Magnetic ShieldsOctober 29th Fact-of-the-Day
Non-magnetic, electrically-conducting shields are not effective in shielding unidirectional or low-frequency magnetic fields, because their magnetic shielding properties depend on eddy currents induced by rapidly changing magnetic flux. However, unidirectional and low-frequency magnetic fields can be shielded by shields made of magnetic material, preferably material having high initial permeability. The degree of shielding provided depends upon the size and thickness of the shield and whether it consists of a single layer or multiple concentric layers separated by air spaces. Multiple, concentric, air-spaced layers are much more effective than the same volume of shielding material in a single layer. ©2004 Martek International All rights reserved.
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