A wireless motion sensor（WMS） is presented which can calculate 3D orientation information in realtime based on 3D acceleration

3D angular rate and 3D magnetic intensity obtained by measurement.With the advantage of compact size

light weight and low cost

it can be applied in wearable computing field.To extend working lifetime of the sensor

an algorithm of power management based on accelerometer is proposed.The experimental result proves that compared with other existing commercial motion sensor

the proposed sensor can significantly reduce power consumption and prolong battery lifetime.