Abstract
A surface acoustic wave (SAW) device is proposed for sensing current by employing the patterned FeGa thin film as the sensitive interface. The layered media structure of FeGa/SiO2/LiNbO3 was established to reveal the working principle of the sensors, and an SAW chip patterned by delay-line and operating at 150 MHz was fabricated photolithographically on 128° YX LiNbO3 substrate. The FeGa thin film with a larger magnetostrictive coefficient was sputtered onto the acoustic propagation path of the SAW chip to build the sensing device. The prepared device was connected into the differential oscillation loop to construct the current sensor. The FeGa thin film produces magnetostrictive strain and so-called ΔE effect at the magnetic field generated by the applied current, which modulates the SAW propagation velocity accordingly. The differential frequency signal was collected to characterize the measurand. Larger sensitivity of 37.9 kHz/A, low hysteresis error of 0.81%, excellent repeatability and stability were achieved in the experiments from the developed sensing device.
Highlights
Current sensors are widely used in current monitoring applications in smart grid line testing, metallurgical and power supplies, rail transit safety warnings and rescue, and power relay protection in industrial automation [1]
The specialized current sensing prototype employing the magnetoresistance effect was proposed firstly by Reindl et al The obtained current resolution was approximately 5% of full scale (−800 A~800 A) [6]. Another typical surface acoustic wave (SAW) current sensing device is built by depositing magnetostrictive thin film along the acoustic propagation path of the SAW chip
The magnetostrictive thin film produces magnetostrictive strain and so-called ∆E effect at the magnetic field generated by the applied current, which modulates the SAW propagation velocity
Summary
Current sensors are widely used in current monitoring applications in smart grid line testing, metallurgical and power supplies, rail transit safety warnings and rescue, and power relay protection in industrial automation [1]. Among the available sensing technologies, the surface acoustic wave (SAW) current sensor features fast response, simple structure, low cost, excellent resistance to interference, low power consumption, and long service life [2,3,4]. It can realize wireless and passive measurement means to improve system security [5,6,7]. Using the FeCo thin film as the sensitive interface, the SAW current sensor prototype was constructed successfully, a larger sensitivity of 16.6 kHz/A was achieved, and the patterned design was considered to improve the hysteresis error [1,8,9]. Working Principle Under the magnetic field generated by the applied current, the FeGa film produces magnetostrictive strain and so-called ∆E effect, which modulates the SAW propagation
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