Shielding effectiveness measuring method applied to shielding device for magnetic induction intensity measurement

Abstract

The invention discloses a shielding effectiveness measurement method applied to a shielding device for magnetic induction intensity measurement, and relates to the technical field of magnetic induction measurement, and the method comprises the steps: constructing a self-adaptive measurement time adjustment mechanism, employing a frequency conversion signal source, gradually increasing the frequency, measuring the magnetic induction intensity inside and outside the shielding device, and then calculating the shielding effectiveness. On the basis of shielding effectiveness curves under different frequencies, harmonic analysis is carried out on measured data, magnetic field data measured at each frequency point is taken, fast Fourier transform is carried out, and whether extra harmonic components exist or not is judged; and constructing a shielding effectiveness repairing mechanism, and filtering the measured magnetic induction data according to a harmonic analysis result. According to the method, frequency spectrum components of magnetic field data are extracted through fast Fourier transform, the total harmonic distortion rate is calculated, whether extra high-frequency interference exists in a shielding device or not is recognized, and a basis is provided for shielding optimization; and determining the key frequency of high-frequency shielding effectiveness reduction through harmonic influence evaluation.

Description

Technical Field

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

[0002] During the process of magnetic induction intensity measurement, external magnetic field interference will significantly affect the measurement accuracy. Therefore, an efficient shielding device is required to reduce the influence of the external magnetic field. Currently, the measurement of shielding effectiveness usually adopts single-point measurement or ideal model calculation. However, the following problems have not been effectively solved:

[0003] Existing methods usually measure the magnetic field intensity only at a single position, ignoring the possible phenomenon of local enhancement or weakening of the magnetic field inside the shielding device, resulting in the measurement results being difficult to accurately reflect the overall performance of the shielding device. Moreover, when measuring the magnetic field signal, high-order harmonic components may introduce additional errors. Especially in the high-frequency range, the shielding effectiveness of the shielding material decreases, and high-order harmonic signals may break through 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 for measuring the shielding effectiveness of a shielding device used for magnetic induction intensity measurement to solve the above problems. Summary of the Invention

[0005] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title. However, such simplifications or omissions shall not be used to limit the scope of the present invention.

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

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

[0008] Step 1: Construct an adaptive measurement time adjustment mechanism. Using a variable-frequency signal source, starting from the lowest frequency f min and gradually increasing the frequency. At each frequency point, measure the magnetic induction intensities inside and outside the shielding device, and then calculate the shielding effectiveness to obtain the shielding effectiveness curve 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 a fast Fourier transform, and determine whether there are additional harmonic components.

[0010] Step 3: Construct a shielding effectiveness repair mechanism, that is, filter the measured magnetic induction data according to the harmonic analysis results, correct the shielding effectiveness measurement value, and improve the shielding effectiveness curve.

[0011] As a preferred solution of the shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement according to the present invention, wherein: the adaptive measurement time adjustment mechanism further includes: adaptively adjusting the measurement time: that is, in the low-frequency band, the magnetic field changes slowly, so the measurement time is increased, and in the high-frequency band, the magnetic field changes quickly, so the measurement time is shortened. Specifically, a non-linear time adjustment function is used to control the measurement time, and the calculation formula is:

[0012]

[0013] wherein, T max is the maximum measurement time at the lowest frequency, and β is the coefficient controlling the measurement time attenuation rate.

[0014] As a preferred solution of the shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement according to the present invention, wherein: the calculation method of the shielding effectiveness is:

[0015] S101: Arrange a multi-point magnetic induction sensor matrix inside the shielding device, that is, through a spatial grid 9-point arrangement method, numbered i = 1, 2,..., 9, and measure the magnetic induction intensity B 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: Adopt a data fusion algorithm to integrate the optimized magnetic induction intensity data and calculate the comprehensive shielding effectiveness value SE(f).

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

[0019]

[0020] wherein, B in,f (f) represents the magnetic induction intensity 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 of the data fusion algorithm is:

[0022]

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

[0024] As a preferred solution of the shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement according to the present invention, wherein: according to the lowest frequency f min and the highest frequency f max during measurement, a frequency exponent weight α = 1 + (f - f min ) / (f max - f min ) is constructed to eliminate the inaccurate calculation caused by error amplification in the high-frequency part, which affects the overall evaluation; in the low-frequency part, the frequency exponent weight α is closer to 1 and the calculation result remains basically unchanged. In the high-frequency band, the frequency exponent weight α of the measured value increases to improve the credibility of the measurement data in the high-frequency band. Then the calculation formula of the final SE final (f) is:

[0025]

[0026] As a preferred solution of the shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement according to the present invention, wherein: the determination process of whether there is an additional harmonic component is as follows:

[0027] S301: Perform a fast Fourier transform on the optimized magnetic induction intensity B in,f (f);

[0028] S302: Extract the fundamental wave and harmonic components according to the Fourier transform result;

[0029] S302: Calculate the total harmonic distortion rate THD value of the measurement point according to the extracted fundamental wave and harmonic components, and 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 solution of the shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement according to the present 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 there is little harmonic interference, that is, the shielding effectiveness is mainly affected by the fundamental wave and there is no additional harmonic interference;

[0031] If the THD value is greater than the empirical threshold, it indicates that the magnetic field signal contains redundant harmonic components; it is necessary to further judge according to two cases of high frequency and low frequency:

[0032] If SE final (f) drops sharply at high frequencies and the THD value rises, it indicates that the shielding material has insufficient attenuation ability for high-frequency harmonics;

[0033] If the THD value is greater than the threshold at low frequencies, but SE final (f) does not show obvious abnormal changes, it indicates that the non-linear distortion of the measurement device causes interference from additional harmonics.

[0034] As a preferred solution of the shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement according to the present invention, wherein: 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. The memory stores a computer program, and when the processor executes the computer program, the steps of the above-mentioned shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement are implemented.

[0036] The present invention also discloses a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement are implemented.

[0037] Advantages of the present invention:

[0038] 1. The present invention adopts 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 ability of the shielding device at different frequencies and avoid the limitations of traditional single-frequency measurement methods.

[0039] 2. The present invention extracts the spectral components of the 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, the key frequencies for the decline of high-frequency shielding effectiveness are determined, providing data support for the material selection and structural optimization of the shielding device, thereby improving the stability and reliability of magnetic induction measurement. Description of the Drawings

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Among them:

[0041] Figure 1 It is the method flow chart of the shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement proposed by the present invention. Detailed Embodiments

[0042] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following detailed description of the specific embodiments of the present invention will be provided in conjunction with the accompanying drawings of the specification.

[0043] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0044] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation manner of the present invention. The phrase "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

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

[0046] Step 1: Construct an adaptive measurement time adjustment mechanism. Using a variable-frequency signal source, starting from the lowest frequency, gradually increase the frequency. Specifically: Let it start from the lowest frequency f min , and increase it step by step at an interval of Δf until the highest frequency f 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, by measuring the magnetic induction intensity inside and outside the shielding device, and then calculating the shielding effectiveness, a shielding effectiveness curve at different frequencies is obtained.

[0050] Specifically: The adaptive measurement time adjustment mechanism also includes: adaptively adjusting the measurement time: that is, in the low-frequency band, the magnetic field changes slowly, and a longer measurement time can obtain more stable data, so the measurement time is increased to improve the signal-to-noise ratio. In the high-frequency band, the magnetic field changes quickly, and too long a measurement time may cause data accumulation noise, affecting the accuracy of harmonic analysis, so the measurement time is shortened to reduce environmental noise interference. Specifically, a non-linear time adjustment function is used to control the measurement time, and the calculation formula is:

[0051]

[0052] Among them, T max is the maximum measurement time at the lowest frequency, and β is the coefficient controlling the measurement time decay rate, usually taking to ensure T(f max ) = T min .

[0053] The calculation method of shielding effectiveness is as follows:

[0054] S101: Arrange a multi-point magnetic induction sensor matrix inside the shielding device, that is, through a spatial grid 9-point arrangement method, numbered i = 1, 2,..., 9, to measure the magnetic induction intensity B in,i (f) at different positions.

[0055] S102: Based on the measurement time T(f), optimize the measured magnetic induction intensity according to the time-domain filtering optimization algorithm. Specifically, the calculation formula of the time-domain filtering optimization algorithm is:

[0056]

[0057] Among them, B in,f (f) represents the magnetic induction intensity inside the shielding device after filtering; f represents the current measurement frequency; j represents the imaginary unit; t0 represents the measurement start time. Through this integral calculation method, the noise components of non-target frequencies are removed, ensuring the accuracy of the measurement data.

[0058] S103: Adopt a data fusion algorithm to integrate the optimized magnetic induction intensity and calculate the comprehensive shielding effectiveness value SE(f).

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

[0060]

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

[0062] It should also be particularly noted that since the attenuation of the shielding material to the magnetic field 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 result is more sensitive to measurement errors, and some measurement errors are amplified, affecting the overall evaluation.

[0064] Therefore, in order to ensure the rationality of data at different frequencies in the calculation of shielding effectiveness, the present invention also designs a weight α that increases with the frequency; this weight is based on the lowest frequency f during measurementmin and the highest frequency f max Determine: α = 1 + (f - f min ) / (f max - f min ), in the low-frequency part, substitute this weight into the above SE(f) calculation process, and the calculation result remains basically unchanged. In the high-frequency band, the frequency exponent weight α of the measured value increases, improving the credibility of the measured data in the high-frequency band. The final formula for SE final (f) is:

[0065]

[0066] Step 2: Based on the shielding effectiveness curves at different frequencies, perform harmonic analysis on the measured 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: Perform a fast Fourier transform on the optimized magnetic induction intensity B in,f (f);

[0068] The specific change process is as follows:

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

[0070] S302: Extract the fundamental wave and harmonic components according to the Fourier transform result;

[0071] Calculate the fundamental wave component (i.e., the main signal frequency component): The meaning of the formula is: find the value corresponding to the main frequency f in the Fourier transform result and take its absolute value (i.e., the amplitude).

[0072] Calculate each order harmonic component: where m represents the harmonic order, M depends on the signal sampling bandwidth, usually M ≤ 10. mw represents the angular frequency of the harmonic. S302: To evaluate whether the shielding effectiveness is affected by harmonics, calculate the total harmonic distortion rate THD value,

[0073]

[0074] 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.

[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 there is little harmonic interference, that is, 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 excessive harmonic components; further judgment needs to be made according to two cases of high frequency and low frequency:

[0077] If SE final (f) drops significantly at high frequencies and the THD value rises, it indicates that the shielding material has insufficient attenuation ability for high-frequency harmonics. Generally, the possible reasons for this situation are: the conductivity and permeability of the shielding material decay rapidly at high frequencies; seams or gaps cause high-frequency signal leakage; the shielding structure generates a resonance effect at high frequencies, making it easier for harmonics to penetrate.

[0078] If the THD value is greater than the threshold at low frequencies, but SE final (f) does not show obvious abnormal changes, it indicates that the non-linear distortion of the measurement device causes interference from additional harmonics. Generally, the possible reasons are: the amplifier and sensor of the device generate additional harmonics when operating at low frequencies; 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, that is, according to the harmonic analysis results, if the THD value is greater than the threshold, the measured magnetic induction data is filtered by using a Butterworth low-pass filter to correct the shielding effectiveness measurement value and improve the shielding effectiveness curve.

[0080] In summary, the present invention uses the nine-point measurement method to collect magnetic field data at multiple measurement points inside the shielding device, and through the magnetic field data fusion algorithm and shielding effectiveness calculation, a complete shielding effectiveness curve is established, which can accurately describe the shielding ability of the shielding device at different frequencies, avoiding the limitations of the traditional single-frequency measurement method. The spectral components of the magnetic field data are extracted by fast Fourier transform, and the total harmonic distortion rate is calculated to identify whether there is additional high-frequency interference in the shielding device, providing a basis for shielding optimization; through harmonic impact assessment, the key frequencies for the decline in high-frequency shielding effectiveness are determined, 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, which is applicable to the situation of the shielding effectiveness measurement method for the shielding device used in magnetic induction intensity measurement, including: 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 implement the shielding effectiveness measurement method for the shielding device used in magnetic induction intensity measurement as proposed in the above embodiment.

[0082] The computer device can be a terminal, which includes a processor, a memory, a communication interface, a display screen, and an input device connected via a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The communication interface of the computer device is used to communicate with external terminals in a wired or wireless manner. The wireless manner can be achieved through WIFI, a carrier network, NFC (Near Field Communication), or other technologies. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device can be a touch layer covering the display screen, or buttons, a trackball, or a touchpad provided on the housing of the computer device, or an external keyboard, touchpad, or mouse, etc.

[0083] This embodiment also provides a storage medium, on which a computer program is stored. When the program is executed by a processor, it implements the shielding effectiveness measurement method for a shielding device applied to magnetic induction intensity measurement as proposed in the above embodiment; 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 Read-Only Memory (PROM), Read-Only Memory (ROM), magnetic memory, flash memory, a magnetic disk, or an optical disc.

[0084] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for measuring the shielding effectiveness of a shielding device applied to magnetic induction intensity measurement, characterized in that, The method includes the following steps: Build an adaptive measurement time adjustment mechanism. Using a variable-frequency signal source, starting from the lowest frequency f min and gradually increasing the frequency. At each frequency point, measure the magnetic induction intensity inside and outside the shielding device, then calculate the shielding effectiveness, and obtain the shielding effectiveness curve at different frequencies; 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 a fast Fourier transform, and determine whether there are additional harmonic components; Construct a shielding effectiveness repair mechanism, that is, filter the measured magnetic induction data according to the results of harmonic analysis, correct the measured shielding effectiveness value, and improve the shielding effectiveness curve.

2. The shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement according to claim 1, wherein: The adaptive measurement time adjustment mechanism further includes: adaptively adjusting the measurement time: that is, in the low-frequency band, the magnetic field changes slowly, so the measurement time is increased; in the high-frequency band, the magnetic field changes quickly, so the measurement time is shortened. Specifically, a non-linear 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 the coefficient that controls the measurement time decay rate.

3. The shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement according to claim 2, wherein: The calculation method of the shielding effectiveness is as follows: S101: Arrange a multi-point magnetic induction sensor matrix inside the shielding device, that is, through a spatial grid 9-point arrangement method, 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), optimize the measured magnetic induction intensity according to the time-domain filtering optimization algorithm; S103: Adopt a data fusion algorithm to integrate the optimized magnetic induction intensity and calculate the comprehensive shielding effectiveness value SE(f).

4. The shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement according to claim 3, wherein: The calculation formula of the time-domain filtering optimization algorithm is: Among them, B in,f (f) represents the magnetic induction intensity inside the shielding device after filtering; f represents the current measurement frequency; j represents the imaginary unit; t0 represents the starting time of measurement; The calculation formula of the data fusion algorithm is: Among them, w i represents the distance weight factor, and B out,i (f) represents the measured value of the external magnetic induction intensity.

5. The shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement according to claim 4, wherein: According to the lowest frequency f during measurement min and the highest frequency f max construct the frequency exponential weight α = 1 + (f - f min ) / (f max - f min ) to eliminate the inaccurate calculation and overall evaluation caused by the error amplification in the high-frequency part; in the low-frequency part, the frequency exponential weight α is closer to 1 and the calculation result remains basically unchanged. In the high-frequency band, the frequency exponential weight α of the measured value increases to improve the credibility of the measurement data in the high-frequency band, and then the final SE final (f) is calculated as follows:

6. The shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement according to claim 5, characterized in that: The determination process of whether there are additional harmonic components is as follows: S301: Perform a fast Fourier transform on the optimized magnetic induction intensity B in,f (f); S302: Extract the fundamental wave and harmonic components according to the Fourier transform results; S302: Calculate the total harmonic distortion rate THD value of the measurement point according to the extracted fundamental wave and harmonic components, and 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.

7. The method for measuring the shielding effectiveness of the shielding device applied to the magnetic induction intensity measurement according to claim 6, 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 there is little harmonic interference, 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 indicates that the magnetic field signal contains redundant harmonic components; further judgment needs to be made according to two cases of high frequency and low frequency: If SE final (f) drops significantly at high frequencies and the THD value increases, indicating that the shielding material has insufficient attenuation ability for high-frequency harmonics; If the THD value is greater than the threshold at low frequencies, but SE final (f) shows no obvious abnormal changes, it indicates that the non-linear distortion of the measuring device causes interference of additional harmonics.

8. The shielding effectiveness measurement method for the shielding device applied to magnetic induction intensity measurement according to claim 7, characterized in that: If the THD value is greater than the threshold, filter it by using a Butterworth low-pass filter.

9. A computer device, comprising a memory and a processor, the memory storing a computer program, characterized in that: When the processor executes the computer program, it implements the steps of the shielding effectiveness measurement method for the shielding device used for magnetic induction intensity measurement according to any one of claims 1 to 7.

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

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