Experimental results of a single probe method were recorded as digital data and calculated plasma parameters such as electron temperature and electron density by a personal computer. Data of current voltage characteristics obtained by Langmuir probe in positive column plasma of air glow discharge were digitized by a digital oscilloscope or a data-logger. Availability of these digital processing systems was compared with derivation of plasma parameters by analog circuits system. Digital measuring systems showed good performance than analog system in some respects, speed up of calculating process and making figures of experimental data. But there exist some problems to be cleared that translation of stored data to general type, reduction of noise added in digitizing process, optimal decision of space potential, sufficiently smoothed numerical differentiation to calculate electron energy distribution function by second derivatives.