CN113945608A - Magnetic induction phase shift measurement system based on magnetoelectric sensor - Google Patents
Magnetic induction phase shift measurement system based on magnetoelectric sensor Download PDFInfo
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Abstract
The invention discloses a magnetic induction phase shift measurement system based on a magnetoelectric sensor, which solves the problem that whether biological tissues are abnormal or not can not be accurately obtained when biological tissues such as liver tissues, breast tissues, bladder tissues and the like are detected by using a magnetic induction phase shift technology in the prior art. The magnetic-electric sensor is utilized to detect 10 at the resonance frequency of kHz‑13The characteristics of the magnetic field with T magnitude can better detect the induction magnetic field, and the electric conductance of the whole system to the biological tissue is improvedThe sensitivity of the rate change enables more internal detection of biological tissue.
Description
Technical Field
The invention relates to the technical field of biomedical equipment, in particular to a magnetic induction phase shift measurement system based on a magnetoelectric sensor.
Background
Magnetic Induction Phase Shift (MIPS) is a technique in which a biological tissue is placed between an excitation coil and a detection Magnetic field sensor by using the principle of Magnetic Induction, and when an alternating excitation Magnetic field B generated by the excitation coil to which an alternating current is supplied passes through the biological tissue, an induced current is generated in the biological tissue, which in turn generates an induced Magnetic field Δ B, and the detection Magnetic field sensor can detect Δ B. When the electrical conductivity sigma of the biological tissue changes, the intensity and distribution of the induction current can be influenced, the measured delta B can reflect the change of the electrical conductivity, the phase shift theta generated between the excitation magnetic field and the induction magnetic field can be deduced according to the vector relation of the B and the delta B, and the change of the electrical conductivity can be reflected by detecting the phase shift theta. Therefore, whether the biological tissue is abnormal or not can be judged through the change of the phase difference.
Biological tissues, such as the skull of a human being, have a significant phase difference under the action of an excitation magnetic field at a megahertz frequency, and a coil or an antenna has a very prominent behavior in detecting magnetic fields at megahertz and above, and therefore, is often used as a sensor for detecting an induced magnetic field in the frequency band. The patent office of china, 2021, 7/20, discloses an invention entitled a magnetic induction phase shift-based real-time monitoring system for blood flow of biological tissues and a simulation monitoring system, and its publication number is CN 113133753A. The invention comprises a signal source, an exciting coil unit, a receiving coil unit, a digitizer and an upper computer PC; the signal source outputs two sinusoidal signals with the same frequency and phase, the sinusoidal signals are respectively connected with the exciting coil unit and the digitizer, the receiving coil unit is connected with the digitizer and used for collecting output signals which are sent by the exciting coil unit and generated in the receiving coil unit after passing through the part to be detected, and the output signals are transmitted to the upper computer for analysis and processing to obtain the real-time state of the part to be detected. The system provided by the invention utilizes the magnetic induction phase shift to monitor the pulsation condition of the cerebral blood flow, and continuously and effectively monitors the variation of the cerebral blood flow pulsation by combining the arterial blood flow mechanics theory and the magnetic induction phase shift detection principle. However, the system uses the coil as a magnetic field sensor, and is limited in that the sensitivity of the coil is insufficient, the excitation frequency is often 1-100 MHz, and the detection depth is insufficient due to the skin effect. And different biological tissues have different characteristics such as liver tissue, breast tissue, bladder tissue, etc., which show a significant phase difference under the action of an excitation magnetic field of a kilohertz frequency, but the performance of the coil or antenna at the kilohertz frequency is not very excellent.
The magnetoelectric sensor is widely concerned because of convenient operation and high sensitivity at room temperature, particularly has outstanding performance at the resonance frequency of kilohertz, and can ensure that the resonance frequency of the magnetoelectric sensor is in a range from zero to kilohertz according to different materials and sizes for preparing the magnetoelectric sensor. In addition, the output response of the magnetoelectric sensor depends on the piezomagnetic coefficient, the piezomagnetic coefficient tends to rise first and then fall along with the direct-current bias magnetic field, the piezomagnetic coefficient can reach the maximum under a certain direct-current bias magnetic field, the direct-current bias magnetic field at the moment is the optimal direct-current bias magnetic field, and the performance of the sensor can be improved by dozens of times or even thousands of times under the direct-current bias magnetic field. Currently, an alternating current magnetic field of 200 fT can be detected at the resonance frequency of 6.862 kHz by using a magnetostrictive material Metglas and a piezoelectric material lithium niobate under an optimal direct current bias magnetic field of 5 Oe.
Disclosure of Invention
The invention aims to solve the problem that whether biological tissues are abnormal or not can not be accurately obtained when biological tissues such as liver tissues, breast tissues, bladder tissues and the like are detected by using a magnetic induction phase shift technology in the prior art, and provides a magnetic induction phase shift measurement system based on a magnetic electric sensor, wherein the magnetic electric sensor can detect 10 kHz resonant frequency -13The performance of the magnetic field with the magnitude of T can better detect the induction magnetic field, the sensitivity of the whole system to the conductivity change of the biological tissue is improved, and the more internal detection of the biological tissue is realized.
In order to achieve the purpose, the invention adopts the following technical scheme: the method comprises the following steps:
a signal source module: outputting two alternating current signals with the same frequency and phase, wherein one signal is transmitted to an amplifying excitation module to generate an excitation signal, and the other signal is transmitted to a signal processing module to generate a reference signal;
an amplification excitation module: amplifying the signal provided by the signal source module and simultaneously generating an alternating current excitation magnetic field and a direct current bias magnetic field;
a magnetoelectric sensor: simultaneously detecting an excitation magnetic field generated by the amplification excitation module and an induction magnetic field generated by the biological tissue, and generating an output signal to the signal processing module;
the signal processing module: and processing the output signal of the magnetoelectric sensor and the reference signal provided by the signal source module to obtain a phase difference, and judging whether the detected tissue is abnormal or not according to the change of the phase difference.
The output end of the signal source module is respectively connected with the input end of the amplifying and exciting module and the reference signal end of the signal processing module, the output end of the amplifying and exciting module is connected with the magnetoelectric sensor, and the output end of the amplifying and exciting module is connected with the input end of the signal processing module. The number of the magnetoelectric sensors is not less than one. The biological tissue generates an induced magnetic field due to an eddy current effect under the action of an alternating current excitation magnetic field, wherein the induced magnetic field and the excitation magnetic field have a phase difference. The magnetoelectric sensor detects an excitation magnetic field and an induction magnetic field generated by biological tissues simultaneously, an output signal of the magnetoelectric sensor is processed through a signal processing module and a reference signal provided by a signal source module to obtain a phase difference, and whether the intracranial pressure changes or not is judged through the change of the phase difference.
According to the invention, the excitation magnetic field of kHz is utilized, the lower the frequency of the excitation magnetic field is, the deeper the detection depth is, and compared with the existing excitation magnetic field of MHz or even GHz, the detection depth of the system is greatly improved, so that the detection of the more interior of the biological tissue can be realized by adopting the excitation magnetic field of kHz, and the detection is not only limited to the surface. The current common high-precision magnetic field sensor comprises a fluxgate meter, a superconducting quantum interferometer and an optical pump magnetometer, but the fluxgate meter can only realize 10 pairs-9The magnetic field detection of T magnitude and higher cost; the superconducting quantum interferometer can only measure the magnetic field in a very small range, is too high in cost and cannot work at room temperature, and needs liquidThe SQUID can normally work due to helium refrigeration, is large in size and is not easy to carry; the optical pump magnetometer can only detect +/-5 multiplied by 10-9The magnetic field in the T is large, low in bandwidth, high in cost and high in requirement on shielding performance of the surrounding environment. Therefore, the invention utilizes the magnetoelectric sensor with excellent performance under the frequency and the optimal bias magnetic field to detect the induction magnetic field generated by biological tissues such as liver tissues, breast tissues, bladder tissues and the like under the action of the excitation magnetic field, and carries out signal processing on the output signal of the magnetoelectric sensor to obtain the phase difference between the induction magnetic field and the excitation magnetic field, and judges whether the biological tissues have abnormality or not through the change of the phase difference. The performance of the magnetoelectric sensor at the resonance frequency point of kHz is extremely excellent, and the pair 10 can be realized -13T magnitude of force magnetic field detection, and excitation magnetic field frequency only needs a frequency point, consequently can detect induction magnetic field better to promote the sensitivity of entire system to biological tissue conductivity change, and magnetoelectric sensor is with low costs, can work at room temperature, and is small, easily carries.
Preferably, the frequency of the alternating current signal generated by the signal source module is the same as the resonant frequency of the magnetoelectric sensor. At this frequency, the magnetoelectric sensor performs best.
Preferably, the amplifying and exciting module comprises:
a current amplifier: amplifying the signal generated by the signal source module;
a direct current bias module: generating a direct current bias current, carrying out direct current bias on the signal amplified by the current amplifier, and applying the amplified signal to an exciting coil;
an exciting coil: and simultaneously generates an alternating current excitation magnetic field and a direct current bias magnetic field.
The input end of the current amplifier is connected with the output end of the signal source module, the output end of the current amplifier is connected with the input end of the direct current bias module, and the output end of the direct current bias module is connected with the exciting coil. The signal source module generates an alternating current signal with the same frequency as the resonant frequency of the magnetoelectric sensor, the signal amplified by the current amplifier is subjected to direct current bias by the direct current bias module, the final output signal acts on the exciting coil, and the exciting coil simultaneously generates an alternating current exciting magnetic field and a direct current bias magnetic field.
Preferably, the excitation coil is a solenoid wound on the magnetoelectric sensor, two ends of the solenoid are respectively connected with the output end of the direct current bias module, and the tissue to be detected is arranged on the right side of the solenoid. The exciting coil is wound on the magnetoelectric sensor, so that the size can be reduced, and the operation is convenient.
Preferably, the exciting coil is a Helmholtz coil, the Helmholtz coil comprises a left Helmholtz coil and a right Helmholtz coil, the magnetoelectric sensor is arranged between the left Helmholtz coil and the right Helmholtz coil, and the measured tissue is arranged between the magnetoelectric sensor and the right Helmholtz coil. Helmholtz coils are devices that produce a uniform magnetic field over a small area, and are open-ended in that other instruments can be easily placed in and removed from the device. The left Helmholtz coil and the right Helmholtz coil generate a large-range uniform field, the uniform field comprises an alternating current excitation magnetic field and a direct current bias magnetic field, and the magnetoelectric sensor and the measured tissue are positioned in the uniform field.
Preferably, the left Helmholtz coil and the right Helmholtz coil can be perpendicular to the magnetoelectric sensor, and can also form an included angle. The horizontal line of the magnetoelectric sensor can be vertical to the plane where the left Helmholtz coil and the right Helmholtz coil are located, and an included angle can also be formed. The left Helmholtz coil and the right Helmholtz coil generate a large-range uniform field, the uniform field comprises an alternating current excitation magnetic field and a direct current bias magnetic field, the direction of the uniform field and the sensitive direction of the magnetoelectric sensor form a certain angle, the response of the magnetoelectric sensor to the excitation magnetic field is weakened, but the detection of the magnetoelectric sensor to the induction magnetic field generated by a measured object is hardly influenced, and therefore the identification capability of the magnetoelectric sensor to the induction magnetic field can be improved.
Preferably, the magnitude of the dc bias magnetic field generated by the dc bias module is the optimal magnitude of the dc bias magnetic field of the magnetoelectric sensor. The size of the direct current bias magnetic field is equal to the size of the optimal direct current bias magnetic field of the magnetoelectric sensor by adjusting the direct current bias module, and the performance of the magnetoelectric sensor can be improved to the greatest extent by the direct current bias magnetic field under the size.
Preferably, the signal processing module includes:
a pre-amplification module: amplifying an output signal of the magnetoelectric sensor;
a filter: filtering the amplified output signal;
the phase discrimination module: and processing and analyzing the reference signal of the signal source module and the output signal of the magnetoelectric sensor after amplification and filtering to obtain the phase difference.
The input end of the pre-amplification module is connected with the output end of the magnetoelectric sensor, the input end of the filter is connected with the output end of the pre-amplification module, and the input end of the phase discrimination module is simultaneously connected with the output end of the filter and the reference signal output end of the signal source module. The phase discrimination module processes the draft test signal and the output signal to obtain a phase difference, once the conductivity or the volume of the detected tissue changes, the finally output phase changes, and the detected tissue can be deduced to be abnormal through the change of the phase.
Preferably, the filter may be a hardware circuit or a software program. The filter is a common instrument, a hardware circuit of the filter mainly comprises a capacitor, an inductor and a resistor, and the filter can effectively filter a frequency point of a specific frequency in a power line or frequencies except the frequency point to obtain a power signal of the specific frequency or eliminate the power signal of the specific frequency.
Preferably, the phase detection module may be a hardware circuit or a software program. Phase detection modules are also known in the prior art.
Therefore, the invention has the following beneficial effects: 1. the induction magnetic field generated by biological tissues such as liver tissue, breast tissue, bladder tissue and the like under the action of the excitation magnetic field with the frequency of kilohertz can be effectively detected; 2. the device can work at room temperature, is dynamic in real time, and has simple structure, convenient operation and low cost; 3. 10 can be detected at the resonance frequency of kHz by using a magnetoelectric sensor as a detection sensor-13Magnetic field of T magnitude, thereby better detecting the induced magnetic fieldAnd the sensitivity of the whole system to the conductivity change of the biological tissue is improved, and the more internal detection of the biological tissue is realized.
Drawings
FIG. 1 is a schematic diagram of the present invention in which the excitation coil is a solenoid;
FIG. 2 is a schematic diagram of a Helmholtz coil configuration of the excitation coil of the present invention;
FIG. 3 is another schematic diagram of the present invention with the excitation coil being a Helmholtz coil;
FIG. 4 is a graph of the test results of the present invention;
FIG. 5 is a schematic diagram of a magnetoelectric sensor according to the present invention in two configurations;
FIG. 6 is a schematic diagram of a magnetoelectric sensor according to the present invention having two signal output ports;
in the figure: 1. a phase discrimination module; 2. a filter; 3. a pre-amplification module; 4. a solenoid; 5. a magnetoelectric sensor; 6. a measured tissue; 7. a signal source module; 8. a current amplifier; 9. a DC bias module; 10. a left Helmholtz coil; 11. a right Helmholtz coil; 12. an acquisition module; 13. a phase discriminator; 14. a first magnetoelectric sensor; 15 a second magnetoelectric sensor; 16. a magnetostrictive material; 17. a first piezoelectric material; 18. a second piezoelectric material; 19. a charge amplifier; 20. a differential amplifier.
Detailed Description
The invention is described in further detail below with reference to the following detailed description and accompanying drawings:
the present embodiment is a magnetic induction phase shift measurement system based on a magnetoelectric sensor, wherein an excitation coil is a solenoid, and the structure of the magnetic induction phase shift measurement system is shown in fig. 1, and the magnetic induction phase shift measurement system includes a phase discrimination module 1, a filter 2, a pre-amplification module 3, a solenoid 4, a magnetoelectric sensor 5, a signal source module 7, a current amplifier 8, and a dc bias module 9. The output end of the signal source module is respectively connected with the input end of the current amplifier and the reference signal end of the phase discrimination module, the output end of the current amplifier is connected with the input end of the direct current bias module, the output end of the direct current bias module is connected with the solenoid, the tissue to be detected 6 is positioned on the right side of the solenoid, the solenoid simultaneously generates an alternating current excitation magnetic field and a direct current bias magnetic field, the magnetoelectric sensor detects an induced magnetic field generated by the excitation magnetic field and the biological tissue, the output end of the magnetoelectric sensor is connected with the pre-amplification module, and the output end of the pre-amplification module is connected with the phase discrimination module through the filter 2.
When the electromagnetic induction type electromagnetic induction. After detecting the excitation magnetic field and the induction magnetic field, the magnetoelectric sensor performs phase analysis with a reference signal in a phase discrimination module through preposed amplification and filtering to obtain a phase difference.
This embodiment is a magnetic induction phase shift measurement system based on magnetoelectric sensor, wherein excitation coil is the excitation coil and is helmholtz coil, its structure is shown in fig. 2, the output of signal source module 7 is connected with the input of current amplifier 8, the input of phase discriminator 13 respectively, provide excitation signal for current amplifier, provide reference signal for the phase discriminator, the current amplifier output is connected with the input of direct current bias module 9, left helmholtz coil 10, right helmholtz coil 11 are connected respectively to two outputs of direct current bias module. Put magnetoelectric sensor 5, surveyed tissue 6 between left Helmholtz coil and the right Helmholtz coil in proper order, and magnetoelectric sensor and biological tissue are on same straight line, and this straight line is perpendicular with the plane at left Helmholtz coil and the coil place of right Helmholtz coil. The output end of the magnetoelectric sensor is connected with the input end of the preamplification module, the output end of the preamplification module is connected with the input end of the filter, the output end of the filter is connected with the input end of the phase discriminator, and the output end of the phase discriminator is connected with the acquisition module.
When the electromagnetic induction type electromagnetic resonance sensor works, a signal source module is connected with a left Helmholtz coil 10 and a right Helmholtz coil 11 through a current amplifier and a direct current bias module, the direct current bias module is a voltage bias adjusting circuit, the left Helmholtz coil and the right Helmholtz coil generate a large-range uniform field, the uniform field comprises an alternating current excitation magnetic field and a direct current bias magnetic field, the frequency of the alternating current excitation magnetic field is the resonant frequency of the electromagnetic sensor, the size of the direct current bias magnetic field generated by the direct current bias module is the optimal bias magnetic field size of the electromagnetic sensor, the electromagnetic sensor and a measured tissue 6 are positioned in the uniform field, and at the moment, the direction of the excitation magnetic field is the same as the sensitive direction of the electromagnetic sensor. The magnetoelectric sensor detects an excitation magnetic field and an induction magnetic field generated by the measured tissue, the output of the magnetoelectric sensor is connected with a preamplifier module, and the preamplifier module is a charge preamplifier. The charge preamplifier is connected with the phase discrimination module through the filter, and the phase discrimination module comprises a phase discriminator and an acquisition module. Meanwhile, the reference signal of the signal source module is connected with the phase discriminator. The acquisition module 12 acquires the magnitude of the direct current output by the phase discriminator, obtains the phase through the relation characteristic of the direct current and the phase of the phase discriminator, and once the conductivity or the volume of the detected tissue is changed, the finally output phase changes, and the abnormal condition of the detected object can be deduced through the change of the phase.
This embodiment is a magnetic induction phase shift measurement system based on magnetoelectric sensor, wherein excitation coil is the excitation coil and is helmholtz coil, its structure is shown in fig. 3, the output of signal source module 7 is connected with the input of current amplifier 8, the input of phase discriminator 13 respectively, provide excitation signal for current amplifier, provide reference signal for the phase discriminator, the current amplifier output is connected with the input of direct current bias module 9, left helmholtz coil 10, right helmholtz coil 11 are connected respectively to two outputs of direct current bias module. Put magnetoelectric sensor 5, surveyed tissue 6 between left Helmholtz coil and the right Helmholtz coil in proper order, and magnetoelectric sensor and biological tissue are on same straight line, and this straight line becomes the angle with the plane at left Helmholtz coil and the coil place of right Helmholtz coil. The output end of the magnetoelectric sensor is connected with the input end of the preamplification module, the output end of the preamplification module is connected with the input end of the filter, the output end of the filter is connected with the input end of the phase discriminator, and the output end of the phase discriminator is connected with the acquisition module.
When the electromagnetic induction type electromagnetic resonance sensor works, a signal source module is connected with a left Helmholtz coil 10 and a right Helmholtz coil 11 through a current amplifier and a direct current bias module, the direct current bias module is a voltage bias adjusting circuit, the left Helmholtz coil and the right Helmholtz coil generate a large-range uniform field, the uniform field comprises an alternating current excitation magnetic field and a direct current bias magnetic field, the frequency of the alternating current excitation magnetic field is the resonance frequency of the electromagnetic sensor, the size of the direct current bias magnetic field generated by the direct current bias module is the optimal size of the bias magnetic field of the electromagnetic sensor, and the electromagnetic sensor and a measured tissue 6 are located in the uniform field. At the moment, the uniform field direction and the sensitive direction of the magnetoelectric sensor form a certain angle, so that the response of the magnetoelectric sensor to an excitation magnetic field is weakened, but the detection of the magnetoelectric sensor to an induction magnetic field generated by the detected tissue is hardly influenced, and the identification capability of the magnetoelectric sensor to the induction magnetic field can be improved. The magnetoelectric sensor detects an excitation magnetic field and an induction magnetic field generated by the measured tissue, the output of the magnetoelectric sensor is connected with a preamplifier module, and the preamplifier module is a charge preamplifier. The charge preamplifier is connected with the phase discrimination module through the filter, and the phase discrimination module comprises an AD8302 phase discriminator and an acquisition module. Meanwhile, the reference signal of the signal source module is connected with the phase discriminator. The acquisition module 12 acquires the magnitude of the direct current output by the AD8302 phase discriminator, the phase is obtained through the relation characteristic of the direct current and the phase of the phase discriminator, once the conductivity or the volume of the detected tissue is changed, the finally output phase changes, and the abnormal condition of the detected object can be deduced through the change of the phase.
By adopting the structure, a magnetoelectric sensor based on Metglas (magnetostrictive material)/PZT (piezoelectric material) is used for testing, the resonant frequency of the magnetoelectric sensor is 19.8kHz, the optimal bias magnetic field is 9.6Oe, therefore, the excitation magnetic field frequency is selected to be 19.8kHz, and the voltage bias adjusting circuit adjusts the direct current magnetic field to be 9.6 Oe. To test the feasibility of the system, brass spheres and 20% saline were used as the tissue tested and the results are shown in FIG. 4. It can be seen that as the volume of brass ball or brine increases, the phase of the system output gradually increases, thereby reflecting the feasibility of the system in testing different volumes of the object under test of the same conductivity.
This embodiment is a magnetic induction phase shift measurement system based on magnetoelectric sensor, and wherein exciting coil is helmholtz coil for exciting coil, and magnetoelectric sensor has two, and its structure is shown in fig. 5, and the preamplification module includes two identical charge amplifier 19 and a difference amplifier 20 this moment, and the phase discrimination module includes phase discriminator and collection module, the preferred AD8302 phase discriminator that is of phase discriminator, and magnetoelectric sensor has two, including first magnetoelectric sensor and second magnetoelectric sensor. The output end of the signal source module 7 is connected with the input end of the current amplifier 8 and the input end of the phase discriminator 13 respectively, an excitation signal is provided for the current amplifier, a reference signal is provided for the phase discriminator, the output end of the current amplifier is connected with the input end of the direct current bias module 9, and two output ends of the direct current bias module are connected with the left Helmholtz coil 10 and the right Helmholtz coil 11 respectively. Put magnetoelectric sensor, surveyed between left Helmholtz coil and the right Helmholtz coil in proper order and organize 6, parallel about first magnetoelectric sensor 14 and the second magnetoelectric sensor 15 are placed, and first magnetoelectric sensor and biological tissue are on same horizontal straight line, and this straight line becomes with the plane angle at left Helmholtz coil and the coil place of right Helmholtz coil. The output ends of the two magnetoelectric sensors are respectively connected with the input end of a charge amplifier, the output ends of the two charge amplifiers are respectively connected with the input end of a differential amplifier, the output end of the differential amplifier is connected with the input end of a filter, the output end of the filter is connected with the input end of a phase discriminator, and the output end of the phase discriminator is connected with an acquisition module.
When the electromagnetic induction type electromagnetic resonance sensor works, a signal source module is connected with a left Helmholtz coil 10 and a right Helmholtz coil 11 through a current amplifier and a direct current bias module, the direct current bias module is a voltage bias adjusting circuit, the left Helmholtz coil and the right Helmholtz coil generate a large-range uniform field, the uniform field comprises an alternating current excitation magnetic field and a direct current bias magnetic field, the frequency of the alternating current excitation magnetic field is the resonance frequency of the electromagnetic sensor, the size of the direct current bias magnetic field generated by the direct current bias module is the optimal size of the bias magnetic field of the electromagnetic sensor, and the two electromagnetic sensors and a measured tissue 6 are located in the uniform field.
At the moment, the direction of a uniform field and the sensitive directions of the two sensors form a certain angle, then the response of the magnetoelectric sensors to an excitation magnetic field is weakened, besides, the two magnetoelectric sensors are completely the same, the first magnetoelectric sensor 14 serves as a main sensor, the second magnetoelectric sensor 15 serves as a reference sensor, the main sensor is close to a measured tissue, so that the excitation magnetic field and the induction magnetic field can be detected, the reference sensor is far away from the measured tissue, the induction magnetic field is reduced along with the increase of the distance, so that the reference sensor mainly detects the excitation magnetic field, the outputs of the two magnetoelectric sensors are respectively connected with a differential amplifier through completely the same charge amplifier, and after differential amplification, the output signals are voltage signals generated by the detection of the induction magnetic field. The differential amplifier is connected with the phase discriminator through the filter, meanwhile, a reference signal of the signal source module is connected with the phase discriminator, the phase discriminator acquires the direct current quantity output by the AD8302 phase discriminator through the acquisition module, the phase is obtained through the relation characteristic of the direct current quantity and the phase of the phase discriminator, once the conductivity or the volume of the tested tissue is changed, the finally output phase changes, and the abnormal condition of the tested object can be pushed out through the change of the phase.
This embodiment is a magnetic induction phase shift measurement system based on magnetoelectric sensor, wherein exciting coil is helmholtz coil for exciting coil, magnetoelectric inductor is the magnetoelectric inductor including two signal output port of oneself equipment, its structure is shown in fig. 6, wherein magnetoelectric inductor includes magnetostrictive material 16, first piezoelectric material 17 and second piezoelectric material 18, the module of preamplifying includes two identical charge amplifier 19 and a differential amplifier 20, the phase discrimination module includes phase discriminator and collection module, the preferred AD8302 phase discriminator that is the phase discriminator. The output end of the signal source module 7 is connected with the input end of the current amplifier 8 and the input end of the phase discriminator 13 respectively, an excitation signal is provided for the current amplifier, a reference signal is provided for the phase discriminator, the output end of the current amplifier is connected with the input end of the direct current bias module 9, and two output ends of the direct current bias module are connected with the left Helmholtz coil 10 and the right Helmholtz coil 11 respectively. Put magnetoelectric sensor, surveyed tissue 6 between left Helmholtz coil and the right Helmholtz coil in proper order, first piezoelectric material 17 and 18 covers of second piezoelectric material are established on magnetostrictive material 16, and first piezoelectric material and second piezoelectric material are parallel from top to bottom placed, and first piezoelectric material and biological tissue are on same horizontal straight line, and this straight line becomes with the plane angle at left Helmholtz coil and the coil place of right Helmholtz coil. The first piezoelectric material and the second piezoelectric material are used as two output ends of the magnetoelectric sensor and are respectively connected with a charge amplifier, the output ends of the two charge amplifiers are respectively connected with the input end of a differential amplifier, the output end of the differential amplifier is connected with the input end of a filter, the output end of the filter is connected with the input end of a phase discriminator, and the output end of the phase discriminator is connected with a collection module.
When the device works, the signal source module is connected with the left Helmholtz coil and the right Helmholtz coil through the current amplifier and the direct current bias module, the direct current bias module is a voltage bias adjusting circuit, the left Helmholtz coil and the right Helmholtz coil generate a large-range uniform field, and the uniform field comprises an alternating current excitation magnetic field and a direct current bias magnetic field.
The magnetostrictive material, the first piezoelectric material and the second piezoelectric material form a magnetoelectric sensor with two signal output ports, wherein the first piezoelectric material and the second piezoelectric material are completely the same and are used as two signal output ports A and B of the magnetoelectric sensor, and the first piezoelectric material and the second piezoelectric material are sleeved on the magnetostrictive material and are in central symmetry with respect to the magnetostrictive material. In a uniform field generated by the Helmholtz coil, the frequency of an alternating current excitation magnetic field is the resonance frequency of the magnetoelectric sensors, the magnitude of a direct current bias magnetic field generated by the direct current bias module is the optimal magnitude of the bias magnetic field of the magnetoelectric sensors, and the two magnetoelectric sensors and the measured tissue 6 are positioned in the uniform field. At the moment, the direction of the uniform field and the sensitive direction of the sensor form a certain angle, so that the response of the magnetoelectric sensor to an excitation magnetic field is weakened. In addition, a signal output port A of the magnetoelectric sensor is used as a main output port, a signal output port B is used as a reference output port, the main output port is close to a detected tissue, therefore, output signals comprise signals generated after an excitation magnetic field and an induced magnetic field are detected, the reference output port is far away from the detected tissue, and the induced magnetic field is reduced along with the increase of the distance, therefore, the output signals only include signals generated after the excitation magnetic field is detected, the outputs of the two signal output ports are respectively connected with a differential amplifier through completely same charge amplifiers, and through differential amplification, the output signals are voltage signals generated after the induced magnetic field is detected. The differential amplifier is connected with the phase discriminator through the filter, meanwhile, a reference signal of the signal source module is connected with the phase discriminator, the phase discriminator acquires the size of the direct current output by the phase discriminator through the acquisition module, the phase is obtained through the relation characteristic of the direct current and the phase of the phase discriminator, once the conductivity or the volume of the detected tissue is changed, the finally output phase changes, and the detected object can be pushed out to be abnormal through the change of the phase.
The above-described embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention in any way, and other variations and modifications may be made without departing from the spirit of the invention as set forth in the claims.
Claims (10)
1. The utility model provides a magnetic induction phase shift measurement system based on magnetoelectric sensor which characterized in that includes:
signal source module (7): outputting two alternating current signals with the same frequency and phase, wherein one signal is transmitted to an amplifying excitation module to generate an excitation signal, and the other signal is transmitted to a signal processing module to generate a reference signal;
an amplification excitation module: amplifying the signal provided by the signal source module and simultaneously generating an alternating current excitation magnetic field and a direct current bias magnetic field;
magnetoelectric sensor (5): simultaneously detecting an excitation magnetic field generated by the amplification excitation module and an induction magnetic field generated by the biological tissue, and generating an output signal to the signal processing module;
the signal processing module: and processing the output signal of the magnetoelectric sensor (5) and a reference signal provided by the signal source module to obtain a phase difference, and judging whether the detected tissue is abnormal or not according to the change of the phase difference.
2. The magneto-electric sensor-based magnetic induction phase shift measurement system according to claim 1, wherein the frequency of the alternating current signal generated by the signal source module is the same as the resonant frequency of the magneto-electric sensor (5).
3. The magnetic induction phase shift measurement system based on a magnetoelectric sensor according to claim 1, characterized in that the amplifying and exciting module comprises:
current amplifier (8): amplifying the signal generated by the signal source module (7);
direct current bias module (9): generating a direct current bias current, carrying out direct current bias on the signal amplified by the current amplifier (8), and applying the amplified signal to an exciting coil;
an exciting coil: and simultaneously generates an alternating current excitation magnetic field and a direct current bias magnetic field.
4. The magnetic induction phase shift measurement system based on the magnetoelectric sensor according to claim 3, characterized in that, the exciting coil is a solenoid (4) wound on the magnetoelectric sensor, the two ends of the solenoid (4) are respectively connected with the output end of a DC bias module (9), the tissue to be measured is arranged on the right side of the solenoid (4).
5. The magnetic induction phase shift measurement system based on magnetoelectric sensors according to claim 3, characterized in that, the excitation coil is the Helmholtz coil, the Helmholtz coil includes left Helmholtz coil (10) and right Helmholtz coil (11), the magnetoelectric sensors are set up between left Helmholtz coil (10) and right Helmholtz coil (11), the measured tissue is set up between magnetoelectric sensors (5) and right Helmholtz coil (11).
6. The magnetic induction phase shift measurement system based on the magnetoelectric sensor according to claim 5, characterized in that the left Helmholtz coil (10) and the right Helmholtz coil (11) can be perpendicular to the magnetoelectric sensor (5) or can form an included angle.
7. The magneto-electric sensor-based magnetic induction phase shift measurement system according to claim 3, 4, 5 or 6, wherein the magnitude of the dc bias magnetic field generated by the dc bias module (9) is the optimal magnitude of the dc bias magnetic field of the magneto-electric sensor (5).
8. The magnetic induction phase shift measurement system based on a magnetoelectric sensor according to claim 1, characterized in that the signal processing module comprises:
pre-amplification module (3): amplifying the output signal of the magnetoelectric sensor (5);
filter (2): filtering the amplified output signal;
phase discrimination module (1): and processing and analyzing the reference signal of the signal source module (7) and the amplified and filtered output signal of the magnetoelectric sensor (5) to obtain the phase difference.
9. The magnetic induction phase shift measurement system based on a magnetoelectric sensor according to claim 8, characterized in that the filter (2) can be either a hardware circuit or a software program.
10. The magnetic induction phase shift measurement system based on a magnetoelectric sensor according to claim 8 or 9, characterized in that the phase discrimination module (1) can be either a hardware circuit or a software program.
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