It is understood that capacitance between the test sample and ground will affect common mode emissions. What is the significance of vertical over horizontal grounds, and why specifically 40 cm? The file cabinet example mentioned previously is not terribly convincing in that file cabinets (in my experience) are not usually grounded. Ken Javor
Phone: (256) 650-5261 ________________________________ From: "ce-test, qualified testing bv - Gert Gremmen" <[email protected]> List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: Wed, 23 Sep 2009 17:47:54 +0200 To: Ken Javor <[email protected]>, <[email protected]> Conversation: [PSES] Conducted emission measurements Subject: RE: [PSES] Conducted emission measurements The capacitance between EUT and 40 cm plane (be it V or H) Is the return path for the common mode current on the mains lead. Make the capacitance smaller (d> 40 cm) then emission decrease, Make it higher (d < 40 cm) then emissions increase. 40 cm is a good compromise for EUT with irregular surfaces and common sizes. Only for CM current ! There are proposals to allow for measurement of house-hold equipments such as vacuum cleaners on a 10 cm from ground. This definitely means more conducted emissions. Rationale: Vacuum cleaners normally operate close to a conductive ground. Note that the LISN measures both CM and DM current, with a coupling factor of -6 dB There is discussion about the coupling factors when ground lead Is connected, so be aware of that. Gert Gremmen Ce-test, qualified testing bv Van: [email protected] [mailto:[email protected]] Namens Ken Javor Verzonden: woensdag 23 september 2009 17:24 Aan: [email protected] Onderwerp: Re: [PSES] Conducted emission measurements Rephrase the question: From an electrical point-of-view, how does the presence of a vertical ground plane at 40 cm separation affect conducted emissions? Ken Javor Phone: (256) 650-5261 ________________________________ From: <[email protected]> List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: Wed, 23 Sep 2009 10:16:11 -0500 To: Ken Javor <[email protected]> Cc: <[email protected]> Subject: Re: [PSES] Conducted emission measurements Ken and List, It was explained to me as: to simulate a file cabinet next to a desk in an office environment type of setup. This is just one example I recall from the various audits I've been through over the years. Michael Sundstrom Electronic Lab Analyst Overhead Door TREQ Center, Dallas [email protected] OFC: 214-579-6312 CELL: 940-390-3644 KB5UKT Ken Javor <[email protected]> 09/23/2009 09:56 AM Please respond to Ken Javor <[email protected]> To [email protected] cc Subject Re: [PSES] Conducted emission measurements What is the rationale behind a vertical conducting surface for conducted emissions? Ken Javor Phone: (256) 650-5261 ________________________________ From: Wan Juang Foo <[email protected]> List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: Wed, 23 Sep 2009 13:46:27 +0800 To: <[email protected]>, <[email protected]> Cc: Wan Juang Foo <[email protected]> Subject: Re: Conducted emission measurements Hello Tim, I may be missing. Is there such a 40 cm height? Here is my 5 ยข worth. These are some of the the special provision for conducted emission testing: To meet EN 55011, I suppose since 1999?? the measurement may be carried out: - on the radiated emission test site (same EUT configuration) - above a metal ground plane which shall extend at least 50 cm beyond the boundary of the equipment under test and have a minimum size of 2m x 2m - within a screened room; either the floor or one wall of the screened room shall act as the vertical ground plane .. CISPR 22 since (1993) and Amendment 1 (1995) Table- top EUTis to be placed 40 cm from a vertical metal reference plane (e.g. a wall of a screened room/enclosure) "The EUT, where intended for table-top use, shall be placed 0,4 m from a vertical metal reference plane of at least 2 m by 2 m and shall be kept at least 0,8 m from any other metal surface or other ground-plane not being part of the EUT. If the measurement. is made in a screened enclosure, the distance of 0,4 m may be referred to one of the walls of the enclosure." Floor- standing EUT on a horizontal metal ground- plane, not in metallic contact with the ground- plane. Metal floor of a screened room may replace the reference ground- plane best regards, Tim Foo Expert Witness, EMC and Product Safety ECE, School of Engineering, http://www.np.edu.sg/ece/ <http://www.np.edu.sg/ece/> <http://www.np.edu.sg/ece/> DID: +65 6460 6143 Ngee Ann Polytechnic, 535 Clementi Road, Fax: +65 6467 1730 Singapore 599489 [email protected] wrote on 23/09/2009 06:06:05 AM: > Hello Group, > > I have a question about the conducted emission measurements > performed in a semi-anechoic chamber. > > CISPR 22 requires the use of a vertical ground plane when testing > tabletop EUTs, unless you mount your EUT on a non-conductive table > 40cm above the horizontal ground plane (instead of the traditional 80cm) > > I did not find a requirement for a vertical ground plane when > testing floorstanding equipment. If one opts to use the alternative > method of not using the vertical ground plane, can floorstanding > equipment also be tested without the vertical ground plane? The > horizontal ground plane is always present since that is the chamber floor. > > What are most labs using? We have the option of making a removable > vertical ground plane "wall" or mounting the equipment on a 40cm table. > > Thanks, > Tim Pierce > - ________________________________ NOTICE: This message may contain privileged/confidential information. If you are not the intended recipient of this email, please delete it immediately and notify the sender . - 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] <mailto:[email protected]> <mailto:[email protected]> > All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc <http://www.ieeecommunities.org/emc-pstc> <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/ <http://www.ieee-pses.org/> <http://www.ieee-pses.org/> Instructions: http://listserv.ieee.org/request/user-guide.html <http://listserv.ieee.org/request/user-guide.html> <http://listserv.ieee.org/request/user-guide.html> List rules: http://www.ieee-pses.org/listrules.html <http://www.ieee-pses.org/listrules.html> <http://www.ieee-pses.org/listrules.html> For help, send mail to the list administrators: Scott Douglas <[email protected] <mailto:[email protected]> <mailto:[email protected]> > Mike Cantwell <[email protected] <mailto:[email protected]> <mailto:[email protected]> > For policy questions, send mail to: Jim Bacher <[email protected] <mailto:[email protected]> <mailto:[email protected]> > David Heald <[email protected] <mailto:[email protected]> <mailto:[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]> - 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]>
