The heart rate measurement function of Apple's mobile phone is integrated into its built-in "health" application. This function uses specific technical principles to monitor the user's heart rate. One method is to use bioelectric signals to measure heart rate. This method captures the electrical signals generated by myocardial cells and then converts these signals into readable heart rate data. This principle is common in medical equipment such as electrocardiograph and some advanced wearable devices.
Another method is to use the pulse fluctuation of blood vessels to measure the heart rate. When the blood rapidly flows to the whole body, it will produce pulsating waves. By capturing this fluctuation by optical sensor or pressure sensor, we can monitor the pulse fluctuation of blood vessels in real time and calculate the heart rate from it. This method is widely used in smart bracelets, watches and other portable devices.