Smartphone Sensors Guide – What are the sensors and their functions

Smartphone Sensors

In this era of technology, phones are no longer just phones. Nowadays smartphones are used for much more than just calling or sending a text message, a huge array of applications from several categories have brought innumerable possibilities to the smartphone world. Each smartphone comes with several sensing hardware which upon up the possibilities to another level. Several sensors, for example, the Accelerometer, helps you automatically rotate the phone to the orientation that it is in. In this post, we’ll discuss some of the sensors, their functionality and their uses.


An Accelerometer is perhaps one of the most common sensors present in any modern age smartphone. This piece of hardware lets the phone automatically rotate to the orientation which it is held in. You can switch the phone position from portrait to landscape and be sure that the screen also rotates, thus keeping the content in best available format. An Accelerometer is also very useful for several applications that use it to modify the content based on the orientation and also for games that help control the character or the vehicle. An Accelerometer works by finding the acceleration due to gravity on the X, Y and Z axis. This data can also be interpreted to approximately finding the distance traveled by the device in a particular amount of time, this can be calculated using the distance formula of kinematics involving Acceleration and time to determine the distance traveled.


The Gyroscope is a more advanced and accurate version of an accelerometer. The gyroscope has the ability to determine the motion of the device in 3D space, thereby giving it the ability to exactly locate the device in a 3D space and plot values of how the device is moving. This technology works by finding the angle of rotation of the device in a way similar to the spirit bubble and then takes into consideration the time and other constraints to find the change in location in 3D space.

Gyroscope is mainly used in games and other applications which demand accurate and precise determination of the device location, for example, in First person shooter games, with the help of the gyroscope, the app can determine the exact position and orientation of the device and let the user aim the target or look around by just moving the device as required. Another major use of this that became prominent in recent days is for VR. Similar to as in the case of games, even in Virtual Reality apps, Gyroscope is the most important sensor which lets the app determine the location and motion of the device so that the display changes accordingly.

Light Sensor

Smartphone Sensors Light Sensor

The Light sensor is another sensor which is prominent in almost all the current generation smartphones and tablets. The most important function of this is to set the screen brightness automatically without any kind of human intervention whatsoever. When the device is in bright sunlight, most LCD and LED displays to perform poorly under low brightness, thus the sensor increases the screen brightness automatically to make the screen text readable, also when in a poorly lit environment, high brightness can cause problems to vision and make it very uncomfortable, for these situations the sensor automatically reduces the screen brightness to avoid strain on eyes.

Hall Magnet Sensor

The hall magnet sensor is not present in all the phones, but most smartphones with official flip cover have this sensor. This sensor works on the principle of magnetic deflection and when there’s a magnetic deflection it toggles the screen. When the flip cover is closed or any magnet is brought near the part of the smartphone containing the sensor, the screen turns off and when the magnet is taken away, the screen turns on again. This has very few applications other than the above-mentioned function. In fact, about less than 50% of the smartphones in the market have this sensor built in.

Proximity sensor

Smartphone Sensors Proximity Sensor

The proximity sensor is a very important sensor present in almost every smartphone, however, it is absent in most tablets unless they have a call functionality and a dedicated earpiece.This sensor uses infrared light to detect how close or far the device is from any object. This is a digital sensor and can only return two values, 0 or 1. Thus the sensor lets the device know if any object is present in the proximity of the sensor. This information is used to turn the screen on or off when a call is in progress so as to avoid accidental clicks. Using 3rd party apps, this sensor can also be used to turn the screen on or off automatically all the time, thereby reducing the load on the power button, however, this sensor uses a lot of power and is not the best idea to keep it working all the time.


Smartphone Sensors Magnetic Sensor

This sensor is used to detect magnetic field around the device finds it’s magnitude and direction. This sensor also works like a digital compass meter and helps the device find out geographic north for mapping applications. The sensor can be calibrated by choosing the calibrate option and then spinning the device in a 8 shape as shown on the screen. This sensor is also used by the metal detecting apps to find the magnetic deflection and measure it. This is sensor has also found its application in the VR industry, the small magnetic clicker on the Google Cardboard works only because of this magnetometer. A click gets triggered in the VR app everytime the button is pulled which generates a magnetic deflection.


Smartphone Sensors Barometer

This sensor is used to determine the altitude that the device is at. The barometer sensor is generally reserved for high-end smartphones and is present in very few smartphones or tablets. Barometer sensor can help increase the accuracy of a GPS sensor by adding accurate and precise altitude information. This sensor works by finding the atmospheric pressure which can be used to calculate the altitude from the sea level. This sensor was first found on the Motorola Xoom and Samsung Nexus smartphone.


This sensor is present in most smartphones, and few smartphones have more than one. Normally, in most smartphones, this sensor is used to monitor the thermal condition of other components of the device, and the device automatically turns off if any component is found to overheat so as to prevent damage to it. However when Samsung Galaxy S4 was found capable of measuring the ambient room temperature, it was nothing less than a surprise, and it also gave bragging rights to many consumers. Samsung made the ambient temperature measurement possible by mastering the air humidity sensor and interpreting that data to come up with the ambient room temperature value. This data is also used by the Samsung workout app, S Health, to find out if the user is in comfort zone or not.


A pedometer is used mainly for fitness applications and helps count the number of steps taken. In most devices, this is done by the help of an accelerometer, but few devices have a pedometer built in and this increases the accuracy and also reduces the power consumption at the same time.  LG Google Nexus 5 was one of the first devices to sport a dedicated pedometer.

Heart Rate sensor

Smartphone Sensors Heart Rate

Heart rate sensor was first introduced in Samsung Galaxy S5, this unique sensor helps detect the heart rate of a human being accurately by just placing his finger on the sensor. This sensor works by detecting the pulse by analyzing the blood flow using an IR light and sensor. There are several third party apps which measure the Heart rate using just the flash and the camera, they work on a similar principle as the dedicated heart rate sensor in the Galaxy S5. The heart rate sensor built-in to the Samsung Galaxy S5 works best with the dedicated S-Health app by Samsung which is used to monitor health and fitness.

Finger Print Sensor

This is probably the most important sensor which first came as a gimmick. The first notable smartphone to be a hit with the fingerprint sensor is probably the iPhone 5S, Motorola had implemented the fingerprint sensor in one of its smartphones before, but it was nothing more than a gimmick and the trouble that is involved using it relieved it of all the convenience. There are three major types of Fingerprint sensors at the moment in the market. With the help of a fingerprint sensor, you can unlock the device by just stamping your fingerprint on the sensor and you don’t have to the enter the password or put in the pattern. This greatly reduces the unlocking time and also increases convenience exponentially.

Optical fingerprint sensor

This is one of the least optimal implementations of a fingerprint sensor, the Samsung Galaxy S5 and the Samsung Galaxy Note 4 had this sensor and it involved the user to swipe his finger across the sensor for it to take a full image of the fingerprint and then analyze it. This type of fingerprint sensors belong to the first generation and are less convenient to use and also take much longer to scan the image, process and unlock the device.

Capacitive fingerprint sensor

Smartphone Sensors Fingerprint

This fingerprint sensor was first found in iPhone 5s and Samsung Galaxy S6 apart from other smartphones, unlike as in the optical fingerprint sensor, here you don’t have to swipe your finger and the sensor can read your fingerprint just by placing your finger over the sensor. This is the most common type of fingerprint sensor present in most smartphones as of now and also the most convenient of the currently available technologies. This works by recognizing the contact in a similar way to the capacitive touch screens but in a much more precise and accurate manner. Using this sensor, companies have achieved really low unlock times of as low as 0.3 seconds.

UltraSonic fingerprint sensor

This technology doesn’t have implementations in any smartphone yet, however, the prototypes have been demos and it can be expected really soon in the smartphones. On of the most important companies that have shown notable results in this technology is Qualcomm. This sensor can be easily hidden behind the screen and the fingerprint is scanned by placing the finger on the designated part of the screen or at a very small distance above it. This sensor works by blasting ultrasonic waves and when they reflect back, the grooves are mapped and a fingerprint image is formed using this information. It is difficult to judge the accuracy or speed of it as the technology is still in prototype stages and we can expect this technology in the market very soon.

Iris Scanner

Smartphone Sensors Iris Scanner

Apart from these sensors, there is a few trivial sensor which was skipped either because they’re present on too few phones or due to their lack of application. If you’ve any doubt about any sensor or want more information on any of them, do reach out to us in the comments section below.

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