A Multi-Contaminants Detection Sensor Based on Digital Lock-In Amplifier Module With High Sensitivity and High Detectability

Wear debris monitoring in lubrication oil has emerged as a promising solution for health monitoring and fault diagnosis of mechanical equipment. However, the debris feature signal is weak and overwhelmed in the noise. Furthermore, the traditional inductive detection sensors suffer from poor detectability to distinguish nonferromagnetic metal particles. To address these problems, in this article, a triple-coil inductive debris sensor combined with a digital lock-in amplifier (DLIA) module was proposed to detect and distinguish multiple contaminants in hydraulic oil so as to achieve high sensitivity and high detectability. First, we introduced the sensor design and fabrication. Second, the triple-coil inductive debris sensor model, the DLIA principle, and the performance analysis of suppressing noise for lock-in amplifier (LIA) were provided, respectively. Finally, both the simulation and experimental platforms were built to substantiate the effectiveness of the proposed approach. Experimental results showed that the detection limit of the designed sensor for iron, copper, and aluminum particles could be inferred as 85.4, 102.4, and $111.6 \mu \text{m}$ , respectively.