Edited by Pulak at 2016-04-16 21:15

Most Android-powered devices have built-in sensors which can be broadly categorized as motion, orientation, and various environmental conditions. These sensors are capable of providing raw data with high level of precision and accuracy, which in turn used by the smartphone OS to provide better user experience.

Common sensors which are available in mid to high end smartphones are-

1. Proximity Sensor
A proximity sensor able to detect the presence of nearby objects without any  contact. For its working, it requires an infrared LED and an IR light detector. Generally it is placed near the earpiece of a phone. This sensor is a must for any smartphone and included in every (well most of the) handset.  When you place the handset up to your ear, the sensor lets the system know that you're most probably in a call and the screen has to be turned off. The sensor works by sending infrared light from the infrared LED, which is reflected from a nearby object and subsequently detected by the IR detector.

2. Light sensor
A light sensor detects how bright the external light is. The phone's software then uses this data to adjust the display's brightness automatically. If the light is very bright, the screen's brightness is increased to match it up, and when it is dark, the display is dimmed down. This sensor is used  by mid and high end phones, and low end phones generally skips this sensor.

3. Barometer
A barometer can measure atmospheric pressure. Data measured by it is used to determine how high the device is above sea level, which in turn results in improved GPS accuracy. This sensor is not common in low and mid range smartphones.

4. Magnetometer
A magnetometer provides orientation sense to the smartphone with respet to the earth's magnetic field. Simply put, it senses which way is North pole is. This sensor is useful for GPS navigation. Most mid and high end phones include this sensor.

5. Hall Sensor
Hall sensors are used for proximity switching, positioning, speed detection, and current sensing applications. This is a advanced proximity sensor.

This sensor mainly detects how close your smartphone's screen is to your body. It detects the position of ear with respect to screen and turns off the light of screen to saves battery. Also this sensor stops the accidental touch, unwanted input during call. This sensor detect the presence of body like cheek, face or ear and stops the web surfing, music or video during the call and saves battery. After the conversation, it resumes the same function which was stopped earlier.

6. Accelerometers
Accelerometers can measure acceleration i.e. the rate of change in velocity and can detect changes in orientation and  tell the screen to rotate. This sensor is used mainly for maintaining screen orientation i.e potrait to landscape and vice versa, and also used for step counter. This sensor is included in almost every smartphone.

7. Gyroscope
The gyroscope is a sensor that can provide orientation information as well, but with greater precision. Thanks to this particular sensor, Android's Photo Sphere camera feature can tell how much a phone has been rotated and in which direction. It is also used by Google's Sky Map for telling what constellation you're pointing a phone at.

8. Thermometer
Thermometer is present in every smartphone, and some handsets might have more than one of them. The primary thermometer is used to monitor the temperature inside the device and its battery. If a component is detected to be overheating, the system shuts itself down to prevent damage. Additional thermometer used e.g. Galaxy S4, uses an air humidity sensor in a smartphone. It basically tells the air temperature and humidity.