All measuring components including the integrating sphere, three IPVs and both Maxim sensors are mounted on a measuring board. To assure an accurate and reliable measurement, all these components should receive uniform light with the same quality. Consequently, the testbed should be designed to provide a homogeneous light intensity in each horizontal level with minimum deviation. A main reason causing heterogeneous light intensity (and quality) is the reflection from walls. Thus, interior surfaces of the platform are covered with rippling black sponges. Form, material and color of this cover helps providing a more homogeneous light intensity on horizontal levels by reducing reflections.