Current measuring device and method based on zero-flux magnetism gathering ring

Abstract

The invention relates to the technical field of current measurement, and discloses a current measurement device and method based on a zero-flux magnetism gathering ring, and a non-uniform magnetism gathering ring is arranged around a conductor of current to be measured and has a standard diameter and a small-diameter area; the NV controller is connected with the NV color center probe and the zero magnetic flux feedback coil, a microwave system of the NV controller drives the NV color center probe, and a phase-locked demodulation system of the NV controller detects the magnetic resonance state of the NV color center and detects a magnetic field change signal; the NV controller provides constant current and feedback current for the zero-flux feedback coil through the constant current source and the feedback current source respectively; the NV color center probe is arranged in a small-diameter area of the non-uniform magnetism gathering ring, and a quantum magnetic resonance system is provided based on driving of the NV controller. The zero-flux feedback coil is installed in a standard diameter area of the non-uniform magnetism gathering ring and is driven by constant current and feedback current, and the feedback current is configured according to a magnetic field change signal; the current value generated by the zero magnetic flux feedback coil is used for calculating the current to be measured of the conductor.

Description

Technical Field

[0001] This invention relates to the field of current measurement technology, and more specifically, to a current measurement device and method based on a zero-flux magnetic ring. Background Technology

[0002] NV color centers are quantum systems based on the magnetic resonance effect, enabling high precision in magnetic measurements. Using radio frequency tracking systems implemented with modern electronics, the magnetic resonance microwave frequency of NV color centers can be tracked in real time. By measuring the resonance frequency, the magnetic field can be calculated, achieving high precision in magnetic measurements. Furthermore, NV color center magnetic sensors also offer the following advantages:

[0003] The temperature drift mechanism of NV color centers is relatively clear and can be offset by dual microwave drive, eliminating the influence of temperature changes on magnetic measurement accuracy and realizing low-temperature drift magnetic measurement.

[0004] NV color centers are grown in diamond, exhibiting high stability and good resistance to factors such as chemical corrosion, temperature changes, and mechanical stress impact. They also show good aging characteristics over long-term use.

[0005] The resonant frequency of the NV color center and the magnetic field strength satisfy the following relationship: f = 2.87 GHz ± 2.8 MHz / Gs × B, where B is the magnetic field to be measured and f is the microwave resonant frequency of the NV color center. The NV color center emits red fluorescence when illuminated by green laser light at wavelengths of 532 nm or 520 nm.

[0006] Based on the above advantages, NV color core magnetic sensors can be applied to current measurement systems to realize related current sensor designs. By placing the NV sensor next to the current to be measured, measuring the magnetic field signal generated by the current, and calculating the current magnitude using the magnetic field signal, the current measurement function can be achieved. Compared with traditional resistance current sensing and induction coil solutions, NV sensors based on magnetic measurement have the following characteristics:

[0007] Employing a non-contact measurement structure, the secondary conductor is completely insulated from the primary conductor where the measured current is located. The sensor itself is unaffected by the voltage on the primary conductor, making it suitable for high-voltage applications.

[0008] It is compatible with both DC and AC measurements, has a high magnetic measurement bandwidth, and can avoid interference from secondary effects such as ferromagnetic resonance and eddy current heating that are common in iron core structures.

[0009] The high magnetic measurement accuracy of diamond NV color centers enables more precise current measurement and improves the accuracy of current measurement.

[0010] However, when the amplitude of the current to be measured is small, NV color centers are often mounted on a magnetic ring to amplify the magnetic signal generated by the current before magnetic measurement. This approach enhances the amplitude of the magnetic signal generated by the current, improving the NV color center current sensor's ability to measure small currents. However, introducing a magnetic ring introduces the following problems:

[0011] The gain of the magnetic field by the magnetic ring is nonlinear. Different current intensities have different magnetic field conversion coefficients, which will lead to systematic nonlinear errors in current measurement.

[0012] Magnetic rings exhibit hysteresis, resulting in different magnetic field responses during the current rise and fall phases. This increases the error in DC current measurements and introduces higher harmonics in AC current measurements, affecting the accuracy of current measurements.

[0013] Traditional magnetic rings use a uniform diameter structure, which typically boosts the magnetic field by 5 to 10 times. For currents with small amplitudes, this gain is slightly insufficient and can easily introduce large measurement errors. Summary of the Invention

[0014] The present invention provides a current measuring device and method based on a zero-flux magnetic ring to solve the problem of how to accurately measure the current based on the zero-flux magnetic ring.

[0015] To address the aforementioned problems, this invention provides a current measurement device based on a zero-flux magnetic ring, the device comprising: a non-uniform magnetic ring, an NV color center probe, a zero-flux feedback coil, and an NV controller;

[0016] A non-uniform magnetic ring, wherein the non-uniform magnetic ring is arranged around a conductor of the current to be measured, and the non-uniform magnetic ring is provided with a standard diameter region and a small diameter region;

[0017] An NV controller is connected to the NV color center probe and the zero flux feedback coil. The microwave system of the NV controller drives the NV color center probe, and the phase-locked demodulation system of the NV controller detects the magnetic resonance state of the NV color center and detects the magnetic field change signal. The NV controller provides constant current and feedback current to the zero flux feedback coil through a constant current source and a feedback current source, respectively.

[0018] An NV color center probe is disposed in the small-diameter region of the non-uniform magnetic ring, and the NV color center probe provides a quantum magnetic resonance system based on the drive of the NV controller;

[0019] A zero-flux feedback coil is installed in the standard diameter region of the non-uniform magnetic ring. The zero-flux feedback coil is driven by a constant current and a feedback current, which is configured according to the magnetic field change signal. The current value generated by the zero-flux feedback coil is used to calculate the current to be measured in the conductor.

[0020] Preferably, the non-uniform magnetic ring has an air gap structure, and the area with a small diameter of the non-uniform magnetic ring is the air gap tightening area;

[0021] Preferably, the non-uniform magnetic ring includes one uniform magnetic ring with an opening and two non-uniform magnetic collectors; the two non-uniform magnetic collectors are arranged close to the air gap.

[0022] Preferably, the method includes: the feedback current source outputs a control current based on the magnetic resonance state of the NV color center detected by the phase-locked demodulation system, and controls the NV color center by controlling the control current to maintain the resonance state of the NV color center.

[0023] Preferably, it further includes: when the current to be measured is 0, maintaining the resonance state of the NV color center through the constant current source.

[0024] According to another aspect of the present invention, the present invention provides a current measurement method based on a zero-flux magnetic ring, characterized in that the method includes:

[0025] A non-uniform magnetic ring is arranged around the conductor of the current to be measured, and the non-uniform magnetic ring is arranged with a standard diameter region and a small diameter region.

[0026] The NV controller is connected to the NV color center probe and the zero flux feedback coil. The NV color center probe is driven by the microwave system of the NV controller. The magnetic resonance state of the NV color center is detected by the phase-locked demodulation system of the NV controller, and the magnetic field change signal is detected. The constant current and feedback current are respectively provided to the zero flux feedback coil through the constant current source and feedback current source of the NV controller.

[0027] The NV color center probe is positioned in the region with a small diameter in the non-uniform magnetic ring, and the NV color center probe provides a quantum magnetic resonance system based on the drive of the NV controller;

[0028] The zero-flux feedback coil is installed in the standard diameter region of the non-uniform magnetic ring. The zero-flux feedback coil is driven by a constant current and a feedback current, which is configured according to the magnetic field change signal. The current to be measured in the conductor is calculated using the current value generated by the zero-flux feedback coil.

[0029] Preferably, the non-uniform magnetic ring has an air gap structure, and the area with a small diameter of the non-uniform magnetic ring is the air gap tightening area;

[0030] Preferably, the non-uniform magnetic ring includes one uniform magnetic ring with an opening and two non-uniform magnetic collectors; the two non-uniform magnetic collectors are arranged close to the air gap.

[0031] Preferably, the method includes: the feedback current source outputs a control current based on the magnetic resonance state of the NV color center detected by the phase-locked demodulation system, and controls the NV color center by controlling the control current to maintain the resonance state of the NV color center.

[0032] Preferably, it further includes: when the current to be measured is 0, maintaining the resonance state of the NV color center through the constant current source.

[0033] The present invention provides a current measurement device and method based on a zero-flux magnetic ring. This device and method uses a zero-flux feedback coil to cancel out magnetic field changes caused by the measured current, maintaining a constant magnetic field strength within the magnetic ring. This avoids the nonlinear response and hysteresis effect of the magnetic ring, thereby eliminating related errors. The present invention also enhances the local magnetic field strength at the location of the NV color center using a non-uniform magnetic ring, increasing the amplitude of magnetic field changes caused by variations in the measured current, thus improving the amplitude of the measured signal and enhancing the signal-to-noise ratio of weak current measurements. Attached Figure Description

[0034] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0035] Figure 1 This is a structural diagram of a current measuring device based on a zero-flux magnetic ring according to a preferred embodiment of the present invention;

[0036] Figure 2 This is an installation example diagram of a current measuring device based on a zero-flux magnetic ring according to a preferred embodiment of the present invention;

[0037] Figure 3 This is a flowchart of a current measurement method based on a zero-flux magnetic ring according to a preferred embodiment of the present invention. Detailed Implementation

[0038] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0039] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0040] Figure 1 This is a structural diagram of a current measuring device based on a zero-flux magnetic ring according to a preferred embodiment of the present invention.

[0041] The present invention provides a zero-flux feedback measurement and a non-uniform magnetic ring structure, and designs a controller with zero-flux feedback control function, specifically including:

[0042] The magnetic ring adopts a structure with an air gap. The diameter of the magnetic ring is tightened in the air gap area. The magnetic field amplification coefficient is increased by the special non-uniform structure of local tightening, which further enhances the current signal.

[0043] A feedback coil is installed on the magnetic ring and driven by a constant current source and a feedback current source. The constant current source is used to stabilize the microwave frequency zero point, and the feedback current source is used to cancel the magnetic field generated by the current to be measured.

[0044] The controller provides a feedback current to the feedback coil to counteract the magnetic field changes of the current under test, and confirms the resonance state by measuring the fluorescence intensity, thereby performing feedback control on the feedback current.

[0045] like Figure 1 As shown, the present invention provides a current measurement device based on a zero-flux magnetic ring, characterized in that the device includes: a non-uniform magnetic ring, an NV color center probe, a zero-flux feedback coil, and an NV controller;

[0046] Non-uniform magnetic ring: The non-uniform magnetic ring is arranged around the conductor of the current to be measured. The non-uniform magnetic ring is arranged with a standard diameter area and a small diameter area.

[0047] The NV controller is connected to the NV color center probe and the zero flux feedback coil. The microwave system of the NV controller drives the NV color center probe, and the phase-locked demodulation system of the NV controller detects the magnetic resonance state of the NV color center and detects the magnetic field change signal. The NV controller provides constant current and feedback current to the zero flux feedback coil through a constant current source and a feedback current source, respectively.

[0048] The NV color center probe is located in the small-diameter region of a non-uniform magnetic ring. The NV color center probe provides a quantum magnetic resonance system based on the drive of the NV controller.

[0049] The zero-flux feedback coil is installed in the standard diameter area of ​​a non-uniform magnetic ring. The zero-flux feedback coil is driven by a constant current and a feedback current, which is configured according to the magnetic field change signal. The current value generated by the zero-flux feedback coil is used to calculate the current to be measured in the conductor.

[0050] Preferably, the non-uniform magnetic ring has an air gap structure, and the area with a small diameter of the non-uniform magnetic ring is the air gap tightening area.

[0051] Preferably, the non-uniform magnetic ring includes one uniform magnetic ring with an opening and two non-uniform magnetic collectors; the two non-uniform magnetic collectors are arranged close to the air gap.

[0052] Preferably, it includes: a feedback current source outputting a control current based on the magnetic resonance state of the NV color center detected by the phase-locked demodulation system, and controlling the NV color center by the control current to maintain the resonance state of the NV color center.

[0053] Preferably, it further includes: when the current to be measured is 0, maintaining the resonance state of the NV color center through a constant current source.

[0054] The functions of each module in the controller of this invention are as follows:

[0055] Microwave system: Provides microwaves of a specific frequency to the NV color center probe for detecting the magnetic resonance state of the NV color center;

[0056] Phase-locked demodulation system: Demodulates the fluorescence signal emitted by the NV color center to detect the magnetic resonance state of the NV color center;

[0057] Feedback current source: The output current is adjusted according to the magnetic resonance state of the NV color center detected by the phase-locked demodulation system. Through feedback control, the magnetic resonance state of the NV color center is maintained.

[0058] Constant current source: Provides a bias magnetic field to maintain the magnetic resonance of the NV color center when the measured current is 0.

[0059] The NV probe of the present invention serves as a magnetic sensor unit, providing a quantum magnetic resonance system for magnetic field measurement.

[0060] Zero flux feedback coil: Driven by a feedback current source and a constant current source, it generates a feedback magnetic field to respond to changes in the magnetic field caused by changes in the measured current, and directly maintains the magnetic resonance state of the NV color center unchanged.

[0061] Non-uniform diameter magnetic ring structure: Locally amplifies the magnetic signal intensity generated by the zero flux feedback coil and the current under test near the NV probe, enhancing the sensitivity of the current under test detection.

[0062] In this invention, the current to be measured flows through a primary conductor, generating a magnetic field signal perpendicular to the direction of the primary conductor and satisfying the right-hand screw rule. Due to the use of a magnetic ring structure, the magnetic field lines of these signals converge within the magnetic ring and do not distribute infinitely far along the radial direction, thus generating a stronger magnetic field within the magnetic ring than in air. Furthermore, if a non-uniform magnetic ring structure is used, the location with a smaller cross-sectional diameter has a higher magnetic field line density, resulting in a stronger magnetic field at that location. A diamond containing an NV color center is placed at this location and driven by a laser system and a microwave system. A photodetector (typically built into the NV sensor probe) and a phase-locked loop demodulation system receive the fluorescence emitted by the NV color center, thereby calculating the magnetic field strength on the diamond. When the current to be measured changes, the NV sensor probe detects the change in magnetic field and adjusts the current magnitude on the feedback coil according to the change in magnetic field to cancel out the change in magnetic field, achieving ampere-turn balance. Then, the current magnitude on the coil is measured, and the current to be measured is calculated from the magnitude of the secondary current on the coil according to the ampere-turn balance principle.

[0063] This invention uses a feedback coil to cancel out the magnetic field changes caused by the measured current, so that the magnetic field strength inside the magnetic ring remains constant, avoiding the nonlinear response and hysteresis effect of the magnetic ring, thereby eliminating related errors.

[0064] The non-uniform magnetic ring enhances the local magnetic field strength at the location of the NV color center, increases the amplitude of the magnetic field change caused by the change of the measured current, thereby improving the amplitude of the measured signal and improving the signal-to-noise ratio of weak current measurement.

[0065] Figure 2 This is an implementation example of the solution. For ease of processing and installation, the non-uniform magnetic focusing ring in this example is divided into one uniform magnetic focusing ring with an opening and two non-uniform magnetic focusing devices. In this example, the magnetic focusing ring is a 10cm diameter ring made of permalloy, with a 1cm diameter circular cross-section. A 1cm long air gap is created at the probe mounting position. The NV color center diamond and the magnetic focusing devices are installed in the air gap. The non-uniform magnetic focusing device has a frustum-like structure, with a 1cm diameter circular upper surface, a 2mm diameter circular lower surface, and a height of 4mm. The two magnetic focusing devices are installed on both sides of the air gap to improve the uniformity of the magnetic field spatial distribution. The diamond, measuring 1mm × 1mm × 0.5mm, is located at the center between the lower surfaces of the two magnetic focusing devices, while the upper surfaces of the magnetic focusing devices are placed close to the air gap. Tests show that a uniform magnetic ring can amplify the magnetic field generated by an electric current by 10 times; with the addition of a magnetizer, the magnetic field can be amplified by another 2.7 times, resulting in a total amplification of 27 times, which is higher than the 7-10 times amplification effect of a traditional uniform magnetic ring. Five segmented coils, each with 300 turns, are wound around the magnetic ring. Under balanced ampere-turn conditions, the current in the coil has a 1:1500 relationship with the measured current in the primary conductor.

[0066] Figure 3 This is a flowchart of a current measurement method based on a zero-flux magnetic ring according to a preferred embodiment of the present invention.

[0067] like Figure 3 As shown, the present invention provides a current measurement method based on a zero-flux magnetic ring, characterized in that the method includes:

[0068] Step 301: Set up a non-uniform magnetic ring around the conductor of the current to be measured. The non-uniform magnetic ring is set up with a standard diameter area and a small diameter area.

[0069] Step 302: Connect the NV controller to the NV color center probe and the zero flux feedback coil. Drive the NV color center probe through the microwave system of the NV controller. Detect the magnetic resonance state of the NV color center and detect the magnetic field change signal through the phase-locked demodulation system of the NV controller. Provide constant current and feedback current to the zero flux feedback coil through the constant current source and feedback current source of the NV controller, respectively.

[0070] Step 303: The NV color center probe is placed in the region with a small diameter in the middle of the non-uniform magnetic ring. The NV color center probe provides a quantum magnetic resonance system based on the drive of the NV controller.

[0071] Step 304: Install the zero flux feedback coil in the standard diameter area of ​​the non-uniform magnetic ring. The zero flux feedback coil is driven by a constant current and a feedback current. The feedback current is configured according to the magnetic field change signal. Calculate the current to be measured in the conductor using the current value generated by the zero flux feedback coil.

[0072] Preferably, the non-uniform magnetic ring has an air gap structure, and the area with a small diameter of the non-uniform magnetic ring is the air gap tightening area.

[0073] Preferably, the non-uniform magnetic ring includes one uniform magnetic ring with an opening and two non-uniform magnetic collectors; the two non-uniform magnetic collectors are arranged close to the air gap.

[0074] Preferably, it includes: a feedback current source outputting a control current based on the magnetic resonance state of the NV color center detected by the phase-locked demodulation system, and controlling the NV color center by the control current to maintain the resonance state of the NV color center.

[0075] Preferably, it further includes: when the current to be measured is 0, maintaining the resonance state of the NV color center through a constant current source.

[0076] The preferred embodiment of the present invention provides a current measurement method based on a zero-flux magnetic ring, which corresponds to the preferred embodiment of the present invention providing a current measurement system based on a zero-flux magnetic ring. These will not be described in detail here.

[0077] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0078] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0079] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0080] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0081] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0082] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0083] The invention has been described with reference to a few embodiments. However, as will be known to those skilled in the art, and as defined in the appended claims, other embodiments besides those disclosed above fall equivalently within the scope of the invention.

[0084] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

Claims

1. A current measuring device based on a zero-flux magnetic ring, characterized in that, The device includes: a non-uniform magnetic ring, an NV color center probe, a zero flux feedback coil, and an NV controller; A non-uniform magnetic ring, wherein the non-uniform magnetic ring is arranged around a conductor of the current to be measured, and the non-uniform magnetic ring is provided with a standard diameter region and a small diameter region; An NV controller is connected to the NV color center probe and the zero flux feedback coil. The microwave system of the NV controller drives the NV color center probe, and the phase-locked demodulation system of the NV controller detects the magnetic resonance state of the NV color center and detects the magnetic field change signal. The NV controller provides constant current and feedback current to the zero flux feedback coil through a constant current source and a feedback current source, respectively. An NV color center probe is disposed in the small-diameter region of the non-uniform magnetic ring, and the NV color center probe provides a quantum magnetic resonance system based on the drive of the NV controller; A zero-flux feedback coil is installed in the standard diameter region of the non-uniform magnetic ring. The zero-flux feedback coil is driven by a constant current and a feedback current, which is configured according to the magnetic field change signal. The current value generated by the zero-flux feedback coil is used to calculate the current to be measured in the conductor.

2. The apparatus according to claim 1, characterized in that, The non-uniform magnetic ring has an air gap structure, and the area with a small diameter of the non-uniform magnetic ring is the air gap tightening area.

3. The apparatus according to claim 2, characterized in that, The non-uniform magnetic ring includes one uniform magnetic ring with an opening and two non-uniform magnetic collectors; the two non-uniform magnetic collectors are set close to the air gap.

4. The apparatus according to claim 1, characterized in that, include: The feedback current source outputs a control current based on the magnetic resonance state of the NV color center detected by the phase-locked demodulation system. The control current controls the NV color center to maintain its resonance state.

5. The apparatus according to claim 1, characterized in that, Also includes: When the current to be measured is 0, the constant current source maintains the resonance state of the NV color center.

6. A current measurement method based on a zero-flux magnetic ring, characterized in that, The method includes: A non-uniform magnetic ring is arranged around the conductor of the current to be measured, and the non-uniform magnetic ring is arranged with a standard diameter region and a small diameter region. The NV controller is connected to the NV color center probe and the zero flux feedback coil. The NV color center probe is driven by the microwave system of the NV controller. The magnetic resonance state of the NV color center is detected by the phase-locked demodulation system of the NV controller, and the magnetic field change signal is detected. The constant current and feedback current are respectively provided to the zero flux feedback coil through the constant current source and feedback current source of the NV controller. The NV color center probe is positioned in the region with a small diameter in the non-uniform magnetic ring, and the NV color center probe provides a quantum magnetic resonance system based on the drive of the NV controller; The zero-flux feedback coil is installed in the standard diameter region of the non-uniform magnetic ring. The zero-flux feedback coil is driven by a constant current and a feedback current, which is configured according to the magnetic field change signal. The current to be measured in the conductor is calculated using the current value generated by the zero-flux feedback coil.

7. The method according to claim 6, characterized in that, The non-uniform magnetic ring has an air gap structure, and the area with a small diameter of the non-uniform magnetic ring is the air gap tightening area.

8. The method according to claim 7, characterized in that, The non-uniform magnetic ring includes one uniform magnetic ring with an opening and two non-uniform magnetic collectors; the two non-uniform magnetic collectors are set close to the air gap.

9. The method according to claim 6, characterized in that, include: The feedback current source outputs a control current based on the magnetic resonance state of the NV color center detected by the phase-locked demodulation system. The control current controls the NV color center to maintain its resonance state.

10. The method according to claim 6, characterized in that, Also includes: When the current to be measured is 0, the constant current source maintains the resonance state of the NV color center.

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