Another simple solution:

Use the hall effect current sensors from Allegro and
convert voltage to current, and read in the PIC A/D.

The sensor are completely isolated from the signal.


Best regards,

Rubens


At 05:58 27/3/2007, you wrote:
>I hate replying to myself :)... but...
>
>Forrest W Christian wrote:
>
>>As a result, the needs may be able to be redefined such that everything must be ground referenced.  However, being able to measure voltages where the input is below Vss is important  since one of the main applications for this device is to monitor battery utilization.
>>  
>>
>I do realize that this specific case (I.E. force everything to be 
>"ground" referenced, and allow +- voltage input) is easily accomplished 
>with an opamp level shifting the voltage upward, and scaling accordingly 
>(So +-5v maps into say 0-3.3V, where 0V becomes something like 1.65V).   
>Of course more novel and less expensive solutions to this case are welcome.
>
>(And of course, ideally I would love to not have to ground reference 
>anything).
>
>-forrest
>
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