claim 1, wherein an insulator is disposed between the magnetic field shielding component and the magnetic field collecting ring. 3. The current sensing device according to claim 1, wherein the magnetic field collecting ring and the magnetic field shielding component are made of ferrite material. 4. The current sensing device according to claim 1, wherein the magnetic field collecting ring and the magnetic field shielding component are made of manganese-zinc ferrite material, nickel-zinc ferrite material or permalloy material become. 5. The current sensing device according to claim 1, wherein the magnetic field shielding assembly comprises a first shielding portion and a second shielding portion assembled together. 6. The current sensing device according to claim 5, further comprising a casing covering the magnetic field shielding component. 7. The current sensing device of claim 6, wherein the housing comprises a first housing portion and a second housing portion respectively connected to the first shielding portion and the second shielding portion . 8. The current sensing device as claimed in claim 1, wherein the magnetic field shielding component has a slot for receiving the magnetic field collecting ring. 9. The current sensing device according to claim 8, wherein the height of the slot is greater than the thickness of the magnetic field collecting ring. 10. The current sensing device as claimed in claim 1, wherein the magnetic field shielding component is ring-shaped. 11. The current sensing device as claimed in claim 1, wherein the magnetic field shielding component is rectangular. 12. The current sensing device of claim 1, further comprising a calibration unit connected to a calibration system of the current sensing device. 13. The current sensing device according to claim 12, wherein the calibration unit comprises a coil wound on the magnetic field collecting ring and connected to the calibration system. 14. The current sensing device of claim 1, wherein said current sensor unit comprises a Wheatstone bridge circuit having two pairs of magnetoresistive elements connected together and four Connecting the terminals, each pair of magneto-resistive elements has two opposite pinning directions. 15. The current sensing device according to claim 14, wherein the current sensor unit further comprises a calibration wire having two connection terminals, the calibration wire is arranged between the two pairs of magnetoresistive elements, and The setting direction of the calibration wire is perpendicular to the pinning direction of each magnetoresistive element. 16. The current sensing device according to claim 15, wherein the current sensor unit further comprises a substrate body, and the Wheatstone bridge circuit and the calibration wire are laminated with the substrate body on different layers. 17. The current sensing device as claimed in claim 15, wherein the alignment wire is laminated on a flexible printed circuit or a printed circuit board. 18. The current sensing device according to claim 14, wherein the current sensor unit comprises a giant magnetoresistive element, a tunnel junction magnetoresistive element or a Hall effect element.

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