This paper presents the development of a novel position measuring method for rotational oscillating biomedical device Ros-Drill (c). This micro driller device has a micro brushless motor that never takes a full turn, just rotationally oscillates. The measuring method basically depends on the principle that one phase of brushless motor is always non-fed and can be used to measure the back-EMF voltage whose value is proportional to motor speed. The measuring technique and control algorithm are implemented via a digital signal processor, dSPACE 1104. The experiments reveal that the method is suitable for biomedical applications needing piercing operations with rotational oscillations and it shows satisfactory performance in terms of wide range of operation frequency.