In message <c4cd5f6946aa5142a638e43997531f1b04311...@ukltnexch02.uk.htplc.grp>, dated Fri, 7 Sep 2007, Paul Lovell <[email protected]> writes:
>On a slightly different track, what about the thermal effects of >altitude? 60950-1 and 60601-1 are deemed to 'work' up to 2000m >elevation, 60065 as well. >but most of the labs (I would assume) are at, or close to, sea level. >However, it's well known (in the NEBS world at least) that the thinning >of the air will lead to increased internal temperatures at a rate of >approx 1C per 500m elevation, so a device running in a 25C ambient will >be about 4C hotter inside (ie windings etc) at 2000m than at sea level. Yes, but the ambient temperatures are lower at higher altitudes (out of direct sunlight exposure). > I've wondered for some time why the safety standards don't take this >into account although they make allowances for minimum clearance >distances at higher altitude. Insufficient data that indicates a need? > >Is this just an error of omission or is the effect too small to be >significant? I remember in my BSI Testing days that we would >occasionally have products which only just passed the heating test >without considering the effect this might have at 2000m: it just wasn't >'on the radar'. Well, 6500 foot mountains aren't on the BSI radar! It would be up to countries that have high mountains or plateaux (USA, Mexico, China, Tibet, India, central Africa) to make proposals if safety issues arise that are due to altitude. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. 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 ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
