A High-Performance Weighing Sensor Based on Surface Acoustic Wave Technology

This article presents a passive wireless weighing sensor based on surface acoustic wave (SAW) technology. It consists of a one-port SAW sensing resonator and force-sensitive structure. Stable temperature (ST)-cut quartz was employed as the piezoelectric substrate of the SAW sensing resonator, and the sensing characteristics of the SAW sensitive resonator were simulated by the finite element method (FEM). The double-connected holes structure was proposed to form a difference sensing unit, which improves the sensitivity of the sensor and can counteract the effects of ambient temperature. Based on the designed force-sensitive structure and SAW sensing resonator, a wireless passive SAW weighing test platform was built and tested. The experimental result shows that the sensor is consistent with the design expectation. The sensitivity of the weighing sensor is 75.35 kHz/kg, and the nonlinear error is 0.17%. Under consecutive loading and unloading of 0–5 kg, the hysteresis is 1.1% and the maximum standard deviation of repeatability under the same load is 2.277 kHz (about 0.6% of the full-scale frequency shift). The difference structure effectively improves the sensitivity and has a good ambient temperature inhibition effect. Under a temperature of 30 °C–60 °C, the frequency shift is within 3 kHz, which is 0.8% of the full scale.