As I recall, this topic came up once before on this forum. But try as I might, I'm unable to find any notes on it.
The idea, as I remember, was you test a single DUT, and then add another, and another, until emissions do not increase appreciably or become asymptotic with enough margin to the limit. This idea had "N+1" in the title. I have studied multiple noise sources in the context of audio white noise from cooling fans (up to 14 at a time) and the noise increase is approximated by the RSS (root-sum-square) function. However RF EMC can be very different because often the emissions are very narrow band and sometimes synchronous, or 100% additive. I would appreciate anyone pointing me in the right direction on what the rules actually are. Best regards, Doug Douglas E Powell Laporte, Colorado USA On Fri, Feb 17, 2023, 7:56 PM Ken Javor <ken.ja...@emccompliance.com> wrote: > I’m finding this an extremely interesting discussion. I don’t have > anything definitive to offer, but I do have a question to help stir the pot. > > If the possibility that multiple items might be used together and that > emissions will be additive in some fashion is a justification for testing > multiple units at a time, what about ... light bulbs? > > Meaning CFLs or LEDs. > > My house is full of them. It is reasonable to assume that most > homes/businesses are. Perhaps the emissions limits for these were based on > this reasonably foreseeable outcome? > > Ken Javor > Phone: (256) 650-5261 > > > ------------------------------ > *From: *John Mcbain <johnmcb...@ieee.org> > *Reply-To: *John Mcbain <johnmcb...@ieee.org> > *Date: *Fri, 17 Feb 2023 14:22:44 -0800 > *To: *<EMC-PSTC@LISTSERV.IEEE.ORG> > *Subject: *Re: [PSES] Adding more than one EUT > > Hi Derek - > > Typical requirement for a unit that may be sold and used in multiples > (that is, all the units can be sold together as one product) is you can > test just one IF adding the other units does not increase the emissions. > > Of course the most practical way to determine that is to assemble the > multiple units to see what happens. If the test result for testing max. > connected units compared to testing only one unit shows no significant > difference, then you're good - but definitely archive those test results! > > If you can't pass the test with all units connected, then whatever you do, > don't let Marketing create a multiple-unit product to sell. ;-) > > Similarly, the desktop PC system that James mentioned would have all power > cords separately tested for conducted emissions as a fully connected system > (monitor, printer, scanner, etc. attached) if it is a product sold as a > complete all-included system. > > Best regards, > John McBain > > > On Fri, Feb 17, 2023 at 1:59 PM James Pawson (U3C) < > ja...@unit3compliance.co.uk> wrote: > > > Hi Derek, > > > Is the daisy chain connection the AC supply or some other power bus? > > > How is 8 units daisy chained any different to 8 separate units all on the > same power bus? We are looking for individual emission contributions from > each connected unit. > > > If measuring conducted emissions on a desktop pc (y'know, the big ones we > had before everyone had laptops to work from home...) the you would just > measure the PC, not the monitor and printer and scanner and modem and and > and... > > > Just thinking aloud > > All the best > > James > > > ---- Lfresearch wrote ---- > > Hi folks, > > > > I’ve been asked to test a light fixture that has the ability to be daisy > chained up to 8 units. > > > > When I run conducted emissions, I’m wondering if I need to insist on > having 8 units plugged in at once i.e. fully populated, OR, can I just test > one fixture at a time since that’s how the system is likely to be used > also.. > > > > Is there a legal requirement or precedent on how this should be tested as > I’m going round in circles arguing with myself here. > > > > Thanks, > > > > Derek. > > > > SSCLabs, > > Reno, NV. > > - > > ---------------------------------------------------------------- > > 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 < > emc-p...@ieee.org> > > > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieee-pses.org/emc-pstc.html > > > > Website: http://www.ieee-pses.org/ > > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) > > List rules: http://www.ieee-pses.org/listrules.html > > > > For help, send mail to the list administrators: > > Mike Cantwell <mcantw...@ieee.org> > > > > For policy questions, send mail to: > > Jim Bacher: <j.bac...@ieee.org> > > David Heald: <dhe...@gmail.com> > > _________________________________________________ > > To unsubscribe from the EMC-PSTC list, click the following link: > https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1 > > - > ---------------------------------------------------------------- > > 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 < > emc-p...@ieee.org> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Website: http://www.ieee-pses.org/ > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org> > David Heald <dhe...@gmail.com> > ------------------------------ > > To unsubscribe from the EMC-PSTC list, click the following link: > https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1 > > - > ---------------------------------------------------------------- > > 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 < > emc-p...@ieee.org> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Website: http://www.ieee-pses.org/ > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org> > David Heald <dhe...@gmail.com> > ------------------------------ > > To unsubscribe from the EMC-PSTC list, click the following link: > https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1 > > - > ---------------------------------------------------------------- > > 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 < > emc-p...@ieee.org> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Website: http://www.ieee-pses.org/ > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org> > David Heald <dhe...@gmail.com> > ------------------------------ > > To unsubscribe from the EMC-PSTC list, click the following link: > https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1 > - ---------------------------------------------------------------- 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 <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com> _________________________________________________ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
