Technical column



The importance of electromagnetic compatibility


       With the development of the world's industrial level, the requirements for electromagnetic compatibility equipment and application technology are getting higher and higher, and the demand is increasing. Electromagnetic compatibility has been widely used in many fields, and has been gradually recognized and valued by people. The scope of EMC disciplines is expanding day by day, and it is not limited to electronic equipment itself, but also involves a series of ecological effects such as electromagnetic pollution, electromagnetic starvation, and other problems. With the development of electromagnetic energy utilization, it will predict and control changes. The electromagnetic environment around the changing earth and celestial bodies, the control methods adopted to coordinate the environment, the formulation of various electrical regulations, the coordination of the electromagnetic environment and the rational application of electromagnetic energy, etc.

        At present, the scientific research, design, and application levels of my country's electromagnetic compatibility industry have been greatly improved, and new technologies and products have also been vigorously developed and produced. However, with my country's accession to WTO and the rapid development of industry, various industries in our country have higher and higher requirements for electromagnetic compatibility technology and products. Therefore, it is imperative to further strengthen the exchange and cooperation of EMC technology at home and abroad, and to accelerate the promotion and application of new technologies and products. With the development of science and technology, a large number of electrical and electronic products with high technical content and complex internal structure have been widely used. Electromagnetic interference leads to performance degradation of electrical and electronic products, and the phenomenon of being unable to work also occurs from time to time, which can cause quality accidents, equipment damage, and other immeasurable losses.

     In the electromagnetic environment, the hazards caused by electromagnetic interference are various, and may range from the simplest annoying phenomenon to serious disaster.

1   For the reliability of electronic equipment 

     Electromagnetic compatibility refers to the ability of electronic equipment to function properly in an electromagnetic environment. Electromagnetic interference is the phenomenon of electromagnetic changes that are detrimental to the performance of electronic equipment. Electromagnetic interference not only affects the normal operation of electronic equipment, but even causes damage to some components in electronic equipment. Therefore, sufficient attention should be paid to the electromagnetic compatibility technology of electronic equipment. It is necessary to pay attention to the fact that the electronic equipment can work normally without the surrounding electromagnetic interference, and also pay attention to that the electronic equipment itself does not generate electromagnetic interference to other surrounding equipment and affect the normal operation of other equipment.

2   For the international standard of electronic equipment

       Recently, electromagnetic compatibility has been developed from post-processing to pre-analysis, prediction and design. Electromagnetic compatibility has become an important part of modern engineering design. Electromagnetic compatibility certification has developed from a national scope to a global region, making electromagnetic compatibility, safety, and environmental adaptability equally important.

       For example, the European Community incorporates the electromagnetic compatibility requirements of products into technical regulations, and enforces the 89/336/EEC Directive, stipulating that electrical and electronic products must meet electromagnetic compatibility requirements from January 1, 1996, and affix the CE mark before being sold in the market. Products without CE shall not be listed on the market, and those that do not meet the requirements of the EMC directive will be ordered to withdraw from the market, and those who continue to violate will be severely punished. At present, the United States, Canada, Japan, Australia and other countries have promulgated corresponding regulations.

       In order to be in line with international standards, the Ministry of Foreign Economic Relations and the State Entry-Exit Inspection Bureau of my country implemented mandatory electromagnetic compatibility testing for personal computers, monitors, printers, switching power supplies, televisions and audio equipment in January 1999. The State Bureau of Technical Supervision stipulates that sound and television broadcasting equipment, information technology equipment, household appliances, electric tools, power supplies, lighting appliances, electric ignition drives, financial settlement electronic Implementation of compulsory certification of electromagnetic compatibility.

3    For the safety of personal and some special materials 

      The electromagnetic wave is inductively coupled with the control circuit of the electric explosive device, and the interference current formed may cause the explosion of the electric explosive device. Therefore, GJB786 stipulates that the electromagnetic interference induced current and voltage on the wire of the electric detonator must be less than 15% of the maximum non-fire current and voltage. In addition, various fuels may burn and explode under the action of strong electromagnetic fields (direct irradiation, electric sparks, electrostatic discharge); electromagnetic energy will produce harmful physiological effects through physical and chemical effects on human tissues. Therefore, for the safety of people and some special materials, GJB786 also stipulates that the average power density of continuous waves of electromagnetic radiation of electronic equipment is not allowed to exceed 4mW/cm 2 , and the average power density of pulse waves is not allowed to exceed 2mW / cm 2 .

4    For the needs of present and future warfare

      The electromagnetic pulse generated during a nuclear explosion radiates outward at the speed of light. Its electric field strength can reach 105V/m, magnetic field strength can reach 260A/m, the pulse width is on the order of 20ns, and the peak frequency of the electromagnetic pulse is 105Hz. When this electromagnetic pulse acts on electronic equipment, the light one will cause the performance of the electronic equipment to deteriorate, and the severe one will cause damage to the circuit components. Especially in today's and future wars, the electromagnetic pulse bombs that have been used and the high-power microwave weapons that are being developed all have electromagnetic pulse radiation similar to nuclear explosions, which will pose a fatal threat to electronic equipment. Electromagnetic compatibility can provide basic technical guidance for combating this threat.

In daily life, some possible harms caused by electromagnetic interference:

①Interfering with watching TV and listening to radio.

② Loss of data in the process of digital system and data transmission.

③ Destruction of normal operation at the equipment, subsystem or system level.

④Medical electronic equipment (such as medical monitors, cardiac pacemakers, etc.) is malfunctioning.

⑤ The automatic microprocessor control system (such as: the brake system of the car, the anti-collision airbag protection system) is out of control.

⑥The navigation system is malfunctioning.

⑦ Unintentional explosion of the detonating device.

⑧ Failure of industrial process control functions (eg petroleum or chemical industry).

In addition, strong electric fields can also affect living organisms, and so on.

It can be seen that the deterioration of the electromagnetic environment will lead to various consequences.

It is imperative to carry out electromagnetic compatibility research, strengthen electromagnetic compatibility management, reduce electromagnetic disturbance, and avoid electromagnetic interference.

       In order to make the product conform to the corresponding EMC standard before it becomes a commodity, necessary EMC testing during the development process will greatly benefit the stability of the product's own performance and the improvement of quality, and can save costs. Therefore, high-performance shielded computer rooms, EMC anechoic chambers and related professional electromagnetic compatibility testing instruments have become necessary equipment for electronic product development companies and manufacturers, and are also important symbols of the company's R&D strength and testing level.

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