Make a building far larger than a 10 meter OATS. Then inside the walls of that building add layer upon layer of cones and tiles until you get well over 60 dB of attenuation of ambient signals. The reciprocal applies. The common and likely cheaper chambers of today, make a Faraday shield and then line it with absorbers to reduce internal reflections, which have to go through the absorbers twice. Without a shield, the emissions going out have to be attenuated below the limits with one pass through the absorbers. (that are twice as thick!) The stand alone building would use the absorbers for attenuating both the ambient and the emitted from the EUT. My SWAG would be 8-12 feet thick walls of absorbers to get the attenuation needed. But modern absorbers might perform better than I have experienced and the walls might be under 8 feet thick. This endeavor is a near trivial spreadsheet exercise in costing one verses the other. The design parameters are available in the spec's of the materials. The building cost is probably the same for both.
The chamber shielding plus cones is an adder. The double set of cones is the other option. The answer without even putting in any numbers is obvious to any that have done just one chamber with prices. Or just the first pass at the pricing. >________________________________ > From: Ed Price <edpr...@cox.net> >To: EMC-PSTC@LISTSERV.IEEE.ORG >Sent: Monday, August 12, 2013 7:34 PM >Subject: Standalone EMC Chamber? > > > >Gary & Elliott: > >Back around 1978, before we had learned a lot of hard lessons about what >constitutes a good OATS, I tried using a 100’ by 30’ by 15’ high tent (sort of >like a canvas Quonset hut) as a cover on an asphalt pad and hardware cloth >proto-OATS. Although the concept was good, I found that rain and dust and >pollution created patchy “regions” of slightly reflective, not quite >free-space. (Maybe a different membrane material would have worked better than >the rubberized canvas I used. A windstorm finally ended my agony.) > >But if you wanted this tent to be a shield, then I would think that any decent >shield (like a metalized plastic film) would be a nasty reflector. If all you >wanted was shielding, then OK, it would be like a reverberant chamber minus >the paddles. But the inside reflections would be catastrophic if you wanted an >equivalent to an OATS. Any method I can think of to reduce the internal >reflections would seriously bulk up the mass and/or weight of the tent >membrane. > >Still, you want to keep an open mind. If somebody can show you a tent >structure that yields a 10-meter OATS volume, then all they have to do is >demonstrate the OATS field uniformity and also show a reduction (60 dB would >be nice) of external signals from the plentiful FM & TV & other emitters. And >then all would be fine, until the wind kicks up. > >Ed Price >WB6WSN >Chula Vista, CA USA > >From:McInturff, Gary [mailto:gary.mcintu...@esterline.com] >Sent: Monday, August 12, 2013 8:38 AM >To: EMC-PSTC@LISTSERV.IEEE.ORG >Subject: Re: [PSES] Standalone EMC Chamber? > >At last week’s EMC symposium there was at least one vendor that was selling >EMC “tents” if you will and I don’t know how large they were, but I have seen >10 meter tents – but they certainly weren’t in a part of the country that has >snow. >Sorry I don’ have the full list of vendors at the show, but if you look up >2013 EMC symposium you should still be able to find the symposium schedule and >vendors for the tent guy. >I’ve seen a 3 meter and a 10 meter tent so they exist, but the companies that >used them have either moved into an SAC or got out of that business – at least >in at the facility that I saw the tent. >Sorry no direct answer but again look for the symposium notes and vendor list > >Gary > >From:Elliott Mac-FME001 [mailto:fme...@motorolasolutions.com] >Sent: Monday, August 05, 2013 8:36 AM >To: EMC-PSTC@LISTSERV.IEEE.ORG >Subject: Re: [PSES] Standalone EMC Chamber? > >Thanks, Brian. > >This sounds like what I am talking about to a degree. The structure would be >totally self-supportive and not attached to a building as yours is, but would >not be in any parent structure at all [i.e. exposed to the elements. Sure >there are code issues as well. > >This chamber would not be in any building at all – would just be by itself >outside. > >Best regards, > >Mac Elliott > > >[ ] General Public >From:Kunde, Brian [mailto:brian_ku...@lecotc.com] >Sent: Monday, August 05, 2013 11:10 AM >To: EMC-PSTC@LISTSERV.IEEE.ORG >Subject: Re: [PSES] Standalone EMC Chamber? > >Mac, > >I’m not exactly sure what you are asking. Stand-alone or not, a 10 meter >chamber takes up a lot of space. > >We have a 10 meter SAC that is supported by its own steal frame structure, >meaning, it is not attached to the building. The supporting structure only >adds about 4ft to the length and width. I thought they were all built that >way, but maybe not. I can send you pictures if that would be helpful. > >One constructional consideration which is very nice is having the chamber >built in a pit so the GRP is at the same level as that area outside the >chamber, and there is room under the GRP for your turntable, power cables, >etc. That way you can roll large or heavy equipment into the chamber without >using an elevator or have to go up steps. Just my 2 cents. > >The Other Brian > >From:emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Elliott >Mac-FME001 >Sent: Monday, August 05, 2013 10:19 AM >To: EMC-PSTC@LISTSERV.IEEE.ORG >Subject: Standalone EMC Chamber? > >Hello group, > >A colleague of mine mentioned that he had seen a “stand-alone” EMI chamber at >a test lab. One of the obstacles we have in getting a chamber is the lack of >space in our building and he thought this may be a good solution to our >dilemma. > >I am not aware of any chambers that do not require a parent structure. > >Are any of you aware of any EMC chambers [3 or 10m – preferably 10m] that do >not require a parent building and operate “stand-alone”? > >Best regards, > >Mac Elliott > > >[ ] General Public >- >---------------------------------------------------------------- >This message is from the IEEE Product Safety Engineering Society emc-pstc >discussion list. 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To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. 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 <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
