In addition to temperature measurement, the MS-TL can provide a general indication of light level. The maximum value of 5 volts corresponds to the light intensity of a 100-watt light bulb at a distance of 15cm, while a zero volt reading indicates total darkness. To the amount that Vcc falls below +5 volts, the absolute maximum light level will become ambiguous. Most often this is not a concern since the device is intended to indicate light present, or no light present.
Note: There is a hole in the top of the enclosure that is directly over the light sensor. Care should be taken to keep this opening clear and facing the light source to be monitored.