A data acquisition system and method are described that may be used with various spectrometers. The data acquisition system may include an ion detector, an initial processing module, and a spectra processing module. The initial processing module is provided for receiving, sampling, and processing ion detection signals received from the ion detector, and for supplying processed signals to the spectra processing module. The initial processing module includes a horizontal accumulation circuit that combines a fractional number of adjacent samples of the ion detection signals into bins. The number of adjacent samples to combine into bins may vary as a function of: (1) the time of arrival at the ion detector corresponding to that sample; (2) the mass corresponding to that sample; (3) the resolution corresponding to that sample; and/or (4) an operational mode of the spectrometer. The spectra processing module receives the processed signals and generates spectra.