No criticism of how a LISN is calibrated. That wasn't the point. The point was that LISN impedance uncertainty affects the measurement of conducted emissions differently by mode, so that the overall uncertainty of the measurement of CE is different from that of the LISN impedance. Also, while the point of a 50 uH LISN is in fact to provide that impedance, the original limit was based on the rf susceptibility of radios operating below 30 MHz, and that susceptibility was to the rf potential caused by various electronic loads. It wasn't about current at all.
Ken Javor Phone: (256) 650-5261 > From: Ralph McDiarmid <ralph.mcdiar...@schneider-electric.com> > Date: Mon, 11 Sep 2017 23:36:35 +0000 > To: Ken Javor <ken.ja...@emccompliance.com>, "EMC-PSTC@LISTSERV.IEEE.ORG" > <EMC-PSTC@LISTSERV.IEEE.ORG> > Conversation: [PSES] LISN Calibration Measurement Uncertainty > Subject: RE: [PSES] LISN Calibration Measurement Uncertainty > > Perhaps all that is needed is to know is the Insertion Loss of the LISN. Some > manufacturers provide this for every s/n. > > The LISN is only there to provide a known impedance to the source of emission > so that RF current can be measured with repeatability. I do understand that > CM and DM currents will have different (and unknown) source impedance and that > those impedances will be a function of frequency, but I feel that's beside the > point. > > I have to assume the folks at CISPR understood those topics and that they > likely deliberated long and hard and did lots of measurements both in the lab > and in the field before agreeing on the LISN as a standard transducer for the > evaluation of conducted RF emission. > > If there were something fundamentally wrong with the method of measurement, I > suspect it would have been uncovered long ago. > > Ralph McDiarmid > Product Compliance > Engineering > Solar Business > Schneider Electric > > > From: Ken Javor [mailto:ken.ja...@emccompliance.com] > Sent: Monday, September 11, 2017 4:10 PM > To: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] LISN Calibration Measurement Uncertainty > > 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 > - ---------------------------------------------------------------- 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>
