## How does a compass work in smart phones? What sensors are used and how do they show the correct directions?

Compass
We all know that the function of compass is to give right direction with respect to the north-south pole of earth by use of magnetism. But due to interference in communication, smartphone does not use the magnet as one of the component in compass sensor but it uses new technology which does the same work as conventional compass does. If ultra low frequency signal coming from specific direction like North or South and with the help of accelerometer, the sensor can calculate the orientation and direction. This can be possible by 'Hall effect'. Thus, by use of multiple sensors put across different orientation and using disk/magnetic concentrator (with high permeability material)which bends the lines of magnetic field which are parallel to the plane of sensor plane this can be attained.

So have you ever played with a magnet? If so, you know that if you put metal near it, they'll stick together! This is because the magnet creates a "field" in the space around it. The closer a piece of metal is to the magnet, the stronger they stick together, because it is more inside the Magnetic Field. The field actually has a specific direction that it points in, like a bunch of signs that all point one way.

Now, the Earth is actually a giant magnet! The Earth's field is fairly weak, so you may not notice it, but it's there. It's field points from the South Pole up to the North Pole.

Inside your smartphone is a small device called a Magnetometer. This is a really complicated device that measures how strong a magnetic field it is. The phone uses the data from this. When you wave your phone around, it measures the magnetic field a bunch of times, and mathematically calculates the direction of the field. Since we know the Earth's magnetic field points north, then as long as there isn't any major interference, the field will be pointing toward north, and we have our compass!

The smartphones  have a small magnetometer built in, which can measure the Earth's magnetic field. This information is combined with an accelerator that acquires information regarding the phone's position in space. It is able to pinpoint the phone's position from solid-state sensors within the phone that can measure their tilt and movement. The information provided by these devices means that the compass app can display cardinal directions no matter which orientation the phone is in, according to the algorithmic software development company Sensor Platforms.

The compass is able to determine north and south due to the magnet's interaction with the Earth's magnetic field. The cause of the magnetic field is not clearly  known, but geologists have made hypotheses regarding the phenomenon by analyzing the layers of the Earth. The Earth is made up of an outer crust, followed by the upper mantle, the inner mantle, the outer core, and then finally the inner core at the very center. The inner core is made up mostly of molten iron, but the very center of the inner core is under so much pressure that the molten iron is in a solid form. It is believed that the rotation of the Earth and the immense heat from the core cause the iron to move in a rotational pattern. This rotational pattern may be the source of the magnetic field that we see on Earth. The field produced is very weak, however, which is why the needle on the compass needs to be very lightweight and on a surface with minimal friction.

Did you know that the magnetic north pole is actually the geographical south pole and vice-versa?  Magnets have two poles, where the lines of magnetic flux enter and emerge. By analogy with the Earth's magnetic field, these are called the magnet's "north" and "south" poles. But we know that opposite poles attract each other, which means that the Earth's North Magnetic Pole is actually a magnetic south pole and the Earth's South Magnetic Pole is a magnetic north pole.
Any of the integrated circuits in this Google query are typically used in cell phones:

compass ic

Basically there are three major types: Hall Sensor, Anisotropic Magnetoresistive (AMR) or Giant Magnetoresistive (GMR).

Any of these types have a magnetic sensor that alters its resistance proportional to the magnetic field in a particular direction.  Circuitry on the chip detects the magnetic field strength and makes the field and its direction available as digital data.  The CPU on the phone pulls this data whenever compass data is required.

Versions exist in 2-axis and 3-axis forms which have separate magnetic field sensors oriented in x, y and/or z which allows the magnetic field direction to be determined.

Smartphone uses Magnetometer sensor feedback for compass application.

What is a Magnetometer ?

Magnetometers are measurement instruments used for two general purposes:
to measure the magnetization of a magnetic material like a ferromagnet, or to measure the strength and, in some cases, the direction of the magnetic field at a point in space.

What Technology used in Magnetometer ?
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. The Hall-effect                sensor produces voltage which is proportional to the                strength and polarity of the magnetic field along the                axis each sensor is directed. The sensed voltage is                converted to digital signal representing the magnetic                field intensity.  Other technologies used for                magnetometer may include magneto resistive devices which                change the measured resistance based on changes in the                magnetic field.

So if the traditional needle compass works because of a small magnet, how do the compass apps in phones work? As it turns out, the smartphones do have a small magnetometer, which can measure the Earth's magnetic field. This information is combined with an accelerator inside the phone. The accelerator gets information regarding the phone's position in space. It is able to pinpoint the phone's position from solid-state sensors within the phone that can measure their tilt and movement. The information provided by these devices means that the compass app can display cardinal directions no matter which orientation the phone is in, according to the algorithmic software development company Sensor Platforms.

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