There has been proposal that cables leaving the test volume be ferrited with long ferrites with (if I remember well) 12-14 dB of attenuation
in the frequencies of interest. But as such ferrite create a CM impedance at the point of entry, and this impedance was not accurately specified, the ferrite created huge differences in test results. You can imagine that a high CM impedance (400 ohm up) can be seen as a cable termination, creating all kinds of resonances and frequency preferences. Ideally such a ferrite should have 150 Ohms of CM impedance, in order to make the cable look like infinite to CM currents. That requirement combined with 10 dB attenuation was a step too far for ferrite clamp manufacturers so the proposal was withdrawn. Our setup uses a cabling duct of metal from the center of the turn table leading to the wall of the room, where each cable is terminated in a suitable filter, where at the outside a suitable load or power source or network cable is connected. The part of all cables in the duct is supposed to be “screened” and not contribute to the radiation pattern inside the room How the CM impedances behave is currently undefined, and for that reason I am in favor of suitable ferrites be designed and connected to each cable leaving the test volume. We also use USB to network convertors with extra shielding to create “silent” USB interfaces on the turn table. Here also, the CM impedance on the USB cable from EUT is unknown. There is so much to develop and to research in this matter. Gert Gremmen ce-test, qualified testing bv Van: [email protected] [mailto:[email protected]] Namens Oaks, Dustin Verzonden: woensdag 29 september 2010 16:43 Aan: [email protected] Onderwerp: EN55022 Hello Everyone, I have been questioned (Internally) regarding our test setup for Radiated Emissions under EN55022:2006 +A1. Therefore, I thought I would do a survey to see how my interpretation fairs against others. A simple question, are ferrites allowed on cables connected to AE located off the turn table? Example setup: - EUT on Table - AE located outside Chamber/Test area - Interconnecting cable is routed from EUT straight down through center of table, under ground screen to AE. Question: Are ferrites allowed anywhere along the interconnecting cable? Any and all feedback would be greatly appreciated. Thank you, Dustin Oaks | Pelco by Schneider Electric | United States | Compliance Laboratory Supervisor Phone: +1-559-292-1981 ext. 3348 | Fax: +1-559-388-7117 | Support: +1-800-289-9100 Email: [email protected] | Site: www.pelco.com <http://www.pelco.com/> | Address: 3500 Pelco Way, Clovis, CA 93612-5699 - USA *** Please consider the environment before printing this e-mail This transmission is intended only for use by the intended recipient(s). If you are not an intended recipient you should not read, disclose copy, circulate or in any other way use the information contained in this transmission. The information contained in this transmission may be confidential and/or privileged. If you have received this transmission in error, please notify the sender immediately and delete this transmission including any attachments. - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ 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]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ 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]>
