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Electromagnetic compatibility of security electronic system

this paper makes a preliminary analysis of the requirements and current situation of electromagnetic compatibility of security electronic system. A large number of electronic devices and devices are used in the security electronic system. These devices and devices will release (radiate) and receive a large amount of electromagnetic interference when they work normally. At present, the electromagnetic compatibility of security electronic system is not optimistic. Compared with other conventional electronic systems, the security electronic system is often considered to have a high important position. When designing the security electronic system, it often ignores its own electromagnetic disturbance to the outside world. Through the actual test results, this paper gives the conclusion that we should pay attention to the technical indicators of electromagnetic disturbance while paying attention to the electromagnetic immunity, and suggests that we should formulate the corresponding technical standards and inspection rules as soon as possible

1. Overview

security, referred to as security, belongs to the category of public security system, which aims to maintain social public security. Security involves all aspects of society, such as party and government organs, military facilities, national energy system, radio and television, communication system, key cultural relics units, banks, warehouses, commercial buildings, residential areas, etc. the security work in these places is very important, and it is also the content that security technology should focus on. In order to prevent invasion, theft and destruction, electronic devices and electronic equipment based on electronic technology, sensor technology and computer technology are widely used in the security system, and they form a system, which is called security electronic system

electromagnetic compatibility, referred to as EMC, is a comprehensive discipline. Article 5.10 of the national military standard gjb72-85 "electromagnetic compatibility interference and electromagnetic compatibility terminology" defines electromagnetic compatibility as follows: the coexistence state in which equipment (subsystems, systems) can perform their respective functions together in a common electromagnetic environment, that is, the equipment will not suffer from the unacceptable performance degradation caused by the electromagnetic emission of other equipment in the same electromagnetic environment; It will not cause other equipment (subsystems, systems) in the same electromagnetic environment to suffer or suffer from unacceptable performance degradation due to its electromagnetic emission. This coexistence state is called electromagnetic compatibility (EMC). Electromagnetic compatibility is divided into two aspects, one is electromagnetic immunity, the other is electromagnetic disturbance. Electromagnetic immunity refers to the ability of the system itself to resist external electromagnetic interference; Electromagnetic disturbance refers to the ability of the system itself to generate electromagnetic interference to the outside world

due to the use of a large number of electronic devices and electronic equipment in the security electronic system, these devices and equipment will release (radiate) and receive a large amount of electromagnetic interference energy when they work normally. Once these are ignored in the system design, not only the working performance level of the equipment or the system may decline or work abnormally, Moreover, other electronic equipment or systems adjacent to or functionally related to this system will also suffer from the decline of working performance level or abnormal operation due to its electromagnetic interference. In serious cases, it will fail to work normally or stop using, which will eventually lead to the embarrassing situation of having to redesign the system. At present, compared with other conventional electronic systems, security electronic systems are often considered to have a higher important position. When designing security electronic systems, they often ignore their own electromagnetic disturbance to the outside world and only pay attention to their own electromagnetic immunity. According to the theory of electromagnetic compatibility, the reason is basically connection failure. Systems with electromagnetic disturbance exceeding the standard limit will have many hidden dangers in electromagnetic immunity. The author himself has deep feelings in this regard based on years of practical work experience

2. Requirements for electromagnetic compatibility of security electronic system

security electronic system is usually composed of detector, signal transmission channel and controller. Almost all parts of the security electronic system are inseparable from electronic devices or electronic equipment (the application of electronic technology accounts for more than 95% of the application technology of the whole system). Therefore, it involves the problem of how to meet the requirements of electromagnetic compatibility between various parts of the security electronic system or between the security electronic system and other electronic systems in the same electromagnetic environment, so as to avoid the mutual interference between equipment or systems, resulting in the degradation of performance level or the phenomenon of failure to work normally. At present, there is not a complete national or industrial electromagnetic compatibility standard for electronic devices or electronic equipment used in security electronic systems in the field of security. In terms of electromagnetic immunity, up to now, most products have adopted the series standards of gb/t 17626-1998 electromagnetic compatibility immunity test method. It should be pointed out here that the severity level of gb/t 17626 immunity test needs to be determined by the product manufacturer himself, who has always firmly controlled the majority of the parliament. Sometimes, in order to make the products successfully pass the immunity test, the product manufacturer often determines the severity level of the test as a lower level. Although the immunity test can be successfully passed, it leaves a potential safety hazard to the security electronic system. In order to avoid this phenomenon, higher electromagnetic immunity requirements should be put forward for electronic devices or electronic equipment applied in the security electronic system. According to years of practical work experience, the severity level of its immunity test should meet the requirements of level 3 or above. Only in this way can the security electronic system work safely, reliably and stably. In terms of electromagnetic disturbance, because the security electronic system has a special position compared with other conventional electronic systems, people pay little attention to the problem of electromagnetic disturbance caused by the security electronic system to the outside world, and the electronic devices or electronic equipment used in the system rarely carry out electromagnetic disturbance tests, especially the electromagnetic radiation disturbance tests, This situation should be changed as soon as possible. At present, our country has integrated electromagnetic compatibility and environmental protection, and is striving to create a clean electromagnetic environment. The requirements that electronic products or electronic systems should meet electromagnetic compatibility have been included in the scope of national enforcement. It is hoped that the application of security electronic system will not make the current electromagnetic environment worse, which also hopes to attract the attention of peers in the security field, and formulate the electromagnetic compatibility technical standards and inspection rules of security electronic products as soon as possible

recently, the Ministry of construction and the General Administration of quality supervision, inspection and Quarantine jointly issued GB 50348 "technical specifications for safety protection engineering", which has been implemented since December 1, 2004. A total of 43 people from 25 units (after 5 years) participated in the drafting of this standard. In this standard, the design requirements of safety and electromagnetic compatibility are put forward for the first time in the design of security engineering. At the same time, in the inspection of security engineering, the inspection requirements of safety and electromagnetic compatibility are also put forward for the first time, which is a very good start. However, it is a pity that the whole standard still only pays attention to the technical requirements of electromagnetic immunity, and does not involve the technical requirements of electromagnetic harassment

3. Current situation of electromagnetic compatibility of electronic products of security system

electromagnetic compatibility of security electronic system can be considered from two aspects: one is electromagnetic compatibility of security electronic system engineering; On the other hand, it is the electromagnetic compatibility of electronic devices or electronic equipment used in system engineering. The electromagnetic compatibility of fully biodegradable packaging waste of electronic devices or electronic equipment under composting conditions is a necessary condition to ensure the electromagnetic compatibility of the whole security electronic engineering. At present, the electronic devices or electronic equipment constituting the security electronic system engineering can basically meet the needs in terms of electromagnetic immunity, but most of them are unsatisfactory in terms of electromagnetic disturbance. The following is the actual test results to illustrate this problem. The author has carried out electromagnetic radiation conduction disturbance and electromagnetic radiation emission disturbance test on typical equipment commonly used in security electronic system engineering, such as video monitoring host and visual intercom host, respectively. The test results are as follows:

Figure 1 shows the electromagnetic radiation conduction test results at the power supply (AC220V) port of visual intercom host (before rectification). Figure 2 shows the test results of the same host after rectification. Comparing the two test results, it can be seen that the electromagnetic disturbance index of the visual intercom host before rectification is very poor (as shown in Figure 1). After improvement, it can meet the requirements of the application (as shown in Figure 2). Figure 3 shows the electromagnetic radiation emission disturbance test of the video monitoring host, with the test distance of 1m. We can see from Figure 3 that the electromagnetic radiation emission disturbance of the video monitoring host is relatively serious, and this phenomenon cannot be known without actual testing, which is a potential safety hazard

Figure 1 test of electromagnetic radiation conduction of power port of visual intercom host (before rectification)

Figure 2 test of electromagnetic radiation conduction of power port of visual intercom host (after rectification)

Figure 3 test of electromagnetic radiation emission disturbance of video monitoring host

4. Conclusion

the electromagnetic compatibility of security electronic system is a comprehensive index to measure the electromagnetic immunity and electromagnetic disturbance of the system itself. Once the system design is completed, it is very difficult to carry out rectification. Therefore, in order to improve the technical index of electromagnetic compatibility of the system, it must be considered in the design stage of the system, so as to get twice the result with half the effort. In the long run, the security electronic system should improve the requirements for electromagnetic compatibility. While paying attention to the electromagnetic immunity of the system itself, we should also pay attention to the technical indicators of electromagnetic disturbance. Because the occurrence of electromagnetic disturbance will not only interfere with the normal work of various components in the system, resulting in interference in the system, but also cause mutual interference between systems, resulting in mutual compatibility between systems in the same environment. This phenomenon should be avoided. (end)