SAW Pressure Sensor Based on Diaphragm–Pirani Composite Sensing Mechanism: For Cross-Scale Measurement Range Extension

Surface acoustic wave (SAW) pressure sensors are widely applied for their strong environmental adaptability, ease of wireless integration, and low cost. With the extension of atmospheric observation into near-space environments, there is a growing demand for cross-scale pressure measurements ranging from pascals to hundreds of kilopascals. However, conventional SAW pressure sensors based on a single sensing mechanism face limitations in meeting this demand. Integrating diaphragm-type and Pirani-type sensing mechanisms offers a promising approach, yet balancing their sensitivities across pressure ranges remains challenging due to conflicting temperature coefficient of frequency (TCF) requirements. To address this issue, this study proposes an SAW pressure sensor based on a composite diaphragm-Pirani sensing mechanism, incorporating a differential decoupling structure and suspended packaging to enable high sensitivity across the pressure scales. Based on the established composite sensing model, the sensor was designed, fabricated, and evaluated using a pressure-temperature integrated test system. Experimental results demonstrate that the sensor achieves sensitivities of 21.03 ppm/Pa (5–100 Pa), 1.01 ppm/Pa (100 Pa–1 kPa), and 3.17 ppm/kPa (1–200 kPa), effectively addressing the limitations of existing technologies in cross-scale pressure sensing. Furthermore, an adaptive range-switching strategy was implemented to enable smooth transition between different measurement modes.