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.
Highlights
Vacuum technology needs accurate pressure monitoring for different kinds of purposes, including thermal insulation and correct operation of manufacturing systems
A polymer housing crossed by the microchannel; A SAW–Pirani chip consisting of a block of lithium niobate with an interdigital transducer printed at its surface and a Joule resistance layer at its bottom; A heating coil encapsulated by liquid polymer which acts as a seal and controls the temperature; An interrogation antenna made with silver screen printing
The vacuum sensor presented here is new in the sense that it is extending the sensing range, while operating completely wirelessly
Summary
Vacuum technology needs accurate pressure monitoring for different kinds of purposes, including thermal insulation and correct operation of manufacturing systems. For instance, this enabled dramatic progress on several frontiers of contemporary electronics such as lifetime, precision, and reproducibility of devices that are currently ubiquitous This capability originates essentially from better production and process control relying on, amongst others, accurate pressure sensors. The pressure changes while the wire is being heated from a constant power source, a new thermal equilibrium is reached, and the temperature of the wire changes to indicate the new number of gas molecules that can carry heat away from it. This means that the temperature of the wire can be used as an indication of the pressure inside the chamber This is the basic principle of all thermal conductivity gauges to which Pirani sensors belong. The temperature variation is transduced into a precise voltage variation
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