The principle of nail oximeter
Due to the red blood cells in the blood, two types of hemoglobin, oxyhemoglobin (HbO2) and reduced hemoglobin (Hb), have different absorption capacities for red light (660nm) and infrared light (910nm). Reduced hemoglobin (Hb) absorbs more red light and less infrared light. Oxygenated hemoglobin (HbO2), on the contrary, absorbs less red light and more infrared light. By setting red LED and infrared LED lights at the same position of the nail oximeter, when the light penetrates from one side of the finger to the other and is received by the photodiode, a corresponding proportion of voltage can be generated. After processing by the single-chip microcomputer, the output results are displayed on the LCD screen.