The signals shielded by the shielding box are also divided into many types, among them there is the shielding of high and low frequency magnetic fields. Do you all know about these? The specific related knowledge, you may not know too much, but it doesn’t matter, I will explain it in detail today. Tell me about the relevant information about low-frequency magnetic field shielding. The detailed knowledge of low-frequency magnetic field is as follows:
The low-frequency magnetic field is actually similar to the basic principle of electromagnetic shielding. Due to its low frequency, the skin effect is very small, and the absorption loss is very small. And because its wave impedance is very low, the reflection loss is also very small, so it relies solely on absorption and reflection. It is difficult to obtain the required shielding effectiveness. For this low-frequency magnetic field, shielding is achieved by using high permeability materials to provide a magnetic bypass.
Due to the high magnetic permeability of the shielding material, it provides a path with low magnetic resistance for the magnetic field. Therefore, the magnetic field in the space will be concentrated in the shielding material, so that the sensitive device is protected from the magnetic field. From the perspective of this mechanism, it is obvious that the more magnetic field components shunt by the shielding body, the higher the shielding effectiveness. According to this principle, we can use the calculation method of the circuit to calculate the magnetic shielding effect.
When using a magnetic shield, the higher the permeability of the magnetic shielding material, the thicker the shield, the smaller the magnetic resistance and the better the shielding effect; when making the magnetic shield, the opening or gap should not cut the magnetic line of induction, otherwise it will Increase the magnetic resistance and reduce the shielding effect; the magnetic material cannot shield the high-frequency magnetic field, because the magnetic loss of the magnetic material is very large at high frequency, which leads to the decrease of the magnetic permeability.
In fact, the shielding effect has a very important relationship with the shielding material and the magnetic field. And if you want to know the final information of the shielding effect, you can calculate the shielding result through the calculation method of the circuit.