Explainer · updated 2026-10-06
What smart-ring sensors actually measure
Separate direct signals from app-derived scores.
Definition
PPG observes reflected light, temperature sensors observe local trends and accelerometers observe motion; named scores are inferences.
Bottom line
The ring does not directly measure recovery, stress, sleep stage or fertility. It combines signals and context into estimates.
Optical sensing
LEDs and photodetectors derive pulse timing. Motion, fit, contact and circulation affect the signal.
Temperature and motion
Finger temperature is not core temperature. Motion supports step, activity and sleep estimates.
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Not medical advice. Contact a qualified clinician about symptoms or concerning readings.