Using Smartphones as time-bound IoT setup, can save huge capital investments. However, sensor data of a $10 phone is not always be as reliable as the one from a $500 phone. Differences arise in quality of data, frequency of data acquisition, consistency of data correctness or incorrectness, and due to calibration issues.
This is a fourth article from a series which identifies how smartphone sensors can be used reliably to produce scientific data for IoT applications. Previous article can be found here
Smartphones Sensors Basic
Smartphone sensors are types of sensing devices installed on a user's phone to gather data for various purposes, often in conjunction with a mobile app. Sensors is also referred as converter that measures a physical quantity and convert it into a signal which can be read by an instrument. These sensors can help your smartphones to be used as scientific tool.
At a high level mobile sensors are divided into 3 categories.
Below image explain sensor categories and few smartphone sensors under these categories.
An accelerometer detects acceleration, tilt and vibration to determine movement and orientation.
Accelerometers are used to determine the orientation in which the phone is held by the user and to use that information to display the screen in such a way that it will either orientate the screen into landscape or portrait view depending on which the user is holding it in. Accelerometer sensor refers to an absolute orientation with respect to the Earth.
A gyroscope identifies up/down, left/right and rotation around three axes for more complex orientation details.
Gyroscope are designed to measure the Coriolis force due to rotation. The Coriolis force is the tendency for a free object to veer off course when it is viewed by a rotating reference.
GPS or Global Positioning System sensor is receiver to receive data from a satellite navigation system that furnishes location and time information in all climate conditions to the user.
A proximity sensor detects when the phone is held to the face to make or take a call, so the touch screen display can be disabled to avoid unintended input.
A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for instance), and looks for changes in the field or return signal.
Reduce display power consumption by turning off the LCD backlight and to disable the touch screen to avoid inadvertent touches by the cheek.
The magnetic sensor in your smartphone is not an actual magnet, it is however capable of sensing the magnetic field of earth using Hall effect and determine your direction. A magnetometer detects the direction of magnetic north and, in conjunction with GPS, determines the user's location.
The magnetometer sensor in your tablet or smartphone also utilizes the modern solid state technology to create a miniature Hall-effect sensor that detects the Earth's magnetic field along three perpendicular axes X, Y and Z.
A light sensor detects data about lighting levels in the environment to adapt the display accordingly.
Light sensor is only used for either brightening or darkening the screen display. The light sensor will automatically check the lightness in the room and will try to balance the screen light with that, so that the user’s eyes won’t be damaged by either the brightness or darkness of the screen.
A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Pressure tendency can forecast short term changes in the weather.
Barometer sensor in smartphone could be of a lot of use to hikers who want to see how many feet they've climbed, or people curious to find out the pressure inside a train or plane.
Barometer provide supplemental data for the GPS sensor, adding altitude measurements for increased accuracy