http://www.ieee-pses.org/symposium http://www.emc2004.org/
Hi All, A secondary use for the resistors is that they help break up the resonant circuit composed of the HCP on the table and the plane on the floor capacitor and the inductance of the connecting lead. The old ANSI standard on ESD also had a 2K resistor in the lead just for this purpose as the ~470K resistors act like small capacitors instead of resistors at frequencies above about 1 MHz or so. I have seen installations with little film resistors in the bleed wire, not a good idea. Such resistors do not handle high peak voltages/currents well and can open or change value over time. 2 watt carbon comp resistors will be less likely to "spark over" and will also be physically robust with use. Doug Chris Maxwell wrote: > http://www.ieee-pses.org/symposium http://www.emc2004.org/ > -------------------------------------------------- > ...... > Most ESD setups require the 940Kohm resistance from the coupling planes > (HCP or VCP) to ground. > > -The resistors complete the circuit from ESD gun to GRP through the > coupling plane, allowing for potential equalization (charge bleeding) > between discharges. This makes repeatable test results. > > -The high value of the resistors protects the test personnel in the > following instance: if the test tech touches a hazardous voltage in the > EUT with one hand and touch the coupling plane with the other hand; then > the high resistance to ground will limit the current through the tech?s > chest cavity (the worst possible area for hazardous current to flow). > On the other hand, if the coupling plane was grounded, or bonded to > ground with a low resistance, there would be a dangerous current through > the tech?s chest cavity. This is OSHA?s peeve with grounded > conductive tabletops. David was more enlightened regarding the OSHA > requirements, so this is a tidbit that I didn?t have. > ....... > Chris Maxwell -- ___ _ 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. IEEE PSES Main Website: http://www.ieee-pses.org/ To post a message send your e-mail to [email protected] Instructions for use of the list server: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [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: http://www.ieeecommunities.org/emc-pstc
