Digital fluxgate sensor with software correction and temperature monitoring functions

Abstract

A digital fluxgate sensor with software correction and temperature monitoring is composed of a probe module, an excitation conditioning module and a data acquisition module, and the probe module is communicated with the excitation conditioning module through electric signals; the excitation conditioning module is in electric signal communication with the data acquisition module; the probe module converts an invisible magnetic signal into a measurable electric signal and outputs the measurable electric signal to the excitation conditioning module; the excitation conditioning module detects, extracts and amplifies weak signals output by the probe module, and outputs the weak signals to the data acquisition module; the data acquisition module performs AD conversion and then interacts a command with the peripheral. Through high integration, many problems originally needing to be solved by a user are perfectly solved in the sensor, and stable, reliable and easy-to-use digital data are directly output.

Description

Technical Field

[0001] This invention relates to the field of weak magnetic field measurement technology, specifically a digital fluxgate sensor with software correction and temperature monitoring for measuring weak magnetic fields. Background Technology

[0002] The fluxgate sensor is a high-precision magnetic field measuring instrument based on the principle of magnetic saturation. It has the advantages of wide measurement range, high resolution and good stability, and is widely used in geophysical exploration, space magnetic field detection, industrial non-destructive testing, navigation systems and biomedicine.

[0003] With technological advancements, the performance requirements for fluxgate sensors are increasingly stringent, particularly regarding long-term stability, reliability, and field maintainability. However, traditional fluxgate sensors still face two significant technical bottlenecks in practical applications: (1) High system complexity: The sensor output is an analog voltage signal, which requires the user to design additional data acquisition equipment (including analog filtering circuit, ADC sampling circuit and MCU, etc.) for digital processing, which increases the complexity of system design. When the sensor is used in conjunction with the user-designed data acquisition equipment, complex electromagnetic compatibility issues may also arise.

[0004] (2) Complex parameter calibration: The fluxgate sensor must be calibrated in a system-level manner with the matching data acquisition equipment. The key parameters such as sensitivity and zero offset obtained from the calibration should be stored in the non-volatile memory of the data acquisition equipment. The serial number of each sensor must correspond one-to-one with the serial number of its data acquisition equipment. If the sensor is connected to an unpaired acquisition equipment, the original calibration parameters will be invalid and the system must be recalibrated in order to ensure measurement accuracy and data validity.

[0005] (3) Inherent defects of analog signal links: Long-distance transmission of analog signals is susceptible to electromagnetic interference, leading to a decrease in signal-to-noise ratio. Analog integrators and other components suffer from integration drift, affecting long-term stability. In addition, analog systems are not conducive to nonlinear correction and advanced algorithm processing, limiting further improvement of sensor performance.

[0006] (4) Temperature Drift Problem: The physical characteristics and electrical parameters of the core sensitive elements (such as the magnetic core) and signal conditioning circuits (such as oscillators, amplifiers, phase-sensitive detectors, etc.) of fluxgate sensors are highly sensitive to changes in ambient temperature. Temperature fluctuations directly cause drift in the permeability and coercivity of the magnetic core, the inductance and resistance of the coil, and the performance of semiconductor components. These changes ultimately manifest as zero-point drift and sensitivity drift in the sensor output signal, collectively referred to as temperature drift, which is the most significant factor affecting the measurement accuracy and long-term stability of fluxgate sensors. Fluxgate sensors inevitably experience temperature changes in actual working environments. Because the temperature of the core components (especially the magnetic core) of the sensor cannot be sensed in real time and accurately, the system cannot perform effective real-time temperature compensation. Therefore, its output signal contains temperature errors that cannot be distinguished or eliminated, resulting in unreliable measurement data in high-precision application scenarios. Furthermore, when the sensor output drifts, the lack of temperature data makes it difficult for maintenance personnel to quickly determine whether the cause is a change in the external magnetic field, a fault in the sensor itself, or simply an influence of the ambient temperature. This poses significant challenges to troubleshooting and system status monitoring, and reduces the overall reliability of the system.

[0007] (5) Lack of effective self-testing function: As a critical measuring device, the health of fluxgate sensors is of paramount importance. Especially in safety-critical fields such as aerospace and unmanned systems, it is necessary to ensure that the sensors are always in normal working order. However, most existing fluxgate sensors do not have online self-testing capabilities. Operators or the system cannot quickly diagnose whether the sensor has malfunctioned without power interruption or disassembly. Current detection methods usually rely on periodic offline calibration or return-to-factory testing, which is not only cumbersome and time-consuming, but also fails to achieve early prediction and warning of faults, which may lead to the failure of the entire system due to latent sensor faults, resulting in safety risks.

[0008] Traditional temperature compensation methods often employ hardware circuits, such as using thermistor networks for analog compensation. These methods suffer from drawbacks including limited compensation accuracy, complex circuitry, poor consistency, high cost, and difficulty in fine-tuning for each sensor. With the development of digital technology, software compensation has become a better option. However, existing software compensation algorithms often have simple models or fail to fully consider the complex nonlinear relationship between fluxgate sensor error and temperature, resulting in poor compensation performance across the entire temperature range (e.g., -20°C to +60°C), and there is still room for improvement in stability and accuracy. Summary of the Invention

[0009] This invention provides a fluxgate sensor and its application, fundamentally solving the technical problems of low system integration, complex calibration, large temperature drift error, and poor flexibility of traditional fluxgate sensor systems. It also integrates a convenient and reliable self-testing mechanism and can be applied to handheld magnetometers. Addressing the issues of existing handheld magnetometers having a single calibration method, inability to dynamically adapt to complex environments, and difficulty in balancing high precision and low power consumption, this invention establishes a unified error model, combines multiple error corrections with attitude calculation, and performs collaborative optimization at the algorithm and hardware levels. Ultimately, it achieves a balance of high precision, high stability, and low power consumption on handheld devices.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A fluxgate sensor includes a power supply circuit (1), characterized in that the power supply circuit (1) is connected to an excitation conditioning module (3), the excitation conditioning module (3) is connected to a probe module (2), and the excitation conditioning module (3) includes an excitation circuit (4) connected to a signal conditioning circuit (5).

[0011] The excitation circuit (4) includes an excitation source (41), a frequency doubling phase shifting circuit (42), and a power amplifier circuit (43); the excitation source (41) is connected to the frequency doubling phase shifting circuit (42), and the frequency doubling phase shifting circuit (42) is connected to the power amplifier circuit (43) and the phase-sensitive detector circuit (52).

[0012] The signal conditioning circuit (5) includes a frequency selection circuit (51), a phase-sensitive detector circuit (52), an integrator circuit (53), and a feedback circuit (54); the frequency selection circuit (51) is connected to the phase-sensitive detector circuit (52); the phase-sensitive detector circuit (52) is connected to the frequency doubling and phase shifting circuit (42) and the integrator circuit (53); the integrator circuit (53) is connected to the feedback circuit (54).

[0013] The power supply circuit (1) performs voltage reduction and filtering on the power supply to power each module circuit. It realizes the momentary on / off control and the distribution of power to each part of the circuit.

[0014] The excitation circuit (4) provides excitation current to the excitation coil.

[0015] The signal conditioning circuit (5) extracts the external magnetic field information from the output signal of the fluxgate sensor and performs signal processing such as filtering, integration, and amplification to measure the magnitude of the ambient magnetic field. Furthermore, one implementation scheme:

[0016] The power supply circuit (1) is connected to the temperature acquisition circuit (6) and the self-test circuit (7).

[0017] The probe module (2) integrates a triaxial sensing probe (21), a non-magnetic platinum resistance PT100 (23), and a triaxial self-test coil (22).

[0018] The feedback circuit (54) is connected to the triaxial sensing probe (21).

[0019] The power amplifier circuit (43) is connected to the triaxial induction probe (21).

[0020] The frequency selection circuit (51) is connected to the triaxial induction probe (21).

[0021] The temperature acquisition circuit (6) includes a constant current circuit (61), an MCU main control circuit (62), and an RS485 conversion circuit (63). The signal input terminal of the constant current circuit (61) is connected to a non-magnetic platinum resistor PT100 (33), and the signal output terminal is connected to the MCU main control circuit (62). The output terminal of the MCU main control circuit (62) is connected to the RS485 conversion circuit (63). The RS485 conversion circuit (63) communicates with external devices. The temperature acquisition circuit (6) converts the temperature information of the probe position into an analog voltage signal and sends it out.

[0022] The self-test circuit (7) includes an optocoupler isolation circuit (71), an oscillator (72) and a drive circuit (73); the optocoupler isolation circuit (71) is connected to the oscillator (72); the oscillator (72) is connected to the signal drive circuit (73), and the drive circuit (73) is connected to the self-test coil (22). Furthermore, another implementation plan is:

[0023] The power supply circuit (1) is also connected to the digital acquisition module (8).

[0024] The probe module (2) is a three-component magnetic probe that senses and reacts to the signal of the external magnetic field, and at the same time generates a reference signal for the phase-sensitive demodulator, which is used to detect the external magnetic field signal.

[0025] The frequency selection circuit (51), feedback circuit (54) and power amplifier circuit (43) of the excitation conditioning module (3) are connected to the probe module (2); the integration circuit (53) is connected to the front-end filter circuit (61).

[0026] The data acquisition module (8) includes a front-end filter circuit (81), an AD conversion circuit (82), an MCU main control circuit (83), a temperature sensor (84), and an acceleration sensor (85). The front-end filter circuit (81) is connected to the AD conversion circuit (82), the AD conversion circuit (82) is connected to the temperature sensor (84), and the MCU main control circuit (83) is connected to the acceleration sensor (85). The MCU main control circuit (83) is equipped with embedded acquisition software (9).

[0027] The data acquisition module (8) has digital output and can communicate with external devices via serial port (TTL) or with a computer via USB.

[0028] The embedded acquisition software (9) integrates magnetic field sensitivity correction, zero drift correction, temperature correction and orthogonality correction functions, and uses SPI to acquire acceleration information, converts acceleration information into tilt information, integrates magnetic field, tilt angle and temperature information, and sends it to the outside in real time. At the same time, it also includes AD conversion communication control, tilt angle calculation control, serial port (TTL) communication control and peripheral interaction commands. Further applications of fluxgate sensors:

[0029] A temperature compensation method for a fluxgate sensor with integrated temperature monitoring and self-testing functions for weak magnetic fields, characterized by comprising the following steps: Step 1: Temperature Calibration Step 2: Multi-temperature point magnetic field calibration and data acquisition: Step 3, Embedded Model and Real-time Compensation: Step 4: Output the final result: Furthermore, fluxgate sensors are applied to handheld magnetometers:

[0030] The invention includes a fluxgate sensor, characterized in that the fluxgate sensor is connected to a handheld watch via a cable.

[0031] The fluxgate sensor described above adopts one of the above-described implementation schemes.

[0032] The handheld watch includes an LCD touch screen module and a display control module. The display control module includes an MCU main control circuit, an LCD screen control circuit, a communication interface circuit, and a power management circuit. The LCD screen control circuit provides power and a communication interface to connect to the LCD touch screen module.

[0033] The touchscreen operation and display software functions of the handheld watch include: magnetic field value display, tilt angle value display, power management function, serial port (TTL) communication control, and interaction function with digital magnetic sensor.

[0034] The aforementioned LCD touchscreen module includes an LCD screen driving circuit that drives the LCD touchscreen.

[0035] The MCU main control circuit described above realizes data processing, transmission, and business operation control of the LCD screen; The LCD screen control circuit provides a power supply and communication interface to connect to the LCD touch screen module (7); The communication interface circuit communicates with the digital magnetic sensor via a serial port; and connects to a PC via a Type-C interface to read internal flash data. Furthermore, a magnetic field fusion correction method for temperature monitoring using a handheld magnetometer:

[0036] Includes the following steps: Step 1: Data Acquisition and Preprocessing Step 2: Establish a comprehensive error compensation model: Step 3: Parameter Calibration and Learning Step 4: Online real-time fusion calibration.

[0037] The beneficial effects of this invention are: This sensor accurately measures magnetic field vector information and integrates real-time temperature monitoring and self-testing functions. The temperature acquisition circuit monitors environmental and internal sensor temperature changes in real time, providing accurate and reliable input for the temperature compensation algorithm. The self-testing circuit automatically verifies the normal operation of the system without external calibration, significantly improving maintainability and ease of operation. It also supports online program upgrades. Using the built-in bootloader and RS485 standard communication interface, users can directly update the sensor's internal firmware without disassembling it. This feature not only facilitates future function expansion and algorithm optimization but also greatly enhances the system's flexibility and lifespan, making it particularly suitable for long-term deployments or applications in harsh environments.

[0038] It achieves precise measurement of magnetic field vector information and integrates temperature and tilt angle measurement functions, significantly enhancing the sensor's environmental adaptability and data reliability. On the same platform, it systematically integrates magnetic field sensitivity correction, zero drift correction, temperature correction, and orthogonality correction functions. Through embedded advanced algorithms and calibration software, the sensor can automatically compensate for various errors introduced by environmental changes, component aging, and non-ideal orthogonal structures, thus maintaining extremely high measurement accuracy across the entire temperature range and under complex operating conditions.

[0039] This sensor features embedded software-based online calibration and real-time temperature and attitude monitoring capabilities, while also boasting excellent low noise and low power consumption characteristics. It completely solves the problems of low integration, complex calibration, large temperature drift error, and poor flexibility inherent in traditional magnetic sensor systems. This sensor is particularly suitable for cutting-edge fields with extremely high requirements for measurement accuracy, reliability, and integration, such as high-precision navigation, resource exploration, space physics detection, and intelligent manufacturing.

[0040] Featuring magnetic field vector measurement, real-time temperature monitoring, and self-testing capabilities, along with a built-in temperature compensation algorithm and online program upgrade capabilities, this sensor completely solves the problem of large temperature drift errors inherent in traditional magnetic sensors, significantly improving maintenance efficiency and product lifecycle after large-scale deployment. This sensor is particularly suitable for high-end industrial and scientific research fields with stringent requirements for measurement accuracy, environmental adaptability, and low maintenance costs.

[0041] It achieves magnetic field fusion calibration, sensitivity correction, zero bias correction, temperature correction and orthogonality correction functions, while realizing a handheld magnetometer with low noise, low power consumption, portable operation and stable operation.

[0042] High calibration accuracy and robustness: By establishing a unified comprehensive error model, the coupling relationship of multiple error sources is taken into consideration, and attitude data is combined for fusion calculation, realizing the leap from "single correction" to "system-level collaborative correction", which significantly improves the measurement accuracy and stability in various complex environments.

[0043] Excellent user experience: The calibration process is partially automated, allowing users to obtain reliable measurement results without requiring extensive professional knowledge. The handheld design and user-friendly interface make operation simple and intuitive. Attached Figure Description

[0044] Figure 1 This is a block diagram of the components of the present invention.

[0045] Figure 2 This is a flowchart of the sensor-embedded acquisition software 5 of the present invention.

[0046] Figure 3 This is a schematic diagram of another embodiment.

[0047] Figure 4 This is a block diagram showing the connection components of the present invention; Figure 5 This is a hardware block diagram of the digital magnetic sensor of the present invention; Figure 6 This is a hardware block diagram of the handheld watch of the present invention; Figure 7 This is a flowchart of the digital magnetic sensor embedded acquisition software 6 of the present invention; Figure 8 This is a flowchart of the handheld watch embedded touchscreen operation and display software 9 of the present invention; Figure 9 This is a schematic diagram showing the sensitivity and temperature fitting of the digital magnetic sensor embedded in this invention; Figure 10 This is a schematic diagram of the zero bias and temperature fitting embedded in the digital magnetic sensor of the present invention.

[0048] In this circuit, 1 is the power supply circuit, 2 is the probe module, 3 is the excitation circuit, 5 is the signal conditioning circuit, 6 is the temperature acquisition circuit, 7 is the self-test circuit, 8 is the data acquisition module, 9 is the embedded acquisition software, 31 is the triaxial sensing probe, 32 is the triaxial self-test coil, and 33 is the PT100 platinum resistance thermometer; 41 is the excitation source, 42 is the frequency doubling and phase shifting circuit, and 43 is the power amplifier circuit; 51 is the frequency selection circuit, 52 is the phase-sensitive detection circuit, 53 is the integrating circuit, and 54 is the feedback circuit; 61 is the constant current circuit, 62 is the MCU main control circuit, and 63 is the RS485 conversion circuit; 71 is the optocoupler isolation circuit, 72 is the oscillator, and 73 is the drive circuit; 81 is the front-end filter circuit, 82 is the AD conversion circuit, 83 is the MCU main control circuit, 84 is the temperature sensor, and 85 is the accelerometer. Detailed Implementation

[0049] The invention will be further described below with reference to the accompanying drawings.

[0050] like Figure 1 , 3 As shown, a fluxgate sensor includes a power supply circuit (1), characterized in that the power supply circuit (1) is connected to an excitation conditioning module (3), the excitation conditioning module (3) is connected to a probe module (2), and the excitation conditioning module (3) includes an excitation circuit (4) connected to a signal conditioning circuit (5).

[0051] The excitation circuit (4) includes an excitation source (41), a frequency doubling phase shifting circuit (42), and a power amplifier circuit (43); the excitation source (41) is connected to the frequency doubling phase shifting circuit (42), and the frequency doubling phase shifting circuit (42) is connected to the power amplifier circuit (43) and the phase-sensitive detector circuit (52).

[0052] The signal conditioning circuit (5) includes a frequency selection circuit (51), a phase-sensitive detector circuit (52), an integrator circuit (53), and a feedback circuit (54); the frequency selection circuit (51) is connected to the phase-sensitive detector circuit (52); the phase-sensitive detector circuit (52) is connected to the frequency doubling and phase shifting circuit (42) and the integrator circuit (53); the integrator circuit (53) is connected to the feedback circuit (54).

[0053] The power supply circuit (1) performs voltage reduction and filtering on the power supply to power each module circuit. It realizes the momentary on / off control and the distribution of power to each part of the circuit.

[0054] The probe module (2) is used to sense the external magnetic field and convert the invisible magnetic signal into a measurable electrical signal, which is then output to the signal conditioning circuit.

[0055] The excitation circuit (4) provides excitation current to the excitation coil and provides a high-frequency alternating excitation signal to the probe module. The excitation source in the excitation circuit is used to provide a highly stable frequency signal to the excitation circuit. The frequency doubling and phase shifting circuit precisely controls the frequency relationship between the excitation frequency f and the second harmonic signal 2f, and maximizes the phase-sensitive detection signal by adjusting the phase of the excitation coil. The power amplifier circuit amplifies the weak excitation signal generated by the previous stage and outputs a sufficiently powerful, pure waveform and stable amplitude alternating current to the excitation coil of the triaxial induction probe, driving the magnetic core to periodically enter a deep saturation state, laying the necessary physical foundation for the sensor to sense the external magnetic field.

[0056] The signal conditioning circuit (5) extracts the external magnetic field information from the output signal of the fluxgate sensor and performs signal processing such as filtering, integration, and amplification to measure the magnitude of the ambient magnetic field and output it to the external data acquisition device. Example

[0057] like Figure 1 As shown, one implementation scheme is: The power supply circuit (1) is connected to the temperature acquisition circuit (6) and the self-test circuit (7).

[0058] The probe module (2) integrates a triaxial sensing probe (21), a non-magnetic platinum resistor PT100 (23), and a triaxial self-test coil (22), which can monitor the ambient magnetic field temperature. The probe module contains a self-test coil, and the self-test circuit drives the self-test coil to generate a self-test magnetic field.

[0059] The feedback circuit (54) is connected to the triaxial sensing probe (21).

[0060] The power amplifier circuit (43) is connected to the triaxial induction probe (21).

[0061] The frequency selection circuit (51) is connected to the triaxial induction probe (21).

[0062] The temperature acquisition circuit (6) includes a constant current circuit (61), an MCU main control circuit (62), and an RS485 conversion circuit (63). The signal input terminal of the constant current circuit (61) is connected to a non-magnetic platinum resistor PT100 (33), and the signal output terminal is connected to the MCU main control circuit (62). The output terminal of the MCU main control circuit (62) is connected to the RS485 conversion circuit (63), which communicates with external devices. The resistance value of PT100 is acquired and converted into a voltage value by the constant current circuit.

[0063] The self-test circuit (7) includes an optocoupler isolation circuit (71), an oscillator (72) and a drive circuit (73); the optocoupler isolation circuit (71) is connected to the oscillator (72); the oscillator (72) is connected to the signal drive circuit (73), and the drive circuit (73) is connected to the self-test coil (22).

[0064] The analog voltage output interface is used to output an analog signal representing the magnetic field strength; the RS485 digital communication interface is used to output a digital signal containing temperature information.

[0065] The temperature acquisition circuit (6) acquires the resistance value of PT100 and converts it into a voltage value through a constant current circuit. The MCU main control circuit processes it and converts it into a temperature digital signal. The self-test circuit can generate a constant magnetic field to detect whether the working state of the magnetic sensor is normal.

[0066] The PT100 non-magnetic platinum resistance thermometer uses a non-magnetic material design and packaging process, which can effectively avoid the introduction of additional magnetic field interference and ensure that the performance of the fluxgate sensor is not affected in sensitive magnetic field measurement scenarios. It is used for real-time monitoring of ambient temperature with an accuracy of ±0.15℃.

[0067] The temperature acquisition circuit incorporates a software-integrated temperature compensation algorithm. This algorithm effectively identifies measurement errors caused by fluctuations in ambient temperature and corrects and compensates for them through software, significantly improving the stability and accuracy of temperature measurement across the entire temperature range. This effectively solves the technical challenge of traditional fluxgate sensors being greatly affected by temperature.

[0068] Upon receiving a command, the self-test circuit actively generates a standard excitation magnetic field of known intensity and frequency to verify the sensor's operating status and the integrity of the measurement link. The self-test process involves applying a magnetic field signal through a built-in self-test coil, which the sensor then acquires and processes. If the output signal matches the expected calibration value, it indicates that the sensor is functioning normally and the measurement accuracy is reliable. If a significant deviation exists, the system automatically indicates a fault or requires calibration, greatly improving the system's reliability and maintainability.

[0069] The fluxgate sensor provides two independent signal output interfaces to meet the needs of different system integrations and signal processing. The analog voltage output interface reflects the intensity of the measured magnetic field in real time, outputting a high-precision analog voltage that is linearly related to the magnetic field strength. The voltage signal uses a differential output method, offering high anti-interference capability and signal-to-noise ratio, facilitating long-distance transmission and allowing direct connection to data acquisition cards, oscilloscopes, or analog control units. It is suitable for scenarios requiring real-time, high-speed acquisition of magnetic field changes. The RS485 digital signal output interface is specifically designed for transmitting temperature information. Based on the RS485 standard bus protocol, it has excellent common-mode interference immunity and supports long-distance communication. Temperature data is acquired by a built-in high-precision temperature sensor (PT100), processed by the MCU, and output as a digital signal. Users can read the ambient temperature value in real time through this interface.

[0070] The aforementioned fluxgate sensor features online program upgrade capability. This function, through the built-in bootloader program and RS485 standard communication interface, allows for direct firmware updates to the sensor without disassembling it. This feature enables continuous algorithm optimization, potential problem fixing, compatibility with new protocols, or expansion of new functions after deployment, significantly improving the product's adaptability, maintainability, and lifespan. It is particularly suitable for high-end industrial and scientific research applications requiring long-term embedded operation, large-scale deployment, or where disassembly is difficult.

[0071] The induction coil of the triaxial induction probe generates an electrical signal characterized primarily by second harmonics. The amplitude of this signal is linearly proportional to the strength of the external DC magnetic field being measured, providing the raw signal for subsequent signal processing circuits. The phase-sensitive detector circuit in the signal conditioning circuit not only extracts the amplitude information characterizing the magnetic field magnitude but also retains the phase information reflecting the magnetic field direction and significantly suppresses various types of noise, ultimately outputting a stable, accurate voltage signal with directional characteristics. The integrator and feedback circuits together constitute a high-precision balanced closed-loop system. The integrator, as the core control unit, drives the feedback loop through the integration error signal, generating a compensation magnetic field that accurately cancels out the external magnetic field. Ultimately, the magnetic field measurement is converted into a measurement of a stable compensation current, thus achieving extremely high accuracy, linearity, and stability.

[0072] The MCU main control circuit processes the signal and converts it into a digital temperature signal. The RS485 conversion circuit further converts the temperature signal into an RS485 digital protocol to enable communication with external devices.

[0073] The probe module integrates a triaxial self-test coil. The optocoupler isolation circuit in the self-test circuit provides electrical isolation from external self-test control commands, effectively preventing external interference from affecting the normal operation of the sensor circuit. After receiving the self-test command, the oscillator generates a square wave signal of a fixed frequency, which is amplified by the drive circuit and then drives the self-test coil to generate a self-test magnetic field.

[0074] The fluxgate sensor integrates a self-test coil and a self-test circuit. This circuit uses an optocoupler to electrically isolate external self-test control commands, effectively preventing external interference from affecting the normal operation of the sensor circuit. Upon receiving a self-test command, it generates a square wave signal of a fixed frequency. After power amplification by the drive circuit, this signal drives the self-test coil to generate a standard excitation magnetic field of known strength and frequency. The sensor collects and processes this signal to verify its operating status and the integrity of the measurement link. The self-test function can be activated periodically or as needed to verify the sensor's operating status. This fluxgate sensor, by integrating a self-test function, effectively solves the core problems of traditional sensors, such as unknowable status, susceptibility to interference, cumbersome on-site calibration, and difficult remote maintenance. It achieves autonomous verification of the sensor's operating status and the measurement link, significantly improving system reliability, anti-interference capability, and maintainability, and reducing long-term operating costs. It is particularly suitable for industrial and field monitoring scenarios with high reliability requirements.

[0075] This fluxgate magnetometer sensor integrates three core functions: weak magnetic field measurement, temperature monitoring, and self-testing. Its weak magnetic field measurement capability reaches the nT level, featuring high resolution and low noise, making it suitable for applications sensitive to subtle changes in magnetic fields. The built-in temperature monitoring function acquires temperature data in real time through a high-precision non-magnetic platinum resistance thermometer and temperature acquisition circuit. External devices can use this temperature information to perform real-time digital compensation for the magnetic field measurement results, effectively suppressing temperature drift caused by ambient temperature changes and improving the sensor's measurement accuracy and stability. The self-testing function can be activated periodically or as needed to verify the sensor's operating status, ensuring reliable long-term continuous operation and reducing the frequency and cost of on-site calibration and maintenance. Example

[0076] like Figure 2 As shown, a fluxgate sensor application, specifically a temperature compensation method for a fluxgate sensor with integrated temperature monitoring and self-testing functions for weak magnetic fields, is characterized by comprising the following steps: Step 1: Temperature Calibration Before leaving the factory, the temperature sensor built into the fluxgate sensor and the third-party calibrated temperature sensor are placed in a temperature chamber. Temperature tests are performed at multiple stable temperature points T_i (i=1, 2, ..., N) within a predetermined full temperature range (e.g., -20℃, -10℃, 0℃, 10℃, 25℃, 40℃, 60℃). Temperature fitting is performed using the temperature T1_i (i=1, 2, ..., N) measured by the built-in temperature sensor and the temperature T0_i (i=1, 2, ..., N) measured by the third-party calibrated temperature sensor. The function is preferably a piecewise linear function or a second-order / third-order polynomial function.

[0077] T0 = ​​k0 + k1 * T1+ k2 * T1^2; Where k0, k1, and k2 are the model coefficients obtained by fitting using the least squares method.

[0078] Step 2: Multi-temperature point magnetic field calibration and data acquisition: Before leaving the factory, the temperature built into the fluxgate sensor is calibrated and placed in a temperature chamber. Within a predetermined full temperature range (e.g., -20℃, -10℃, 0℃, 10℃, 25℃, 40℃, 60℃), the corrected temperature T_i (i=1, 2, ..., N) is measured at multiple stable temperature points, and the following operations are performed: In a zero magnetic field environment, measure the zero-position output value M_offset(T_i) of the sensor.

[0079] Under a known standard magnetic field B_ref, measure the full-scale output value M_fullscale(T_i) of the sensor.

[0080] Establish a temperature error model: Based on the data collected in step 2, a zero-point drift error model and a sensitivity drift error model are established respectively.

[0081] Zero-point drift model: Fits the zero-point output value V_offset(T) to a function of temperature T. This function is preferably a piecewise linear function or a second / third-order polynomial function. For example: M_offset(T) = a0 + a1 * T + a2 * T^2 Where a0, a1, and a2 are the model coefficients obtained by fitting using the least squares method.

[0082] Sensitivity calculation: Calculate the sensitivity at each temperature point; S(T_i) = (M_fullscale(T_i) - M_offset(T_i)) / B_ref.

[0083] Sensitivity drift model: The sensitivity S(T) is fitted as a function of temperature T. This function is preferably a piecewise linear function or a second / third-order polynomial function. For example: S(T) = b0 + b1 * T + b2 * T^2; Where b0, b1, and b2 are the model coefficients obtained by fitting using the least squares method.

[0084] Step 3, Embedded Model and Real-time Compensation: The temperature calibration model coefficients (k0, k1, k2,...), zero-point drift model coefficients (a0, a1, a2,...), and sensitivity drift model coefficients (b0, b1, b2,...) determined in steps 1 and 2 are stored in the non-volatile memory of the fluxgate sensor. When the sensor is operating normally, the following real-time compensation process is executed: Synchronous data acquisition: The current ambient temperature T_current is obtained in real time through the built-in temperature sensor, and temperature correction T_est is performed.

[0085] Error calculation: Based on T_est and the zero-offset model, calculate the current zero-offset estimate M_offset_est(T_current).

[0086] Calculate the current sensitivity estimate S_est(T_current) based on T_est and the sensitivity drift model.

[0087] Obtain the sensor's raw, uncompensated magnetic field output value M_raw.

[0088] Compensated Output: Using the calculated zero-point drift and sensitivity estimates, the original output is compensated to obtain the accurate magnetic field measurement value M_compensated. The compensation formula is: M_compensated=(M_raw-M_offset_est(T_est)) / S_est(T_est).

[0089] 4: Output the final result The compensated, precise magnetic field value B_compensated is output as the final measurement result of the sensor. Example

[0090] like Figure 3 As shown, another implementation scheme is: The power supply circuit (1) is also connected to the digital acquisition module (8).

[0091] The probe module (2) is a three-component magnetic probe.

[0092] The frequency selection circuit (51), feedback circuit (54) and power amplifier circuit (43) of the excitation conditioning module (3) are connected to the probe module (2); the integration circuit (53) is connected to the front-end filter circuit (61).

[0093] The data acquisition module (8) includes a front-end filter circuit (81), an AD conversion circuit (82), an MCU main control circuit (83), a temperature sensor (84), and an acceleration sensor (85). The front-end filter circuit (81) is connected to the AD conversion circuit (82), the AD conversion circuit (82) is connected to the temperature sensor (84), and the MCU main control circuit (83) is connected to the acceleration sensor (85). The MCU main control circuit (83) is equipped with embedded acquisition software (9).

[0094] The frequency selection circuit (51), feedback circuit (54) and power amplifier circuit (43) of the excitation conditioning module (3) are connected to the probe module (2); the integration circuit (53) is connected to the front-end filter circuit (61).

[0095] The embedded acquisition software (9) integrates magnetic field sensitivity correction, zero drift correction, temperature correction and orthogonality correction functions, and uses SPI to acquire acceleration information, converts the acceleration information into tilt information, integrates magnetic field, tilt and temperature information, and sends it to the outside in real time.

[0096] The data acquisition module (8) has digital output and can communicate with external devices via serial port (TTL) or with a computer via USB.

[0097] The temperature sensor (84) is a high-precision linear analog temperature sensor with ambient temperature monitoring function.

[0098] The aforementioned accelerometer (85) is a high-precision accelerometer. Through the attitude algorithm embedded in the MCU, it can ultimately output pitch and roll angle information.

[0099] The excitation conditioning module provides a high-frequency alternating excitation signal to the probe module, detects, extracts, and amplifies the weak signal containing external magnetic field information output by the probe module, and outputs it to the data acquisition module; the data acquisition module performs AD conversion on the analog voltage, the MCU processes it and converts it into a digital signal; the embedded acquisition software realizes AD conversion communication control, tilt angle calculation control, serial port (TTL) communication control, and interaction commands with peripherals.

[0100] Equipped with high-precision measurement capabilities in weak magnetic fields, it boasts extremely high accuracy, linearity, and stability. It utilizes precision analog components with low quiescent current (such as operational amplifiers and voltage references) and a low-power microcontroller (MCU) with a built-in high-performance analog-to-digital converter, significantly reducing overall system power consumption at the source. Simultaneously, it carefully selects amplifiers and ADCs with low equivalent noise density (low noise figure) to ensure minimal background noise at the signal chain front-end. This low-noise, low-power design enables the sensor to achieve high performance and long battery life in applications with stringent energy consumption and performance requirements, such as long-term geomagnetic monitoring in the field, space exploration, and portable exploration equipment.

[0101] The embedded acquisition software facilitates the correction of the magnetic field using temperature and tilt information, thereby improving the accuracy of vector magnetic measurements.

[0102] It features digital output and can communicate with external devices via serial port (TTL) or with a computer via USB.

[0103] The tilt angle information can be used to assess the flatness of the environment in which the digital fluxgate sensor is placed. Furthermore, by using this tilt angle information, magnetic field data can be fused and corrected, thereby enabling the measurement of magnetic heading.

[0104] The AD front-end filter circuit performs low-pass filtering on the single-ended voltage signal output by the integrator circuit and converts it into a differential signal. The AD conversion circuit uses two domestic 32-bit ADC chips to simultaneously realize the precise digitization of the analog signal and output it to the MCU main control circuit. The MCU main control circuit provides the minimum system for the entire MCU. The MCU has an embedded program that integrates multiple algorithms to realize magnetic field sampling, attitude information transmission, and correction and compensation of various indicators. The temperature sensor uses a high-precision linear analog temperature sensor, whose output voltage is proportional to the temperature, making it very suitable for various analog temperature measurement and temperature monitoring applications.

[0105] The embedded acquisition software enables AD conversion communication control, tilt angle calculation control, serial port (TTL) communication control, and interaction commands with peripheral devices. The digital fluxgate sensor establishes a communication connection with external devices via serial port (TTL).

[0106] The data acquisition module of the digital fluxgate sensor integrates a high-precision linear analog temperature sensor whose output voltage is proportional to temperature, making it ideal for various analog temperature measurement and monitoring applications. It achieves a typical accuracy of ±0.5°C over a temperature range of 0°C to +85°C, superior to other pin-compatible products on the market. Its output stage employs an AB-class design with a maximum output drive capability of 500μA, sufficient to drive a 1000pF capacitive load, making it ideal for connection to the input stage of an analog-to-digital converter (ADC). Compared to traditional passive thermistors, the analog output temperature sensor offers a cost-effective solution due to its high accuracy and powerful linear output driver.

[0107] The embedded acquisition software in the digital fluxgate sensor integrates magnetic field sensitivity correction, zero drift correction, temperature correction, and orthogonality correction functions, improving the accuracy of vector magnetic measurement. The correction function aims to convert raw, error-laden sensor data into a high-precision, reliable three-dimensional magnetic field vector for orientation measurement. These correction algorithms are integrated into the hardware or firmware, enabling automatic correction and storage—simply triggering the calibration procedure and storing the calibration parameters in the internal flash memory; or manual parameter writing, with corrections completed at the factory calibration and parameters stored in the internal flash memory. The entire process requires multi-information acquisition, employing dual ADCs for magnetic field and temperature acquisition, and using SPI to acquire acceleration information. This acceleration information is converted into tilt angle information, and the magnetic field, tilt angle, and temperature information are integrated and transmitted in real time. This facilitates the use of temperature and tilt angle information to correct the magnetic field, improving the accuracy of vector magnetic measurement. Example

[0108] like Figure 4 As shown, the fluxgate sensor is applied to a handheld magnetometer: The invention includes a fluxgate sensor, characterized in that the fluxgate sensor is connected to a handheld watch via a cable.

[0109] The fluxgate sensor is a sensor equipped with a digital acquisition module (8).

[0110] The fluxgate sensor transmits the analog voltage signal to the digital acquisition module (8).

[0111] The fluxgate sensor (4) includes a three-component probe (2), a power supply circuit (1), an excitation circuit (4), a signal conditioning circuit (5), and a temperature acquisition circuit (6).

[0112] The handheld watch includes an LCD touch screen module and a display control module. The display control module includes an MCU main control circuit, an LCD screen control circuit, a communication interface circuit, and a power management circuit. The LCD screen control circuit provides power and a communication interface to connect to the LCD touch screen module.

[0113] The acceleration module in the data acquisition module (8) uses a high-precision accelerometer.

[0114] The embedded acquisition software (9) includes the following functions: AD conversion communication control, tilt angle calculation control, serial port (TTL) communication control, and interaction commands with peripheral devices.

[0115] The touchscreen operation and display software functions of the handheld watch include: magnetic field value display, tilt angle value display, power management function, serial port (TTL) communication control, and interaction function with digital magnetic sensor.

[0116] The digital magnetic sensor and the embedded interactive software integrated into the handheld watch integrate a magnetic field fusion calibration method that includes sensitivity correction, zero drift correction, temperature correction, and orthogonality correction.

[0117] The excitation circuit (4) provides excitation current to the excitation coil.

[0118] The three-component probe (2) senses the signal of the external magnetic field and generates a reference signal for the phase-sensitive demodulator, which is used to detect the external magnetic field signal.

[0119] The signal conditioning circuit (5) extracts the external magnetic field information from the output signal of the fluxgate sensor and performs signal processing such as filtering, integration, and amplification to measure the magnitude of the ambient magnetic field.

[0120] The temperature acquisition circuit (6) converts the temperature information at the probe position into an analog voltage signal and sends it out.

[0121] The aforementioned front-end processing circuit (81) performs input scaling, low-pass filtering, and single-end to differential conversion on the single-ended signal of the fluxgate sensor.

[0122] The acceleration module (85) uses a domestically produced high-precision accelerometer and provides tilt information from the digital magnetic sensor through the attitude algorithm embedded in the MCU.

[0123] The MCU main control circuit (83) provides the minimum system for the entire MCU. The MCU has an embedded program that integrates multiple algorithms to realize magnetic field sampling, attitude information transmission and magnetic field correction compensation.

[0124] The aforementioned LCD touchscreen module includes an LCD screen driving circuit that drives the LCD touchscreen.

[0125] The MCU main control circuit described above realizes data processing, transmission, and business operation control of the LCD screen; The LCD screen control circuit provides a power supply and communication interface to connect to the LCD touch screen module (7); The communication interface circuit communicates with the digital magnetic sensor via a serial port; it connects to a PC via a Type-C interface to read internal flash data. The power management circuit mainly realizes the jog power-on / off control and the distribution of various circuit parts.

[0126] The display control module in the handheld watch receives magnetic field data and controls the LCD touchscreen module to display the magnetic field information and tilt angle information in a graphical interface. This graphical interface also integrates touch buttons and corresponding operation menus.

[0127] The connection relationships of the various circuits in the digital magnetic sensor are as follows: Figure 5 As shown, after the fluxgate sensor probe senses the magnetic field signal, it is ultimately converted into three analog voltage signals by the internal processing circuit and sent to the AD sampling circuit of the digital acquisition section. The temperature information is directly sent to the internal AD channel of the MCU of the digital acquisition section and finally sent out through the serial port (TTL).

[0128] The connection relationships of each circuit in the handheld meter are as follows: Figure 6 As shown, the digital magnetic sensor transmits the digitized magnetic field and temperature information to the isolated serial port of the handheld meter via a serial port; the internal power acquisition circuit of the handheld meter collects the internal battery voltage and finally displays the power level on the LCD; a large amount of GUI display module data is stored in the SDRAM video memory; the LED status indicator is mainly used for circuit debugging; finally, the magnetic field information, temperature information, power information, and touch screen button operations are presented through the GUI configuration interface program on the LCD display.

[0129] Embedded software includes digital magnetic sensor acquisition software (such as...) Figure 7 ) and the handheld watch's embedded touchscreen operation and display software (such as Figure 8 ).

[0130] The embedded acquisition software of the digital magnetic sensor requires the acquisition of multiple information sources throughout the process. It employs dual ADCs to acquire magnetic field and temperature data, utilizes SPI to obtain acceleration information, converts this acceleration information into tilt angle information, and integrates the magnetic field, tilt angle, and temperature information for real-time transmission. This facilitates the use of temperature and tilt angle information to correct the magnetic field, improving the accuracy of vector magnetic measurements.

[0131] The handheld watch's embedded touchscreen operation and display software utilizes the professional UI design and development software LVGL to build the touchscreen software interface, supporting multiple platforms and various input devices. As a miniature host computer, it is more convenient for outdoor detection. The handheld watch connects to the digital magnetic sensor 1, and through the interaction of commands between the two, it can achieve magnetic measurement, display, and storage functions without external devices. It also integrates low-power management and real-time power detection, which can track the power supply status in real time and instantly enter low-power mode when not in use for a long time, realizing power and low-power management modes in the embedded system. Example

[0132] like Figure 7 As shown, a magnetic field fusion correction method integrating software correction and temperature monitoring is characterized by comprising the following steps: Step 1: Data Acquisition and Preprocessing The original three-axis magnetic field data M_raw=[Mx_r,My_r,Mz_r] is collected by a fluxgate sensor, the acceleration data A_raw=[Ax_r,Ay_r,Az_r] is collected by an accelerometer, the attitude data A=[Pitch,Roll] is calculated, and the temperature data T is collected by a temperature sensor. The original magnetic field data is then subjected to preliminary digital filtering to suppress noise. Step 2: Establish a comprehensive error compensation model: The model unifies zero bias, sensitivity, temperature, and orthogonality error within a single mathematical framework, and its expression is as follows: M_comp = S(T) * O * (M_raw - B(T)); Where: M_raw and M_comp are the triaxial magnetic field vectors before and after compensation, respectively; B(T) is the temperature-dependent zero bias vector [Bx(T), By(T), Bz(T)]; O is a fixed orthogonality error correction matrix used to correct triaxial non-orthogonality; S(T) is the temperature-dependent sensitivity coefficient diagonal matrix diag([Sx(T), Sy(T), Sz(T)]); Step 3: Parameter Calibration and Learning Before leaving the factory or when the user triggers the calibration mode, a large amount of data is collected through a series of specific actions. The key parameters in the model are calculated using the least squares method and stored in non-volatile memory. Temperature changes can cause the magnetic sensor to be less accurate and produce errors, especially the sensitivity and zero bias of the magnetic sensor. Therefore, variable temperature testing is carried out to correct the sensitivity and zero bias, thereby improving the accuracy of the magnetic sensor. Step 4: Online Real-Time Fusion Calibration: In normal measurement mode, the processor executes the following sub-steps: 4-1: Read the current temperature T and retrieve the corresponding B(T) and S(T) from the memory; 4-2: Substitute M_raw, B(T), S(T), and O into the comprehensive error compensation model to calculate the precise triaxial magnetic field value M_comp in the instrument coordinate system; 4-3: Attitude fusion calculation: Combining the tilt angle data [Pitch,Roll], rotate M_comp from the instrument coordinate system to the horizontal geographic coordinate system to obtain M_level=R(θ,φ)*M_comp, where R is the rotation matrix. Calculate the total magnetic field strength F, which is unaffected by attitude, based on M_level.

[0133] The variable temperature test is performed using the following sub-steps: Step 1: Before leaving the factory, calibrate the built-in temperature of the fluxgate sensor and place it in a temperature chamber. Within the predetermined full temperature range (e.g., -20℃, -10℃, 0℃, 10℃, 25℃, 40℃, 60℃), measure the corrected temperature T_i (i=1,2,...,N) at multiple stable temperature points, and then perform the following operations: In a zero magnetic field environment, measure the zero bias output value B(T_i) of the sensor; Under a known standard magnetic field B_ref, measure the full-scale output value M_fullscale(T_i) of the sensor; Step 2: Establish a temperature error model: Based on the data collected in step 1, a zero-point drift error model and a sensitivity drift error model are established respectively. Zero-biased drift model: Fits the zero-biased output value B(T) to a function of temperature T. This function is preferably a piecewise linear function or a second / third-order polynomial function. B(T) = a0 + a1*T + a2*T^2; Where a0, a1, a2 are the model coefficients obtained by fitting using the least squares method.

[0134] Sensitivity calculation: Calculate the sensitivity at each temperature point. S(T_i)=(M_fullscale(T_i)-B(T_i)) / B_ref; Step 3, Sensitivity Temperature Model: Fit the sensitivity S(T) to a function of temperature T. This function is preferably a piecewise linear function or a second / third-order polynomial function. S(T) = b0 + b1*T + b2*T^2; Where b0, b1, and b2 are the model coefficients obtained by fitting using the least squares method.

[0135] The fitting function is as follows Figure 8and Figure 9 As shown.

Claims

1. A digital fluxgate sensor with software correction and temperature monitoring, comprising a power supply circuit (1), characterized in that, The power supply circuit (1) is connected to the excitation conditioning module (3) and the data acquisition module (8). The probe module (2) is connected to the excitation conditioning module (3) by electrical signal; the excitation conditioning module (3) is connected to the data acquisition module (8) by electrical signal.

2. A digital fluxgate sensor with software correction and temperature monitoring as described in claim 1, characterized in that, The probe module (2) is a three-component magnetic probe.

3. A digital fluxgate sensor with software correction and temperature monitoring according to claim 1, characterized in that, The excitation conditioning module (3) includes an excitation source (31), a frequency doubling and phase shifting circuit (32), a power amplifier circuit (33), a frequency selection circuit (34), a phase-sensitive detector circuit (35), an integrator circuit (36), and a feedback circuit (37). The excitation source (31) is connected to the frequency doubling and phase shifting circuit (32), and the frequency doubling and phase shifting circuit (32) is connected to the power amplifier circuit (33). The frequency doubling and phase shifting circuit (32) is connected to the phase-sensitive detector circuit (35). The phase-sensitive detector circuit (35) is connected to the frequency selection circuit (34) and the integrator circuit (36). The integrator circuit (36) is connected to the feedback circuit (37). The frequency selection circuit (34), the feedback circuit (37), and the power amplifier circuit (33) are connected to the probe module (2). The integrator circuit (36) is connected to the front-end filter circuit (42).

4. A digital fluxgate sensor with software correction and temperature monitoring as described in claim 1, characterized in that, The data acquisition module (8) includes a front-end filter circuit (81), an AD conversion circuit (82), an MCU main control circuit (83), a temperature sensor (84), and an acceleration sensor (85). The front-end filter circuit (81) is connected to the AD conversion circuit (82), the AD conversion circuit (82) is connected to the temperature sensor (84), and the MCU main control circuit (83) is connected to the acceleration sensor (85). The MCU main control circuit (83) is equipped with embedded acquisition software (9).

5. A digital fluxgate sensor with software correction and temperature monitoring according to claim 4, characterized in that, The embedded acquisition software (5) integrates magnetic field sensitivity correction, zero drift correction, temperature correction and orthogonality correction functions, and uses SPI to acquire acceleration information, converts the acceleration information into tilt information, integrates magnetic field, tilt and temperature information, and sends it to the outside in real time.

6. A digital fluxgate sensor with software correction and temperature monitoring according to claim 4, characterized in that, The data acquisition module (8) has digital output and can communicate with external devices via serial port (TTL) or with a computer via USB.

7. A digital fluxgate sensor with software correction and temperature monitoring according to claim 4, characterized in that, The temperature sensor (84) is a high-precision linear analog temperature sensor with ambient temperature monitoring function.

8. A digital fluxgate sensor with software correction and temperature monitoring according to claim 4, characterized in that, The aforementioned accelerometer (85) is a high-precision accelerometer. Through the attitude algorithm embedded in the MCU, it can ultimately output pitch and roll angle information.

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