7.4 Accelerometer data
The data recorded by the accelerometer can be utilized by the operator to recognize the movement and
non-movement periods from the measurement. The reading from the accelerometer is the acceleration
induced by the sum of all forces acting on the device, including gravity, movement of the patient and
movement caused by the environment, for example vibration of a car.
The total acceleration is represented by the accelerometer vector components (x, y and z). The direction of
each acceleration component is represented by the sign of the vector and the amplitude is represented as
the absolute value of the vector.
The strong environmental-based vibrations (for example driving a bumpy road) can reflect on
accelerometer data when the subject does not move. The accelerometer output is raw data.
Accelerometer data is not analyzed within the device or differentiated between various physical
activities.
Figure 13 Accelerometer axis directions
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