Thickness sensor for ferromagnetic sheets

Abstract

The paper presents a novel design and development of a resonant sensor to measure thickness of ferromagnetic sheets and their alloys. The sensor is built with cantilever beam as a resonator with electromagnetic excitation and piezoelectric sensing in closed loop electronics. The sensor measures the unknown thickness by measuring the resonance frequency of the resonator. The magnetic force due to the magnetic field interaction between electromagnet and ferromagnetic sheet will make the resonator at resonance. The resonator vibrates at different resonance frequencies depending on the thickness of the ferromagnetic sheet. The shift in resonance frequency for a change in thickness is detected by closed loop electronics. The proposed system is simple and varies linearly with thickness in the given measurement range and the sensitivity is improved by increasing the magnetic field strength of the electromagnet.