IMO, one of the errors of the standard or how it is interpreted, is to use a 4-line (two-pair) ISN/CDN for 10/100 Ethernet. Ethernet, in almost all applications, although there might be some where the following does not apply, uses 4-pair (8-line) cables (mostly UTP). If the DUT is a 10/100 device, the two pairs are typically terminated in some way at the port of the DUT. The unused - for traffic - pairs are typically terminated and so they contribute to the overal CM impedance and noise coupling mechanism. Therefore, in my opinion, Ethernet should (almost) always be tested using a device with 4-pairs. The only exception should be if it is verified that the unused pairs are really left completely disconnected at the DUT connector. Now, here I completely ignored my viewpoint that the current definition and construction of ISN/CDN devices is not suitable for Ethernet, i.e. the abovementioned would apply (again IMO) for a better CDN and ISN devices. Until then, V and I-clamp metod is much better. Actually, in -6, there is mostly ignored sentence that specifies that the selection of the CDN should be based on the number of wires in the cable (which I believe is a correct approach). Therefore it does not matter if I have 10/100 or Gbit device, I'd use 4-pair CDN/ISN. Neven Sorry, I am very opinionated :)
-------------- Original message -------------- From: John Woodgate <[email protected]> > In message > <[email protected]>, dated > Fri, 18 May 2007, "Kim, Ben" writes: > > >However, 10Mbps/100Mbps uses only 2 pair (4 wires) although the number > >of wires are 8. Since unused wires are not considered as "balanced > >pair", > >it would be still acceptable to use 2 pair (4 wires) balanced ISN for > >10/100Mbps mode per 9.6.3.1 > > It may be acceptable in terms of the standard, but the presence of > 'floating' wires in the cable is liable to result in malfunction, which > is what has been reported in this case. > > Exactly what damage (and how) the floating wires do is not clear to me, > but.... > -- > OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk > There are benefits from being irrational - just ask the square root of 2. > John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to [email protected] > > Instructions: http://listserv.ieee.org/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > > Scott Douglas [email protected] > Mike Cantwell [email protected] > > For policy questions, send mail to: > > Jim Bacher: [email protected]! &g t; David Heald: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
