On Sunday, 12 April 2015 23:58:10 UTC+1, Cursitor Doom wrote:
On Sun, 12 Apr 2015 10:52:08 -0700, tabbypurr wrote:

On Sunday, 12 April 2015 18:37:09 UTC+1, Cursitor Doom wrote:
On Sun, 12 Apr 2015 03:47:08 -0700, nt wrote:

Well you can't really blame me. Your description is a bit vague, after
all: "string of 3w resistors, bit of coathanger, bit of polystyrene."

With your experience/expertise I'd expect you to have no difficulty
seeing how that works. Ditto for anyone that would know how to use such
a thing safely.

I think I can see where you're coming from with your string of resistors,
but the role of the coat-hanger and poly remains unclear. I'm not a mind-
reader.

OK. A stick of expanded polystyrene makes the insulated handle and the mounting base for the series string of resistors & coathanger offcut. The latter is of course the conductive probe. A 2nd ground wire is wrapped round the poly between resistor string & handle area as a 2nd line of defence against insulation breakdown - this needs grounding of course. The whole is tested to well above working voltage before use. An easy way to do that is hook it up to a CRT anode.

Anyone doing this has to understand the engineering issues, getting it wrong can kill.


A low impedance load can hardly be a gold standard for measuring a
normally high impedance voltage.

I was of course referring to the gold standard for moving coil meters.

in terms of input impedance that would be fet buffered meters


NT