Traditional watches, as a fashion item, have relatively limited functions. With the emergence of smartwatches, not only do their diverse features meet user needs, but their stylish designs are also highly favored by users. Smartwatches excel in health tracking, exercise recording, daily reminders, and more, making them a classic consumer electronic product in many people's lives today. What components make up a smartwatch, how does it work, and what are its operational principles and internal structure?
The core of this technology lies in the use of photoplethysmography (PPG), where green LED light is directed onto the skin to detect changes in light scattering caused by blood flow. This process converts light signals into electrical signals, which are then used to calculate heart rate. In simple terms, the process is: light → electricity → digital signal. When the heart pumps blood, the green light on the watch interacts with hemoglobin in the blood. The differences in absorption and reflection of green light by the blood allow the watch to capture and calculate the heart rate.
Behind photoelectric heart rate monitoring, several factors make green LED the preferred light source, including its minimal impact on skin melanin and moisture absorption, as well as the strong absorption capacity of hemoglobin for light of this wavelength. Some high-end watches can even adjust the LED color based on environmental conditions to enhance monitoring accuracy. Additionally, a few products employ electrocardiography (ECG), which requires specific chest straps and external devices to capture the subtle electrical changes caused by heartbeats to determine heart rate.
Smartwatch heart rate monitoring is not only based on PPG technology but may also use electrocardiogram methods to detect the R-wave in the QRS complex to calculate heart rate. By precisely measuring the intervals between heartbeats, accurate heart rate analysis can be performed for various populations. For example, the Veepoo RIG smartwatch uses photoplethysmography to monitor heart rate through optical detection of blood flow fluctuations at the wrist or ear. Although the monitoring results may deviate from those of professional medical devices, heart rate data from compliant and technically assured smartwatches still holds reference value.
The application of heart rate monitoring in smartwatches is extensive, helping users adjust exercise intensity, optimize workout results, and monitor heart health through changes in heart rate, such as conducting HRV analysis to assess cardiac status. As the technology matures, smartwatches can not only monitor heart rate in real time but also identify abnormalities and alert users, making them a powerful tool for health management. Nevertheless, smartwatches are not medical devices, and their data should be used as a reference for daily health awareness rather than a basis for treatment.
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