The core component of Kejit gear speed sensor uses magnetoresistance as the detection component, and then uses a new signal processing circuit to reduce noise and improve functions. By comparing with the output waveforms of other types of tooth speed sensors, the error of the measured speed is extremely small and the linear characteristics are very consistent. The sensing objects are magnetic materials or magnetically permeable materials, such as magnetic steel, iron and electrical steel. When the magnetic or permeable material with protrusions (or depressions) on the measured object rotates as the measured object, the sensor outputs a pulse signal related to the rotation frequency to achieve the purpose of speed measurement or displacement detection.