An Embedded Surface Acoustic Wave Pressure Sensor for Monitoring Civil Engineering Structures

This paper proposes a novel embedded surface acoustic wave (SAW) pressure sensor for monitoring civil engineering structures. The sensor consists of a pressure cell and a sensing chip in a metal housing. The whole interior of the sensor is filled with silicone oil for pressure transfer. The sensing chip is a SAW die packaged in a seal cavity to monitor the pressure of the silicone oil. Therefore, the external pressure applied to the cell can be detected by this method. In order to optimize the structure, the strain behavior and pressure measurement of the SAW device are analyzed in detail. The positions of the inter-digital transducer and reflectors on the SAW substrate are designed deliberately. The SAW device is fabricated by a lift-off process. The sensor is characterized by a network analyzer. The pressure sensitivity tested is 0.4°/kPa and the nonlinearity is 1.02%. The maximum absolute error is 2.9° in the range of 0-500 kPa.