Ferromagnetic Metal Particle Detection Including Calculation of Particle Magnetic Permeability Based on Micro Inductive Sensor

As the working medium of machine, lubrication oil system is a very important component, which can be used to judge the operating conditions of machine, moreover, lubricating oil detection can eliminate the need for costly machine shutdowns for inspection. Metal particle is the most important parameter in lubrication oil detection. Inductance detection is one of the commonly used metal particle detection methods, with the development of micro fabrication technology, which can measure the sizes of metal particles and count the particles. In this paper, the model of ferromagnetic metal particle detection is established based on micro inductive sensor. It is obtained that the inductance change rate is proportional to the magnetic permeability of the metal particle and the cube of the particle size of metal particle. The tests about the metal particles with five different diameters are carried out, it is obtained that the theoretical values are in good agreement with the experimental values, the relative errors are less than 9.47%. And combined with experimental research, the magnetic permeability of ferromagnetic metal particles μ 3.907 × 10
⁴
H/m, 4.246 × 10
⁴
H/m, 4.092 × 10
⁴
H/m, 3.718 × 10
⁴
H/m, 4.07 × 10
⁴
H/m and 4.4289 × 10
⁴
H/m is obtained when the radii of particles are 25 μm, 50 μm, 100 μm, 200 μm, 500 μm and 1 mm, the relative errors E
_r
= |1 - μ/μAVG| are less than 8.82%.