Speaking of effects of changing the capacitance to the horizontal coupling plane, take a look at the effect of placing small rubber feet on a small enclosure:
http://emcesd.com/tt2006/tt010106.htm Would you retest if you added these thin feet to an enclosure? I would bet most would not, but should. Doug On 7/26/11 3:06 PM, Bill Owsley wrote: how about the dielectric constant of the spacer? It can range from near air using paper, to something over 10 using some of those fancy materials. Certainly that would change the capacitive coupling to reference plane and that would affect the ESD waveform. And the how to test the spacer for voltage withstand, or to detect any leaks? Say hi-pot it to 15 kV, or 30 kV.? Attitude is Mind over Matter. If you don't Mind, it doesn't Matter... This email has been displayed using 100% recycled electrons and 100% pure virgin photons. ________________________________ From: Derek Walton <[email protected]> <mailto:[email protected]> To: [email protected] Cc: [email protected]; [email protected]; [email protected] Sent: Tuesday, July 26, 2011 8:45 AM Subject: Re: [PSES] ESD Spacer Hi Doug? I'm lost: what secondary discharge? Please don't include MU in ESD discussions, MU in EMC is a stupid idea at best. Leave that to Meteorologists. Your idea of common sense, may not agree with others. Imagine what havoc we would unleash if we applied common sense to many of our standards. If it's important, it MUST be specified, and be proceeded by a "SHALL". Otherwise, it's open season. Cheers, Derek. -----Original Message----- From: Doug Smith <[email protected]> <mailto:[email protected]> To: Derek Walton <[email protected]> <mailto:[email protected]> Cc: Michael_Sundstrom <[email protected]> <mailto:[email protected]> ; bstammerjohan <[email protected]> <mailto:[email protected]> ; EMC-PSTC <[email protected]> <mailto:[email protected]> Sent: Tue, Jul 26, 2011 1:32 am Subject: Re: [PSES] ESD Spacer Hi Derek, I disagree. Why would you knowingly allow secondary discharges that are more intense than applied stress? In this case, the measurement uncertainty of the setup would go up astronomically, dominating all other factors, if the insulating layer can be penetrated by a spark. The EN may not specify this, but common sense must prevail. Doug On 7/25/11 7:27 PM, Derek Walton wrote: > Hi All, > > I'd just like to point out here that the EN does not give any criteria for the dielectric withstand nature of the spacer. So, while we can argue best practice, if a lab meets the thickness, all is permissible. > > I also disagree with Doug's statement on cables. You must test with whats supplied by the manufacturer, or with ones that he states you must use. Why, well because cables can make a huge difference in performance. I would call messing with cables like this part substitution and fraud. > > > > > I also disagree about using new cables. The reason for this is that cables will degrade with some flexing and you should be assuring a product meets the EMC requirements for it's design lifetime, not on a good day in a lab, with the wind behind it and rubber boots on. > > Just trying to keep the common sense hat on compliance testing > > Cheers, > > Derek Walton. > > > > > -----Original Message----- > From: Doug Smith<[email protected]> > To: Sundstrom, Michael<[email protected]> > Cc: Bryce Stammerjohan<[email protected]>; EMC-PSTC<[email protected]> > Sent: Mon, Jul 25, 2011 8:59 pm > Subject: Re: [PSES] ESD Spacer > > > If the poster board is 0.5 mm thick as required, you may be failing equipment that might otherwise pass, which I have seen happen. A spark through the poster board will likely be worse than the one you supply from the ESD simulator in terms of peak current and di/dt. In any case, unless the poster board in 0.5mm thick and you have confirmed there is no spark through, than you cannot say you have tested to IEC 61000-4-2! Maybe OK for a pretest but not for CE marking. It's hardly worth it to save a few cents on test materials (the insulating layer we are talking about, USB cables, Ethernet cables, and many other things) and waste thousands of dollars in the end. I see this happen a dozen times per year. > > I also recommend using new, high quality cables for any performance test. This is especially important for USB and Ethernet cables. > > Doug > > On 7/25/11 10:32 AM, Sundstrom, Michael wrote: > > > Guys, > > I just use poster board, I get 20 sheets at a local office supple house for $5-$6 ? > > Am I missing something? Do you need plastic sheets? > > > > > > > Michael Sundstrom > > OHD / TREQ Dallas > > Electronic Lab Analyst, EMC Lead > > 2170 French Settlement Rd, Suite B > > Dallas, Texas 75212 > > (214) 579 6312 > > (940) 390 3644c > > KB5UKT > > > > Albert Einstein once said, "The definition of insanity is doing the same thing over and over again and expecting different results". > > > > > > > From: Bryce Stammerjohan [mailto:[email protected] <mailto:[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://product-compliance.oc.ieee.org/ > 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]> -- ------------------------------------------------------- ___ _ Doug Smith \ / ) P.O. Box 1457 ========= Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-----( ) | o | Email: [email protected] \ _ / ] \ _ / Website: http://www.dsmith.org ------------------------------------------------------- - ---------------------------------------------------------------- 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://product-compliance.oc.ieee.org/ 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]> -- ------------------------------------------------------- ___ _ Doug Smith \ / ) P.O. Box 1457 ========= Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-----( ) | o | Email: [email protected] \ _ / ] \ _ / Website: http://www.dsmith.org ------------------------------------------------------- - ---------------------------------------------------------------- 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://product-compliance.oc.ieee.org/ 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]>
