Orientation of patient's position sensor using external field

摘要

An implantable cardiac stimulation device is equipped with an accelerometer-based sensor to sense a patient's movement and produce a vertical acceleration component indicative of a patient's acceleration in a vertical direction. A vertical velocity component is computed from the vertical acceleration component. The device may be further equipped with a magnetic field sensor to sense the earth's magnetic field as a way to obtain a true vertical orientation, against which the accelerometer-based sensor can be calibrated.