Frequently Asked Questions

Magnetic Shield Corporation has spent 60 years specializing in creating solutions to problems related to electromagnetic interference (EMI). Our shields have been to outer space in the Explorer IV satellites used to discover the Van Allen Belts. Closer to home they are aboard US Navy submarines, shielding navigation systems. Shields are used in everyday applications such as heart monitors, cellular phones, credit card and check readers, automobiles and "smart house" control networks... anywhere electronics can be affected by EMI.

Here is Part Two of our series answering the most frequently asked questions concerning EMI.

What is ELF

ELF stands for Extremely Low Frequency and usually refers to magnetic fields at 0.5 to 100 Hertz. This range includes the 60 Hertz power line frequency commonly used in the United States. In other countries, the power line frequency might be 50 Hertz.

How does magnetic shielding work?

All shielding materials work by diverting the magnetic flux to themselves. Although the field from a magnet will be greatly reduced by a shield plate, the shield plate will itself be attracted to the magnet. Closed shapes are the most efficient for magnetic shielding cylinders with caps, boxes with covers and similar enclosed shapes are the most effective. Magnetic shielding materials offer a very high permeability path for magnetic field lines, directing the magnetic field lines through the thickness of the alloy, and keeping them from going where they are not wanted. It is important that the shield offers a complete path for the field lines, so that they do not exit the material in a place where they will cause unintended interference.

What blocks magnetic fields?

Nothing - there is no known material that blocks magnetic fields without itself being attracted. Magnetic fields can only be redirected using high permeability shielding alloys. The magnetic field lines are strongly attracted into the shielding material.

How do I solve a magnetic shielding problem?

Shield calculation formulas do exist, but are usually valid only for theoretical conditions of closed shield shapes and well-described interference fields. Many magnetic shielding problems are solved by prototyping a shield. This procedure allows you to immediately see the results of the shielding in the item under test and the opportunity to optimize the shield's thickness and shape.

Record Growth Presents New Challenges

Despite an overall economy that has been less than stellar, the last two years have been very strong ones for Magnetic Shield Corporation. In the year 2000, we set a company growth record by increasing our sales by 40%. We continued this trend by setting an even higher sales record for 2001.

Our growth can be tied to the expansion of electronics, which has resulted in a constant flow of new applications, creating new customers - and business - for us. Of course we thank you, our customers, for your support, and we will work even harder in the future to maintain and earn that support.

Throughout this issue of Magnetic Shield Update, you will find examples of how we utilize our 60 years of experience to create innovative solutions to electromagnetic interference problems in wide-ranging applications. Feel free to contact us with your special need - we're waiting to assist you.