PPG (photoplethysmography) is the technology that lets your phone’s camera take your heart signal. It shines a light onto your skin and highlights your blood vessels. The camera then picks up on the subtle changes in the lighting as blood passes through your capillaries with every beat.
After that, we analyze the frequency of your heartbeat using HRV, which is short for heart rate variability.
Your heartbeat usually has slight variations in the time between every beat. This is called heart rate variability, and it has been shown to reveal a lot of useful information about the state of the human body. This is because the sympathetic and parasympathetic nervous systems that control your heartbeat are also in charge of regulating a lot of other things in your body, and they affect your heart rate whenever you are sick or under a lot of pressure.