Measurement of acoustic properties of liquid using liquid flow SH-SAW sensor system

The SH-SAW resonator having narrow bandwidth and higher Q value has been used for sensing the properties in ionic and viscosity of liquid. The surface acoustic waves with the shear horizontal displacement (SH-SAW) are excited on a piezoelectric substrate; 36 rotated Y cut X prop. LiTaO3 (36 YX LiTaO3) and the liquid flow sensing system was constructed by using two-port resonator on the substrate. The flow of a sample liquid was interacted with the SAW only on the cavity of the resonator. The resonator was connected in an amplifier, to construct an SH-SAW oscillator. The frequency changes of the SH-SAW oscillator were detected as a sensor response. Experimental results showed that the response of the SAW sensor varied with both the conductivity and the square root of product of the density and viscosity of the liquid. Transit responses of the SAW sensor system to the flow of the sample liquid also showed a specific feature. It was found that these quantities were very useful to determine the properties of liquid.