The meter is fully cosine corrected for the angular incidence of light meaning that if you are not holding the sensor perfectly perpendicular to the light source the sensor will still read the light correctly. The sensor is stable and made of a long-life silicon photo diode. The Active Eye Digital Light Meter accurately measures to 432000 Lux. The meter's built in low battery indicator means you'll never be caught by surprise by a low-power product. It can measure grow lights or sunlight and offer 3 scales for precise readings. The meter has a convenient hand held remote sensor and a Cell Battery (Lithium 3V CR2032) is suuplied.