Using fiberoptic link is best if you can do it. However even so you need another end of the twisted-pair cable connected to another 100 Mbps device. You may check that device by looping it back on itself first and performing the immunity test on it. If it passes, it is safe to asume that it will not fail as supprt equipment to another DUT. Absorption clamp is an easy to use device too.
What I would recommend if you really want good decoupling of your AUX equipment is to use another set of Ethernet transformers in line with your cable. The transformers must have center taps in each pair, on both sides. I recomment GBit 1:1 transformers from BelFuse or Pulse. Insert transformers in line to each pair (used and unused), close to your AUX equipment, preferably at the chamber feedthrough panel. Place 75 Ohm resistor from each center-tap on the DUT-side to GND (chamber- wall/panel) for common-mode termination. On the other (AUX) side of the transformers conect the center taps directly to the ground panel. You don't care about high- voltage isolation in this application, so you don't need any caps. If you keep the connections from the center taps very short and low-inductance, this will be almost a bulletproff combination for protecting AUX equipment. Some other additional measures come to mind, such as shielded cable on the AUX side and extra 10-15pF (max) from each line to GND, but most likely you will never really need them. All this said, there are many products on the market that meet 10V and 10 V/m, you can verify it with a pre- test as I mentioned earlier, so I don't think you really need such a bulletproof combination. You can expect much more troubles with EFT and AUX equipment than with conducted or radiated RF. Good luck, Neven > > I want to provide isolation for auxillary equipment while performing > radiated/conducted immunity testing on 100BT LAN. Tests are performed in a > shielded room, and a bulkhead is used. Right now, cables pass right through > the bulkhead (with, of course, split core ferrites of varying materials > clamped to the cables on either side of the bulkhead). But this is not good > enough. > > Does anyone have an effective means of keeping the RF energy where it > belongs (behind the bulkhead) ? By the way, this is low level testing, no > more than 10V/m and 10 Vrms. > > I have an option of using a fiber link (modem) through the bulkhead, > however, I am not sure if this equipment will be susceptible, and no > samples are available for test. > > Thanks in advance. > > Paul > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > 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: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ 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: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
