SAW pressure sensor for vacuum control applications

Abstract

A new kind of surface acoustic wave (SAW) sensor has been developed in order to measure sub-atmospheric pressure below 100 mTorr with accuracy better than 0.1 mTorr. It provides an efficient measuring solution in a pressure range inaccessible in past by conventional diaphragm-based SAW sensors. Indeed, due to the small bending force in low pressure and limited sensitivity, diaphragm-based SAW sensors are only suited to monitor relatively high pressure with a precision hardly better than 0.5 Torr. In order to reach precision level better than 1 mTorr at sub-atmospheric pressure for vacuum technology applications, a radically different SAW-based solution is desired. Our device aims to measure sub-atmospheric pressure less than 100 mTorr with a threshold resolution better than 0.1 mTorr. The concept is similar to the one used by Pirani pressure gauges. However, it is claimed that a heated and suspended SAW device may have better sensitivity. A theoretical model based on the basic concepts of gas kinetic theory and thermodynamics is presented. The validity of the model is checked by comparison between theoretical and experimental results.

A Low-Cost, Nanowatt, Millimeter-Scale Memristive-Vacuum Sensor

“…Pressure sensors are widely used in space pressurized structures and environments. Various solutions in the literature enable to sense changes in the pressure from the atmospheric pressure (~760 Torr) down to high vacuum (~6.5 × 10 −6 Torr) [4][5][6][7][8][9][10][11]. These solutions are thermal sensors that depend on the heat transfer principle [7][8][9][10][11], or they rely on frequency shifts caused by damping variation under different pressures [4][5][6].…”

“…Various solutions in the literature enable to sense changes in the pressure from the atmospheric pressure (~760 Torr) down to high vacuum (~6.5 × 10 −6 Torr) [4][5][6][7][8][9][10][11]. These solutions are thermal sensors that depend on the heat transfer principle [7][8][9][10][11], or they rely on frequency shifts caused by damping variation under different pressures [4][5][6]. However, most of the proposed solutions operate at high power and require heavy and oversized circuitry to be used (see Table II), not being able to comply with low power, light weight, and small footprint requirements for mobile applications [1,2].…”