Shiledmu Tape & Foil

There is no black magic required when selecting the power alloy for magnetic shielding at audio and power frequencies.

SHIELDMU gives the designer a full range of magnetic performance for construction of formed-in-place shields. ALL SHIELDMU types are available from stock in a number of thicknesses and widths for convenient application.


Shieldmu is carried in stock widths lengths wound on spools. When ordering, please use the part number indicated, each letter and digit is coded to indicate a specific requirement as shown in the example below:

Economical Shielding with Shieldmu Tape And Foil.

SHIELDMU tapes and foils are fully processed and ready to use; heat-treatment is not required after forming. Formed-in-place shields save time and expense when compared to fabrication of special shields. This is most important where experimental results are urgently required, or where small quantity needs make tooling cost uneconomical.


Estimating attenuation of SHIELDMU Tape & Foil

Attenuation is a function of the permeability of the metal in the shield, and its geometry. It is most conviently expressed in decibels (db),

db = 20 log

Where B1 is the field strength in the space outside the shield. B2 is the field strength inside the shield. Strengths of alternating-current fields are usually measured with a vacuum tube voltmeter and a search coil, or an existing winding on the component to be protected, i.e., a transformer or inductor. Static fields of permanent magnets, direct-current devices, or the earth's field may be measured with Hall probes or magnetometers.
Attenuation is sometimes expressed in percent. 

Use Calculator here:
7 8 9 /
4 5 6 *
1 2 3 -
0 +/- . +


Practical Considerations

The development of the best magnetic permeability (shielding ability) by proper annealing makes these high performance magnetic alloys ductile and subject to work-hardenning (drilling, bending, hammering or dropping), by actual test measurement, lowers the permeability and thus the shielding ability. Form a practical viewpoint, this lowering of the permeability must be viewed against the level of shielding required for the particular application. If the permeability is changed by a factor of two, the attenuation changes by six decibels. This may or may not be significant in a particular application.

Selecting SHIELDMU

Shieldmu is provided in three levels of permeability performance. Each is designed to meet the specific requirements of various shielding applications. Multi-layer shields using different materials often give the most economical result by putting high flux capability materials in the region of the strongest field. The high permeability layers are then most effective at the lower field strengths.


Shieldmu is now being used to provide formed-in-place magnetic shielding of components. Shieldmu is used for production quantities, prototypes and for laboratory experiments. Tooling, with its high cost and long delivery, is not necessary. Shieldmu, in stock, offers an economical, fast way to investigate the performance of combinations of materials and thicknesses. A few of the typical applications are for shielding of:
Transformers, Cathode Ray Tubes, Tachometers, Microphones, Magnetic Tape Reels, Vacuum tubes, instruments, cables (current-carrying conductors), photomultiplier tubes, meters, reed relays, storage & display tubes, electrical wave filters, magnetrons, traveling wave tubes,  shielded rooms, motors, transistors, relays, recording heads...





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This Page was last modified on Wednesday, March 27, 2002 .