Smartphone Basics

I’m here to make sense | Smartphone Sensors

Today’s smartphones are incredible little machines. We’ve grown so used to our iPhones and Android handsets that we take them for granted even though there’s so much cool technology packed into them. Take their sensors for example. Do you know how many different kinds go inside a smartphone?

Sensor is nothing but a converter that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. These sensors are capable of providing raw data with high precision and accuracy, and are useful if you want to monitor three-dimensional device movement or positioning, or you want to monitor changes in the ambient environment near a device. For example, a game might track readings from a device’s gravity sensor to infer complex user gestures and motions, such as tilt, shake, rotation, or swing. Likewise, a weather application might use a device’s temperature sensor and humidity sensor to calculate and report the dew point, or a travel application might use the geomagnetic field sensor and accelerometer to report a compass bearing.

GPS (Global Positioning System)

GPS [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.

The Accelerometer & Gyroscope

Accelerometers are hardware sensors. They are the simple MEMS (Microelectromechanical System) devices which are used to measure position, motion, tilt, shock, vibration, and acceleration (the rate of change of velocity). As its name implies, it measures the acceleration that the handset is experiencing relative to freefall. Move it in any direction and data from this sensor will spike, but leave it still and it will go flat. They are available with one, two, or three axes. A 3-axis accelerometer senses the orientation of the phone and changes the screen, images, web browser, music player accordingly, allowing the user to easily switch between portrait and landscape mode.

Accelerometer & Gyroscope

Accelerometers in mobile phones are used to detect the orientation of the phone. The gyroscope, or gyro for short, adds an additional dimension to the information supplied by the accelerometer by tracking rotation or twist. A Gyroscope can provide orientation information with greater precision. Thanks to this particular sensor, Android’s Photo Sphere camera feature can tell how much a phone has been rotated and in which direction. It is also used by Google’s Sky Map for telling what constellation you’re pointing a phone at. An accelerometer measures linear acceleration of movement, while a gyro on the other hand measures the angular rotational velocity. Both sensors measure rate of change; they just measure the rate of change for different things.

The Proximity

The Proximity Sensor

Proximity Sensor is a hardware-based sensor & detects the presence of nearby objects without any physical contact. Comprised of an infrared LED and an IR light detector, it is placed near the earpiece of a phone, and for a good reason – when you place the handset up to your ear, the sensor lets the system know that you’re most probably in a call and that the screen has to be turned off.

The sensor works by shining a beam of infrared light (invisible to human) which is reflected from a nearby object and picked up by the IR detector. The object being sensed is often referred to as the proximity sensor’s target. Different proximity sensor targets demand different sensors. For example, a capacitive or photoelectric sensor might be suitable for a plastic target; an inductive proximity sensor always requires a metal target. The maximum distance that this sensor can detect is defined “nominal range”.

The Compass or Magnetometer

Yup, it is able to detect magnetic fields. The magnetometer is one of the sensors that compass applications use to point at the planet’s North Pole. Apps made to detect metal use this sensor as well. The Compass or magnetometer is a hardware-based sensor which can be used to determine the angle by which the device is rotated relative to the Earth’s magnetic north pole. As a result, your phone always knows which way is North so it can auto rotate your digital maps depending on your physical orientation. Nokia Lumia 610 has this sensor built-in.

The Light sensor

An ambient light sensor is a hardware-based sensor which is typically used for adjusting the display brightness hence saving the battery power. It measures how bright the ambient light is. The phone’s software uses this data to adjust the display’s brightness automatically.

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.

The Fingerprint

Built into a number of smartphones, including the iPhone, the Samsung Galaxy, and the HTC One Max., Fingerprint scanners are most often used as an extra layer of security – as a substitute for a lock screen password.

The Fingerprint Scanner

The Barometer

Higher-end phones have a built-in barometer – a sensor that can measure atmospheric pressure. Contrary to what you may suggest, it has nothing to do with weather. Instead, the data measured by it is used to determine how high the device is above sea level, to help the GPS chip inside the device get a faster lock by instantly delivering altitude data, which in turn results in improved GPS accuracy. On a related note, the Motorola XOOM and the Samsung Galaxy Nexus were among the first Android devices to feature this sensor. This sensor is found in only some selective latest mobiles.

The Thermometer & Barometer

The Thermometer

Some folks might remember that the Samsung Galaxy S4 bragged with a thermometer for measuring ambient temperature. However, there’s a thermometer in pretty much any smartphone, and some handsets might have more than one of them. The difference is that they’re used to monitor the temperature inside the device and its battery. If a component is detected to be overheating, the system shuts itself down to prevent damage. And speaking of the Galaxy S4, it pioneered the use of an air humidity sensor in a smartphone.

The Pedometer

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 Google Nexus 5 is among the few phones that have a true pedometer built into them.

The Heart rate sensor

This list would be incomplete if we do not mention 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.

The Heart Rate Sensor

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.

Detect Harmful Radiation

A sensor that you wouldn’t expect to find on a smartphone is one capable of detecting harmful radiation. Yet there’s a phone that sports one – the Sharp Pantone 5. Released only in Japan, it features a dedicated button which launches an app used to measure the current radiation level in the area.

RGB Light Sensor: Measure the red, green, blue and white intensity of the light source, used mainly to make adjustments in the Cameras.

Hall Sensor: Recognizes whether the cover is open or closed.

Adding the microphone and the cameras to the list gives us a figure of at least 16 different sensors that are used in a smartphone. That’s quite a lot of data that a smartphone can pick up, use, and provide. This is only the beginning chapter in the era of self-aware devices and continuous data logging. With smartphones getting more and more awesome by the year, there’s much more to come.

How would you like a phone that could track your heart rate and emotional state, perhaps putting on some soothing music as soon as you start to get anxious? We’re still waiting for a phone that knows when you’re happy or sad – but Google Now and Siri are certainly getting there.

Think there’s a sensor that I’ve missed? Shout it out in the comments!



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