Good People, Nothing I say represents the policy or opinions of my employer.
Did not intend to sound like a cold, heartless, Darwin-driven guy; actually I am a warm, heartless, Darwin-driven guy. I 'eat my own dog food'; that is, almost everything on my safety benches are floated via galvanic isolation using my EIT-series iso xfmrs. And I have also have opened the connection to 'ground' on some of the instruments. The set-up is required for both sanity and accuracy in the performance of leakage/touch current measurements, for working voltage measurements, and for recording and analyzing fault currents. As for capacitive coupling - the iso xfmrs have less than 0.015pf - so not a concern. But body impedance is <1500 ohms (much less than the 1000s of megaohms for the iso) so if you bridge certain instruments with your body, you will not be happy. My philosophy is simple - product safety Type Tests shall be performed with a high state of awareness and attention to detail - if myself or the technician gets shocked, then I have reason to suspect the veracity of the test data, because the test was not being performed with due diligence. The insurance company and the lawyer are aware of this 'situation' - and we now list, by name, who shall be allowed in the product safety area. Now ask me about that large, thick piece of lexan and the two steel boxes next to the bench... R/S, Brian From: [email protected] [mailto:[email protected]]On Behalf Of Bill Owsley Sent: Wednesday, March 11, 2009 5:54 PM To: [email protected]; [email protected] Subject: Re: Ungrounded (was RE: scope probe gnd) Floating a scope is not just lifting the ground since the neutral (in the USA) goes back to ground. Floating for me is using an isolation transformer - there is no galvanic connection to the mains. As you've mentioned - training as in education. And yes, there's some capacitive coupling that could make touching some voltages somewhat uncomfortable but your back pockets won't explode in flames. - Bill Indecision may or may not be the problem. --- On Wed, 3/11/09, Cortland Richmond <[email protected]> wrote: From: Cortland Richmond <[email protected]> Subject: Ungrounded (was RE: scope probe gnd) To: [email protected] List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: Wednesday, March 11, 2009, 7:28 PM We have read in this thread about missteps which were, luckily, only embarassing. Given that training is SUPPOSED to inform people so they don't do stupid things, and that we do them anyway, I am just as glad to see insulating covers on LISN's. I know why my former colleague floated the scope and I see it done quite a bit. But I am also unwilling to let a stupid mistake be the last mistake we can ever make. In that lab, I had a chance to make things safer and I did. Whether the inspector has legal grounds for writing a citation depends on your state's occupational safety laws. I am definitely the wrong guy to ask about that! However, you might ask your firm's attorney(s) whether it is legal to pull the safety ground off test equipment in yours. And what happens when the required warnings aren't enough. Cortland Richmond > [Original Message] > From: Brian O'Connell <[email protected]> > To: <[email protected]> > > Would like more info on the basis of requirement that this 'hazard' be mitigated, if the access to the area is controlled and only trained personnel familiar with hazard mitigation are allowed to operate equipment. I am constantly arguing with the fire/health inspector on this issue, and am weary of citing the same OSHA clauses. Last month, I was down the street visiting a friend at his place of employment and watched the same inspector walk by some serious fire and shock hazards in a common area. To quote the great philosopher Bugs Bunny, "what a marooon..." > > I can think of several reasons that your former safety engineer 'floated' the test equipment. And I have a large banner above my safety benches that indicate that "test equipment on this bench may be floated - extreme shock hazard". > I also routinely have type test set-ups that expose hundreds or thousands of volts to the bench user. And so what ? The lab is a controlled space. What concept am I missing ? - 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://www.ieeecommunities.org/emc-pstc 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]>
