- Aug 08, 2017 -
There are three main ways to suppress electromagnetic interference: shielding, filtering and grounding.
Shield: is used to reduce the electromagnetic field outward or inward penetration of the measures, commonly used in isolation and attenuation of radiation interference. Shielding according to its principle is divided into electrostatic shielding, electromagnetic shielding and magnetic shielding three. The role of electrostatic shielding is to eliminate the two circuits due to distributed capacitance coupling generated by electromagnetic interference, the shield is made of low resistance metal material, the shield must be grounded. The role of electromagnetic shielding is to prevent the interference of high-frequency electromagnetic field, the shield is made of low-resistance metal material, the use of shielding metal on the electromagnetic field absorption and reflection to achieve the purpose of shielding. The role of magnetic shielding is to prevent the interference of low-frequency magnetic field, the shield using high permeability, high saturation magnetic materials to absorb or loss of electromagnetic field to achieve the purpose of shielding.
The influence of electromagnetic interference is very close to the distance, the closer to the interference source, the greater the interference field strength, the greater the impact. In electronic instrumentation, the layout of electronic components is often limited by the size of the use of low-resistance metal materials or magnetic materials made of closed body, the protection of the gap between the components or parts isolated to reduce or prevent static or electromagnetic interference.
Filter: can inhibit the electromagnetic interference. Sensitive electronic equipment through the power line, telephone lines, control lines, signal lines, such as electromagnetic interference signal transmission. For conduction interference often use low-pass filter, can be effectively suppressed. However, in the design of electromagnetic compatibility, we must consider the characteristics of the filter: frequency characteristics, impedance characteristics, rated voltage and voltage loss, rated current, leakage current, insulation resistance, temperature, reliability, size and so on.
Grounding: In the equipment or device, the grounding is to make the equipment or device itself generated by the interference of current through the ground into the earth, commonly used in the suppression of conduction interference. The ideal grounding body is a zero-potential, zero-impedance physical entity that acts as a reference point for all signal levels in the associated circuit, and no unwanted current through it produces no voltage drop. This ideal grounded entity is actually similar.