一种采用IDT技术的新型微量液体密度传感器

A New Type of Liquid Density Sensor Using IDT Technics

新型微量液体密度传感器采用压电基片-液体层-压电基片结构。两个叉指换能器(IDT)分别位于压电基片-液体层-压电基片的两个液固界面上,压电基片保持平行且两个IDT处于相对的位置。一定条件之下第一个IDT在射频脉冲的激励下可只向液体层中辐射出高频超声脉冲,该超声脉冲在液体层中来回反射。液体层中来回反射的超声脉冲每次入射到起接收作用的第二个IDT上均有一个电脉冲信号输出。液体层密度值可用超声脉冲在液体层内来回传播一次的声时变化予以表征。通过测量第二个IDT输出的前两个电脉冲信号之间的时间间隔变化,即可得到相应的液体密度值。实验结果表明,采用压电基片-液体层-压电基片结构的微量液体密度传感器的敏感程度至少可达10-5g.cm-3/ns量级。

new type of minim liquid density sensor using a structure consisting of piezoelectric substrate-liquid layer-piezoelectric substrate has been examined in the present work. The two interdigital transducers （IDTs）are deposited at an interface of the structure respectively. The two piezoelectric substrates are parallel to each other and the two IDTs are positioned face to face. Under given conditions, the first IDT deposited at one interface and driven by a tone burst can generate a high frequency Acoustic Bulk Wave （BAW）pulse only into the liquid layer. The BAW pulse generated with the first IDT can reflect back and forth in the liquid layer between the two interfaces of the structure. There is an output of electrical pulse in the second IDT located on the other interface of the structure when the BAW pulse generated with the first IDT impinges on the location of the second IDT each time. The density of the liquid layer between the two piezoelectric substrates can be characterized by the change of transient time of a round trip of the BAW pulse. The density of the liquid layer can be obtained by measuring the change of the interval between the first two electrical pulses from the second IDT. The experimental results show that the minim liquid density sensor consisting of piezoelectric substrate-liquid layer-piezoelectric substrate has at least a measurement sensitivity of 10^-5g·cm^-3/ns.