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. Ken Javor
Phone: (256) 650-5261 > From: Derek Walton <[email protected]> > Date: Wed, 13 May 2009 09:24:12 -0500 > To: John Woodgate <[email protected]> > Cc: IEEE EMC Discussion Group <[email protected]> > Subject: Re: Dimmer Switch > > Hi John, > > not deeply philosophical at all. In fact MIL testers are well aware of > this: it is SA 101. > > By harmonically rich I am agreeing that the signal measured contains > gazillions of frequencies all at once... The point specifically is when > you look at the SA screen, people interpret the signal displayed as > harmonics.... some even want to note the frequencies! > > The 90% observation is from assessing 100+ labs, and entertaining > clients daily in my test lab.. It is a basic lack of understanding of > whats happening, once explained, people follow... > > Now do you follow? > > Cheers, > > Derek. > > > > > John Woodgate wrote: >> In message <[email protected]>, dated Wed, 13 May 2009, Derek >> Walton <[email protected]> writes: >> >>> I was choice in my words by saying harmonic rich.... >> >> .... several lines down. >>> >>> Whats misleading is describing a time domain event on a SA as >>> harmonic. 90% of the folks I talk to do not comprehend that the line >>> on the emissions plot represents the instant an event occurs and not >>> a discrete frequency that could be remeasured at that point. >> >> Could there be another explanation for the 90% contrary opinion? At >> the least, your point is a deep philosophical one, I think. >> >> I responded to your statement: >> >> Specifically I want to point out that the noise you see is NOT >> harmonics. >> >> It IS; the fact that with some settings of the SA you can't see the >> individual lines spaced at 50 or 60 Hz is another matter. > > - > ---------------------------------------------------------------- > 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]> - 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]>
