Smartwatches have intimately involved in our lives, with all the stunning features they provide us, they are not only our fitness trackers, health guides, etc along with a lot of other things. So how do smartwatches achieve these functionalities? The answer would be all the delicate sensors compacted in the small cases on our wrists.
What kind of sensors does a smartwatch commonly have? Let’s take a look.
1. Ambient light sensor
Most fitness trackers and smartwatches come with ambient light sensors. Its main job is to adjust the brightness of the display based on the surrounding light. This also helps save power.
2. Three-axis accelerometer
Three-axis accelerometers are the most common sensors in wearable devices. The sensor can track forward and backward movement, sense gravity, and determine the body’s orientation, position, and rate of change in velocity.
The altimeter can only detect changes in altitude. It helps to detect whether you are climbing stairs or going downhill, thus helping to measure calorie count.
4. Optical heart rate sensor
Almost every fitness tracker comes with an optical heart rate sensor, which uses light to check the blood flow rate on the wrist to calculate the number of heartbeats per minute. When the heartbeats, the blood flows rapidly within the arteries, so less light is reflected on the sensor, which is detected as a heartbeat.
5. The SpO2 monitor
SpO2 monitors check the color of the blood to see how much oxygen is in it. “Deoxygenated blood returning to the lungs through veins is slightly more red than fully oxygenated blood in arteries,” explains DTNO.1. The sensor measures the relative reflectance of red and infrared light in the blood through the wrist and observes how it changes with the heartbeat. The SpO2 value was estimated based on the change.
6. Bio-impedance sensor
Bio-impedance sensors measure the skin’s resistance to small amounts of electricity. Battery charger electrodes in fitness trackers provide very small amounts of current to measure sleep, heart rate, breathing rate, water level, and more.
7. Proximity sensor
Proximity sensors just let the device know that you are near the device and want to use it. If you’re not wearing a fitness tracker, this sensor can put the device to sleep and save battery power when not in use. It is mainly used to turn the display on or off.
The compass helps the Map app run on the smartwatch and gives the device a sense of direction.
9. ECG sensor
ECG sensors are a new addition to wearables. This sensor’s job is to detect the tiny electrical pulses your heart sends out with each beat. The sensor detects the minute’s heart signal through electrodes on your smartwatches.
10. Global Positioning System
GPS only helps you detect your running volume, the location of your smartwatch and track your activity. It also helps guide the Map application.
Technically, gyroscopes measure the angular velocity used to detect movements and accurately track them on the go. For example, data from a gyroscope and other sensors can determine whether you’re actually running or jogging somewhere. In addition, it can eliminate motion caused by vigorous wrist shaking and mistake it for a vigorous run.
12. Gesture sensor
Gesture sensors can instruct the smartwatch to perform certain functionalities when the hand is moved in a certain way. For example, a call will be disconnected if the wrist is flicked twice, or the stopwatch will start timing when the hand circle is turned.
13. UV sensor
Some smartwatches also provide information on whether outdoor sunlight is harmful. This is detected by UV sensors, which detect UV light when you step outside.
The magnetometer works with GPS and compass to determine the exact coordinates of your location.
15. Galvanic skin response sensor
Galvanic skin response or EDA sensors are a new addition to wearables. It measures stress along with a heart rate tracker, ECG, and skin temperature sensor. It detects subtle electrical changes in your skin’s sweat and helps you relieve stress.
16. Skin temperature sensor
The skin temperature sensor detects slight changes in temperature to know if you are getting sick like a fever or detect the start of a menstrual period.