If you are going to make repeatable measurements two things have to hold true. The LISN has to continue to provide its function, and the LISN has to be close enough to the EUT that the mismatch between EUT, power cord and LISN doesn't cause vswr errors. At 30 MHz, the power cord should be l/10, or one meter. Of course that isn't the case, so there is already some question as to the accuracy of the present measurement stopping at 30 MHz. It is pretty easy to design a 50 uH LISN to 100 MHz, but you should check. Also, there are 5 uH LISNs that have been designed to 400 MHz. Above about 2 MHz, it doesn't matter whether you use a 5 or 50 uH LISN, so you have that possible alternative.
If it were me, and I wanted to make accurate and repeatable CE measurements, I would either shorten the power cord to one-tenth wavelength, or I would go to a current probe measurement and slide the current probe up and down the power cord looking for peaks (spectrum analyzer in max hold while scanning frequencies and scanning the probe). I also think it would be very important to discriminate between different conduction modes, dm or cm or super-cm (current flowing same sense in phase, neutral and safety ground). From: "Garnier, David S (GE Healthcare)" <david.garn...@med.ge.com> List-Post: emc-pstc@listserv.ieee.org Date: Thu, 29 Sep 2005 10:55:58 -0500 To: <emc-p...@ieee.org> Subject: Measuring Conducted Emissions above 30 Mhz Hello EMC Guru's, I am looking for some guidance... Is there an established Standard & Test Method for measuring AC Power Conducted Emissions above 30 MHz (say to 150 MHz?) ((Obviously, CE limits for CISPR11 only go to 30 Mhz.)) Thanks for your time, Dave Garnier David Garnier e GE Health Care ___________________________________________ David S. Garnier Senior Technician Functional & CT Engineering 3000 N. Grandview Ave - M/S W-1250 Waukesha, Wi. 53188 Tel: 262.312.7246 Cel: 414.899.7580 - 2005 IEEE Symposium on Product Safety Engineering 3-4 October Schaumburg, IL http://www.ieee-pses.org/symposium ---------------------------------------------------------------- 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: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - 2005 IEEE Symposium on Product Safety Engineering 3-4 October Schaumburg, IL http://www.ieee-pses.org/symposium ---------------------------------------------------------------- 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: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc