A relatively simple digitizing interface for use in chemical relaxation experiments is described. It is possible to sample by repeating the experiments and adding the data in a small on-line computer. This technique has considerably improved the accuracy obtainable in relaxation experiments as well as the speed of data acquisition. The relaxation data, which are corrected by the computer program for superimposed exponential decay processes of small amplitude, are available immediately after the experiment. By integrating the analog signal before digitization, nearly optimal electronic filtering is achieved. The technique has been extensively used in the pressure-jump technique but is applicable also to related methods. An example for the application to signals which do not change exponentially with time illustrates further possibilities of the proposed technique.