The measurement of solar radiation is required in the various fields of research, including agriculture, astrophysics, biology, forestry, meteorology, building construction and energy assessment. In order to measure the radiation, various types of instruments are used. Pyranometers are applied to measure the global, direct or diffuse radiation. Depending on the type of their sensors, they are classified as thermal or photovoltaic pyranometers. In the present work, the characteristics of three instruments - the CM11 - Kipp and Zonen, Licor 200SZ and Matrix 1G - are studied in detail. The results show that by applying cosine, air mass and clear sky index corrections, the cheaper PV pyranometers can yield comparable results to the expensive thermal pyranometers. The results are much more convincing under clear sky conditions than under overcast conditions.