The proximity sensor detects how close an object is to a smartphone's screen. It detects the position of a user's ear during calls to turn off the screen and save battery. This prevents accidental touches. It also detects signal strength and filters interference using beam forming. The ambient light sensor adjusts screen brightness based on light intensity to save battery life. The accelerometer senses orientation changes to adjust the screen from portrait to landscape. The compass uses signals from sensors rather than a magnet to determine direction. Gyroscopes maintain orientation and detect motion in six axes like roll and pitch using MEMS technology. The back-illuminated sensor captures more light for photos. Higher-end phones have barometers for improved GPS accuracy and pedometers count

1. Proximity Sensor
The main function of this proximity sensor is to detect how close your
smartphone's screen is to your body. When you use your smartphone,
it detects the position of ear with respect to screen and turns off the
light of screen and saves battery. Also proximity sensor stops the
accidental touch, unwanted input during talk. This sensor also detects
the signal strength, interference sources and amplify or filter by use of
Beam Forming Technique. Thus, in a nutshell, proximity sensor detect
the presence of body like cheek, face or ear and stops the web
surfing, music or video during talk/calling and save the battery. After
the conversation, it resumes the same function which was stopped
earlier during talk.
Proximity Sensor

2. GPS (Global Positioning System) sensor
GPS short form of Global Positioning System, originally developed
and setup for military operations and was made available for
everyone in 1980s by Government. GPS is a system which tracks the
target or 'navigate' the things by map or picture with the help of
GPS satellites. Nowadays smartphones come with assisted GPS or A-
GPS which does the same work with the help of intermediate server
in case of disconnection with main GPS satellite.
GPS (Global Positioning System) sensor

3. Ambient Light Sensor
This sensor optimize the light of screen when it exposed to normal
light with different intensity. Ultimate function of ambient light
sensor is to adjust the display brightness, which at the end saves
the battery power and life too. Ambient light sensor senses and
adjust the light based on principle of "superposition". They
contains photo diodes which are sensitive to different spectrum of
light and combined mathematical effect adjusts the gain and
output changes of the light intensity on the screen.
Ambient Light Sensor

4. Accelerometer
The main function of accelerometer is to sense the changes in the
orientation of smartphone with respect to datum and adjust the
orientation to suits the viewing angle of operator. For example,
when you are looking for web-page with increased width, you can
get this landscape view from changing the orientation of phone to
horizontal. Similarly camera mode also changes the portrait to
landscape or landscape to portrait mode when we change the
orientation of phone/camera. Ultimately this accelerometer
sensor sense the change in orientation by 3D (X,Y & Z axis)
measurement of acceleration of the device with respect to free
fall. One can better use this feature/sensor while playing
racing games where he/she can steer the car in the desired
direction by leaning the phone in that direction.
Accelerometer

5. Compass
We all know that the function of compass is to give right direction
with respect to the north-south pole of earth by use of magnetism.
But due to interference in communication, smartphone does not
use the magnet as one of the component in compass sensor but it
uses new technology which does the same work as conventional
compass does. If ultra low frequency signal coming from specific
direction like North or South and with the help of accelerometer,
the sensor can calculate the orientation and direction. This can be
possible by 'Hall effect'. Thus, by use of multiple sensors put across
different orientation and using disk/magnetic concentrator (with
high permeability material)which bends the lines of magnetic field
which are parallel to the plane of sensor plane this can be attained.
Compass

6. Gyros or Gyroscope
This sensor's function is to maintain and control the position, level
or orientation based on the principle of angular momentum.
When 'Gyros' used along with accelerometer senses motion from
six axes i.e. right, left, up, down, forward and backward. It also
detects the roll, pitch and yaw motions. Yaw, Roll and Pitch are the
angular moments seen from three axes i.e. X, Y and Z. Using
MEMS(Micro Electrical and Mechanical System) technology,
(iPhone 4 uses this technology) gyroscopic sensors helps in
navigation purpose and detecting the gesture recognition systems
used in smartphones and tablets.

7. Back-Illuminated sensor
Back-illuminated sensor is one of the new feature that every
camera contains. It is a type of digital image sensor which
changes or increase the light captured while capturing a
photograph. Earlier it was designed for security cameras and
astronomical purposes. Sony is the first company to implement
this technology in 2009.
Back-Illuminated sensor

8. Higher-end phones have a built-in barometer –
a sensor that 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. On a related note, the
While we're at the health and fitness topic,
the pedometer is a sensor used for counting
the number of steps that the user has taken.
Such data is usually obtained by the device's
accelerometer, but a dedicated pedometer is a
lot more accurate and power efficient. The
the heart rate monitor on the Galaxy S5. As
you can tell, it is made to measure one's pulse,
and it does that by detecting the minute
pulsations of the blood vessels inside one's
finger.
Others sensor
Mahboob Afsar
mahboob.afsar@gmail.com