JOURNAL OF MAGNETIC SHIELD CASE STUDIES

“Open Sesame!” vs. “Stop – Thief!”
Case #14781

A leading manufacturer of automatic door openers (the ones you might find at any supermarket entrance) received complaints about electromagnetic interference. In this particular situation, the problem was not from interference received by his system, but instead from interference that the door-opening sensor generated. The extremely sensitive coils of the anti-theft security tag sensing systems were receiving signals from the opener’s sensor, causing improper operation of the security system. Properly functioning security systems are obviously of primary importance in stores, so a fast, effective solution was essential.

As with many situations that require quick solutions, the customer’s first and judicious step was for its engineers to obtain a Magnetic Shielding Lab Kit. These engineers then discussed their unique problem with the experienced shielding engineers at Magnetic Shield Corporation and tested prototype solutions. The source of the interference was identified, and a wrap of 0.004” CO-NETIC AA Alloy Foil was applied around the component, successfully eliminating the interference. We immediately supplied additional quantities of the foil from the large inventories we maintain within our plant so that the solution could be applied quickly on production units.

The long-term solution is unique in that two different shielding forms are used. in some models, a CO-NETIC AA Alloy Foil strip with a special adhesive is applied during assembly. We furnish the strips pre-cut to the proper length and width, with special adhesive, and on Mylar carrier strip for easy handling. The assembler simply peels the strip from the carrier and wraps it in place. For other models, a custom stamped magnetic shield inserts into the circuit board, surrounding the problem component. This drawn part is supplied completely formed, annealed and with the specified paint finish. The solder tabs that insert into the circuit board are left bare, and the ready solderability of CO-NETIC AA Alloy permits the solder to accomplish grounding and mechanical retention functions.