3rice I checked it with my hospital instrument and surprisingly it's aqurate exactly ...see the main phenomena is the heart rate sensor measures your heart rate in Beats per Minute using an optical LED light source and an LED light sensor. The light shines through your skin, and the sensor measures the amount of light that reflects back. The light reflections will vary as blood pulses under your skin past the light. The variations in the light reflections are interpreted as heartbeats. same oxygen sensor do ,,the blood oxygen level is estimated based on the kind of reflection, so a.) how much light comes back to the sensor b.) WHICH light comes back to the sensor.Oxygenated Hemoglobin (=blood with good oxygen saturation) has a bright red color and absorbs more infrared light.Deoxygenated Hemoglobin (=blood with bad oxygen saturation) has a dark red color and absorbs more red light. So by emitting a large-spectrum light (R and IR) and measuring the ratio of the feedback, the device can make a estimation of the blood oxygen level.
