It is to protect the space between two regions of a barrier metal, to control the electric and magnetic fields and the electromagnetic waves and radiation induced by one region to another region. More precisely, the shield is surrounded by a set of component circuits, the interfering source, the cable or the whole system at the same time, to prevent the diffusion towards the outside of the electromagnetic fields; shielding with the receiving circuit, a device or system surrounded, to protect them from the outside effects of electromagnetic fields. Because the shielding against electromagnetic interference from electromagnetic waves from the outside and wires inside, cables, components, circuits or systems are the game of energy absorption (loss by eddy currents), l reflected energy (an electromagnetic wave reflected at the interface on the screen) and the offset energy (magnetic induction power generated in the opposite electromagnetic direction of the shielding layer, can be partially compensated by interference electromagnetic), and therefore have a shielding function against interference.
When high frequency electromagnetic fields, using a metallic drone jammer material of eddy current product low resistivity in the form of electromagnetic waves thwart foreign, to achieve the shielding effect.
When low frequency electromagnetic interference, the use of a material with high magnetic permeability, so that the magnetic flux confined inside the shielding to prevent the spread of the protected space.
In some cases, if the conditions required for high frequency and low electromagnetic fields have a good protective effect, often composed of multilayer metal shielding using different materials.
Many people do not understand the principle of electromagnetic shielding, as long as a metal box, the box is grounded, it can act as an electromagnetic shield. Under the leadership of this concept is the result of failure. Because the electromagnetic shielding and the shield to the ground or not does not matter. Only two factors that influence the actual effectiveness of the protective shielding: one shielding surface must be electrically conductive continuous and the other conductor does not directly penetrate the shielding. There are many points on a discontinuous conductive shield, the most important of which is a non-conductive space formed by different parts of the connection shield. The non-conductive deviation occurs from an electromagnetic leak, as fluid can leak from the same location on the container. One way to approach such a leak is filled in the space with the conductive elastic material, in order to eliminate the non-conductive point. This filling rubber as a fluid container in space for the same reason. Such a conductive filling material is an elastic electromagnetic seal.