The Milwaukee Instruments Lux Light Meter SM700 measures aquarium lighting intensity. It's a great tool for testing the intensity of your lighting system and determining when the bulbs need changing. Product Manual (pdf format in new window) Settings for 0.000 - 1999 Lux, 2000 - 19999 Lux or 20000 - 50000 Lux. Range setting Manual through key buttons Accuracy: ± 6% of reading ± 1 digitPeak wave length: 560 nmSensor type: Silicon PhotodiodeSensor sensitivity: 100 scotopic LUXSensor stability: ± 2% change per year (in the first two years)Battery/Life: 1 x 9V/150 hours continuous useEnvironment: 0 to 50°C; RH 95%