How do smartwatches use sensors?

25 Ağu 21:28

Smartwatches primarily use photoplethysmography (PPG) sensors. These sensors send constant pulsed beams of green or red light into your skin and measure the amount of light that bounces back. They calculate your heart rate based on changes in blood flow—for example, when your heart beats, blood volume increases, and less light is reflected. This method is cheap and energy-efficient, making it popular in smartwatches, but it can produce errors during obvious movements or where light doesn’t penetrate well (e.g., darker skin tones). For activity tracking, they rely on accelerometers and gyroscopes. By detecting movement along the XYZ axes, they estimate your steps, calorie burn, and even sleep stages. Unlike heart rate sensors, these tend to be fairly accurate—counting steps flawlessly while walking, running, or cycling. However, they can miss steps during erratic movements like cycling or swimming, so some watches use GPS location data for more precise measurements. Based on my experience with accuracy: When running with the Samsung Galaxy Watch 5, step counts were usually over 90% accurate, but heart rate readings could be off by 10-15 bpm during sudden movements (like sitting down and standing up quickly). The most reliable results came from comparing my watch’s sensors to a chest strap on both my wrist and chest—PPG sensors often respond with a slight delay. The best approach isn’t to blindly trust every number your smartwatch spits out, but to use it for tracking trends. Simply put: “My heart rate is about 10% lower than usual today” is enough—don’t expect every single figure from a tiny device to be 100% accurate.

25 Ağu 23:56

I think one of the most commonly used methods is using a photoplethysmogram (PPG) sensor to measure heart rate. These green or white LEDs detect changes in blood flow while in contact with the skin and provide the heart rhythm. Of course, continuous measurement and calibration are important for accuracy.