Hi All, I think that I would describe it as the following,
Every t=1/50 seconds current flows and this has a fast rise time. The net effect is a comb occurring in the frequency domain every 50Hz, however, this comb only appears every 1/50 (=20)ms. If the sweep is, say 20ms for the whole screen - then one, possibly 2 of these time domain events will show on the screen. In order to correctly display this type of signal, the sweep time should be slowed and the frequency range adjusted until each 50Hz element is displayed. A quick answer to something that could take a lot of explaining - may mean that there are limitations to the answer! Regards Tim (Off home now) ************************ Tim Haynes A1N10 Electromagnetic Engineering Specialist SELEX Sensors and Airborne Systems 300 Capability Green Luton LU1 3PG ( Tel : +44 (0)1582 886239 7 Fax : +44 (0)1582 795863 ) Mob : +44 (0)7703 559 310 * E-mail : [email protected] P Please consider the environment before printing this email. There are 10 types of people in the world-those who understand binary and those who don't. J. Paxman From: [email protected] [mailto:[email protected]] On Behalf Of Derek Walton Sent: 13 May 2009 16:04 To: John Woodgate Cc: [email protected] Subject: Re: Dimmer Switch *** WARNING *** This message has originated outside your organisation, either from an external partner or the Global Internet. Keep this in mind if you answer this message. I think you are missing th point John, I'm not saying harmonics aren't there: I've stressed harmonic rich as much as I can..... It's all down to what you see on the display of the SA, and thats sweep time dependent. Ken describes that well. The lines that appear on the display are spaced on sweep time not frequency. It would be useful to show graphs on the group! Cheers, Derek. John Woodgate wrote: > In message <c630442d.4265c%[email protected]>, dated Wed, 13 > May 2009, Ken Javor <[email protected]> writes: > >> Have to admit to being confused by the Woodgate-Walton discussion. >> The way I see it, the dimmer switch is indeed generating a harmonic >> rich signal. The spectrum analyzer, due to the required EMC >> bandwidths, doesn't show each individual harmonic - the bandwidth is >> wider than the harmonic spacing. Therefore the dimmer switch is >> creating what appears to be broadband noise, as long as your >> reference point is audio frequency bandwidths necessary for radio >> communications, and by extension EMI measurements. > > I agree. The harmonics are there, whatever you can or can't see on the > SA display. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ 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]> SELEX Sensors and Airborne Systems Limited Registered Office: Sigma House, Christopher Martin Road, Basildon, Essex SS14 3EL A company registered in England & Wales. Company no. 02426132 ******************************************************************** This email and any attachments are confidential to the intended recipient and may also be privileged. If you are not the intended recipient please delete it from your system and notify the sender. You should not copy it or use it for any purpose nor disclose or distribute its contents to any other person. ******************************************************************** - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ 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]>
