Digital vector magnetometer with low resource consumption based on magnetoresistive sensor

Abstract

The utility model relates to the technical field of magnetic field detection, and discloses a digital vector magnetometer with low resource consumption based on a magnetoresistive sensor. The low-resource-consumption digital vector magnetometer based on the magnetoresistive sensor comprises the magnetoresistive sensor which is used for detecting an external magnetic field and converting the external magnetic field into an electric signal, and the magnetoresistive sensor is made of an anisotropic magnetoresistive material; the amplifier is connected to the signal output end of the magnetoresistive sensor and is used for amplifying the weak electric signal output by the magnetoresistive sensor; the AD converter is connected to the signal output end of the amplifier and used for converting the electric signal amplified by the amplifier into a digital signal; and the CPU (central processing unit) is connected to the digital signal output end of the AD converter (analog-to-digital converter). The digital vector magnetometer with low resource consumption based on the magnetoresistive sensor provided by the utility model has the advantages of small volume, light weight, low power consumption, high precision and stability, and low resource consumption.

Description

Technical Field

[0001] The utility model relates to the technical field of magnetic field detection, in particular to a digital vector magnetometer with low resource consumption based on a magnetoresistive sensor. Background Technique

[0002] Magnetic field detection is widely used in the fields of industry, transportation, instruments, medical devices, prospecting, etc. For example, magnetic flux leakage corrosion detection is a technology that uses magnetic anomalies to perform non-destructive detection and precise positioning of the corrosion status of long-distance pipelines. Vehicle detection, magnetic guidance, iron ore pulp concentration detection, magnetic triaxial logging tool, magnetic field positioning of in-vivo capsule endoscopes, etc. The magnetic field sensors used in these magnetic field detection fields mainly include Hall sensors, inductive sensors, magnetoresistive sensors, etc. Magnetoresistive sensors are significantly superior to Hall sensors in terms of sensitivity, noise, and resource consumption. Although the noise of inductive sensors is smaller than that of magnetoresistive sensors, magnetoresistive sensors have advantages such as low cost and low resource consumption, and also have a frequency response starting from direct current, and are also suitable for the detection of static magnetic source targets.

[0003] Magnetoresistive sensors have the advantages of low power consumption, low cost, small size, high reliability, and low noise, making them ideal devices for the field of magnetic field detection. Magnetoresistive sensors can be divided into three categories: giant magnetoresistive, tunneling magnetoresistive, and anisotropic magnetoresistive sensors. The noise of giant magnetoresistive sensors and tunneling magnetoresistive sensors is usually higher than that of anisotropic magnetoresistive sensors. Anisotropic magnetoresistive sensors have two important types of noise that affect low-frequency measurements: 1 / f noise and white noise. 1 / f noise is usually suppressed by the "flip modulation" (periodically remagnetizing the sensor by applying a large bipolar magnetic field pulse), that is, the chopper amplification method. Anisotropic magnetoresistive sensors are generally made based on permalloy. Permalloy is a NiFe alloy with a certain atomic ratio (such as 80:20). Due to its relatively large anisotropic magnetoresistance ratio, excellent soft magnetic properties, and very small magnetostriction constant, it is a commonly used material for anisotropic magnetoresistive sensors.

[0004] In view of the characteristics of magnetoresistive sensors, the utility model proposes a digital vector magnetometer with low resource consumption based on a magnetoresistive sensor, which has the advantages of small volume, light weight, and low power consumption. Summary of the Utility Model

[0005] The utility model provides a digital vector magnetometer with low resource consumption based on a magnetoresistive sensor, aiming to propose a digital vector magnetometer with small volume, light weight, and low power consumption in view of the characteristics of magnetoresistive sensors.

[0006] The digital vector magnetometer with low resource consumption based on a magnetoresistive sensor provided by the present utility model includes a magnetoresistive sensor for detecting an external magnetic field and converting it into an electrical signal, and the magnetoresistive sensor uses anisotropic magnetoresistive material; an amplifier connected to the signal output end of the magnetoresistive sensor for amplifying the weak electrical signal output by the magnetoresistive sensor; an AD converter (analog-to-digital converter) connected to the signal output end of the amplifier for converting the electrical signal amplified by the amplifier into a digital signal; a CPU (central processing unit) connected to the digital signal output end of the AD converter for controlling the set / reset operation of the magnetoresistive sensor, processing the output digital signal, and outputting a final voltage signal capable of reflecting the external magnetic field vector information; a power amplifier circuit connected to the output end of one of the signals of the CPU for amplifying the set / reset signal generated by the CPU to generate a strong magnetic field; a DA converter connected to the output end of the other signal of the CPU for converting the digital signal processed by the CPU into an analog signal; and a voltage-controlled current source connected to the analog signal output end of the DA converter for adjusting the bias current of the magnetoresistive sensor according to the analog signal output by the DA converter.

[0007] Preferably, the magnetoresistive sensor uses the HMC1021Z model, and its internal includes a magnetoresistor with a Wheatstone bridge structure, a bias current band, and a set / reset current band.

[0008] Preferably, the amplifier uses the instrumentation amplifier AD620 to improve the signal-to-noise ratio and stability of the signal.

[0009] Preferably, the CPU can generate a square wave signal with a peak value of 5V, a frequency of 2KHz, and a duty cycle of 50%, which is converted into a pulse signal with a peak-to-peak value of 24V, a frequency of 2KHz, and a width of 2us through the power amplifier circuit for the set / reset operation of the magnetoresistive sensor.

[0010] Preferably, the voltage-controlled current source can automatically adjust the bias current of the magnetoresistive sensor according to the analog signal output by the DA converter to achieve closed-loop control, thereby improving the accuracy and stability of the magnetometer.

[0011] Compared with the related technology, the digital vector magnetometer with low resource consumption based on a magnetoresistive sensor provided by the present utility model has the following beneficial effects:

[0012] The present utility model provides a digital vector magnetometer with low resource consumption based on a magnetoresistive sensor:

[0013] 1. The magnetometer adopts an integrated design, reducing the overall volume and weight. At the same time, it uses a low-power consumption magnetoresistive sensor and an efficient circuit design, significantly reducing the power consumption.

[0014] 2. Through the closed-loop control technology, the dynamic zeroing of the working state of the magnetoresistive sensor is achieved, improving the accuracy and stability of magnetic field detection;

[0015] 3. By adopting low-power components and optimized circuit design, the resource consumption is significantly reduced, making it suitable for long-term continuous operation;

[0016] 4. It is applicable to multiple fields from industrial detection, traffic monitoring to medical devices. Especially in occasions with limited resources, such as remote monitoring and mobile devices, it has outstanding advantages. Brief Description of the Drawings

[0017] Figure 1 It is a schematic diagram of the Wheatstone resistance bridge structure of the magnetoresistive sensor (model: HMC1021Z);

[0018] Figure 2 It is a schematic diagram of the digital magnetoresistive magnetometer.

[0019] Reference numerals in the figure: 1. Magnetoresistive sensor; 2. Amplifier; 3. AD converter; 4. CPU; 5. Power amplifier circuit; 6. DA converter; 7. Voltage-controlled current source; 8. Set / reset signal; 11. Magnetoresistor; 12. Bias current band; 13. Set / reset current band. Detailed Embodiment

[0020] The following further describes the present utility model in conjunction with the drawings and embodiments.

[0021] A digital vector magnetometer with low resource consumption based on a magnetoresistive sensor provided by the present utility model, as Figure 2As shown in the figure, it includes a magnetoresistive sensor 1, an amplifier 2, an AD converter 3, a CPU 4, a power amplifier circuit 5, a DA converter 6, and a voltage-controlled current source 7. The magnetoresistive sensor 1 is used to detect an external magnetic field and convert it into an electrical signal. The magnetoresistive sensor 1 uses an anisotropic magnetoresistive material. The amplifier 2 is connected to the signal output end of the magnetoresistive sensor 1 and is used to amplify the weak electrical signal output by the magnetoresistive sensor 1. The AD converter 3 is connected to the signal output end of the amplifier 2 and is used to convert the electrical signal amplified by the amplifier 2 into a digital signal. The CPU 4 is connected to the digital signal output end of the AD converter 3 and is used to control the set / reset operation of the magnetoresistive sensor 1, process the digital signal output by the AD converter 3, and output a final voltage signal that can reflect the external magnetic field vector information. The power amplifier circuit 5 is connected to the output end of one of the signals of the CPU 4 and is used to amplify the set / reset signal 8 generated by the CPU 4 to generate a strong magnetic field. The DA converter 6 is connected to the output end of the other signal of the CPU 4 and is used to convert the digital signal processed by the CPU 4 into an analog signal. The voltage-controlled current source 7 is connected to the analog signal output end of the DA converter 6 and is used to adjust the bias current of the magnetoresistive sensor 1 according to the analog signal output by the DA converter 6.

[0022] Among them, the magnetoresistive sensor 1 in the present invention is described by taking the magnetoresistive sensor with the model HMC1021Z as an example, and it is also applicable to other magnetoresistive sensors. HMC1021Z has a simple Wheatstone resistance bridge structure (as Figure 1 shown), and only needs a supply voltage V b to measure the magnetic field. The magnetoresistive sensor is made of a thin nickel-iron film electroplated on a silicon wafer and arranged as a resistance strip. When there is an external magnetic field, the change in the bridge resistance will cause a corresponding change in the voltage output. In addition to the bridge circuit, there are two magnetically coupled current strips on the sensor chip - the set / reset current strip and the bias current strip. The set / reset current strip can briefly apply a strong recovery magnetic field to reset the polarity of the film magnetization, improve the sensitivity of the sensor, and setting it to the cyclic mode can also improve the linearity, reduce the influence of the vertical axis and the temperature influence. The bias current strip can be used as a feedback element in the closed-loop circuit. The closed-loop working mode can eliminate the influence caused by common-mode signals such as temperature drift and circuit parameter drift, and improve the performance of the magnetic field sensor.

[0023] In the present invention, the magnetoresistive sensor 1 includes a magnetoresistor 11 with a Wheatstone bridge structure, a bias current strip 12, and a set / reset current strip 13. Compared with any other structure composed of the same components, the Wheatstone bridge structure can obtain better sensitivity and linearity. V refProvide a reference voltage for the bridge. R1 - R4 are the four magnetoresistors of the Wheatstone bridge. The output voltage of the Wheatstone bridge is only at the millivolt level and needs to be amplified by amplifier 2 (such as instrumentation amplifier AD620). Amplifier 2 amplifies the voltage signal induced by the magnetoresistive sensor 1 through an external magnetic field and converts it into a digital signal through the AD converter 3. The CPU generates a square wave signal with a peak value of 5V, a frequency of 2KHz, and a duty cycle of 50% as the set / reset signal, which is then converted into a pulse signal with a peak - to - peak value of 24V, a frequency of 2KHz, and a width of 2us through the power amplifier circuit 5 and sent to the set / reset current band 13 of the magnetoresistive sensor 1.

[0024] The CPU 4 also controls the AD converter 3 to perform analog - to - digital conversion and operates on the AD signal collected after set / reset. The high - power pulse signal applied to the set / reset current band 13 will generate a strong magnetic field. This strong magnetic field is along the sensitive axis direction and will reverse the polarity of the magnetization of the sensitive axis. And the polarity of the bridge output signal depends on the direction of the magnetization of the sensitive axis. When the set signal comes, it will drive the set pulse to obtain the bridge output V set ; when the reset signal comes, it will drive the reset pulse to obtain the bridge output V reset , and calculate the result of subtracting the two readings V out =(V set - V reset ) / 2 as the final output.

[0025] The result of the operation is output in two paths. One path is used as the final output voltage signal, which can reflect the external magnetic field vector information; the other path of the voltage signal is converted into an analog signal through the DA converter 6 and then input to the bias current band 12 of the magnetoresistive sensor 1 through the voltage - controlled current source 7. The bias current band 12 can generate a magnetic field signal that cancels out the externally applied magnetic field, making the magnetic field applied to the magnetoresistor 1 in a "dynamic zero - clearing" state. In this way, the entire circuit works in a closed - loop mode. The closed - loop working mode can stabilize the working state and amplification factor of the circuit, improve the linearity, make the magnetoresistive sensor 1 work in the best linear region, and effectively suppress the temperature drift and zero - drift phenomena, reduce the non - linear distortion, and expand the frequency band.

[0026] Compared with the related technologies, the low - resource - consumption digital vector magnetometer based on magnetoresistive sensors provided by the present utility model has the following beneficial effects:

[0027] The present utility model provides a low - resource - consumption digital vector magnetometer based on magnetoresistive sensors, which has an integrated design, significantly reducing the volume and weight; through low - power consumption design and closed - loop control technology, it improves the accuracy and stability of magnetic field detection, and at the same time ensures the ability to work continuously for a long time. These characteristics make it suitable for occasions with limited resources, such as remote monitoring and mobile devices, and has obvious market advantages.

[0028] The above are only embodiments of the present utility model, and thus do not limit the patent scope of the present utility model. Any equivalent structural or equivalent process transformations made by using the content of the specification and drawings of the present utility model, or directly or indirectly applied in other related technical fields, are similarly included within the patent protection scope of the present utility model.

Claims

1. A low resource consumption digital vector magnetometer based on magnetoresistive sensor, characterized in that: include: A magnetoresistive sensor (1) is used to detect an external magnetic field and convert it into an electrical signal, wherein the magnetoresistive sensor (1) uses an anisotropic magnetoresistive material; An amplifier (2), connected to the signal output end of the magnetoresistive sensor (1), and used to amplify the weak electrical signal output by the magnetoresistive sensor (1); An AD converter (3), connected to the signal output end of the amplifier (2), and used for converting the electrical signal amplified by the amplifier (2) into a digital signal; A CPU (4) is connected to the digital signal output end of the AD converter (3), and is used to control the set / reset operation of the magnetoresistive sensor (1), process the digital signal output by the AD converter (3), and output a final voltage signal capable of reflecting the external magnetic field vector information; A power amplifier circuit (5) connected to an output end of one of the signals of the CPU (4) and used for amplifying a set / reset signal (8) generated by the CPU (4) to generate a strong magnetic field; A DA converter (6), connected to another signal output end of the CPU (4), and used for converting the digital signal processed by the CPU (4) into an analog signal; A voltage-controlled current source (7) is connected to the analog signal output end of the DA converter (6) and is used to adjust the bias current of the magnetoresistive sensor (1) according to the analog signal output by the DA converter (6).

2. The low resource consumption digital vector magnetometer based on magnetoresistive sensor according to claim 1, characterized in that: The magnetoresistive sensor (1) adopts the HMC1021Z model, and contains a magnetoresistive resistor (11) of a Wheatstone bridge structure, a bias current band (12) and a set / reset current band (13).

3. The low resource consumption digital vector magnetometer based on magnetoresistive sensor according to claim 1, characterized in that: The amplifier (2) uses an instrumentation amplifier AD620 to improve the signal-to-noise ratio and stability of the signal.

4. The low resource consumption digital vector magnetometer based on magnetoresistive sensor according to claim 1, characterized in that: The CPU (4) can generate a square wave signal with a peak value of 5V, a frequency of 2KHz and a duty cycle of 50%, which is converted into a pulse signal with a peak-to-peak value of 24V, a frequency of 2KHz and a width of 2us through a power amplifier circuit (5) for the set / reset operation of the magnetoresistive sensor (1).

5. The low resource consumption digital vector magnetometer based on magnetoresistive sensor according to claim 1, characterized in that: The voltage-controlled current source (7) can automatically adjust the bias current of the magnetoresistive sensor (1) according to the analog signal output by the DA converter (6), thereby realizing closed-loop control.

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