The essential factors for photovoltaic solar cells are illuminance, temperature and electrical load. ET 252 enables targeted testing to understand the essential fundamentals and practically relevant effects on cells and modules. Four solar cells are illuminated by a dimmable lamp array. These can be kept precisely at a selectable setpoint temperature via a regulated Peltier module. Using the included cable set, the cells can be connected in various ways via a connection board. Individual cells can be bridged, e.g. by bypass diodes, to examine differences in power loss under shadowing.