Ferromagnetic sensors using PCB coils as sensing elements are becoming more and more mature.However,due to the structural limitations of PCB coil,ferromagnetic particles cannot pass through its detection area.In addition,there is no relevant research to confirm the accuracy of the PCB coil for the measurement of ferromagnetic particles.A new type of ferromagnetic sensor based on the principle of magnetic plug and inductance detection was proposed.The simulation model of the sensor was established by using the finite element simulation software COMSOL Multiphysics,and the magnetic field distribution of the PCB coil was simulated and analyzed.It is found that the magnetic field intensity on the surface of the PCB coil has good uniformity,and reducing the inner diameter of the PCB coil appropriately is beneficial for improving the magnetic field uniformity of the PCB coil.Based on the simulation results,five kinds of PCB coils with different sizes were designed,and the detection accuracy of the sensor was measured by experiments.Experimental results show that the sensor has good sensitivity and can effectively detect the ferromagnetic particles smaller than particle size of 100 μm.