| Electronics > Beginners |
| An oscilloscope with no earth (crappy wiring in house) |
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| HackedFridgeMagnet:
Could an electrician rewire just one outlet to have a properly connected Earth? Then you could use that for your lab equipment. I'm not familiar with US style split supply, or 6 phase or whatever it is, but, it could be a worry if your ground clip on your probe gets connected to some unsafe voltage. Then your whole lab will be made unsafe. |
| FriedMule:
Greetings from Denmark:-) I think that you have 3 sollutions: as ovnr writes about --- Quote from: ovnr on July 04, 2014, 01:51:34 pm ---Well, you may have a ground somewhere in the house - even 80s houses had grounded outlets (kitchen stove, bathroom, etc). Consider just running a loose ground lead (of suitable size) to your lab - that's what I ended up doing. Also, you can buy plug-in GFCIs - here's one. If you can't afford to have your house re-wired, I'd strongly suggest buying one for your lab. (As others already have, I strongly suggest getting your wiring sorted out. Yes, it's ridiculously expensive, but it's worth it. And no more old decrepit outlets and light switches!) --- End quote --- The HPFI or CFCI as it is also called do protect you perfectly, if you should be extremely unlucky you will get a short zap and that's it. You can also as ovnr says, find an outlet with ground, put a wire in it and then run it all the way to your lab, try to look in your lamp in the ceiling, they do often have a ground because it was more easy just to make ground everywhere. Last get a Earth rod and make your own ground. But have you considered if it may not be to your advantage, not to have ground? Your whole system is right now floating and you avoid many of the danger to your gear that a ground do give you. |
| AVGresponding:
--- Quote from: FriedMule on August 26, 2019, 02:15:12 pm ---Greetings from Denmark:-) I think that you have 3 sollutions: as ovnr writes about --- Quote from: ovnr on July 04, 2014, 01:51:34 pm ---Well, you may have a ground somewhere in the house - even 80s houses had grounded outlets (kitchen stove, bathroom, etc). Consider just running a loose ground lead (of suitable size) to your lab - that's what I ended up doing. Also, you can buy plug-in GFCIs - here's one. If you can't afford to have your house re-wired, I'd strongly suggest buying one for your lab. (As others already have, I strongly suggest getting your wiring sorted out. Yes, it's ridiculously expensive, but it's worth it. And no more old decrepit outlets and light switches!) --- End quote --- The HPFI or CFCI as it is also called do protect you perfectly, if you should be extremely unlucky you will get a short zap and that's it. You can also as ovnr says, find an outlet with ground, put a wire in it and then run it all the way to your lab, try to look in your lamp in the ceiling, they do often have a ground because it was more easy just to make ground everywhere. Last get a Earth rod and make your own ground. But have you considered if it may not be to your advantage, not to have ground? Your whole system is right now floating and you avoid many of the danger to your gear that a ground do give you. --- End quote --- This so called 'floating ground' may only serve to provide a false sense of security; while you hold a probe in this system, you run the chance of becoming the path for current to ground... I've seen a lot of argument in these forums about the relative merits of floating vs earth ground reference, but the fact remains that if you're mucking around with high potential systems there's always going to be a chance for you to be the link between +/-V and GND. Whether your system is isolated or not, that's going to spoil your day (or maybe make it, I hear some people enjoy electric shocks *looks at Big Clive*) and maybe your test gear too. With enough energy in the system it's maybe fatally problematic. The long and short of it is, if you don't know what you're doing, don't do it. For those that insist on doing it anyway, take every available precaution (RCD/GFCI + isolation tranny + variac + differential probe) but don't expect these things to save your life/equipment if you fuck up badly enough. There are ways to achieve gear-safe measuring without recourse to all these methods, but they are ONLY for people that understand WHAT THEY ARE DOING and also THE RISKS involved to their person. @queennikki1972 since you say your main board is grounded (presumably you mean with earth as the reference), there are a few ideas for you to consider. If your house has drywall/studwall and not stone/brick walls, it might be practical for you to have just one circuit rewired to include a CPC (circuit protective conductor) aka PE (protective earth) for a relatively low cost. Alternatively, it might be possible to have a radial socket installed directly from the board, perhaps directly adjacent to the board, which you could use with an extension lead to wherever it's needed. I've seen a few people post that GFCI/RCDs will work fine on a 2 wire system. In theory, maybe, but I'd not trust my life to it. Ultimately there are NO safe ways to manually probe unsafe voltages, there are only ways to reduce your risk of death/serious injury. If you make yourself the current path for a large voltage, GFCI/RCDs and isolation transformers will only limit the maximum V/I you're exposed to, they won't make it 'safe'. I hate when people say 'as an engineer or w/e with X qualifications and Y years experience I can tell you Z', but in this instance I'll break my own rules a bit lol... As a mechanical and electrical engineer and electronics hobbyist of 40 years experience, with C&G and HNC qualifications, I can tell you I've had an actual mains V electric shock just ONCE (about a year ago, hell of a time to lose my virginity dammit), due entirely to the fact that electricity rightly scares the shit out of me, and therefore I am SUPER careful where I stick my probes (and also my fingers, now). |
| janoc:
--- Quote from: GeorgeOfTheJungle on July 03, 2014, 08:15:11 pm --- --- Quote from: steverino on July 03, 2014, 06:45:57 pm --- In the USA, a GFCI receptacle is used in these situations for personal safety. --- End quote --- And in Europe -by law- it's mandatory that all mains plugs be protected by a GFCI. ... --- End quote --- Ehm, nope. This varies between countries (building and electrical codes are not standardized across Europe!) and especially the older installations predating the rule (if there is one) don't need to be upgraded to match the newer code unless major work is being done that requires a new approval. So if you are relying on this you will sooner or later get a very nasty surprise. |
| Mr. Scram:
Why did we dig up a thread from 2014? Especially one which has two or three currently active duplicates with what’s essentially the same question. |
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