Andy,

 Bias the voltage into the A/D with an Op amp so that at zero degrees, the 
A/D sees 3.6 volts.  That will translate the 0  to  -3.6 volts as 3.6 to 0,
and 3.6 to 7.2 will represent 0 to 3.6 volts.  

Regards,

Jim



> Hi,
> 
>  
> 
>    Here's my problem.  I've got a sensor (I didn't get to pick it, so
>    I'm
>stuck with this) which outputs a voltage between -3.6 and +3.6 volts. 
>The voltage correlates to the orientation angle of the sensor.  Zero
>voltage indicates that the sensor is level.  The angle from zero is
>reported as a voltage (60 mV/degree).  Although angle measurements out
>at the voltage limits are interesting to me, I'm most interested in
>getting good voltage readings when the sensor is near zero degrees.  I
>figure a 14 bit A/D converter will get me the resolution I need, as long
>as I scale the sensor voltage to relatively near the full scale range of
>the converter.
> 
>  
> 
>    So here's my question/problem.  I don't know how to handle the
>    negative
> voltage with an A/D IC.  I know it is possible to read it (for example,
> an Omega Digital Transmitter can read it), but I haven't been able to
> find any sources (electronics textbooks, web searches, etc) that can
> tell me how to design my own circuit to process this voltage when it
> goes negative, as all the converter data sheets I've read only allow
> one to convert a voltage between ground and Vref.. There's got to be a
> simple solution to this problem, but my EE class is about 20 years in
> the past, and I've had no luck tracking down a beginner book which
> clues me in.
> 
>  
> 
>    Can anyone help a clueless newbie out?  I'm not looking for a
>    complete
>solution, just some pointers to get me going in the right direction.  If
>anyone has an electronics primer book they'd recommend, I'd be
>interested in the title of that too!
> 
>  
> 
>  
> 
> Thanks,
> 
>  
> 
> Andy
> 
>  
> 
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