At 10:33 AM 8/17/01 -0700, you wrote:
>I am trying to figure out a way to measure a DC voltage that ranges from
-0.9V to +12.5V.  I ideally would like to just add 1V to the signal, and
then use a voltage divider to get it to the 0 to +5V range of a PIC.  How
do I condition the signal???
               +5
               |
              [R2]
in             |
o-----[R1]-----x-------------> pic
               |
              [R3]
               |
               0V

Try R2 = 100K
 => R1 = 18K
 &  R3 = 7K2

You can scale these equally to get close to standard E-96 1% values, just
be careful
about the source impedance looking back from the PIC pin (see the data
sheet for the maximum,
based on leakage), and the input impedance of this circuit is about 25K
looking into the
"in" node, with the values show.

Best regards,
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.