Low pressure transducer using metal foil diaphragm

Claim 2

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 and means for detecting changes in the capacitance between said foil diaphragm member and said thin conductive layer.

Claim 3

A low pressure capacitive transducer assembly as defined in claim 1 wherein said foil diaphragm member is a stainless steel foil.

Claim 4

A low pressure capacitive transducer assembly as defined by claim 1 wherein said retaining member is comprised of a steel washer.

Claim 5

A low pressure capacitive transducer assembly as defined by claim 1, wherein said assembly includes an electronic circuit for producing a signal which is linearly related to the capacitance between said thin electrically conductive plate and said diaphragm member.

Claim 6

A low pressure capacitive transducer as defined by claim 1 wherein said epoxy layer is slightly thicker than said electrically conductive plate.

Claim 7

A low pressure capacitive transducer as defined by claim 1 wherein said nonconductive plate is made of alumina.

Claim 8

A low pressure capacitive transducer as defined by claim 1 wherein first and second thin electrically conductive plates are deposited on said planar surface of said nonconductive plate, with said first conductive plate being essentially circular in shape with an electrically conductive lead, and said second plate forming a ring around said first plate and also having an electrical lead.

Claim 11

A method defined in claim 8 wherein the depositing of the thin electrically conductive plate further comprises the step of depositing a first conductive plate and a second plate, wherein said first and second plates do not overlap.

Claim 12

A low pressure capacitive transducer comprising: 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.

Claim 13

A low pressure capacitive transducer comprising: 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.

Claim 14

A low pressure capacitive transducer as defined by claim 10 wherein said circular member is comprised of a steel washer.

Claim 15

A low pressure capacitive transducer as defined by claim 10 further comprising an electronic circuit for producing a signal which is linearly related to the capacitance between said thin electrically conductive layer and said diaphragm member.

Claim 16

A low pressure capacitive transducer as defined by claim 10 wherein said ring of epoxy is slightly thicker than said electrically conductive layer.

Claim 17

A low pressure capacitive transducer as defined by claim 10 wherein said nonconductive plate is made of alumina.

Claim 18

A low pressure capacitive transducer as defined by claim 10, including two spaced conductive layers on said plate and wherein said first conductive layer is essentially circular in shape with an extension to an electrically conductive lead, and said second conductive plate forms a broken ring around said first plate and also having an extension to an electrical lead, and said extension of said first conductive plate extends through a break in said ring of said second conductive plate.

Claim 19

A low pressure transducer as defined in claim 11 wherein said circular member is a stainless steel washer.

Claim 20

A low pressure capacitive transducer as defined in claim 10 wherein said ring of epoxy is a silk-screened ring of epoxy.