Lux, or ambient light, is measured by ActiGraph’s ActiSleep, ActiSleep+, ActiTrainer, GT3X+, and our new wireless wGT3X+ and wActiSleep+ devices. Ambient light may affect subject sleeping habits and thus is a useful tool in analyzing circadian rhythms and sleeping patterns. Lux data is stored once per epoch. For GT3X+/ActiSleep+/wGT3X+/wActiSleep+ devices, Lux data is stored once per second. When converting a GT3X+ raw file into an accumulated *.agd format with epoch lengths greater than one second, the lux values for that epoch are averaged.
The ActiTrainer, GT3X+, and wGT3X+ devices are capped at a maximum value of 2500; the ActiSleep, ActiSleep+, and wActiSleep+ are capped at 6000:
The wGT3X-BT device is capped at a maximum lux value of 5000 and the wActiSleep-BT is capped at 6500. The new GT9X Link device does not have a lux sensor.
An estimate of industry accepted lux values is shown below:
Lux Level Interpretation Comparison
1 Twilight 5 Minimal Street Lighting 10 Sunset 50 Family Living Room 80 Hallway 100 Very Dark Overcast Day 320 - 500 Office Lighting 400 Sunrise/Sunset 1,000 Overcast Day 10,000-25,000 Full Daylight 32,000-130,000 Direct Sunlight
Note that these levels are only estimates and are not meant for exact interpretation of the light detected by the device. Lux values reported by ActiGraph devices are only intended as a general guideline for average light intensities.
You can also refer to the attached Data Sheet for more information.
Please also refer to the following Wikipedia page for more information on Lux values:
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