I have successfully used small loops for performing "shielding effectiveness" measurements. They are ideal to locate weak spots or points in a seam or isolate the leakage from aperture areas. We then compared these readings to a final shielding effectiveness measurement for the entire chassis and found that on an empirical basis there was a reasonable correlation that the localized readings were typically always equal to or greater than the final measurement.
Ed Nakauchi EMI/EMC Consultant Principal Scientist Instrument Specialties, Inc. -----Original Message----- From: [email protected] [mailto:[email protected]]On Behalf Of Douglas C. Smith Sent: Tuesday, August 01, 2000 4:54 AM To: emc-pstc; SI-LIST Subject: Shielding Effectiveness - or when a dB is not a dB Hi All, Shielding effectiveness is normally measured using plane waves (relatively far from the source). This method of measurement for shielding effectivenes does not always correspond to the way a shielding material is used. It is especially true when shielding material is incorporated into small products, such as the new wave of wireless devices on the market. If you rely on shielding to keep different parts of a product from interfering with each other, correlation of specification to use is especially important. The August 2000 Technical Tidbit on http://www.dsmith.org (or http://emcesd.com) describes a simple method of shielding effectiveness measurement that can be easily done in the development laboratory. This measurement method can give a better measure of shielding effectiveness that industry standard measurement techniques when the shield is close to the source being shielded. Has anyone here who is into shielding used something like this method which uses magnetic field loops? Doug -- ----------------------------------------------------------- ___ _ Doug Smith \ / ) P.O. Box 1457 ========= Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-----( ) | o | Email: [email protected] \ _ / ] \ _ / Website: http://www.dsmith.org ----------------------------------------------------------- ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
