The ferrite works well ONLY if you have correctly chosen Low Q ferrite that is especially lossy at the frequency of interest; otherwise, you are correct. Too often I see people simply clamping on a hunk of ferrite with no idea what flavor it is. If any lab has unidentified ferrite in their sample kits or just laying around they should consider dumping it.
-doug From: Cortland Richmond [mailto:k...@earthlink.net] Sent: Thursday, July 14, 2011 1:18 PM To: 'Emc-Pstc (E-mail)' Cc: Powell, Doug; 'Price, Edward'; oconne...@tamuracorp.com Subject: RE: bulkhead feedthrough for chamber I once worked at a company where one chamber used cables fed through a “waveguide below cutoff” from an often noisier control room. Predictably, EMI from control room test and support equipment polluted testing in the attached chamber. Such an entry is good only for fiber optic and other nonconductive signals and controls. A conductor in a waveguide converts it to a section of coaxial feedline and even large ferrites and CISPR EMC clamps did little to help. “Yuh tells ‘em an’ tells ‘em...” I have also seen shielding thwarted in this or similar ways at third-party test labs whose personnel should have known better. It may be worthwhile to discuss here what duty one owes a customer to observe the practices needed to make tests meaningful. Cortland Richmond KA5S From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Powell, Doug Sent: Thursday, July 14, 2011 11:06 AM To: Price, Edward; oconne...@tamuracorp.com; Emc-Pstc (E-mail) Subject: RE: bulkhead feedthrough for chamber Grounded coaxial connectors on penetrations panels is always a good idea. Same with filtered D-SUB and so on. But getting every flavor can be a problem. An alternative is pipes. Study circular waveguide operating below cutoff for correct sizing of a pipe. For a 1 MHz chamber, I design the pipe to cutoff at 3MHz. One of my favorite tricks is thread an I/O cable through the pipe with a stack of suppression beads on the cable and inside the pipe. Douglas E Powell www.advanced-energy.com/renewables <http://www.advanced-energy.com/> This message, including any attachments, may contain information that is confidential and proprietary information of Advanced Energy Industries, Inc. The dissemination, distribution, use or copying of this message or any of its attachments is strictly prohibited without the express written consent of Advanced Energy Industries, Inc. - ---------------------------------------------------------------- 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 <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at http://product-compliance.oc.ieee.org/ 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 <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com>
