Isolation transformers

[electronics-whiz]

I read something in an electronics repair book. The one thing it mentioned was using an isolation transformer. I have A power conditioner from like the late 80s i was given, it appears to be totally isolated output up to about 8A at 120V. I use UPS for my electronics, so have little use for something like what it was designed for. I have considered just recycling it or parting out, but also tempted to keep for isolation.

I didn't exactly understand the isolationg thing because something happens you touch something i would think no mater what you do you'll get a shock. That is part of why i have a GFCI on my bench so if something happens it would trip. I very rarely work on anything live, and if i do i place a meter, then plug it in long enough to get a reading. Occasionally if i'm fixing something i'll leave the cover of until i get it working for sure.

Just looking for thoughts and better explanation of benefits of isolation.

[mariush]

An UPS doesn't provide isolation, unless you unplug it from mains or it's a more expensive online ups.
Most UPSes connect system straight to mains and just use relays to disconnect and switch to battery when there's a fault. 

Only online UPS systems usually run all the time through two transformers, basically like they're running all the time from battery.

[Sigmoid]

Just looking for thoughts and better explanation of benefits of isolation.

As far as I understand, an isolated (floating) circuit won't shock you, unless you short circuit something within the floating system. Connecting any one terminal (hot OR cold) to earth ground should, ideally, yield no current flow.

[Monkeh]

An UPS doesn't provide isolation, unless you unplug it from mains or it's a more expensive online ups.

Or it happens to provide isolation without being online or unplugged.

[mmilejski]

Connecting any one terminal (hot OR cold) to earth ground should, ideally, yield no current flow.

Before you connect any of the terminals to earth ground there is no live or neutral, the one you short to ground becomes neutral, and the other becomes hot, unconnected they are just floating.

[electronics-whiz]

OK i guess that makes since since circuit is not complete. I figured though if you have something E.G a 120V output from isolation source, you touch something it would still be higher than ground so you would get a shock. That does make since though that it wouldn't because you kind of cut path in 1/2. Still could get something though if torched 2 lines, or hot and chassis. I believe the conditioner the grounds are linked between in and out, i don't know for sure that would make it a true isolation transformer. I always thought that it was the separation of the standard power circuit. Separating ground though seem like could be a good idea too though.

I was referring to using UPS for computers, etc. i guess place i got from had on an old server, now i just use UPS for all that. I have thought about that too using UPS as isolator unplugged.