Sensors of modern smartphones

We continue to understand the device of the smartphone. Last time we looked at screens, but today we'll talk about sensors.

Smartphone screens

Accelerometer, also called G-sensor. The official definition is that it is a device that measures the projection of apparent acceleration. In simple terms, the accelerometer helps the smartphone determine the position in space, as well as the distance of movement. The main functions of the accelerometer:

  • Auto-rotate screen orientation;
  • Also, the accelerometer can be configured so that it responds to gestures and actions. For example, shake your smartphone or turn the screen upside down to mute a call;
  • An accelerometer also helps to count steps and helps to navigate on maps (Google Maps and others)

An accelerometer is a bulky device with an inert mass inside that reacts to all movements. This option was not suitable for a smartphone, so they came up with a chip with a crystal structure, a piezoelectric element and a capacitive resistance sensor. When the smartphone moves / rotates, the piezoelectric element emits discharges, and the sensor interprets them, thus determining the position and speed.

Sensors of modern smartphones

An accelerometer is a basic sensor found in any, even the cheapest, smartphone. It's a surprisingly technically complex product though. In smartphones, the accelerometer understands movements along 3 axes. The third is needed for 3D positioning. By the way, there is an accelerometer in all modern cars, but there it is usually two-axis (because the car does not spin in the air).

Not all accelerometers are created equal. They are made from different materials. Accordingly, some are more sensitive, some less.

The gyroscope is one of the coolest sensors, the usefulness of which for smartphones for a long time no one suspected until Steve Jobs came on the scene and explained how it should be. Watch the demo of this awesome feature and how the audience exploded with delight.

The gyroscope and accelerometer should not be confused. These sensors partially duplicate and complement each other. The gyroscope also serves to track the position of the device in space, but it does this by determining its own tilt angle relative to the earth's surface. This is very important, as it means that in zero gravity conditions, you will not be able to play Asphalt 9 using the tilt of the device as a control. Be careful!

A gyroscope (unlike an accelerometer) cannot measure the distance traveled, but it determines the position in space much more accurately. Please watch the Steve Jobs video above for an understanding. Starting at 1:10, Jobs shows how the accelerometer determines the position of an object in space and how a gyroscope.

Usually in modern smartphones, both sensors work in tandem. The gyroscope is essential for gaming, augmented reality, and a number of other applications. Often, in cheap smartphones, the manufacturer prefers to save on the gyroscope.

Proximity sensor. As the name implies, this is a sensor that helps determine if an object is in front of it. The simplest example is turning off the screen when the smartphone is brought to your ear. Also, the proximity sensor excludes phantom screen switching when the smartphone is in a bag or pocket. Such a sensor can, alone or in combination with the front camera, track movements of the hand above the screen to perform any functions. For example, scrolling a page in a browser and the like. There are many proximity sensor technologies available. It can work like radar, sonar, Doppler effect, there is an infrared proximity sensor, and sometimes a photocell is installed.

The basic proximity sensor, which turns off the screen when brought to the ear, seems to be already in all smartphones. But the advancedness of the sensor can be judged by the presence of additional functions.

Light sensor – everything is simple and clear here. Such a sensor helps to automatically adjust the brightness of the screen. The light sensor is already considered a basic sensor, but in cheap smartphones it can save money. And then you will have to manually set the brightness each time.

A modern light sensor usually works in combination with the AI ​​of a smartphone. For example, if the sensor has set a certain brightness, and you manually adjusted it, the smartphone will take a note and next time it will brighten the screen on its own. Accordingly, always let the light sensor get used to and adjust to your habits before judging its performance.

The Hall sensor is one of the most mysterious sensors in a smartphone, as few people know why it is needed. A sensor based on the so-called Hall effect detects a magnetic field and measures its strength. Physically speaking: electrons in a conductor are always perpendicular (90 degree angle) to the direction of the magnetic field. The density of electrons on different sides of the conductor will differ, a potential difference arises, which is recorded by the Hall sensor.

But smartphones use a simplified Hall sensor that detects only the presence of a magnetic field.

Usually a Hall sensor is needed for additional accessories. For example, it is he who turns on the screen iPad when the user removes the magnetic cover. By the way, in this function, the proximity sensor may well replace the Hall sensor.

Also, the Hall sensor works in tandem with the compass, making the latter more accurate.

The compass (magnetometer) is a very important sensor even if you are not in orienteering. It is the compass that is responsible for the fact that on Google Maps the user sees not just a point, but an arrow pointing in which direction you are looking.

When the compass is calibrated, the heading display is narrow. To calibrate the compass, open google maps and rotate your smartphone with the figure eight:

Sensors of modern smartphones

Barometer – usually only flagships can boast of such a sensor. The barometer assists with GPS and helps to determine the altitude. The presence of such a sensor is useful, since building plans are already appearing on Google Maps, and the barometer will determine which floor you are on. The barometer is also used in applications that measure physical activity. The bottom line is the same: determine how many floors you have passed.

Humidity sensor – once such a sensor was in the Samsung Galaxy Note 4, and then Samsung abandoned it. The role is obvious. The sensor detects the moisture level.

The heart rate / blood oxygen sensor is another proprietary sensor from Samsung, but many fitness bracelets also have one. Works in conjunction with LED flash. You put your finger on, the LED shines on your finger, and the sensor measures how the light waves are reflected. The waves are reflected in different ways depending on the pulse: blood vessels, then narrow, then expand. The function of determining oxygen in the blood works according to the same principle.

GPS is a Global Positioning System. In fact, this is not even a sensor, but the ability of a smartphone to communicate with satellites thanks to either a separate or multi-chip that supports several systems at once. Now every developed country has its own satellite system. GLONASS in Russia, Galileo in Europe, BDS (or BeiDou) in China, QZSS (or Quasi-Zenith Satellite System) in Japan. You can download the GPS Test program, which will show which satellites your smartphone sees. For example, the screenshot below shows the flags GPS, GLONASS and Galileo.

Sensors of modern smartphones

GPS is an excellent technology, but slow (as long as you can find and interrogate all the satellites there) and consumes a lot of energy and works well in open areas, so A-GPS (Assisted GPS) was also invented. The principle is based on the fact that while GPS is looking for satellites, the smartphone manages to interrogate cell towers, Wi-Fi networks, Bluetooth devices for their location. This significantly increases the cold start time and also reduces energy consumption.

Dual band GPS. Support for this option appeared in devices starting bfz with Android 7 and older. iPhone can't do that.

Usually satellites send two signals: coarse and accurate. If we talk about GPS, then these are L1 and L5 channels, while Galileo has E1 and E5. L1 is a rough channel. In a city, any signal reaches the satellite not only directly, but also bouncing off third-party objects (for example, buildings), that is, several signals arrive at the satellite at once. Accordingly, he also returns more than one, and an approximate location area is formed, where all returned signals intersect. There is also a precise L5 channel. This channel is much less prone to distortion, since it works according to the principle: The first signal that reaches the satellite is the correct one (after all, it goes along the shortest path, and not through reflections), and the rest can be ignored.

Previously, L5 belonged only to military and special objects, but now there are a lot of satellites in the sky, and there will be enough L5 satellites for everyone, so it was decided to share.

Sensors of modern smartphones

Sensors of modern smartphones

Instead of a conclusion

Geiger counter is the most unexpected sensor, right? This is a Japanese theme. And as far as there is information on the Internet, such a sensor was only in the Sharp Pantone 5 phone, which came out after the accident at the Fukushima-1 nuclear power plant.

A modern smartphone should have on board: an accelerometer, a gyroscope, a proximity and lighting sensor. A compass is also required. If you can do without a gyroscope, then a point on the map without a direction is annoying. A-GPS is already included in all smartphones. It's great if the GPS works in two bands. It's great if there is a barometer.

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