Depending on the enclosure material if its isn't' some high permeability material such as mu metal, the window probably isn't' the greatest concern to magnetic radiation is it? A quick but old example is putting a CRT on top of aluminum or steel CPU chassis over or near the power supplies large input transformers (long before switch mode supplies) used to cause a lot of deflection and 50/60 Hz interference. Either the monitor had to be moved or the CRT yoke magnetically shielded with mu metal. Gary
From: Price, Ed [mailto:[email protected]] Sent: Thursday, September 16, 2004 6:49 AM To: [email protected] Subject: RE: Germanium & ITO Window shielding effectiveness From: Chris Maxwell [mailto:[email protected]] Sent: Thursday, September 16, 2004 5:42 AM To: Barker, Neil; Price, Andrew P (UK Basildon); Emc-Pstc (E-mail) Subject: RE: Germanium & ITO Window shielding effectiveness I agree with Andy. ITO coating has a surface resistivity of 14Ohms/sq inch. You could probably get just as much surface resistivity from a coating of dust :-) ITO coatings are good at dissipating static; but I think that they are pretty much useless for shielding. I shudder to think of how naïve we were back in 1995 when this whole EMC (CE marking) kick began. We had one product with a window about 2" x 2". We had the window ITO coated. We spaced mounting screws every 1/2" around its edge and then used conductive RTV between the edge and the Aluminum panel into which it mounted. We took a $2 window assembly and turned it into a $50 window assembly. (we did this on the advice of someone we trusted) I looked into it a little while later and found the above facts regarding the surface resistivity of the ITO coating. We would have done just as much good by flushing money down the toilet. I would recommend a window with a fine, high mu wire (monel?) mesh shield. Tecknit and Chomerics make some shielded windows like this. Best regards, Chris Maxwell Umm first, what is ITO? (Indium Thorium Oxide <g>, so maybe it also acts like a nightlight?) Sorry, couldn't help that. Anyway, we need to know the permeability of the material too; isn't it possible that even a fairly thin film of a poor conductivity, but permeable material, will give a bit of shielding (redirection) of a magnetic field? The OP was talking only about magnetic field shielding. Regards, Ed Ed Price [email protected] WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
