In message <[email protected]>, dated Wed, 11 Mar 2009, Bill Owsley <[email protected]> writes:
>Floating a scope is not just lifting the ground since the neutral (in >the USA) goes back to ground. But the neutral isn't connected to any signal circuits within the scope, so lifting the ground allows those circuits to be connected to a 'hot' reference point. >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. Isolation transformers create their own problems. There is a good reason why the neutral of public supplies is grounded, in all countries except where the surface of the planet is non-conducting rock (some parts of Norway and France, for example). A safety Class 1 product has only basic insulation between mains and accessible parts. That is OK if there is a second safeguard - grounding the accessible parts. But if they are not grounded and the mains is floating, an insulation failure can persist undetected. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Things can always get better. But that's not the only option. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - 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]>
