The reverse speed sensor CS-3F can be used to detect the positive and negative rotation, rotational speed, linear speed, etc. of gears, racks and axles. The acceleration of the measured body can also be obtained through calculation and processing. The reverse speed sensor CS-3F has good low frequency and high frequency characteristics, and its low frequency can be as low as 0Hz, which can be used for the zero speed measurement of rotating machinery. Since the sensor can give two speed signals with a certain phase difference, it can be used for positive and negative rotation discrimination. The high frequency can be as high as 20 KHz, which can meet the high speed measurement requirements of most industrial fields.