John, You are arguing
"Should the test conditions not reflect the actual environment in use of the product, rather than employ these unusual materials?" The problem is that we do not know the actual conditions. So we need to define the test conditions. If everyone use be using the SAME wooden table, it would be fine. But that is not the case and there are large variations between different wooden tables, surface materials etc. So if one uses a wooden table, its influence must be taken into the uncertainty calculation. This adds a few more dBs, much more above 1 GHz. In radiated immunity it is even worse, as there is no maximization done. David Pommerenke -----Original Message----- From: John Woodgate [mailto:[email protected]] Sent: Friday, November 02, 2001 1:34 AM To: [email protected] Subject: Re: EMC test table construction plans I read in !emc-pstc that Pommerenke, David <[email protected]> wrote (in <[email protected]>) about 'EMC test table construction plans', on Thu, 1 Nov 2001: >For emissions and immunity you should not use any wood in the table. It will >significantly (+/-2 dB up to 1 GHz for emissions , more above, +/-10 dB for >immunity up to 1 GHz) change the test result. My experience has shown that >Styrofoam is basicly the best material. You mean that it gives the worst-case results? >There are a couple of published >papers on this issue. As surface material the following worked out fine: > > - Foamed PVC (rather stiff, low dielectric constant due to the foamed >nature), maybe 4 mm thick. > > - PE sheet, maybe 2 mm thick. Should the test conditions not reflect the actual environment in use of the product, rather than employ these unusual materials? -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Eat mink and be dreary! ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [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: No longer online until our new server is brought online and the old messages are imported into the new server. ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [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: No longer online until our new server is brought online and the old messages are imported into the new server.
