HI Orin and the group, One problem is that if that wire is a few inches long it may have a thousand volts drop along it length from Ldi/dt drop leaving the surface that is "grounded" as much as thousands of Volts above "ground" (other end of the wire) during the fast parts of the ESD event, enough to still jump to nearby circuits in some cases. If even 1% of that Ldi/dt drop couples through Mdi/dtinto nearby circuits, problems can result. Although some general rules can help, I find that each ESD problem needs to be analyzed (through lots of current and/or voltage measurements) to insure asolution is understood as to how it works. BTW, there are no voltage probes commercially available from the big measurement companies than work around ESD that I am aware of. The one that comes closest is a passive differential probe from Fischer Custom Communications. My favorite current probe for ESD work is the F-65 from Fischer Custom Communications. Doug On 9/24/14 12:38 AM, Orin Laney wrote: Which is why I run a separate wire. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx[1] [mailto:si-list-bounce@xxxxxxxxxxxxx[2]] On Behalf Of Douglas Smith Sent: Wednesday, September 24, 2014 12:00 AM To: si-list@xxxxxxxxxxxxx[3] Subject: [SI-LIST] Re: ESD failure - need advise I do not find simple general rules like this to be useful. On average, systems with circuit and chassis ground strongly interconnected do best for ESD immunity. I have confirmed this over hundreds of systems and thousands ofmeasurements. There is always a possibility of an exception. That wire carrying ESD to chassis can induce tens to hundreds of Volts/inch in nearby conductors! Doug On 9/23/14 4:16 PM, Orin Laney wrote: One useful strategy isto provided a trace, metal rail, etc. to intercept thezap and conduct it directly to the chassis without sharing with circuit grounds. In other words,it's a lightning rod. Somewhere else in the system the chassis and circuit are presumably tied together, but not as part of thispath. Shunting the zap works better than trying to prevent it with insulation and distance. Orin -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx[4][1] [mailto:si-list-bounce@xxxxxxxxxxxxx[5][2]] On Behalf Of Ramesh N Sent: Tuesday, September 23, 2014 3:48 PM To: si-list@xxxxxxxxxxxxx[6][3] Subject: [SI-LIST] ESD failure - need advise Hello Experts, Greetings!!! we are havingESD fail (in regulatory testing) in one of our design. It's simple wireless DAQ system with 2 boards [controller PCB + LED/Sensor PCB]. FPC cable (5") is used as interconnect.Package is abs plastics. Light-pipe is used for the for led indication. When +8kV is appliedthrough air discharging,inadvertent LED trigger occurs . Randomly, system is also hangingwhen multiple zapping applied (especially for 8kV voltage level). I have tried to limit airgaps, added filter caps, etc but issue is not entirelysolved. Is there any ESD simulation/analysis tool available for addressing this failure analysis? Any help/debug tips related to this would be very helpful. Thanks and regards, Ramesh ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx[7][4] with 'unsubscribe'in the Subject field or to administer your membership from a webpage, go to: //www.freelists.org/webpage/si-list[8][5] For help: si-list-request@xxxxxxxxxxxxx[9][6] with 'help' in the Subject field List forum is accessible at: http://tech.groups.yahoo.com/group/si-list[10][7] List archivesare viewable at: //www.freelists.org/archives/si-list[11][8] Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu[12][9] ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx[13][10] with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list[14][11] For help: si-list-request@xxxxxxxxxxxxx[15][12] with 'help' in the Subject field List forumis accessible at: http://tech.groups.yahoo.com/group/si-list[16][13] List archives are viewable at: //www.freelists.org/archives/si-list[17][14] Old (prior to June 6, 2001)list archives are viewable at: http://www.qsl.net/wb6tpu[18][15] --- Links --- 1 mailto:si-list-bounce@xxxxxxxxxxxxx[19] 2 mailto:si-list-bounce@xxxxxxxxxxxxx[20] 3 mailto:si-list@xxxxxxxxxxxxx[21] 4 mailto:si-list-request@xxxxxxxxxxxxx[22] 5 //www.freelists.org/webpage/si-list[23] 6 mailto:si-list-request@xxxxxxxxxxxxx[24] 7 http://tech.groups.yahoo.com/group/si-list[25] 8 //www.freelists.org/archives/si-list[26] 9 http://www.qsl.net/wb6tpu[27]10 mailto:si-list-request@xxxxxxxxxxxxx[28] 11 //www.freelists.org/webpage/si-list[29] 12 mailto:si-list-request@xxxxxxxxxxxxx[30] 13 http://tech.groups.yahoo.com/group/si-list[31] 14 //www.freelists.org/archives/si-list[32] 15 http://www.qsl.net/wb6tpu[33]----------------------------------------------- ------------------- To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx[34] with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list[35] For help: si-list-request@xxxxxxxxxxxxx[36] with 'help' in the Subject field List forumis accessible at: http://tech.groups.yahoo.com/group/si-list[37] List archives are viewable at: //www.freelists.org/archives/si-list[38] Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu[39] --- Links --- 1 mailto:si-list-bounce@xxxxxxxxxxxxx 2 mailto:si-list-bounce@xxxxxxxxxxxxx 3 mailto:si-list@xxxxxxxxxxxxx 4 mailto:si-list-bounce@xxxxxxxxxxxxx 5 mailto:si-list-bounce@xxxxxxxxxxxxx 6 mailto:si-list@xxxxxxxxxxxxx 7 mailto:si-list-request@xxxxxxxxxxxxx 8 //www.freelists.org/webpage/si-list 9 mailto:si-list-request@xxxxxxxxxxxxx 10 http://tech.groups.yahoo.com/group/si-list 11 //www.freelists.org/archives/si-list 12 http://www.qsl.net/wb6tpu 13 mailto:si-list-request@xxxxxxxxxxxxx 14 //www.freelists.org/webpage/si-list 15 mailto:si-list-request@xxxxxxxxxxxxx 16 http://tech.groups.yahoo.com/group/si-list 17 //www.freelists.org/archives/si-list 18 http://www.qsl.net/wb6tpu 19 mailto:si-list-bounce@xxxxxxxxxxxxx 20 mailto:si-list-bounce@xxxxxxxxxxxxx 21 mailto:si-list@xxxxxxxxxxxxx 22 mailto:si-list-request@xxxxxxxxxxxxx 23 //www.freelists.org/webpage/si-list 24 mailto:si-list-request@xxxxxxxxxxxxx 25 http://tech.groups.yahoo.com/group/si-list 26 //www.freelists.org/archives/si-list 27 http://www.qsl.net/wb6tpu 28 mailto:si-list-request@xxxxxxxxxxxxx 29 //www.freelists.org/webpage/si-list 30 mailto:si-list-request@xxxxxxxxxxxxx 31 http://tech.groups.yahoo.com/group/si-list 32 //www.freelists.org/archives/si-list 33 http://www.qsl.net/wb6tpu 34 mailto:si-list-request@xxxxxxxxxxxxx 35 //www.freelists.org/webpage/si-list 36 mailto:si-list-request@xxxxxxxxxxxxx 37 http://tech.groups.yahoo.com/group/si-list 38 //www.freelists.org/archives/si-list 39 http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu