Space industry is changing very fast since the last few years. With the explosion of the information society a lot of new players have come into the space market. Thanks to them, customers are demanding better specifications and lower prices. This situation is pushing most of the companies to explore new ways of making satellites. When it comes to components, traditional rad-hard parts are progressively been replaced by commercial off-the-shelf (COTS) ones in a lot of applications. In order to have an excellent time performance in the Single Event Latch up (SEL) tests, a lowcost and high-flexibility testing unit has been developed by Thales Alenia Space in Spain called CLARK (Control de Latch up Ajustable y Regulable para Kits de Evaluación).