The magnetometer in your smartphone measures the strength of earth’s magnetic field.
The magnetometer is enclosed in a small electronic chip that often incorporates another sensor (typically a built in accelerometer) that helps to correct the raw magnetic measurements using tilt information from the auxiliary sensor.
In addition to general rotational information, the magnetometer is crucial for detecting the relative orientation of your device relative to the Earth’s magnetic north.
Photo “Three-axis magnetometer sensor unit” by Steve Marple is licensed under CC BY 2.0
Today, mobile phones use IR-based proximity sensors to detect the presence of a human ear. This sensing is done for two purposes: to reduce display power consumption by turning off the LCD backlight and to disable the touch screen to avoid inadvertent touches by the cheek.
Photo “New VCNL4000 Proximity and Ambient Light Optical Sensor” by Vishay Intertechnology is licensed under CC BY 2.0
Traditionally, barometers have been used to detect—and predict—short term changes in weather. Measured drops in pressure indicate rain is on the way. Sharply rising pressure signals clearer skies are ahead. But surely, Apple and Google didn’t conspire on this just to make more accurate weather predictions, right?
The barometer uses its atmospheric pressure readings to determine your altitude and more accurately determine how quickly you’re moving through an area.
Photo “Barometer” by Juan Pablo Olmo is licensed under CC BY 2.0
Typical accelerometers are made up of multiple axes, two to determine most two-dimensional movement with the option of a third for 3D positioning. Most smartphones typically make use of three-axis models.
Photo “ADXL3XX” by Windell Oskay is licensed under CC BY 2.0