Theoretical Investigation of Torque Measuring by a Vibration Motor in a Mobile Phone

In the precision technology always puts the measuring of way-out small torques trouble. There are not any commercially available special instruments to measure the torque. The task has to be solved with a non-contact method because the measuring system must not load the object. The measuring of intensive variables can be solved easily with a non-contact method but by extensive variables like the torque we have to provide for the circulating of the unknown quantity through the transducer (or sensor). The small size of the emissive instrument presents beyond the small value of the unknown quantity difficulty. The diameter of the motor is only 0.7 mm. By so conditions can be taken only such physical principle into account which ensures the non-contact method and it does not need more space such the unknown object itself. Non-contact method for measuring of small torque of vibration motors is presented in this paper. The possible errors its influences are discussed as well.