Patent ID: 8862422

Claim:
A sensor for sensing accelerations, which sensor comprises: an accelerometer for measuring an acceleration, a magnetometer for measuring a magnetic field, and a processor for, in response to at least one acceleration measurement measured by the accelerometer and at least one magnetic field measurement measured by the magnetometer, judging the acceleration, the processor comprising: an acceleration unit for comparing the at least one acceleration measurement measured by the accelerometer with at least one acceleration threshold, a magnetic field unit for comparing at least one change of the at least one magnetic field measurement measured by the magnetometer per time interval with at least one rate threshold, and a decision unit for, in response to comparison results from the acceleration unit and the magnetic field unit, deciding whether a total acceleration forms part of a tumbling free-fall or a non-tumbling free-fall, wherein the decision unit is configured to decide that the total acceleration forms part of a non-tumbling free-fall if the deviation of the total acceleration from a fixed acceleration value is larger than a first threshold while the rate of change of each of the at least one magnetic field measurement is smaller than the at least one rate threshold and if the time integral of the deviation of the total acceleration is larger than a second threshold.