A giant magneto-inductive sensor for measuring high rotational speed of brushed and brushless direct-current motors

There is a paucity of research on measurement of high rotational speed of direct-current motors using giant magneto-inductive sensors. In this work, measurements of high rotation-speed of brushed and brushless direct-current motors were realized by using a magneto-inductive sensing system. Successive square waves and sawtooth waves were observed when the rotation shafts of the motors pass by the giant magneto-inductive sensor. High rotational speed of 51000 r/min was accurately measured with a large distance of 9 cm between the giant magneto-inductive sensor and the rotation shafts, outputting a high voltage response of 5 V. The magneto-inductive sensing system displays a great potential application in ultrasensitive rotational speed measurements.