In message <[email protected]>, dated Tue, 11 Sep 2007, Doug Smith <[email protected]> writes:
>The results are surprising in the amplitude observed at 48 kHz. Go to >http://emcesd.com . The picture of the scope probe and fluorescent >light is the link to the article. Presumably the lamp manufacturer claims that the lamp meets CISPR 15/EN 55015? This points up the importance of 'measurement distance' in EMC. Limits for radiated interference are based on a standard distance between source and measuring antenna (although the measurements may be made at a different distance and 'referred' to the standard distance by applying a factor (often of doubtful accuracy, since everything is in the near field where true corrections for distance are complex in the extreme). Your measurements are all made much closer to the source that the standard distance. Also, you have looked at the electric field, but the emissions are probably substantially magnetic (because the dimensions of the lamp are very much smaller that the wavelength it is a very inefficient electric radiator), and many receivers in the low and medium frequency ranges have magnetic antennas. -- 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 ______________________________________________________________________
