Somewhat OT Knob & Tube wiring (was Re: Power and the RA82)

Roger Merchberger zmerch at
Tue Jul 12 14:51:26 CDT 2005

Rumor has it that Vintage Computer Festival may have mentioned these words:
>On Tue, 12 Jul 2005, Curt @ Atari Museum wrote:
> > Still burns and leaves the God-awefullest metal taste in your mouth when
> > you get hit with a ring surge,    You sure its AC?   Doesn't make sense,
> > but voltage on my meter would jump up from 48-52vdc to around 78-80vdc
> > on the DVM
>Yes, it's AC.  That's why it hurts.  DC would feel strange perhaps but not
>like AC.  The reason you saw voltage at 80VDC is because your digital
>meter samples slowly.

Or -- some meters when set to DC and fed AC will measure the RMS [kinda 
DC-equivalent value] voltage of the AC...

100+V AC * .707 = 70+V DC.

The equation for figuring RMS voltage on sine-wave AC is:

(I've seen up to 110V AC myself [more on hand-cranked military handsets], 
so that would get awfully close to the 80V the OP saw...)

Just a thought,
Roger "Merch" Merchberger

Roger "Merch" Merchberger   | Anarchy doesn't scale well. -- Me
zmerch at         |
SysAdmin, Iceberg Computers

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