The point of the cm vs. dm discussion is that the effect of LISN impedance is not so important for dm as for cm, speaking very generally, so that the effect of uncertainty in LISN impedance on dm emissions is less than for cm. But we don't separately measure cm and dm, so we don't know, looking at any specific signal, what the uncertainty is, even if we have nailed down the uncertainty of the LISN impedance. And you don't need two LISNs to separate modes, but that is another discussion.
Ken Javor Phone: (256) 650-5261 > From: Ralph McDiarmid <ralph.mcdiar...@schneider-electric.com> > Reply-To: Ralph McDiarmid <ralph.mcdiar...@schneider-electric.com> > Date: Mon, 11 Sep 2017 22:32:14 +0000 > To: <EMC-PSTC@LISTSERV.IEEE.ORG> > Conversation: [PSES] LISN Calibration Measurement Uncertainty > Subject: Re: [PSES] LISN Calibration Measurement Uncertainty > > Sorry, I guess we drifted a little off topic, and that's my fault. If you > want to characterize a LISN for the purpose of defining an measurement > "uncertainty budget" then I suppose all that is needed is a carefully written > test procedure. I doubt a Network Analyzer is required, I think a signal > generator and a scope would suffice. > > What parameter of a LISN matters for determining its measurement uncertainty? > I can only think of the impedance "seen" the DUT. As the impedance gradually > moves away from the ideal 50 ohm resistive, then I think less signal reaches > the EMI receiver, and that is the "uncertainty" or maybe error is a better > term. I really cannot see how CM vs DM comes into play at all; the LISN > measures both as far as I know, so one cannot separate the two, without using > a second LISN connected to a second power pole of the DUT. I think save to > say that most DUTs will have a least two power poles, a "line" and a "neutral > for connection to the a.c. mains. > > I think some manufactures provide a graph or two plotting something (perhaps > insertion loss versus frequency) for that serial number. > > I hope that helped a little. > > Ralph McDiarmid > Product Compliance > Engineering > Solar Business > Schneider Electric > > > -----Original Message----- > From: John Woodgate [mailto:jmw1...@btinternet.com] > Sent: Monday, September 11, 2017 1:28 PM > To: Ralph McDiarmid <ralph.mcdiar...@schneider-electric.com>; > EMC-PSTC@LISTSERV.IEEE.ORG > Subject: RE: [PSES] LISN Calibration Measurement Uncertainty > > It's not quite as simple as it may appear. Mr Javor points out that it > measures two mixtures of DM and CM voltages, which is not helpful either in > fixing a design or in determining the consequent radiated emission (due to the > CM component alone). > > The 50 ohms is indeed the input resistance of the SA. But it's not necessarily > (not likely to be) the impedance looking back down the mains lead to the EUT. > All it does is to help produce consistent results, it doesn't do anything to > help the results to be representative of real world conditions. > > With best wishes DESIGN IT IN! OOO - Own Opinions Only www.jmwa.demon.co.uk J > M Woodgate and Associates Rayleigh England > > UK is a sovereignty, not a Zollverein-ty > > -----Original Message----- > From: Ralph McDiarmid [mailto:ralph.mcdiar...@schneider-electric.com] > Sent: Monday, September 11, 2017 7:33 PM > To: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] LISN Calibration Measurement Uncertainty > > My understanding: > > A LISN seems to be a simple device, which has three ports: an input, an > output, and a sense port. The sense port connects to the spectrum analyzer or > EMI receiver, with the input port connecting to mains, and the output port > connecting to the power terminals of the device under test (DUT). > > What impedance is important? I assume it is that impedance which is "seen" > by the DUT when it is connected to the output port of the LISN. I think it is > that impedance which is 'stabilized' over a given bandwidth for the purpose of > a repeatable measurement environment. > > When we talk about a "50 ohm LISN", isn't it the EMI receiver that provides > the 50 ohms? Both above and below the design bandwidth of the LISN (AMN), > there will be reactance (inductive or capacitive) that begins to affect the > impedance seen by the DUT, which moves the load impedance further away from > the ideal 50 ohms. > > > Ralph McDiarmid > Product Compliance > Engineering > Solar Business > Schneider Electric > > > From: Ken Javor [mailto:ken.ja...@emccompliance.com] > Sent: Monday, September 11, 2017 10:21 AM > To: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] LISN Calibration Measurement Uncertainty > > Off-topic response. Grinding an axe. Clearly the network analyzer itself > serves as a limit on the achievable uncertainty, but it should be much better > than what is needed (+/-20% in the military world). That aside, consider that > differential mode emissions tend to be low impedance relative to that of the > LISN, and therefore act as voltage sources, whose amplitude doesn't correspond > much to changes in LISN amplitude. Common mode emissions tend to be current > sources and therefore common mode emission amplitudes track closely with > changes in LISN impedance. But we don't measure these modes separately, but > rather as vector sums on the phase conductor, and vector differences on > neutral, so we have no idea what the effect of the LISN impedance on any > particular emission measured actually is. > > Ken Javor > Phone: (256) 650-5261 > > ________________________________________ > From: Mac Elliott <mailto:00000a115b29e815-dmarc-requ...@ieee.org> > Reply-To: Mac Elliott <mailto:mac_elli...@yahoo.com> > Date: Mon, 11 Sep 2017 16:32:09 +0000 > To: <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> > Subject: [PSES] LISN Calibration Measurement Uncertainty > > All, > > We are interested in doing some in-house LISN calibrations (impedance > verification only using network analyzer) and need to develop an uncertainty > budget. > > Does anyone happen to have a budget you could share with us? We will go > through the exercise of calculating ourself but if there is one out there > would appreciate it if you could share. > > Have a great day > > Mac Elliott > - > ---------------------------------------------------------------- > > 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 > <mailto:emc-p...@ieee.org> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used > formats), large files, etc. > > 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: > Scott Douglas <mailto:sdoug...@ieee.org> Mike Cantwell > <mailto:mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher <mailto:j.bac...@ieee.org> > David Heald <mailto:dhe...@gmail.com> > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > ______________________________________________________________________ > - > ---------------------------------------------------------------- > 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 > <mailto:emc-p...@ieee.org> All emc-pstc postings are archived and searchable > on the web at: http://www.ieee-pses.org/emc-pstc.html > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used > formats), large files, etc. > Website: http://www.ieee-pses.org/ > Instructions: http://www.ieee-pses.org/list.html > List rules: http://www.ieee-pses.org/listrules.html > For help, send mail to the list administrators: > Scott Douglas <mailto:sdoug...@ieee.org> Mike Cantwell > <mailto:mcantw...@ieee.org> For policy questions, send mail to: > Jim Bacher <mailto:j.bac...@ieee.org> > David Heald <mailto:dhe...@gmail.com> > > - > ---------------------------------------------------------------- > 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 > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used > formats), large files, etc. > > 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: > Scott Douglas <sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher: <j.bac...@ieee.org> > David Heald: <dhe...@gmail.com> > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > ______________________________________________________________________ > > - > ---------------------------------------------------------------- > 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 > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used > formats), large files, etc. > > 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: > Scott Douglas <sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher: <j.bac...@ieee.org> > David Heald: <dhe...@gmail.com> - ---------------------------------------------------------------- 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 Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. 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: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
