Abstract: Hydraulic oil is the key medium of mechanical equipment. The wear debris carried in hydraulic oil can reflect the operating state of the equipment, effectively predict the early failure of the equipment, and achieve predictive maintenance. In order to monitor the wear debris in hydraulic oil, an impedance sensor with multi-coil is designed and studied. The silicon steel strips are used to enhance the magnetic field strength of the detection region, the rectangular channels can make full use of the magnetic field distribution region, thereby improving the detection sensitivity and throughput of the sensor. The comparison experiment of series-parallel coils shows that the sensor has higher detection sensitivity and is more suitable to detect wear debris when the coils are connected in series in the same direction. The impedance sensor with multi-coil can judge the properties of the metal debris according to the direction of the inductance signal and the presence or absence of the resistance and inductance signals. The smallest metal debris that can be detected and distinguished by the sensor are 46 μm iron particle and 110 μm copper particle. The impedance debris sensor can obtain more accurate debris information based on the two parameters of inductance and resistance, which makes up for the insufficiency of the limited accuracy of traditional inductance sensors for non-ferromagnetic metal debris.

Key words: impedance sensor, wear debris, hydraulic oil, multi-coil