An inductive monitoring method leveraging tunable mixing phase difference for wear debris inspection

In order to improve the feasibility and accuracy of inductive oil debris monitoring method for metal debris, lock-in amplifier (LIA) technology integrated with two digital frequency synthesizers is developed to enhance the wear monitoring capability of an inductive sensor under different Mixing Phase Difference (MPD). This new method leverages two adjustable digital synthesis chips to generate both an excitation signal and a square wave reference signal, therefore improving the signal-to-noise ratio (SNR) of debris signals. Moreover, with adjusting the MPD, variations in debris signal amplitude across different material types are examined in this study. Experimental results reveal substantial distinctions are achieved by determining the optimal MPD among different debris materials. Taking copper debris as an example, an appropriate adjustment increases the signal amplitude by as much as 3.48 times, demonstrating the remarkable sensitivity enhancement enabled by the approach. As a result, the proposed method is capable of effectively detecting iron debris as small as 80 μm and copper debris down to 200 μm in a piping system containing 13-mm diameter pipes.