LTH

Light
The light sensor in the adapter returns values from 0 to about 1100 based on light intensity - it does NOT return any standard measure, and the actual readings vary based on the opacity of the label applied and so on. It can be used to easily sense that a room is brighter or darker. For example, you can use it to turn security lights on when the sun goes down - or to turn off room heaters and computer displays when the overhead lights are turned off, indicating that the room is not occupied.
Note: These are simple, low-cost "light intensity" sensors that are intended to be used for a wide variety of applications. However, they were never intended to measure the lux of a particular scene. For this reason, we're not able to provide a formula to convert light intensity to lux.
You could not use it (for example) to test that a workbench has an exact luminous intensity of "X" cd/m2. If you require such measurements, you should use a standard light sensor with a 0-10v or 4-20mA signal in a AIO adpater.
Also note that the duration of the actual light detection is short, so it works best with either sun light or non-flickering incandescent or DC-powered halogen lamps. Measure light with standard fluorescent light will result in the light value varying over a range of values (many percentage points). This does not prevent your system from detection 'the room is light' or 'the room is dark', but you will need to accommodate this variation with a hysteresis or dead-band calculation.