Hi Ken, Ok, you caught me exercising a pet peeve (hop up here on the table peeve). My problem stems from specifications which state nominal component values rather than a verifiable Zin. The 61000-4-4 mains coupler is a pretty worst case example. Huge variation in the actual devices from manufacturer to manufacturer. The thing I like better about the LISN is that both the insertion loss and Zin as a measurement system component are specified and verifiable. Of course, connections to the LISN can seriously distort it's response, just as can connections to the 10 uF cap.
I hope my personal prejudices don't step on anyone's toes. Best regards, Brent -----Original Message----- From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Wednesday, December 27, 2000 12:57 AM To: bdew...@ix.netcom.com; 'praveen rao'; 'muriel bittencourt de liz' Cc: emc-p...@majordomo.ieee.org Subject: Re: Doubt with conducted emissions measurement Hi Brent, Specifically NOT meaning to argue, but only in pursuit of the TRUTH, isn't the 10 uF feedthrough cap a perfectly well-defined source impedance above, say 15/20 kHz, where the old MIL-STD-461A/B/C CE03 limit started? Which is not to say that the current measurement is preferred, but what makes a LISN more consistent? The new MIL-STD-462D and -461E cites the fact that a LISN is more representative of a real world bus impedance, and therefore a filter designed to work with a LISN works similarly with the real bus. But that is not a testability issue at all. Respectfully, Ken Javor ---------- >From: "Brent G DeWitt" <bdew...@ix.netcom.com> >To: "'Ken Javor'" <ken.ja...@emccompliance.com>, "'Praveen Rao'" <p...@tennyson.com.au>, "'Muriel Bittencourt de Liz'" <mur...@grucad.ufsc.br> >Cc: <emc-p...@majordomo.ieee.org> >Subject: RE: Doubt with conducted emissions measurement >Date: Tue, Dec 26, 2000, 11:48 PM > > Hi Ken, > > After twenty years or so of EMC testing, I find myself more often using the > word "consistent" rather than "accurate". This is exactly the issue of "n" > ohm LISNs versus voltage or current probes. Current probes and voltage > probes are certainly as accurate as a LISN, but they leave in doubt what > source impedance the system was working into. The selection of 50 ohms is > certainly debatable, especially in light of the 150 ohm specification for > CDNs, and I won't even attempt to defend the number. The key is that, when > we can't hope to define what's "right", we can at least attempt to define > consistency. > > Best regards sir, > > Brent DeWitt > > -----Original Message----- > From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf > Of Ken Javor > Sent: Tuesday, December 26, 2000 7:56 PM > To: Praveen Rao; 'Muriel Bittencourt de Liz' > Cc: emc-p...@majordomo.ieee.org > Subject: Re: Doubt with conducted emissions measurement > > 2) Why does Mr., Rao (or anyone else) feel that the LISN-based measurement > is more accurate than a current probe measurement? I can see pros and cons > to each, myself. > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
