| Products > Test Equipment |
| Floating Scopes |
| << < (4/23) > >> |
| Fungus:
--- Quote from: dicky96 on June 22, 2017, 10:27:21 am ---Is it any more dangerous to float my Rigol 1052 and take sensible precautions ... Than it is to use my Fluke 79 with the negative terminal clipped to hot ground --- End quote --- Yes! With the fluke you normally make momentary contacts and you're looking at what you're doing. Even if you clip the leads onto the DUT, there's only one COM connection on the Fluke and you're very unlikely to touch the metal of the other input jacks with your fingers. Not so the 'scope! When one BNC of the 'scope is connected to something hot, all the BNCs are connected to something hot. The BNCs are exposed metal which is easy to touch if (for example) you decide you need another probe. Plus you might have multiple probes connected to the device at any time and that would create hot ground clips lying around the bench every time you connect to the DUT. |
| Vtile:
Sounds dodgy to float the scope by removing the "ground pin", I personally wouldn't trust the scopes internal design to keep it "floating" as the neutral is in most electrical distributing systems still ground connected somewhere in the building or in the power grid. Floating the scope with safety isolation transformer (the english term might be slightly different, the point is that your typical galvanically isolated transformer is not build this kind of use in mind [even if that reads in the front plate of chinese cheap no-name unit], it is just not electrically and mechanically strong enough.) is another disqussion. Not recommended these days anywhere, technically possible though. I read one rather amusing story of one case where old tek were powered with internal combustion engine generator, lift up to insulation stand several meters above ground (obviously with the generator) and were connected to 20kV power distribution line to measure some part of an prototype thyristor reactor. The scope were then used with long insulation pole. >:D Obviously something that hobbyist (or even majority of professionals) should not try out. Personally I don't like the mystification part involved the HV work, in the long run it leaves too much room for false information. One military explosive specialist once told that explosives are safe to handle as long as you respect them, but when you get arrogant you soon will be dead. This also apply to high voltages. |
| wasyoungonce:
--- Quote from: Electro Detective on June 22, 2017, 10:37:19 am ---It's 2017, not 1987.. technology has gone up, prices are dirt cheap, sweat shoppe labor even cheaper --- End quote --- We used ground busters in late 70's and early 80's in Airforce.....yes got a few "kicks"! :palm: |
| nctnico:
--- Quote from: dicky96 on June 22, 2017, 10:27:21 am ---I honestly don't think the way we were taught 'back in the day' was irresponsible or dangerous - I think we were just properly taught to understand exactly what we were doing, the risks involved and how to minimise them. This included using shrouded probes, a separate ground connection to the chassis (not on the scope probe) and clipping the scope probe to component lead you wanted to test, then powering up the DUT. Oh and there was nothing grounded on the wooden bench, plus it had a rubber surface mat and you stood on a rubber mat. --- End quote --- So you already know there is a lot more to it than just cutting the earth wire! Good, because many people think an isolation transformer is enough and happily ground the DUT again using their oscilloscope's ground lead. The modern day equivalent to setting up an entire isolated work environment is a CAT rated differential probe. Much cheaper and much easier. |
| Vtile:
--- Quote from: nctnico on June 22, 2017, 09:29:18 pm --- --- Quote from: dicky96 on June 22, 2017, 10:27:21 am ---I honestly don't think the way we were taught 'back in the day' was irresponsible or dangerous - I think we were just properly taught to understand exactly what we were doing, the risks involved and how to minimise them. This included using shrouded probes, a separate ground connection to the chassis (not on the scope probe) and clipping the scope probe to component lead you wanted to test, then powering up the DUT. Oh and there was nothing grounded on the wooden bench, plus it had a rubber surface mat and you stood on a rubber mat. --- End quote --- So you already know there is a lot more to it than just cutting the earth wire! Good, because many people think an isolation transformer is enough and happily ground the DUT again using their oscilloscope's ground lead. The modern day equivalent to setting up an entire isolated work environment is a CAT rated differential probe. Much cheaper and much easier. --- End quote --- .... And the differential probe is the cheapest chinese found from ebay where the isolation can be anything a common semiconductor junction included. There is also not much discussion of wallwart type PSUs or insulation properties of a random laboratory PSUs. Also potential high voltages (ie. In case of high current short at next room) on mains ground lead is hardly mentioned.. There is traps here and there. |
| Navigation |
| Message Index |
| Next page |
| Previous page |