1. A method of calibrating a redundant number system analog-to-digital converter (RNS ADC), wherein the RNS ADC includes N analog converter reference elements, each of the analog converter reference elements is associated with a weight in a weight vector, and N is an integer greater than one, the method comprising: successively approximating each of M distinct analog input signals twice to generate M respective pairs of successive approximation converter reference element vectors, that correspond to digital approximations of the input signals, wherein M is a positive integer; and using differences between converter reference element vectors of each of the M respective pairs to determine a final weight vector.