CN116482591B - Device for measuring residual magnetism of object and rapidly demagnetizing - Google Patents
Device for measuring residual magnetism of object and rapidly demagnetizing Download PDFInfo
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- 230000005389 magnetism Effects 0.000 title claims abstract description 95
- 230000005291 magnetic effect Effects 0.000 claims abstract description 102
- 230000007246 mechanism Effects 0.000 claims abstract description 52
- 238000005259 measurement Methods 0.000 claims abstract description 42
- 230000033001 locomotion Effects 0.000 claims abstract description 38
- 230000005347 demagnetization Effects 0.000 claims abstract description 27
- 239000000523 sample Substances 0.000 claims description 203
- 238000000034 method Methods 0.000 claims description 22
- 238000004804 winding Methods 0.000 claims description 9
- 230000000737 periodic effect Effects 0.000 claims description 8
- 238000005070 sampling Methods 0.000 claims description 8
- 239000011159 matrix material Substances 0.000 claims description 6
- 239000013598 vector Substances 0.000 claims description 6
- 238000004364 calculation method Methods 0.000 claims description 5
- 230000005358 geomagnetic field Effects 0.000 claims description 4
- 230000001105 regulatory effect Effects 0.000 claims description 4
- 238000010183 spectrum analysis Methods 0.000 claims description 4
- 230000008859 change Effects 0.000 claims description 3
- 230000010354 integration Effects 0.000 abstract description 4
- 230000008569 process Effects 0.000 description 16
- 230000000694 effects Effects 0.000 description 11
- 239000000463 material Substances 0.000 description 9
- 230000005540 biological transmission Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000007689 inspection Methods 0.000 description 2
- 230000005415 magnetization Effects 0.000 description 2
- 229910001260 Pt alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005294 ferromagnetic effect Effects 0.000 description 1
- JUWSSMXCCAMYGX-UHFFFAOYSA-N gold platinum Chemical compound [Pt].[Au] JUWSSMXCCAMYGX-UHFFFAOYSA-N 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910001004 magnetic alloy Inorganic materials 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
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- 230000002269 spontaneous effect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/12—Measuring magnetic properties of articles or specimens of solids or fluids
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F13/00—Apparatus or processes for magnetising or demagnetising
- H01F13/006—Methods and devices for demagnetising of magnetic bodies, e.g. workpieces, sheet material
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
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Abstract
The invention discloses a device for measuring residual magnetism and rapidly demagnetizing of an object, which comprises: the plane simple pendulum motion mechanism comprises a conical structure formed by a plurality of cycloids with the same length and adjustable, and the cycloid length of the magnetometer at the optimal measurement signal-to-noise ratio is determined before the remanence measurement is carried out for the first time; the magnetic field generating mechanism is used for generating a magnetic field required by sample demagnetization when the residual magnetism of the sample does not meet the index requirement; the magnetic field measuring mechanism comprises a Gaussian meter and a magnetometer and is used for measuring the demagnetizing magnetic field applied to the sample to be measured in real time, and simultaneously measuring the magnetic field generated by the sample remanence when the optimal signal-to-noise ratio is measured in real time before and after the demagnetizing operation starts, so that the sample remanence is calculated; and the position and posture adjusting mechanism is used for adjusting the direction of the demagnetizing coil. The invention integrates the measurement of remanence and demagnetization in the same device, has high integration level, can effectively improve the measurement accuracy of remanence, and has the advantages of convenient operation and short demagnetization time.
Description
Technical Field
The invention belongs to the technical field of precise measurement, and particularly relates to a device for measuring residual magnetism of an object and rapidly demagnetizing the object.
Background
The remanence is a macroscopic magnetic moment formed by spontaneous ordered arrangement of electronic magnetic moment inside the material in the absence of an externally applied magnetic field, and the magnitude of the remanence is related to the magnetization process of the material. Various materials have different degrees of magnetization in the processes of manufacturing, processing, transporting, storing and the like, and the requirements of different application fields on the material remanence indexes are different.
In precisionIn the measurement fields, such as measurement of gravitational constant, experimental inspection of equivalent principle, noise interference caused by the existence of residual magnetism in gravitational satellites and space gravitational wave detection, especially severe residual magnetism requirements on materials used, the residual magnetism of critical components with inspection quality lower than 20nAm is required in space gravitational wave detection 2 The residual magnetic size of the experimentally prepared material is generally much higher than this index, and in addition to reducing the content of ferromagnetic impurities in the material, demagnetizing the sample with an alternating magnetic field with amplitude decay has proven to be an effective means of reducing the residual magnetic size. The traditional demagnetizing method can not finish two steps of demagnetizing and measuring remanence in one set of device, so that the time required for demagnetizing is greatly increased. Real-time monitoring of the demagnetization effect cannot be achieved, more time is required in the process of transferring the sample from the demagnetization device to the residual magnetism measurement device due to the operations of fixing again, installing the sample and the like, and the residual magnetism can be influenced due to the fact that uncertain factors are introduced in the process of transferring the sample, so that the demagnetization effect cannot be accurately judged.
Therefore, there is a need for a device that can have both demagnetization and remanence measurement functions.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a device for measuring the residual magnetism of an object and rapidly demagnetizing, wherein the residual magnetism measurement and the demagnetization are integrated in the same device, the integration level is high, the accuracy of the residual magnetism measurement can be effectively improved, and the device has the advantages of convenience in operation and short demagnetization time.
To achieve the above object, the present invention provides an apparatus for measuring remanence and rapidly demagnetizing an object, comprising:
the sample box adopts a cube hollow structure, and the inside of the sample box is used for placing a sample to be tested;
the plane simple pendulum motion mechanism comprises a conical structure formed by a plurality of cycloids with the same length and adjustable, the cycloids are connected with the top of the sample box to form a simple pendulum structure, and the length of the cycloids is adjusted to enable a magnetometer arranged below the sample box to be in an optimal measurement signal-to-noise ratio before the residual magnetism measurement is carried out for the first time; the simple pendulum structure is used for enabling the sample box to periodically perform simple pendulum motion along the fixed plumb face, and the optimal cycloid length is determined according to a time-varying magnetic field signal generated by the residual magnetism of the sample to be detected, which is measured to perform the simple pendulum motion;
the sample box in the simple pendulum mechanism is hung at the center of the demagnetizing coil and is used for generating a magnetic field required by demagnetizing a sample to be detected when the residual magnetism of the sample to be detected does not meet the index requirement and carrying out demagnetizing operation on the sample to be detected;
the magnetic field measuring mechanism comprises a Gaussian meter and a magnetometer, wherein the Gaussian meter is used for measuring a demagnetizing magnetic field applied to a sample to be measured in real time, and the magnetometer is used for measuring xyz magnetic field components generated by residual magnetism of the sample to be measured in real time when the optimal signal-to-noise ratio is measured before and after the demagnetizing operation starts; the residual magnetism of the sample to be measured is calculated according to the xyz magnetic field components in three directions and the relative position relation between the sample to be measured and the magnetometer;
the position and posture adjusting mechanism is used for adjusting the direction of the demagnetizing coil according to the size and the direction of the residual magnetism of the sample to be detected and changing the direction of the demagnetizing field applied to the sample to be detected.
The device for measuring the residual magnetism and rapidly demagnetizing the object provided by the invention has the following effects: (1) The remanence measurement and demagnetization operation are integrated in the same set of device, so that the integration level is high, and the operation is convenient; (2) The invention can rapidly measure the residual magnetism of the sample before and after the primary demagnetizing process starts, rapidly evaluate the effect of the primary demagnetizing process, then timely adjust the demagnetizing parameters according to the demagnetizing effect, and perform the next demagnetizing process, and compared with the conventional demagnetizing means, the invention can greatly shorten the time spent for demagnetizing the sample to the required index; (3) The plane simple pendulum is adopted to enable the sample to perform periodic motion, a time domain magnetic field signal generated by residual magnetism of the sample measured by the magnetometer can be modulated to a fixed frequency band, meanwhile, the period of the simple pendulum is adjustable, a measuring frequency point with the lowest noise of the magnetometer is selected for measurement, the measuring signal-to-noise ratio of the magnetometer can be greatly enhanced, and the accuracy of residual magnetism measurement is further improved; in addition, the simple pendulum adopts cycloid instead of hard rod and the like as a transmission mechanism, so that the motion of a sample is ensured to be a fixed plane, a calculation model is simplified, the fitting precision of measured data is improved, and meanwhile, the amplitude attenuation caused by friction loss in the motion process can be greatly reduced, thereby measuring more simple pendulum periods, reducing the random error of measurement and improving the measurement precision.
In one embodiment, the planar simple pendulum motion mechanism further comprises a simple pendulum period adjusting component, wherein the simple pendulum period adjusting component comprises a cycloid length adjusting nut, a winding rod and a locking nut, the cycloid length adjusting nut and the winding rod are matched to change the length of a cycloid, and the locking nut is used for locking and releasing the winding rod.
In one embodiment, the method of operation of the device comprises the steps of:
the operation method of the device comprises the following steps:
(1) Firstly, placing a sample to be measured into a sample box for fixation, then pushing the sample box to a certain height, enabling the magnetic field generated by the residual magnetism of the sample to be measured at a magnetometer to be close to zero, recording an initial release position, and then releasing the sample box to enable the sample box to perform periodic single pendulum motion along a fixed plumb face;
(2) Acquiring a time-varying magnetic field signal generated by residual magnetism of a sample to be measured, which is measured in real time by a magnetometer, performing frequency spectrum analysis on the magnetic field signal, calculating the fundamental frequency of the signal, finding the position of a frequency point where a signal peak value is positioned according to the fundamental frequency, judging the noise condition of the frequency point where the signal is positioned, if the noise is lower due to the increase of the frequency of the signal, properly reducing the cycloid length by a simple pendulum period adjusting part, otherwise, properly increasing the cycloid length to determine the cycloid length L when the magnetometer is in the optimal measurement signal-to-noise ratio;
(3) The cycloid length is adjusted to be the length L, then magnetic field components in three directions of xyz generated by residual magnetism of a sample to be detected are measured through a magnetic field measuring mechanism, and then the residual magnetism of the sample is obtained through calculation according to the magnetic field components in three directions of xyz and the relative position relation between the sample to be detected and a magnetometer;
(4) After obtaining the residual magnetism of the sample to be tested, comparing the residual magnetism with a target value, and directly taking out the sample to be tested from the sample box if the residual magnetism meets the index requirement; if the residual magnetism does not meet the index requirement, starting a magnetic field generating mechanism to demagnetize the sample to be detected;
(5) After one demagnetization is finished, closing the magnetic field generating mechanism, then measuring the residual magnetism of the sample to be measured again, and if the residual magnetism of the sample to be measured meets the index requirement at the moment, ending the measurement and taking out the sample to be measured; and if the residual magnetism of the sample to be tested still does not meet the index requirement at the moment, adjusting the demagnetizing magnetic field parameters applied to the sample to be tested by the magnetic field generating mechanism, and continuing to demagnetize the sample to be tested until the residual magnetism of the sample to be tested reaches the index requirement.
In one embodiment, in step (4), if the residual magnetism does not meet the index requirement, starting the magnetic field generating mechanism to perform the demagnetizing operation on the sample to be tested, specifically:
if the residual magnetism does not meet the index requirement, determining the magnitude and the direction of a demagnetizing field required to be applied to the sample to be detected according to the magnitude and the direction of the measured residual magnetism;
then, according to the direction of the demagnetizing field required to be applied, the direction of the demagnetizing field applied to the sample to be detected is regulated through a position posture regulating mechanism; simultaneously, combining the properties of the sample material to be detected, determining the amplitude, frequency, decay rate parameters and demagnetization mode of a needed demagnetizing field, and then carrying out corresponding demagnetizing operation on the sample to be detected through a magnetic field generating mechanism; the demagnetizing mode comprises sine wave alternating current demagnetizing or square wave direct current demagnetizing.
In one embodiment, the remanence of the sample to be measured is determined by 3n overdetermined linear equations b=km r N is the number of sampling points of the magnetic field signal measured in one period, and the specific form of the equation is as follows:
fitting results are:
M r ＝(K T K) -1 K T B
wherein M is rx 、M ry And M rz The residual magnetism components in three directions of xyz which are residual magnetism of the sample; b (B) x 、B y And B z N 1 column vectors formed by n sampling point data of xyz three-direction magnetic field component signals generated by residual magnetism of a sample to be measured by a magnetometer; coefficient matrixEach matrix element in the array is an n 1 column vector formed by propagation coefficients at n sampling points, the propagation coefficients are completely determined by the relative position relation between a sample to be detected and the magnetometer, and the relative position relation is calculated by a simple pendulum motion equation.
In one embodiment, the device further comprises a magnetic field shielding mechanism for shielding external magnetic field interference including geomagnetic field.
In one embodiment, the device further comprises a first level arranged on the sample box and used for measuring the posture of the sample box, so that the upper surface of the sample box is parallel to the horizontal plane, and the movement plane of the sample box is always a fixed plumb face.
In one embodiment, the device further comprises a second level, wherein the demagnetizing coil, the magnetometer and the second level are all arranged on a workbench, the workbench is fixedly arranged on the position posture adjusting mechanism, and the second level is used for measuring whether the workbench is horizontal or not.
In one embodiment, the device further comprises a lifting table and a leveling nut arranged at the bottom of the lifting table, wherein the lifting table is used for keeping the relative positions of the workbench and a sample to be tested unchanged, the leveling nut is used for adjusting the workbench surface, so that the workbench surface and the sample box keep certain parallelism, and meanwhile, the demagnetizing coil, the magnetometer and the sample box are guaranteed to meet certain parallelism.
In one embodiment, the magnetometer is a fluxgate magnetometer or an atomic magnetometer.
Drawings
FIG. 1 is a schematic diagram of an apparatus for measuring remanence and rapidly demagnetizing an object according to an embodiment of the present invention;
FIG. 2 is a flow chart of a method of operation of an apparatus according to an embodiment of the present invention;
FIG. 3 is a time domain plot of magnetic fields measured by an atomic magnetometer in accordance with one embodiment of the invention;
fig. 4 is a waveform diagram of a magnetic field generated by a demagnetizing coil according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
It should be noted that, in the conventional demagnetization, after the sample is demagnetized on the demagnetizer, the sample is taken out, and then the sample is measured by a special residual magnetism measuring device such as a vibrating sample magnetometer, a superconducting quantum interferometer or a torsion balance, and the magnetic field interference is easily introduced in the measuring mode, so that the judgment of the demagnetization effect is affected.
In this regard, the present invention provides a device for measuring remanence and rapidly demagnetizing an object, as shown in fig. 1, which comprises a sample box, a planar simple pendulum motion mechanism, a magnetic field generating mechanism, a magnetic field measuring mechanism and a position posture adjusting mechanism.
The sample box S5 provided in this embodiment adopts a cube hollow structure, and the inside of the sample box S is used for placing a sample to be tested. Nuts can be specifically arranged around the sample box S5 to fix the sample.
The magnetic field measuring mechanism provided in this embodiment includes a gauss meter S10 and a magnetometer S9. Wherein a Gaussian meter S9 is provided in the measuring magnetic field generating means, and the Gaussian meter S10 is used for measuring the amplitude, waveform, etc. of the demagnetizing field applied to the sample by the magnetic field generating means when the sample demagnetizing operation is performedParameters, so as to find out the optimal parameters for demagnetizing the sample; a magnetometer S9 is arranged below the sample box S5, and the magnetometer S9 is used for measuring xyz three-direction magnetic field components B generated by sample remanence when the sample remanence measurement is carried out x 、B y And B z Thus calculating the sample remanence. Preferably, the magnetometer S9 provided in this embodiment may use a three-axis high-precision magnetometer such as a fluxgate magnetometer or an atomic magnetometer, so as to further improve the measurement accuracy of remanence.
The planar simple pendulum movement mechanism provided by the embodiment adopts a conical structure formed by a plurality of cycloids S4 with the same length and adjustable, and is used for enabling the sample box S5 to carry out periodic simple pendulum movement along a fixed plumb face, so that the cycloid length L of the magnetometer S9 when the optimal measurement signal to noise ratio is determined before the first sample remanence measurement is carried out, then the length of the cycloid S4 is adjusted to L when the remanence measurement is carried out, the measurement resolution of the magnetometer S9 on the remanence can be effectively improved, and the accuracy of the remanence measurement is further effectively improved.
Further, the planar simple pendulum motion mechanism provided in this embodiment may preferably adopt a conical structure formed by 4 cycloids S4 with the same length and adjustable, and cycloid fixing members are disposed on the 4 corners at the top of the sample box S5, and the 4 cycloid fixing members are correspondingly connected with the four cycloids S4 to form a simple pendulum structure, and the length of the 4 cycloids S4 can be changed through the cycloid fixing members. Preferably, in order to improve the efficiency of the length adjustment of the cycloid S4, the planar simple pendulum motion mechanism provided in this embodiment may further include a simple pendulum period adjustment part including a cycloid length adjustment nut S1, a winding rod S3, and a lock nut S2. Wherein, the cycloid length adjusting nut S1 and the winding rod S3 are matched for use to change the length of the cycloid S4; the lock nut S1 is used for locking and releasing the winding rod S3.
The magnetic field generating mechanism provided by the embodiment is used for generating a magnetic field required by sample demagnetization when the residual magnetism of the sample does not meet the index requirement, and carrying out demagnetization operation on the sample.
In the present embodiment, the magnetic field generating mechanism includes a function generator, a power amplifier, and a demagnetizing coil S7. Wherein the function generator is used for outputting a current signal with a specific waveform, such as sine wave or square wave current with continuously attenuated amplitude, according to the material property of the sample; the power amplifier is used for amplifying the current signal into a large current signal so that the demagnetizing coil S7 can generate a demagnetizing field which is large enough for the sample to demagnetize.
Considering that the direction of the demagnetizing field applied to the sample is also a key parameter for determining demagnetization of the sample, the apparatus provided by this embodiment further includes a position posture adjustment mechanism for adjusting the direction of the demagnetizing coil S7 according to the magnitude and direction of the residual magnetism of the sample, and changing the direction of the demagnetizing field applied to the sample. Preferably, the position and posture adjusting mechanism provided in this embodiment may use a turntable S11, where the turntable S11 has scales, and is capable of displaying the angle after rotation.
As can be seen from the above description of the structure and function of each mechanism, the operation method of the device for measuring remanence and rapidly demagnetizing an object provided by the invention specifically comprises the following steps:
step one: before the first measurement of the residual magnetism of the sample, the sample is placed into the sample box S5 for fixation, then the sample box S5 is pushed up to a certain height, the sample box S5 is far away from the magnetometer S9, the initial release position is recorded, and then the sample box S5 is released, so that the sample box S5 performs periodic single pendulum motion along the fixed plumb face.
In step one, the sample box S5 is pushed up to a certain height, so that the magnetic field generated by the sample remanence at the magnetometer S9 is approximately zero, and therefore, the time-varying magnetic field signal (i.e. the field data) generated by the sample remanence is maximum in the moving process of the sample towards the magnetometer S9 from far to near, and the magnetic field signal with the maximum amplitude can be obtained in a half period. Preferably, the initial swing angle of the sample cell S5 is not more than 10 °, the initial swing angle being determined by the swing length, so that the movement of the sample can be approximately equivalent to a simple harmonic movement, and the frequency and amplitude of the magnetic field signal can be extracted from the measured magnetic field data more accurately.
Step two: acquiring a time-varying magnetic field signal generated by the residual magnetism of the sample to be measured and measured in real time by a magnetometer S9, wherein the magnetic field signal presents a periodic characteristicThen, the magnetic field signal is subjected to spectrum analysis to calculate the fundamental frequency F of the signal s ＝2/T 0 ，T 0 And (3) carrying out a simple pendulum period of simple pendulum motion on the sample, finding out the position of a frequency point where a signal peak value is located according to the fundamental frequency, judging the noise condition of the frequency point where the signal is located, if the noise is lower due to the increase of the signal frequency, properly reducing the length of the cycloid S4 through a simple pendulum period adjusting component, otherwise properly increasing the length of the cycloid S4 to determine the length L of the cycloid when the magnetometer S9 is in the optimal measurement signal-to-noise ratio.
When the sample performs periodic single pendulum movement, the amplitude of the single pendulum movement is smaller and smaller due to air resistance and the like in the movement process of the sample, and finally the movement is stopped. Assume that the initial amplitude of the sample is θ 0 The initial time is t 0 After N periods of motion, the amplitude is theta 1 At time t 1 The period of the simple pendulum is: t (T) 0 ＝(t 1 -t 0 ) From this, the relation of the amplitude of the single pendulum motion over time can be approximated: θ t ＝θ 0 e^(-δ(t-t 0 ))，δ＝(lnθ 0 -lnθ 1 )/(NT 0 ) Wherein θ t The amplitude of the simple pendulum at any time t is shown. Assuming that the amplitude decays to θ t ＝θ 3 When the signal amplitude is obviously reduced and the measurement accuracy requirement cannot be met, the amplitude theta can be calculated 3 Time t corresponding to time 3 Then intercept t 3 The magnetic field data before the moment in time is subjected to a spectral analysis.
Step three: the cycloid length is adjusted to be the length L, and then a magnetometer S9 is utilized to measure the magnetic field component B in the xyz three directions generated by the residual magnetism of the sample to be measured x 、B y And B z The measurement is then carried out according to the xyz three-direction magnetic field component B x 、B y 、B z And calculating the relative position relation K of the sample and the magnetometer to obtain the residual magnetism of the sample.
In the third step, the remanence of the sample to be measured can pass through 3n overdetermined linear equations b=km r Obtained by least square fitting of (2), n is the acquisition of the measured magnetic field signal in one periodThe number of the sample points and the specific form of the equation are as follows:
fitting results are:
M r ＝(K T K) -1 K T B
wherein M is rx 、M ry And M rz The residual magnetism components in three directions of xyz which are residual magnetism of the sample; b (B) x 、B y And B z N 1 column vectors formed by n sampling point data of xyz three-direction magnetic field component signals generated by residual magnetism of a sample to be measured by a magnetometer; coefficient matrixEach matrix element in the array is an n 1 column vector formed by propagation coefficients at n sampling points, the propagation coefficients are completely determined by the relative position relation between a sample to be detected and the magnetometer, and the relative position relation is calculated by a simple pendulum motion equation.
Step four: after obtaining the residual magnetism of the sample, comparing the residual magnetism with a target value, if the residual magnetism meets the index requirement, indicating that the sample meets the use requirement, and directly taking out the sample from the sample box without carrying out demagnetizing operation on the sample; if the residual magnetism does not meet the index requirement, the magnetic field generating mechanism is started to demagnetize the sample so as to enable the sample to meet the index requirement.
In the fourth step, when the sample is demagnetized, the magnitude and direction of the demagnetizing field required to be applied to the sample can be determined according to the magnitude and direction of the obtained residual magnetism of the sample, and then the sine wave alternating current demagnetizing or the square wave direct current demagnetizing, the magnetic field period, the frequency and the attenuation rate are selected according to the specific properties of the material. For example, for the soft magnetic alloy material AuPt, a sine wave with a period of 20s, an initial amplitude of 35mT and a decay rate of 0.15mT/s is selected for demagnetization, so that a remarkable demagnetization effect can be obtained.
Further, when it cannot be judged whether to select direct current or alternating current for demagnetization, one waveform can be selected for demagnetization, the decay rate of the magnetic field is as small as possible, and the period is larger. After the parameters are determined, the parameters are input into a function generator to output a specific waveform, and the signal is amplified into a large current signal by a power amplifier so that the demagnetizing coil can generate a magnetic field with enough magnitude. Because the magnitude of demagnetizing magnetic field is generally above 10mT, a Gaussian meter S8 with larger magnetic field measuring range and lower precision can be adopted to monitor the magnetic field generated by the demagnetizing coil in real time so as to judge whether the actually output magnetic field accords with the expectation.
Step five: after one demagnetization is finished, closing the magnetic field generating mechanism, measuring the residual magnetism of the sample again, and if the residual magnetism of the sample meets the index requirement at the moment, finishing the measurement and taking out the sample; if the residual magnetism of the sample still does not meet the index requirement at this time, returning to the step four, adjusting the demagnetizing magnetic field parameters applied to the sample to be detected by the magnetic field generating mechanism, and continuing the next demagnetizing operation on the sample until the residual magnetism of the sample reaches the index requirement, wherein the whole process can be shown by referring to the flow chart of fig. 2.
The device for measuring the residual magnetism and rapidly demagnetizing of the object provided by the embodiment has the following effects: (1) The remanence measurement and demagnetization operation are integrated in the same set of device, so that the integration level is high, and the operation is convenient; (2) The invention can rapidly measure the residual magnetism of the sample before and after the primary demagnetizing process starts, rapidly evaluate the effect of the primary demagnetizing process, then timely adjust the demagnetizing parameters according to the demagnetizing effect, and perform the next demagnetizing process, and compared with the conventional demagnetizing means, the invention can greatly shorten the time spent for demagnetizing the sample to the required index; (3) The plane simple pendulum is adopted to enable the sample to perform periodic motion, a time domain magnetic field signal generated by residual magnetism of the sample measured by the magnetometer can be modulated to a fixed frequency band, meanwhile, the period of the simple pendulum is adjustable, a measuring frequency point with the lowest noise of the magnetometer is selected for measurement, the measuring signal-to-noise ratio of the magnetometer can be greatly enhanced, and the accuracy of residual magnetism measurement is further improved; in addition, the simple pendulum adopts cycloid instead of hard rod and the like as a transmission mechanism, so that the motion of a sample is ensured to be a fixed plane, a calculation model is simplified, the fitting precision of measured data is improved, and meanwhile, the amplitude attenuation caused by friction loss in the motion process can be greatly reduced, thereby measuring more simple pendulum periods, reducing the random error of measurement and improving the measurement precision.
In one embodiment, the device further comprises a magnetic field shielding mechanism which can be used as a magnetic field shielding cover commonly used in the field for shielding external magnetic field interference including geomagnetic field, and the mechanism is needed for shielding the influence of geomagnetic field when demagnetizing the weak magnetic material.
In one embodiment, the device provided by the invention further comprises two levels S6, wherein one level is used for measuring the posture of the sample box S5, so that the upper surface of the sample box S is parallel to the horizontal plane, and the movement plane of the sample box S is always a fixed plumb face; the other level, demagnetizing coil S7 and magnetometer S9 are all set on a work bench S10, and the other level is used for measuring whether the work bench S10 is level.
Further, the device can be provided with a lifting table S12 and a leveling nut S13 arranged at the bottom of the lifting table S12. Wherein, after the cycloid length is adjusted, the relative position of the workbench S10 and the sample can be kept unchanged by utilizing the lifting table S12; the leveling nut S13 is used for adjusting the workbench surface to keep certain parallelism with the sample box S5, and meanwhile, the leveling nut S13 is also used for ensuring that the demagnetizing coil S7, the magnetometer S9 and the sample box S5 meet certain parallelism, so that system errors caused by component shape and position deviation are reduced, and the magnetic field measurement accuracy is improved.
The invention is correspondingly described below with reference to specific examples:
for a gold-platinum alloy cube sample with the size of 5cm multiplied by 5cm, the equivalent pendulum length is 1.2m, the residual moment is measured by a measuring system with a magnetic sensor as an atomic magnetometer, the time domain curve of the magnetic field in the moving process of the measured sample is shown in the figure 3, the amplitude information of the magnetic field is extracted from the measured time domain curve, and finally the calculation is carried out to obtain the magnetic field: m is M rx ＝176nAm 2 ，M ry ＝292nAm 2 ，M rz ＝143nAm 2 . Magnetic field using the waveform shown in fig. 4After demagnetizing the field, rapidly measuring the remanence again to obtain the remanence of: m is M rx ＝59nAm 2 ，M ry ＝97nAm 2 ，M rz ＝43nAm 2 The residual magnetism of the sample in all directions is obviously reduced, which indicates that the demagnetization achieves good effect.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (10)
1. An apparatus for measuring remanence and rapidly demagnetizing an object, comprising:
the sample box adopts a cube hollow structure, and the inside of the sample box is used for placing a sample to be tested;
the plane simple pendulum motion mechanism comprises a conical structure formed by a plurality of cycloids with the same length and adjustable, the cycloids are connected with the top of the sample box to form a simple pendulum structure, and the length of the cycloids is adjusted to enable a magnetometer arranged below the sample box to be in an optimal measurement signal-to-noise ratio before the residual magnetism measurement is carried out for the first time; the simple pendulum structure is used for enabling the sample box to periodically perform simple pendulum motion along the fixed plumb face, and the optimal cycloid length is determined according to a time-varying magnetic field signal generated by the residual magnetism of the sample to be detected, which is measured to perform the simple pendulum motion;
the sample box in the simple pendulum mechanism is hung at the center of the demagnetizing coil and is used for generating a magnetic field required by demagnetizing a sample to be detected when the residual magnetism of the sample to be detected does not meet the index requirement and carrying out demagnetizing operation on the sample to be detected;
the magnetic field measuring mechanism comprises a Gaussian meter and a magnetometer, wherein the Gaussian meter is used for measuring a demagnetizing magnetic field applied to a sample to be measured in real time, and the magnetometer is used for measuring xyz magnetic field components generated by residual magnetism of the sample to be measured in real time when the optimal signal-to-noise ratio is measured before and after the demagnetizing operation starts; the residual magnetism of the sample to be measured is calculated according to the xyz magnetic field components in three directions and the relative position relation between the sample to be measured and the magnetometer;
the position and posture adjusting mechanism is used for adjusting the direction of the demagnetizing coil according to the size and the direction of the residual magnetism of the sample to be detected and changing the direction of the demagnetizing field applied to the sample to be detected.
2. The apparatus for measuring remanence and rapidly demagnetizing an object according to claim 1, wherein the planar simple pendulum motion mechanism further comprises a simple pendulum period adjusting member including a cycloid length adjusting nut, a winding rod and a locking nut, the cycloid length adjusting nut and the winding rod being engaged to change the length of the cycloid, the locking nut being used to lock and release the winding rod.
3. Device for measuring the remanence of an object and for rapid demagnetization according to claim 2, characterized in that the method of operation of the device comprises the following steps:
(1) Firstly, placing a sample to be measured into a sample box for fixation, then pushing the sample box to a certain height, enabling the magnetic field generated by the residual magnetism of the sample to be measured at a magnetometer to be close to zero, recording an initial release position, and then releasing the sample box to enable the sample box to perform periodic single pendulum motion along a fixed plumb face;
(2) Acquiring a time-varying magnetic field signal generated by residual magnetism of a sample to be measured, which is measured in real time by a magnetometer, performing frequency spectrum analysis on the magnetic field signal, calculating the fundamental frequency of the signal, finding the position of a frequency point where a signal peak value is positioned according to the fundamental frequency, judging the noise condition of the frequency point where the signal is positioned, if the noise is lower due to the increase of the frequency of the signal, properly reducing the cycloid length by a simple pendulum period adjusting part, otherwise, properly increasing the cycloid length to determine the cycloid length L when the magnetometer is in the optimal measurement signal-to-noise ratio;
(3) The cycloid length is adjusted to be the length L, then magnetic field components in three directions of xyz generated by residual magnetism of a sample to be detected are measured through a magnetic field measuring mechanism, and then the residual magnetism of the sample is obtained through calculation according to the magnetic field components in three directions of xyz and the relative position relation between the sample to be detected and a magnetometer;
(4) After obtaining the residual magnetism of the sample to be tested, comparing the residual magnetism with a target value, and directly taking out the sample to be tested from the sample box if the residual magnetism meets the index requirement; if the residual magnetism does not meet the index requirement, starting a magnetic field generating mechanism to demagnetize the sample to be detected;
(5) After one demagnetization is finished, closing the magnetic field generating mechanism, then measuring the residual magnetism of the sample to be measured again, and if the residual magnetism of the sample to be measured meets the index requirement at the moment, ending the measurement and taking out the sample to be measured; and if the residual magnetism of the sample to be tested still does not meet the index requirement at the moment, adjusting the demagnetizing magnetic field parameters applied to the sample to be tested by the magnetic field generating mechanism, and continuing to demagnetize the sample to be tested until the residual magnetism of the sample to be tested reaches the index requirement.
4. The device for measuring residual magnetism and rapidly demagnetizing objects according to claim 3, wherein in the step (4), if the residual magnetism does not meet the index requirement, the step of starting the magnetic field generating mechanism to demagnetize the sample to be measured is specifically:
if the residual magnetism does not meet the index requirement, determining the magnitude and the direction of a demagnetizing field required to be applied to the sample to be detected according to the magnitude and the direction of the measured residual magnetism;
then, according to the direction of the demagnetizing field required to be applied, the direction of the demagnetizing field applied to the sample to be detected is regulated through a position posture regulating mechanism; simultaneously, combining the properties of the sample material to be detected, determining the amplitude, frequency, decay rate parameters and demagnetization mode of a needed demagnetizing field, and then carrying out corresponding demagnetizing operation on the sample to be detected through a magnetic field generating mechanism; the demagnetizing mode comprises sine wave alternating current demagnetizing or square wave direct current demagnetizing.
5. The device for measuring residual magnetism and rapidly demagnetizing an object according to any one of claims 1 to 4, characterized in that the residual magnetism of the sample to be measured is passed throughOver 3n overdetermined linear equations b=km r N is the number of sampling points of the magnetic field signal measured in one period, and the specific form of the equation is as follows:
fitting results are:
M r ＝(K T K) -1 K T B
wherein M is rx 、M ry And M rz The residual magnetism components in three directions of xyz which are residual magnetism of the sample; b (B) x 、B y And B z N 1 column vectors formed by n sampling point data of xyz three-direction magnetic field component signals generated by residual magnetism of a sample to be measured by a magnetometer; coefficient matrixEach matrix element in the array is an n 1 column vector formed by propagation coefficients at n sampling points, the propagation coefficients are completely determined by the relative position relation between a sample to be detected and the magnetometer, and the relative position relation is calculated by a simple pendulum motion equation.
6. The apparatus for measuring residual magnetism and rapidly demagnetizing an object according to claim 1, further comprising a magnetic field shielding mechanism for shielding external magnetic field interference including geomagnetic field.
7. The device for measuring remanence and rapidly demagnetizing an object according to claim 1, further comprising a first level arranged on the sample box for measuring the posture of the sample box, so that the upper surface of the sample box is parallel to the horizontal plane, thereby ensuring that the movement plane of the sample box is always a fixed plumb face.
8. The apparatus for measuring residual magnetism and rapidly demagnetizing an object according to claim 7, further comprising a second level, wherein the demagnetizing coil, the magnetometer and the second level are all provided on a table fixedly provided on the position posture adjusting mechanism, and the second level is used for measuring whether the table is horizontal or not.
9. The device for measuring residual magnetism and rapidly demagnetizing according to claim 8, further comprising a lifting table and a leveling nut arranged at the bottom of the lifting table, wherein the lifting table is used for keeping the relative position of the workbench and the sample to be measured unchanged, and the leveling nut is used for adjusting the workbench surface to keep the workbench surface and the sample box at a certain parallelism, and meanwhile ensuring that the demagnetizing coil and the magnetometer are in a certain parallelism with the sample box.
10. The apparatus for measuring remanence and rapidly demagnetizing an object according to claim 1, wherein the magnetometer is a fluxgate magnetometer or an atomic magnetometer.
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