In the modern analytical laboratory, and particularly in the teaching and research situation, analysts are confronted with the problem of processing experimental data. Invariably, instruments are linked or have the capacity to be easily linked with microcomputers, providing the user with digitised versions of the experimental signal, which can be processed in a multitude of increasingly complex ways to extract as much analytical information as possible. In Part I of this two-part article, we show how to upgrade, and more interestingly, replace some functions and improve existing analog instrumentation using a relatively cheap data acquisition card.