Design and Simulation of a Wireless SAW–Pirani Sensor with Extended Range and Sensitivity

Abstract

Pressure is a critical parameter for a large number of industrial processes. The vacuum industry relies on accurate pressure measurement and control. A new compact wireless vacuum sensor was designed and simulated and is presented in this publication. The sensor combines the Pirani principle and Surface Acoustic Waves, and it extends the vacuum sensed range to between 10−4 Pa and 105 Pa all along a complete wireless operation. A thermal analysis was performed based on gas kinetic theory, aiming to optimize the thermal conductivity and the Knudsen regime of the device. Theoretical analysis and simulation allowed designing the structure of the sensor and its dimensions to ensure the highest sensitivity through the whole sensing range and to build a model that simulates the behavior of the sensor under vacuum. A completely new design and a model simulating the behavior of the sensor from high vacuum to atmospheric pressure were established.

Characterization of a Wireless Vacuum Sensor Prototype Based on the SAW-Pirani Principle

“…The sensitivity constantly decreased with the pressure according to the expectations between approximately 42 kHz/Pa at 0.9 Pa and 1 Hz/Pa at atmospheric pressure. The sensitivity is higher in the rough vacuum area between the minimum pressure and 200 Pa approximately corresponding to the limit between the Knudsen regime and the transition regime [8], which corresponds of Knudsen number close to 1 [10]. The Knudsen regime is not explained in detail here but in [11].…”

“…The response of the sensor to the pressure is non linear. First of all the Pirani sensing curve has a characteristic S-shape [8] due to the nonlinear relationship between the gas thermal conductivity and pressure. However, eliminating thermal losses, eliminating the offset of the signal and applying a proper algorithm to the output signal may significantly increase the sensor linearity.…”

“…With this in mind, a miniaturised wireless vacuum sensor with extended range and sensitivity was designed, simulated and prototyped [8,9]. The assembly of a prototype entailed challenges linked to the operation of two different electromagnetic waves, the miniaturization of all the components and wireless power transfer in a vacuum environment while most components were made of stainless steel.…”

Toward a Compact Wireless Surface Acoustic Wave Pirani Microsensor with Extended Range and Sensitivity

“…In the wake of the concept of the SAW-Pirani for extending the sensing range of vacuum sensors [7][8][9] and the miniaturization of wireless power transfer systems, the development of a wireless vacuum micro sensor with extended range is discussed. The structural design is followed by the simulation of each component.…”

Effect of IDT position parameters on SAW yarn tension sensor sensitivity

“…[1][2][3][4] Because SAW sensors are particularly sensitive to the environmental changes on the substrate surface, they are widely used in the detection of physical, 5 chemical, 6 and biological 7 data. With the continuous increase in SAW sensor applications, the study of the aspects of theoretical enrichment, 8,9 working mechanism innovation, 10 simulation model improvement, 11 and working performance development 12 for SAW sensors has become a hot research topic.…”