Electromagnetic shielding is manufactured from materials of high permeability that can interfere with magnetic flux bypasses to avoid interference with the protected circuit. Moreover, the alternating interference flux will form eddy currents in the conductive shielding layer, and the eddy currents will weaken the strength of the external magnetic field. Shielding layers made of materials such as iron and pimo have both functions and can cause the interfering magnetic field to lose its influence on the circuit. The weak current signal circuit near the power transformer shall be protected from magnetic field interference and may be shielded by iron and beryllium-Mo plates.
Although the instrument shell is made of iron plate, but in order to prevent the influence of external magnetic field, often in the table attached to a layer of magnetic shielding.
In electronic equipment, some parts need to be protected from external magnetic fields. To solve this problem, it is necessary to use ferromagnetic material made of a cover, the need to prevent interference parts in the inside, so that it and the external magnetic field isolation, can also be those radiation interference magnetic field components, so that it can not interfere with other parts. This method is called magnetic shielding and is shown on the right. Because the shield shell with iron magnetic resistance is very small, it provides a unobstructed magnetic circuit for external interference with the magnetic field, so that the magnetic field lines are short-circuited through the iron shell and no longer affect the shielded components inside.