Signal conditioning technique for magnetoelastic sensors

Abstract

Magnetoelastic materials are obtaining an increasing interest in the last few years. Magnetoelastic wave resonant frequency is the sensory parameter generally used to reliably obtain critical information, nevertheless, it was shown that wave amplitude also is very sensitive to measure displacements or magnetic fields. Both parameters, amplitude and resonance frequency could be used as the 'sensitive parameter' in no- contact vibration sensors or stress, flux or magnetic field sensors. To make them advantageous to be used, some problems should be solved: the excitation problem (to induce resonance) and the conversion problem (to transduce frequency or amplitude information into a convenient electric signal); in other words, the signal conditioning problem. The paper describes a signal conditioning technique for magnetoelastic sensors developed by using metallic glass materials. Analysis and synthesis phases of design for the signal-conditioning prototype are presented. From the frequency response analysis of a magnetoelastic metallic glass ribbon, a very low damping factor is pointed out. This means that a stationary oscillation could be easily induced into the ribbon and it was seen that the oscillation frequency changed when the boundary conditions (mechanical stress or magnetic field) changed. So, the ribbon can be used as a sensor. The proposed device (PLG 3) for the sensor signal conditioning is described in detail. Finally, PLG 3 plus a magnetoelastic sensor is used for a no contact vibration measurement and compared to the results from traditional tools.