This thesis investigates a personal computer based radiometer system which uses the photocurrent produced by a silicon PN junction (SJ) as a solar radiation transducer. A laboratory prototype for the radiometer hardware is designed and implemented using two types of silicon PN junction as solar radiation transducers.. The use of such commercially available low - cost sensors together with the various facilities offered by the PC results in compared with other equivalent systems. The developed prototype has eight input channels, although only four channels are considered in the present work. The other channels are left spare to the user for other meteorological parameters. The system is also provided with a programmable timer to determine the time of reading instants and to ensure automatic ON and OFF switching of the entire system components according to the time of sunrise and sunset respectively. The performance of the complete prototype radiometer is assessed experimentally by an instantaneous comparison made between Apply black and white pyranometer (B&W) and the SJ from one side, and the precision spectral pyranometer (PSP) and SJ from the other. The comparison shows that the SJ has 4 distinctions, high time responsively (about one nanosecond), better cosine response than B&W, low cost and smaller volume than that of the B&W and PSP.