How Blood Oxygen is measured by Apple Watch series 6?

 According to Apple The Apple Watch Series 6, the optical Heart sensor is redesigned to add Blood Oxygen capabilities. While measuring the Blood Oxygen level the back Crystal shines red, green LED,s and infrared onto your wrist. Then the Photodiodes Measure the amount of light reflected back. There is colour Algorithm is used as While there is Bright red means high level of oxygen and Dark red means less.  

                                                           

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