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?

So I think you are saying you want to measure the nominal 48V difference
between two signals that could be floating with respect to the PIC ground?
Dividing down one of the signals to the PIC ground and ignoring the other is
definitely not going to work.

What is the common mode range of the two signals?  How much leakage can be
allowed between the two grounds?  How fast must the PIC respond?


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