Concept and classification of EMI shielding room

1. Concept of shielding
The methods and measures taken to prevent mutual induction of static electricity, magnetic field, and fire electromagnetic field are called shielding. Its purpose is to limit the electromagnetic interference generated by electronic equipment or electronic components to a certain area or protect electromagnetic sensitive equipment from external electromagnetic interference.
2. Basic classification of shielding
1) Electrostatic shielding
Electrostatic shielding prevents electrostatic coupling interference, which refers to the shielding of the electrostatic field, that is, using low-resistivity conductor materials to make containers, limiting the power lines inside the container, and preventing external power lines from entering the container. In electrostatic shielding, the shielding conductor must be grounded, and the shielding body and the grounding wire are both metal materials with good conductivity.
2) Electromagnetic shielding
Electromagnetic shielding prevents high-level electromagnetic wave interference and is used to suppress interference generated by electromagnetic field coupling when the noise source and sensitive equipment are far apart. Electromagnetic shielding must shield both electric and magnetic fields, and usually uses low-resistivity conductor materials. When space electromagnetic waves are projected onto the surface of a metal body, reflection loss and absorption loss will occur, which greatly attenuates the electromagnetic energy, thereby achieving the purpose of shielding. In electromagnetic shielding, the shielding body itself may not be grounded, but in order to avoid electrostatic coupling, the electromagnetic shielding conductor is generally grounded.
3) Magnetic shielding
Magnetic shielding is to prevent low-frequency magnetic field induction. Shielding is more difficult. Usually, metal materials with high magnetic permeability and low resistivity are used to form a shell with a certain thickness, so as to limit the magnetic lines of force to the inside of the shielding body with low magnetic resistance and prevent the diffusion of the magnetic field. This is the basic principle of magnetic shielding. Similar to electromagnetic shielding, in magnetic shielding, whether the shielding body is grounded does not affect the shielding effectiveness. In order to prevent electrostatic induction, the actual structure is generally connected to the housing (safe grounding).