Alan,

If you'll use an opamp configured as a differential amplifier you ought 
to be able to isolate your circuits as well as, if you set Rf less than 
Rin, the voltage attenuation you need.  TI has a good opamp tutorial at 
their web site if you need to review or there is Walter Jung's "The IC 
Op-Amp Cookbook," which is always handy to keep around.

REB

alan smith wrote:

>I have a design where I have a 48V input that I
>monitor with the PIC, but the ground for this is
>isolated from the rest of the circuit.  The 48V goes
>thru a resistor divider to be in the range of the PIC
>(100:1) and I just need to know if its within a range,
>not looking for accuracy.  So, since the source is
>isolated from the ground that the other resistor is
>tied to, will I see any problems, or better to tie the
>divider across the 48V and the isolated ground?
>  
>


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