Importance

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Abstract

A pressure sensor device 10 comprises three layers 11a, 12 and 11b of silicon, fusion-bonded together. The outer layers 11a and 11b form a sealed housing around the central layer 12 to which they are bonded, and in use a cavity 13 between the housing 11a, 11b and central layer 12 is evacuated. The sensor device 10 is normally placed inside a component for containment of a pressurised fluid (not shown). Due to the cross-sectional shape of the device 10, pressure exerted by the fluid causes the layers 11a and 11b to flex inwardly in the region of minimum cross-sectional dimension and thereby outwardly in the region of maximum cross-sectional dimension, thereby is placing under tension a balanced twin beam vibratable element 16 on the central layer 12. The tension across the vibratable element affects its resonant frequency of vibration. Accordingly by accurately measuring the resonant frequency of vibration of the element, and by comparing this to previous calibration data, the magnitude of the pressure exerted on the layers 11a and 11b may be determined. The device may be made in other materials such as quartz and/or include temperature compensation facilities.

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First Claim