The indenting and markup make it a bit unclear who wrote what, but I must take issue with some of the post below: - I am currently a lab manager who has worked in the trenches for almost thirty years and still does about 10 days a month. I am also a US TAG and IEC SC62A committee member writing medical EMC standards. - At least five other members are regularly doing hands-on product testing of either their own or other peoples products. - A) Test houses may indeed have this knowledge, but as a test house they are not allowed to put words into the mouth of the manufacturer, who is ultimately responsible for the product compliance. - B) Yes indeed, the manufacturers should contribute, and indeed they do. Well over 80% of my committee are national representatives who work for a company in the medical electronics industry. When I joined the committee I was employed by a manufacturer. - C) Several standards committees do have good input from test equipment manufacturers. Of particular note is Mike Hopkins of Thermo-Voltek who is a major contributor to the transient interference committees. While I can speak to the state of British test houses, I will say that the committees that I have been involved with (ANSI and IEC) are anything but insensitive to commercial impacts. With respect, personal opinions of Brent DeWitt Redmond, WA
From: [email protected] [mailto:[email protected]]On Behalf Of [email protected] Sent: Sunday, August 21, 2005 10:51 AM To: [email protected]; [email protected] Subject: Re: RF Susceptibility: Sweep v/s spot check In a message dated 8/20/2005 4:18:48 PM GMT Daylight Time, [email protected] writes: The British Standards EMC committees have test houses very well represented. Two observations... First: Test houses are entities that commercially exist to evaluate products. It is unlikely that you will find somebody on a standards committee that works in a hands on position in that company. More than likely it's a more senior member, distant from the testing being done. Second: A test house only has limited use on a committee, from my experience: A) skills that evaluate where EMC is likely to be at risk are important. Test houses don't have this knowledge. B) product manufacturers who understand the commercial impact of introducing a test should help decide what to impose. C) The test equipment manufacturer should be a contributor. They can help decide when not to try to impose something that is impractical to build equipment for. Or, alternative ways to simulate a threat. D) Test Facilities, internal and external, can provide input such as what existing capability could be used.. or what factors may drive a test duration >from reasonable to unreasonable etc. I guess my point is John, that there may be too many British test house folks involved... and we need more people who can match the product evaluation to the threat! Before you ask for an example, here's one: In the EN world, we typically have a blanket field strength. eg 10 v/m. When evaluating the strength of high power transmitters against aircraft, transmitter databases, including classified ones, were searched and the threat to the Aircraft defined. Once this was done, a "skyline" was composed that Aircraft were tested to. What that meant was that only the necessary field strength was generated, and only problems likely to occur were "fixed". Heck, we even looked at Gating the signal to simulate rotating of an antenna. I have lost count of the times products have failed in my lab when a cable resonance has dipped them under the flat line spec limit. What is just plain silly is that this happens in regions where there is not EM threat! Nor does the cable influence get taken into account. The commercial impact to a responsible manufacturer is unnecessarily burdensome. What's frustrating is that standards committees are insensitive to such commercial impacts. If there is a test limit in a standard, then the "driver" for that limit should be in the standard: why is that unreasonable? Just for the record... I own a test lab, contract to a test equipment manufacturer, and I'm a Lab Assessor. What I don't do is manufacturer products, so you can see I'm not biased. Cheers, Derek Walton L F Research ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
