Single-frequency pulse magnetic measurement method

Abstract

The invention belongs to the field of magnetic measurement, and particularly discloses a single-frequency pulse magnetic measurement method, which comprises the following steps: acquiring an intrinsic demagnetization curve of a magnetic sample to be measured when a magnetizing coil is subjected to tertiary pulse discharge; the tertiary pulse comprises a saturation magnetization pulse, and a magnetic flipping pulse and a magnetic non-flipping pulse after the saturation magnetization pulse; determining a first eddy current magnetic field in the to-be-tested sample during the pulse discharge in combination with an intrinsic demagnetization curve during the magnetic non-overturning pulse discharge, and determining an eddy current conversion factor of the to-be-tested sample based on the first eddy current magnetic field; the same background magnetic field in the intrinsic demagnetization curve has the same static magnetic polarization field; and determining a second eddy current magnetic field in the to-be-tested sample during the current pulse discharge by combining the intrinsic demagnetization curve and the eddy current conversion factor during the magnetic flip pulse discharge. According to the application, stripping measurement of the intrinsic magnetization and the eddy current magnetic field of the sample can be completed only through single-frequency pulse, fewer discharge times and shorter cooling time.

Description

Technical Field

[0001] The present application belongs to the field of magnetic measurement, and more specifically, relates to a single-frequency pulse magnetic measurement method. Background Art

[0002] Permanent magnets are widely used in modern life, such as industrial production, power conversion, electronic products, data storage, etc. According to whether there is an air gap in the magnetic circuit, the measurement technology of permanent magnetic materials can be divided into closed magnetic circuit measurement technology and open magnetic circuit measurement technology. Closed magnetic circuit measurement technology uses electromagnets to magnetize samples. For ultra-high coercive force samples, it is limited by the influence of pole head saturation and cannot fully magnetize the samples, which leads to large measurement deviations. Open magnetic circuit measurement technology uses energized coils to magnetize samples. Typical technologies include vibrating sample magnetometers (VSM) and pulsed field magnetometers (PFM). The application of vibrating sample magnetometers is limited by factors such as expensive superconducting coils and the ability to measure only small-sized samples.

[0003] The pulsed magnetic field magnetometer has a simple principle, is relatively inexpensive, can achieve a higher magnetization field, is suitable for the growing demand for magnetic coercivity, and has a good development prospect. However, due to the rapid change of the magnetic field, the magnetic sample will generate eddy currents during the test, and the eddy current magnetic field will affect the test results.

[0004] In order to solve the influence of eddy current magnetic field, patent document CN1115383A proposes to use pulse magnetic fields of different frequencies to quantify the influence of eddy current magnetic field. This variable frequency pulse measurement method requires magnets with different adjustable capacitance or inductance to achieve frequency change. In addition, each pulse discharge is a complete cycle, and the number of discharges in the entire measurement process is at least 6 times, which requires longer cooling and testing time. Summary of the invention

[0005] In view of the defects of the prior art, the purpose of this application is to provide a single-frequency pulse magnetic measurement method, which aims to solve the problem that the eddy current magnetic field of the magnetic sample will affect the magnetic measurement, and there is currently no solution to quantify the eddy current magnetic field by relying solely on a single-frequency pulse.

[0006] To achieve the above-mentioned purpose, in a first aspect, the present application provides a single-frequency pulse magnetic measurement method, which is applied to a magnetic measurement device, the device comprising: a magnetizing coil, a magnetic sample to be measured is located inside the magnetizing coil, and the magnetizing coil provides a background magnetic field for the magnetic sample to be measured when discharged, the method comprising:

[0007] Obtaining an intrinsic demagnetization curve of the magnetic sample to be tested when the magnetizing coil is subjected to three pulse discharges; the three pulses include: a saturation magnetization pulse, and a magnetic reversal pulse and a magnetic non-reversal pulse after the saturation magnetization pulse; the magnetic reversal pulse and the magnetic non-reversal pulse are in no particular order; the saturation magnetization pulse is used to saturate magnetize the sample, and the magnetic reversal pulse and the magnetic non-reversal pulse are used to magnetize the sample with the same or opposite magnetic direction, and the magnetic direction is the magnetization direction of the sample during the last pulse discharge; the intrinsic demagnetization curve reflects the relationship between the background magnetic field and the dynamic magnetization pole field of the magnetic sample to be tested;

[0008] Combined with the intrinsic demagnetization curve during magnetic non-reversal pulse discharge, the first eddy current magnetic field in the sample to be tested during this pulse discharge is determined, and the eddy current conversion factor of the sample to be tested is determined based on the first eddy current magnetic field; wherein the dynamic magnetic polarization field of the sample during magnetic non-reversal pulse discharge includes: the first eddy current magnetic field and the static magnetic polarization field caused by the background magnetic field; the same background magnetic field in the intrinsic demagnetization curve has the same static magnetic polarization field;

[0009] The second eddy current magnetic field in the sample to be tested during the pulse discharge is determined by combining the intrinsic demagnetization curve during the magnetic reversal pulse discharge and the eddy current conversion factor; wherein the dynamic magnetic polarization field during the magnetic reversal pulse discharge includes: the first eddy current magnetic field, the static magnetic polarization field and the second eddy current magnetic field caused by the static magnetic polarization field.

[0010] Optionally, the three pulse discharges mentioned above are all half-cycle pulse discharges.

[0011] Among them, the above three pulse discharges are single-frequency pulse discharges, which means that the amplitude and pulse width of the pulse are the same, and only the direction changes. The present application can calculate the eddy current characteristics of the sample through a single-frequency half-cycle magnetic reversal pulse discharge and a half-cycle magnetic non-reversal pulse discharge, thereby performing eddy current deduction; the method of the present application requires a small number of discharges, a short test time, a short cooling time, and a simple measuring device. The existing traditional variable frequency measurement method requires eddy current quantification through the characteristic that the eddy current is proportional to the frequency. Each pulse discharge needs to be a complete cycle discharge, and the entire test device is complex. The number of discharges during the measurement process is at least 6 times, which requires a longer cooling and testing time.

[0012] In an optional embodiment, when the three pulses are: a saturation magnetization pulse, a magnetic reversal pulse, and a magnetic non-reversal pulse, the first eddy current magnetic field when the magnetic reversal pulse is discharged has the same value and direction as the first eddy current magnetic field when the magnetic non-reversal pulse is discharged;

[0013] When the three pulses are: saturation magnetization pulse, magnetic non-reversal pulse and magnetic reversal pulse, the first eddy current magnetic field during the discharge of the magnetic reversal pulse has the same value as the first eddy current magnetic field during the discharge of the magnetic non-reversal pulse, but has opposite directions.

[0014] In an optional embodiment, the method further includes: based on the intrinsic demagnetization curve obtained during the magnetic reversal pulse discharge, removing the corresponding eddy current magnetic field to obtain the intrinsic demagnetization curve after eddy current correction.

[0015] In an optional embodiment, determining the first eddy current magnetic field includes:

[0016] When the magnetic field is not reversed by pulse discharge, in the intrinsic demagnetization curve, the first eddy current magnetic field H in the rising field section at the same background magnetic field is assumed to be eH (t 1 ) and the first eddy current magnetic field H of the descending field section eH (t 2 ) is k;

[0017] Then, the corresponding k is solved according to the magnetic field attenuation coefficient b and the magnetic field frequency ω corresponding to the background magnetic field:

[0018]

[0019] Among them, t 1 and t 2 Indicates the corresponding pulse discharge time;

[0020] According to the dynamic magnetic polarization field J in the rising field section under the same background magnetic field c (t 1 ) and the dynamic magnetic polarization field J in the falling field section c (t 2 ) value, solve the first eddy current magnetic field of the static magnetic polarization field at the background magnetic field:

[0021] H eH (t 1 )=(J c (t 2 )-J c (t 1 ))*k / (k+1)

[0022] H eH (t 2 )=(J c (t 2 )-J c (t 1 )) / (k+1)

[0023] The corresponding eddy current conversion factor is obtained according to the corresponding relationship between the first eddy current magnetic field and the background magnetic field.

[0024] In an optional embodiment, determining the second eddy current magnetic field includes:

[0025] During magnetic reversal pulse discharge,

[0026]

[0027] Among them, H e represents the total eddy current magnetic field, K represents the eddy current conversion factor, B represents the total magnetic field around the magnetic sample to be tested, and t represents time; μ 0 represents vacuum permeability, N represents demagnetization factor, J m represents the static magnetic polarization field, H a represents the background magnetic field;

[0028] If the iterative effect of the eddy current magnetic field itself is ignored, then:

[0029]

[0030] Among them, H eH represents the first eddy current magnetic field, H eM represents the second eddy current magnetic field;

[0031] At this time, the second eddy current magnetic field H eM Approximately: J c Represents the dynamic magnetic polarization field.

[0032] In an optional embodiment, the three pulse discharges include one of the following methods:

[0033] Forward pulse discharge, forward pulse discharge, reverse pulse discharge;

[0034] Reverse pulse discharge, reverse pulse discharge, forward pulse discharge;

[0035] Forward pulse discharge, reverse pulse discharge, reverse pulse discharge;

[0036] Reverse pulse discharge, forward pulse discharge, forward pulse discharge.

[0037] In a second aspect, the present application provides a magnetic measurement device, comprising: a magnetizing coil and a magnetic measurement unit;

[0038] The magnetic sample to be tested is placed inside the magnetizing coil, which is used to provide a background magnetic field for the magnetic sample to be tested when it is discharged:

[0039] The magnetic measurement unit is used to obtain the intrinsic demagnetization curve of the magnetic sample to be tested when the magnetizing coil is discharged by three pulses; the three pulses include: a saturation magnetization pulse, and a magnetic reversal pulse and a magnetic non-reversal pulse after the saturation magnetization pulse; the magnetic reversal pulse and the magnetic non-reversal pulse are in no particular order; the saturation magnetization pulse is used to saturate magnetize the sample, and the magnetic reversal pulse and the magnetic non-reversal pulse are used to magnetize the sample with the same or opposite magnetic direction, and the magnetic direction is the magnetization direction of the sample during the last pulse discharge; the intrinsic demagnetization curve reflects the relationship between the background magnetic field and the dynamic magnetization pole field of the magnetic sample to be tested;

[0040] The magnetic measurement unit is also used to determine the first eddy current magnetic field in the sample to be tested during the pulse discharge in combination with the intrinsic demagnetization curve during the magnetic non-reversal pulse discharge, and determine the eddy current conversion factor of the sample to be tested based on the first eddy current magnetic field; wherein the dynamic magnetic polarization field of the sample during the magnetic non-reversal pulse discharge includes: the first eddy current magnetic field and the static magnetic polarization field caused by the background magnetic field; the same background magnetic field in the intrinsic demagnetization curve has the same static magnetic polarization field;

[0041] The magnetic measurement unit is also used to determine the second eddy current magnetic field in the sample to be measured during the pulse discharge in combination with the intrinsic demagnetization curve during the magnetic reversal pulse discharge and the eddy current conversion factor; wherein the dynamic magnetic polarization field during the magnetic reversal pulse discharge includes: the first eddy current magnetic field, the static magnetic polarization field and the second eddy current magnetic field caused by the static magnetic polarization field.

[0042] In an optional embodiment, the magnetic measurement unit determines the first eddy current magnetic field, including: when the magnetic non-reversal pulse discharge occurs, in the intrinsic demagnetization curve, the first eddy current magnetic field H in the rising section at the same background magnetic field is set eH (t 1 ) and the first eddy current magnetic field H of the descending field section eH (t 2 ) is k; then the corresponding k is solved according to the magnetic field attenuation coefficient b and the magnetic field frequency ω corresponding to the background magnetic field: Among them, t 1 and t 2 Indicates the corresponding pulse discharge time; according to the dynamic magnetic polarization field J of the rising field segment at the same background magnetic field c (t 1 ) and the dynamic magnetic polarization field J in the falling field section c (t 2 ) value, solve the first eddy current magnetic field of the static magnetic polarization field at the background magnetic field: H eH (t 1 )=(J c (t 2 )-Jc (t 1 ))*k / (k+1);H eH (t 2 )=(J c (t 2 )-J c (t 1 )) / (k+1); the corresponding eddy current conversion factor is obtained according to the corresponding relationship between the first eddy current magnetic field and the background magnetic field.

[0043] In an optional embodiment, the magnetic measurement unit determines the second eddy current magnetic field, including: when the magnetic reversal pulse discharges, Among them, H e represents the total eddy current magnetic field, K represents the eddy current conversion factor, B represents the total magnetic field around the magnetic sample to be tested, and t represents time; μ 0 represents vacuum permeability, N represents demagnetization factor, J m represents the static magnetic polarization field, H a represents the background magnetic field; if the iterative effect of the eddy current magnetic field itself is ignored, then: Among them, H eH represents the first eddy current magnetic field, H eM represents the second eddy current magnetic field; at this time, the second eddy current magnetic field H eM Approximately: J c Represents the dynamic magnetic polarization field.

[0044] In a third aspect, the present application provides an electronic device comprising: at least one memory for storing programs; and at least one processor for executing the programs stored in the memory. When the program stored in the memory is executed, the processor is used to execute the method described in the first aspect or any possible implementation of the first aspect.

[0045] In general, the above technical solutions conceived by the present application have at least the following beneficial effects compared with the prior art:

[0046] The present application provides a single-frequency pulse magnetic measurement method, which utilizes three single-frequency half-cycle pulse discharges to perform magnetic measurement, one single-frequency pulse discharge to saturate magnetize the sample to be measured, and then utilizes magnetic non-reversal pulse discharge and magnetic reversal pulse discharge to achieve quantification of the eddy current magnetic field during the magnetic measurement of the sample to be measured, thereby completing high-precision magnetic measurement of the magnetic sample (minus the influence of the eddy current magnetic field); in summary, the present application only requires a single-frequency pulse, fewer discharge times, and a shorter cooling time to complete the measurement of the sample's eddy current magnetic field, thereby achieving more accurate magnetic measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1is a flow chart of a single-frequency pulse magnetic measurement method provided in an embodiment of the present application;

[0048] Figure 2 Schematic diagram of a pulse magnetic measurement device provided in an embodiment of the present application;

[0049] Figure 3 The embodiment of this application provides Figure 1 Schematic diagram of pulse waveform generated by the pulse magnetic measurement device shown;

[0050] Figure 4 is the magnetic field distribution around the sample provided in the embodiment of the present application;

[0051] Figure 5 is a schematic diagram of a pulsed magnetic field used in the pulsed magnetic measurement method NPP provided in an embodiment of the present application;

[0052] Figure 6 It is a schematic diagram of magnet discharge pulse parameter fitting provided in an embodiment of the present application;

[0053] Figure 7 It is a magnetic moment correction algorithm and its effect diagram provided in the embodiment of the present application;

[0054] Figure 8 is a schematic diagram of an eddy current magnetic field provided in an embodiment of the present application;

[0055] FIG9( a ) is a diagram showing an effect of the pulse magnetic measurement method NPP provided in an embodiment of the present application;

[0056] FIG9( b ) is another effect display diagram of the pulse magnetic measurement method NPP provided in an embodiment of the present application;

[0057] In all the drawings, the same reference numerals are used to represent the same elements or structures, wherein: 101 is a power supply, 102 is a charging switch, 103 is a capacitor, 104 is an energy dissipation switch, 105 is an energy dissipation resistor, 106 is a thyristor, 107 is a reversing switch group, 108 is a magnetizing coil, 109 is a magnetic sample, 110 is a J coil, 111 is an H coil, 112 is an ADC acquisition module, and 113 is a data processing module. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0059] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0060] The purpose of this application is to provide a new type of pulse magnetic measurement method to solve the eddy current effect in the pulse magnetic measurement process, and the structure is simpler and has lower cost. In addition, this application only needs four discharges to complete the magnetic measurement, and the cooling and testing time is short.

[0061] Figure 1 is a flow chart of the single frequency pulse magnetic measurement method provided in the embodiment of the present application; Figure 1 As shown, the following steps are included:

[0062] Step S101, obtaining an intrinsic demagnetization curve of a magnetic sample to be tested when the magnetizing coil is discharged by three pulses; the three pulses include: a saturation magnetization pulse, and a magnetic reversal pulse and a magnetic non-reversal pulse after the saturation magnetization pulse; the magnetic reversal pulse and the magnetic non-reversal pulse are in no particular order; the saturation magnetization pulse is used to saturate magnetize the sample, and the magnetic reversal pulse and the magnetic non-reversal pulse are used to magnetize the sample in the same or opposite magnetic direction, and the magnetic direction is the magnetization direction of the sample during the last pulse discharge; the intrinsic demagnetization curve reflects the relationship between the background magnetic field and the dynamic magnetization pole field of the magnetic sample to be tested;

[0063] Step S102, combining the intrinsic demagnetization curve during the magnetic non-reversal pulse discharge, determining the first eddy current magnetic field in the sample to be tested during the pulse discharge, and determining the eddy current conversion factor of the sample to be tested based on the first eddy current magnetic field; wherein the dynamic magnetic polarization field of the sample during the magnetic non-reversal pulse discharge includes: the first eddy current magnetic field and the static magnetic polarization field caused by the background magnetic field; the same background magnetic field in the above intrinsic demagnetization curve has the same static magnetic polarization field;

[0064] Step S103, combining the intrinsic demagnetization curve and eddy current conversion factor during the magnetic reversal pulse discharge to determine the second eddy current magnetic field in the sample to be tested during this pulse discharge; wherein the dynamic magnetic polarization field during the magnetic reversal pulse discharge includes: a first eddy current magnetic field, a static magnetic polarization field, and a second eddy current magnetic field caused by the static magnetic polarization field.

[0065] Optionally, when the three pulses are: a saturation magnetization pulse, a magnetic reversal pulse, and a magnetic non-reversal pulse, the value and direction of the first eddy current magnetic field during the discharge of the magnetic reversal pulse are the same as those of the first eddy current magnetic field during the discharge of the magnetic non-reversal pulse.

[0066] When the three pulses are: saturation magnetization pulse, magnetic non-reversal pulse and magnetic reversal pulse, the first eddy current magnetic field during magnetic reversal pulse discharge has the same value as the first eddy current magnetic field during magnetic non-reversal pulse discharge, but has opposite directions.

[0067] Optionally, based on the intrinsic demagnetization curve obtained during magnetic reversal pulse discharge, the corresponding eddy current magnetic field is removed to obtain the intrinsic demagnetization curve after eddy current correction.

[0068] It is understandable that the present application can use the intrinsic demagnetization curve during magnetic reversal pulse discharge as half of the intrinsic demagnetization curve, first perform eddy current correction on this part, and then perform centrosymmetric processing to obtain the intrinsic demagnetization curve after eddy current correction on the other half. For example, the present application provides a single-frequency pulse magnetic measurement method. The variables involved in the method include: background magnetic field H a , demagnetizing field H d , static magnetic polarization field J m , dynamic magnetic polarization field J c , total eddy current magnetic field H e , background magnetic field H a The eddy current magnetic field H caused eH , static magnetic polarization field J m The eddy current magnetic field H caused eM , net magnetic field H m , eddy current conversion factor K, demagnetization factor N, initial magnetic polarization field J 0 , J coil calibration coefficient c, vacuum permeability μ 0 , magnetic field attenuation coefficient b, magnetic field frequency ω.

[0069] This embodiment uses this method to correct the influence of the sample eddy current magnetic field on the hysteresis loop measurement process. Figure 2 The pulse magnetic measurement device used in the embodiment of the present application is shown, comprising: a power supply 101, a charging switch 102, a capacitor 103, an energy dissipation switch 104, an energy dissipation resistor 105, a thyristor 106, a reversing switch group 107, a magnetizing coil 108, a magnetic sample 109, a J coil 110, an H coil 111, an ADC acquisition module 112, and a data processing module 113. 101-108 are used to generate a half-wave pulse magnetic field with a pulse width of 4ms, such as Figure 3 As shown, the magnetic field can be reversed by the reversing switch group 107. The magnetic sample 109 is placed inside the magnetizing coil 108 and inside the J coil 110, and the three are coaxial. The H coil 111 is a Rogowski coil, which is sleeved on one side of the magnetizing coil 108 and is used to measure the discharge current to calibrate the discharge magnetic field strength. The data of the J coil 110 and the H coil 111 are collected by the DC acquisition module 112, and the data processing module 113 performs eddy current correction and other calculation processes.

[0070] It should be noted that the J coil is a coil for measuring the magnetic polarization intensity of the sample, and the H coil is a coil for measuring the background magnetic field intensity.

[0071] according to Figure 4 , the sample is surrounded by: background magnetic field H a , demagnetizing field Hd , static magnetic polarization field J m , total eddy current magnetic field H e , net magnetic field H m With demagnetization field H d They can be expressed as:

[0072] H m =H a +H e +H d (1)

[0073]

[0074] Where N is the demagnetization factor, μ 0 is the vacuum magnetic permeability. The voltage signal output by the J coil is integrated to obtain the dynamic magnetic polarization field J of the sample under the pulse magnetic field. c :

[0075]

[0076] Among them, J 0 is the initial magnetic polarization field of the sample, and c is the calibration coefficient of the J coil. To quantify the magnitude of the eddy current magnetic field, deduct this term from equation (3) to obtain the dynamic magnetic polarization field J c Get the static magnetic polarization field J m , which is the main function of this application.

[0077] In a more specific scenario, taking three pulse discharges as reverse pulse discharge, forward pulse discharge, and forward pulse discharge as an example, the solution provided by this application is described in detail: Figure 5 This magnetic measurement method requires a total of 4 pulse discharges; 3 of the 4 pulse discharges are the three pulse discharges required for the measurement mentioned above, and 1 pulse discharge is the discharge required to measure the background magnetic field when no sample is placed. The discharge required to measure the background magnetic field can be performed in advance.

[0078] Specifically, pulse 301, pulse 303, and pulse 304 can be forward pulses, and pulse 302 can be a reverse pulse. When no sample is placed in the magnetizing coil, pulse 301 is discharged to obtain a background signal. After placing the sample, pulses 302, 303, and 304 are discharged to make the sample undergo three processes, namely, reverse saturation magnetization, magnetic reversal, and magnetic non-reversal. For the magnetic non-reversal stage, a magnetic moment correction algorithm is required to separate the static magnetic polarization field J. m With the first eddy current magnetic field H eH For the magnetic reversal stage, the eddy current derivation algorithm is needed, based on the background magnetic field H a With the first eddy current magnetic field H eHCalculate the eddy current conversion factor K, and then calculate the second eddy current magnetic field H eM , the total eddy current magnetic field H is obtained e (H e =H eH +H eM ), these two algorithms are the core of this application, and will be described in detail below:

[0079] In the magnetic non-reversal stage, J c Contains H eH With J m Two parts, H eH By H a Caused by, and satisfies the following expression:

[0080]

[0081] exist Figure 6 (a) shows the test results of this stage. The Jc-Ha curve goes from point A to point B and then to point C. The AB segment is the rising segment and the BC segment is the falling segment. a Draw dotted lines at points AB and BC that intersect at point y 1 ,y 2 , y 1 y 2 The line segment is divided into k parts and 1 parts, representing the eddy current magnetic field H in the rising stage. eH (t 1 ), eddy current magnetic field H in the field reduction stage eH (t 2 ). After the sample 109 passes through the pulse 303, it is in the forward saturation state, which can be considered to be the case under the same H a Under, with the same J m , so y 0 represents the static magnetic polarization field J m The size of y was obtained by experiment. 1 y 2 Line segment length y 2 -y 1 , when the k value is determined, the above three magnetic fields can be obtained. For the pulse discharge process of the capacitor in series with the inductor, the magnetic field generated can be expressed as:

[0082] B(t)=B 0 e -bt sin(ωt) (5)

[0083] Among them, B 0 is the initial magnetic induction intensity, b is the magnetic field attenuation coefficient, and ω is the magnetic field frequency. Let the initial eddy current magnetic field be H 0 , then the eddy current magnetic field can be expressed as:

[0084]

[0085] In order to determine the values ​​of b and ω, Figure 1 The discharge current obtained by the device under different excitation levels is parameter fitted to obtain the values ​​of b and ω, such as Figure 7 As shown; in this example, b and ω are 60 and 787 respectively. At this point, the k value can be calculated as:

[0086]

[0087] Among them, the superscript 1 represents the rising segment, and the superscript 2 represents the falling segment. 1 ,y 2 , the unknown point y can be calculated 0 , thus obtaining H eH (t 1 ), H eH (t 2 ), piece together the lifting field data to get the final H eH , as follows:

[0088] H eH (t 1 )=(J c (t 2 )-J c (t 1 ))*k / (k+1)

[0089] H eH (t 2 )=(J c (t 2 )-J c (t 1 )) / (k+1)

[0090] H eH =H eH (t 1 )+H eH (t 2 ) (8)

[0091] Among them, the dynamic magnetic polarization field in the rising field section at the same background magnetic field is J c (t 1 ), the dynamic magnetic polarization field in the falling field section is J c (t 2 ). Furthermore, the above formulas (7) and (8) can be called the "magnetic moment correction algorithm", that is, an algorithm for calculating the eddy current magnetic field using k.

[0092] Figure 6 (b) shows the data processed by the magnetic moment correction algorithm, where the magnetic moment lines refer to the lines connecting the static magnetic polarization field strength at each moment.

[0093] In the magnetic reversal stage, J c Contains H eH , H eM , J m Three parts, including H eH By H a Caused by H eM By J m Both of them act on the sample 109 to cause eddy current, share the same conductivity, and have the same eddy current conversion factor K. In formula (4), H a Obtained by H coil detection, H eH The K value can be calculated from the above magnetic moment correction algorithm. Similarly, during the magnetic reversal process, there is:

[0094]

[0095] The “≈” in the above formula simplifies the calculation process and ignores the iterative effect of the eddy current itself (when the conductivity of the magnetic sample to be measured is very large or the background magnetic field changes very quickly, the change of the eddy current magnetic field at the previous moment will bring about a corresponding change in the eddy current magnetic field at the next moment). If you need to obtain more accurate results, you can consider the iterative effect and increase the number of iterations. For the case where the eddy current effect is not significant, you only need to calculate according to formula (9).

[0096] Furthermore, in formula (9), since J c =μ 0 H e +(1-N)J m ; and J m Much larger than μ 0 H e ,therefore:

[0097] Finally get Figure 8 The eddy current magnetic field calculation results are shown in Figure 9. In order to more intuitively demonstrate the effect of the above method on the deduction of the eddy current magnetic field, the original hysteresis loop and the hysteresis loop after deducting the eddy current are plotted as shown in Figure 9(a) and Figure 9(b).

[0098] The present application proposes a pulse magnetic measurement technology, and the technical solution adopted is: the eddy current magnetic field generated by the sample is extracted by the difference between the same-direction pulse discharge and the reverse pulse discharge, so as to realize eddy current correction. Further optionally, the magnetic measurement direction provided in the present application can be referred to as the NPP method. The NPP method is a pulse sequence method, which includes the reverse process of N and P and the same-direction process of P and P. PPN or NNP are both acceptable. For the sake of convenience, one of the sequence combinations is taken, and the sequence method is collectively referred to as NPP. In the NPP method, N refers to the reverse pulse and P refers to the forward pulse. There are 4 pulse discharges in one measurement. Pulse 301, pulse 303, and pulse 304 are forward pulses, and pulse 302 is a reverse pulse. When the sample is not placed in the magnetizing coil, pulse 301 is discharged to obtain the background signal. After the sample is placed, pulses 302, 303, and 304 are discharged, respectively causing the sample to undergo three processes: reverse saturation magnetization, magnetic reversal, and magnetic non-reversal.

[0099] In the process of magnetic non-reversal, the sample has no magnetic domain reversal, and the induction signal of the J coil only contains the background magnetic field H. a The eddy current magnetic field H caused eH And with the background magnetic field H a The changing sample static magnetic polarization field J m Through the magnetic moment correction algorithm, H eH With J m , using the background magnetic field H a and the eddy current magnetic field H generated by it eH , and obtain the eddy current conversion factor K representing the conductivity of the sample.

[0100] During the magnetic reversal process, the sample magnetic domain is reversed, and the induction signal of the J coil contains the background magnetic field H a The eddy current magnetic field H caused eH , sample static magnetic polarization field J m and the eddy current magnetic field H caused by it eM , due to the background magnetic field Ha and the magnetic polarization field J m Sharing the same eddy current conversion factor K, we can get the eddy current magnetic field H eM Finally, the eddy current magnetic field H eH and eddy current magnetic field H eM The sum is the total eddy current magnetic field H e , and thus the net magnetic field H can be calculated m With the static magnetic polarization field J m , and obtain the hysteresis loop of the sample - JH curve and BH curve.

[0101] The core of this application is to correct the magnetic moment for the magnetic non-reversal signal and separate the static magnetic polarization field J m and eddy current magnetic field H eH, and the total eddy current magnetic field H derived from the magnetic reversal signal e。

[0102] In one embodiment, the co-directional pulse and the reverse pulse have the same pulse width, amplitude, and shape, and are both half-sine waves.

[0103] In one embodiment, the NPP technology refers to performing pulses 302, 303, and 304 after placing the sample, which are respectively a reverse pulse, a forward pulse, and a forward pulse, so it is called the NPP technology. According to the central symmetry principle of the hysteresis loop, a complete cycle of the hysteresis loop can be obtained by data reversal.

[0104] In one embodiment, the J coil is composed of two coaxial reversely wound coils with equal turn areas connected in series, which can cancel out the background magnetic field H. a Signal.

[0105] In order to verify the accuracy and repeatability of the test results of the magnetic measurement method proposed in this application, magnetic samples of the same size and different coercive forces were processed, and the samples were measured respectively by the method of this application (NPP technology) and the BH instrument; wherein the BH instrument is an instrument for measuring magnetic properties. The BH instrument measures the magnetic flux density B and the magnetic field intensity H, and draws a BH curve to evaluate the magnetic properties of the material. In order to verify the accuracy of this method, temperature control tests were carried out on NdFeB samples with grades of 45SH, 45H, and 45M, and the results shown in Table 1 were obtained.

[0106] Table 1

[0107]

[0108] To verify the repeatability of this method, samples with the same pulse amplitude and temperature were measured three times for grades 45SH and 33EH, and the results shown in Table 2 were obtained.

[0109] Table 2

[0110]

[0111] It can be seen from the above results that this method can basically achieve an accuracy within 1% deviation and a repeatability within 1% deviation.

[0112] It should be understood that expressions such as "including" and "may include" that may be used in the present application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In the present application, terms such as "including" and / or "having" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0113] In addition, in the present application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0114] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Among them, "fixed connection" means that the relative position relationship after connection remains unchanged. "Rotational connection" means that the two are connected to each other and can rotate relative to each other after connection. "Sliding connection" means that the two are connected to each other and can slide relative to each other after connection. The directional terms mentioned in the embodiments of the present application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only reference directions of the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present application, 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 embodiments of the present application.

[0115] In addition, in the embodiments of the present application, the mathematical concepts mentioned are symmetry, equality, parallelism, verticality, etc. These limitations are all for the current state of the art, rather than being absolutely strict definitions in a mathematical sense, and allow a small amount of deviation, approximation to symmetry, approximation to equality, approximation to parallelism, approximation to verticality, etc. are all possible. For example, A and B are parallel, which means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. A and B are perpendicular, which means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0116] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A single-frequency pulse magnetic measurement method, the method is applied to a magnetic measurement device, the device comprising: A magnetizing coil, wherein the magnetic sample to be tested is located inside the magnetizing coil, and when the magnetizing coil is discharged, a background magnetic field is provided for the magnetic sample to be tested, wherein the method comprises: Obtaining an intrinsic demagnetization curve of the magnetic sample to be tested when the magnetizing coil is subjected to three pulse discharges; the three pulses include: a saturation magnetization pulse, and a magnetic reversal pulse and a magnetic non-reversal pulse after the saturation magnetization pulse; the magnetic reversal pulse and the magnetic non-reversal pulse are in no particular order; the saturation magnetization pulse is used to saturate magnetize the sample, and the magnetic reversal pulse and the magnetic non-reversal pulse are used to magnetize the sample with the same or opposite magnetic direction, and the magnetic direction is the magnetization direction of the sample during the last pulse discharge; the intrinsic demagnetization curve reflects the relationship between the background magnetic field and the dynamic magnetization pole field of the magnetic sample to be tested; Combined with the intrinsic demagnetization curve during magnetic non-reversal pulse discharge, the first eddy current magnetic field in the sample to be tested during this pulse discharge is determined, and the eddy current conversion factor of the sample to be tested is determined based on the first eddy current magnetic field; wherein the dynamic magnetic polarization field of the sample during magnetic non-reversal pulse discharge includes: the first eddy current magnetic field and the static magnetic polarization field caused by the background magnetic field; the same background magnetic field in the intrinsic demagnetization curve has the same static magnetic polarization field; The second eddy current magnetic field in the sample to be tested during the pulse discharge is determined by combining the intrinsic demagnetization curve during the magnetic reversal pulse discharge and the eddy current conversion factor; wherein the dynamic magnetic polarization field during the magnetic reversal pulse discharge includes: the first eddy current magnetic field, the static magnetic polarization field and the second eddy current magnetic field caused by the static magnetic polarization field.

2. The method according to claim 1, characterized in that When the three pulses are: a saturation magnetization pulse, a magnetic reversal pulse, and a magnetic non-reversal pulse, the first eddy current magnetic field when the magnetic reversal pulse is discharged is the same in value and direction as the first eddy current magnetic field when the magnetic non-reversal pulse is discharged; When the three pulses are: saturation magnetization pulse, magnetic non-reversal pulse and magnetic reversal pulse, the first eddy current magnetic field during the discharge of the magnetic reversal pulse has the same value as the first eddy current magnetic field during the discharge of the magnetic non-reversal pulse, but has opposite directions.

3. The method according to claim 1, characterized in that Also includes: On the basis of the intrinsic demagnetization curve obtained during the magnetic reversal pulse discharge, the corresponding eddy current magnetic field is removed to obtain the intrinsic demagnetization curve after eddy current correction.

4. The method according to claim 1, characterized in that: Determining a first eddy current magnetic field includes: When the magnetic field is not reversed by pulse discharge, in the intrinsic demagnetization curve, the first eddy current magnetic field H in the rising field section at the same background magnetic field is assumed to be eH (t1) and the first eddy current magnetic field H of the descending field section eH The absolute value ratio of (t2) is k; Then, the corresponding k is solved according to the magnetic field attenuation coefficient b and the magnetic field frequency ω corresponding to the background magnetic field: Among them, t1 and t2 represent the corresponding pulse discharge time; According to the dynamic magnetic polarization field J in the rising field section under the same background magnetic field c (t1) and the dynamic magnetic polarization field J in the falling field section c (t2), solve the first eddy current magnetic field of the static magnetic polarization field at the background magnetic field: H eH (t1)=(J c (t2)-J c (t1))*k / (k+1) H eH (t2)=(J c (t2)-J c (t1)) / (k+1) The corresponding eddy current conversion factor is obtained according to the corresponding relationship between the first eddy current magnetic field and the background magnetic field.

5. The method according to claim 1, characterized in that Determining a second eddy current magnetic field includes: During magnetic reversal pulse discharge, Among them, H e represents the total eddy current magnetic field, K represents the eddy current conversion factor, B represents the total magnetic field around the magnetic sample to be tested, t represents time; μ0 represents the vacuum permeability, N represents the demagnetization factor, J m represents the static magnetic polarization field, H a represents the background magnetic field; If the iterative effect of the eddy current magnetic field itself is ignored, then: Among them, H eH represents the first eddy current magnetic field, H eM represents the second eddy current magnetic field; At this time, the second eddy current magnetic field H eM Approximately: J c Represents the dynamic magnetic polarization field.

6. The method according to any one of claims 1 to 5, characterized in that: The three pulse discharges include one of the following methods: Forward pulse discharge, forward pulse discharge, reverse pulse discharge; Reverse pulse discharge, reverse pulse discharge, forward pulse discharge; Forward pulse discharge, reverse pulse discharge, reverse pulse discharge; Reverse pulse discharge, forward pulse discharge, forward pulse discharge; and / or The three pulse discharges are all half-cycle pulse discharges.

7. A magnetic measuring device, characterized in that: include: Magnetizing coil and magnetic measurement unit; The magnetic sample to be tested is placed inside the magnetizing coil, which is used to provide a background magnetic field for the magnetic sample to be tested when it is discharged: The magnetic measurement unit is used to obtain the intrinsic demagnetization curve of the magnetic sample to be tested when the magnetizing coil is discharged by three pulses; the three pulses include: a saturation magnetization pulse, and a magnetic reversal pulse and a magnetic non-reversal pulse after the saturation magnetization pulse; the magnetic reversal pulse and the magnetic non-reversal pulse are in no particular order; the saturation magnetization pulse is used to saturate magnetize the sample, and the magnetic reversal pulse and the magnetic non-reversal pulse are used to magnetize the sample with the same or opposite magnetic direction, and the magnetic direction is the magnetization direction of the sample during the last pulse discharge; the intrinsic demagnetization curve reflects the relationship between the background magnetic field and the dynamic magnetization pole field of the magnetic sample to be tested; The magnetic measurement unit is also used to determine the first eddy current magnetic field in the sample to be tested during the pulse discharge in combination with the intrinsic demagnetization curve during the magnetic non-reversal pulse discharge, and determine the eddy current conversion factor of the sample to be tested based on the first eddy current magnetic field; wherein the dynamic magnetic polarization field of the sample during the magnetic non-reversal pulse discharge includes: the first eddy current magnetic field and the static magnetic polarization field caused by the background magnetic field; the same background magnetic field in the intrinsic demagnetization curve has the same static magnetic polarization field; The magnetic measurement unit is also used to determine the second eddy current magnetic field in the sample to be measured during the pulse discharge in combination with the intrinsic demagnetization curve during the magnetic reversal pulse discharge and the eddy current conversion factor; wherein the dynamic magnetic polarization field during the magnetic reversal pulse discharge includes: the first eddy current magnetic field, the static magnetic polarization field and the second eddy current magnetic field caused by the static magnetic polarization field.

8. The device according to claim 6, characterized in that The magnetic measurement unit determines the first eddy current magnetic field, including: when the magnetic field does not flip the pulse discharge, in the intrinsic demagnetization curve, the first eddy current magnetic field H in the rising field section at the same background magnetic field is set eH (t1) and the first eddy current magnetic field H of the descending field section eH The absolute value ratio of (t2) is k; then the corresponding k is solved according to the magnetic field attenuation coefficient b and the magnetic field frequency ω corresponding to the background magnetic field: Among them, t1 and t2 represent the corresponding pulse discharge time; according to the dynamic magnetic polarization field J of the rising field segment at the same background magnetic field c (t1) and the dynamic magnetic polarization field J in the falling field section c (t2) value, solve the first eddy current magnetic field of the static magnetic polarization field at the background magnetic field: H eH (t1)=(J c (t2)-J c (t1))*k / (k+1);H eH (t2)=(J c (t2)-J c (t1)) / (k+1); the corresponding eddy current conversion factor is obtained according to the corresponding relationship between the first eddy current magnetic field and the background magnetic field.

9. The device according to claim 6, characterized in that The magnetic measurement unit determines the second eddy current magnetic field, including: when the magnetic reversal pulse discharges, Among them, H e represents the total eddy current magnetic field, K represents the eddy current conversion factor, B represents the total magnetic field around the magnetic sample to be tested, t represents time; μ0 represents the vacuum permeability, N represents the demagnetization factor, J m represents the static magnetic polarization field, H a represents the background magnetic field; if the iterative effect of the eddy current magnetic field itself is ignored, then: Among them, H eH represents the first eddy current magnetic field, H eM represents the second eddy current magnetic field; at this time, the second eddy current magnetic field H eM Approximately: J c Represents the dynamic magnetic polarization field.

10. An electronic device, characterized in that: include: at least one memory for storing a computer program; At least one processor is used to execute the program stored in the memory. When the program stored in the memory is executed, the processor is used to execute the method according to any one of claims 1 to 5.

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