A High-Sensitivity and High-Throughput Inductive Sensor for Abrasive Particle Detection Using Rectangular Coils

The analysis of wear particles within machinery lubricants constitutes a critical methodology for assessing equipment health and enabling the early identification of potential failures. However, conventional inductive abrasive particle sensors typically exhibit lower detection sensitivity compared to other sensing technologies, limiting their practical application in precision condition monitoring. To address this limitation, this paper introduces an inductive abrasive particle sensor with enhanced sensitivity and throughput, employing rectangular coils, together with a custom-designed signal conditioning circuit. The sensor features two symmetrically arranged rectangular excitation coils and two symmetrically arranged rectangular sensing coils, with their respective axes mutually perpendicular. This unique spatial configuration not only ensures strong magnetic field intensity within the detection region but also significantly enhances magnetic field utilization efficiency. The sensing coils are connected in a differential output configuration to improve the common-mode rejection ratio, thereby enhancing the sensor's immunity to environmental interference. Furthermore, a specifically designed compensation circuit effectively counteracts the inherent unbalanced output of the probe, ensuring stable sensor operation. Subsequent the signal conditioning circuit successfully extracts weak particle signals from the sensor output while effectively suppressing noise interference and improving the signal-to-noise ratio. This paper also develops a comprehensive mathematical model for the proposed sensor, providing theoretical validation of the structural superiority. Experimental results reveal that the sensor can reliably detect ferromagnetic particles as small as 130 μm and non-ferromagnetic particles as small as 184 μm within a flow conduit of 7.2 mm equivalent diameter, maintaining high sensitivity while providing substantial flow throughput of 4.88 L/min.