Method for measuring shielding effectiveness applied to shielding device for magnetic induction intensity measurement

Abstract

The application discloses a shielding effectiveness measuring method applied to a shielding device for magnetic induction intensity measurement, relates to the technical field of magnetic induction measurement, and gradually improves the frequency by constructing a self-adaptive measuring time adjusting mechanism and utilizing a variable-frequency signal source, measures the magnetic induction intensity inside and outside the shielding device, then calculates the shielding effectiveness, carries out harmonic analysis on the measuring data based on the shielding effectiveness curve under different frequencies, takes the measured magnetic field data of each frequency point, carries out fast Fourier transform, and determines whether there is an additional harmonic component; a shielding effectiveness repairing mechanism is constructed, the measured magnetic induction data is filtered according to the harmonic analysis result, the spectrum component of the magnetic field data is extracted through fast Fourier transform, the total harmonic distortion rate is calculated, whether the shielding device has additional high-frequency interference is identified, and a basis is provided for shielding optimization; through harmonic influence evaluation, the key frequency of the decrease of the high-frequency shielding effectiveness is determined.

Description

Technical Field

[0001] This invention relates to the technical field of magnetic induction measurement, and more particularly to a method for measuring the shielding effectiveness of a shielding device used for measuring magnetic induction intensity. Background Technology

[0002] In the measurement of magnetic induction intensity, external magnetic field interference can significantly affect the measurement accuracy. Therefore, efficient shielding devices are needed to reduce the influence of external magnetic fields. Currently, the measurement of shielding effectiveness usually employs single-point measurement or calculation using ideal models. However, the following problems have not yet been effectively solved:

[0003] Existing methods typically measure magnetic field strength only at a single location, neglecting the potential for localized enhancement or weakening of the magnetic field within the shielding device. This leads to measurement results that fail to accurately reflect the overall performance of the shielding device. Furthermore, higher harmonic components can introduce additional errors when measuring magnetic field signals, especially in the high-frequency range where the shielding effectiveness of the material decreases, and higher harmonic signals may penetrate the shielding layer, affecting the measurement results. However, existing methods generally lack in-depth analysis of harmonic components.

[0004] Therefore, there is an urgent need for a method to measure the shielding effectiveness of shielding devices used for magnetic induction intensity measurement in order to solve the above problems. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the prior art, the present invention is proposed.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for measuring the shielding effectiveness of a shielding device used for measuring magnetic induction intensity, characterized in that the method includes the following steps:

[0008] Step 1: Construct an adaptive measurement time adjustment mechanism, using a frequency converter signal source, starting from the lowest frequency f min Initially, the frequency was gradually increased. At each frequency point, the magnetic induction intensity inside and outside the shielding device was measured, and then the shielding effectiveness was calculated to obtain the shielding effectiveness curves at different frequencies.

[0009] Step 2: Based on the shielding effectiveness curves at different frequencies, perform harmonic analysis on the measurement data, take the magnetic field data measured at each frequency point, perform fast Fourier transform, and determine whether there are additional harmonic components.

[0010] Step 3: Construct a shielding effectiveness repair mechanism, which involves filtering the measured magnetic induction data based on the harmonic analysis results, correcting the shielding effectiveness measurement value, and improving the shielding effectiveness curve.

[0011] As a preferred embodiment of the shielding effectiveness measurement method for a shielding device used in magnetic induction intensity measurement according to the present invention, the adaptive measurement time adjustment mechanism further includes: adaptive adjustment of the measurement time: that is, in the low-frequency range, the magnetic field changes slowly, so the measurement time is increased; in the high-frequency range, the magnetic field changes rapidly, so the measurement time is shortened. Specifically, a nonlinear time adjustment function is used to control the measurement time, and the calculation formula is as follows:

[0012]

[0013] Among them, T max β represents the maximum measurement time at the lowest frequency, and is a coefficient that controls the measurement time decay rate.

[0014] In a preferred embodiment of the shielding effectiveness measurement method for a shielding device used in magnetic induction intensity measurement according to the present invention, the shielding effectiveness is calculated as follows:

[0015] S101: A multi-point magnetic induction sensor matrix is ​​arranged inside the shielding device, that is, a spatially gridded 9-point arrangement, numbered i = 1, 2, ..., 9, to measure the magnetic induction intensity B at different locations. in,i (f);

[0016] S102: Based on the measurement time T(f), optimize the measured magnetic induction intensity according to the time domain filtering optimization algorithm;

[0017] S103: Using a data fusion algorithm, the optimized magnetic induction intensity is integrated to calculate the comprehensive shielding effectiveness value SE(f).

[0018] As a preferred embodiment of the shielding effectiveness measurement method for a shielding device used in magnetic induction intensity measurement according to the present invention, the calculation formula of the time-domain filtering optimization algorithm is as follows:

[0019]

[0020] Among them, B in,f (f) represents the magnetic field strength inside the shielding device after filtering; f represents the current measurement frequency; j represents the imaginary unit; t0 represents the measurement start time;

[0021] The calculation formula for the data fusion algorithm is as follows:

[0022]

[0023] Among them, w i B represents the distance weighting factor. out,i (f) represents the measured value of external magnetic induction intensity.

[0024] As a preferred embodiment of the shielding effectiveness measurement method for a shielding device used in magnetic induction intensity measurement according to the present invention, wherein: based on the lowest frequency f during measurement min and the highest frequency f max Construct the frequency exponential weight α = 1 + (ff) min ) / (f max -f min This eliminates the impact of error amplification in the high-frequency range on inaccurate calculations and overall evaluation; in the low-frequency range, the frequency exponent weight α is closer to 1, and the calculation result remains basically unchanged; in the high-frequency range, the frequency exponent weight α of the measured value increases, improving the reliability of the high-frequency measurement data, thus resulting in the final SE. final The formula for calculating (f) is:

[0025]

[0026] In a preferred embodiment of the shielding effectiveness measurement method for a shielding device used in magnetic induction intensity measurement according to the present invention, the process for determining whether there are additional harmonic components is as follows:

[0027] S301: Regarding the optimized magnetic flux density B in,f (f) Perform a fast Fourier transform;

[0028] S302: Extract fundamental and harmonic components based on Fourier transform results;

[0029] S302: Calculate the total harmonic distortion (THD) value of the measurement points based on the extracted fundamental and harmonic components, then take the average THD value of all measurement points and compare it with the set empirical threshold to determine whether the shielding effectiveness is affected by harmonics.

[0030] As a preferred embodiment of the shielding effectiveness measurement method for a shielding device for measuring magnetic induction intensity described in this invention, wherein: if the THD value is less than or equal to the empirical threshold, it indicates that the magnetic field signal is mainly composed of the fundamental wave and has little harmonic interference, that is, the shielding effectiveness is mainly affected by the fundamental wave and has no additional harmonic interference.

[0031] If the THD value is greater than this empirical threshold, it indicates that the magnetic field signal contains redundant harmonic components; further judgment is needed based on both high-frequency and low-frequency cases.

[0032] If SE final (f) If the THD value drops significantly at high frequencies and increases, it indicates that the shielding material is not strong enough to attenuate high-frequency harmonics.

[0033] If the THD value is greater than the threshold at low frequencies, but the SE final (f) If there are no obvious abnormal changes, it indicates that the nonlinear distortion of the measuring equipment causes interference from additional harmonics.

[0034] As a preferred embodiment of the shielding effectiveness measurement method for a shielding device used for measuring magnetic induction intensity according to the present invention, if the THD value is greater than the threshold, filtering is performed by using a Butterworth low-pass filter.

[0035] The present invention also discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described method for measuring the shielding effectiveness of a shielding device for measuring magnetic induction intensity.

[0036] The present invention also discloses a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the above-described method for measuring the shielding effectiveness of a shielding device for measuring magnetic induction intensity.

[0037] The beneficial effects of this invention are:

[0038] 1. This invention employs a nine-point measurement method to collect magnetic field data at multiple measurement points inside the shielding device. Through magnetic field data fusion algorithms and shielding effectiveness calculations, a complete shielding effectiveness curve is established, which can accurately describe the shielding capability of the shielding device at different frequencies, avoiding the limitations of traditional single-frequency measurement methods.

[0039] 2. This invention extracts the spectral components of magnetic field data through fast Fourier transform and calculates the total harmonic distortion rate to identify whether there is additional high-frequency interference in the shielding device, providing a basis for shielding optimization; through harmonic impact assessment, it determines the key frequencies that reduce the effectiveness of high-frequency shielding, providing data support for the material selection and structural optimization of the shielding device, thereby improving the stability and reliability of magnetic induction measurement. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0041] Figure 1 This is a flowchart of the method for measuring the shielding effectiveness of a shielding device for measuring magnetic induction intensity, as proposed in this invention. Detailed Implementation

[0042] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0043] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0044] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0045] Reference Figure 1 As an embodiment of the present invention, a method for measuring the shielding effectiveness of a shielding device for measuring magnetic induction intensity is provided. This method includes the following steps:

[0046] Step 1: Construct an adaptive measurement time adjustment mechanism using a frequency converter, starting from the lowest frequency and gradually increasing the frequency. Specifically: Let the lowest frequency f be... min Initially, the frequency is gradually increased by step intervals Δf until the highest frequency f is reached. max :

[0047] f n =f min +n·Δf, n=0,1,2,...,N f .

[0048] Where, N f =(f max -f min ) / Δf is the number of frequency points scanned.

[0049] At each frequency point, the shielding effectiveness curves at different frequencies are obtained by measuring the magnetic induction intensity inside and outside the shielding device and then calculating the shielding effectiveness.

[0050] Specifically, the adaptive measurement time adjustment mechanism also includes: adaptive adjustment of measurement time: In the low-frequency range, the magnetic field changes slowly, and a longer measurement time yields more stable data, so the measurement time is increased to improve the signal-to-noise ratio. In the high-frequency range, the magnetic field changes rapidly, and an excessively long measurement time may lead to noise accumulation in the data, affecting the accuracy of harmonic analysis. Therefore, the measurement time is shortened to reduce environmental noise interference. Specifically, a nonlinear time adjustment function is used to control the measurement time, and the calculation formula is as follows:

[0051]

[0052] Among them, T max β represents the maximum measurement time at the lowest frequency, and is a coefficient that controls the measurement time decay rate; it is typically taken as... Guarantee T(f) max ) = T min .

[0053] The method for calculating shielding effectiveness is as follows:

[0054] S101: A multi-point magnetic induction sensor matrix is ​​arranged inside the shielding device, that is, a spatially gridded 9-point arrangement, numbered i = 1, 2, ..., 9, to measure the magnetic induction intensity B at different locations. in,i (f).

[0055] S102: Based on the measurement time T(f), the measured magnetic flux density is optimized using a time-domain filtering optimization algorithm. Specifically, the calculation formula for the time-domain filtering optimization algorithm is as follows:

[0056]

[0057] Among them, B in,f (f) represents the magnetic flux density within the shielded device after filtering; f represents the current measurement frequency; j represents the imaginary unit; t0 represents the measurement start time. This integral calculation method removes noise components from non-target frequencies, ensuring the accuracy of the measurement data.

[0058] S103: Using a data fusion algorithm, the optimized magnetic induction intensity is integrated to calculate the comprehensive shielding effectiveness value SE(f).

[0059] The calculation formula for the data fusion algorithm is:

[0060]

[0061] Among them, w i B represents the distance weighting factor. out,i (f) represents the measured value of external magnetic induction intensity.

[0062] It should also be noted that the attenuation of magnetic fields by shielding materials usually follows an exponential decay relationship;

[0063] When f is small, the shielding effectiveness is mainly determined by the low-frequency characteristics of the material. When f increases, the calculation results are more sensitive to measurement errors, and some measurement errors are amplified, affecting the overall evaluation.

[0064] Therefore, to ensure the rationality of data from different frequencies in the shielding effectiveness calculation, this invention also designs a weight α that increases with frequency; this weight is based on the lowest frequency f during measurement.min and the highest frequency f max Determine: α = 1 + (ff) min ) / (f max -f min In the low-frequency range, this weight is substituted into the SE(f) calculation process described above, and the calculation result remains basically unchanged. In the high-frequency range, the frequency exponential weight α of the measured value is increased, improving the reliability of the high-frequency measurement data. The final SE after substitution... final The formula for calculating (f) is:

[0065]

[0066] Step 2: Based on the shielding effectiveness curves at different frequencies, perform harmonic analysis on the measurement data. Take the magnetic field data measured at each frequency point and perform a fast Fourier transform to determine whether there are additional harmonic components. Specifically, the determination process is as follows:

[0067] S301: Regarding the optimized magnetic flux density B in,f (f) Perform a fast Fourier transform;

[0068] The specific process of change is as follows:

[0069] Where w = 2πf is the angular frequency, representing the frequency of the main signal we applied; the result It shows the spectral distribution of magnetic field data at different frequencies;

[0070] S302: Extract fundamental and harmonic components based on Fourier transform results;

[0071] Calculate the fundamental component (i.e., the main signal frequency component): The formula means: find the value in the Fourier transform result that corresponds to the dominant frequency f, and take its absolute value (i.e., the amplitude).

[0072] Calculate the harmonic components of each order: Where m represents the harmonic order, M depends on the signal sampling bandwidth, and is typically M≤10. mw represents the angular frequency of the harmonic. S302: To evaluate whether the shielding effectiveness is affected by harmonics, the total harmonic distortion (THD) value is calculated.

[0073]

[0074] Then, the average THD value of all measurement points is taken and compared with the set empirical threshold to determine whether the shielding effectiveness is affected by harmonics.

[0075] If the THD value is less than or equal to this empirical threshold, it indicates that the magnetic field signal is mainly composed of the fundamental wave and has little harmonic interference. In other words, the shielding effectiveness is mainly affected by the fundamental wave and there is no additional harmonic interference.

[0076] If the THD value is greater than this empirical threshold, it indicates that the magnetic field signal contains redundant harmonic components; further judgment is needed based on both high-frequency and low-frequency cases.

[0077] If SE final (f) If the THD value drops significantly at high frequencies and increases, it indicates that the shielding material is not strong enough to attenuate high-frequency harmonics. Generally, the possible reasons for this are: the conductivity and permeability of the shielding material decrease rapidly at high frequencies; seams or gaps cause high-frequency signal leakage; the shielding structure generates a resonance effect at high frequencies, making harmonics easier to penetrate.

[0078] If the THD value is greater than the threshold at low frequencies, but the SE final (f) If there are no obvious abnormal changes, it indicates that the nonlinear distortion of the measuring equipment causes interference from additional harmonics. Generally, possible causes are: the amplifier or sensor of the equipment generates additional harmonics when operating at low frequencies; or there are additional interference signals in the measurement environment, resulting in harmonics in the measurement data.

[0079] Step 3: Construct a shielding effectiveness repair mechanism. Based on the harmonic analysis results, if the THD value is greater than the threshold, the measured magnetic induction data is filtered using a Butterworth low-pass filter to correct the shielding effectiveness measurement value and improve the shielding effectiveness curve.

[0080] In summary, this invention employs a nine-point measurement method to collect magnetic field data at multiple measurement points inside the shielding device. Through magnetic field data fusion algorithms and shielding effectiveness calculations, a complete shielding effectiveness curve is established, which can accurately describe the shielding capability of the shielding device at different frequencies, avoiding the limitations of traditional single-frequency measurement methods. By extracting the spectral components of the magnetic field data through fast Fourier transform and calculating the total harmonic distortion rate, it identifies whether there is additional high-frequency interference in the shielding device, providing a basis for shielding optimization. Through harmonic impact assessment, it determines the key frequencies at which high-frequency shielding effectiveness decreases, providing data support for material selection and structural optimization of the shielding device, thereby improving the stability and reliability of magnetic induction measurement.

[0081] This embodiment also provides a computer device applicable to the shielding effectiveness measurement method of a shielding device for measuring magnetic induction intensity, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to realize the shielding effectiveness measurement method for a shielding device for measuring magnetic induction intensity as proposed in the above embodiment.

[0082] The computer device can be a terminal, comprising a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0083] This embodiment also provides a storage medium storing a computer program, which, when executed by a processor, implements the shielding effectiveness measurement method for a shielding device used for measuring magnetic induction intensity as proposed in the above embodiments. The storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0084] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method of measuring the shielding effectiveness of a shielding device for use in the measurement of magnetic induction, characterized in that, The method comprises the following steps: An adaptive measurement time adjustment mechanism is constructed, and a variable frequency signal source is used to start from the lowest frequency f min First, the frequency is gradually increased, and at each frequency point, the magnetic induction intensity inside and outside the shielding device is measured, and then the shielding effectiveness is calculated to obtain the shielding effectiveness curve at different frequencies. Based on the shielding effectiveness curve at different frequencies, the harmonic analysis is performed on the measured data, the magnetic field data measured at each frequency point is taken, and the fast Fourier transform is performed to determine whether there is an additional harmonic component; A shielding effectiveness repair mechanism is constructed, that is, the measured magnetic induction data is filtered according to the harmonic analysis result to correct the shielding effectiveness measurement value and perfect the shielding effectiveness curve; The adaptive measurement time adjustment mechanism further comprises: adaptive adjustment of the measurement time, that is, the measurement time is increased at a low frequency band where the magnetic field changes slowly, and the measurement time is shortened at a high frequency band where the magnetic field changes quickly, and a nonlinear time adjustment function is used to control the measurement time, and the calculation formula is: where T max is the maximum measurement time at the lowest frequency, and β is a coefficient that controls the rate of decay of the measurement time. The shielding effectiveness calculation method is: S101: A multi-point magnetic induction sensor matrix is arranged inside the shielding device, i.e. through a spatial gridding 9-point arrangement, numbered i = 1, 2,..., 9, to measure the magnetic induction intensity B at different positions in,i (f); S102: Based on the measurement time T(f), the time domain filtering optimization algorithm is used to optimize the measured magnetic induction intensity; S103: The data fusion algorithm is used to integrate the optimized magnetic induction intensity to calculate the comprehensive shielding effectiveness value SE(f); The calculation formula of the time domain filtering optimization algorithm is: where B in,f (f) represents the magnetic induction within the shielded device after filtering; f represents the current measurement frequency; j represents the imaginary unit; t0represents the measurement start time; The calculation formula of the data fusion algorithm is: where w i represents a distance weight factor, B ＝>％,i (f) represents an external magnetic induction measurement value.

2. The method for measuring shielding effectiveness of a shielding device for magnetic field intensity measurement according to claim 1, characterized by: According to the lowest frequency f min and the highest frequency f ma@ of the measurement min , the frequency index weight α = 1 + (f-f ma@ ) / (f min ) is constructed to eliminate the influence of the high frequency part due to error amplification, resulting in inaccurate calculation affecting the overall evaluation; in the low frequency part, the frequency index weight α is closer to 1, and the calculation result is basically unchanged; in the high frequency band, the frequency index weight α of the measurement value increases, improving the reliability of the measurement data in the high frequency band, and then the final SE final (f) is calculated as follows:

3. The method for measuring shielding effectiveness of a shielding device for magnetic field induction metering according to claim 2, characterized in that: The determination process of whether there is an additional harmonic component is: S301: performing optimization on the magnetic induction intensity B in,f (f) performing a fast Fourier transform; S302: The fundamental wave and harmonic component are extracted according to the Fourier transform result; S302: The total harmonic distortion rate THD value of the measurement point is calculated according to the extracted fundamental wave and harmonic component, and then the average THD value of all measurement points is taken to compare with the set empirical threshold to determine whether the shielding effectiveness is affected by the harmonic.

4. The method for measuring shielding effectiveness of a shielding device for magnetic field induction metering according to claim 3, characterized in that: According to the THD value less than or equal to the empirical threshold, it is indicated that the magnetic field signal is mainly composed of the fundamental wave and the harmonic interference is small, that is, the shielding effectiveness is mainly affected by the fundamental wave and there is no additional harmonic interference; If the THD value is greater than the empirical threshold, it is indicated that the magnetic field signal contains an extra harmonic component; further judgment needs to be made according to the high frequency and low frequency conditions: If SE final (f) The THD value rises and the attenuation ability of the shielding material for high frequency harmonic is insufficient. If the THD value at low frequencies is greater than the threshold, but SE final (f) No significant abnormal change, which indicates that the non-linear distortion of the measuring equipment causes interference of additional harmonics.

5. The method for measuring shielding effectiveness of a shielding device for magnetic field induction strength measurement according to claim 4, characterized in that: If the THD value is greater than the threshold, the Butterworth low-pass filter is used for filtering.

6. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that: The processor executes the computer program to realize the steps of the shielding effectiveness measurement method for the shielding device for magnetic induction intensity measurement according to any one of claims 1-4.

7. A computer readable storage medium having stored thereon a computer program, characterized in that: The computer program is executed by the processor to realize the steps of the shielding effectiveness measurement method for the shielding device for magnetic induction intensity measurement according to any one of claims 1-4.

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