Pressure sensor with improved capacitive pressure transducer

Claim 1

A pressure sensor comprising a capacitive pressure transducer having a ceramic substrate, a first electrically conductive capacitor plate secured to one surface of the substrate, a flexible ceramic sheet forming a diaphragm, a second electrically conductive capacitor plate secured to one surface of the flexible ceramic sheet, a mixture of a glass frit fusible at one temperature and of a plurality of elements with portions of a selected diameter of a material which retains its shape at said one temperature disposed between portions of said one surface of the ceramic substrate and the flexible ceramic sheet member for disposing the first and second capacitor plates in precisely spaced relation to each other as determined by the diameter of said element portions to form a capacitor, the glass frit being fused at said one temperature for securing the first and second capacitor plates in said precisely spaced relation to permit the second capacitor plate to be movable in response to application of pressure to an opposite surface of the flexible ceramic sheet for varying the capacitance of the capacitor in response to changes in pressures applied to the flexible ceramic sheet, and connector means for electrically connecting the first and second capacitor plates in an electrical circuit; support means attached to the transducer forming a chamber between the support means and transducer for mounting the transducer to be exposed to a pressure in a zone to be monitored; and electrical circuit means disposed in the chamber and electrically connected to said connector means for providing an electrical signal corresponding to said pressure changes; the support means comprising housing means having an opening therein for exposing the flexible ceramic sheet of the transducer to said fluid pressure and seal means between the transducer and housing means sealing the electrical circuit means within the chamber from said fluid pressure.