Electromagnetic shielding effectiveness evaluation system for environmental laboratory

Abstract

The invention discloses an electromagnetic shielding effectiveness evaluation system for an environmental laboratory, which relates to the technical field of electromagnetic shielding effectiveness evaluation and comprises a signal source module, a shielding body test module, an electromagnetic field detection module, a data acquisition and processing module and a verification and calibration module. Wherein the signal source module and the shielding body test module are used as hardware parts and are necessary parts in the evaluation system, and the electromagnetic field detection module, the data acquisition and processing module and the verification and calibration module are used as software parts, so that high-efficiency evaluation processing on a product is also realized; the technical key points are as follows: the scheme not only ensures the accuracy and reliability of an evaluation result, but also improves the consistency and repeatability of evaluation, and a scientific and effective method is provided for the evaluation of the shielding effectiveness of the wire sleeve; meanwhile, the scheme is also helpful to timely discover and correct problems in evaluation, and ensures that the product can meet specific requirements in actual use.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic shielding effectiveness evaluation, and in particular to an electromagnetic shielding effectiveness evaluation system for an environmental test room. Background Art

[0002] Electromagnetic shielding effectiveness, referred to as SE, refers to the effective barrier capability of shielding materials to electromagnetic waves, and is used to describe the degree of attenuation of electromagnetic waves by the shielding body. In layman's terms, it is the ability of shielding materials to resist electromagnetic interference. In electromagnetic compatibility testing, the quality of shielding effectiveness directly affects the accuracy and reliability of test results. Electromagnetic shielding effectiveness is usually expressed in decibels (dB). The higher the decibel value, the better the shielding effectiveness of the material against electromagnetic waves.

[0003] There are many ways to evaluate the electromagnetic shielding effectiveness. Different test methods can be selected according to different test objects and frequency ranges. Common evaluation methods include the shielding room window test method and the small shielding body window test method. The shielding room window test method is mainly based on the principle of electromagnetic equilinear transmission lines. A window is opened on one side, and the sample is installed to test the transmission and reception of new signals. This method is suitable for larger shielding materials. Small shielding body window test method: This method is similar to the shielding room window test method, but the test window is usually 0.3 meters, which is suitable for plane wave far-field shielding effectiveness testing of smaller shielding materials, and the applicable frequency range is 1GHz to 18GHz.

[0004] The existing application number is 201910243430.9, and the document named "An electromagnetic shielding effectiveness measurement system and measurement method" points out: The measurement system includes an electromagnetic wave analysis device, an electromagnetic wave transmitting device and a transverse electromagnetic wave chamber; the electromagnetic wave transmitting device is arranged in the input window of the transverse electromagnetic wave chamber, and is used to send transverse electromagnetic waves to the transverse electromagnetic wave chamber; the first input end of the electromagnetic wave analysis device is connected to the first output end of the transverse electromagnetic wave chamber, and the second input end of the electromagnetic wave analysis device is connected to the second output end of the transverse electromagnetic wave chamber, and is used to determine the first coupling transmission coefficient and the second coupling transmission coefficient between the electromagnetic wave transmitting device and the transverse electromagnetic wave chamber according to the signal output from the first output end of the transverse electromagnetic wave chamber and the output signal from the second output end of the transverse electromagnetic wave chamber before setting the shielding material to be tested; after setting the shielding material to be tested, the third coupling transmission coefficient and the fourth coupling transmission coefficient between the electromagnetic wave transmitting device and the constant electromagnetic wave chamber are determined according to the signals output from the first output end and the second output end of the transverse electromagnetic wave chamber; but it cannot conduct comprehensive or targeted shielding effectiveness evaluation.

[0005] In combination with the above-mentioned prior art and documents:

[0006] The current mainstream solution is to analyze the product and evaluate the electromagnetic shielding effectiveness of the corresponding product through analysis feedback. However, the determination of the electromagnetic shielding effectiveness of the product is usually obtained by testing in a professional laboratory based on relevant standards. However, for those products with known electromagnetic shielding standard effectiveness, their effectiveness will be discounted after a period of use. For example, wear and tear in some parts or other conditions may affect the established electromagnetic shielding standard effectiveness of the product (such as cable sheath). If the original electromagnetic shielding effectiveness is still used, the accuracy of the effectiveness evaluation results will be reduced, and it will also be impossible to continue to conduct effective evaluation work on the same type of products. Summary of the invention

[0007] 1. Technical issues to be solved

[0008] In view of the deficiencies in the prior art, the present invention provides an electromagnetic shielding effectiveness evaluation system for an environmental test room, which can accurately evaluate used products of the same type and solve the problems raised in the background technology.

[0009] (II) Technical solution

[0010] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0011] An electromagnetic shielding effectiveness evaluation system for an environmental test chamber, comprising:

[0012] A signal source module generates electromagnetic signals of quantitative frequency and amplitude to simulate external electromagnetic interference and internal transmission signals;

[0013] Shielding test module, build an electromagnetic shielding room as an environmental test room, and design an adjustable bracket and fixture system and grounding device inside it; the adjustable bracket and fixture system is used to fix the product to be tested;

[0014] The electromagnetic field detection module uses n sets of flexible probes to obtain the strength data of the inner and outer parts of the product. It also builds a rule engine to set the number of flexible probes according to the thickness of the product, evenly set corresponding measurement points on the product, and output the strength data obtained by the flexible probes at the corresponding measurement points.

[0015] The data acquisition and processing module receives the output strength data, calculates and processes the average value of the internal strength data under the condition of obtaining the internal strength data of the product, and compares it with the strength data under the condition of no shielding to obtain the internal shielding effectiveness value; after the signal source generates the same electromagnetic signal, under the condition of obtaining the external strength data of the product, calculates and processes the average value of the external strength data, and compares it with the strength data under the condition of no shielding to obtain the external shielding effectiveness value, and uses a statistical algorithm model to process the internal and external shielding effectiveness values ​​to generate a comprehensive shielding effectiveness value;

[0016] The verification and calibration module performs several evaluation operations to obtain several comprehensive shielding effectiveness, and extracts the maximum value of several comprehensive shielding effectiveness. The shielding effectiveness of the known corresponding cable sheath is compared with the maximum value. If the difference between the two exceeds the preset judgment threshold, the calibration strategy is executed; otherwise, the acceptance strategy is executed.

[0017] Furthermore, the definition of the electromagnetic signal with a quantitative frequency and amplitude is as follows: the maximum value of the interference frequency and amplitude is selected from the historical interference data as the quantitative electromagnetic signal; the product uses a wire sheath that has been used for at least 1 year.

[0018] Furthermore, the value range of n is {1, 2, ..., N}, where N is a positive integer;

[0019] The specification engine is set as follows:

[0020] For wire sheaths with a thickness of less than 1 mm, at least M measuring points are set for every 10 cm length;

[0021] For wire sheaths with a thickness between 1 mm and 5 mm, M-1 measuring points are set every 10 cm in length;

[0022] For wire sheaths with a thickness greater than 5 mm, M-2 measuring points are set every 10 cm in length.

[0023] Furthermore, the intensity data represents the signal intensity, and the average value of the internal intensity data represents the average value of the data obtained at each measurement point.

[0024] Furthermore, the average value of the internal strength data is compared with the strength data without shielding to obtain the internal shielding effectiveness value, and the formula is as follows:

[0025]

[0026] In the formula, Tx in represents the internal shielding effectiveness value, oup represents the strength data without shielding, Indicates the average value of the product's internal strength data;

[0027] When comparing the average value of the external intensity data with the intensity data without shielding, the external shielding effectiveness value is obtained based on the following formula:

[0028]

[0029] Where, Tx out represents the external shielding effectiveness value, oup represents the strength data without shielding, Indicates the average value of the product's external strength data.

[0030] Furthermore, the statistical algorithm model used is a model for finding the geometric mean;

[0031] The formula used to generate the comprehensive shielding effectiveness value is as follows:

[0032]

[0033] Where Txz represents the comprehensive shielding effectiveness value.

[0034] Furthermore, the difference between the two represents: the difference between the known shielding effectiveness of the corresponding cable sheath and the comprehensive shielding effectiveness value, and the difference is always a positive number; the judgment threshold represents: the maximum value of the error between the actually calculated comprehensive shielding effectiveness value and the known shielding effectiveness of the corresponding cable sheath.

[0035] Furthermore, the calibration strategy implemented is:

[0036] Add a correction coefficient to the original formula for generating the comprehensive shielding effectiveness value, and build a correction model in combination with the known shielding effectiveness of the corresponding cable sheath to generate a comprehensive shielding effectiveness correction value, and re-perform several evaluation operations to obtain several comprehensive shielding effectiveness correction values, and extract the maximum value of the several comprehensive shielding effectiveness correction values, and compare the known shielding effectiveness of the corresponding cable sheath with the maximum value. If the difference between the two still exceeds the preset judgment threshold, reduce the correction coefficient by 0.1 each time until the difference between the two does not exceed the preset judgment threshold;

[0037] Among them, the formula for building a correction model and generating a comprehensive shielding effectiveness correction value is as follows:

[0038] Tx - =(1-k)*Txz+k*Bs;

[0039] In the formula, Txz - It represents the comprehensive shielding effectiveness correction value, k represents the correction coefficient, the initial setting value is 0.5, and Bs represents the known shielding effectiveness of the corresponding cable sheath.

[0040] Furthermore, the acceptance strategy implemented is: when the difference does not exceed the preset judgment threshold, the corresponding model under this condition is run to evaluate the same type of products.

[0041] (III) Beneficial effects

[0042] The present invention provides an electromagnetic shielding effectiveness evaluation system for an environmental test room, which has the following beneficial effects:

[0043] (1) A programmable signal generator is used to simulate external electromagnetic interference and internal transmission signals to ensure that the test environment is real and controllable. At the same time, by building an electromagnetic shielding room and designing adjustable brackets, fixture systems, and grounding devices, the stable fixation and good grounding of the product in a dynamic electromagnetic environment are ensured, avoiding interference from external factors.

[0044] This solution can accurately and comprehensively evaluate the shielding effectiveness of cable sheaths in complex electromagnetic environments, including shielding of external electromagnetic signals and leakage control of internal signals, thus improving the accuracy and reliability of the test;

[0045] (2) This solution not only improves the flexibility and adaptability of the measurement, but also ensures the accuracy and reliability of the evaluation results through the statistical algorithm model; the geometric mean value model is used to generate the comprehensive shielding effectiveness value, which further improves the comprehensiveness and scientificity of the evaluation; Overall, this technical solution provides an efficient and accurate method for evaluating the electromagnetic shielding effectiveness of cable sheaths;

[0046] (3) The comprehensive shielding effectiveness is obtained through multiple evaluation operations and compared with the shielding effectiveness of known cable sheaths. According to the comparison result between the difference and the preset judgment threshold, the corresponding calibration or acceptance strategy is executed; the calibration strategy builds a correction model by introducing a correction coefficient, adjusts the comprehensive shielding effectiveness value until the difference meets the requirements, and improves the accuracy of the evaluation; the acceptance strategy ensures that when the difference does not exceed the threshold, it can be reliably applied to the evaluation of the same type of products;

[0047] This solution not only ensures the accuracy and reliability of the evaluation results, but also improves the consistency and repeatability of the evaluation, providing a scientific and effective method for evaluating the shielding effectiveness of cable sheaths. At the same time, this solution also helps to promptly discover and correct problems in the evaluation, ensuring that the product can meet specific requirements in actual use. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a modular schematic diagram of an electromagnetic shielding effectiveness evaluation system for an environmental test room in the present invention;

[0049] Figure 2 This is a real cross-sectional view of the interior evaluation of the electromagnetic shielding room in the present invention. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] Embodiment 1:

[0052] See also Figure 1 This embodiment provides an electromagnetic shielding effectiveness evaluation system for an environmental test room. The system evaluates the electromagnetic shielding effectiveness of a product. At the same time, the product needs to be placed in the environmental test room. The environmental test room needs to ensure in advance that it will not be interfered by external electromagnetic interference, so as to facilitate subsequent evaluation work;

[0053] The assessment system includes:

[0054] Signal source module, shielding body test module, electromagnetic field detection module, data acquisition and processing module, and verification and calibration module; among them, the signal source module and shielding body test module are the hardware parts, which are an indispensable part of the evaluation system, and the electromagnetic field detection module, data acquisition and processing module, and verification and calibration module are the software parts, which also realize the efficient evaluation and processing of the product;

[0055] Signal source module:

[0056] Generate electromagnetic signals of quantitative frequency and amplitude to simulate external electromagnetic interference and internal transmission signals;

[0057] Among them, a programmable signal generator is used to evaluate the external electromagnetic interference shielding effectiveness of the product under the action of external electromagnetic signals under the condition of simulating external electromagnetic interference; under the condition of simulating internal transmission signals, it is used to evaluate the internal signal leakage shielding effectiveness of the product during normal operation;

[0058] The definition of electromagnetic signals with quantitative frequency and amplitude is as follows: the maximum interference frequency and amplitude are selected from the historical interference data as the quantitative electromagnetic signal, so that in subsequent tests, the evaluation results can more truly and accurately reflect the electromagnetic shielding effectiveness of the corresponding product;

[0059] The product in this embodiment is a wire cover that has been used for at least one year. The electromagnetic shielding effectiveness of the wire cover can no longer be judged according to the known effectiveness standard, so a test room needs to be built for re-judgment.

[0060] For the shielding performance evaluation of the cable sheath, bidirectional detection is required, that is, testing the influence of external electromagnetic signals on the inside of the cable sheath and the interference of the internal signals of the cable sheath on the external environment; it should be noted that the programmable signal generator can generate complex time-varying signals or pulse signals to simulate a dynamic electromagnetic environment. Users can set the waveform, frequency, amplitude and duration parameters of the signal through programming to meet the needs of different test scenarios;

[0061] Basic Overview of Programmable Signal Generators

[0062] Definition: A programmable signal generator is a comprehensive electronic instrument consisting of an oscillator, a frequency synthesis unit, and a modulation unit. It can not only provide sine wave signals and modulation wave signals, but also output a variety of complex waveforms through programming, such as square waves, triangle waves, sawtooth waves, and even arbitrary waveforms;

[0063] Function: Its basic function is to simulate various electromagnetic signals to test the performance of electronic equipment, such as electromagnetic compatibility (EMC) test, signal integrity test, etc. When simulating external electromagnetic interference, the programmable signal generator can accurately control the frequency, amplitude and phase of the signal to simulate the real interference environment;

[0064] Key parameters of programmable signal generators

[0065] Frequency: refers to the repetitive cycle rate of a signal. Programmable signal generators are usually able to cover a wide frequency range from a few hertz to tens of gigahertz. Amplitude: a measure of the "strength" of a waveform voltage. A programmable signal generator can set a voltage range, such as -3V to +3V, to generate a signal that fluctuates between two voltage values. Phase: indicates the position of a waveform relative to a reference waveform or time point. For some advanced applications, phase control is also an important function of a programmable signal generator.

[0066] Shielding test module:

[0067] Build an electromagnetic shielding room and design an adjustable bracket and clamp system and grounding device inside it;

[0068] The electromagnetic shielding room is used as an environmental test room to ensure that there is no interference from external factors during the evaluation. The adjustable bracket and clamp system is used to fix the product to be tested, ensuring that the cable sheath is stable in the dynamic electromagnetic environment and will not move due to external forces. The grounding device is used to connect the product to the ground terminal. The module should also have the ability to adapt to products of different sizes and types, and ensure that the position and grounding status of the product remain stable in the dynamic electromagnetic environment.

[0069] Reference Figure 2 It can be seen that the corresponding cable sheath runs through the entire electromagnetic shielding room. At the same time, the adjustable bracket and clamp system designed in the electromagnetic shielding room are fixed at both ends of the product respectively. Two sets of elastic wire clamps are used to support and fix the position of the product, so that it is always in a stretched state during the evaluation, ensuring that the product has no twists, wrinkles, etc., which is convenient for the subsequent evaluation process;

[0070] It can also be seen from the figure that for the cable sheath corresponding to the thickness H, for the subsequent inspection work, the number of inspection points is three, namely: inspection point A, inspection point B and inspection point C.

[0071] By adopting the above technical solution, the technical problem of accurately evaluating the electromagnetic shielding effectiveness of wire sheaths after at least one year of use is solved. Since the electromagnetic shielding effectiveness of such products can no longer be judged according to known standards, a special test room needs to be built for re-judgment;

[0072] In the technical solution, a programmable signal generator is used to simulate external electromagnetic interference and internal transmission signals to ensure that the test environment is real and controllable. At the same time, by building an electromagnetic shielding room and designing adjustable brackets, fixture systems and grounding devices, the stable fixation and good grounding of the product in a dynamic electromagnetic environment are ensured, avoiding interference from external factors.

[0073] This solution can accurately and comprehensively evaluate the shielding effectiveness of cable sheaths in complex electromagnetic environments, including the shielding of external electromagnetic signals and the leakage control of internal signals, which improves the accuracy and reliability of the test, provides strong technical support for the electromagnetic compatibility design and improvement of products, and ensures the stability and safety of products in actual use.

[0074] Electromagnetic field detection module:

[0075] Use n sets of flexible probes to obtain the strength data of the inner and outer parts of the product, build a rule engine simultaneously, set the number of flexible probes according to the thickness value of the product, evenly set corresponding measurement points on the product, and output the strength data obtained by the flexible probes at the corresponding measurement points;

[0076] Wherein, the value range of n is {1, 2, ..., N}, and N is a positive integer;

[0077] Flexible probes are probes designed to operate in confined spaces. They usually have bendable cables and a smaller diameter so that they can reach inside products, such as cable sheaths. Such probes are widely used in electromagnetic compatibility (EMC) testing, radio spectrum monitoring, and other fields.

[0078] Practical example:

[0079] When measuring the signal strength inside the cable sheath, a special flexible probe can be used. This probe extends into the cable sheath through a small hole or opening on the cable sheath to receive the signal from inside the cable. By configuring multiple such probes, the signal strength can be obtained at different measurement points and the average value can be calculated to reflect the actual signal strength.

[0080] The purpose of building a rule engine is to ensure that the number of measurement points is determined by the product, that is, the thickness of the cable sheath. The basic principle is that when the cable sheath is thin, more measurement points are needed to capture potential shielding effectiveness changes because the uniformity of material distribution and shielding effect may be poor. When the cable sheath is thick, the shielding effect is usually more stable, and the number of measurement points can be appropriately reduced.

[0081] Specific settings of the specification engine:

[0082] For wire sheaths with a thickness of less than 1 mm, at least M measuring points are set for every 10 cm length;

[0083] For wire sheaths with a thickness between 1 mm and 5 mm, M-1 measuring points are set every 10 cm in length;

[0084] For wire sheaths with a thickness greater than 5 mm, M-2 measuring points are set every 10 cm in length;

[0085] Among them, the value of M is usually 5;

[0086] The reasons are: Considering the uniformity of the material: thinner wire sheaths may be more prone to uneven material distribution during the manufacturing process, which will affect the shielding effectiveness; therefore, more measuring points are needed to accurately evaluate its shielding effect; Shielding effect stability: As the thickness of the wire sheath increases, the shielding effect is usually more stable because the thicker material layer can better block the penetration of electromagnetic waves; therefore, on thicker wire sheaths, the number of measuring points can be appropriately reduced; Measurement efficiency and accuracy: Under the premise of ensuring measurement accuracy, a reasonable setting of the number of measuring points can improve measurement efficiency. Too many measuring points will increase measurement time and cost, while too few measuring points may not accurately reflect the shielding effectiveness of the wire sheath.

[0087] Here is an example:

[0088] We set M=5 as the benchmark; according to this setting:

[0089] For wire sheaths with a thickness of less than 1 mm (e.g. 0.5 mm), 5 measuring points should be set for every 10 cm length;

[0090] For wire sheaths with a thickness between 1 mm and 5 mm (such as 1.2 mm and 2.5 mm), 4 measuring points should be set for every 10 cm length;

[0091] For wire sheaths with a thickness greater than 5 mm (such as 6.0 mm and 10.0 mm), three measuring points should be set for every 10 cm length;

[0092]

[0093] The above table lists 5 practical examples to illustrate the number of measurement points that should be set for every 10cm length of wire sheaths of different thicknesses.

[0094] Data acquisition and processing module:

[0095] Receive the output strength data, calculate and process the average value of the internal strength data under the condition of obtaining the internal strength data of the product, and compare it with the strength data under the unshielded condition to obtain the internal shielding effectiveness value; after the signal source generates the same electromagnetic signal, obtain the external strength data of the product, calculate and process the average value of the external strength data, and compare it with the strength data under the unshielded condition to obtain the external shielding effectiveness value, use the statistical algorithm model to process the internal and external shielding effectiveness values, and generate a comprehensive shielding effectiveness value;

[0096] Among them, the intensity data represents the signal strength;

[0097] The average value of the internal intensity data represents the average value of the data obtained at each measurement point;

[0098] The internal shielding effectiveness value is derived by comparing the average value of the internal strength data with the strength data without shielding, based on the following formula:

[0099]

[0100] Where, Tx in represents the internal shielding effectiveness value, oup represents the strength data without shielding, It represents the average value of the internal strength data of the product. The purpose of +1 is to avoid the situation where the denominator is 0;

[0101] When comparing the average value of the external intensity data with the intensity data without shielding, the external shielding effectiveness value is obtained based on the following formula:

[0102]

[0103] Where, Tx out represents the external shielding effectiveness value, oup represents the strength data without shielding, It represents the average value of the product's external strength data. The purpose of +1 is to avoid the situation where the denominator is 0;

[0104] It can be seen from this that the calculation principles for internal and external shielding effectiveness values ​​are the same;

[0105] The statistical algorithm model used is a model for finding the geometric mean;

[0106] The formula used to generate the comprehensive shielding effectiveness value is as follows:

[0107]

[0108] Where Txz represents the comprehensive shielding effectiveness value.

[0109] By adopting the above technical solution, the technical problems of unreasonable measurement point setting and complex data processing in the electromagnetic shielding effectiveness evaluation of the wire sheath are solved; the technical solution dynamically adjusts the number of measurement points according to the thickness of the wire sheath to ensure the accuracy and efficiency of the evaluation; at the same time, the strength data of the internal and external parts of the product are obtained by using a flexible probe, and accurate calculations are performed through the rule engine and data processing module to obtain the internal, external and comprehensive shielding effectiveness values;

[0110] This solution not only improves the flexibility and adaptability of the measurement, but also ensures the accuracy and reliability of the evaluation results through statistical algorithm models; in addition, the geometric mean model is used to generate the comprehensive shielding effectiveness value, which further improves the comprehensiveness and scientificity of the evaluation; overall, this technical solution provides an efficient and accurate method for evaluating the electromagnetic shielding effectiveness of cable sheaths, which helps to optimize product design, improve product performance, and ensure the electromagnetic compatibility of products in actual use.

[0111] Verify the calibration module:

[0112] Perform several evaluation operations to obtain several comprehensive shielding effectiveness, and extract the maximum value of several comprehensive shielding effectiveness, compare the known shielding effectiveness of the corresponding cable sheath with the maximum value, if the difference between the two exceeds the preset judgment threshold, execute the calibration strategy, and take the comprehensive shielding effectiveness correction value calculated in the strategy as the standard; if the difference between the two does not exceed the preset judgment threshold, execute the acceptance strategy, when the difference between the two does not exceed the preset judgment threshold directly, the calculated comprehensive shielding effectiveness value shall prevail, when the difference between the two does not exceed the preset judgment threshold after adjustment, the adjusted calculated comprehensive shielding effectiveness correction value shall prevail;

[0113] Among them, the shielding effectiveness of the corresponding cable sheath is known:

[0114] The shielding effectiveness of known cable sheaths is usually obtained through testing in professional laboratories based on relevant standards. During the test, precision equipment is used to simulate the actual working environment. The test report is issued by an authoritative organization to ensure accuracy and reliability.

[0115] The difference between the two represents:

[0116] The difference between the shielding effectiveness of the corresponding cable sheath and the comprehensive shielding effectiveness value is known, and the difference is always a positive number;

[0117] The judgment threshold represents the maximum value of the error between the actual calculated comprehensive shielding effectiveness value and the known shielding effectiveness of the corresponding cable sheath. In order to ensure accurate evaluation results, the maximum value of the error is set according to the actual situation. Usually, the maximum value of the error is 1% of the known shielding effectiveness of the corresponding cable sheath, and the maximum value of the error is used as the judgment threshold;

[0118] The calibration strategy implemented is:

[0119] Add a correction coefficient to the original formula for generating the comprehensive shielding effectiveness value, and build a correction model in combination with the known shielding effectiveness of the corresponding cable sheath to generate a comprehensive shielding effectiveness correction value, and re-perform several evaluation operations to obtain several comprehensive shielding effectiveness correction values, and extract the maximum value of the several comprehensive shielding effectiveness correction values, and compare the known shielding effectiveness of the corresponding cable sheath with the maximum value. If the difference between the two still exceeds the preset judgment threshold, reduce the correction coefficient by 0.1 each time until the difference between the two does not exceed the preset judgment threshold;

[0120] Among them, the formula for building a correction model and generating a comprehensive shielding effectiveness correction value is as follows:

[0121] Tx - =(1-k)*Txz+k*Bs;

[0122] In the formula, Txz - It represents the correction value of comprehensive shielding effectiveness, k represents the correction coefficient, the initial setting value is 0.5, and Bs represents the known shielding effectiveness of the corresponding cable sheath;

[0123] Here is an example:

[0124] Assuming Txz=10, Bs=30, and the initial difference Δ=20, we choose the correction coefficient k=0.5 to adjust the value of Txz.

[0125] Application formula:

[0126] Tx - =10+0.5*(30-10)=10+0.5*20=20;

[0127] The adjusted Txz value is Txz - =20, the difference with Bs is reduced to: |30-20|=10;

[0128] By introducing the correction coefficient k and adjusting the value of Txz, we can effectively reduce the difference between Txz and B. If the difference is still too large, the correction coefficient can be further adjusted to achieve the desired reduction effect.

[0129] The acceptance strategy implemented is:

[0130] When the difference does not exceed the preset judgment threshold, the corresponding model under this condition is run to evaluate products of the same type;

[0131] Products of the same type are also wire covers that have been used for at least 1 year.

[0132] By adopting the above technical solution, the accuracy and consistency problems in the shielding effectiveness evaluation of cable sheaths are solved; the technical solution obtains the comprehensive shielding effectiveness through multiple evaluation operations, and compares it with the shielding effectiveness of known cable sheaths, and executes the corresponding calibration or acceptance strategy according to the comparison result between the difference and the preset judgment threshold; the calibration strategy builds a correction model by introducing a correction coefficient, adjusts the comprehensive shielding effectiveness value until the difference meets the requirements, and improves the accuracy of the evaluation; the acceptance strategy ensures that when the difference does not exceed the threshold, it can be reliably applied to the evaluation of the same type of products;

[0133] This solution not only ensures the accuracy and reliability of the evaluation results, but also improves the consistency and repeatability of the evaluation, providing a scientific and effective method for evaluating the shielding effectiveness of cable sheaths. At the same time, this solution also helps to promptly discover and correct problems in the evaluation, ensuring that the product can meet specific requirements in actual use.

[0134] Embodiment 2:

[0135] Based on Example 1, this embodiment also provides an electromagnetic shielding effectiveness evaluation method for an environmental test room, comprising the following specific steps:

[0136] S1. Generate electromagnetic signals of quantitative frequency and amplitude using a signal source module to simulate external electromagnetic interference and internal transmission signals;

[0137] S2. Build an electromagnetic shielding room as an environmental test room, and design an adjustable bracket and fixture system and a grounding device inside it; the adjustable bracket and fixture system is used to fix the product to be tested;

[0138] S3. Use n sets of flexible probes to obtain the strength data of the inner and outer parts of the product, build a rule engine simultaneously, set the number of flexible probes according to the thickness value of the product, evenly set corresponding measurement points at the product, and output the strength data obtained by the flexible probes at the corresponding measurement points;

[0139] S4. Receive the output strength data, calculate the average value of the internal strength data under the condition of obtaining the internal strength data of the product, and compare it with the strength data under the unshielded condition to obtain the internal shielding effectiveness value; after the signal source generates the same electromagnetic signal, obtain the external strength data of the product, calculate the average value of the external strength data, and compare it with the strength data under the unshielded condition to obtain the external shielding effectiveness value, use the statistical algorithm model to process the internal and external shielding effectiveness values, and generate a comprehensive shielding effectiveness value;

[0140] S5. Perform several evaluation operations to obtain several comprehensive shielding effectiveness, and extract the maximum value of the comprehensive shielding effectiveness. Compare the known shielding effectiveness of the corresponding cable sheath with the maximum value. If the difference between the two exceeds the preset judgment threshold, execute the calibration strategy; otherwise, execute the acceptance strategy.

[0141] In the application, the several formulas involved are all calculated by taking their numerical values ​​after removing the dimensions, and the formulas are established by collecting a large amount of data and performing software simulation to obtain a formula for the most recent actual situation. Some coefficients or weights in the formulas are set by technical personnel in this field according to actual conditions, so they will not be elaborated here.

[0142] The above embodiments may be implemented in whole or in part by software, hardware, firmware or any other combination thereof. When implemented using software, the above embodiments may be implemented in whole or in part in the form of a computer program product. A person of ordinary skill in the art may appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein may be implemented in electronic hardware, or in a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution.

[0143] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, and may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0144] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. An electromagnetic shielding effectiveness evaluation system for an environmental test room, characterized in that: include: A signal source module generates electromagnetic signals of quantitative frequency and amplitude to simulate external electromagnetic interference and internal transmission signals; Shielding test module: build an electromagnetic shielding room as an environmental test room, and design an adjustable bracket and fixture system and grounding device inside it; the adjustable bracket and fixture system is used to fix the product to be tested; The electromagnetic field detection module uses n sets of flexible probes to obtain the strength data of the inner and outer parts of the product. It also builds a rule engine to set the number of flexible probes according to the thickness of the product, evenly set corresponding measurement points on the product, and output the strength data obtained by the flexible probes at the corresponding measurement points. The data acquisition and processing module receives the output strength data, calculates and processes the average value of the internal strength data under the condition of obtaining the internal strength data of the product, and compares it with the strength data under the condition of no shielding to obtain the internal shielding effectiveness value; after the signal source generates the same electromagnetic signal, under the condition of obtaining the external strength data of the product, calculates and processes the average value of the external strength data, and compares it with the strength data under the condition of no shielding to obtain the external shielding effectiveness value, and uses a statistical algorithm model to process the internal and external shielding effectiveness values ​​to generate a comprehensive shielding effectiveness value; The verification and calibration module performs several evaluation operations to obtain several comprehensive shielding effectiveness, and extracts the maximum value of several comprehensive shielding effectiveness. The shielding effectiveness of the known corresponding cable sheath is compared with the maximum value. If the difference between the two exceeds the preset judgment threshold, the calibration strategy is executed; otherwise, the acceptance strategy is executed.

2. The electromagnetic shielding effectiveness evaluation system for an environmental test room according to claim 1, characterized in that: The definition of electromagnetic signals with quantitative frequency and amplitude is: selecting the maximum interference frequency and amplitude from historical interference data as the quantitative electromagnetic signal; the product uses wire sheaths that have been used for at least 1 year.

3. The electromagnetic shielding effectiveness evaluation system for an environmental test room according to claim 2, characterized in that: The value range of n is {1, 2, ..., N}, where N is a positive integer; The specification engine is set as follows: For wire sheaths with a thickness of less than 1 mm, at least M measuring points are set for every 10 cm length; For wire sheaths with a thickness between 1 mm and 5 mm, M-1 measuring points are set every 10 cm in length; For wire sheaths with a thickness greater than 5 mm, M-2 measuring points are set every 10 cm in length.

4. The electromagnetic shielding effectiveness evaluation system for an environmental test chamber according to claim 3, characterized in that: The intensity data indicates the signal intensity, and the average value of the internal intensity data indicates the average value of the data acquired at each measurement point.

5. The electromagnetic shielding effectiveness evaluation system for an environmental test room according to claim 4, characterized in that: The internal shielding effectiveness value is derived by comparing the average value of the internal strength data with the strength data without shielding, based on the following formula: In the formula, Tx in represents the internal shielding effectiveness value, oup represents the strength data without shielding, Indicates the average value of the product's internal strength data; When comparing the average value of the external intensity data with the intensity data without shielding, the external shielding effectiveness value is obtained based on the following formula: In the formula, Tx out represents the external shielding effectiveness value, oup represents the strength data without shielding, Indicates the average value of the product's external strength data.

6. The electromagnetic shielding effectiveness evaluation system for an environmental test chamber according to claim 5, characterized in that: The statistical algorithm model used is a model for finding the geometric mean; The formula used to generate the comprehensive shielding effectiveness value is as follows: Where Txz represents the comprehensive shielding effectiveness value.

7. The electromagnetic shielding effectiveness evaluation system for an environmental test chamber according to claim 6, characterized in that: The difference between the two represents: the difference between the known shielding effectiveness of the corresponding cable sheath and the comprehensive shielding effectiveness value, and the difference is always a positive number; the judgment threshold represents: the maximum value of the error between the actual calculated comprehensive shielding effectiveness value and the known shielding effectiveness of the corresponding cable sheath.

8. The electromagnetic shielding effectiveness evaluation system for an environmental test chamber according to claim 7, characterized in that: The calibration strategy implemented is: Add a correction coefficient to the original formula for generating the comprehensive shielding effectiveness value, and build a correction model in combination with the known shielding effectiveness of the corresponding cable sheath to generate a comprehensive shielding effectiveness correction value, and re-perform several evaluation operations to obtain several comprehensive shielding effectiveness correction values, and extract the maximum value of the several comprehensive shielding effectiveness correction values, and compare the known shielding effectiveness of the corresponding cable sheath with the maximum value. If the difference between the two still exceeds the preset judgment threshold, reduce the correction coefficient by 0.1 each time until the difference between the two does not exceed the preset judgment threshold; Among them, the formula for building a correction model and generating a comprehensive shielding effectiveness correction value is as follows: Txz - =1-k*Txz+k*Bs; In the formula, Txz - It represents the comprehensive shielding effectiveness correction value, k represents the correction coefficient, the initial setting value is 0.5, and Bs represents the known shielding effectiveness of the corresponding cable sheath.

9. The electromagnetic shielding effectiveness evaluation system for an environmental test chamber according to claim 8, characterized in that: The acceptance strategy implemented is: when the difference does not exceed the preset judgment threshold, run the corresponding model under this condition to evaluate products of the same type.

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