The Fusion Brain's analogue input ports are 10bit.

This means they read values in and convert them to a digital signal that uses 10bits of information to store the aquired data. Because digital logic is binary based, this means there are 2^10 - 1 possible digital values for any given range which works out to be 1023. Our range is 0v to 5v, so 5v/1023 means we have a minimum step of 0.00488v. So this means the Fusion Brain can tell between 2.500v and 2.505v but inbetween it will round up or down.