What is the difference between "gravity" and "acceleration" sensors in Android?
What is the difference between gravity and acceleration sensors in Android? From my point of view the physical value is the same in both cases.
Which one measures the force acting on unit mass inside the device?
ADDITION
The question is: what physical quantity is measured by these sensors? According to equivalence principle the acceleration and gravity are indistinguishable and the only way to measure both is by usual (but 3d) spring balance.
Answer
Acceleration sensor gives you back the sum of all forces applied to your device, while Gravity sensor returns only the influence of gravity. If you want to exclude the gravity from acceleration, you may use a high-pass filter or just subtract the gravity sensor values from acceleration sensor values -- not sure which method gives better precision.
Another method could be using Sensor.TYPE_LINEAR_ACCELERATION, which gives exactly (acceleration - gravity), however you should check if it's available on the device. I've found a few devices, which have ACCELERATION sensor working, but no response from GRAVITY or LINEAR_ACCELERATION sensors.