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1. Electromagnetic Compatibility
It means that an electronic device neither interferes with nor is not affected by other devices. Electromagnetic compatibility, like the safety we are familiar with, is one of the indicators of product quality. Safety concerns people and property, while electromagnetic compatibility concerns the protection of people and the environment.
2. Design principles
EMC design should be part of the comprehensive design of any electronic device and system. It is far more cost-effective than other methods of trying to achieve EMC for a product. The main design techniques of EMC include: electromagnetic shielding method, filtering technology of circuit, and grounding design including bonding of grounding components that should be paid special attention to.
1. Application of good electrical and mechanical design principles
First, the foundation of good EMC design is the application of good electrical and mechanical design principles. These include reliability considerations such as compliance with design specifications within acceptable tolerances, good assembly methods, and various testing techniques that are being developed.
Typically, the devices that drive today's electronic equipment are mounted on PCBs. These devices consist of components and circuits that are potential sources of interference and sensitive to electromagnetic energy. Therefore, PCB EMC design is the next problem in EMC design. The location of active components, the routing of printed lines, impedance matching, grounding design, and circuit filtering should all be considered in EMC design. Some PCB components also require shielding.
2. Connection of internal cables
Again, internal cables are generally used to connect PCBs or other internal subassemblies. Therefore, the internal cable EMC design including routing method and shielding is very important to the overall EMC of any given device.
After the EMC design of the PCB and the internal cable design are completed, special attention should be paid to the shielding design of the chassis and the treatment methods of all gaps, perforations and cable through holes.
3. Power supply and cable filter
Finally, input and output power supplies and other cable filtering issues should also be considered.
3. Protection design
Generally speaking, EMI protection is a systematic project, and EMI needs to be run through from the product design and development stage. However, due to various reasons, it is difficult for high-frequency lines to solve the EMI problem at the PCB design stage, and most of them need to shield the chassis to achieve the anti-EMI effect.
4. Absorbing magnetic ring
The ability of EMI absorbing magnetic rings/magnetic beads to absorb interference is characterized by their impedance characteristics. It presents a very low inductive impedance value in the low frequency band, which does not affect the transmission of useful signals on data lines or signal lines. In the high frequency band, starting from about 10MHz, the impedance increases, and its inductive reactance component remains small, but the resistive component rapidly increases, absorbing and dissipating the high frequency EMI interference energy in the form of heat energy. Usually, the resistance values at two key points of frequency 25MHz and 100MHz are used to calibrate the absorption characteristics of EMI absorbing magnetic rings/magnetic beads.
5. How to use
EMI absorbing magnetic ring EMI absorbing magnetic ring is often used to suppress interference on power lines and signal lines, and also has the ability to absorb electrostatic pulses.
1. Put it directly on one or a bunch of power and signal lines. In order to increase the interference and absorb energy, you can repeat it several times;
2. EMI magnetic ring with mounting clips, suitable for compensation type anti-interference suppression;
3. It can be conveniently clamped on the power line and signal line;
4. Flexible and reusable installation;
5. Self-contained clip-type fixation does not affect the overall image of the device.
6. Size selection
The greater the difference between the inner and outer diameters of the EMI absorbing magnetic ring, the greater the longitudinal height, and the greater its impedance, but the inner diameter of the magnetic ring must tightly wrap the cable to avoid magnetic flux leakage.
Seven, electromagnetic interference
Electromagnetic waves will interact with electronic components and cause interference, which is called EMI (Electromagnetic Interference). For example, the common 'snowflakes' on TV screens indicate that the received signal is being interfered with.