The health sensor is an essential factor for human health detection, and the accuracy of step counting is also greatly improved; it can monitor heart rate, monitor sleep, blood pressure, and even UV index. The implantation of a large number of sensors makes the monitoring items of the bracelet more comprehensive and intelligent.
1. Acceleration healthcare sensor
The acceleration sensor, the English name is acceleration transducer. It is a device that measures acceleration forces by sensing acceleration and converting it into electrical signals. At present, it has been widely used in many fields such as automobile safety, intelligent products, and game control.
The acceleration sensor is the basic sensor used to record the number of steps and running.
By measuring the direction and acceleration force, the accelerometer can determine whether the device is in a horizontal or vertical position, and can determine whether the device is moving, so as to achieve pedometer operation.
The basic style of the acceleration sensor is two-axis and three-axis. The two-axis can only measure the plane, and the accuracy needs to be improved; the three-axis sensor can better detect the position of the device in the three-dimensional space of the X-axis, Y-axis, and Z-axis. More accurate records.
Today’s smart bracelets are basically equipped with a three-axis acceleration sensor.
Three-dimensional rhythmic motion sensor (three-axis acceleration sensor) This sensor can sense acceleration or oscillation in different directions through a capacitive accelerometer. The motion sensor of the three-dimensional rhythm is divided into three-axis and six-axis. The three-axis will generally record data when swinging the arm, while the six-axis will record data and improve the movement through walking, running, cycling, and climbing stairs. Accuracy.
Software algorithm: According to the three-dimensional data captured by the three-axis acceleration in real-time, through filtering, peak and valley detection, and other processes, various algorithms, and scientific and meticulous logical operations are used to finally convert these data into the app of the bracelet. Read the number, the number of steps, intervals, calories consumed, etc. appear.
The development engineer reasonably optimizes and adjusts the calculation method of the sensor, and filters out irregular movement gestures and movements in daily life as much as possible.
Sleep monitoring function, sensors, and wrist touch to monitor people’s movements, the smart bracelet first learns the state of sleep through the body movement frequency, the movement more clarifies that the sleep is shallow, the deep sleep user has relatively little body movement; it is obvious that it can be seen, In fact, the error is relatively large to monitor the sleeping status through the bracelet, and the algorithm needs to be optimized to reduce the error.
2. Optical heart rate healthcare sensor
The optical heart rate sensor is a popular configuration of current exercise monitoring equipment. It uses LED light to illuminate the skin and the fluctuations caused by blood absorption of light to determine the heart rate level, and achieve more accurate exercise level analysis.
The optical heart rate sensor is used to monitor the heart rate.
The general method of heart rate monitoring principle:
Photoelectric transmission measurement method: The sensor of the wristband in contact with the skin emits a beam of light hitting the skin to measure the reflected/transmitted light. Blood absorbs light of a specific wavelength, and every time the heart pumps blood, this wavelength is absorbed in a large amount, so that the heartbeat can be determined. The disadvantage is that it consumes a lot of power and is interfered with by ambient light. At present, most of the smart bracelets or watches on the market to monitor the heart rate use the photoelectric transmission measurement method.
Test ECG signal method: The sensor of the bracelet can judge the user’s heart rate by measuring the electrical signal of myocardial contraction. The principle is similar to that of the ECG. The disadvantage is that the circuit is more complicated, occupying a large PCB space, and is susceptible to electromagnetic interference. At the same time, the sensor must be close to the skin and the placement position is relatively fixed. Few bracelets use this measurement method.
Vibration measurement: Every heartbeat will cause body vibration. This vibration is captured by a high-precision sensor, and then the heartbeat can be obtained through signal processing. Generally speaking, products such as smart cushions or smart massagers will use this Measurement method, bracelets are relatively rare.
As for the accuracy of the optical heart rate sensor, factors such as usual exercise, posture, and even skin color will affect the results of the photoelectric method of heart rate measurement. This method can accurately reflect the trend of heart rate changes, which is sufficient for ordinary people’s exercise heart rate monitoring.
How to judge whether a bracelet has a heart rate monitoring function? Just look at the back.
3. Global Positioning System (GPS) sensor
GPS is now a very popular technology. By using four of the 29 total earth-orbiting satellites for positioning, it is possible to obtain precise positions with less error. GPS positioning has been widely used in a variety of electronic products.
Due to the high power consumption, it has not yet been fully popularized in sports bracelets. Only some sports watches for positioning professional sports monitoring to have GPS chips, which are used to record the user’s geographic location, running routes, and so on. Moreover, a bracelet with a GPS positioning system.
4. Temperature healthcare sensor
Since the bracelet is in direct contact with the skin, the temperature sensor can measure the skin temperature.
Through the rise of body temperature, the smart bracelet judges whether it is exercising or may have a fever. At the same time, it can monitor the abnormality of human body temperature in accordance with the change of heart rate.
The temperature sensor is a simple but practical sensor.
5. Air pressure healthcare sensor
The altitude change of the location is calculated from the weak air pressure change during the movement. The accuracy can be controlled within 10cm during the height movement of the 10-story building.
The air pressure sensor is used to measure the elevation, which can measure the movement data more accurately.
Although the air pressure sensor can only measure air pressure data, the altitude can be accurately known through this data. The air pressure sensor can detect changes in altitude to provide accurate altitude information when GPS is not covered by large shopping malls and mountainous areas. An air pressure sensor is added to the bracelet.
Barometric pressure sensors can also help improve the accuracy of fitness trackers, especially in applications that calculate calories.
Calorie energy expenditure
Under normal circumstances, calorie consumption depends not only on the step count data obtained by the accelerometer, but also on the individual’s physiological data (such as age, weight, height, etc.). Depending on the sensors inside the device, heart rate data or GPS recorded speed, distance, and altitude can also be included in the calculation.
The calories consumed by sports such as running, climbing stairs, and climbing vary. Although the acceleration sensor can determine that a person is climbing, it cannot determine whether the person is uphill or downhill. Through the introduction of high-level motion data through the pressure sensor, and then using the corresponding algorithm, the energy consumed by the user can be accurately calculated.
6. Electric skin response healthcare sensor
The galvanic skin response sensor is a more advanced biosensor, usually equipped with some equipment that can monitor sweat levels.
Most people have this experience: before going on to a very important task, they may feel nervous, or even anxious, so that their hands and feet sweat. The process of transforming this kind of psychological response into a physiological response can be detected by an electrical skin sensor.
The human skin is a kind of electrical conductor. When sweat starts, the skin electrical response sensor can detect the sweat rate. With the accelerometer and advanced software algorithm, it is helpful to monitor the user’s exercise level more accurately.
7. Ambient light and ultraviolet sensor
The ambient light sensor simulates the sensitivity of human glasses to light, and can judge the time according to the brightness of the surrounding light, and effectively saves the power consumption of the bracelet.
Ultraviolet sensors use the photoemission effect of certain semiconductors, metals or metal compounds, which will release a large number of electrons under ultraviolet radiation, and the intensity of ultraviolet rays can be calculated by detecting this discharge effect. The UV index in the light can be monitored, and the sunscreen reminder operation can be realized.
8. SPO2 sensor for blood oxygen saturation healthcare sensor
The absorption ratio of hemoglobin and oxygenated hemoglobin in blood to infrared light and red light is different. The blood oxygen content can be measured by irradiating the finger with two LEDs of infrared light and red light at the same time and measuring the absorption spectrum of the reflected light.
Blood oxygen saturation may be of little use to ordinary users, but for mountain enthusiasts, it can promptly remind to avoid hypoxia, and it is also very useful for users with respiratory diseases such as asthma.
9. Capacitance healthcare sensor
It is a sensor that reflects the transformation of other quantities in the change of capacitance.
It is used to detect whether a bracelet is worn.
Many bracelets have an off-wrist detection function. In fact, the capacitance sensor is used to monitor the change of the capacitance voltage, and the matching algorithm automatically detects whether the user is wearing the bracelet and gives a corresponding reminder. Avoid misjudgment of sleep and heart rate monitoring in the scene without wearing a bracelet,
10. Hall healthcare sensor
A magnetic field sensor based on the Hall effect. When an electric current passes through a conductor in a magnetic field, the magnetic field produces a force perpendicular to the direction of movement of the electrons in the conductor, thereby generating a potential difference between the two ends of the conductor.
There is a built-in magnet on the wristband of the wristband, which can judge whether the earphone is on or off the wristband by sensing the change of the magnetic flux between the earphone and the wristband. When it is taken off, the sound will be adaptively converted from the mobile phone to Bluetooth output. It is very common in mobile phones, but not common in bracelets. It is mostly used in Bluetooth headset bracelets.
11. Bioelectrical impedance healthcare sensor
The blood flow monitoring can be realized through the biological body’s own impedance and converted into specific heart rate, respiration rate and skin electrical response index. It is a more advanced comprehensive biosensor with relatively higher accuracy.
In recent years, thanks to the evolution of sensors, the bracelet monitoring data has become more and more accurate. In the future, more and more powerful sensors will be gradually added to the bracelet, and more advanced software algorithms will be configured to help obtain more accurate monitoring data.
12. Electrophysiological healthcare sensor
The body’s organs, tissues, and nerve activity are related to electric potential, so monitoring electrophysiological (EP) signals can help find abnormal vital signs. Especially the heart (electrocardiogram: ECG), muscle tissue (EMG: EMG), brain (electroencephalogram: EEG) and other related diseases can be diagnosed through the electrophysiological monitoring system.
Traditional electrophysiological sensing systems require large electrodes to be attached to the target area of the body with tape, clips or adhesive pads, and conductive medical gels are used to ensure that the electrodes stay in contact with the skin.
This system can achieve accurate reading of monitoring data, but it is relatively complicated, and due to the limitations of large equipment, rigidity, and heavy electrodes, it is more suitable for professional doctors to monitor and read signal data in hospitals. Medical diagnosis.
13. Chemical healthcare sensor
Biological fluids (blood, tears, saliva, sweat, urine, etc.) usually contain electrolytes, metabolites and hormones. Chemical sensors can provide important physiological information by detecting and analyzing these biomarkers, thereby making early diagnosis and prevention of diseases possible. For example, the shortage and surplus of heavy metals will have harmful effects on the human body. Therefore, continuous monitoring of the concentration of heavy metals can take appropriate action.
Most of the dynamic blood glucose monitors we come into contact with in our daily life have built-in chemical sensors to monitor the glucose content in the interstitial fluid, so as to judge the level of blood glucose in the human body.
In addition, sweat also contains a lot of important physiological information. Researchers at Stanford University believe that “sweat contains important electrolytes, metabolites, amino acids, proteins and hormones. Monitoring sweat can be used to determine metabolic diseases, physiological conditions, or a person’s drunkenness.”
Although a single-index biosensor can provide some health-related information, most devices reflect limited content and have problems with accuracy and reliability, because multiple factors may lead to the same result. A technology developed by scientists at KTH Royal Institute of Technology in Sweden uses multi-purpose chemical sensors to measure blood and sweat.
These sensors can be integrated into skin patches or deployed as microneedles, and can also be combined with existing sensors (such as ECG). Sensor) integration, providing important parameters, has great significance and application prospects in the field of medical diagnosis and health monitoring.
The continuous innovation of scientific researchers has made the secrets of human health more deeply discovered and perceived. We can use various auxiliary sensors and monitoring equipment to understand our own health.