Abstract: The invention concerns rapid, precise analog-to-digital converters (ADC). To achieve rapid conversion, the invention uses a fast though imprecise ADC, whose numeric output value is used to address a memory location in a first memory block containing correction values. Calibration measurements are inserted between conversion measurements, the time intervals being sufficient to establish a stable reference voltage at the output of a generator. The switching between conversion and calibration measurements is made using a switch. During calibration, the differences between the conversion results and the real values are written into a second memory block at addresses corresponding to the numeric output values of the ADC. Means of control and calculation enable sequencing and switching of the roles of the calibration and correction memory blocks at the end of a calibration.