How to do magnetic shielding

How to do magnetic shielding

In practical work (for example, accurately measuring certain magnetic fields), it is often necessary to eliminate the interference of external magnetic fields, so some parts of the space need to be shielded. The closed shell made of ferromagnetic material can conduct magnetic shielding. This system can be regarded as a parallel magnetic circuit consisting of closed shell and cavity inside the shell. Obviously, the magnetoresistance of the shell made of ferromagnetic material is much smaller than that of the cavity composed of air. According to the inverse ratio of magnetic flux to magnetoresistance in parallel magnetoresistance, the magnetic energy (and magnetic induction intensity) in the cavity is far less than the magnetic flux (or magnetic induction intensity) in the shell.
It
The magnetic induction intensity in the cavity of a ferromagnetic shell is not zero, which is different from that in a closed conductor cavity. Therefore, the effect of magnetic shielding is far less than that of electrostatic shielding. In order to achieve better magnetic shielding, the shell should be made thick enough or screened in many layers besides the materials with high magnetic conductivity.