Pressure sensing cell using brittle diaphragm
First Claim
1. A differential pressure sensor assembly having first and second sensor portions;
- said first and second sensor portions each comprising a pair of plates, a first of which is a brittle semiconductor material, and a second of which is a rigid insulating material, said plates initially being substantially contiguous to each other along first surfaces of said plates and sealed together along an encompassing line with portions of said first surfaces being unconnected to permit movement of said first semiconductor plate of each sensor portion relative to the other plate of the same sensor portion to form first and second chambers, respectively, in each of the first and second sensor portions;
each of said second plates having capacitive electrode means on the first surfaces thereof facing said semiconductor plates of the respective sensor portion to permit measuring differences in spacing of said facing surfaces by measurement of capacitance between the semiconductor plate and the capacitive electrode;
fluid conduit means for connecting said first and second chambers, respectively;
a quantity of substantially incompressible fluid filling said first and second chambers and to said fluid conduit means to space the semiconductor plates from the second plates;
housing means to permit subjecting at least one of the plates of each sensor portion to a pressure tending to move the plates forming each sensor portion together, the pressure acting on the respective sensor portion being at least at times different from the pressure acting on the other sensor portion, whereby the incompressible fluid will be forced into one chamber from the other chamber and cause increase in bending stress of the plates in one of said sensor portions and a decrease in bending stress of the plates of the other sensor portion; and
said other sensor portion reaching a condition wherein the first and second surfaces of the plates forming the other chamber are substantially contiguous before either of the plates forming the one sensor portion reach an excessive stress level.
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Accused Products
Abstract
A capacitive sensing cell is adapted for manufacture in a batch process, and uses a substrate or base from a rigid insulating material such as glass and a diaphragm assembly of a brittle semiconductor. The diaphragm assembly and the substrate are anodically bonded together. A very shallow recess is formed on either the diaphragm or the substrate to accommodate a deposited capacitor plate. Two such assemblies are connected together and the assembly is filled with noncompressible fluid to slightly bow the diaphragms away from the substrates. Differential pressure between the diaphragm assemblies is sensed by detecting the relative positions of the two diaphragms.
71 Citations
31 Claims
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1. A differential pressure sensor assembly having first and second sensor portions;
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said first and second sensor portions each comprising a pair of plates, a first of which is a brittle semiconductor material, and a second of which is a rigid insulating material, said plates initially being substantially contiguous to each other along first surfaces of said plates and sealed together along an encompassing line with portions of said first surfaces being unconnected to permit movement of said first semiconductor plate of each sensor portion relative to the other plate of the same sensor portion to form first and second chambers, respectively, in each of the first and second sensor portions; each of said second plates having capacitive electrode means on the first surfaces thereof facing said semiconductor plates of the respective sensor portion to permit measuring differences in spacing of said facing surfaces by measurement of capacitance between the semiconductor plate and the capacitive electrode; fluid conduit means for connecting said first and second chambers, respectively; a quantity of substantially incompressible fluid filling said first and second chambers and to said fluid conduit means to space the semiconductor plates from the second plates; housing means to permit subjecting at least one of the plates of each sensor portion to a pressure tending to move the plates forming each sensor portion together, the pressure acting on the respective sensor portion being at least at times different from the pressure acting on the other sensor portion, whereby the incompressible fluid will be forced into one chamber from the other chamber and cause increase in bending stress of the plates in one of said sensor portions and a decrease in bending stress of the plates of the other sensor portion; and said other sensor portion reaching a condition wherein the first and second surfaces of the plates forming the other chamber are substantially contiguous before either of the plates forming the one sensor portion reach an excessive stress level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A differential pressue sensor assembly comprising:
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first and second pressure sensor cells, said first and second sensor cells each including a base of rigid insulating material and a brittle semiconductor diaphragm mounted on a surface of said base and fused to the base to enclose a chamber, an aperture formed through each base open to the center portion of the respective diaphragm; a housing enclosing each sensor cell and including rigid divider means for separating the sensor cells; means for defining a sealed passageway through the rigid divider means opening to the apertures in the bases of both sensing cells, said means for defining including supports to space the bases of the respective sensor cell from the divider means except adjacent the respective apertures to stress isolate the sensor cells with respect to the housing; a filling of substantially noncompressible fluid in said apertures and said passageway under a pressure sufficient to support the center portions of the respective diaphragm to be spaced from each of the bases to form fluid filled chambers, whereby pressure differentials on the outer surfaces of said diaphragms will tend to cause one of the diaphragms to move toward its respective base while the other diaphragm bows out further from its respective base; and means to permit sensing deflection of the center portion of at least one diaphragm relative to its associated base. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A capacitive differential pressure sensor assembly comprising first and second sensor elements mounted with respect to each other:
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said first and second sensor elements each including an insulating substrate plate, and a semiconductor diaphragm plate mounted on a surface of said substrate plate and bonded to the substrate to enclose the center portions of the diaphragm to form a chamber, an aperture through each substrate plate open to the center portion of the respective diaphragm plate;
means forming a fluid passageway coupling the openings in each of the substrate plates;a filling of substantially noncompressible fluid in said openings and passageways and under a pressure sufficient to support the respective diaphragm plates to be spaced from each of the substrate plates to form fluid filled chambers, whereby pressure differentials on the outer surfaces of said diaphragm plate will tend to cause one of the diaphragm plates to move toward its respective substrate plate, while the other diaphragm plate bows out further from its respective substrate plate; a capacitor electrode deposited on each substrate plate to form a capacitor in combination with the respective diaphragm plate to permit determining relative deflecting movement of the associated plates; each of the diaphragm plates contacting its substrate plate under pressure forces before the other diaphragm plate of the sensing cell is overstressed; and means to permit applying separate pressures to each of the diaphragm plates. - View Dependent Claims (24, 25, 26, 27, 28)
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- 29. A method of manufacturing diaphragm assemblies used for a fluid pressure sensor comprising steps of providing a sheet member of brittle material having a suitable thickness, forming a plurality of openings through said sheet member at spaced intervals, depositing a coating, including a conductive portion forming an electrode on the sheet member around each opening, and separated from the conductive coatings surrounding the other openings, positioning a semiconductor material wafer having a plurality of separated diaphragm members formed thereon with each diaphragm member overlying one of said electrodes and associated opening providing a recess on one of the members aligned with each deposited conductive coating when the wafer is positioned on the glass sheet, the recess being provided to have a depth substantially equal to the thickness of the deposited coating, anodically bonding the wafer and sheet member together in regions surrounding each of the diaphragm members, and separating the bonded sections of said sheet member and wafer along lines surrounding each of said diaphragm members.
Specification