Android devices have built-in sensors that measure motion, orientation, and various environmental conditions. CPU gets the data from sensors, uses seperatly or combined at applictions  and device functions.

• Accelerometer Sensor: Observes the linear movements of the device at three axes (x,y,z) and measures the accelaration. Accelerometer also calculates the gravitational accelaration which the other sensors can not. Applications such as GPS and Navigation use the combined data, collected from Accelerometer, Orientation, Gyroscope and Magnetic sensors. In addition it is used for camera image stabilizition and game movement actions. It is a hardware based sensor and works continuously.
• Orientation Sensor: Measures the screen rotation angle at three axes (x,y,z). Aquired data is especially used to find directions and locating the device's coordinates by combining the data collected from other sensors. It may be hardware or software based and works continuosly.
• Gyroscope Sensor: Observes and measures angular rotational velocity of the device at three axes (x,y,z). For example, Accelerometer only observes the linear movements of the device, but can not sense the spin, flip or tilt movements happening on device's own axis. For that reason all data from Acceleroemeter and Gyroscope sensor must be combined to read device's accurate movements through the space. It is a hardware based sensor and works continously.
• Magnetic Sensor: This sensor interacts with earth's magnetic field and measures the magnetic value of the device's location at three axes (x,y,z). CPU uses this data to form a digital compass. Aquired data is especially used to find directions and to locate the device's coordinates by combining the data collected from other sensors. It may be hardware or software based and works continuosly.
• Proximity Sensor: Measures the distance of any object close to the screen of the device. Some types only sense the object if gets closer than a default value (8 cm), and some can measure the exact distance. The tyipical usage of this sensor is turning off the screenlight while talking on the phone. By this, possible commands with unwanted touches are avoided. It is hardware based and works only on defined situations.
• Hall Sensor: Senses the magnetic area on Flip Covers. Turns off the screenlight when the cover is closed and turns on when it's opened. It is hardware based and works only on defined situations.
• Light Sensor: Starts working when the ambient light changes. Measures the new value and sends the data to CPU. CPU may change the screen brightness or camera lens diaphragm width due to aquired data.
• Sound Sensor (Microphone): Transforms the audiosignals to electrical signals and sends to CPU. Basicly it is the device's microphone. It is hardware based and works only on defined situations such as sound recording, phone calls and etc.