I'd put a 10K resistor in series with each AD input.  This limits the
current into the input protection circuits to a safe value without
seriously slowing down the the conversion.  Be sure to follow Microchip's
advice on trading measurement speed for source impedance.

_____________________________________________
Lynn Richardson           | lrich@qni.com    \
Progress Instrument, Inc. | wa0znl.ampr.org  |
807 NW Commerce Drive     |  [44.46.176.3]   |
Lee's Summit, MO 64086    |                  |
(816)524-4442 F:246-4556  |                  /
---------------------------------------------

On Fri, 13 Dec 1996, Martin Larran 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
>