A weak magnetic measurement device based on a TMR sensor

Abstract

The utility model discloses a kind of weak magnetic measurement devices based on TMR sensor, comprising: TMR sensor module, angle feedback module, direction control module for adjusting TMR sensor module position, electronic compass module, main control module and interactive module;TMR sensor module is used to collect magnetic field intensity signal;Angle feedback module is used to real-time feedback direction control module's position signal to main control module, electronic compass module is used to obtain magnetic field direction signal and transmit to main control module;Main control module is used to control direction control module rotation according to the magnetic field direction signal of electronic compass module transmission and the position signal of angle feedback module transmission, to correct the position of TMR sensor module to the direction of TMR sensor module and magnetic field direction alignment.The utility model has high sensitivity, high resolution, real-time data processing and portable design etc. Characteristics, can adapt to the application requirement of different scene.

Description

Technical Field

[0001] This utility model relates to the field of magnetic field detection technology, and in particular to a weak magnetic field measurement device based on a TMR sensor. Background Technology

[0002] Currently, weak magnetic field measuring devices are being used more and more widely in various fields, such as geological exploration, medical imaging, environmental monitoring, and electronic product testing. However, these measuring devices generally suffer from drawbacks such as low measurement accuracy, high cost, and large size, which seriously limit their promotion and popularization in practical applications.

[0003] First, low measurement accuracy is a major drawback of weak magnetic field measurement equipment. Many existing devices cannot provide sufficient sensitivity when faced with weak magnetic fields, leading to inaccurate measurement results and affecting the reliability of the data. Such low-precision measurement results may lead to incorrect judgments in scientific research and industrial applications, thereby affecting decision-making and subsequent work.

[0004] Secondly, high cost is also a significant factor limiting the widespread adoption of weak magnetic field measuring devices. Many high-performance weak magnetic field measuring devices currently on the market are expensive, often exceeding the affordability of small and medium-sized enterprises and individual users. This makes it difficult for many potential users to find a balance between demand and cost, further inhibiting market expansion.

[0005] Furthermore, the issues of large size and poor portability cannot be ignored. Many traditional weak magnetic field measuring devices are complex in design and bulky in size, making them difficult to use in field or non-laboratory environments. This limitation often forces users to rely on cumbersome equipment when on-site measurements are required, increasing the difficulty and inconvenience of operation.

[0006] While various sensors (such as Hall effect sensors and magnetoresistive sensors) are used for detecting weak magnetic fields in existing technologies, most devices still need improvement in terms of sensitivity, resolution, and portability. These sensors perform well under certain specific conditions, but in practical applications, they often fail to meet users' demands for high performance and multifunctionality. Therefore, there is an urgent need for a new type of weak magnetic field measurement device to meet the growing market demand. Utility Model Content

[0007] This invention provides a weak magnetic field measurement device based on a TMR sensor to overcome the above-mentioned technical problems.

[0008] To achieve the above objectives, the technical solution of this utility model is as follows: A weak magnetic field measurement device based on a TMR sensor includes: a TMR sensor module, an angle feedback module, a direction control module for adjusting the position of the TMR sensor module, an electronic compass module, a main control module, and an interaction module. The TMR sensor module is used to acquire magnetic field strength signals. The angle feedback module is used to provide real-time feedback of the position signal of the direction control module to the main control module. The electronic compass module is used to acquire magnetic field direction signals and transmit them to the main control module. The main control module controls the rotation of the direction control module based on the magnetic field direction signal transmitted by the electronic compass module and the position signal transmitted by the angle feedback module, thereby correcting the position of the TMR sensor module until its direction is aligned with the magnetic field direction. The interaction module displays the magnetic field measurement results based on the magnetic field strength signal acquired by the TMR sensor module after the position correction.

[0009] Furthermore, the direction control module includes: a rotating bracket with a turntable, a first servo motor, a second servo motor, and a sensor bracket for mounting the TMR sensor module; the body of the first servo motor is fixedly connected to the rotating bracket, and its output shaft is connected to the turntable; the body of the second servo motor is connected to the turntable, and its output shaft is connected to the sensor bracket; the first servo motor drives the turntable to rotate, thereby driving the TMR sensor module to perform horizontal rotation; the second servo motor drives the sensor bracket to rotate, thereby driving the TMR sensor module to perform pitch rotation.

[0010] Furthermore, the TMR sensor module uses a TMR2652D sensor.

[0011] Furthermore, the electronic compass module employs a Honeywell HMC5883L magnetoresistive sensor. Furthermore, the weak magnetic field measuring device also includes a metal shielding box; the metal shielding box is equipped with the TMR sensor module, angle feedback module, direction control module, electronic compass module and main control module; and one end face of the metal shielding box is provided with a mounting groove for installing the interaction module, the interaction module being embedded in the mounting groove.

[0012] Furthermore, the metal shielding box includes an inner shell and an outer shell, with a copper foil disposed between the inner shell and the outer shell.

[0013] Furthermore, the angle feedback module is integrated within the direction control module.

[0014] Beneficial effects: This utility model uses a TMR sensor module and an electronic compass module to detect the magnetic field. The electronic compass module acquires the magnetic field direction signal, and the main control module controls the rotation of the direction control module based on the magnetic field direction signal and the position signal transmitted by the angle feedback module, so as to correct the position of the TMR sensor module until the direction of the TMR sensor module is aligned with the magnetic field direction. This utility model has the characteristics of high sensitivity, high resolution, real-time data processing and portable design, and can adapt to the application needs of different scenarios. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a structural block diagram of the weak magnetic field measuring device in this utility model; Figure 2 This is a schematic diagram of the weak magnetic field measuring device in this utility model; Figure 3 This is a first structural schematic diagram of the direction control module in this utility model; Figure 4 This is a schematic diagram of the second structure of the direction control module in this utility model; Figure 5 This is a circuit diagram of the TMR2652D sensor in this utility model; Figure 6 This is a circuit diagram of the electronic compass module in this utility model.

[0017] In the diagram: 1. TMR sensor module; 2. Direction control module; 21. Rotating bracket; 211. Turntable; 212. First mounting platform; 213. Second mounting platform; 22. First servo motor; 23. Second servo motor; 231. Fixing plate; 24. Sensor bracket; 3. Electronic compass module; 4. Main control module; 5. Interaction module; 6. Metal shielding box; 7. Buzzer. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0019] This embodiment provides a weak magnetic field measurement device based on a TMR sensor, such as... Figure 1 As shown, it includes: TMR sensor module 1, angle feedback module, direction control module 2 for adjusting the position of TMR sensor module, electronic compass module 3, main control module 4 (microcontroller) and interaction module 5 (TFT display module and voice broadcast module). Specifically, the TMR sensor module 1 is used to acquire magnetic field strength signals; the angle feedback module is used to acquire the position signals of the direction control module 2 and transmit them to the main control module. Specifically, the angle feedback module is a photoelectric encoder, integrated within the direction control module. In this embodiment, it is integrated within the first and second servo motors, providing real-time feedback of the rotation angle of the direction control module 2 to the main control module, thus providing data for the main control module to calculate the deviation angle θ. In this embodiment, the TIM4 / TIM5 channels of the main control module are configured in encoder mode, with a 4x frequency counter and an angle resolution of 0.1°.

[0020] Specifically, the electronic compass module 3 is used to acquire magnetic field direction signals and transmit them to the main control module; Specifically, the main control module 4 is used to control the rotation of the direction control module 2 according to the magnetic field direction signal transmitted by the electronic compass module 3 and the position signal transmitted by the angle feedback module, so as to correct the position of the TMR sensor module 1 so that the direction of the TMR sensor module is aligned with the magnetic field direction. In a specific embodiment, the weak magnetic field measurement device also includes a power management module, which is powered by a low-noise LDO (ripple <10μV).

[0021] Specifically, in this embodiment, the main control module uses an STM32F407 chip (with a built-in 12-bit ADC that supports floating-point operations).

[0022] Specifically, the main control module integrates a 12-bit ADC, a Kalman filter algorithm, and a dynamic calibration algorithm. It fuses magnetic field strength and direction information using the Kalman filter algorithm, and compares the TMR magnetic field strength with the electronic compass direction data in real time to correct for environmental interference and sensor drift. Based on the heading angle α and pitch angle β output by the electronic compass, combined with the theoretical direction of the target magnetic field (γ, δ), it calculates the axial deviation θ between the target magnetic field direction and the TMR sensor. If the deviation exceeds a threshold (θ>45°), a buzzer 7 is triggered to issue a voice alarm (e.g., "Direction deviation is too large, please manually calibrate"), and data acquisition is paused. If θ>1°, a PID controller (PID parameter set to: proportional coefficient K) is used. p =0.8, integral coefficient K i =0.05, differential coefficient K d =0.1) control algorithm to adjust the speed of servo motor, drive servo motor to adjust the position of TMR sensor, so that θ<0.5°, thereby realizing dynamic calibration of TMR sensor orientation.

[0023] Specifically, the interaction module 5 is used to display the magnetic field measurement results based on the magnetic field strength signal collected by the TMR sensor module 1 after the position is corrected.

[0024] In this embodiment, the interaction module includes a 3.5-inch TFT display screen (resolution ≥320×480, ILI9488 driver, SPI interface) and a SYN6288 voice chip (UART protocol, supports Chinese speech synthesis), which displays three-dimensional vector graphics and historical curves in real time, and broadcasts the detection results through the voice chip.

[0025] In a specific embodiment, the magnetic field weakening measurement device also includes a signal conditioning circuit, comprising a low-noise amplifier (LNA) and a three-stage inverting amplifier circuit, with a total gain of 60dB and a bandwidth of 0.1Hz-1kHz; the LNA adopts a fully differential instrumentation amplifier (such as ADIAD8421), with an input noise density of <1nV / √Hz, a gain of 100 times, and a 10kΩ / 100 nF RC low-pass filter connected in parallel at the input stage; the multi-stage amplifier circuit adopts a three-stage inverting amplifier (such as OPA2188), with the first stage having a gain of 10 times (bandpass 0.1 Hz - 100Hz), the second stage having a gain of 10 times (bandpass 100Hz-1kHz), and the third stage being a voltage follower. Specifically, the circuit topology of the low-noise amplifier (LNA) circuit is as follows: TMR output → 10kΩ / 100nF RC filter → AD8421 (gain=100) → 1kΩ / 10nF low-pass filter → multi-stage amplification.

[0026] Noise optimization: Input stage shielding: LNA input traces are wrapped in copper foil and grounded at a single point.

[0027] Power supply decoupling: A 10μF tantalum capacitor and a 100nF ceramic capacitor are connected in parallel to the power supply pins of each amplifier stage.

[0028] Multi-stage amplification and filtering circuits: First stage: OPA2188 inverting amplifier (gain=10), bandpass filter (0.1Hz-100Hz).

[0029] Second stage: OPA2188 inverting amplifier (gain=10), bandpass filter (100Hz-1kHz).

[0030] The third stage: OPA2188 voltage follower, driving the ADC input.

[0031] In a specific embodiment, the TMR sensor module 1 uses a TMR2652D sensor. Specifically, the TMR2652D sensor employs advanced tunnel magnetoresistive (TMR) technology, which offers superior temperature and long-term stability compared to other magnetic sensor technologies. It is less affected by ambient temperature changes and time drift, maintaining stable performance over a wide temperature range. Furthermore, its sensitivity of 50mV / V / Oe means it can output a relatively high voltage signal for a unit change in voltage and magnetic field strength (Oe), enabling it to detect weak magnetic field changes and making it suitable for applications requiring high magnetic field detection accuracy. It features a linear range of ±5Oe, within which the sensor's output signal exhibits a linear relationship with the detected magnetic field strength, facilitating signal processing and data analysis. This allows it to accurately reflect changes in magnetic field strength, detecting weak magnetic fields at the nT level. Powered by a constant current source (1mA ±0.1%), the output signal is connected to an LNA after RC low-pass filtering (10Hz). Its internal structure and manufacturing process provide it with a certain degree of electromagnetic interference resistance, enabling it to operate normally in complex electromagnetic environments and reducing the impact of external interference signals on the detection results. It can operate normally with a constant current source (such as 1mA), making it suitable for portable or battery-powered devices with strict power consumption requirements, which helps to extend the device's battery life.

[0032] Specifically, the pin functions of the TMR2652D chip are as follows: the VREF pin connects to an external reference voltage, providing an accurate voltage reference for the internal circuitry; the GND pin is grounded, establishing a potential reference point; the NC pin is unconnected and has no electrical connection; the Comp pin (function depends on the chip datasheet); the VCC pin connects to a 3.3V power supply, providing power for chip operation; the VOUT pin serves as a signal output terminal, converting the detected magnetic field signal into an electrical signal for subsequent processing and analysis.

[0033] Specifically, such as Figure 5As shown, the TMR sensor is connected to external devices via an HDR-F-2.54_1x4 connector (H1). Pin 1 is grounded (GND), pin 2 is connected to the reference voltage VREF, pin 3 is connected to the power supply VCC3V3, and pin 4 is used to transmit the sensor output signal or other control signals, enabling convenient connection and communication between the circuit and external systems.

[0034] In a specific embodiment, such as Figure 2 and Figure 3 As shown, the direction control module 2 includes: a rotating bracket 21 with a turntable 211, a first servo motor 22, a second servo motor 23, and a sensor bracket 24 for mounting the TMR sensor module 1; the body of the first servo motor 22 is fixedly connected to the rotating bracket 21, and its output shaft is connected to the turntable 211; the body of the second servo motor 23 is fixedly connected to the turntable 211, and its output shaft is connected to the sensor bracket 24; the first servo motor 22 drives the TMR sensor module 1 to perform horizontal rotation by driving the turntable 211 to rotate; the second servo motor 23 drives the TMR sensor module 1 to perform pitch rotation by driving the sensor bracket 24 to rotate.

[0035] Specifically, in this embodiment, such as Figure 3 and Figure 4 As shown, the rotating bracket 21 includes a first mounting platform 212 and a second mounting platform 213 arranged opposite to each other, and the second mounting platform 212 and the second mounting platform 213 are fixedly connected by a plurality of connecting rods; the first mounting platform 212 is provided with a first mounting hole for mounting a first servo motor 22, and the body of the first servo motor 22 is fixedly connected to the first mounting platform 212 through the first mounting hole; the second mounting platform 213 is provided with a second mounting hole for mounting a turntable 211, the outer ring structure of the turntable 211 is fixedly connected to the second mounting platform 213, and the rotating structure of the turntable 211 is connected to the output shaft of the first servo motor 22 through the second mounting hole, and drives the TMR sensor module to rotate horizontally from 0 to 270° under the drive of the first servo motor 22.

[0036] Specifically, the second servo motor 23 is fixedly mounted on the rotating structure of the turntable 211 via a fixing plate 231. Its output shaft is connected to the sensor bracket 24. Since the TMR sensor module is mounted on the sensor bracket 24 with screws, in this embodiment, the sensor bracket 24 includes a mounting plate for mounting the TMR sensor module and a first connecting plate and a second connecting plate disposed at both ends of the mounting plate. The first connecting plate is connected to the output shaft of the second servo motor 23 via a coupling, and the second connecting plate is rotatably connected to the fixing plate 231 via bearings. Therefore, by driving the sensor bracket 24 to rotate via the second servo motor 23, the TMR sensor module can be driven to perform a pitch rotation of 0~180°, thereby achieving position correction of the TMR sensor module.

[0037] Specifically, in this embodiment, the servo motor drive circuit uses a DRV8837 dual H-bridge drive chip with a peak current of 1.5A and a PWM frequency of 20kHz.

[0038] Specifically, in this embodiment, the universal joint is made of titanium alloy (TC4) with a torsional stiffness ≥100N•m / rad, ensuring positioning deviations caused by no elastic deformation and eliminating flexible vibrations.

[0039] In a specific embodiment, the electronic compass module 3 is a Honeywell HMC5883L magnetoresistive sensor. The circuit diagram design of the electronic compass module is as follows: Figure 6 As shown. Specifically, the Honeywell HMC5883L is a triaxial magnetoresistive sensor with a resolution of 5 mG (milligauss) and a data sampling rate of 100 Hz. The electronic compass can simultaneously measure the magnetic field strength along the X, Y, and Z axes, comprehensively acquiring spatial magnetic field information to accurately calculate azimuth (head, pitch, and roll) angles, providing more accurate pointing data. With a resolution of 5 mG, it can detect weak magnetic field changes, outputting relatively accurate measurement results even in complex or subtly varying environments, meeting the requirements for high-precision azimuth detection. Its communication protocol uses an I2C interface, electrically connecting to the main control module. This communication method requires only two wires (SCL clock line and SDA data line) for data transmission, simplifying wiring, minimizing pin usage on the main control chip, and facilitating integration with other devices in circuit design, reducing hardware design complexity. Simultaneously, it has low power consumption during operation, helping to extend the device's battery life. It possesses a certain degree of anti-interference capability, operating stably in common electromagnetic environments and is not easily affected by magnetic field interference from other surrounding electronic devices, thus maintaining measurement accuracy. At the same time, it can maintain relatively stable performance under different temperature environments.

[0040] In a specific embodiment, the weak magnetic field measuring device further includes a metal shielding box 6; the metal shielding box 6 is provided with the TMR sensor module 1, the angle feedback module, the direction control module 2, the electronic compass module 3 and the main control module 4; and one end face of the metal shielding box 6 is provided with a mounting groove for installing the interaction module 5, and the interaction module 5 is embedded in the mounting groove.

[0041] In a specific embodiment, the metal shielding box 6 includes an inner shell and an outer shell, with a copper foil disposed between the inner shell and the outer shell.

[0042] Specifically, copper foil possesses excellent conductivity, effectively shielding electromagnetic interference. Sandwiching the copper foil between two shells creates a Faraday cage effect, enhancing anti-interference capabilities while maintaining low cost. In this embodiment, the copper foil is secured between the inner and outer shells of the metal shielding box using screws. Alternatively, copper foil (0.1mm) and Mu-metal (0.5mm) can be placed together between the inner and outer shells of the metal shielding box, depending on specific requirements. Furthermore, in this embodiment, the seams of all parts of the metal shielding box are sealed using laser welding.

[0043] Specifically, in this embodiment, a 3.3V DC power supply (VCC3V3) is used to power the TMR sensor circuit. An ESD5341N-ES type transient voltage suppressor (TVS) diode is configured on the power path, which can quickly conduct when encountering transient high voltages, clamping the voltage within a safe range and protecting subsequent circuits from surge impacts. Simultaneously, 0.1μF capacitors C5 and C8 are connected in parallel between the power supply and ground, forming a filter circuit to effectively filter out high-frequency noise in the power supply, ensuring a stable and clean power supply for the TMR2652D chip and other components. The TMR sensor circuit includes a voltage module: the reference voltage (VREF) is externally introduced, providing a reference level for the TMR2652D chip. Two 20pF capacitors C6 and C7 are connected to ground on the VREF line to further filter out high-frequency interference components in the reference voltage, ensuring high accuracy and stability of the reference voltage, thereby improving the detection accuracy and reliability of the TMR sensor. This circuit, through the appropriate combination of TVS diodes, filter capacitors, and other components, significantly enhances the anti-interference capability and stability of the TMR sensor circuit, ensuring the reliable operation of the TMR2652D sensor in complex electromagnetic environments. Simultaneously, the meticulously designed power supply and voltage modules effectively improve the detection accuracy of the TMR sensor, offering significant advantages in detection accuracy and response speed compared to traditional designs, thus possessing high practical value and market competitiveness. Compared with existing weak magnetic field detection equipment, the advantages of this invention are as follows: (1) This utility model adopts a TMR2652D sensor and electronic compass collaborative measurement scheme. By combining a low-noise amplifier and multi-stage amplification circuit, and with a 0.1Hz-1kHz bandpass filter design, the sensitivity of weak magnetic field detection reaches 0.1nT level, which is more than 100 times higher than that of traditional sensors. The integrated direction control module calibrates the TMR sensor direction in real time through a dual-axis servo motor (full stroke response time <0.5s). Combined with the electronic compass heading data, the measurement error is reduced from ±5% to ±0.3% (actual measurement data). The metal shell adopts a copper foil structure, supports wide temperature range of -40℃ to 85℃, and the power consumption of the whole machine is as low as 2.5mA@3.3V. It is suitable for long-distance high-precision detection in mobile scenarios such as UAV magnetic measurement and medical magnetic detection.

[0044] (2) This utility model incorporates a Kalman filter algorithm and a dynamic calibration mechanism. Through real-time comparison of electronic compass direction data and TMR magnetic field strength (deviation threshold ±5%), it achieves three-dimensional vector modeling and anomaly self-checking. It integrates a TFT display module (resolution ≥320×480) and a SYN6288 voice chip, supporting magnetic field strength-time curves, three-dimensional direction arrows, and voice broadcast functions (delay <200ms), improving interaction efficiency. The device of this utility model adopts a modular design, is compatible with I2C / SPI communication protocols, adapts to automated packaging platforms, reduces production costs by 30%, and is suitable for industrial non-destructive testing, intelligent navigation, and geological exploration.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A weak magnetic field measurement device based on a TMR sensor, characterized in that, include: The TMR sensor module (1), the angle feedback module, the direction control module (2) for adjusting the position of the TMR sensor module, the electronic compass module (3), the main control module (4), the interaction module (5), and the metal shielding box (6). The metal shielding box (6) contains the TMR sensor module (1), angle feedback module, direction control module (2), electronic compass module (3) and main control module (4). Furthermore, one end face of the metal shielding box is provided with a mounting groove for installing the interactive module (5), and the interactive module (5) is embedded in the mounting groove; The TMR sensor module (1) is used to acquire magnetic field strength signals; The angle feedback module is used to provide real-time feedback of the position signal of the direction control module (2) to the main control module; The direction control module (2) includes: a rotating bracket (21) with a turntable (211), a first servo motor (22), a second servo motor (23), and a sensor bracket (24) for mounting the TMR sensor module (1). The body of the first servo motor (22) is fixedly connected to the rotating bracket (21), and the output shaft is connected to the turntable (211); The body of the second servo motor (23) is connected to the turntable (211), and the output shaft is connected to the sensor bracket (24); The first servo motor (22) drives the turntable (211) to rotate, thereby driving the TMR sensor module (1) to perform horizontal rotation. The second servo motor (23) drives the sensor bracket (24) to rotate, thereby driving the sensor to rotate. The TMR sensor module (1) performs pitch and rotation motion; The electronic compass module (3) is used to acquire magnetic field direction signals and transmit them to the main control module; The main control module (4) is configured to compare the magnetic field direction given by the electronic compass module (3) with the current orientation of the TMR sensor module (1), generate a rotation command to drive the first servo motor (22) and / or the second servo motor (23), so that the sensitive axis of the TMR sensor module (1) is aligned with the direction of the magnetic field to be measured, and control the interactive module (5) to display the measurement result based on the magnetic field strength signal output by the TMR sensor module (1) after the position is corrected.

2. The weak magnetic field measurement device based on a TMR sensor according to claim 1, characterized in that, The TMR sensor module (1) uses a TMR2652D sensor.

3. The weak magnetic field measurement device based on a TMR sensor according to claim 1, characterized in that, The electronic compass module (3) uses a Honeywell HMC5883L magnetoresistive sensor.

4. The weak magnetic field measurement device based on a TMR sensor according to claim 1, characterized in that, The metal shielding box (6) includes an inner shell and an outer shell, with copper foil disposed between the inner shell and the outer shell.

5. The magnetic field weakening measurement device based on a TMR sensor according to claim 1, characterized in that, The angle feedback module is integrated inside the direction control module (2).

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