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The basis of all functions of smart watches-sensors

Updated: Aug 18, 2021

Smart watches have become an essential life health monitoring device, which can help us track and understand our daily activities and some basic health indicators. But how is this achieved? It all starts with the sensor on the smart watch.

Smart watches generally have about 16 built-in miniature sensors, and different sensors take on different functions. Sensors are the basis for smart watches to realize their functions. Generally speaking, the design of these sensors is mainly composed of transmitter, light path, electrode, and receiver. The sensor is one of the most important components.

Let’s take a look at what functions the sensors have.


1. The ambient light sensor can adjust the display brightness

Smart watches will be equipped with ambient light sensors. Its main job is to adjust the brightness of the display according to the surrounding light to suit people’s reading habits. It also helps to save battery life.

2, three-axis accelerometer detects movement and tracks direction

The three-axis accelerometer is the most common sensor in smart hands. It is mainly used to track forward and backward movement, sense gravity and determine the direction, position and rate of speed change of the body.

3, the altimeter can detect your climbing height

The altimeter can only detect changes in altitude. It helps to detect whether you are climbing stairs or downhill, so it helps to measure calories. High-precision altimeters are more used in sports smart watches.

4, the optical heart rate sensor can detect the heartbeat per minute

Now mainstream smart watches, such as Apple series 6, Huawei GT2 Pro, Veepoo Watch RIG, etc., are equipped with optical heart rate sensors. The sensors use light to check the blood flow rate on the wrist to calculate the number of heartbeats per minute. When the heart beats, blood flows quickly in the arteries, so less light is reflected on the sensor, and the amount of light is used to determine whether the heart is contracting or relaxing.

5, SpO2 monitor can measure the oxygen content in the blood

The optical sensor irradiates the skin with red light and infrared light, and then obtains the red light and infrared light reflected by the blood vessels under the skin, and finally calculates the blood oxygen through an algorithm. Veepoo’s blood oxygen designer explained: “The deoxygenated blood that flows back to the lungs through the veins is slightly more red than the oxygenated blood in the arteries. The sensor measures the relative reflectivity of red and infrared light in the blood through the wrist and observes it. The SpO2 value is estimated as the heartbeat changes.”

6. The bioimpedance sensor can measure breathing rate, scientific sleep, etc.

The sensor can measure the resistance of the skin to a small amount of electricity. Electrodes in smart watches can provide a small amount of current to measure sleep, heart rate, breathing rate, etc.

7, the proximity sensor can save battery and wake up the display when needed

When you approach the smart watch, the sensor will know that you are near the device and want to use it. In the case of a smart watch, this sensor can make the device go to sleep when not in use and save battery power. It is mainly used to open or close the display.

8. Compass to help directions and maps

The compass, as the name suggests, helps people find directions without getting lost.

9, ECG sensor

ECG sensor is a new feature of wearable devices. Now, the function of this sensor is to detect the tiny electrical pulses emitted by your heart every time your heart beats, and record them to form an electrocardiogram waveform. The sensor detects this minute’s heart signal through electrodes on the wearable device. The generated data can be used as medical data reference.

10. Gyroscope

Technically speaking, the gyroscope is used to detect the angular velocity of movement and accurately track them during the journey. The gyroscope is a universal function.

11. Gesture sensor detects wrist movement

When the hand is moved in a certain way, the gesture sensor can instruct the smart watch to perform certain activities. For example, if the wrist is flicked twice, the call will be disconnected, or the stopwatch will start timing when the hand ring rotates. It is the job of the gesture sensor to detect these pre-feed actions.

12. Ultraviolet sensor can measure exposure to harmful sunlight

Some smart watches will also provide information on whether outdoor sunlight is harmful. This is detected by an ultraviolet sensor. When we are walking under the sun, the ultraviolet sensor will detect ultraviolet rays.

13. Magnetometer

Magnetometer, GPS and compass can determine the coordinates of where we are.

14. Galvanic skin activity sensor

Galvanic skin activity and EDA sensors are the second new features of smart watches. It measures pressure with a heart rate tracker, ECG and skin temperature sensor. It can detect subtle electronic changes in skin sweat and help you relieve stress. At the same time, you can do stress relief exercise.

15, skin temperature sensor

The skin temperature sensor mainly detects temperature changes, and then determines whether we have a cold or female menstrual cycle.

Keywords: smart watch; sensor; blood oxygen; heart rate; ECG; Apple; Huawei; Veepoo; dynamic tracking;

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