Hello James, In your response you said: "it is not easy to monitor the quality of the link for judging performance against immunity criteria A/B/C" as a downside to the loopback method. I have also had other responses that detailed the requirements from CISR24 as to the monitoring of transmission performance during an immunity test. While I can see that might be an issue for server farms and the like - but for AV equipment surely not!
My question (for the group) is : Why (for streaming video) is it necessary to monitor the link minutia? Surely the test requirement is that the video will continue undisturbed under excitation from external fields. As long as my viewing experience is uninterrupted - then that's a PASS. (I can see how monitoring the stream might be beneficial for diagnosing immunity issues). Best Regards Charles Grasso Compliance Engineer Echostar Communications (w) 303-706-5467 (c) 303-204-2974 (t) 3032042...@vtext.com<mailto:3032042...@vtext.com> (e) charles.gra...@echostar.com<mailto:charles.gra...@echostar.com> (e2) chasgra...@gmail.com<mailto:chasgra...@gmail.com> From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Pawson, James Sent: Thursday, December 29, 2011 2:55 AM To: 'Chris Wells'; 'Knighten, Jim L'; EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: What means do you use to exercise Ethernet telecom ports? Hi Chris, As for the CISPR 22 conducted emissions test that Jim mentioned in his orginal message the measurement is made using an ISN which defines the CM impedance of the AE so no issues there. You would also have to make sure that the cable lengths / distances to the walls of the test chamber were as per the standard and that would be your CM impedance defined. For CISPR 24 conducted immunity testing (using 61000-4-6) the noise is injected using a CDN (very similar to an ISN) which again provides a defined CM impedance. I guess also the CM impedance for a radiated emissions test would also be OK as the dimensions / orientation of the cable bundle is defined. Another disadvantage to the simple loopback method that I just thought about is that it is not easy to monitor the quality of the link for judging performance against immunity criteria A/B/C. You can monitor the Link Up status in the software to a first approximation but data transfer / ping is more suitable in this case. As for your "emissions quiet" transciever it is possible to execute a cheap but effective Cat-5 chamber entry/exit filter that effectivley removes any CM emissions from the incoming lead. Not quite what you were asking for though :( Regards, James ________________________________ From: Chris Wells [mailto:radioactive55...@comcast.net] Sent: 28 December 2011 17:03 To: Pawson, James; 'Knighten, Jim L'; EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: What means do you use to exercise Ethernet telecom ports? James/Jim I like the loop back test idea for preliminary EMI testing due to the simplicity. However another issue is that it lacks the common mode impedance relationship at the AE end. I suppose one could use a long enough cable to create some capacitive relationship to the ground plane but the pulse transformer at the far end would not be there. Back to the AE side of this discussion: I am having similar issues in doing some preliminary emission testing where I was using a Cat5 to fiber optic transceiver as the AE end (another FO/Cat5 outside the chamber to my notebook). This approach worked well for EMI testing since the transceiver was robust enough but I found that my transceiver was a major source of emissions during my emission testing. Can anyone suggest an "emission quite" FO/Cat5 transceiver that would behave for my testing? Thanks Chris Wells Eaton Corp. Subject: RE: What means do you use to exercise Ethernet telecom ports? Hi Jim, As a basic test you can make an RJ45 connector that connects the EUT TX lines to the RX lines thus looping back the Ethernet interface onto itself. This certainly works for 100BaseTX because the EUT sees it's own Link Test Pulse, assumes it is connected to another Ethernet interface and then activates it's scrambled_idle packet mode. This is a 100BaseTX PRBS sequence that maintains a net 0Vdc bias on the lines which is used to get round the issues with first pulse as seen on 10Base-T Advatanges of this method - it doesn't require other equipment in the chamber / test area - very cheap to make - no software support required so useful for a at the start of EUT validation testing Disadvantages - the EUTs PHY (and maybe a bit of the MAC) is the only part of the EUT Ethernet interface that is activated. As other posters have pointed out, pinging, file transfer will generate electrical activity futher up the 7-layer OSI model - you might not be able to ping or generate traffic at all as the EUT might figure out it is connected to itself and redirect traffic internally (this statement is a guess) I would imagine that it would work with Gigabit as this should use scrambled_idle packets as well. If you want to use an application to get data moving over a network connection I would highly recommend using iperf (http://sourceforge.net/projects/iperf/) which is primarily a network testing tool. It transfers far more data than ping, can do bidirectional data transfer and if highly configurable. The command line interface is easy to use, can't comment on the jperf GUI. Disadvantage against ping is that it requires iperf to be running on both ends of the link whereas ping doesn't Hope this helps James Subject: [PSES] What means do you use to exercise Ethernet telecom ports? I am curious what means people are using to exercise Ethernet telecom ports when testing for conducted emissions according to CISPR 22 and conducted immunity according to CISPR 24? Do you use an external piece of equipment (AE) to send Ethernet traffic? If so, what do you use and do you like it? My particular interest is 1000BaseT (gigabit Ethernet), but the question is more general. Thanks in advance, Jim - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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