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Introduction To The Working Principle Of smart Watches


With the arrival of intelligence, smart wear is more and more widely used by people, and the development of smart watches is especially rapid. People have even likened smartwatches to mini phones, because smartwatches also have most of the functions of smartphones. Then, some people will ask, what is the working principle of supporting so many functions of smart watches, the following is with small editor Allan to take a look!

The working principle of smart watches is mainly to use the watch built-in intelligent system, equipped with smart phone system and connected to the network to achieve multi-function, can synchronize the phone, mail, photos, music and so on. In addition, the smart watch can also record daily exercise and sleep time, which can be said to greatly enrich the function of the watch.

Some of the features a smartwatch might have are extensions of what a smartphone can do. For example, by designing it to prompt phone calls or tweets, users no longer need to take their phones out of their pockets, backpacks or handbags, and smart watches have unique advantages when it comes to sports and fitness. In addition, smart watches also have great advantages in mobile payment. Here is a detailed introduction to the working principle of the three functions of smart watch detection steps, heart rate monitoring and positioning.

First, the principle of detection steps:

1. Sensor detection

This kind of sensor can sense the acceleration or vibration in different directions through the capacitive accelerometer. The three-dimensional motion state sensor is divided into three axes and six axes, the three axes will generally record data when the arm is swinging, while the six axes will improve the data recording and accuracy of the movement by walking, running, cycling and climbing stairs.

2. Software algorithm

According to the real-time data of the three dimensions captured by the triaxial acceleration, through filtering, peak and valley detection and other processes, the use of various algorithms and scientific and rigorous logic operations, and finally convert these data into readable numbers on the watch APP, and the number of steps, distance, and calorie consumption value are presented.

3, green light photoelectric measurement method

It is composed of two green wavelength luminous leds and a light-sensitive sensor, located on the back of the watch. The principle is based on the change in the density of the blood in the blood vessels in the arm when it pulsates, causing a change in the light transmittance. The luminous LED emits light waves of green wavelength, and the photosensitive sensor can accept the reflected light of the arm skin and measure the change in the intensity of the light field and convert it to the heart rate. Heart rate can be continuously measured, average heart rate calculated, and maximum heart rate recorded.

Second, heart rate monitoring principle:

In general, the principle of heart rate monitoring is usually divided into three kinds: one is the photoelectric transmission measurement method, the principle is that the watch and the skin contact sensor will emit a beam of light on the skin, measuring the reflected/transmitted light. Because blood absorbs a specific wavelength of light, each time the heart pumps blood, that wavelength is absorbed in large quantities, and the heartbeat can be determined. However, the disadvantage is that it consumes a lot of power and will be interfered with by ambient light. At present, the function of smart watches on the market to monitor the heart rate is to use photoelectric transmission measurement method. Another method is to test the ECG signal method, the sensor of the watch can judge the user’s heart rate by measuring the electrical signal of the myocardial contraction, the principle is similar to the principle of the ECG. The disadvantage is that the circuit is more complex, the PCB space is relatively large, vulnerable to electromagnetic interference, and the sensor must be close to the skin, and the placement position is relatively fixed, so it is difficult to use this measurement method for smart watches.

Third, positioning principle: used for children or elderly watches

At present, the main technology used in the positioning function of smart watches on the market is based on GPS positioning, base station positioning, WiFi positioning of these three types of positioning technology.

1. GPS Global Positioning System

The basic principle of the GPS navigation system (the United States) is to measure the distance between the satellite with a known position and the user’s receiver (GPS can guarantee that at any time, any point on the earth can observe four satellites at the same time) and then integrate the data of multiple satellites to know the specific position of the receiver. It is composed of space part + control part + user part, with an accuracy greater than 3m. This system is not an ordinary country can build, to rely on economic strength and technical level, at present, there are three mature satellite positioning systems in the world and one under construction. The existing satellite navigation and positioning system with America’s global positioning system (GPS) and Russia’s global positioning system (GlobleNaviga2tionSatelliteSystem), referred to as “GLONASS, and China’s big dipper, the European Galileo (construction).

2. LBS base station positioning

Base station positioning principle: The mobile phone (SIM card function) measures the downlink pilot signal of different base stations and obtains TOA (TimeofArrival) or TDOA (TimeDifferenceofArrival) of the downlink pilot of different base stations. According to the measurement result and the coordinate of the base station, Generally using the triangular formula estimation algorithm, you can calculate the location of the mobile phone, the accuracy is not high, greater than 100m.

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