Online demagnetization method

Abstract

The invention belongs to the technical field of demagnetization, and particularly relates to an online demagnetization method which comprises the following specific steps: detecting the size of a to-be-detected magnetic field applied to a magnetic core by utilizing the characteristic of induction signal mutation caused by inductance mutation when the magnetic core enters a saturated state; the external current and the space position physical information are indirectly detected; in the application, the magnetic material can periodically work in a saturated-unsaturated state, and the condition that the sensitivity of the sensor is the highest is that the magnetic field intensity H generated by an excitation signal is the saturated magnetic field intensity Hm of the magnetic material which is # imgabs 0 # times. According to the scheme, during demagnetization, the sensor can still work normally, and no detection empty window exists; a complicated demagnetization circuit or physical method is not needed, and the implementation is easy; demagnetization can be realized in several short periods, and the speed and the efficiency are high; and the device is easy to be repeatedly used in actual products, has no special requirements on the structure and function of the products, and is high in applicability.

Description

Technical Field

[0001] The invention relates to the technical field of demagnetization, in particular to an online demagnetization method. Background Art

[0002] Remanence, or residual magnetization, is the magnetization that remains when the external field is reduced to zero. The essence of remanence is the accumulation of irreversible movement of magnetic domains. Under very small magnetic fields, the initial magnetization of magnetic materials is a reversible state. In this state, the magnetic core has no residual magnetization. As the degree of magnetization increases, the accumulation of residual magnetization will increase. In the extreme case, when the magnetic induction intensity reaches Bs, the magnetic domains are magnetized and point in one direction. At this time, when the external field is reduced to zero, the residual magnetization intensity is the largest ( Figure 1 as shown).

[0003] Residual magnetism is one of the key factors affecting the accuracy of current sensors. The accumulation of residual magnetism will lead to zero bias on the one hand, and measurement deviation on the other hand. In severe cases, it may even generate impact signals that damage the back-end precision electronic circuits. Therefore, demagnetization of magnetic sensors is particularly important.

[0004] There are two main methods for demagnetizing magnetic sensors: Thermal magnetic neutral demagnetization method: During the production process of the core material, the core material is heated to above the Curie temperature (generally about 60 degrees higher than the Curie temperature), and then cooled and demagnetized without the action of an external magnetic field. When the temperature reaches the Curie temperature, the molecules inside the core move violently, and the magnetic domains return to a chaotic and disordered state. However, this method can only be used during the production of the core material to eliminate the residual magnetism caused by the production process such as internal stress, but the disadvantage is that it requires extremely high temperatures and cannot be used in the actual work of the finished sensor.

[0005] Alternating attenuation current demagnetization method: The alternating attenuation current method is to gradually reduce the residual magnetism of the magnetic core by slowly reducing the amplitude of the current signal or reducing the frequency of the current signal (or voltage signal). The signal size and the required number of cycles at the end of demagnetization are determined according to the actual residual magnetism requirements to achieve a low residual magnetism state or a zero residual magnetism state in the magnetic material.

[0006] In addition, there are other publicly available demagnetization methods as follows: CN118486524A proposes a transformer energy storage demagnetization method, which connects an energy storage capacitor to a transformer and utilizes energy oscillation to achieve core demagnetization; CN118335449A proposes a compensatory pulse demagnetization method, which uses an RLC second-order oscillation circuit to generate a pulse current in the demagnetization coil, and demagnetization is achieved with the pulse oscillation; In summary, the existing demagnetization methods mainly use physical demagnetization and demagnetization by gradually reducing energy through various different methods. These two methods have the following difficulties in practical engineering use, especially in sensor applications: 1) The physical demagnetization method requires the core to be raised to below the Curie temperature. On the one hand, it is difficult to achieve in the product. On the other hand, high-temperature demagnetization is an irreversible process. Therefore, this method is only used in the production process of the core. 2) The method of gradually reducing the energy to eliminate the residual magnetism of the magnetic core by different means has been widely used in engineering, but such methods all take a long time (even if some faster methods are adopted, 10 to 20 cycles of signal attenuation are required). Especially for sensors used in key protection positions, if this method is used for calibration, there will inevitably be sensor non-online periods, which may even bring immeasurable losses in severe cases. Summary of the invention

[0007] The object of the present invention is to provide an online demagnetization method to solve the problems raised in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: an online demagnetization method, the specific steps of the online demagnetization method are as follows: S1: Formulate a test circuit: The test circuit includes a sensor core L1 and a sampling resistor R1 connected to a power supply VCC, and a test point 1 is between the sensor core L1 and the sampling resistor R1; S2: Calculate the current in the circuit based on the voltage value at test point 1, and then calculate the magnetic field strength on the sensor core L1; Based on the voltage value of test point 1, the system gives a control signal to control the power supply VCC square wave signal to flip; S3: Periodically turn on the switch for 3 to 5 square wave cycles to eliminate external false offsets and complete online demagnetization of the magnetic material of the sensor core L1.

[0009] Preferably, the voltage amplitude is changed so that the current increases, thereby increasing the magnetic field strength and achieving demagnetization.

[0010] Preferably, an external capacitor is used to increase the current amplitude and the magnetic field strength by means of rapid discharge or pulse current to achieve demagnetization.

[0011] Preferably, the windings are transformed to directly increase the magnetic field strength and achieve demagnetization.

[0012] Compared with the prior art, the present invention has the following beneficial effects: In this solution, the sensor can still work normally during demagnetization without any detection window; it does not require complex demagnetization circuits or physical methods and is easy to implement; it can achieve demagnetization in just a few cycles with high speed and efficiency; it is easy to use repeatedly in actual products, has no special requirements for product structure and function, and has strong applicability.

[0013] The existing demagnetization method requires the magnetic core to stop working or even cannot be directly operated in the product. An online demagnetization method applied to the fluxgate sensor is provided, which greatly reduces the sensor residual magnetic deviation problem caused by the external environment and signal mutation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a graph showing the cumulative change of residual magnetization as the degree of magnetization changes; Figure 2 It is the position of each signal on the measured BH curve during actual operation; Figure 3 It is a simplified diagram of embodiment 1 of the online degaussing system; Figure 4 This is a simplified diagram of Example 2 of the online demagnetization system. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0017] See also Figure 1-4 , the present invention provides a technical solution: Whether it is thermal demagnetization or energy reduction demagnetization, the basic principle is to restore the magnetic domain inside the magnetic core to a disordered state, thereby eliminating the remanence and making the magnetic material in a low remanence or zero remanence state. As mentioned above, these methods are difficult to apply online, especially for sensors used in key protection positions. The technical solution of the present invention is described in detail below from the working principle and in combination with the embodiments.

[0018] 1)1) Working principle: The fluxgate technology uses the characteristics of the induced signal mutation caused by the inductance mutation when the magnetic core enters the saturation state to detect the size of the magnetic field to be detected applied to the magnetic core, and then indirectly detects physical information such as external current and spatial position.

[0019] In the above applications, magnetic materials will work periodically in the saturation-unsaturation state. According to the published literature, the sensor has the highest sensitivity when the magnetic field strength (H) generated by the excitation signal is times the saturation magnetic field strength (Hm) of the magnetic material.

[0020] In the actual working process, due to changes in the external environment and possible sudden changes in the detected signal, it is easy to introduce a false bias signal into the sensor, which will cause detection deviation and thus cause sensor failure. This false bias signal essentially brings external residual magnetism to the magnetic material, which is specifically reflected in the offset of the hysteresis loop on the magnetic material, and this offset cannot be eliminated when the sensor is working normally.

[0021] It has been found through experiments that when the magnetic core enters a deep alternating saturation state, the externally introduced false deviation signal can be effectively reduced or even eliminated, that is, the externally introduced residual magnetism is eliminated to achieve demagnetization.

[0022] Figure 2 is the position of each signal in the measured BH curve during actual operation, Hm is the saturation magnetic field intensity, Hm is the magnitude of the magnetic field generated by the excitation signal, and Hdeg is the magnitude of the magnetic field generated by the demagnetization signal: The formula for the magnetic field strength inside a magnetic material is as follows: H = NI / L; Where H is the magnetic field strength, N is the number of turns, I is the current, and L is the length of the magnetic path.

[0023] In a certain product, N and L are fixed and only parameter I can be changed to perform the above operation.

[0024] The following is an example to illustrate the implementation scheme: 2) Example 1 Simplified diagram of online degaussing system embodiment 1 Figure 3 As shown in the figure, VCC is the power supply, and the power supply signal is a square wave signal with the same positive and negative amplitudes; L1 is the sensor core (with multiple windings, not shown in the figure), and R1 is the sampling resistor. The current in the circuit can be calculated based on the voltage value of test point 1, and then the magnetic field strength on the core can be indirectly calculated.

[0025] Furthermore, the magnetic material of the magnetic core is a high permeability nonlinear soft magnetic material, such as 1J85, 1K107, etc.; The strength of the magnetic field of the core is controlled by the voltage at test point 1, and the reversal of the positive and negative square waves of the power supply is also controlled by the voltage at test point 1.

[0026] In normal operation, when the voltage at test point 1 is | When HmL / NR1|, the system gives a control signal to control the power supply square wave signal to flip.

[0027] Furthermore, the voltage signal at test point 1 is positive or negative. HmL / NR1, when the power square wave signal is positive, the voltage at test point 1 is greater than HmL / NR1 flips the power square wave; when the power square wave signal is negative, the voltage at test point 1 is less than - HmL / NR1 inverts the power square wave.

[0028] In normal operation, a demagnetization signal of 3 to 5 cycles is periodically inserted. The implementation method of the demagnetization signal is to change the value of the reference detection voltage signal of test point 1. The embodiment sets the voltage signal of test point 1 to |4HmL / NR1|, and Hdeg=4Hm.

[0029] Furthermore, the number of cycles of the demagnetization signal and the amplitude of the reference voltage may be changed to different values ​​according to different application requirements and actual measurement conditions, and are not limited to the parameters described in the embodiment.

[0030] 3) Example 2 The solution described in Example 2 requires a feedback system and is limited in application in certain open-loop systems or fixed-frequency systems. The following specifically describes the application example in an open-loop system or a fixed-frequency system.

[0031] Simplified diagram of online degaussing system embodiment 2 Figure 4 As shown, VCC is the power supply, and the power supply signal is a square wave signal with the same positive and negative amplitudes; L1 is the sensor core (with multiple windings, not shown in the figure), R1 is the sampling resistor, R2 is the demagnetization resistor, and the left side of the R2 resistor is a switch, which is controlled by the control system (not marked in the figure).

[0032] When the system is working normally, the switch is disconnected. At this time, the maximum magnetic field passing through the core is VN / R1L. Combined with the above description, the magnetic field strength on the core during normal operation is Hm, that is Hm =VN / R1L.

[0033] The demagnetization magnetic field strength in Example 2 is the same as that in Example 1, which is 4Hm. At this time, R2=( +2)R1 / 14.

[0034] The switch is turned on periodically, with the on time being about 3 to 5 square wave cycles, to eliminate external false offsets and complete the online demagnetization of magnetic materials.

[0035] The current can be increased by changing the voltage amplitude, thereby increasing the magnetic field strength to achieve demagnetization; The current amplitude can be increased by fast discharge of external capacitors or pulse current, thereby increasing the magnetic field strength to achieve demagnetization; The N in H=NI / L can be changed by changing the winding, thereby directly increasing the magnetic field strength to achieve demagnetization.

[0036] Based on the above solution, the following methods can also be used: The current can be increased by changing the voltage amplitude, thereby increasing the magnetic field strength to achieve demagnetization; The current amplitude can be increased by fast discharge of external capacitors or pulse current, thereby increasing the magnetic field strength to achieve demagnetization; The N in H=NI / L can be changed by changing the winding, thereby directly increasing the magnetic field strength to achieve demagnetization.

[0037] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention; therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the attached claims rather than the above description. Therefore, it is intended to include all changes within the meaning and scope of the equivalent elements of the claims in the present invention, and any figure marks in the claims should not be regarded as limiting the claims involved.

[0038] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An online demagnetization method, characterized in that: The specific steps of the online demagnetization method are as follows: S1: Formulate a test circuit: The test circuit includes a sensor core L1 and a sampling resistor R1 connected to a power supply VCC, and a test point 1 is between the sensor core L1 and the sampling resistor R1; S2: Calculate the current in the circuit based on the voltage value at test point 1, and then calculate the magnetic field strength on the sensor core L1; Based on the voltage value of test point 1, the system gives a control signal to control the power supply VCC square wave signal to flip; S3: Periodically turn on the switch for 3 to 5 square wave cycles to eliminate external false offsets and complete online demagnetization of the magnetic material of the sensor core L1.

2. An online demagnetization method according to claim 1, characterized in that: Changing the voltage amplitude increases the current, increases the magnetic field strength, and achieves demagnetization.

3. An online demagnetization method according to claim 1, characterized in that: Use external capacitors, rapid discharge or pulse current to increase the current amplitude, increase the magnetic field strength, and achieve demagnetization.

4. An online demagnetization method according to claim 1, characterized in that: Changing the windings directly increases the magnetic field strength and achieves demagnetization.

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