This meter allows you to track the decrease in output of your UVB lamps over time. Simply point the round sensor on the top of the unit at the UVB source, hold down the button and read the LCD screen (UVB level is displayed in microwatts per square centimeter). Remember that readings will vary with distance, so make all measurements from the same distance (12. for example). A 9-volt battery is included already installed in the unit. Eventually the battery indicator "Batt" will come on, indicating need for replacement of battery. Always replace battery when indicator comes on in order to maintain meter accuracy. Wear eye protection when checking UV lamps (e.g.: UV-block eyewear). Allow lamps to warm-up prior to taking readings (at least 5 min). Do not use meter to compare different type lamps, due to their different spectral power distributions. Although higher output lamps will read higher than low output lamps, the readings are relative rather than absolute. Do not subject the meter to extremes in temperature, humidity, shock or dust. Use a dry, soft cloth to clean the instrument. Keep sensor free of oil, dirt, etc. Keep sensor from light when not in use.