Development of SH-SAW Sensing System for Liquids

Developments of sensors using surface acoustic wave (SAW) devices have been attractive. A shear horizontal SAW (SH-SAW) sensor can detect liquid properties and chemical reactions in liquid. For practical applications of the SAW sensor, it is necessary to discuss its properties. In this paper, the SH-SAW sensors with a floating electrode unidirectional transducer (FEUDT) or an interdigital transducer (IDT) are compared. Frequency-phase characteristics and frequency-insertion loss profiles are measured. Also, phase shift and amplitude ratio between sample and reference liquids are evaluated. The results indicate that the SH-SAW sensor with the FEUDT has suited for liquid measurements. Then the SH-SAW sensor with FEUDT is mounted in the SH-SAW sensing system. The system configuration is the same of a vector voltmeter measurement system. However, exclusive circuits are developed, so its size is reduced. Using the system, several liquids are measured.