Alvaro,

Sounds like you may be using standard 'automotive' sensors,
which are powered from a nominal +5V supply.

If so, the output from these sensors is usualy ratiometric
(the output sensitivity is proportional to their +5V supply voltage).

Usual automotive practice is then to use an AD with sufficient
resolution (say 10 or 12 bit) and use the 5V sensor supply as
your AD reference voltage. Your sensor readings will then track
any variation in the 5V supply/refence due to their ratiometric
characteristic. No need for expensive reference sources.

You don't say what sort of sensors you are using, but most
automotive sensors only have an accuracy of +/-3%, so there
is no merit in cranking up the AD resolution way beyond the
basic accuracy of the sensors.

regards, Richard Golding

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