CN110308411A - A kind of high-precision, the quick passive method for shimming of Halbach magnet - Google Patents
A kind of high-precision, the quick passive method for shimming of Halbach magnet Download PDFInfo
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- CN110308411A CN110308411A CN201910718207.5A CN201910718207A CN110308411A CN 110308411 A CN110308411 A CN 110308411A CN 201910718207 A CN201910718207 A CN 201910718207A CN 110308411 A CN110308411 A CN 110308411A
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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
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
- G01R33/387—Compensation of inhomogeneities
- G01R33/3873—Compensation of inhomogeneities using ferromagnetic bodies ; Passive shimming
Abstract
The present invention relates to one kind about high-precision, the quick passive method for shimming of Halbach magnet.The method is based on a kind of Halbach magnet system, and the system is multilayer cyclic structure, is made of the several layers magnet ring being layered on top of each other along axial direction；Wherein, the magnet ring is the cyclic structure that multiple small magnets surround, and each small magnet can be carried out moving radially.The method moves radially shift length based on what minimum value automatic optimal algorithm obtained each magnet, and main field is directly adjusted to optimal magnetic field strength and uniformity of magnetic field by moving radially small magnet.The magnetic field strength and the uniformity of Halbach magnet and the position of magnet, mismachining tolerance are closely related, using radial displacement as variable, using magnetic field strength and the uniformity as objective function, carry out optimization, obtain optimal magnet displacement position, there is the passive shimming permeability magnetic material of auxiliary of Engineering Error without iron plate etc., have the characteristics that precision is high, quick, simple and economical.
Description
Technical field
The invention belongs to nuclear magnetic resonance fields, and in particular to a kind of high-precision, the quick passive shimming side of Halbach magnet
Method.
Background technique
Nuclear magnetic resonance (NuclearMagneticResonance, abbreviation NMR) phenomenon by Stanford university Bloch and
Purcell of Harvard university et al. respectively independently has found with nineteen forty-six, is applied quickly later in physics, chemistry, material supply section
The fields such as, life science and medicine.For universal, Nuclear Magnetic Resonance Measurement is mainly realized by following some steps.Pass through
Magnet generates magnetostatic field B0, it is used for so that spin Hydrogen Proton magnetization vector is along magnetostatic field B0Arrangement.In order to establish thermal balance, from
Rotation Hydrogen Proton must adequately be polarized in magnetostatic field, and the magnetic polarization time is relaxation time T1.Spin Hydrogen Proton is obtaining
Sufficiently after polarization, by radio-frequency coil transmitting and magnetostatic field B0Vertical electromagnetic field B1Carry out switching.Initial radio frequency pulse is known as 90 °
Pulse.After the 90 pulse, spin proton start along magnetostatic field carry out precession, due to magnetostatic field heterogeneity and can not
Inverse proton precession, spin proton starts dephasing, to generate inductive signal.However, dephasing process is that part is reversible, pass through
Apply 180 ° of radio-frequency pulses, instantaneous phase can be inverted, to start rephasing.The reunion of proton phase can generate inductive signal, into
And continue that dephasing occurs, repetition constantly knows that signal completely disappears.
Halbach magnet is otherwise known as magic ring magnet structure, is composed of multiple small magnets, can in the inside of magnet chamber
To generate high-intensitive uniform magnetic field.Under three-dimensional cartesian coordinate system, the magnetic direction which generates is along x-axis or y-axis.
Compared to traditional cryogenic magnet, Halbach magnet does not need Cryo Equipment, small in size, at low cost and easy to carry.
However, Halbach magnet is often not achieved required for magnetic resonance detection since the error of magnet in process influences
The requirement of uniformity of magnetic field, the especially resolution ratio to the measurement of porous media short relaxation component, nuclear magnetic resonance spectral resolution and core
Magnetic resonance imaging image quality suffers from very big influence.Therefore, improve Halbach magnet uniformity of magnetic field with, to promotion
Halbach plays the role of great in the application of multiple fields.
Existing body even field scheme includes passive shimming and active shimming.The mode of passive shimming is based on magnetic field of the goal
The humorous decomposition of ball, the component of each harmonic components is calculated, by applying additional permeability magnetic material in Halbach magnet inside cavity
And the position of permeability magnetic material is determined to eliminate each harmonic components component, retain main field component to obtain the higher uniformity；
Active method for shimming is then to design the shimming DC coil for eliminating each harmonic components component for target field to reach raising
The purpose of uniformity of magnetic field, while the auxiliary of additional power-supply device being needed just to be able to achieve.However, the mistake of the processing of permeability magnetic material
The inhomogeneities of difference and magnetic permeability can bring the uncertainty of shimming result；And directly adopt active shimming mode, increase at
On the basis of this, if the non-uniformity in magnetic field is higher, active shimming still reaches to the requirement less than high evenness, while causing resource
Waste.Therefore, opposite position of the small magnet in entire magnet system directly is adjusted by calculating the shift position of small magnet
It sets, is a kind of economic, practical and effective mode to obtain higher uniformity of magnetic field.
A kind of high-precision proposed by the present invention, the quick passive method for shimming of Halbach magnet, not only can be nuclear magnetic resonance
Relaxation, diffusion, imaging, chemistry Pu Deng quantum measurement category provide the magnetic field environment of high standard, and this method can be also manufacture particle
The magnet system in the fields such as accelerator, specific type of electric machine provides new approaches.
Summary of the invention
It is an object of the invention to propose a kind of high-precision, the passive method for shimming of quick Halbach, including passive shimming
The calculation method of process and corresponding shimming magnet displacement.Specifically adopt the following technical scheme that:
A kind of Halbach magnet system, the Halbach magnet system are multilayer cyclic structure, by along axial mutual
The several layers magnet ring of stacking is constituted；Wherein,
The magnet ring is the cyclic structure that multiple small magnets surround, and each small magnet can be carried out moving radially.
Further, there is certain gap between the adjacent small magnet to facilitate and carry out radiai adjustment to small magnet.
Further, the Halbach magnet system is made of 6 layers of magnet ring, and each layer of magnet ring is all small by 16 cylinders
Magnet composition；The diameter of each magnet ring is 70mm；The diameter of each small magnet is 12mm, is highly 30mm.
Further, a kind of high-precision, quick Halbach magnet based on above-mentioned Halbach magnet system are passively even
Field method, which comprises
Small magnet is carried out numeral mark by S1, and records the Surface field intensity of each small magnet, total X small magnet；
S2 measures the magnetic field strength on the search coverage surface of magnet system under original state, and measurement point number is N, measurement point
It is evenly distributed on search coverage surface；
The target field magnetic field that the Surface field intensity of small magnet and measurement obtain is updated to and minimizes automatic optimal calculation by S3
In method, the mobile distance l of each small magnet is calculatedm；
S4 is by corresponding moving distance lmIt is corresponded with small magnet numeral mark, and corresponding small magnet is radially moved into
Corresponding position；
S5 judges whether to meet engineering precision, if not up to requiring, repeats step S1-S4, re-measures magnetic field, continue into
Row shimming；If reaching requirement, terminate.
Further, each small magnet corresponds to magnetic field strength caused by spherical surface position in search coverage are as follows:
Wherein, μ0For space permeability；I is the magnetizing current of magnet；Coordinate (x ', y ', z ') is small under rectangular coordinate system
The position of magnet, (x, y, z) are the position of search coverage umbilical point；MzFor the residual magnetization obtained measured by each small magnet, S
For the cross-sectional area of magnet magnetizing direction.
Further, spheric harmonic function decomposition is carried out to the magnetic field strength on search coverage surface, obtains the ball under spherical coordinate system
Hamonic function expansion:
Wherein, BzIt is that measurement obtains the magnetic field distribution on search coverage surface；For the coordinate of measurement point,
In, r is spherical radius, and θ is the elevation angle,For azimuth；M indicates the n-th ball harmonic component of spheric harmonics expansion, and n represents m
Rank ball harmonic component；It is n times m rank associated Legendre polynomial,WithIt is n times m rank ball harmonic component intensity respectively.
Further, total search coverage Surface field intensity distribution are as follows:
Magnetic field B0 after being superimposed by the humorous decomposition of ballzBall harmonic component wi, establish objective function:
Minimum value optimizing is carried out, optimal R ' value is obtained；Further according to lM=R '-R obtains the moving displacement of small magnet
Distance；Wherein,
When optimization, R ' is optimized variable, R 'min≤R′≤R′max；R is the initial position radius of small magnet；R ' is small magnet
Position radius after movement.
Further, the step S5 specifically:
Whether measurement uniformity of magnetic field reaches requirement, if Magnetic field inhomogeneity, repeats step S1-S4, re-measures magnetic field, after
It is continuous to carry out shimming；If field homogeneity terminates.
Alternatively, the step S5 specifically:
Judge moving distance lMAbsolute value whether reach requirement, if not up to require, repeat step S1-S4, survey again
Magnetic field is measured, shimming is continued；If reaching requirement, terminate.
Further, if the moving distance lMAbsolute value be less than 0.05mm and reach requirement.
Through the above technical solutions, technical solution of the present invention has the following advantages that and technical effect.
A kind of high-precision of the present invention, the quick passive method for shimming of Halbach magnet, are based on minimum value automatic optimal algorithm
Obtain each magnet moves radially shift length, and main field is directly adjusted to optimal magnetic field by moving radially small magnet
Intensity and uniformity of magnetic field.The magnetic field strength and the uniformity of Halbach magnet and the position of magnet, mismachining tolerance are closely related,
Optimization is carried out, optimal magnetic is obtained using magnetic field strength and the uniformity as objective function using radial displacement as variable
Position pan position has the passive shimming permeability magnetic material of auxiliary of Engineering Error without iron plate etc., high with precision, quick,
Simple and economical feature.
This method can be improved the uniformity of magnetic field of magnet, further improve nuclear magnetic resonance in the short relaxation group of porous media
Divide the resolution ratio of measurement, the resolution ratio of NMR spectrum and the image resolution ratio of Magnetic resonance imaging.
Above description is only the general introduction of technical scheme, in order to better understand the technological means of the application,
So as to be implemented in accordance with the contents of the specification, and in order to allow the above and other objects, features and advantages energy of the application
It is enough clearer and more comprehensible, with the preferred embodiment of the application and cooperates attached drawing below detailed description is as follows.
According to the accompanying drawings to the detailed description of the application specific embodiment, those skilled in the art will be brighter
The above-mentioned and other purposes of the application, advantages and features.
Detailed description of the invention
In order to illustrate the technical solutions in the embodiments of the present application or in the prior art more clearly, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, the accompanying drawings in the following description is the application
Some embodiments for those of ordinary skill in the art without creative efforts, can also basis
These attached drawings obtain other attached drawings.
Fig. 1 provides the perspective view of Halbach magnet structure by the embodiment of the present invention；
Fig. 2 provides the sectional view of Halbach magnet structure by the embodiment of the present invention；
Fig. 3 provides the magnet marking convention of Halbach magnet structure by the embodiment of the present invention.
Fig. 4 is passive shimming flow chart provided by the embodiment of the present invention；
Fig. 5 is the mobile distance results figure of magnet provided by the embodiment of the present invention；
Fig. 6 is the comparison diagram of harmonic component intensity after small magnet provided by the embodiment of the present invention is mobile；
Fig. 7 is the comparison of spherical surface magnetic field strength before and after mobile small magnet provided by the embodiment of the present invention；
Specific embodiment
To keep the purposes, technical schemes and advantages of the embodiment of the present application clearer, below in conjunction with the embodiment of the present application
In attached drawing, the technical scheme in the embodiment of the application is clearly and completely described, it is clear that described embodiment is
Some embodiments of the present application, instead of all the embodiments.In the following description, such as specific material configuration is provided only
Only to assist in comprehensive understanding embodiments herein.It therefore, it will be apparent to those skilled in the art that can be to described herein
Embodiment make various changes and modifications without departing from the scope and spirit of the present application.In addition, in order to remove and succinctly, implement
The description to known function and construction is omitted in example.
The terms "at least one", only a kind of incidence relation for describing affiliated partner, indicates may exist three
Kind relationship, for example, at least one of A and B, can indicate: individualism A exists simultaneously A and B, these three feelings of individualism B
Condition.It should also be noted that, herein, relational terms such as first and second and the like be used merely to an entity or
Person's operation is distinguished with another entity or operation, is appointed without necessarily requiring or implying existing between these entities or operation
What this actual relationship or sequence.Moreover, the terms "include", "comprise" or its any other variant are intended to non-row
His property includes.
Embodiment 1
A kind of Halbach magnet system, the Halbach magnet system be it is cylindric, by what is be layered on top of each other along axial direction
Several layers magnet ring is constituted.
Wherein
The magnet ring is the cyclic structure that multiple small magnets surround, and each small magnet can be carried out moving radially,
That is, each small magnet can be radially moved forward and backward.
It is worth noting that, the initial radial position of the small magnet is greater than the radius of search coverage ball-type volume,
That is influence of each small magnet for magnetic field is unidirectional.
As shown in Figure 1, the Halbach magnet system is cylinder, which is made of 6 layers of magnet ring, each layer
Magnet ring is all made of 16 cylindrical small magnets, and main field direction is along z-axis.For the magnet system, each small magnet
It can all be moved radially.The diameter of each magnet ring is 70mm, and the diameter of each small magnet is 12mm, is highly
30mm, central magnetic field intensity are 0.19T, have certain gap between small magnet to facilitate and carry out radial adjusting to small magnet.
In the present embodiment, search coverage is the sphere that diameter is 10mm.Target spherical area is scanned by gaussmeter, it can be with
Obtain the Distribution of Magnetic Field on spherical surface.
Embodiment 2
On the basis of embodiment 1, it is further mentioned based on one of embodiment 1 Halbach magnet system, the present embodiment
A kind of high-precision, the quick passive method for shimming of Halbach magnet out, as shown in figure 4, specifically:
Small magnet is carried out numeral mark, and measures and record the Surface field intensity of each small magnet, total X by step 1
A small magnet.
As shown in figure 3, first to each small magnet according to clockwise direction, from the top layer magnet ring of Halbach magnet system
It is successively marked to bottom magnet ring.Each small magnet can be considered as an independent magnetic dipole, and magnetization is strong
Spend the magnetic field strength that M is small magnet surface.
Each small magnet, which corresponds to magnetic field strength caused by spherical surface position in search coverage, can cut down your law with than Sa difficult to understand
It indicates:
Wherein, μ0For space permeability, unit is 4 π × 10-7T·m/A；I is the magnetizing current of magnet；Coordinate (x ', y ',
Z ') be small magnet under rectangular coordinate system position, (x, y, z) is the position of search coverage umbilical point, and rectangular coordinate system and ball are sat
Mark system can convert mutually；MzFor the residual magnetization obtained measured by each small magnet, S is the cross section of magnet magnetizing direction
Product.
Step 2, under magnet system original state, measure the umbilical point magnetic field strength of ball-type search coverage, measurement point
Number is N, and measurement point is evenly distributed on the spherical surface of search coverage.
The magnetic field being distributed on any one spherical surface, is decomposed, the available magnetic field is under spherical coordinate system by spheric harmonic function
Spheric harmonics expansion:
Wherein, BzIt is that measurement obtains spherical surface magnetic field distribution；For the coordinate of measurement point, wherein r is spherical surface
Radius, θ are the elevation angle,For azimuth；M indicates the n-th ball harmonic component of spheric harmonics expansion, and n represents humorous point of m rank ball
Amount；It is n times m rank associated Legendre polynomial,WithIt is n times m rank ball harmonic component intensity respectively.
The spherical surface Distribution of Magnetic Field obtained using measurement, by arithmetic of linearity regression, available any n times m rank
Ball harmonic component.
The umbilical point magnetic field strength that the Surface field intensity of small magnet and measurement obtain is updated to minimum certainly by step 3
In dynamic optimizing algorithm, the mobile distance l of each small magnet is calculatedM。
Total spherical surface magnetic field distribution is equal to the total magnetic field and measurement magnetic field originally that small magnet is generated in new position
Superposition, can be written as:
Magnetic field B0 after being superimposed again by the humorous decomposition of ballzBall harmonic component wi, establish objective function:
Minimum value optimizing is carried out, when optimization, R ' is optimized variable.
Wherein, R 'min≤R′≤R′max, R 'minWith R 'maxBe variable R determining in advance ' bound constraint condition.
Minimum value optimizing terminates, and obtains optimal R ' value.
Then, according to lM=R '-R obtains the moving displacement distance of small magnet.Wherein, R is the initial position half of small magnet
Diameter (that is, when small magnet is located at initial position, radius) under spherical coordinate system；R ' be after small magnet is mobile position radius (that is,
After small magnet is mobile, the radius under spherical coordinate system).
Minimum value optimizing algorithm in this step can directly be quoted in MATLAB kit to be used, and programmed environment is just
It is prompt, easy to use.
Step 4, by corresponding moving displacement distance lMIt is corresponded with small magnet numeral mark, and each small magnet is radial
It is moved to corresponding position；
Whether step 5, measurement uniformity of magnetic field reach requirement, if not up to requiring, re-measure magnetic field, continue even
?.Specifically: circulation executes step 1-4, until measurement uniformity of magnetic field, until reaching requirement.
It is worth noting that, step 5 may be replaced by:
Step 5 judges moving displacement distance lMAbsolute value whether reach requirement, if not up to require, re-measure magnetic
, continue shimming.Specifically: circulation executes step 1-4, until moving displacement distance lMAbsolute value, reaching requirement is
Only.
Preferably, the moving displacement distance lMAbsolute value be less than 0.05mm and be considered as and reach requirement.
Experiment and verifying
Fig. 5 is to record the table magnetic intensity of each magnet first according to Fig. 4 process, is updated to the optimization of magnet moving distance and calculates
The moving distance of each small magnet obtained in method.Wherein,
What the longitudinal axis of Fig. 5 represented is the moving distance of small magnet, and positive sign indicates that small magnet radial inward is mobile, and negative sign indicates
Radially move.It is humorous that the contribution of the non-uniformity in magnetic field caused by Halbach magnet system mostlys come from order magnetic field
Wave component, therefore carry out small magnet using 3 rank spherical-harmonic expansions and be displaced the calculating optimized.
Fig. 6 is the harmonic amplitude before and after mobile small magnet.After mobile small magnet, the harmonic wave intensity in magnetic field occurs some
Variation, but good suppression has been still carried out for high-intensitive harmonic component, to improve the whole of magnet system
The body uniformity.
Fig. 7 is the spherical surface Distribution of Magnetic Field that the mobile front and back measurement of small magnet obtains.Before non-moving magnet, due to adding for magnet
Caused by work error and tooling error, the uniformity of magnetic field within the scope of 10mm search coverage is 820ppm；However, when mobile small magnetic
After body, the uniformity of magnetic field within the scope of 10mm search coverage that measures again is 31ppm, 26 times of improving uniformity with
On, and the central magnetic field intensity of the mobile front and back of small magnet is 0.19T.
To the above description of all disclosed embodiments, professional and technical personnel in the field is made to can be realized or use this Shen
Please.Various modifications to these embodiments will be readily apparent to those skilled in the art, and determine herein
The General Principle of justice can be realized in other embodiments without departing from the spirit or scope of the application.Therefore, originally
Application is not intended to be limited to the embodiments shown herein, and is to fit to and the principles and novel features disclosed herein
Consistent widest scope.
Claims (10)
1. a kind of Halbach magnet system, which is characterized in that the Halbach magnet system is multilayer cyclic structure, by edge
The several layers magnet ring being axially layered on top of each other is constituted；Wherein,
The magnet ring is the cyclic structure that multiple small magnets surround, and each small magnet can be carried out moving radially.
2. a kind of Halbach magnet system according to claim 1, which is characterized in that between the adjacent small magnet
There is certain gap to facilitate and carry out radiai adjustment to small magnet.
3. a kind of Halbach magnet system according to claim 1, which is characterized in that the Halbach magnet system by
6 layers of magnet ring are constituted, and each layer of magnet ring is all made of 16 cylindrical small magnets；The diameter of each magnet ring is 70mm；It is each
The diameter of small magnet is 12mm, is highly 30mm.
4. a kind of high-precision, quick Halbach magnet based on any one of claim 1-3 Halbach magnet system are passive
Method for shimming, which is characterized in that the described method includes:
Small magnet is carried out numeral mark by S1, and records the Surface field intensity of each small magnet, total X small magnet；
S2 measures the magnetic field strength on the search coverage surface of magnet system under original state, and measurement point number is N, and measurement point is equal
It is even to be distributed on search coverage surface；
The target field magnetic field that the Surface field intensity of small magnet and measurement obtain is updated to and minimizes automatic optimal algorithm by S3
In, calculate the mobile distance l of each small magnetm；
S4 is by corresponding moving distance lmIt is corresponded with small magnet numeral mark, and corresponding small magnet is radially moved into correspondence
Position；
S5 judges whether to meet engineering precision, if not up to requiring, repeats step S1-S4, re-measures magnetic field, continue
Shimming；If reaching requirement, terminate.
5. a kind of high-precision according to claim 4, the quick passive method for shimming of Halbach magnet, which is characterized in that
Each small magnet corresponds to magnetic field strength caused by spherical surface position in search coverage are as follows:
Wherein, μ0For space permeability；I is the magnetizing current of magnet；Coordinate (x ', y ', z ') is small magnet under rectangular coordinate system
Position, (x, y, z) are the position of search coverage umbilical point；MzFor the residual magnetization obtained measured by each small magnet, S is magnet
The cross-sectional area of magnetizing direction.
6. a kind of high-precision according to claim 5, the quick passive method for shimming of Halbach magnet, which is characterized in that
Spheric harmonic function decomposition is carried out to the magnetic field strength on search coverage surface, obtains the spheric harmonics expansion under spherical coordinate system:
Wherein, BzIt is that measurement obtains the magnetic field distribution on search coverage surface；For the coordinate of measurement point, wherein r
It is spherical radius, θ is the elevation angle,For azimuth；M indicates the n-th ball harmonic component of spheric harmonics expansion, and n represents m rank ball
Harmonic component；It is n times m rank associated Legendre polynomial,WithIt is n times m rank ball harmonic component intensity respectively.
7. a kind of high-precision according to claim 6, the quick passive method for shimming of Halbach magnet, which is characterized in that
Total search coverage Surface field intensity distribution are as follows:
Magnetic field B0 after being superimposed by the humorous decomposition of ballzBall harmonic component wi, establish objective function:
Minimum value optimizing is carried out, optimal R ' value is obtained；Further according to lM=R '-R obtains the moving displacement distance of small magnet；
Wherein,
When optimization, R ' is optimized variable, R 'min≤R′≤R′max；R is the initial position radius of small magnet；R ' is mobile for small magnet
Position radius afterwards.
8. a kind of high-precision according to claim 4, the quick passive method for shimming of Halbach magnet, which is characterized in that
The step S5 specifically:
Measurement uniformity of magnetic field whether reach requirement, if Magnetic field inhomogeneity, repeat step S1-S4, re-measure magnetic field, continue into
Row shimming；If field homogeneity terminates.
9. a kind of high-precision according to claim 4, the quick passive method for shimming of Halbach magnet, which is characterized in that
The step S5 specifically:
Judge moving distance lMAbsolute value whether reach requirement, if not up to require, repeat step S1-S4, re-measure magnetic
, continue shimming；If reaching requirement, terminate.
10. a kind of high-precision according to claim 9, the quick passive method for shimming of Halbach magnet, feature exist
In if the moving distance lMAbsolute value be less than 0.05mm and reach requirement.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112034404A (en) * | 2020-09-03 | 2020-12-04 | 中国科学院精密测量科学与技术创新研究院 | External passive shimming device of Halbach array magnet for magnetic resonance |
| WO2021109847A1 (en) * | 2019-12-05 | 2021-06-10 | 湖南迈太科医疗科技有限公司 | Shimming control method, device, and system for magnetic resonance imaging |
| CN113296035A (en) * | 2021-05-24 | 2021-08-24 | 德惠市北方汽车底盘零部件有限公司 | Magnetic field detection assembly and ferromagnetic and magnetic material detector |
| CN113400317A (en) * | 2021-07-13 | 2021-09-17 | 上海交通大学 | Decoupling type control mechanism for magnetic field strong point and magnetic line direction |
| CN116380163A (en) * | 2023-03-29 | 2023-07-04 | 青岛峻海物联科技有限公司 | Sensing device for intelligent environment data acquisition of Internet of things |
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