Test to the appropriate standard. C63.4 does not use it. If you are using a product family CISPR standard, follow it. CISPR22, for example, does not use the inductor.
Ghery S. Pettit From: [email protected] [mailto:[email protected]] On Behalf Of Elliott Mac-FME001 Sent: Monday, September 13, 2010 9:04 AM To: [email protected] Subject: LISN - Use of 1.6 mH Earth Line Choke - In or Out Recently the question of whether the 1.6 mH Earth Line Choke should be used during conducted emissions tests came up in discussion with another colleague. The purpose of the choke is to avoid double RF ground connection in the conducted emissions test setup. My colleague reported to me that he was seeing 20-30 dB difference between readings at around 8 MHz, with the higher emissions being reported with the choke inline. His question was, do I test with it IN or OUT? CISPR 16-1-2 does define the impedance, but indicates that it may be required for certain types of equipment following the requirements in related publications. Not normative or required it seems. Since the standard that he is testing to is ANSI C63.4, he referred to it reported that the 1.6mH choke does not seem to be indicated anywhere in the standard, which seemed to be correct after a check myself. This got me questioning as well and I did a bit of research and came across a very good paper which states with regards to this earth lead inductor "The inductor is not now a requirement of any international standards. Since its inclusion compromises the HF impedance from EUT earth connection to ground reference plane (because of the need for a switch), best engineering practice would dictate that it is left out of modern designs of AMN/LISNs." Honestly - for our type of equipment we have checked it both ways - IN and OUT - and have never to my knowledge seen a great difference in results. It does seem to be dependant on the EUT and the frequency of emissions and the impedance it produces at those frequencies on whether or not you see great differences. Unfortunately for my friend, it seems his type of equipment is very sensitive to it. The difference is pass and fail with it IN or OUT. ANSI C63.4 does not define or require the use of the choke and the CISPR documentation indicates that it may be required for certain equipment following the product standard. I believe the guidance to give him would be to follow the standard - which in this case seems to be to test with the choke out. Do you guys agree? Any thoughts or experience or feedback on this earth line inductor and when it is appropriate [outside of any standard requirements] to use it would be much appreciated. Best regards, Mac Elliott [ ] General Public - ---------------------------------------------------------------- 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]>
