sciencecapsules

       Heart rate monitors in smartwatches typically use photoplethysmography (PPG) technology to measure the wearer's heart rate. PPG is a non-invasive method that uses light to measure changes in blood volume and flow within the body. In smartwatches, this is usually done by shining light from an LED onto the skin, and then detecting the changes in light that result from the pumping of blood through the veins. The smartwatch typically has sensors that pick up the light reflected from the skin and convert it into an electrical signal, which is then processed to determine the wearer's heart rate. This measurement can be taken continuously, or at specific intervals, to provide a real-time reading of the wearer's heart rate. Why green LED: G reen light has a longer wavelength than red light, which makes it easier to detect changes in blood volume and flow through the skin. This is because the longer wavelength of green light is better able to penetrate the skin and

 How it works-1  An accelerometer in a smartphone is a microelectromechanical system (MEMS) device that measures acceleration and tilt. It works by detecting changes in motion by measuring the vibration or acceleration of the device. The accelerometer consists of a small mass suspended on a spring inside a sealed chamber. When the device is subjected to acceleration, the mass moves relative to the device, causing a change in capacitance that can be measured and processed by the smartphone's hardware. The accelerometer measures acceleration in three dimensions (x, y, and z) and provides data that the smartphone's software can use to determine the device's orientation, detect motion, and track changes in velocity and acceleration. The accelerometer is used for a variety of purposes in a smartphone, including screen rotation, motion tracking for games and fitness apps, and detecting the position of the device for navigation and location services. Additionally, it can be used t