The facts about Magnetic shielding
As well as being a commercial supplier we also like to share our knowledge for people who want to know. We have put together unbiased fact sheets for each of the products we supply.
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An unbiased data sheet
Magnetic sources generally come from large electric motors, sub station transformers or high tension (high voltage) cables, there are other sources such as large magnets and even the earth but the latter sources do not normally cause a problem for the environment.
Magnetic fields quickly decay in strength moving away from the source, this can be seen in a magnetic footprint diagram.
In some cases a high voltage sub station can be very close to a house or a particular room, in these cases the area is not safe for humans to be continually situated.
The method of shielding is to employ magnetic reluctance, that is, to construct a barrier where the magnetic field will flow easier in the shielding medium rather than in free air.
There are exotic materials that have good magnetic effect such as Mu metal but this is prohibitively expensive.
Other more cost effective materials like low carbon steel can be welded into a shield wall for good effect.
For D.C. shielding there are special electrical steels such as non-grain oriented low carbon steel, these are expensive.
Normally the area to be screened/shielded is measured by a probe in a grid like manner, the area is then re-tested after the shield installation using the same test method so that the effect of the shield can be demonstrated.
