It might be argued that the resolution of the AD converter is
not really a problem since the error from resolution will
average out over time. However, it is not practical with a
meter that is not measuring accurately in every input signal.
Especially for verification purposes, with a stable source
applying current and voltage, it is necessary with a resolution
well below the accuracy requirements which is once again
0.01% of range. 16 bits is equal to a resolution of
approximately 0.0015% of range, which is a minimum
requirement for resolution. A resolution of 18-20 bits or more
is preferable, especially if the meter is supposed to measure
both positive and negative energy flow and hence measure
both positive and negative current.