Modes that use this sensor
The g-force meter measures the ratio of normal force to gravitational force (FN/Fg) in three dimensions. The g-force changes whenever the mobile device accelerates: speeds up, slows down, or changes direction. When the mobile device is not accelerating and lying face-up with respect to the surface of the earth, it reads g-force values of 0, 0, 1. This means that a normal force is only experienced in the upward direction, and that it is in equal strength as the force of gravity. An object that experiences a vertical g-force of 2 feels a force twice as strong as that of gravity in the upward direction (which is interpreted as “feeling twice as heavy”). An object that experiences a g-force of 0 is in free-fall (which is interpreted as “feeling weightless”).
G-force data is extracted directly from the accelerometer. Accelerometers often come in two flavors: piezoresistive cantilevers and capacitative. Piezoresistive cantilevers are protrusions of silicon, sometimes crafted with a paddle at the end that serves as an inertial mass. As the mobile device accelerates, the cantilever bends, changing the resistance of the silicon, which is interpreted as acceleration. Alternatively, a capacitive accelerometer contains three inertial comb-like masses attached to springs, with one in each dimension. When the mobile device is not accelerating and lying flat, a total g-force of 1 is measured due to the downward-pulling gravitational force (and the resulting upward reaction force of equal strength). When the mobile device accelerates, one or more inertial masses along the directions of acceleration move around in the presence of capacitor plates between the comb-like masses, varying the electric potential across the plates. Change in the electric potential across the plates is interpreted as acceleration and a change in g-force.
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