Just because... some standard lab techniques is record the environment conditions at the time of the test. Remember chemistry labs in school. Now outside of EMC, other lab tests get concerned, for example harddrive heads use air to "fly" over the media. High altitudes with less air pressure contribute to head crashes. Air pressure and density relate to cooling and fans moving the air. The telcom test world has/had a requirement of one of the tests to be done at a pressure 200 feet below sealevel. That increase is about a really good sunny high pressure day amount. And on low pressure days, the techs get sinus headaches and fail your system.
John Woodgate <[email protected]> wrote: In message <[email protected]>, dated Mon, 31 Mar 2008, Derek Walton writes: >I asked the same question... The only one I can think of is ESD, but >that doesn't tell me why. More importantly, what evidence is there >documenting the effects? It's an easy question to ask, but impossible to answer. The standards have to apply to ALL products, and no standards committee knows everything about every product. > >I think, until facts are published, confirmed and quantified, that the >Standards body is shotgunning environmental requirements. The possibility to delete the air pressure requirement has been debated within living memory. No-one seem to know of a case where it matters [1], but there COULD be some, and the Certainty Principle indicates that if there is one, a failure to take pressure into account will result in a major problem (i.e. $$$$$) one day. > >What on earth is the value of recording something if all it is is >documented? I doubt few people if anyone will ever pay any notice. .... until a critical product and phenomenon are discovered. Then the magazine articles about it will come thick and fast. > >It's all just adding cost to testing. Since probably all of the EMC standards committees have equipment manufacturers' experts in the majority, adding cost to testing is always a no-no. [1] For example, an airtight shielding enclosure might flex under unusually low or high external pressure and either not remain an integral shield or foul something internal or external that compromises immunity. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Murphy's Law has now been officially re-named The Certainty Principle John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - 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/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: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - Bill You can say what you want about the South, but you never hear of anyone retiring and moving North!!! _____ OMG, Sweet deal for Yahoo! users/friends: Get A Month of Blockbuster Total Access, No Cost. <http://us.rd.yahoo.co /evt=47520/*http://tc.deals.yahoo.com/tc/blockbuster/text2.com> W00t - ---------------------------------------------------------------- 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/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: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
