Patent attributes
A pressure sensing device (10, 40) is shown having a ceramic capacitive sensing element (12) received in a chamber formed in a hexport housing (16). The hexport housing has a fluid passageway (16c) communicating with a recessed chamber (16d) formed in a bottom wall circumscribed by an annular platform shoulder (16e). A thin flexible metal diaphragm (18) is hermetically attached to the bottom wall along the platform shoulder. A curable adhesive resin having a thermal coefficient of expansion and modulus of elasticity appropriately matching that of sensing element (12), such as polyurethane, is cast between the sensing element (12) and the metal diaphragm (18) forming, when cured, a layer bonded to both members resulting in a sensor that is effective in monitoring negative as well as positive fluid pressures. In one embodiment a ring is used to define layer 20 laterally and in a second embodiment an insulator sleeve (44) and shield sleeve (42) which receives pressure sensing element (12) each have an open end with an inwardly extending lip (44b, 42b) that define layer 20 laterally.
