Development of a novel SAW current sensor based on the magnetostrictive effect

This paper developed a novel surface acoustic wave (SAW) current sensor utilizing the magnetostrictive effect. The sensor was composed of a differential delay-line oscillation configuration, and a magnetostrictive FeCo film coated onto the surface of the sensing SAW device. The FeCo coating produces magnetostrictive strain under the magnetic field induced by the applied current, then, leading to changes in the SAW propagation velocity. Hence, the corresponding differential oscillation frequency shift was used to evaluate the applied current. To realize better temperature compensation, a SiO₂ thin film was deposited onto the SAW device surface, which exhibits opposing polarity of temperature coefficient of frequency (Tcf) to the LiNbO₃ substrate used in the SAW device. Using the Helmholtz coil, the developed SAW current sensor was characterized, high sensitivity, and good linearity were observed in the current experiment.