It's time to restore the 11/45.

Noel Chiappa jnc at
Thu Feb 5 12:59:30 CST 2015

    > From: Jon Elson

    > there is no part of the EUT that is at neutral potential

    > From: tony duell

    > With most 'scopes one side of the input is grounded -- you have a
    > coaxial cable with the shield connected to the 'scope case and true
    > ground.

Ah. That's the part I was missing! I (naively :-) assumed that the 'scope's
whole input amplifier would be 'floating', and the input signal would be taken
as referenced to the 'ground' on the probe, which could itself be floating.

Clearly not! (I'll have to look at the manuals/prints for my 'scopes -
Tektronix 465's - to see if they are this way. Anyone happen to know,
offhand?) Thanks!

    > In most, if not all, countries, one side of the mains is connected to
    > ground too.

Yes, in the US that's code; neutral (aka 'return') is usually tied to ground
at the main panel. (Well, at least in the state I live in - technically I
suspect that it's under state law, not Federal, but I would assume the states
are all the same, the way they are with commercial law.)


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