Keith, I'd like to bring one more comment on top of all the rest of good ideas and advices for this question: Depending on your specific physical design and functionality, dielectric absorption may affect measurements and performance due to very long time constant charge displacements inside the insulating materials, which from the circuit functionality and troubleshooting perspective may look like leakage currents. Cosmin Iorga, NoiseCoupling.com http://www.noisecoupling.com tel: (805) 231-9786 ________________________________ From: keithK EPD <epd2001usa@xxxxxxxxxxx> To: si-list@xxxxxxxxxxxxx Sent: Thu, November 18, 2010 7:24:06 PM Subject: [SI-LIST] Re: Guard Rings ... DC I am dealing with DC ! so, some of my questions are not for the entire High speed audience, so I apologize I have a 4 gig ohm electrode/electrodes(s) ..... my electrode spacing is 0.230" and my socket has a 0.175" diameter / 4 layer I haven't seen much lit on the subject - PCB material / voids / components / etch width to the 1 resistor into the opAmp / given 0.060" / slots req'd what does conformal coating do for me.... comments, pointers to white papers, etc are welcome. Keith Kowal www.product-designs.com ------------------------------------------------------------------ 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 technical documents are available at: http://www.si-list.net 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 ------------------------------------------------------------------ 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 technical documents are available at: http://www.si-list.net 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