Accelerometer

The accelerometer is a new technology which has upgraded the user's experience in touch screen smart devices like mobiles and tablet PCs. The main function of this is to adapt the orientation change when the position is changed from vertical to horizontal and vice-versa. This technology actually measures the orientation change and positions the screen, so that user gets comfortable with viewing experience. If you are reading a e-newspaper, it will be a very nice experience if you read it in landscape view rather than conventional portrait mode. When the screen is tilted horizontally for landscape view, the function of smartphone accelerometer is to sense this change and adapt the screen accordingly. Along with this, this feature helps developer to make games and other apps user friendly. If you are playing racing games, it will be better if your car changes/steers itself when you tilt your phone or device. This is possible by this new technology. Initially this feature was added in iPhone but nowadays, most of the mobile manufacturers try to adopt this technology. So, in short, smartphone accelerometer is a device to gauge or measure the phone/tablet's orientation - tilt or landscape or portrait. Hence we can say that this is one of the coolest feature in any smartphone. 

Construction

The smartphone accelerometer contains circuit having 'Seismic mass' (made up of Silicon) and it goes on changing its position according to the orientation change and 'housing' attached to the device's circuit. 

Principle

Actually a smart device with accelerometer is nothing but a circuit based on MEMS(Micro Electro Mechanical System), that senses or measures the forces of acceleration that may be caused due to gravity of movement or tilting action. So, it is a device to measure the speed of acceleration or movement to which it is attached. If it is employed in mobile, it will do accordingly. It also senses the the angle at which it is being held via mobile. 

Following figure shows the working principle: 

The figure (b), a cutout of figure (a), shows change in capacitance as a result of change in position of Seismic mass, when smart device is tilted or changed in orientation. This will recognize the change in gravitational pull by changing the current equivalent to capacitance change. This is the working principle of smartphone accelerometer.

Important characteristics

It changes/adjusts the screen to proper viewing, when user changes the orientation from horizontal/landscape to vertical/portrait and vice-versa.
It interacts or controls the racing games (motion sensitive) by changing the direction or steer of the racing vehicle.
It helps the user to mute the phone/device in case of incoming call or when music is played, just by turning the device facing downward.
It makes web-browsing and photo viewing better by changing the orientation.
Accelerometer is also used in many devices like laptop for detecting drops. Whenever any drop is detected, it signals the hard disk's heads and they are parked or stopped to avoid the data losses. Hence for data security, accelerometer plays an important role.