> =A0If you run the 10 bit A2D with external reference voltages of around
> 1.54 volts, you'll still get around
> =A01.5mv resolution.

For extra points (and headaches) mapping  only the top half of  tht
range onto the ADC takes you to better than the originally specified
nominal 1 mV, notionally at least.

Using a PIC with a 12 bit ADC is probably worthwhile.

Note that somebody mentioned dithering to get additional resolution.
Whether you also get extra accuracy depends on other factors. If you
add +/- ha;f a bot of gaussian noise it will sometimes move signal at
the intermediate point between 2 bits up or down so the ADC reads it
at one of two bit values. The ratio occurrences at value N or value
N+1 relate rto its actual distance between the two states. In practice
with somewhat random noise and good enough other components you can
get an extra bit or two this way and maybe more with luck and skill.

Simplistic example. If random noise is added to a signal and it reads
145 mV 60% of the time and 146 mV 40 % of the time then actual voltage
MAY be about 145.4 (not 145.6) mV. Take care when arttempting to apply
this magic. It does work, but ... .


 Russell

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