Section 9.5.3.5 of CISPR 22, 3rd Edition reads:
“9.5.3.5 Measurements at telecommunications ports intended for connection to cables containing more than two balanced pairs or to unbalanced cables The measurement method of C.1.3 or C.1.4 shall be used. At each frequency, the requirements shall be met either by using the method of C.1.3 or by using the method of C.1.4. NOTE – It is allowed to measure with method C.1.3 and then to measure with method C.1.4 only at frequencies for which the limit is exceeded when using method C.1.3.” Note that the title of the section refers to the cable, not the port, when discussing the number of pairs. C.1.3 and C.1.4 deal with current probes and capacitive voltage probes. No schematic is provided for an 8 wire ISN in the 3rd Edition of CISPR 22. Now, when we go to CISPR, 5th Edition (and EN 55022:2006), we have a slight difference: “9.6.3.1 Voltage measurement at balanced telecommunication ports intended for connection to unscreened balanced pairs When disturbance voltage measurements are performed, an ISN providing a voltage measuring port suitable for connection to a measuring receiver while satisfying the telecommunication port common mode termination impedance requirements shall be used. When disturbance voltage measurements are performed on a single unscreened balanced pair, an adequate ISN for two wires shall be used; when performed on unscreened cables containing two balanced pairs, an adequate ISN for four wires shall be used; when performed on unscreened cables containing four balanced pairs, an adequate ISN for eight wires shall be used (see Annex D).” Figure D.3 provides an ISN for 8 wires. This was new in the 4th Edition, but as the 4th Edition wasn’t adopted as a version of EN 55022, nobody paid it much attention (just like Figure C.6 and its impact on power line communications, but that’s another story). So, now that 5th Edition is taking effect around the world, you need an 8 wire ISN for Ethernet. I’m not convinced that R&S, Fisher and others should have labeled 4 wire ISNs for Ethernet, but that was a common practice. I know we’ve used those ISNs for Ethernet (up to 100 Base T, anyway). I hope this helps. Not only did the characteristics of the ISNs change with the new versions of CISPR 22, but an 8 wire flavor was added, and should be used for all 8 wire cables. Ghery S. Pettit _____ From: Larry Stillings [mailto:[email protected]] Sent: Friday, May 18, 2007 1:01 PM To: Pettit, Ghery; [email protected]; [email protected]; [email protected] Subject: RE: EN 55022:1998+A!+A2 vs EN 55022:2006 Ghery, I need to ask about this one. All of the CDN / ISN adapters I have used including R&S, Fischer & Schaffner 4-Wire ISN/CDNs all have coupling networks for 4 interfaces and are labelled for E1, Ethernet, ISDN, etc., so you are saying the intent of CISPR 22 was to have all those interfaces tested with an Eight Wire ISN? This is news to me, how many others on this list? Thanks. Larry Stillings _____ From: Pettit, Ghery [mailto:[email protected]] Sent: Friday, May 18, 2007 3:49 PM To: [email protected]; [email protected]; [email protected] Subject: RE: EN 55022:1998+A!+A2 vs EN 55022:2006 CISPR 22 requires that you use an ISN based on the number of wires in the cable, not the number actually being used. All Ethernet tests should be done with an 8 wire ISN as Cat 3, Cat 5 and Cat 6 cables all have 8 wires. Ghery _____ From: [email protected] [mailto:[email protected]] Sent: Friday, May 18, 2007 12:35 PM To: Pettit, Ghery; [email protected]; [email protected] Subject: Re: EN 55022:1998+A!+A2 vs EN 55022:2006 Hi Ghery, It is a two balanced pair ISN, so of course Gigabit Ethernet will not function, but I had trouble with 100 Mbps working through the ISN. I couldn't get a ping through it, so the probes were used instead. Maybe a newer 8 wire ISN will do the job. Thanks, Tim _____ See what's free at AOL.com <http://www.aol.com?ncid=AOLAOF00020000000503> . - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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