Conformity Magazine - September 2008 - (Page 25)

EM phenomena that have been considered so far include: • Electrostatic discharge (ESD) • EM fields • Rated power frequency magnetic field • Low-frequency magnetic field • Fast transients • Surges (line-line and line-ground) • Conducted radio-frequency • Voltage dips • Voltage interruptions • Harmonics and inter-harmonic distortion of the AC mains waveform The current draft of the combined EMC performance and safety standard is still biased towards using the IEC 61000-4 series immunity test methods for safety engineering purposes. IEC 61000-1-2 [10] points out that these standards were developed assuming economic/technical compromises that took no account of safety risks and, unless modified, may not be suitable for safety engineering purposes. [15] and [16] show that traditional EMC performance testing methods are either unsuitable, or at least insufficient on their own, for achieving acceptable functional safety risks. They also show that the usual preoccupation of EMC engineers with increasing the immunity test level to provide a “margin of safety” (evident in [4]) is incorrect. Once the test levels are set to the worst-case levels that could arise in the EM environment, and allowance has been made for the measurement uncertainty, no extra “safety margin” is necessarily achieved by increasing the test level further. [17] and [18] discuss what is needed instead to do risk-based EMC for safety engineering purposes, based on suitable design techniques and their verification and validation by appropriate techniques, including (but not limited to) appropriate EMC testing. [17] and [18] indicate that, by following certain approaches to design and verification, it can sometimes be possible to significantly reduce the testing burden as far as safety is concerned, helping to save time and cost overall. However, this requires the development of an industry-wide understanding of how to do EMC design and verification for safety engineering purposes, and this will no doubt take some time to establish. A similar regime had to be developed from scratch for IEC 61508, and was substantially complete within 5 years, so it is not impossible. The Leading Source for EMI Shielding Reliable Board, Enclosure and Cable Solutions Printed Circuit Board Shielding Finger Stock Gaskets Conductive Elastomers Metalized Fabric Over Foam Microwave Absorbers FerriShield Ferrites Leader Tech is a world-leading innovator and U.S. manufacturer of EMI shielding products for circuit boards, electronic enclosures and interconnect cables. Our core products include standard and custom circuit board shields, beryllium copper ﬁngerstock gaskets, conductive elastomers, advanced RF absorber materials and EMI/RFI ferrites. FerriShield is now Leader Tech In addition to the world’s largest, in-stock assortment of cable-mounted ferrites, FerriShield customers now have access to a greatly expanded EMI Shielding product line, dramatically improved engineering support and an unrivaled customer service team. Board, Enclosure or Cable EMI Shielding problems? Leader Tech sales engineers are waiting for your call. 866.TECH.EMI (866.832.4364) | www.leadertechinc.com | 12420 Racetrack Road | Tampa, FL 33626 September 2008 Conformity 25 http://www.leadertechinc.com http://www.leadertechinc.com

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Conformity Magazine - September 2008 Contents Editor’s Note Commission Adopts Regulations for Internet-Based TRS Services Another Company Fined for Non-Compliance with HAC Requirements FCC Extends “Do-Not-Call” Registry Compliance Requirements Marketing Company Gets $1.4 Million Fine for Junk Faxes EU Commission Codifies Directive on TTE Market Competition EU Commission Releases Updated Standards List for the R&TTE Directive Updated Standards List for the “New” Low Voltage Directive Released New Standards List Released for the EU’s Machinery Directive The ESD Association: Voluntary Standards in Action ESD Open Forum Medical EMC Standards: Towards the 4th Edition of IEC 60601-1-2 iNARTE Informer Pre-Pulse Voltage in the HBM ESD Model Digital Interfaces and EMC Performance ESD Design Buyer’s Guide Product News Commission Publishes Updated Standards List for the EU’s Personal Protective Equipment Directive FDA Links “Human Factors” to Adverse Events with Medical Devices CPSC Actions in the News IEC Standards Update UL Standards Update Product Reviews Telcordia Standards Update From Our “You Can’t Make This Stuff Up” Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - September 2008

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