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SOLUTION

HRM / Heart Rate Monitoring

HRM：Heart Rate Monitor

Heart rate monitoring methods are mainly divided into two types: ECG and PPG.

The electrical HRM consists of two components: a monitor and a receiver. The heart signals are read by the electrodes of the monitor and then transmitted to the receiver via wireless signals (such as Bluetooth, ANT+, or other low-power wireless communication technologies).

As for optical technology, heart rate is measured with the help of an LED light emitted onto the skin, allowing for blood flow analysis. Optical technology is generally considered less accurate than medical-grade HRMs, which typically use electrical readings, but it is the most commonly used technology in multifunctional wearable devices like smartwatches and fitness trackers.

Smartwatches are the most feature-rich wearable devices, with many of them having heart rate monitors that can help you achieve fitness goals and maintain health (though, of course, wearable devices cannot replace medical consultations). Fitness trackers not only track your steps, but several models also include HRMs.

ECG / Electrocardiogram

ECG：ElectroCardioGraphy

Heart rate is detected by sensors that collect electrical signals from the body’s surface. When electrodes are placed on your chest in a hospital to perform an electrocardiogram (ECG), or when you wear a sports heart rate chest strap, both are examples of ECG.

ECG is a technology that monitors the heart using electrodes through bioelectrical signals. During each cardiac cycle, the heart is excited in sequence by the pacemaker, atria, and ventricles, accompanied by changes in the action potentials of countless myocardial cells. These bioelectrical changes are referred to as the electrocardiogram (ECG). By placing electrodes on the surface of the skin, the heart’s electrical activity can be detected and, after digital signal processing, multiple values—including heart rate—can be reconstructed.

PPG / Heart rate sensor

PPG：Photoplethysmography. Commonly known as optical heart rate monitoring, the heart rate sensor in Apple Watches is a typical example of PPG.

In simple terms, PPG measures heart rate using light reflection. The PPG sensor on the back of a smartwatch emits green light, which passes through tissues and arteries in the skin. While the absorption of light by muscles, bones, veins, and other connective tissues remains relatively constant, the absorption of light by the blood in the arteries changes as blood flows. This results in variations in the intensity of the reflected light. By converting the light into electrical signals and extracting the alternating current signal, the characteristics of blood flow can be reflected.

Blood Oxygen Module

Blood oxygen saturation generally refers to arterial oxygen saturation. Arterial oxygen saturation (SaO₂) measures the extent to which oxygen is bound to hemoglobin (Hb) in the arterial blood. It represents the percentage of oxygen bound to hemoglobin out of the total hemoglobin, calculated as SaO₂ = HbO₂ / Total Hb × 100% = Blood oxygen content / Oxygen binding capacity × 100%. Arterial oxygen saturation indirectly reflects whether the body is hypoxic and the degree of hypoxia, but it is less sensitive in detecting hypoxia and carries the potential risk of masking it.

Normal values: The normal range for arterial oxygen saturation is 95% to 100%.

Optical Design Plan

Professional optical design engineers use Zemax software for optical simulation and analysis to provide clients with optimal design solutions.

HRM / Heart Rate Monitoring

HRM：Heart Rate Monitor

Heart rate monitoring methods are mainly divided into two types: ECG and PPG.

The electrical HRM consists of two components: a monitor and a receiver. The heart signals are read by the electrodes of the monitor and then transmitted to the receiver via wireless signals (such as Bluetooth, ANT+, or other low-power wireless communication technologies).

As for optical technology, heart rate is measured with the help of an LED light emitted onto the skin, allowing for blood flow analysis. Optical technology is generally considered less accurate than medical-grade HRMs, which typically use electrical readings, but it is the most commonly used technology in multifunctional wearable devices like smartwatches and fitness trackers.

Smartwatches are the most feature-rich wearable devices, with many of them having heart rate monitors that can help you achieve fitness goals and maintain health (though, of course, wearable devices cannot replace medical consultations). Fitness trackers not only track your steps, but several models also include HRMs.

ECG / Electrocardiogram

ECG：ElectroCardioGraphy

Heart rate is detected by sensors that collect electrical signals from the body’s surface. When electrodes are placed on your chest in a hospital to perform an electrocardiogram (ECG), or when you wear a sports heart rate chest strap, both are examples of ECG.

ECG is a technology that monitors the heart using electrodes through bioelectrical signals. During each cardiac cycle, the heart is excited in sequence by the pacemaker, atria, and ventricles, accompanied by changes in the action potentials of countless myocardial cells. These bioelectrical changes are referred to as the electrocardiogram (ECG). By placing electrodes on the surface of the skin, the heart’s electrical activity can be detected and, after digital signal processing, multiple values—including heart rate—can be reconstructed.

PPG / Heart rate sensor

PPG：Photoplethysmography. Commonly known as optical heart rate monitoring, the heart rate sensor in Apple Watches is a typical example of PPG.

In simple terms, PPG measures heart rate using light reflection. The PPG sensor on the back of a smartwatch emits green light, which passes through tissues and arteries in the skin. While the absorption of light by muscles, bones, veins, and other connective tissues remains relatively constant, the absorption of light by the blood in the arteries changes as blood flows. This results in variations in the intensity of the reflected light. By converting the light into electrical signals and extracting the alternating current signal, the characteristics of blood flow can be reflected.

Blood Oxygen Module

Blood oxygen saturation generally refers to arterial oxygen saturation. Arterial oxygen saturation (SaO₂) measures the extent to which oxygen is bound to hemoglobin (Hb) in the arterial blood. It represents the percentage of oxygen bound to hemoglobin out of the total hemoglobin, calculated as SaO₂ = HbO₂ / Total Hb × 100% = Blood oxygen content / Oxygen binding capacity × 100%. Arterial oxygen saturation indirectly reflects whether the body is hypoxic and the degree of hypoxia, but it is less sensitive in detecting hypoxia and carries the potential risk of masking it.

Normal values: The normal range for arterial oxygen saturation is 95% to 100%.

Optical Design Plan

Professional optical design engineers use Zemax software for optical simulation and analysis to provide clients with optimal design solutions.