Design and experimental research of abrasive particle detection sensor based on coil magnetic field

Abstract This paper develops a dual-coil sensor integrated with high-permeability materials based on inductive sensor technology to detect wear particles in oil. This method is mainly used for online detection and fault analysis of pollutants in hydraulic and lubricating oil systems. The sensor innovatively embeds permalloy into the sensing unit of the sensor to generate high gradient magnetic field in the sensing area, consequently improving the detection sensitivity of the sensor. The detection unit consists of two pieces of permalloy and two plane coils. The permalloys have a rectangular groove at the center, which is placed in line with the inner hole of the coil, thereby forming the detection area. Particles in the microchannel can be detected as they flow through the detection area. The article theoretically analyzes the working principle of the sensor and establishes a verification experiment system. The experimental results show that after adding permalloy to the sensing unit, the signal-to-noise ratio (SNR) of iron particles is increased by more than 40%, and the SNR of copper particles is increased by more than 30%. As the particle size increases, the SNR decreases. Using this design, the range of the lower limit detection for ferromagnetic metal particles increased to 10–15 μm, while that of non-ferromagnetic metal particles increased to 60 μm. Compared with traditional inductive sensors, the addition of permalloy greatly improves the sensor's performance, which significantly boosts the sensitivity of the dual-coil type sensor.