Re: hot scope leads?

Phil Allison wrote:
"Andre"


! Never connect the ground side of a scope _mains_ lead to anything....

Andre Schmeets


** This sounds like * VERY BAD * advice.

Generically lifting the ground of a scope is indeed a Bad Thing.

Much better example advice is to use, say, a differential probe (if you
can afford one!) or two channels in difference mode (even these
approaches have their disadvantages and limitations.)

When working with high-current supplies there are very real dangers
associated with the "safety ground" on test equipment. The current of a
filament transformer for a big rig can, for example, easily melt the
ground wiring inside the test equipment or inside the wall, which is
usually only sized for AC fault currents (say 15 or 20Amps). This is
particularly nasty because everything may seem to work afterwards but
you are left with NO ground protection.

A non-grounded scope is a *lethal weapon* sitting on your bench.

We have lots of similarly lethal weapons all over our benches, for the
most part, so I'm not fundamentally opposed to isolating ground to a
scope when done wisely and safely.

Tim.

.

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