I agree that the AMN (LISN) is intended only to provide consistent (more or less) results, not to represent a real-world impedance at RF. I don't know how much that impedance changes from site to site; quite a lot I'll bet.
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>
