Student Digital Lux Meter w/Carrying Case
by American Scientific

Useful for checking the level of luminance (Lux), this digital lux meter is perfect for students. With a range of 0-50,000 and 0-100,000 Lux, which is selectable via slide switch on the meter, it is capable of highly accurate and rapid display of the level of luminance in your area of measurement. The Lux Meter has a sampling rate of 0.4 seconds, and features a large and easy to read digital LCD display. A 9V battery is capable of powering the unit for approximately 200hrs, and an operating manual and padded carrying case to protect the unit when it is not in use are included.

A Lux is a unit that indicates the density of light that falls on a surface. Average indoor lighting ranges from 100 to 1,000 Lux, and average outdoor sun lights about 50,000 Lux. Light is necessary for the development of plants, as a sufficient contribution of light is needed in order for the photosynthesis process to proceed. By supplementing light by means of lamps, the photosynthesis process can continue even at night, unhindered.

Because the human eye is sensitive only to blue, green and red light, in calculating the Lux falling on an object, only the light that the human eye sees will be counted. If infrared light falls on an object, the Lux will be counted as zero, sinze our eyes see nothing. Mathematically, a spectral weighting function becomes convolved with the actual illumination spectrum to calculate Lux exactly. This is the formal definition of Lux, an unusual unit of measurement.

Still, Lux can be thought of as a way of measuring light in terms of what our eyes perceive. One Lux is equal to one Lumen per square meter. One footcandle is equal to 10.76391 lux. A footcandle is essentially the amount of light that a standard birthday candle generates from one foot away.