Principle of low magnetic field shielding
In many cases, the components in electronic equipment will be affected by the surrounding magnetic field. When the frequency of the magnetic field is very low, the traditional shielding method is almost useless.
Therefore, low-frequency magnetic fields often have a serious impact on the normal operation of the equipment. Low-frequency magnetic fields are generally generated by motors, generators, transformers and other equipment. These magnetic fields
It will have an impact on equipment that uses a magnetic field. For example, the electron beam in a cathode ray tube is scanned under the control of a magnetic field. When there is interference from an external magnetic field,
The deflection of the electron beam will change, distorting the image. When the changing frequency of the external magnetic field is the same as the field scanning frequency, the image will only be distorted and deformed.
When the frequency of the magnetic field is different from the field scanning frequency, the image will roll. One of the effective ways to solve magnetic field interference is shielding.
The shielding of low-frequency magnetic fields uses ferromagnetic materials to wrap sensitive devices. The function of the shield is to provide a low magnetic resistance path for the magnetic field, so that the sensitive device is surrounded by
The surrounding magnetic field lines are concentrated in the shielding material, thus playing a shielding role. In order to provide a high shielding effect, the shielding material should have as high a permeability μ as possible.
The permeability of a material is not a constant quantity, it changes with the applied magnetic field, frequency, etc. Therefore, this kind of low frequency magnetic field shielding needs to provide a low magnetic resistance surface to complete.
The special shielding materials with high permeability of CO NETIC AA (μ=450000) and NETIC S3-6 (μ=4000) can achieve this purpose.