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Floating Scopes
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Electro Detective:

--- Quote from: Vtile on June 22, 2017, 09:59:00 pm ---
--- 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.

--- End quote ---



..and the cheap or overpriced differential probe is still connected to the BNC socket,  :--

which is connected to the mains neutral earth/ground utility power, that has lots of energy available for unlimited free fireworks   :clap: :scared:

An isolation transformer is a must, it can only supply so much rated current/voltage and isolates you from the incoming line,

and always a better bet than only relying (PRAYING) that some overpriced sealed piece of plastic sweat shoppe crafted 'differential' probe
won't suddently become 'indifferent' and die, arc or bridge internally,
or after a drop or bump some loose internal silly tiny self tapping screw or solder blob gets the party going early  :clap:  :-BROKE  :-[   

Please   :palm:

Fungus:

--- Quote from: Electro Detective on June 22, 2017, 10:41:49 pm ---..and the cheap or overpriced differential probe is still connected to the BNC socket,  :--

which is connected to the mains neutral earth/ground utility power, that has lots of energy available for unlimited free fireworks   :clap: :scared:

--- End quote ---

If your neutral/earth are tied together you need to revise your wiring.

PS: Your 'scope has a transformer in it, too. I guess all 'scopes are "floating" to you, right?

Electro Detective:

--- Quote from: Fungus on June 22, 2017, 10:47:26 pm ---
--- Quote from: Electro Detective on June 22, 2017, 10:41:49 pm ---..and the cheap or overpriced differential probe is still connected to the BNC socket,  :--

which is connected to the mains neutral earth/ground utility power, that has lots of energy available for unlimited free fireworks   :clap: :scared:

--- End quote ---

If your neutral/earth are tied together you need to revise your wiring.

PS: Your 'scope has a transformer in it, too. I guess all 'scopes are "floating" to you, right?

--- End quote ---


I don't know what planet you're from but here in Australia ALL neutral buss bars are linked to the earth buss bar in the switchboard.

Some oscilloscopes do have switchmode power supplies last time I checked (and millions of other scope owners)

Anything else?  :-//

Hey,  :-DMM   wanna talk about the latest Flook 87V ?  >:D

wasyoungonce:

--- Quote from: Fungus on June 22, 2017, 10:47:26 pm ---
If your neutral/earth are tied together you need to revise your wiring.....
--- End quote ---

I think he means Multiple Earth Neutral (MEN).  Used a lot these days.


Electro Detective:

--- Quote from: wasyoungonce on June 22, 2017, 10:54:05 pm ---
--- Quote from: Fungus on June 22, 2017, 10:47:26 pm ---
If your neutral/earth are tied together you need to revise your wiring.....
--- End quote ---

I think he means Multiple Earth Neutral (MEN).  Used a lot these days.

--- End quote ---

yes correct,  :-+  MEN relates to the TN-C-S system here

He knows what I meant, he also thinks he's a moderator here too  :-DD

Just question where the current Fluke 87V might be made/assembled and you get threatened with a ban  :scared: :scared: :scared:

after a few of them try gang up like schoolyard bullies  :-*  and cause an 'investigative' post to get locked   :--
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