At each frequency where the emission is more than the limit or close to the limit
a. Measure the emission with the DUT in full functional mode. b. Now remove the DUT (in your case the USB encryption key) and measure the emission. If emission at (a) and (b) are same then DUT is not the cause, else DUT is the cause. Can't we conclude this way. Finding a quite laptop or hub seem to be almost impossible. Bala |------------> | From: | |------------> >------------------------------------ -----------------------------------------------------------| |"Piotr Galka" <[email protected]> | >------------------------------------ -----------------------------------------------------------| |------------> | To: | |------------> >------------------------------------ -----------------------------------------------------------| |"EMC-PSTC" <[email protected]>, "John Woodgate" <[email protected]> | >------------------------------------ -----------------------------------------------------------| |------------> | Date: | |------------> >------------------------------------ -----------------------------------------------------------| |04/15/2009 04:27 PM | >------------------------------------ -----------------------------------------------------------| |------------> | Subject: | |------------> >------------------------------------ -----------------------------------------------------------| |Re: SV: "Quiet" Laptop | >------------------------------------ -----------------------------------------------------------| From: "John Woodgate" <[email protected]> >>Can't it be done that way, that peripherals are tested alone but with some >>dB lower limits ? > > Not usually, because the peripheral doesn't work, or doesn't work in a way > that might produce more emissions, unless it's connected to a computer. I supposed connected to PC, but PC as AE (out of measurement room). > In any case, there is no provision in EN standards for such a procedure. My intention was to ask why there is no provision in EN standards for such a procedure. The world would be easier I think. When I was testing USB encryption key the lab suggested that instead of searching for good PC I can measure my key with USB-hub. The hub should have its own power supply to test Surge at it and not at PC. During test the highest source of emission was switched mode power supply sold with this hub. I'm not sure if nest time replacing it with other source classic supply would be OK, or it is unaccepted idea. Piotr Galka - 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]>
