An analog-to-digital converter (ADC) controlled in a manner to increase its precision. The signal to be digitized is one input to an analog signal summing means whose output is the input to the ADC. A stepped or dither voltage signal is applied to the other summing means input during each analog signal sampling period of the ADC. The dither voltage steps are equal to the voltage equivalent of one ADC count plus 1/N where N is the number of steps per ADC count chosen to obtain a desired degree of precision in the digital signals that are output by the ADC. The dither voltage step that is combined with the current analog signal sample in the summing means amounts to displacing the sample in steps within each count of the ADC. The ADC converts each combined signal during a sampling interval to a succession of binary digital values which are summed. The result of the summation is a binary number having a value that corresponds more precisely to the true value of the analog signal samples than would be the case if they were converted directly by the ADC.