Conformity Magazine - August 2008 - (Page 26)

limit of 18°C for the safety of their staff, since condensate could form on the test equipment, the device under test, or other objects, and create an unexpected discharge path. ESD Generator The ESD specification for the generator has changed very slightly to specify the accuracy of the pulse. I would be surprised if any existing ESD test equipment currently used for ISO 10605:2001 could not meet the new 5% accuracy requirement, although proving this may be tiresome. The most obvious change is the reduction of the upper voltage requirement, a change that is, in fact, inconsistent with some of the test levels listed later in the standard that still suggest 25kV pulses. Although there is a caveat in the table as written in the standard that states “or as required in the test plan,” this is not as explicit as the previous editions. Consequently the generator specification is now slightly misleading. At first glance, anyone with a standard IEC 61000-4-2 specified generator would believe they could offer automotive ESD testing to ISO 10605. However, they may find themselves in trouble if the client requires a 15kV contact and/or 25kV air discharge (as many VM standards do when referencing ISO 10605). The most significant change, as far as both testing and product design is concerned, is the additional use of the 330Ω resistor in the human body model for the discharge network. This is easily missed at first glance, as 330Ω is the value used in the IEC 61000-4-2 standard and will be familiar to any EMC test service. But this is the first time it has been introduced in the automotive ESD standard. Resistor Network: 330 or 2000 To those used to IEC 61000-4-2 testing, it might seem a trivial issue, even sensible, to use a 330Ω in the human body model. But there are several significant problems with this change. The first problem is that it implies that existing testing is inadequate, since this significantly increases the discharge energy while shortening the applied pulse duration. The second problem is that it implies that there has always been something wrong with the premise of the original 2000Ω network (used since before 1994). Lastly, I believe it has been introduced due to errors in other VM testing standards (such as BMW’s, for example, a mistake propagated from their adoption of MG Rovers’ specification when they owned that marque). Instead of the VM’s correcting their mistake, it is being introduced into this standard. The new standard lists the reason for the use of 330Ω as being representative of a discharge from a metal object (such as a tool) to the item being tested (ESA or vehicle). However, it may be unclear to some why IEC 61000-4-2 does not use a 2000Ω for body-to-object, as it is suggesting is used in the automotive environment. The reason is actually simple. The 2000Ω is used in the automotive environment because the environment itself is isolated from the earth reference. Hence, although the charge on a car and ESA is similar to the earth potential, the discharge path is not direct to earth but via vehicle ground (usually chassis and battery 0V). As a consequence, the resistor network is increased to compensate. The original 330Ω used in IEC 61000-4-2 was developed to model human body discharge to earth referenced systems (e.g., domestic and commercial systems installed and primarily powered via an electrical mains network). Therefore, the only application environment where the 330Ω resistor model would be valid would be when the vehicle or ESA is connected directly to a mains referenced supply with ELECTRONICS Your One Stop Shop for EMI Suppression Experts in EMI Suppression products since 1985 • Elastomers • Wire Mesh • EMI/RFI Filters • Enclosures • Ferrite Beads • Airvent Panels and Cores • Windows • Inductive Components • Conductive Adhesives • Gaskets We find solutions for all EMC/EMI problems whether it be new designs, prototype quantities, or small or large production run quantities. From board level to cable assemblies to power entry, we have a shielding or suppression solution. Distributor for premium manufacturers including: • Fair-Rite Products Corp. • Leader Tech, Inc. • Power Dynamics, Inc. ISO Edition: Parameter Output Voltage Accuracy Rise Time Holding Time Network Capacitance Network Resistance DIS: 2007 Contact 2-8kV <5% 0 .7-1 .0ns 5 150pF or 330pF 330Ω/2000Ω Air 2-15kV Released: 2001 Contact 15kV Not Specified 0 .7-1 .0ns Not Specified 150pF or 330pF 2000Ω <=5ns Air 25kV Samples Available 408-330-5914 www.pscelex.com Online Ordering info@emailpsc.com Table 2: ESD generator parameters 2 Conformity AUGUSt 2008 http://www.pscelex.com http://www.pscelex.com

Table of Contents Feed for the Digital Edition of Conformity Magazine - August 2008

Conformity Magazine - August 2008 Contents Editor’s Note FCC Seeks Comment on Reauction of 700 MHz D Block Commission Cracks Down (Again!) on Junk Fax Marketer Canada Levies Fees for Public Safety Radio Spectrum FDA Issues Guidance on Medical Device Tracking Greenpeace Challenges Video Game Manufacturers The IEEE EMC Society: A Proud History of Accomplishments ESD Open Forum An Update on Changes to the Automotive ESD Standard, ISO 10605 Modeling of Radiated Electromagnetic Disturbances in Automotive Applications Design Issues in Automotive Radio Frequency Systems IEEE EMC Symposium IEEE 2008 Show Preview Exhibitors Buyer’s Guide Product News Most Eco-Friendly Companies Updated Standards List For the EU’s Pressure Equipment Directive Commission Issues Updated Standards List For Directive on Gas-Fired Appliances HHS Releases Fact Sheet on U.S. Imports from China Customs Agents Seize Holiday Lights IEEE PSES Symposium Set for October CPSC Actions in the News IEC Standards Update UL Standards Update Telcordia Standards Update From Our “You Can’t Make This Stuff Up” Department Looking Back: Items from Past Issues of Conformity Product Reviews Advertisers

Conformity Magazine - August 2008

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