PRESSURE SENSOR BASED ON SAW RESONATORS

In this work, we present a pressure sensor based on surface acoustic wave (SAW) resonators operating in the pressure range from 0 to 3 bar. The sensing mechanism is related to changes in the elastic constants of the substrate and, hence, in SAW phase velocity, induced by the applied pressure. In order to determine the radius of the membrane, we used a finite element method (FEM) program, using the elastic constants of the anisotropic ST-x quartz, A differential configuration has been designed to reduce parasitic phenomena due to temperature variations. The SAW elements are two 2-ports resonators operating at approximately 393 MHz and opportunely positioned on the designed circular diaphragm. SAW resonators are used as frequency-control element in the feedback branch of a Pierce oscillator circuit. The frequency shifts of the oscillators, as consequence of pressure variations, are easily measured and reported. A resolution better than 4 Pa and a linear response curve are obtained.