Hi Pat, May be it helps reading through the literature on our web ( www.euro-emc-service.de ) with hints to our inventions like GTEM (end of 80s), EUROTEM (End of 90s) etc, plus background (R&D-web-section) info. A size limited TEM device can not do everything but may sometimes prove useful. Detailed info also in IEC 61000-20. TEM Devices for radiated emission and immunity.The basic idea is to consider a free space (TEM-basically only mode) wave inside and for emissions use the concept of t o t a l radiated power to correlate to OATS.This requires EUT mechanical rotations in a GTEM (Dr. Perry F. Wilson Algorithm- now working for NIST Bolder Co--He also published an article I think in IEEE EMC Transaction How to correlate below 30 MHz several years ago (mid 90s?) ). At the Apex you receive (based on simple e.g. 3, x-y-z orientation of EUT) voltages vs. frequency to feed into the software correlation algorithm. To be more specific we need to hear details of the product (EUT), in particular size! Cables do also matter! One TEM cell competitor is e.g. compact chambers now. What TEM type of cell are you considering? Regulatory compliance/acceptance under EN 55022/ CISPR 22 issues (accreditation?) may also be an important issue. IEC 61000-20 is "just" a new basic standard.....normative references....? The GTEM is listed in the new ANSI/IEEE C 63.4. Diethard Best regards
Dr. Diethard Hansen EES President, Principal Consultant, Trainer US Senior NARTE certif. EMC Eng. 001937NE EMC+Automotive+Telecom QM+techn. EA-Auditor Euro EMC SERVICE (EES) Dr.-Ing. D. Hansen POB 64, Bahnhofstr.39, CH-8965 Berikon 2, Switzerland, Swiss VAT (Mwst.)No.:323214 tel./fax: +41 566 33 73 81 German mobile phone: +49(0)1736015909 www.euro-emc-service.de euro.emc.serv...@swissonline.ch ( mailto:diethard.han...@ieee.org) Consulting+Seminars+R&D-Projects Marketing+CE-Testing+ww.Audits From: owner-emc-p...@listserv.ieee.org mailto:owner-emc-p...@listserv.ieee.org]On Behalf Of pat_law...@condordc.com Sent: Mittwoch, 17. November 2004 20:19 To: emc-p...@ieee.org Subject: Using TEM cells for radiated emissions at 30MHz Hi: I was given some literature by management recently advertising the use of a TEM cell for radiated emissions: http://www.wavecontrol.com/index2004.php?idioma=2 Our people have the impression that a TEM cell small enough to fit on a table-top could eliminate the need to go to the local OATS. I don't think it's that simple, but I need more solid information. The products I test are component power supplies, using CISPR 22 Class A & Class B limits. Most of our emissions are in the range of 30-100MHz. 1) I've heard TEM cells need correlation to an OATS. Is this a one-time correlation (like a calibration), or is it tied to the model being tested? 2) The dimensions of the TEM cell appear small compared to a wavelength at 30MHz. Does the issue of near-field and far-field zones still apply in a TEM cell? If so, how do you correlate the two? 3) The product appears to have pyramid absorbers inside (no reverberation). Does this mean the EUT needs to be repositioned several times during the test? 4) How do the TEM cell correlation factors and noise floor of the spectrum analyzer interact? Do I need a certain maximum noise floor in order to make measurements? I guess I'm looking for a TEM cell tutorial, or maybe a book or paper titled 'TEM Cells For Dummies'. I wrote to the vendor, but they haven't responded. On a slightly different note, has there been any progress for accepting emissions measurements from reverberation chambers (IEC 61000-4-21)? Thanks in advance, Pat Lawler EMC Engineer Condor DC Power Supplies, Inc. -------- ------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Scott Douglas emcp...@ptcnh.net 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://www.ieeecommunities.org/emc-pstc ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Scott Douglas emcp...@ptcnh.net 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://www.ieeecommunities.org/emc-pstc
