gEDA-user: Transformer as voltage transducer?

[Greg Cunningham]

On Sun, 2007-05-27 at 13:11 +0100, Peter Clifton wrote:
> On Sun, 2007-05-27 at 08:02 -0400, Randall Nortman wrote:
> > So now I have to figure out if I really care about those >60Hz spikes,
> > dips, and noise.  I am thinking not, so transformers should be just
> > fine.  Then again, the reference designs for these Analog Devices
> > chips just put a resistor divider between hot and neutral and feed it
> > straight in without isolation.  They use neutral as DC circuit ground
> > and derive power from the hot line, so the whole circuit is tied to
> > mains without isolation.  If I did that, I would of course have to
> > make sure that the digital interface between my measurement system and
> > the PC that captures the data is isolated, which is pretty easy.  Any
> > thoughts on that setup?
> 
> Not a bad setup, but like you say, needs careful attention to isolation
> and insulation at appropriate points.
> 
> Be careful with resistors, they have a voltage rating, so for mains work
> you may need more than one in series (in the high side of the divider)
> to avoid them failing open-circuit.
> 
> Regards,
> 
> Peter Clifton
...
see also http://www.edcheung.com/automa/power.htm
>  
> Greg Cunningham <greg at crafty.homelinux.net>