The ISP 2000 integrating sphere from Instrument Systems (Munich, Germany) has been specifically designed with a diameter of 1.9 meters to facilitate precise measurement of total radiant power and luminous flux of lamps, luminaires, and large LED modules. The ISP 2000 is equipped with an auxiliary lamp to compensate for self-absorption and a temperature sensor to monitor the thermal conditions of the interior. A rail-mounted sliding mechanism delivers light-tight closure for the ISP 2000 and permits the sphere to be opened easily for quick access to the interior.