Low pressure transducer using metal foil diaphragm
First Claim
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1. A low pressure capacitive transducer assembly comprising:
- a nonconductive plate having a substantially planar surface;
a thin electrically conductive layer deposited on said planar surface;
an epoxy layer silk-screened to form a border around said conductive layer on said planar surface;
a planar metal foil diaphragm member having a flat surface, said diaphragm member being positioned with said flat surface opposite said planar surface and with its periphery firmly in contact with said epoxy layer, but not in contact with said conductive layer;
the central area of said foil diaphragm member being free of engagement with other portions of said transducer assembly;
said foil diaphragm member being between 1/3 and 3 mils thick, and being spaced away from said conductive layer by a distance of between 1/2 mil and 20 mils;
a retaining member of approximately the shape of said epoxy layer, said retaining member engaging said diaphragm member on the opposite side thereof from said epoxy layer, such that the capacitance between said diaphragm member and said thin electrically conductive layer is at a predetermined level andmeans for detecting changes in the capacitance between said foil diaphragm member and said thin conductive layer.
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Abstract
A low pressure transducer is disclosed which utilizes a stainless steel foil diaphragm. An electrically conductive layer is deposited onto a non-conductive planar disk to form one plate of a capacitor. An epoxy ring is silk-screened onto the non-conductive plate to form an insulative washer between the stainless steel foil and the conductive layer on the non-conductive plate. A stainless steel ring is placed on top of the stainless steel foil and pressed down toward the non-conductive plate until the capacitance formed by the conductive layer screened onto the non-conductive plate and the stainless steel foil diaphragm reaches a predetermined level.
56 Citations
17 Claims
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1. A low pressure capacitive transducer assembly comprising:
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a nonconductive plate having a substantially planar surface; a thin electrically conductive layer deposited on said planar surface; an epoxy layer silk-screened to form a border around said conductive layer on said planar surface; a planar metal foil diaphragm member having a flat surface, said diaphragm member being positioned with said flat surface opposite said planar surface and with its periphery firmly in contact with said epoxy layer, but not in contact with said conductive layer; the central area of said foil diaphragm member being free of engagement with other portions of said transducer assembly; said foil diaphragm member being between 1/3 and 3 mils thick, and being spaced away from said conductive layer by a distance of between 1/2 mil and 20 mils; a retaining member of approximately the shape of said epoxy layer, said retaining member engaging said diaphragm member on the opposite side thereof from said epoxy layer, such that the capacitance between said diaphragm member and said thin electrically conductive layer is at a predetermined level and means for detecting changes in the capacitance between said foil diaphragm member and said thin conductive layer. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for forming a low pressure capacitive transducer comprising the steps of:
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depositing a thin electrically conductive plate on a planar surface of a nonconductive plate; silk-screening an epoxy layer slightly thicker than said electrically conductive plate around the marginal edge of said planar surface of said nonconductive plate; placing a foil diaphragm having a central area which is free of engagement with other parts of said transducer, on top of said epoxy layer; placing a retaining member of approximately the shape of said epoxy layer on top of said diaphragm member; and pressing said diaphragm member toward said thin electrically conductive plate with said retaining member until the capacitance between said diaphragm and said thin electrically conductive plate reaches a predetermined level, and said diaphragm and said conductive plate are spaced apart by a distance of between 1/2 and 20 mils. - View Dependent Claims (9)
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10. A low pressure capacitive transducer comprising:
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a nonconductive plate having a planar surface; a thin electrically conductive layer deposited on said planar surface; a planar metal foil diaphragm member having a flat surface, means for sealing the space between the outer edges of said diaphragm member and said plate, wherein said sealing means is a ring of epoxy around said conductive layer, and further comprising a circular member of approximately the shape of said epoxy ring, said circular member engaging said diaphragm member on the opposite side thereof from said epoxy layer, such that the capacitance between said diaphragm member and said thin electrically conductive layer is at a predetermined level, said diaphragm member being mounted with said flat surface opposite said planar surface and with its periphery firmly in contact with said epoxy but not in contact with said conductive layer; the central area of said foil diaphragm member being free of engagement with other portions of said transducer assembly; said foil diaphragm member being between 1/3 and 3 mils thick, and being spaced away from said conductive layer by a distance of between 1/2 mil and 20 units; and means for detecting changes in the capacitance between said foil diaphragm member and said thin conductive layer. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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Specification