The shielding box generally uses high-conductivity materials as the shield, and the shield is grounded. It uses the shield body to generate the eddy current magnetic field in the opposite direction under the action of the high-frequency magnetic field and the original magnetic field to offset the original magnetic field to weaken the interference of the high-frequency magnetic field, and realize the electric field shielding due to the grounding of the shield body. The thickness of the shield does not need to be too large, and the skin depth and structural strength are the main considerations.
Surround the positively charged conductor with a complete metal shield. The negative charge equal to the charged conductor will be induced on the inside of the shield, and the positive charge equal to the charged conductor will appear on the outside. If the metal shield is grounded, then The positive charge on the outside will flow into the ground, and there will be no electric field on the outside, that is, the electric field of the positively charged conductor is shielded in the metal shield.
In order to reduce the coupling interference voltage of the alternating electric field to the sensitive circuit, a metal shield with good conductivity can be set between the interference source and the sensitive circuit, and the metal shield can be grounded. The coupling interference voltage of the alternating electric field to the sensitive circuit depends on the product of the alternating electric field voltage, the coupling capacitance and the ground resistance of the metal shield. As long as the metal shield is well grounded, the coupling interference voltage of the alternating electric field to the sensitive circuit can be reduced. The electric field shielding is mainly based on reflection, so the thickness of the shielding body does not need to be too large, and the structural strength is the main consideration.
Since the shielded box has lower radiation emission than the unshielded cable, it prevents the network transmission from being intercepted. The shielded network (shielded cables and components) can significantly reduce the electromagnetic energy radiation level that may be intercepted when entering the surrounding environment.