What Can You Find Inside a Fitness Tracker?

What Can You Find Inside a Fitness Tracker?

The quantified self movement, which has exploded in popularity, involves tracking statistics such as activity, steps, and heart rate. The best wearable for you will be determined by your specific requirements; whether it’s step counting, sleep tracking, or 24/7 heart rate monitoring, there’s something for everyone.

But do you know what sensors are buried inside your Fitbit or Garmin fitness tracker, or your Apple Watch? Continue reading to find out.

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The 3 axis accelerometer

3 axis accelerometer sensors are ubiquitous in activity trackers and may be found in almost all of them. This is an electromechanical sensor that can detect both gravity and linear accelerations. The sensors track movement in all directions and can calculate the body’s orientation, inclination, and tilt, as well as take inertial position and velocity readings.


Using atmospheric pressure, an altimeter detects changes in altitude. The total number of flights of stairs you’ve climbed will be added together and used as a factor in your calorie count. This improves the accuracy of your calorie output.

Sensor for ambient light

Ambient light sensors restrict the light spectrum, allowing only visible light types to be recognised. The light is transformed into a digital signal, which is then broadcast to the fitness tracker’s CPU. This can be used to save battery life by making the wearable screen brighter or dimmer (depending on the weather or whether you’re inside or outside).


A barometer is a device that measures and shows atmospheric pressure. It determines whether a sunny or rainy day will occur by monitoring the pressure exerted by the atmosphere above it. This pressure measurement can also be used to calculate altitude.

The sensor of bioimpedance

Bioimpedance sensors capture a wide range of physiological signals by measuring the resistance of bio-tissue to a small amount of electric current. Two exterior electrodes drive little electrical energy, while two interior electrodes detect voltage changes.

Bioimpedance analysis has traditionally been used in clinical settings to assess body composition, such as body fat percentage vs lean body mass. They are used by fitness trackers to monitor heart rate, sleep, breathing rate, hydration, and skin galvanization. They’re also used by smart scales.

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sensor that detects capacitance

The user interface can be lit up by using capacitive proximity sensing to wake the device from sleep. The device’s power usage is reduced by including a capacitive sensor that turns it on only when it’s worn. Many other wearables, including the Apple Watch, use it to switch on the screen.


A compass, which can be seen on some sports watches, is an instrument with a magnetized pointer that shows the direction of magnetic north as well as bearings from it.

ECG (Electrocardiogram) sensor

The passage of electrical impulses through the cardiac muscle is recorded by an ECG sensor. Each time your heart beats, an electrical impulse is sent forth. Even if the amount of electricity is very small, ECG (ECG) electrodes placed on the skin can detect it.

Gesture recognition software

It’s a word for technology that is controlled by various bodily gestures, such as waving your wrist or grabbing something with your fingers. Much of the gesture technology is still in the early stages of development, but what’s to come makes this an area to keep an eye on in the future.

All of your running metrics are correct thanks to the Global Positioning System (GPS). It consumes a lot of juice, and obtaining a signal might be difficult at times. However, the end effect is well worth the effort. It connects to a series of GPS satellites to function. The receiver collects the signals, calculates the distance between them, and uses that information to determine its location.


Gyro sensors, often known as angular rate sensors or angular velocity sensors, detect angular motion. When you’re on the run, they aid in movement monitoring and increase accuracy. The greater the number of axes, the better.

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Your fitness tracker or smartwatch is almost certainly reliant on your smartphone for cellular connectivity. Unless, of course, you have one that supports Long-Term Evolution (LTE).

LTE is a high-speed wireless communication technology that is based on GSM/EDGE and UMTS/HSPA technologies. If the wristwatch on your wrist is LTE enabled, it simply implies that it has a cellular connection built in.


This is a sensor that measures magnetic fields, especially the magnetic field of the earth. A magnetometer can be used as a compass to fix your movement to the earth’s coordinate system and pinpoint your precise motions.This is useful for determining a user’s orientation with regard to the Earth’s magnetic north pole.

An optical heart rate sensor is a device that measures how fast your heart beats.

The optical heart rate sensor is housed inside the fitness tracker and shines a small light against the skin to measure heart rate. When your heart beats, blood rushes through your veins, causing less light to be reflected back to you. The algorithm used by the wrist-worn device will then compute your heart rate. Although there is a current trend to relocate heart-rate monitoring away from the chest and toward the wrist, accuracy is not as good at these places.

This technology appears to be capable of monitoring blood pressure as well. Samsung has acquired regulatory approval to include blood pressure monitoring in its most recent watch models. For the time being, this is a rough representation of how an actual blood pressure monitor operates. The optical heart-rate sensor is used to complete the reading, which takes less than 30 seconds.

A pulse oximeter

 is a device that measures the amount of oxygen in the blood.

Sensors on pulse oximeters evaluate how well oxygen is delivered to the portions of your body farthest from your heart (such as arms and legs). A light source, often LEDs, emits light into the tissue, while a photo detector collects light reflected or transmitted by the skin. Despite the fact that they became popular in the 1980s, they have only recently become cheaper.

The capacity to monitor pulse oxygen is built into some wristwatches and fitness trackers. This covers a variety of Garmin gadgets, as well as Fitbits and other fitness trackers.

Sensor for measuring temperature

Temperature variations are monitored using this sensor. It gives you a reading of your body temperature or the temperature outside. They are not yet widely used on wrist wearables, but they will be soon.

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UV detector

UV sensors alert the fitness tracker when you are likely to be exposed to harmful UV radiation and advise you to seek shade if you are at risk of burning.

Fitness wearables may have started off as little more than a pedometer that tracked simple movement, but they’re getting better with each passing year. Your smartphone can help. From encouraging you to improve your workout regimen to warning you about a potential sickness, it can help. Sensors will, in the not-too-distant future, move beyond basic health and fitness functions to become life-saving enhancement systems. Don’t be surprised if your wristwatch can monitor your glucose levels, analyze your sweat, and measure your blood pressure in the next several years. It’s all going to happen.

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