What sensors are inside smartwatches, and how do they collect and analyze data? For example, are metrics like heart rate, blood oxygen levels, or step count actually accurate? Could you provide some technical details?
How do sensors work in wearable technology?
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The working principle of sensors in wearable devices is quite fascinating. For example, PPG (Photoplethysmography) sensors are commonly used for heart rate measurement. These sensors detect changes in blood volume synchronized with heartbeats by measuring light absorption in the blood flowing under the skin. For oxygen level (SpO₂) measurements, sensors use the same principle but with different wavelengths of light – a combination of infrared and red light detects the difference between hemoglobin and oxygenated blood.
Step counting, on the other hand, is done using an accelerometer. The device continuously monitors the acceleration of body movements and checks whether it exceeds certain threshold values. The accuracy depends on the sensor's position and the quality of the algorithm – incorrect movements like swinging the arm can produce erroneous data. In my own experience, the heart rate sensor gave slightly delayed readings during workouts, but it was generally consistent during daily use. For oxygen measurements, the values fluctuated when I didn't fully cover my finger – clean contact is crucial.