Thanks for the idea! I may need to ask you a follow-up
question later about "a 12-bit +-10volt AtoD (resolution =
10/(2^12))." I'm not quite sure what this means.Diane
Well suppose we set up the following mapping table:
0000 0000 0000 = 2^0 -1 --> -10V (all bits off)
. . . . . .
. . . . . .
1111 1111 1111 = 2^12 -1 --> +10V (all bits on)
Thus, the resolution (the least detectable change in voltage over (-10,+10)) is
20V/(2^12 -1) = 4/819 V = 0.004884 V
Note, this is not what you have given above, and clearly, the resolution
could be improved (smaller) for the
same 12-bit A/D if the input range was decreased.
In general, the resolution, dV, of an k-bit A/D over an voltage range, R, is defined by:
dV = R/(2^k -1)
However, be aware that there are k-bit A/D converters with
a sign bit position, and this equation must
be modified. Also, this resolution is for an "ideal" A/D converter.
--Virgil :-)
