Conformity Magazine - August 2008 - (Page 27)

earth connection and approached over an insulating surface (to gather charge) by someone holding a non-insulated metal tool (e.g., a wrench). I’m not sure how many car assembly lines or garage workshops were visited by the ISO committee members who allowed this resistor value change, but they must be very different from the ones that I’ve been around. In any event, I have come to the personal conclusion that, in reality, there are almost no cases where this application scenario is valid; as such, this change to the 330Ω resistor network is effectively redundant in the automotive environment. Functional Performance Status Classification Functional performance status classification (FPSC) is a new annex to the standard (an informative annex), and is a useful addition to the text. It effectively incorporates most of what was implied in the 2001 edition that using references to ISO failure mode severity classifications, but applies them more logically. What the existing severity classification B implies is that a product could exceed its maximum parametric performance during exposure, but it leaves unanswered the question of how would you detect this during testing. As a consequence the current ISO class B classification is redundant for ESD test classification. Effectively though, instead of just using the existing ISO classes A, C, D and E, the classes have been relabelled in ISO 10605 as Status I, II, III and IV, and are effectively unaltered in their descriptive form. The critical difference is that the tests are being applied to functions on the ESA, not just the ESA as a whole. This might at first be difficult to perceive, but most ESAs these days have multiple outputs with different functional implications. Hence, simple on/off signals, which may include interior switches or illumination lights and some exterior lights, some data bus communications and others, may be analog signals. The FPSC allows the severity level and status of the individual signal function to be specified, rather than of the ESA as a whole. Hence, maybe some on/off data should be Status I under all conditions, but some analog functions (say RF reception) and on/off signals for interior lighting may be allowed to be compromised during a high severity event (Status II). Anyone familiar with Daimler-Chrysler standards will recognize some of this and, as a designer or producer, it makes sense and can allow some cost reductions on non-critical functions within a multi-function module or ESA. However, I expect it may cause some headaches to the test houses, and that it will be more difficult to give a clean “pass” or “fail” as is possible with the current standard. The wording of this annex could also be a little more clear; initially, it looks like a specific number of fails can be tolerated, but this is not the intention. Additionally, the examples show three categories of test level, but this is not introduced in the text, and there is no explanation of what the categories are. I believe these are intended to show various categories of devices and, hence, test severity. For example, category 1 may be a non-safety device, such as an in-car entertainment (ICE) system, and category 3 may be a safety critical function, such as engine control module (ECM). The text does state users may group functions into categories, but it does not make suggestions of what these categories might be, how many might be specified, and what test severity is appropriate (although the examples imply the later at least). Exclusion of Pyrotechnic Modules One classification of device that is specifically excluded from the updated standard is pyrotechnic devices. Personally, I find this strange since, of all the products that you do not want to react to a user-borne ESD event, one would expect air bags to be number one. This is not excluded in an annex, but in the scope at the start of the document, even though one of the pictures in the annexes for on-vehicle testing shows discharge to the steering wheel. (I guess you wouldn’t want the horn to sound inadvertently while you are trying to disentangle the air-bag from your face.) Calibration The method for calibrating the ESD generator is very well documented, and a specific 2Ω target is suggested with construction details. There is also a 50Ω conical line adaptor AUGUSt 2008 Conformity 27 http://www.okaya.com http://www.okaya.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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