> I am a student using a PIC 16F877 in a project and would like to read an
> analog input from an accelerometer setup that varies its output
> from 0-11v.
> This voltage is put out by a signal conditioner made by the
> manufacturer of
> the accelerometer so I have little control over it. Now I know there are
> vref pins I can use, but some analog inputs will be in the 0-5v range and
> I'd rather not lose precision on them by changing the voltage reference to
> accomodate the range of the accelerometer. How can I step down
> the 0-11v to
> 0-5v? Can I use two high high value resistors to divide the
> voltage down? I
> am considering that approach but am afraid of the effects temperature will
> have on the resistors and thus the readings, since I am told that
> resistors
> are prone to drift with temperature. The accelerometer will be used
> outdoors, inside a model airplane, where temperature could vary
> considerably. Also, having little background on EE, I am not sure
> what other
> effects might follow from using the resistors. Any thoughts or other
> approaches? I know little about EE, so bear with me if this is too basic.

        The resistor approach is easiest, however you have to be careful. What is
the output impedance of the accelerometer? Remember that the input impedance
of a PIC analog input isn't all that high, so you have to put that into play
as well.

        As for the temperature variance that will have an effect, you'll have to
research what type of tolerance you need and what type of resistor gives you
that tolerance. If you can't find one then things become much trickier. TTYL

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