利用声体波反射效应的液体密度声传感器

Liquid Density Sensor Employingthe Effect of the Reflection of Bulk Acoustic Waves

研究了一种新型的液体密度声传感器，其结构为压电基片－液体层－各向同性固体板。在特定取向压电基片的背离液体层的表面上有两个叉指换能器，选择恰当的叉指换能器激励频率，可得到较强的声体波响应。叉指换能器激励的声体波在传感器对应的层状结构中来回反射，液体层密度的变化，将从输出叉指换能器的相位或群延时中得到反映。实验结果表明，对于蒸馏水溶液，当其密度相对变化为１０－６时能予以分辨。

The structure of the liquid density sensor studied in the present paper is: piezoelectric substrateliquid layerisotropic plate.Two interdigital transducers(IDTs)are positioned on the surface of special orientated piezoelectric substrate deviating from liquid layer.The bulk acoustic waves(BAWs)generated by the input IDT will reflected back and forth in the layered structure of the sensor.By selecting proper IDT excitation frequency the most intensive response of BAWs may be obtained in the output IDT.The phase or group delay time of output IDT will alter along with the change of density of the liquid to be measured.In the process of actual experiment the sensor is used to determine the relative change of the density of the liquid(distilled water).The result shows that the resolution of the sensor is 106。