html5 devicemotion acceleration always changes

Question

I develop a web application and want to use the devicemotion event to get the acceleration to measure the speed and the distance but i noticed that even the device is static on a flat surface the acceleration values on y and always change.

    var clock = null, prevClock = new Date().getTime();
window.addEventListener("devicemotion", function(e) {
if (e.acceleration.x) {
    clock = new Date().getTime();
    var d = (clock - prevClock) / 1000;
    d *= d;
    motion.x = (e.acceleration.x);
    motion.y = (e.acceleration.y);
    motion.z = (e.acceleration.z);

    distance.x += (motion.x) * d;
    distance.y += (motion.y) * d;
    distance.z += (motion.z) * d;
    prevMotion = motion;
    prevClock = new Date().getTime();
}
}, true);

how can i measure the accurate acceleration.

Answer 1

you are already doing it the correct way. and also you won't get an more accurate acceleration than this. this is because the sensors are so damn sensitive (or just not accurate enough) that you will NEVER get a acceleration of 0 even when your device is just lying on a flat surface. newer phones have more accurate sensors. for example an iPhone 6+ gets way closer to the 0 instead of my Galaxy S4, but even with the iPhone6+ you will never get an acceleration of 0 on a flat surface.