A fundamental factor in any artificial testing instrument is the unit's capability of accurately reproducing the environment to which the materials will experience in their end-use application. Using a sophisticated modeling system the spectral power distribution of sunlight is critically defined and characterized. Once the defined spectrum is established a correct artificial light source / filtering system providing the characteristics desired can be selected. Several laboratory based solar radiation sources which are commonly used in simulating sunlight each with advantages and disadvantages are compared. In the comparison basic and advanced solar radiation measuring and monitoring systems are employed.