Current sensor, sensing device and preparation method thereof

Abstract

The present invention relates to the technical field of current sensors, and provides a current sensor, a sensing device and a preparation method thereof. The current sensor comprises two U-shaped symmetrically arranged magnetic focusing rings, whose openings are arranged opposite to each other, forming a cavity for accommodating the conductor to be measured and a first air gap position and a second air gap position; two magnetomechanical composite units, which are respectively located at the first air gap position and the second air gap position, and are respectively fixedly connected to the two end faces of the second magnetic focusing ring, for sensing the external magnetic field around the conductor to be measured and generating opposite longitudinal vibrations in the direction perpendicular to the two end faces, and outputting differential signals; a substrate, for supporting the two magnetic focusing rings. The present invention realizes non-contact measurement of low-frequency current through the synergistic effect of the magnetomechanical composite unit and the magnetic focusing ring, and has the characteristics of low energy consumption, strong anti-interference, high sensitivity, and easy implementation.

Description

Technical Field

[0001] The present invention relates to the technical field of current sensors, and in particular to a current sensor, a sensing device and a preparation method thereof. Background Art

[0002] Current sensors are widely used in industry, national defense, science and technology, medical and other fields.

[0003] The magnetostrictive / piezoelectric composite current sensor uses magnetostrictive material as the induction current magnetic field element and piezoelectric material as the main signal output element. It is used for high-frequency current measurement and generally has the advantages of high sensitivity and good linearity.

[0004] Magnetostrictive materials generally need to be subjected to a certain bias magnetic field through a Helmholtz coil or a permanent magnet so that they can work in the linear region where the magnetostrictive coefficient changes with the bias magnetic field and the maximum point of the piezomagnetic coefficient. The introduction of the bias magnetic field greatly increases the energy consumption of the current sensor.

[0005] Magnetostrictive / piezoelectric composite current sensors are used to measure low-frequency currents such as industrial frequency, and their sensitivity is generally not high.

[0006] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0007] The purpose of the present invention is to provide a current sensor, a sensing device and a preparation method thereof, so as to improve the defects of the existing magnetoelectric composite current sensor, such as high energy consumption and unsuitability for low-frequency current measurement, thereby providing a current sensor, a sensing device and a preparation method thereof.

[0008] To achieve the above objective, a first aspect of the present invention provides a current sensor.

[0009] The current sensor comprises:

[0010] Two U-shaped symmetrical magnetic focusing rings, wherein the openings of the first magnetic focusing ring and the second magnetic focusing ring are arranged opposite to each other, forming a cavity for accommodating the wire to be tested and a first air gap position and a second air gap position located on both sides of the cavity;

[0011] Two magneto-mechanical composite units of the same structure, wherein the first magneto-mechanical composite unit and the second magneto-mechanical composite unit are respectively located at the first air gap position and the second air gap position and are respectively fixedly connected to the two end faces of the second magnetic focusing ring, and are used to sense the external magnetic field around the conductor to be tested and generate opposite longitudinal vibrations in the direction perpendicular to the two end faces, and output differential signals;

[0012] A signal processing module is used to output the current value of the conductor to be tested according to the differential signal.

[0013] A base is used to support the first magnetic focusing ring and the second magnetic focusing ring.

[0014] According to some embodiments of the present invention, the magnetomechanical composite unit comprises a first electrode, a second electrode, and a first permanent magnet block, an electromechanical composite layer, and a second permanent magnet block arranged in sequence along a first direction; the first direction is parallel to the thickness direction of the magnetic focusing ring;

[0015] The first permanent magnet block and the second permanent magnet block are magnetically adsorbed on both sides of the free end of the electromechanical composite layer;

[0016] The electromechanical composite layer comprises a piezoelectric layer and an elastic layer which are stacked;

[0017] The elastic layer, the first electrode, the piezoelectric layer and the second electrode are arranged in sequence along the first direction;

[0018] The first permanent magnet block and the second permanent magnet block can generate the longitudinal vibration approaching or moving away from the second magnetic focusing ring under the action of the external magnetic field.

[0019] According to some embodiments of the present invention, the first electrode in the first magneto-electromechanical composite unit is electrically coupled to the first electrode in the second magneto-electromechanical composite unit, and the signal processing module is electrically coupled to the second electrode in the first magneto-electromechanical composite unit and the second electrode in the second magneto-electromechanical composite unit respectively; or,

[0020] The second electrode in the first magneto-mechanical composite unit is electrically coupled to the second electrode in the second magneto-mechanical composite unit, and the signal processing module is electrically coupled to the first electrode in the first magneto-mechanical composite unit and the first electrode in the second magneto-mechanical composite unit respectively.

[0021] According to some embodiments of the present invention, the resonance frequency of the first permanent magnet block and the second permanent magnet block is 50 Hz.

[0022] According to some embodiments of the present invention, the elastic layer is spring steel; the magnetic focusing ring is Permalloy; the piezoelectric layer is piezoelectric single crystal, piezoelectric ceramic or piezoelectric polymer; the first permanent magnet block and the second permanent magnet block are square permanent magnets.

[0023] According to some embodiments of the present invention, the elastic layer is made of 304 stainless steel;

[0024] The material of the piezoelectric layer is AlN, quartz, LiNbO3, BaTiO3, ZnO, Pb(Zr, Ti)O3, Pb(Mg, Nb)O3-PbTiO3, Pb(Zn, Nb)O3-PbTiO3 or BiScO3-PbTiO3;

[0025] The material of the magnetic focusing ring is 1J85;

[0026] The first permanent magnet block and the second permanent magnet block are made of neodymium iron boron.

[0027] According to some embodiments of the present invention, the elastic layer has a length of 1.8 to 2.5 cm, a width of 2.6 to 4 mm, and a thickness of 0.15 to 0.3 mm;

[0028] The piezoelectric layer has a length of 1.8 to 2.5 cm, a width of 2.6 to 4 mm, and a thickness of 0.15 to 0.3 mm;

[0029] The permanent magnet block is a square block with a side length of 2.6 to 4 mm.

[0030] According to some embodiments of the present invention, the substrate includes a first supporting surface and a second supporting surface;

[0031] The first supporting surface is arranged at a side of the first magnetic focusing ring close to the second magnetic focusing ring, and is used to support the first magnetic focusing ring; the magnetomechanical composite unit is away from the first supporting surface.

[0032] The second supporting surface is arranged on a side of the second magnetic focusing ring away from the cavity, and is used for supporting the second magnetic focusing ring.

[0033] To achieve the above object, a second aspect of the present invention provides a method for preparing a current sensor, wherein the current sensor is the above current sensor; the preparation method comprises:

[0034] (1) taking a piezoelectric material and an elastic material, and making them into a piezoelectric layer and an elastic layer respectively;

[0035] (2) depositing electrodes on the upper surface and the lower surface of the piezoelectric layer respectively, and polarizing the piezoelectric layer in the thickness direction to obtain a first composite layer;

[0036] (3) laminating and bonding the first composite layer and the elastic layer to obtain a second composite layer;

[0037] (4) placing permanent magnet blocks on both sides of the first end of the second composite layer to obtain a magnetomechanical composite unit;

[0038] (5) placing two U-shaped magnetic focusing rings in the base, with the openings of the first magnetic focusing ring and the second magnetic focusing ring arranged opposite to each other, thereby forming a cavity and a first air gap position and a second air gap position located on both sides of the cavity;

[0039] (6) The two magnetomechanical composite units are fixedly connected to the two end surfaces of the second magnetic focusing ring respectively, wherein the thickness direction of the piezoelectric layer in the two magnetomechanical composite units is parallel to the thickness direction of the magnetic focusing ring;

[0040] (7) electrically coupling two electrodes located on the same side of the two magnetomechanical composite units;

[0041] (8) Collecting output signals of two electrodes located on the other side of the two magneto-electromechanical composite units.

[0042] To achieve the above object, the third aspect of the present invention provides a sensing device. The sensing device includes a current sensor; the current sensor is the above current sensor.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] The current sensor provided by the present invention includes: two magnetic focusing rings symmetrically arranged in a U-shape, whose openings are arranged opposite to each other, forming a cavity for accommodating the conductor to be measured and a first air gap position and a second air gap position; two magnetomechanical composite units of the same structure, which are respectively located at the first air gap position and the second air gap position, and are respectively fixedly connected to the two end faces of the second magnetic focusing ring, for sensing the external magnetic field around the conductor to be measured and generating opposite longitudinal vibrations in the direction perpendicular to the two end faces, and outputting differential signals; a substrate, for supporting the two magnetic focusing rings. The present invention realizes non-contact measurement of low-frequency current through the synergistic effect of the magnetomechanical composite unit and the magnetic focusing ring, and has the characteristics of low energy consumption, strong anti-interference, high sensitivity, and easy implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A schematic diagram of the structure of a current sensor in an embodiment of the present invention;

[0046] Figure 2 A schematic diagram of the structure of a magneto-mechanical-electrical composite unit in an embodiment of the present invention;

[0047] Figure 3 : is a magneto-electric voltage coefficient curve of the magneto-mechanical composite unit in the frequency range of 30 to 100 Hz in an embodiment of the present invention;

[0048] Figure 4 The output variation curve of the current sensor in the embodiment of the present invention when the current varies in the range of 0 to 50A;

[0049] Figure 5It is the detection limit curve of the current sensor in the embodiment of the present invention at a frequency of 50 Hz and a current variation range of 0.001A to 1A;

[0050] Figure 6 The output response waveform curve of the first magneto-mechanical composite unit and the second magneto-mechanical composite unit in the current sensor in the embodiment of the present invention to 50 Hz vibration;

[0051] Figure 7 A schematic diagram of the first position of the current sensor and the interference wire in the embodiment of the present invention and an output response waveform curve generated by the first magneto-mechanical composite unit and the second magneto-mechanical composite unit to the interference wire in the first position in the embodiment of the present invention;

[0052] Figure 8 A schematic diagram of the second position of the current sensor and the interference wire in the embodiment of the present invention and an output response waveform curve generated by the first magneto-mechanical composite unit and the second magneto-mechanical composite unit to the interference wire in the second position in the embodiment of the present invention;

[0053] Fig. 9 A schematic diagram of the third position of the current sensor and the interference wire in the embodiment of the present invention and an output response waveform curve generated by the first magneto-mechanical composite unit and the second magneto-mechanical composite unit to the interference wire in the third position in the embodiment of the present invention;

[0054] Fig.10 A schematic diagram of a fourth position of the current sensor and the interference wire in an embodiment of the present invention and an output response waveform curve generated by the first magneto-mechanical composite unit and the second magneto-mechanical composite unit to the interference wire in the fourth position in an embodiment of the present invention;

[0055] Fig.11 The output response change curve of the first magneto-mechanical composite unit and the second magneto-mechanical composite unit in the embodiment of the present invention to the interfering wire within the range of 0 to 10 cm away from the second position;

[0056] Fig.12 This is the output response change curve of the first magneto-mechanical-electrical composite unit in the embodiment of the present invention to the interfering wire within the range of 0 to 10 cm away from the fourth position.

[0057] Reference numerals:

[0058] 11 first substrate; 12 second substrate; 21 first magnetic focusing ring; 22 second magnetic focusing ring; 221 first end face; 222 second end face; 30 second magneto-mechanical composite unit; 40 first magneto-mechanical composite unit; 31 elastic layer; 32 piezoelectric layer; 33 first permanent magnet block; 34 second permanent magnet block; 35 first electrode; 36 second electrode.

[0059] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0060] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0061] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] Current sensors are widely used in industry, national defense, science and technology, medical and other fields.

[0063] The magnetostrictive / piezoelectric composite current sensor uses magnetostrictive material as the induction current magnetic field element and piezoelectric material as the main signal output element. It is used for high-frequency current measurement and generally has the advantages of high sensitivity and good linearity.

[0064] Magnetostrictive materials generally need to be subjected to a certain bias magnetic field through a Helmholtz coil or a permanent magnet so that they can work in the linear region where the magnetostrictive coefficient changes with the bias magnetic field and the maximum point of the piezomagnetic coefficient. The introduction of the bias magnetic field greatly increases the energy consumption of the current sensor.

[0065] When magnetostrictive / piezoelectric composite current sensors are used to measure low-frequency currents such as industrial frequency, their sensitivity is generally not high.

[0066] Therefore, in order to improve the defects of the existing magneto-electric composite current sensor, such as high energy consumption and unsuitability for low-frequency current measurement, an embodiment of the present invention provides a current sensor.

[0067] like Figure 1 As shown, the current sensor of the embodiment of the present invention comprises a substrate (11, 12), two U-shaped symmetrically arranged magnetic focusing rings (21, 22), two magnetomechanical composite units (30, 40) with the same structure, and a signal processing module (not shown).

[0068] In the two magnetic focusing rings of the embodiment of the present invention, the first magnetic focusing ring 21 and the second magnetic focusing ring 22 are both U-shaped, and their openings are arranged opposite to each other, so that a cavity for accommodating the wire to be tested and a first air gap position and a second air gap position located on both sides of the cavity are formed between the first magnetic focusing ring 21 and the second magnetic focusing ring 22.

[0069] The substrate of the embodiment of the present invention includes a first substrate 11 connected to the first magnetic focusing ring and a second substrate 12 connected to the second magnetic focusing ring. The position of the second substrate 12 in contact with the second magnetic focusing ring 22 has an arc-shaped groove matching the outer surface shape of the second magnetic focusing ring 22, so that the second substrate can provide support for the second magnetic focusing ring 22 through the arc-shaped groove; the first substrate 11 includes a supporting surface in contact with the two end surfaces of the first magnetic focusing ring, so that the first substrate can provide support for the first magnetic focusing ring 21 through the supporting surface.

[0070] It should be noted that the first substrate may also be in contact with the arc-shaped outer side of the first magnetic focusing ring, and support is achieved by being fixedly connected to the arc-shaped outer side of the first magnetic focusing ring, which is not limited here.

[0071] The two magnetomechanical composite units of the embodiment of the present invention have the same structure, wherein the first magnetomechanical composite unit 40 is located at the first air gap position and is fixedly connected to the first end face 221 of the second magnetic focusing ring 13; the second magnetomechanical composite unit 30 is located at the second air gap position and is fixedly connected to the second end face 222 of the second magnetic focusing ring 13 opposite to the first end face 221. The first magnetomechanical composite unit and the second magnetomechanical composite unit both have a free end, which can generate vibration under the action of an external force.

[0072] Under the action of the two magnetic focusing rings, the first magneto-electromechanical composite unit 40 and the second magneto-electromechanical composite unit 30 can be used to sense the external magnetic field around the conductor to be tested in the cavity, and generate opposite longitudinal vibrations in the directions perpendicular to the two end faces of the second magnetic focusing ring. The longitudinal vibrations affect the electrical signals of the piezoelectric layers in the first magneto-electromechanical composite unit and the second magneto-electromechanical composite unit, and output differential signals.

[0073] It should be understood that the two end faces of the second magnetic focusing ring are located in the same plane, which is parallel to the thickness direction of the magnetic focusing ring and perpendicular to the extension direction of the two magnetic focusing rings.

[0074] It should be understood that the magnetomechanical composite unit (30, 40) of the embodiment of the present invention can generate longitudinal vibration in an environment with a magnetic field, and output an electrical signal corresponding to the external magnetic field based on the longitudinal vibration.

[0075] Since the longitudinal vibrations generated by the two magnetomechanical composite units under the same magnetic field are in opposite directions, the differential signals of the two magnetomechanical composite units can cancel the surrounding interference signals and thus better feedback the information of the external magnetic field. Specifically, the electrical signal output by the magnetomechanical composite unit under the same magnetic field includes both the magnetic field electrical signal and the interference electrical signal; when there is an external magnetic field around the conductor to be tested in the cavity, the output electrical signal of the first magnetomechanical composite unit is H 导 +H 干扰 The output electrical signal of the second magneto-mechanical composite unit is -H conduction +H 干扰 , where H导 H is an electrical signal proportional to the current of the conductor to be measured. 干扰 The output signal of the first magneto-mechanical composite unit and the second magneto-mechanical composite unit after differential connection is 2H 导 , which is proportional to the current of the conductor to be measured and has nothing to do with the interference signal. Therefore, the current signal measured by the current sensor of the embodiment of the present invention has anti-interference performance.

[0076] The signal processing module is used to output the current value of the conductor to be tested according to the differential signal output by the first magnetomechanical composite unit 40 and the second magnetomechanical composite unit 30. Specifically, the signal processing module is electrically coupled to the first magnetomechanical composite unit and the second magnetomechanical composite unit respectively.

[0077] The two magneto-mechanical composite units of the embodiment of the present invention have the same structure. The magneto-mechanical composite unit (30, 40) comprises a first electrode 35, a second electrode 36, a first permanent magnet block 33, a second permanent magnet block 34 and a magneto-mechanical composite layer. The magneto-mechanical composite layer comprises a stacked elastic layer 31 and a piezoelectric layer 32, wherein the first electrode 35 and the second electrode 36 are respectively arranged on two side surfaces of the piezoelectric layer. The first permanent magnet block and the second permanent magnet block are respectively arranged at the free ends of the first end surface or the second end surface of the piezoelectric layer 32 and the elastic layer 31 away from the second magnetic focusing ring.

[0078] like Figure 2 As shown, the first permanent magnet block 33, the electromechanical composite layer (32, 31) and the second permanent magnet block 34 of the embodiment of the present invention are stacked in sequence along a first direction; the first direction is parallel to the thickness direction of the magnetic focusing ring.

[0079] The first permanent magnet block 33 and the second permanent magnet block 34 are magnetically adsorbed on both sides of the free end of the electromechanical composite layer (32, 31) under the effect of opposite attraction. The elastic layer 31, the first electrode 35, the piezoelectric layer 32 and the second electrode 36 are arranged in sequence along the first direction.

[0080] After magnetic attraction, the first permanent magnet block 33 and the second permanent magnet block 34 can make the magnetomechanical composite unit generate longitudinal vibration close to or away from the second magnetic focusing ring under the action of the external magnetic field.

[0081] It should be understood that, in the embodiment of the present invention, the piezoelectric layer in the first magneto-electromechanical composite unit and the piezoelectric layer in the second magneto-electromechanical composite unit are located on the same side, the elastic layer in the first magneto-electromechanical composite unit and the elastic layer in the second magneto-electromechanical composite unit are located on the same side, and the first electrode and the second electrode serve as conductive ports respectively, but the first electrode or the second electrode plays opposite roles in the first magneto-electromechanical composite unit and the second magneto-electromechanical composite unit.

[0082] In the embodiment of the present invention, the first electrode in the first magneto-electromechanical composite unit is electrically coupled to the first electrode in the second magneto-electromechanical composite unit, and the signal processing module is electrically coupled to the second electrode in the first magneto-electromechanical composite unit and the second electrode in the second magneto-electromechanical composite unit, respectively, so that the differential signal is the difference between the output signal of the first magneto-electromechanical composite unit and the output signal of the second magneto-electromechanical composite unit.

[0083] In other embodiments of the present invention, it can also be arranged that: the second electrode in the first magneto-electromechanical composite unit is electrically coupled with the second electrode in the second magneto-electromechanical composite unit, and the signal processing module is electrically coupled with the first electrode in the first magneto-electromechanical composite unit and the first electrode in the second magneto-electromechanical composite unit respectively, which is not specifically limited here.

[0084] The first permanent magnet block and the second permanent magnet block of the embodiment of the present invention have the same size and material, and the material is a permanent magnet material, preferably neodymium iron boron. When used for measuring power frequency current, the resonant frequency can be adjusted to 50Hz. The resonant frequency is related to its size. It is preferably a cube with a side length of 2.6 to 4mm.

[0085] The elastic layer of the embodiment of the present invention is a spring steel material, and its material is preferably 304 stainless steel. It is a thin rectangular parallelepiped with a length of 1.8 to 2.5 cm, a width of 2.6 to 4 mm, and a thickness of 0.15 to 0.3 mm.

[0086] The piezoelectric layer of the embodiment of the present invention is a piezoelectric material such as a piezoelectric single crystal, a piezoelectric ceramic, a piezoelectric polymer, etc., and its material is preferably AlN, quartz, LiNbO3, BaTiO3, ZnO, Pb(Zr, Ti)O3, Pb(Mg, Nb)O3-PbTiO3, Pb(Zn, Nb)O3-PbTiO3 or BiScO3-PbTiO3. Its size matches that of the elastic layer, and its length is 1.8 to 2.5 cm, its width is 2.6 to 4 mm, and its thickness is 0.15 to 0.3 mm.

[0087] The substrate of the embodiment of the present invention can be spliced ​​or integrally formed, and at least includes a first support surface arranged on a side of the first magnetic focusing ring close to the second magnetic focusing ring and a second support surface arranged on a side of the second magnetic focusing ring away from the cavity; wherein the first support surface is used to support the first magnetic focusing ring, and the second support surface is used to support the second magnetic focusing ring. Furthermore, in order to make the magnetomechanical composite unit have a free end away from the end face of the second magnetic focusing ring, the free ends of the two magnetomechanical composite units are away from the first support surface.

[0088] The magnetomechanical composite unit of the embodiment of the present invention includes a piezoelectric layer, an elastic layer and a pair of permanent magnet blocks, and the two permanent magnet blocks are arranged at the free ends of the piezoelectric layer and the elastic layer in a magnetic adsorption manner. When there is a surrounding magnetic field of the conductor to be measured in the cavity, the magnetic field direction of the external magnetic field acting on the first magnetomechanical composite unit and the second magnetomechanical composite unit through the magnetic focusing ring is opposite and parallel to the direction of separation of the two magnetic focusing rings. The first permanent magnet block and the second permanent magnet block in the two magnetomechanical composite units are permanent magnetic materials, and their coercive force under the external magnetic field can drive the elastic layer on the side of the permanent magnet block to produce elastic movement (stretching or shrinking) perpendicular to the end face of the magnetic focusing ring. The elastic movement causes the pressure felt by the piezoelectric layer to change, which is a contraction stress or a tensile stress, thereby causing the piezoelectric layer to output different electrical signals.

[0089] The current measurement effect of the current sensor according to an embodiment of the present invention is verified as follows.

[0090] like Figure 7-10 As shown, in the current sensor of the embodiment of the present invention, the first magnetic focusing ring and the second magnetic focusing ring are opened opposite to each other, forming a cavity and a first air gap position and a second air gap position; the substrate includes a base for supporting the first magnetic focusing ring and a support frame for supporting the second magnetic focusing ring, the support frame is located above the base, and the base and the support frame are both made of high hardness materials, and the material is one of acrylic, brass, high manganese steel, high manganese alloy, ultra-high manganese alloy, chromium alloy cast iron, and chromium carbide composite material.

[0091] The first permanent magnet block and the second permanent magnet block are both cubes with a side length of 3 mm and are made of neodymium iron boron. The first permanent magnet block and the second permanent magnet block are magnetically adsorbed along the thickness direction of the magnetic focusing ring.

[0092] The material of the piezoelectric layer is PZT-5, with a length of 2 cm, a width of 3 mm, and a thickness of 0.2 mm; the material of the elastic layer is 304 stainless spring steel, with a length of 2 cm, a width of 3 mm, and a thickness of 0.2 mm; the piezoelectric layer and the elastic layer are bonded and fixed by epoxy resin. The first electrode and the second electrode are respectively fixed to the two sides of the piezoelectric layer by conductive tape. The first electrode in the first magnetomechanical composite unit is electrically coupled to the first electrode in the second magnetomechanical composite unit. The second electrode in the first magnetomechanical composite unit and the second electrode in the second magnetomechanical composite unit are used to output a differential signal.

[0093] The resonant frequency of the magneto-mechanical composite unit in the current sensor provided in this embodiment is 50 Hz. Specifically, by testing the frequency response performance of the magneto-mechanical composite unit, a magneto-electric voltage coefficient curve of the magneto-mechanical composite unit in the range of 30 to 100 Hz is obtained, such as Figure 3 As shown. Figure 3, there is a peak at 50Hz, the sensitivity of the magnetic field at this resonance is 2.58V / Oe; and the magnetoelectric coefficient at other frequencies is very low. Therefore, the frequency 50Hz at the resonance peak corresponds to the longitudinal mechanical vibration frequency of the first magneto-electromechanical composite unit.

[0094] The current sensor provided in this embodiment has high sensitivity for measuring current at a frequency of 50 Hz. Specifically, the output change curve of the current sensor of the embodiment is tested at a frequency of 50 Hz when the current of the wire to be tested varies from 0 to 50 A, as shown in FIG. Figure 4 As shown. Figure 4 The output voltage of the current sensor increases linearly with the current value, and the sensitivity is about 88mV / A; when the current value is 36A, the maximum error between the output value and the fitting value is 25mV, and the linear error is only 0.5%. Therefore, the experimental results show that the current sensor of the embodiment of the present invention has good detection sensitivity and good linearity for low-frequency current, and has the ability to detect low-frequency magnetic fields.

[0095] The current sensor provided in this embodiment has a detection limit of 40mA for 50Hz low-frequency current measurement. Specifically, the detection limit curve of the current sensor of the embodiment is tested at a frequency of 50Hz when the current variation range of the measured wire is 0.001 to 1A, as shown in FIG. Figure 5 As shown. Figure 5 , the sensor output value no longer maintains linear change at 40mA. Therefore, the detection limit of the sensor in the embodiment of the present invention is 40mA.

[0096] The current sensor provided in this embodiment is resistant to power frequency vibration caused by an exciter or the like. Specifically, an exciter is used to drive the bottom of the sensor to vibrate continuously to simulate external vibration interference, and the frequency is set to 50 Hz. The output response waveform curve generated by the first magneto-mechanical composite unit and the second magneto-mechanical composite unit in the current sensor to the 50 Hz vibration is recorded and obtained by the Scope function module in the phase-locked amplifier, such as Figure 6 The curve corresponding to device1 is the output response waveform curve of the first magneto-mechanical composite unit, and the curve corresponding to device2 is the output response waveform curve of the second magneto-mechanical composite unit. Figure 6 The amplitudes of the first magneto-mechanical composite unit and the second magneto-mechanical composite unit are 481.3mV and 453.6mV respectively, with an amplitude difference of only 27.7mV and a phase difference of 1 / 2 cycle. The output response and value of the first magneto-mechanical composite unit and the second magneto-mechanical composite unit to interference at the same time are a fixed value, indicating that the differential signal output by the current sensor of this embodiment can offset the vibration interference of the external environment.

[0097] The current sensor provided in this embodiment has a certain degree of anti-interference to the interference wire far away from the cavity. Specifically, a 5A interference wire is placed at different positions around the cavity to test the output response waveform curve generated by the first magnetomechanical composite unit and the second magnetomechanical composite unit to the interference wire. The results are as follows: Figure 7-10 shown.

[0098] like Figure 7 As shown in (a), when the interference wire is located at the first position of the current sensor, that is, the interference wire is parallel to the thickness direction of the magnetic focusing ring and is placed on the side of a magnetomechanical composite unit, the output response waveform curves of the first magnetomechanical composite unit and the second magnetomechanical composite unit are as follows: Figure 7 (b) As shown. Figure 7 (b) The output response phases of the first magneto-electromechanical composite unit and the second magneto-electromechanical composite unit differ by 1 / 2 cycle, and the amplitudes differ greatly, indicating that the differential signal of the current sensor of the embodiment has a weaker anti-interference effect on the interference wire at the first position.

[0099] like Figure 8 As shown in (a), when the interference wire is located at the second position of the current sensor, that is, the interference wire is perpendicular to the thickness direction of the magnetic focusing ring and is placed on the sides of the two magnetomechanical composite units, the output response waveform curves of the first magnetomechanical composite unit and the second magnetomechanical composite unit to the interference wire are as follows: Figure 8 (b) As shown. Figure 8 (b) The output response phases of the first magneto-electromechanical composite unit and the second magneto-electromechanical composite unit differ by 1 / 2 cycle, and their amplitudes are close, indicating that the interfering wire produces similar interference to the first magneto-electromechanical composite unit and the second magneto-electromechanical composite unit, and that the differential signal of the current sensor of the embodiment has a certain anti-interference effect on the interfering wire at the first position.

[0100] like Fig. 9 As shown in (a), when the interference wire is located at the third position of the current sensor, that is, the interference wire is perpendicular to the thickness direction of the magnetic focusing ring and is placed on the top side of the two magnetomechanical composite units, the output response waveform curves of the first magnetomechanical composite unit and the second magnetomechanical composite unit to the interference wire are as follows: Fig. 9 (b) As shown. Fig. 9 (b) The output response phases of the first magneto-electromechanical composite unit and the second magneto-electromechanical composite unit differ by 1 / 2 cycle, and their amplitudes are close, indicating that the differential signal of the current sensor of the embodiment has a certain anti-interference effect on the interference wire at the third position.

[0101] like Fig.10As shown in (a), when the interference wire is located at the fourth position of the current sensor, that is, the interference wire is parallel to the thickness direction of the magnetic focusing ring and is placed on the top side of the two magnetomechanical composite units, the output response waveform curves of the first magnetomechanical composite unit and the second magnetomechanical composite unit are as follows: Fig.10 (b) As shown. Fig.10 (b) The output response phases of the first magneto-electromechanical composite unit and the second magneto-electromechanical composite unit are the same and the amplitudes are close, indicating that the differential signal of the current sensor of this embodiment has a weaker anti-interference effect on the interference wire at the fourth position and is greatly affected by the interference signal.

[0102] The above measurement results show that when the interference wire is perpendicular to the thickness direction of the magnetic ring and far away from the cavity, the current sensor has a better anti-interference effect on the interference wire; when the interference wire is parallel to the thickness direction of the magnetic ring and far away from the cavity, the current sensor has a weaker anti-interference effect on the interference wire.

[0103] The current sensor of the embodiment of the present invention has anti-interference performance against interference wires that are more than 10 cm away from the cavity. When the 5A interference wire is in the first position of the current sensor, that is, parallel to the thickness direction of the magnetic focusing ring and placed on the side of a magneto-mechanical composite unit, the output response change curves of the first magneto-mechanical composite unit and the second magneto-mechanical composite unit in the range of 0 to 10 cm away from the cavity are as follows: Fig.11 The curves corresponding to difierent devices1 and different device2 are the output response change curves of the first magneto-mechanical composite unit and the second magneto-mechanical composite unit at different distances, and the curve corresponding to Total ouput is the differential signal change curve. When there is no interference from the interfering wire, the output signal amplitude of a single magneto-mechanical composite unit is 222mV, and the amplitude of the differential signal is 444mV. Fig.11 As the distance increases, the amplitude of the magneto-mechanical composite unit gradually approaches, the influence of interference on the differential signal gradually decreases, and when the distance is 9-10cm, the interference signal tends to a fixed value. When the distance is 10cm, the amplitude of the output response signal differs from that of the output response signal without interference wire by only 4.5mV, and the influence of the interference signal is greatly improved.

[0104] When the 5A interference wire is in the fourth position of the current sensor, that is, parallel to the thickness direction of the magnetic focusing ring and away from the top side of the two magnetomechanical composite units, the output response change curves of the first magnetomechanical composite unit and the second magnetomechanical composite unit in the range of 0 to 10 cm are as follows: Fig.12The curve corresponding to difierent devices 1 is the output response curve of the first magneto-mechanical composite unit at different distances. When there is no interference from the interfering wire, the output signal amplitude of a single magneto-mechanical composite unit is 222mV. Fig.12 As the distance increases, the amplitude of the magneto-mechanical composite unit gradually approaches, and the influence of interference on the differential signal gradually decreases. When the distance is 10 cm, the output response signal amplitude (226mV) is only 4mV different from the output response signal amplitude (222mV) when there is no interference wire. The interference effect of the interference wire on the current sensor is greatly improved.

[0105] Therefore, the current sensor of the embodiment of the present invention can be used for low-frequency current measurement of 50 Hz, and has high sensitivity, good resistance to vibration interference, good high sensitivity and good resistance to external environment interference.

[0106] The embodiment of the present invention also provides a method for preparing the above-mentioned current sensor.

[0107] The preparation method of the embodiment of the present invention includes: S100: taking a piezoelectric material and an elastic material, and making them into a piezoelectric layer and an elastic layer respectively; specifically, processing the piezoelectric material and the elastic material into a cuboid respectively, and then ultrasonically cleaning them with pure water to obtain the piezoelectric layer and the elastic layer.

[0108] Preferably, the elastic layer has a length of 2 cm, a width of 3 mm, and a thickness of 0.2 mm; the piezoelectric layer has a length of 2 cm, a width of 3 mm, and a thickness of 0.2 mm.

[0109] S200: depositing electrodes on the upper surface and the lower surface of the piezoelectric layer respectively, and polarizing the piezoelectric layer in a thickness direction to obtain a first composite layer;

[0110] Specifically, the two surfaces of the piezoelectric layer are annealed, electrodes are deposited, and thickness polarization is performed, and wires are led out at the two electrode positions. The electrode deposition step can be evaporation, magnetron sputtering or other deposition methods, which are not specifically limited.

[0111] S300: laminating and bonding the first composite layer and the elastic layer to obtain a second composite layer;

[0112] Specifically, the piezoelectric material is adhered to the side of the spring steel by an adhesive.

[0113] S400: placing permanent magnetic blocks on both sides of the first end of the second composite layer to obtain a magnetomechanical composite unit;

[0114] Specifically, two square permanent magnets of the same size are placed on two sides of one end of the second composite layer. Preferably, the permanent magnets are square with a side length of 3 mm.

[0115] S500: placing two U-shaped magnetic focusing rings in the base, so that the openings of the first magnetic focusing ring and the second magnetic focusing ring are arranged opposite to each other, forming a cavity and a first air gap position and a second air gap position located on both sides of the cavity;

[0116] S600: fixing the two magnetomechanical composite units to the two end surfaces of the second magnetic focusing ring respectively, wherein the thickness direction of the piezoelectric layer in the two magnetomechanical composite units is parallel to the thickness direction of the magnetic focusing ring;

[0117] S700: electrically coupling two electrodes located on the same side of two magneto-mechanical composite units;

[0118] S800: collecting output signals of two electrodes located on the other side of the two magneto-electromechanical composite units.

[0119] Specifically, the differential signal is outputted by the two electrodes on the other side. The two electrodes are electrically coupled to the signal processing module, and then the signal processing module outputs a current value of the conductor to be tested corresponding to the differential signal.

[0120] The embodiment of the present invention further provides a sensor device, which at least includes the above-mentioned current sensor and the current sensor manufactured by the above-mentioned manufacturing method.

[0121] Therefore, an embodiment of the present invention provides a current sensor, a sensing device and a preparation method thereof, wherein the current sensor includes two U-shaped symmetrically arranged magnetic focusing rings, whose openings are arranged opposite to each other, forming a cavity for accommodating the conductor to be measured and a first air gap position and a second air gap position; two magnetomechanical composite units, which are respectively located at the first air gap position and the second air gap position, and are respectively fixedly connected to the two end faces of the second magnetic focusing ring, for sensing the external magnetic field around the conductor to be measured and generating opposite longitudinal vibrations in the direction perpendicular to the two end faces, and outputting differential signals; a substrate, for supporting the two magnetic focusing rings. The present invention realizes non-contact measurement of low-frequency current through the synergistic effect of the magnetomechanical composite unit and the magnetic focusing ring, and has the characteristics of low energy consumption, strong anti-interference, high sensitivity, and easy implementation.

[0122] It should be understood that the above is only an example and does not constitute any limitation on the technical solution of the present invention. In specific applications, technicians in this field can make settings as needed, and the present invention does not limit this.

[0123] It should be noted that the workflow described above is merely illustrative and does not limit the scope of protection of the present invention. In practical applications, technicians in this field can select part or all of them according to actual needs to achieve the purpose of the present embodiment, and no limitation is made here.

Claims

1. A current sensor, characterized in that: include: Two U-shaped symmetrical magnetic focusing rings, wherein the openings of the first magnetic focusing ring and the second magnetic focusing ring are arranged opposite to each other, forming a cavity for accommodating the wire to be tested and a first air gap position and a second air gap position located on both sides of the cavity; Two magneto-mechanical composite units of the same structure, wherein the first magneto-mechanical composite unit and the second magneto-mechanical composite unit are respectively located at the first air gap position and the second air gap position and are respectively fixedly connected to the two end faces of the second magnetic focusing ring, and are used to sense the external magnetic field around the conductor to be tested and generate opposite longitudinal vibrations in the direction perpendicular to the two end faces, and output differential signals; A signal processing module, used for outputting the current value of the conductor to be tested according to the differential signal; A base, used for supporting the first magnetic focusing ring and the second magnetic focusing ring; The magneto-mechanical composite unit comprises a first electrode, a second electrode, and a first permanent magnet block, an electromechanical composite layer, and a second permanent magnet block arranged in sequence along a first direction; the first direction is parallel to the thickness direction of the magnetic focusing ring; The first permanent magnet block and the second permanent magnet block are magnetically adsorbed on both sides of the free end of the electromechanical composite layer; The electromechanical composite layer comprises a piezoelectric layer and an elastic layer which are stacked; The elastic layer, the first electrode, the piezoelectric layer and the second electrode are arranged in sequence along the first direction; The first permanent magnet block and the second permanent magnet block can generate the longitudinal vibration approaching or moving away from the second magnetic focusing ring under the action of the external magnetic field.

2. The current sensor according to claim 1, characterized in that: The first electrode in the first magneto-mechanical composite unit is electrically coupled to the first electrode in the second magneto-mechanical composite unit, and the signal processing module is electrically coupled to the second electrode in the first magneto-mechanical composite unit and the second electrode in the second magneto-mechanical composite unit respectively; or, The second electrode in the first magneto-mechanical composite unit is electrically coupled to the second electrode in the second magneto-mechanical composite unit, and the signal processing module is electrically coupled to the first electrode in the first magneto-mechanical composite unit and the first electrode in the second magneto-mechanical composite unit respectively.

3. The current sensor according to claim 1, characterized in that: The resonance frequency of the first permanent magnet block and the second permanent magnet block is 50 Hz.

4. The current sensor according to claim 1, characterized in that: The elastic layer is spring steel; The magnetic focusing ring is made of Permalloy; The piezoelectric layer is a piezoelectric single crystal, a piezoelectric ceramic or a piezoelectric polymer; The first permanent magnet block and the second permanent magnet block are square permanent magnets.

5. The current sensor according to claim 4, characterized in that: The elastic layer is made of 304 stainless steel; The material of the piezoelectric layer is AlN, quartz, LiNbO3, BaTiO3, ZnO, Pb(Zr,Ti)O3, Pb(Mg,Nb)O3-PbTiO3, Pb(Zn, Nb)O3-PbTiO3 or BiScO3-PbTiO3; The material of the magnetic focusing ring is 1J85; The first permanent magnet block and the second permanent magnet block are made of neodymium iron boron.

6. The current sensor according to claim 1, characterized in that: The elastic layer has a length of 1.8-2.5 cm, a width of 2.6-4 mm, and a thickness of 0.15-0.3 mm; The piezoelectric layer has a length of 1.8-2.5 cm, a width of 2.6-4 mm, and a thickness of 0.15-0.3 mm; The permanent magnet block is a square block with a side length of 2.6-4 mm.

7. The current sensor according to claim 1, characterized in that: The base comprises a first supporting surface and a second supporting surface; The first supporting surface is arranged at a side of the first magnetic focusing ring close to the second magnetic focusing ring, and is used to support the first magnetic focusing ring; the first magnetomechanical composite unit and the second magnetomechanical composite unit are away from the first supporting surface; The second supporting surface is arranged on a side of the second magnetic focusing ring away from the cavity, and is used for supporting the second magnetic focusing ring.

8. A method for preparing a current sensor, characterized in that: The current sensor is a current sensor according to any one of claims 1 to 7; and the preparation method comprises: Taking a piezoelectric material and an elastic material, and making them into a piezoelectric layer and an elastic layer respectively; Depositing electrodes on the upper surface and the lower surface of the piezoelectric layer respectively, and polarizing the piezoelectric layer in a thickness direction to obtain a first composite layer; Laminating and bonding the first composite layer and the elastic layer to obtain a second composite layer; Permanent magnetic blocks are respectively placed on both sides of the first end of the second composite layer to obtain a magneto-mechanical composite unit; Placing two U-shaped magnetic focusing rings in the base, so that the openings of the first magnetic focusing ring and the second magnetic focusing ring are arranged opposite to each other, forming a cavity and a first air gap position and a second air gap position located on both sides of the cavity; The first magneto-mechanical-electrical composite unit and the second magneto-mechanical-electrical composite unit of the two magneto-mechanical-electrical composite units are respectively fixedly connected to the first end face and the second end face of the two end faces of the second magnetic focusing ring, wherein the thickness direction of the piezoelectric layer in the two magneto-mechanical-electrical composite units is parallel to the thickness direction of the magnetic focusing ring; electrically coupling two electrodes located on the same side of the first magneto-electromechanical composite unit and the second magneto-electromechanical composite unit; The output signals of two electrodes located at the other side of the first magneto-electromechanical composite unit and the second magneto-electromechanical composite unit are collected.

9. A sensing device, characterized in that: including a current sensor; The current sensor is the current sensor according to any one of claims 1 to 8.

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