Hi John, I did not see much magnetic field. I put a loop of a few feet in diameter in several orientations around the lamp, but saw nothing. I justified this in that there are probably high voltage pulses in the lamp but I did not spend much time looking for magnetic fields other than to note my loop did not pick up anything I could see on the scope >from a foot or two away.
Doug John Woodgate wrote: > 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. -- ___ _ Doug Smith \ / ) P.O. Box 1457 ========= Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-----( ) | o | Email: [email protected] \ _ / ] \ _ / Website: http://www.dsmith.org - 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 ______________________________________________________________________
