Ah yes I know it well. As smeone who has encountered the discharge from power supply caps that haven't fully discharged after the power was turned off. The designer I was working with had disconnected the bleeder resistor. And all this with an agency rep looking on.
Doug --- "Peter L. Tarver" <peter.tar...@sanmina-sci.com> wrote: > > From: Doug Beckwith > > Sent: Friday, December 03, 2004 6:56 AM > > > > I suspect that 100% of people in the engineering > > profession have > > experienced it because we tend to ask "I wonder > > what happens > > when......?" > > > > Doug > > > > And some inadvertently. > > Product safety engineers seem to take many chances with > their persons. No matter how wary we think we are or how > careful we believe ourselves to be, we commit the very acts > we intend to protect others from. Another anecdote of a > _one_finger_ electric shock: > > While working on a product, I was demonstrating to a safety > agency engineer that a product had an accessibility issue > that was a risk of electric shock. The product was sitting > on an static dissipative bench top, with a 1-? in. tall fan > module (otherwise secured with knurled thumbscrews) removed. > Mains voltages were accessible through the opening on a PWB > mounted, right-angle connector. The unit was connected to a > 120V source, with power switch on the power supply in the > OFF position. > > What I neglected to consider in that moment of glory, was > that the very accessibility issue I was demonstrating with > my finger was that the power supply switch did not > disconnect mains voltages from the entire product. To > receive this shock, I had to bridge phase and neutral, so > the current path through my body was very limited. I > consider myself lucky that my reaction did not do more than > take a little skin off my finger, by scraping it along a > sheet metal edge at high velocity. > > > A phantom shock anecdote: > > At another time and working with another product with the > same agency engineer, I reached out to adjust a potential on > a power converter sourced by a test sample when my cell > phone range. The cell phone (at my hip) was set to vibrate. > In retrospect, I'm not sure which was more precious: my > reacting (which was identical in gesture to the above real > shock scenario, though without injury) or the look on the > agency engineer's face when he saw my reaction. > > > Regards, > > Peter L. Tarver, PE > ptar...@ieee.org > > > This message is from the IEEE Product Safety Engineering > Society > emc-pstc discussion list. Website: > http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to > emc-p...@ieee.org > > Instructions: > 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: emc-p...@hypercom.com > Scott Douglas emcp...@ptcnh.net > > For policy questions, send mail to: > > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web > at: > > http://www.ieeecommunities.org/emc-pstc > ______________________________________________________________________ Post your free ad now! http://personals.yahoo.ca This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: 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: emc-p...@hypercom.com Scott Douglas emcp...@ptcnh.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
