Martin:

Putting an op-amp with single supply of 5v will not give you the complete 0
to 5 volt range output.  I would stick to the +/-12V and protect the PIC
with a 5.1V Zener Diode at each analog input, anode to ground and cathode to
the input.




At 07:29 PM 12/13/96 -0800, you wrote:
>Hi people!
>
>        Here is my problem: I4m using the 16C71 with the four A/D chanels to
> measure magnetic field, temperature, etc. The supply is 5V and also the
>ref.
>for the A/D. As I use a symethrical(12,-12) PS for the Op. Amp. of the
>sensors,
>if something goes wrong with some sensor(like wire breaks), the Op.Amp
>will
>saturate blowing the A/D. So which is the best way to prevent this?
>        For now I4m using another Op. Amp.(Av=1) with single supply of 5V, to
>cut
>the "overvoltage" but I loose many mV.
>        Sure there is another simpler and more efficient way of doing it!
>
>        Thanks a lot
>
>
>
>
>                                                        Martin Larran
>
>
____________________
Gonzalo Palarea
chalo@infovia.com.gt