The development and use of a computerised data acquisition system for the study of the temporal variations of the plasma parameters in pulsed Helium and Argon afterglows using a single Langmuir probe. The controlling software and electronics were developed to a level that enabled plasma characteristics to be analysed and presented on a number of output devices. A novel technique was developed to pulse the probe which limits plasma depletion during the measurement process. A non - Maxwellian electron energy distribution was found at early times in the afterglow with two distinct 'temperature' or energy groups. The 'faster' or 'hotter' electrons 'blended' with the cold group at late times in the afterglow, giving a single group which could be characterised by a unique temperature. This temperature was seen to approach room temperature in the temporal limit. The decay of bulk electron temperature and density was modelled using the diffusion equation and reasonable agreement was found to exist between the theoretical and experimental data.