Hi, I have been involved - as the customer - with the specification, installation, certification and use of over 27 shielded rooms - 5 of which are also anechoic. A shielded room is just that, whether it is connected to a protective earth or not. The 50/60/400Hz single or 3phase supplies need to be filtered - this is where the additional protective earth is necessary. It really should connect to the same panel of the shielding as the filters are attached to. I would think that the building lightning protection should protect the shielded room in all circumstances - except possibly damage to the filters >from the surge current. In this respect, apart from size, what is the difference between this box and all the other equipment boxes/racks in the building? We do not think of these as needing extra protection - do we? Regards Tim
************************ Tim Haynes Electromagnetic Engineering Specialist SELEX Galileo, A Finmeccanica Company 300 Capability Green Luton LU1 3PG (Phone () +44 (0) 1582 886239 (Mob )) +44 (0) 7540629920 (Fax 7)+44 (0)1582 795863 (Email *) t <mailto:[email protected]> [email protected] www.selexgalileo.com P Please consider the environment before printing this email. There are 10 types of people in the world-those who understand binary and those who don't. J. Paxman ________________________________ From: Fischer, Kurt [mailto:[email protected]] Sent: 03 August 2010 17:53 To: [email protected] Subject: Re: [PSES] Chamber Electrical Isolation Question *** WARNING *** This message has originated outside your organisation, either from an external partner or the Global Internet. Keep this in mind if you answer this message. Mac, I agree with Ghery’s points below; however, you should consider lightning protection. If the SE is touching the ceiling / roof then if there is a lightning strike to the building then the currents would flow onto the SE and eventually be concentrated at the “single-point” ground at the floor. Perhaps you should consider multi-point at the floor?? Just my 2 cents. Cheers, Kurt From: [email protected] [mailto:[email protected]] On Behalf Of Pettit, Ghery Sent: Tuesday, August 03, 2010 10:50 AM To: Elliott Mac-FME001; [email protected] Subject: RE: Chamber Electrical Isolation Question Mac, Single point grounding is of use if you are trying to use the room at very low frequencies where the thickness of the shield isn’t very many skin depths, thus allowing currents flowing through the shield to generate a field inside the room. If you are testing in the normal frequency ranges where we perform commercial EMC testing this is not an issue. I’ve had a chamber with a single point ground and I’ve had several where we paid no attention to single point grounding and they all worked fine. I wouldn’t worry about it. Ghery S. Pettit From: [email protected] [mailto:[email protected]] On Behalf Of Elliott Mac-FME001 Sent: Tuesday, August 03, 2010 7:30 AM To: [email protected] Subject: Chamber Electrical Isolation Question Colleagues I am in the process of investigating options for a possible FAR chamber [full ETSI Compliant]. I may be able to fit one in my building but may not be able to electrically isolate the chamber from the parent building structure [will be touching the ceiling at points] If we put 1 very good ground connection the thought is that any surface currents introduced to the shield will follow the path of least impedance and go to ground there and not cause standing waves in the chamber. My understanding of single point grounding for chambers evolved from a security perspective - so that it could be disconnected and the shield could be investigated for currents to detect listening devices - Fed-type stuff - and is not an essential requirement for EMC / Antenna applications. Does anybody have any feedback / experience / opinions on this? Do you foresee any issues with not electrically isolating the chamber from the parent building? 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. 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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]>
