BS EN 60904-3:2008 pdf free.Photovoltaic devices - Part3:Measurement principles for terrestrial photovoltaic (PV) solar devices with reference spectral irradiance data. BS EN 60904-3 describes basic measurement principles for determining the electrical output of PV devices. The principles given in this document are designed to relate the performance rating of PV devices to a common reference terrestrial solar spectral irradiance distribution. 3...