How does ZeFit2 calculate my sleep quality? August 11, 2015 11:55 Updated Our 3 axis accelerometer sensor determines whether your are in a phase of light sleep, deep sleep, or awaken. Related articles How do I activate sleep mode? How does ZeCircle2 evaluate my sleep quality? What are the patterns of Caller ID? I have difficulties to connect my device to Huawei P8 lite How do I activate sleep mode on my ZeFit³ ?