It appears that there is a common electrical (galvanic) reference plane/s. The vertical one is 40 cm from the EUT/tabletop, and the horizontal one is 80 cm from the EUT/tabletop. The LISN is bonded galvanically to this common reference plane. The receiver is coax connected to the LISN, and the usual AC mains powered receivers are Safety grounded to earth via the earth in the AC power cord. The common electrical reference planes are usually earthed as well to ensure no floating metal that could get energized to some unsafe voltage. This common electrical reference plane/s placed in the specified positional relationship to the EUT provides a "standard" test configuration to make somewhat repeatable measurements.
- Bill In the event of a national emergency, click on the following links to provide directions to your duly elected mis-representative. http://www.usa.gov/Contact/Elected.shtml or... https://writerep.house.gov/writerep/welcome.shtml http://www.senate.gov/general/contact_information/senators_cfm.cfm --- On Wed, 9/23/09, Ken Javor <[email protected]> wrote: From: Ken Javor <[email protected]> Subject: Re: [PSES] Conducted emission measurements To: [email protected] Date: Wednesday, September 23, 2009, 4:11 PM Curiouser and curiouser. The ground plane to which the LISNs are connected must indeed be grounded, for safety if nothing else. But there is something else: the EMI receiver interrogating the LISNs ground the LISN by virtue of the coaxial connection between LISN EMI port and EMI coaxial input, both of which are grounded. That ground plane is 80 cm below the nonconductive table top, right? Am I understanding/misunderstanding that now there is a vertical ungrounded conductive surface at 40 cm distance from the test sample? I’m thinking I must be mixing up multiple inputs here. Ken Javor Phone: (256) 650-5261 ________________________________ From: "ce-test, qualified testing bv - Gert Gremmen" <[email protected]> Date: Wed, 23 Sep 2009 19:29:15 +0200 To: Ken Javor <[email protected]>, <[email protected]> Conversation: [PSES] Conducted emission measurements Subject: RE: [PSES] Conducted emission measurements There is no technical ground for the difference In H versus V ground plane. Just that if the set-up is compared by dummies they look different and may be justification for challenging test results. The loop to consider for CM current is: EUT – 80 cm of mains wire – LISN – 50 Ohm (both phases) - ground plane – 40 cm distance capacitor – EUT Where: - One of the 50 Ohms loads is the measuring receiver. - The ground plane does not need to be grounded, just a convenient low impedance conductor - The 80 cm of mains wire is critical in the way excess length is folded - The LISN needs to be bonded to the ground plane with 30cm wide conductors to prevent 25-30 MHz resonances - The 40 cm is arbitrary chosen a long time ago I do not think the setup was to mimic a file cabinet. Gert Gremmen Ce-test, qualified testing. Van: [email protected] [mailto:[email protected]] <http://us.mc396.mail.yahoo.com/mc/[email protected]]> Namens Ken Javor Verzonden: woensdag 23 september 2009 17:59 Aan: [email protected] Onderwerp: Re: [PSES] Conducted emission measurements 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]> 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]] <http://us.mc396.mail.yahoo.com/mc/[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]> 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]> 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 ¢ 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]> <http://us.mc396.mail.yahoo.com/mc/[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]> <http://us.mc396.mail.yahoo.com/mc/[email protected]> > Mike Cantwell <[email protected] <mailto:[email protected]> <http://us.mc396.mail.yahoo.com/mc/[email protected]> > For policy questions, send mail to: Jim Bacher <[email protected] <mailto:[email protected]> <http://us.mc396.mail.yahoo.com/mc/[email protected]> > David Heald <[email protected] <mailto:[email protected]> <http://us.mc396.mail.yahoo.com/mc/[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]> - ---------------------------------------------------------------- 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]>
