Really big resolution on a small input voltage range

Hello,

I have a accelerometer but the accelerometer has a offset of 1,5 volt. And with 1G it has an ouput voltage from about 1,9 volt. I would like to set the full resolution ( 10 bit ) to the input range from 1,5 volt to 2 volt. I already used the analogReference function but I would like to increase the underbound. It is also possible to use first a voltage divider but resistors aren't precies enough for this job.

I use this accelerometer:

http://www.tiepie.com/en/products/Accessories/Miscellaneous/Accelerometer_TP-ACC20

I know, but in the holiday I work there and make this accelerometers by my self. So I diden't pay that!

The only way I can see to get 10 bits from your .5v range is to condition the signal with an opamp or two to give an offset and amplification.

Opamps aren't my bag though so I can really offer a circuit. Amplifying is easy, offsets I don't know about.


Rob

Just a thought, but you might try two small diodes in series with the output of your device such that with no acceleration the input to the arduino might be ~.1v and ~.5v at the high end.

Run your signal thru a summing amplifier to add some DC offset and enough gain to get full resolution.

http://masteringelectronicsdesign.com/how-to-derive-the-summing-amplifier-transfer-function/

Pretty straightforward.