Ultrasensitive Inductive Debris Sensor With a Two-Stage Autoasymmetrical Compensation Circuit

Inductive oil debris sensors have been widely used in the health monitoring of mechanical equipment. Such sensors are important for fault diagnosis, life prediction, and prevention of catastrophic failures. In this article, the concept that the residual voltage caused by the asymmetry of two incentive coils hinders the improvement of the sensor resolution is theoretically demonstrated for the first time. In order to achieve ultrasensitive detection, a novel two-stage autoasymmetrical compensation circuit (AACC) is introduced into the triple-coil debris sensor to automatically suppress the residual voltage in real time. The experimental results show the successful detection of 70
μ
m (diameter or
D
) ferrous particles and 165
μ
m (
D
) nonferrous particles in a sensing channel with a diameter of 43 mm. The AACC is verified effectively to maintain the residual voltage at an ultrasmall value even in the presence of environmental fluctuations, and the sensitivity of the sensor using AACC is more than 31 times that of the sensor without AACC.