CN102043083A

CN102043083A - Giant magnetoresistance array current sensor

Info

Publication number: CN102043083A
Application number: CN 201010560952
Authority: CN
Inventors: 辛守乔; 肖立业; 张国民; 戴少涛; 邱清泉; 刘怡; 许熙
Original assignee: Institute of Electrical Engineering of CAS
Current assignee: Institute of Electrical Engineering of CAS
Priority date: 2010-11-23
Filing date: 2010-11-23
Publication date: 2011-05-04
Anticipated expiration: 2030-11-23
Also published as: CN102043083B

Abstract

The invention relates to a giant magnetoresistance array current sensor comprising a giant magnetoresistance chip sub-board array (1), an annular mother PCB (printed circuit board) (2), an eight-channel amplifier circuit (3), an eight-channel sampling retaining and A/D (analog to digital) conversion circuit (4) and a FPGA (field programmable gate array) signal processing circuit (5). The giant magnetoresistance chip sub-board array (1) comprises a giant magnetoresistance chip AA005-02 and two strip-shaped aluminum-nickel-cobalt permanent magnets, wherein the aluminum-nickel-cobalt permanent magnets are arranged on two ends of the giant magnetoresistance chip AA005-02, and the magnetizing direction of the strip-shaped aluminum-nickel-cobalt permanent magnets is consistent with the magnet-sensing direction of the giant magnetoresistance chip AA005-02; eight giant magnetoresistance chip sub-boards are arranged on the annular mother PCB (2); the voltage signals outputted by the giant magnetoresistance chip AA005-02 are inputted into the eight-channel amplifier circuit (3), and then the voltage signals are amplified and made to enter the eight-channel sampling retaining and A/D conversion circuit (4); and the simulated voltage signals are converted into digital signals, and then the eight-way digital signals are processed by the FPGA signal processing circuit (5).

Description

A kind of giant magnetoresistance array current sensor

Technical field

The present invention relates to a kind of intelligence sensor, particularly the giant magnetoresistance array is surveyed current sensor.

Background technology

For improving the access of the suitable regenerative resource of utilization efficiency of energy, present electrical network develops to the intelligent grid direction that with Based Intelligent Control, management and analysis is the flexible strain of feature just gradually, and this carries out real-time monitoring with regard to needing various sensors to the parameters such as ruuning situation of electric current, voltage, temperature and the power equipment of power network line.

Wherein, accurately detecting in real time of electric current is one of vital task in numerous measurement of electric parameter.In more than 100 year of power system development, traditional current transformer is playing the important and pivotal role aspect current detecting and the relay protection, but along with the continuous expansion of electrical network scale, continuous rising and the access of renewable new forms of energy electrical network and the construction of digital transformer substation of electric pressure, traditional current transformer more and more exposes numerous deficiencies, such as: 1. volume is increasing, waste too much electrical material, increased cost and be difficult for installation; 2. there is the Secondary Winding high-tension danger of opening a way; 3. lack digital interface and intelligent analysis function, be difficult to adapt to the development need of intelligent grid.

In order to remedy the deficiency of conventional current mutual inductor, over past ten years, scientific research personnel both domestic and external studies various novel electronic formula current transformers.The focus of research mainly concentrates on Luo-coil current transformer and block optical current mutual inductor and pure optical fiber current mutual inductor.The method that Luo-coil is measured electric current is the technology of comparative maturity at present, and precision can reach more than 0.2 grade, and has begun large-scale production and application.But because Luo-coil is measured electric current is according to Faraday's electromagnetic induction law, therefore can only be used to exchange the measurement with pulse current, is helpless for the measurement of DC current.Pure optical current mutual inductor is the most attractive a kind of current transformer, and its principle is according to Faraday effect.Divide from structure, optical current mutual inductor can be divided into block and two kinds of pure optical fiber current mutual inductors.Pure optical fiber current mutual inductor advantage is simple in structure, and an optical fiber is realized the sensing and the two kinds of functions of communicating by letter simultaneously, but owing to be subjected to the influence of temperature and mechanical deformation very big, its stability and precision also are difficult to guarantee; Block optical current mutual inductor proposes for the deficiency that remedies pure optical fiber current mutual inductor, relative optical fiber, and the temperature coefficient of block glass is little, and mechanical property is strong, and measurement effect is better, but block glass is difficult for the worker.In fact, no matter be bulk or pure optical fiber current mutual inductor, the cost height is common shortcoming.Because need stable light source, need optical signal processing device, the cost of these devices is that most of enterprise is difficult to accept.

Magnetosensitive device is the element relatively more responsive to magnetic field intensity, mainly is divided into several types such as Hall, anisotropic magnetoresistance, giant magnetoresistance effect at present.Utilize magnetoresistance device that the indirect measurement of the measurement realization electric current in magnetic field has been remedied the not defective of energy measurement direct current of sufficient Luo-coil; The production in enormous quantities of magnetosensitive device simultaneously makes it with low cost, and metastable performance also makes it be widely used.

Survey in the sensor of electric current at the magnetosensitive device array, mostly adopt magnetic resistance and Hall element.Since little between the general magnetic resistance and the linear zone of Hall element, be fit to the measurement of medium and small electric current.Giant magnetoresistance is the research focus in material field in recent years, compares with other magnetosensitive device, and the sensitivity of giant magnetoresistance is higher, and temperature stability is good, and is wide between linear zone.The AA series of comparisons that at present commercial simulation giant magnetoresistance magnetic force chip has only U.S. NVE company to produce is stable, but no matter the direction in magnetic field is negative just, and the output of giant magnetoresistance all is one pole.

Summary of the invention

The objective of the invention is to overcome the shortcoming of existing Luo-coil electronic current mutual inductor, propose a kind of sensor that utilizes giant magnetoresistance array measurement electric current, realizing the same brake of alternating current-direct current, and can finish information the digitizing transmission, store.

To achieve these goals, the technical solution used in the present invention is as follows:

The present invention is by installing the method for permanent magnet at the two ends of giant magnetoresistance chip, a bias magnetic field is provided, bias magnetic field output offset voltage in the time of the giant magnetoresistance chip power, when magnetic field superposition that tested electric current produces is on bias magnetic field, the output voltage of giant magnetoresistance chip is the voltage that is produced by the magnetic field of tested electric current generation that superposeed again on the basis of former bias voltage, through follow-up signal processing circuit bias voltage is reduced, just obtain the voltage of a bipolar output, also promptly output has negative voltage is just arranged.Because what the giant magnetoresistance chip was measured is magnetic field, is that DC current or alternating current all can produce magnetic field,, just possessed the function of alternating current-direct current with survey so just can not only measure direct current but also can measure and exchanged by measuring magnetic field.

The present invention includes giant magnetoresistance chip daughter board array, PCB motherboard, 8 channel voltage amplifier circuits, the maintenance of 8 channel sample and A/D change-over circuit, FPGA treatment circuit.Giant magnetoresistance chip daughter board array is made of 8 giant magnetoresistance daughter boards.Each daughter board is made of the Al-Ni-Co permanent magnet of a slice giant magnetoresistance chip AA005-02 and two bar shapeds, two described permanent magnets place the two ends of giant magnetoresistance chip AA005-02 respectively, and the magnetizing direction of permanent magnet is consistent with the magnetosensitive sense direction of giant magnetoresistance chip AA005-02.8 giant magnetoresistance chip daughter board arrays evenly are installed on the PCB motherboard of annular with identical radius and equal angles.The voltage signal of giant magnetoresistance chip output is input in the 8 channel voltage amplifier circuits, after amplifying, enter 8 channel sample and keep and the A/D change-over circuit, the voltage signal of simulation is transformed into digital signal, through the FPGA treatment circuit 8 way word signals is carried out parallel type again and handles.

Giant magnetoresistance chip daughter board of the present invention is made of the AA005-02 of NVE company and the casting aluminium nickel cobalt LNGT18 permanent magnet of two bar shapeds, and magnetizing direction is along thickness direction, and promptly magnetizing direction is perpendicular to long and the wide plane that constitutes.For bias magnetic field being provided for the giant magnetoresistance chip, two strip permanent magnets place the two ends of chip, the size adjustment of the bias-field that concrete distance can provide as required according to identical pole orientation.

Ring-shaped P CB motherboard of the present invention is used for installing and fixing giant magnetoresistance chip daughter board, and tested current bus bar is passed by interior circle.

Voltage amplifier circuit of the present invention is made of two four-way rail-to-rail amplifier LTC6085.Be used to receive the voltage output signal of giant magnetoresistance chip daughter board array.

Sampling of the present invention keeps and the A/D change-over circuit, and MAX155 constitutes by a slice, is used for the voltage output signal of the anterior amplifier circuit of synchronous acquisition, and the digital signal after will changing with the parallel way of output is given the FPGA processor at rear portion.

FPGA signal processing circuit of the present invention is made of a slice Cyclone III/EP3C10E144.

The voltage signal of giant magnetoresistance chip daughter board array output is input in the voltage amplifier circuit, entering sampling through the voltage signal after sending out greatly keeps and the A/D change-over circuit, voltage signal by simulation is transformed into digital signal, enter the FPGA signal processing circuit then each way word signal parallel, finally calculate according to the measurement of finishing bus current based on the discrete Fourier transform (DFT) in space.

The present invention compared with prior art has following advantage:

1) the giant magnetoresistance chip daughter board that the present invention proposes is biased has been realized the bipolar output of output signal, and just output signal just has, and has negatively, makes the measurement of positive counter magnetic field be achieved;

2) the giant magnetoresistance chip array of the present invention's proposition has been realized alternating current-direct current with the function of surveying, and cooperates certain algorithm to weaken the magnetic interference that the through-flow lead of space parallel produces;

3) adopt FPGA as signal processing unit among the present invention, the multichannel transducing signal has been realized parallel processing mode, broken through the instruction type of traditional MCU, DSP etc. fully and handled, improved the real-time that detects.

Description of drawings

Below in conjunction with the drawings and specific embodiments, the invention will be further described.

Fig. 1 is the structural principle block diagram of giant magnetoresistance array current sensor;

Magnetic line of force distribution plan when distance is 6mm between two strip permanent magnets of Fig. 2;

The magnetic field intensity range value of each point and each component value figure on the vertical axis of symmetry of Fig. 3 permanent magnet;

Fig. 4 giant magnetoresistance chip daughter board structural representation;

Fig. 5 is the wiring layout of giant magnetoresistance chip daughter board array on ring-shaped P CB motherboard;

Fig. 6 is the connection layout of 8 giant magnetoresistance chip daughter boards and voltage amplifier LTC6085;

Fig. 7 is the connection layout of voltage amplifier LTC6085 and sampling maintenance and A/D converter MAX155;

Fig. 8 is the connection layout of sampling maintenance and A/D converter MAX155 and FPGA processor EP3C10.

Embodiment

Fig. 1 is a theory structure block diagram of the present invention.As shown in Figure 1, the present invention includes: giant magnetoresistance chip daughter board array 1,

PCB motherboard

2,8 channel

voltage amplifier circuits

3,8 channel sample of annular keep and A/D change-over circuit 4, FPGA treatment circuit 5.Giant magnetoresistance chip daughter board array 1 is made of 8 giant magnetoresistance daughter boards.Each daughter board is made of the Al-Ni-Co permanent magnet of a slice giant magnetoresistance chip AA005-02 and two bar shapeds, two strip permanent magnets place the two ends of giant magnetoresistance chip AA005-02 respectively, and the magnetizing direction of permanent magnet is consistent with the magnetosensitive sense direction of giant magnetoresistance chip AA005-02.8 giant magnetoresistance daughter boards are with on the PCB motherboard 2 that is evenly distributed in annular with identical radius and equal angles, after the voltage signal of its output amplifies through 8 channel voltage amplifier circuits 3, enter the conversion that maintenance of 8 channel sample and A/D change-over circuit 4 are realized simulating signals and digital signal.Digital signal after the conversion enters the measurement calculating that FPGA treatment circuit 5 is finished bus current.

Described giant magnetoresistance chip daughter board array 1 is to be made of 8 giant magnetoresistance chip daughter boards, be welded on the PCB motherboard 2 of annular with identical radius and angle between 8 giant magnetoresistance chip daughter boards, the transducing part of forming this giant magnetoresistance array intelligence current sensor, as shown in Figure 5.

The annular motherboard 2 of present embodiment is r=9cm by an inside radius, and external radius is that the pcb board of D=11cm constitutes.

Described 8 channel voltage amplifier circuits 3 are made of two amplifier LTC6085, and two amplifiers are parallel waies, and except power supply and ground end were parallel with one another, other leads ends did not link to each other.As shown in Figure 6, the V+ of 8 giant magnetoresistance chips end is unified to be connect+5V voltage, the unified ground connection of V-end.The Out+ termination first amplifier LTC6085 of No. 1 giant magnetoresistance chip+the INA end, the Out+ termination first amplifier LTC6085 of No. 2 giant magnetoresistance chip+the INB end, the Out+ termination first amplifier LTC6085 of No. 3 giant magnetoresistance chip+the INC end, the Out+ termination first amplifier LTC6085 of No. 4 giant magnetoresistance chip+the IND end.The Out-termination first amplifier LTC6085 of No. 1 giant magnetoresistance chip-the INA end, the Out-termination first amplifier LTC6085 of No. 2 giant magnetoresistance chip-the INB end, the Out-termination first amplifier LTC6085 of No. 3 giant magnetoresistance chip-the INC end, the Out-termination first amplifier LTC6085 of No. 4 giant magnetoresistance chip-the IND end.The Out+ termination second amplifier LTC6085 of No. 5 giant magnetoresistance chip+the INA end, the Out+ termination second amplifier LTC6085 of No. 6 giant magnetoresistance chip+the INB end, the Out+ termination second amplifier LTC6085 of No. 7 giant magnetoresistance chip+the INC end, the Out+ termination second amplifier LTC6085 of No. 8 giant magnetoresistance chip+the IND end; The Out-termination second amplifier LTC6085 of No. 5 giant magnetoresistance chip-the INA end, the Out-termination second amplifier LTC6085 of No. 6 giant magnetoresistance chip-the INB end, the Out-termination second amplifier LTC6085 of No. 7 giant magnetoresistance chip-INC, the Out-termination second amplifier LTC6085 of No. 8 giant magnetoresistance chip-the IND end.

Described 8 channel sample keep and A/D change-over circuit 4 is made of chip MAX155.The simulating signal of two LTC6085 amplifier outputs becomes digital signal through chip MAX155 sampling and quantification.As shown in Figure 7, the V+ of first, second two amplifier LTC6085 termination+5V voltage, V-termination-5V voltage.The OUTC end that the AINO that the OUTA end of the first amplifier LTC6085 is connected to MAX155 holds, the OUTB end of the first amplifier LTC6085 is connected to the AIN1 end of MAX155, the first amplifier LTC6085 is connected to the AIN2 end of MAX155, the OUTD of the first amplifier LTC6085 holds the AIN3 end that is connected to MAX155; The OUTC end that the AIN4 that the OUTA end of the second amplifier LTC6085 is connected to MAX155 holds, the OUTB end of the second amplifier LTC6085 is connected to the AIN5 end of MAX155, the second amplifier LTC6085 is connected to the AIN6 end of MAX155, the OUTD of the second amplifier LTC6085 holds the AIN7 end that is connected to MAX155.

Described FPGA treatment circuit 5 is made of the EP3C10E144 of cyclone III series, receives the digital signal from sampling maintenance and A/D change-over circuit 4.The D0/A0 end of MAX155 is connected to the IO of FPGA, the DIFFIO_B9p end, the D1/A1 end of MAX155 is connected to the IO of FPGA, the DIFFIO_B9n end, the D2/A2 end of MAX155 is connected to the IO of FPGA, the DIFFIO_B10p end, the D3/PD end of MAX155 is connected to the IO of FPGA, the DIFFIO_B11p end, the D4/INH end of MAX155 is connected to the IO of FPGA, the DIFFIO_B11n end, the D5/BIP end of MAX155 is connected to the IO of FPGA, the DIFFIO_B12p end, the D6/DIFF end of MAX155 is connected to the IO of FPGA, the DIFFIO_B12n end, the D7/ALL end of MAX155 is connected to IO, the DIFFIO_B15p end.The VDD of MAX155 connects+5V, and Vss connects-5V, DGND and AGND ground connection, and REFIN and REFOUT end link together and pass through capacitor C ground connection.As shown in Figure 8.

What giant magnetoresistance chip daughter board array adopted is sensing technology on the plate, is distributed in the PCB motherboard of annular with 45 degree equal angles by 8 giant magnetoresistance chip daughter boards.When the present invention worked, tested lead passed from the interior geometry of the circle center of ring-shaped P CB motherboard.Because the magnetic field intensity measured chip that AA005-02 is a kind of one pole to be exported is (that is: under the effect of alternating magnetic field, its output only changes toward the direction), when magnetic field was alternating magnetic field, the output voltage of AA005-02 but can only be the voltage of one pole output.Therefore the present invention has placed strip permanent magnet at the two ends of giant magnetoresistance chip, and for it provides a constant bias magnetic field, magnetizing direction is parallel with the sensitive axes direction of giant magnetoresistance chip.When magnetic field superposition that tested electric current produces was on giant magnetoresistance chip AA005-02, the voltage of its generation will be superimposed upon on the initial bias voltage.The voltage of the output of giant magnetoresistance chip variation at this moment is exactly the variation on the bias voltage basis.In the FPGA treatment circuit 5 this bias voltage is deducted in the back, just obtain the bipolar output characteristics of giant magnetoresistance chip.The physical dimension of the strip permanent magnet among the present invention is: long: 6mm, wide: 1.5mm, thick: 1mm, towards magnetic direction along thickness direction.The spacing of two magnets is at least greater than the length of giant magnetoresistance chip, the bias-field intensity adjustments that concrete numerical value can be as required.

The inside radius of the PCB motherboard 2 of annular is r=9cm, and external radius is D=11cm, and the distance of mounting points and motherboard central point is L=10cm.Have 8 daughter board mounting points on the ring-shaped P CB motherboard 2, successively on the anchor ring of the motherboard of equal angles distribution.

8 channel voltage amplifier circuits 3 are made of two four-way rail-to-rail amplifier LTC6085, and 8 outputs of giant magnetoresistance chip daughter board array all are connected to LTC6085 with differential mode.Because signal in the transmission from the sensing element to the Signal Processing Element, produces stray capacitance and inductance inevitably on lead on pcb board, this will produce additional voltage---common mode voltage in amplifier input terminal.In order farthest to reduce the interference of common mode voltage, must all be connected into the difference-mode input mode.

The direct MAX1554 of the output of amplifier, MAX155 are a 8 analog to digital converters of 8 passages that integrate synchronized sampling maintenance and A/D translation function, and its conversion figure place can require freely select according to measuring accuracy.Synchronized sampling has guaranteed the phase-locking of 8 tunnels analogy voltages, is that the FPGA treatment circuit carries out the basis that Measurement Algorithm is optimized.The output of MAX155 is 8 position digital signals that walk abreast, and therefore can directly be connected with any 8 I/O mouths of FPGA, it should be noted that whether both physical electrical signals mate, and does not then need level conversion if match.

The FPGA treatment circuit adopts the Cyclone family chip of ALTERA company, mainly finishes Signal Processing.Can be divided into four parts according to function: channel allocation, the pre-service of A/D translation data (eliminate bias, temperature and sluggish compensation etc.), Measurement Algorithm optimization (variation of space Fourier) and output control module (numeral and simulation output).

Claims

1. giant magnetoresistance array current sensor is characterized in that: described sensor by giant magnetoresistance chip daughter board array (1), ring-shaped P CB motherboard (2), 8 channel amplifier circuit (3), 8 channel sample keep and A/D change-over circuit (4), FPGA signal processing circuit (5) constitute; Giant magnetoresistance chip daughter board array (1) is made of 8 giant magnetoresistance daughter boards, each giant magnetoresistance daughter board is made of the Al-Ni-Co permanent magnet of a slice giant magnetoresistance chip AA005-02 and two bar shapeds, two strip permanent magnets place the two ends of giant magnetoresistance chip AA005-02 respectively, and the permanent magnet magnetizing direction is consistent with the magnetosensitive sense direction of giant magnetoresistance chip AA005-02; Giant magnetoresistance chip daughter board array is installed on the ring-shaped P CB motherboard (2), the voltage signal of described giant magnetoresistance chip daughter board array (1) output is input in the 8 channel voltage amplifier circuits (3), after amplifying, entering 8 channel sample keeps and A/D change-over circuit (4), the voltage signal of simulation is transformed into digital signal, passes through FPGA treatment circuit (5) again 8 way word signals are handled.

2. giant magnetoresistance array current sensor as claimed in claim 1 is characterized in that, described 8 giant magnetoresistance chip daughter boards are distributed on the PCB motherboard (2) with identical radius and angle same.

3. giant magnetoresistance array current sensor as claimed in claim 1 is characterized in that, described 8 channel amplifier circuit (3) are made of two LTC6085; The Out+ end of first giant magnetoresistance chip in the giant magnetoresistance chip daughter board array (1) is connected to first LTC6085's+the INA end; The Out-end is connected to first LTC6085's-the INA end; The Out+ end of second giant magnetoresistance chip is connected to first LTC6085's+the INB end; The Out-end is connected to first LTC6085's-the INB end; The Out+ end of the 3rd giant magnetoresistance chip is connected to first LTC6085's+the INC end; The Out-end is connected to first LTC6085's-the INC end; The Out+ end of the 4th giant magnetoresistance chip is connected to first LTC6085's+the IND end; The Out-end is connected to first LTC6085's-the IND end; The Out+ end of the 5th giant magnetoresistance chip is connected to second LTC6085's+the INA end; The Out-end is connected to second LTC6085's-the INA end; The Out+ end of the 6th giant magnetoresistance chip is connected to second LTC6085's+the INB end; The Out-end is connected to second LTC6085's-the INB end; The Out+ end of the 7th giant magnetoresistance chip is connected to second LTC6085's+the INC end; The Out-end is connected to second LTC6085's-the INC end; The Out+ end of the 8th giant magnetoresistance chip is connected to second LTC6085's+the IND end; The Out-end is connected to second LTC6085's-the IND end.

4. giant magnetoresistance array current sensor as claimed in claim 1 is characterized in that, described 8 channel sample keep and A/D change-over circuit (4) is made of a slice MAX155; The OUTA of first amplifier chip LTC6085 terminates at the AIN0 end of MAX155, and OUTB terminates at the AIN1 end of MAX155, and OUTC terminates at the AIN2 end of MAX155, and OUTD terminates at the AIN3 end of MAX155; The OUTA of second amplifier chip LTC6085 terminates at the AIN4 end of MAX155, and OUTB terminates at the AIN5 end of MAX155, and OUTC terminates at the AIN6 end of MAX155, and OUTD terminates at the AIN7 end of MAX155.

5. giant magnetoresistance array current sensor as claimed in claim 1 is characterized in that described FPGA signal processing circuit (5) is made of a slice Cyclone III/EP3C10E144, is used for accepting the digital signal of MAX155 output; The D0/A0 of MAX155 is connected to the IO of EP3C10E144, DIFFIO_B9p, D1/A1 is connected to the IO of EP3C10E144, DIFFIO_B9n, D2/A2 is connected to the IO of EP3C10E144, DIFFIO_B10p, D3/A3 are connected to the IO of EP3C10E144, DIFFIO_B11p, D4/INH is connected to the IO of EP3C10E144, DIFFIO_B11n, D5/BIP are connected to the IO of EP3C10E144, DIFFIO_B12p, D6/DIFF is connected to the IO of EP3C10E144, DIFFIO_B12n, D7/ALL are connected to the IO of EP3C10E144, DIFFIO_B15p.

6. method that adopts the described giant magnetoresistance array current of claim 1 sensor measurement electric current, it is characterized in that, provide a bias magnetic field by described permanent magnet, when giant magnetoresistance chip daughter board array (1) when powering on, described bias magnetic field output offset voltage; The magnetic field superposition that produces when tested bus current is on bias magnetic field the time, the output voltage of giant magnetoresistance chip daughter board array (1) is the voltage that is produced by the magnetic field of tested bus current generation that superposeed on the basis of former bias voltage, through described FPGA signal processing circuit bias voltage is reduced, just obtain the voltage of a bipolar output, this voltage for produce by tested bus current magnetic field produced.