An Asymmetric Micro-Three-Coil Sensor Enabling Non-Ferrous Metals Distinguishment

At present, when performing material identification of metal wear debris, most sensors can only roughly distinguish between ferromagnetic and non-ferromagnetic metal wear debris, but fail to distinguish them deeply. To achieve fine detection of metal wear debris in the oil, this article designs an asymmetric micro-three-coil sensor, which generates an asymmetric magnetic field by using two excitation coils of different sizes. Different metal wear debris are affected differently in the magnetic field and the shape of the output signal is also different, therefore, the wear debris material can be distinguished by the shape of the signal of the induction electric potential output from the induction coil alone, and the wear debris size can be determined by the amplitude of the signal. Copper particles, aluminum particles, iron particles, and 304 stainless steel particles were selected as experimental objects, and the experimental results showed that the material differentiation of these four types of particles can be achieved by the asymmetric magnetic field of the sensor. The method provides a new research direction for the inductive method to distinguish non-ferrous metals, which is important for the fine detection of multi-parameter pollutants and the diagnosis and monitoring of mechanical system faults.