基于磁致伸缩效应的声表面波电流传感器敏感机理分析

The Sensitive Mechanism of SAW Current Sensor Based on the Magnetomechanics Effect

为实现高灵敏度、低温漂的高性能电流传感器,提出将声表面波技术与磁致伸缩效应相结合的电流检测方法,分析了其敏感机理并改善其温度特性。这种声表面波电流传感器采用128°YX-Li Nb O3作为压电基片,表面覆盖SiO_2薄膜来改善器件温度稳定性,并溅射超磁致伸缩Tb Dy Fe薄膜以响应电流。在电流作用下,Tb Dy Fe薄膜会发生磁致伸缩效应和ΔE效应,引起声表面波相速度的改变。结合层状介质中声传播理论,分析了给定电流下层状结构中声表面波的传播特性,特别分析了Tb Dy Fe和SiO_2膜厚对传感器响应的影响。计算结果表明,Tb Dy Fe和SiO_2薄膜厚度分别为0.5μm、2μm时,该声表面波电流传感器具有最大检测灵敏度58.2 k Hz/A,有良好温度稳定性和较高的灵敏度,从而为高性能声表面波电流传感器的研制奠定理论基础。

In order to achieve a kind of high-performance current sensor with high sensitivity and low temperature drift,this paper put forward a kind of new current detection method combined the surface acoustic wave（ SAW） technology with magnetostrictive effect,analyzed its sensitive mechanism and improved its temperature characteristic.This SAW current sensor used 128° YX-LiNbO3 as piezoelectric substrate,and SiO2film whose temperature coefficient polarity is opposite to improve the temperature stability,and one of the SAW delay lines was sputtered with giant magneto strictive Tb Dy Fe film to detect current. The applied current induces the Tb Dy Fe film＇s magneto strictive strain and ΔE effect,changes the SAW propagation characteristics. Based on the theory of acousticwave propagation in layered medium,this paper analyzed the SAW propagation characteristics in the Tb Dy Fe film/SiO2/piezoelectric substrate layered structure under given current conditions,especially analyzed the effects of Tb Dy Fe and SiO2film thicknesson sensor response. The results show that the highest sensitivity can reaches 58.2 k Hz/A when the Tb Dy Fe and SiO2thin film thickness are respectively 0.5 μm and 2 μm,which shows excellent temperature stability and high sensitivity.