Abstract
A magnetostrictive FeNi-coated surface acoustic wave (SAW)-based current sensor was proposed in this work. The weak remanence and hysteresis effect of the FeNi itself contributes to suppress the asymmetry in sensor response at increasing and decreasing current. The sensor response was simulated by solving the coupled electromechanical field equation in layered structure considering the magnetostrictive effect and an approach of effective dielectric constant. The effects from the aspect ratio and thickness of the FeNi film on sensor response were analyzed to determine the optimal design parameters. Differential oscillation structure was used to form the sensor, in which, the FeNi thin film was deposited along the SAW propagation of the sensor chip by using RF magnetron sputtering. The magnetostrictive effect of the FeNi coating induced by the magnetic loading generates the perturbation in SAW velocity, and corresponding oscillation frequency. High sensitivity of 10.7 KHz/A, good linearity and repeatability, lower hysteresis error of 0.97% were obtained from the developed prototype 150 MHz SAW FeNi coated current sensor.
Highlights
Surface acoustic wave (SAW)-based devices attracts increasing attention for various physical and chemical sensing because they offer some unique performances such as high sensitivity, excellent reproducibility, small size, simple structure, robustness, being passive, and remotely queried
Reindl et al reported a dexterous design of the configuration of the SAW magnetic/current sensor loaded with magnetoresistor sensor, where wireless and passive measurement for current was realized [16,17], and the obtained current resolution is approximately 5% of full scale (−800~800 A)
A FeNi-coated SAW based current sensor was constructed, which was composed of a differential SAW delay line oscillator configuration, and magnetostrictive FeNi thin film deposited along the SAW propagation path of the sensing device
Summary
Surface acoustic wave (SAW)-based devices attracts increasing attention for various physical and chemical sensing because they offer some unique performances such as high sensitivity, excellent reproducibility, small size, simple structure, robustness, being passive (batteryless), and remotely queried (wireless). Referring to the magnetostrictive thin film as the sensing material or magnetoresistor as the external loaded sensor, a new concept of SAW-based magnetic/current sensor were proposed, allowing possible features of fast response, high sensitivity, strong anti-interference, and small size. FeCo-coated SAW magnetic/current sensor using the differential oscillation structure was proposed in our previous work, where high sensitivity of 16.6 KHz/A was obtained [12]. A FeNi-coated SAW based current sensor was constructed, which was composed of a differential SAW delay line oscillator configuration, and magnetostrictive FeNi thin film deposited along the SAW propagation path of the sensing device.
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