ELI5: how do mobile devices know your movements? - eviltoast

I’m primarily talking about stuff like step counters, but also health apps measuring your heart rate, how many stairs you take, the length of your steps, and so on. I’m honest when you tell me to explain it to me like I’m five years old, this one boggles my mind.

  • Successful_Try543@feddit.org
    4·
    3 months ago

    For completing your nice explanation, here is the DeepL translation of the section in German Wikipedia on micro accelerometers:

    In recent years, miniaturised acceleration sensors have become increasingly important. These are micro-electro-mechanical systems (MEMS) and are usually made of silicon. These sensors are spring-mass systems in which the “springs” are silicon bars only a few μm wide and the mass is also made of silicon. Due to the deflection during acceleration, a change in electrical capacitance can be measured between the spring-mounted part and a fixed reference electrode. The entire measuring range corresponds to a capacitance change of approx. 1 pF. The electronics for analysing this small change in capacitance are housed on the same integrated circuit (IC).

    There are also variants in which piezoresistive resistors are attached to the bending beam by ion implantation, which change their resistance according to the bending and thus allow conclusions to be drawn about the acceleration.