I would like to consider the feasibility of building an AC power meter 
(watt*hour counter, power factor, etc)
-- without the use of a current transformer. The reason I believe this 
would be useful is because a small resistor can be used in place of a 
relatively large and more expensive magnetic device.
The sticky-note schematic is like this:

    ------------------->
AC -----[R01]---------> DUT
       |         |
      [220k]   [220k]
       |         |_____
       |-------- | ----[Interface]---:isolation:---->
      [1k]      [1k]        |
gnd___|_________|__________|


So my question is about isolation. I assumed I would use a difference 
amplifier at the [Interface] section, but I don't know if I can put in 
an ADC powered by an unisolated supply here without seeing things blow 
up. I also need to measure the voltage at the post-current-resistor 
divider with another ADC channel [this is probably a PIC project]
I guess I need some guidance as to where the isolation should go, while 
keeping it as simple as possible.
-- 
Martin K
http://wwia.org/sgroup/biofuel/
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