What about using an Energy Meter chip from ADI or
Cypress?  If you just want to measure voltage, its a
resistor divider, and SPI interface.  With the
isolation between the chip might be looking around the
same cost.  There is also an App note from Microchip
on  using the PIC for energy monitoring AP939.  


--- Jinx <joecolquitt@clear.net.nz> wrote:
> 
> > I didn't look at the part itself, but whats the
> cost of this
> > device and the associated components around it ?
> 
> Alan
> 
> About NZ$10. 90% of that is the RS price of the tx.
> I'd be
> shopping around of course, but at the prototype
> stage I'll wear
> the odd extra $ for convenience sake. Got something
> in mind ?
> 
> > We tested some small transformers in this role a
> few years ago.
> > They worked fine(ish) at 230V but we needed to go
> as high as
> > 270 or 280. At this voltage they started to
> saturate and the
> > output waveform became very distorted
> 
> Richard
> 
> I'm more concerned about safety/reliability at the
> moment. As
> long as the tx keeps going (in a repeatable way
> across all units)
> it wouldn't be too hard to characterise the DC
> output of a full
> bridge against input AC. Assuming that the AC input
> could go
> as high as 280 at times, adding a series component
> could obviate
> saturation if necessary
> 
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