Capacitance manometer having a relatively thick flush diaphragm under tension to provide low hysteresis
First Claim
1. A capacitance diaphragm manometer comprising:
- a body structure having a front surface and a rear surface;
at least one electrode positioned through the body structure, the electrode having a front face substantially flush with the front surface;
a ring-shaped shim positioned on the front surface of the body structure, the shim having a thickness; and
a diaphragm having a first surface and a second surface, the first surface positioned on the shim and spaced apart from the front surface of the body structure by the thickness of the shim, the first surface of the diaphragm fixed to the shim under tension, the second surface of the diaphragm being a completely smooth and unobstructed exposed surface.
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Accused Products
Abstract
A capacitance diaphragm gauge (CDG) for measuring pressure includes a flush diaphragm mounted to a body structure via a shim or other raised perimeter portion. The diaphragm and the shim are welded to the body structure while the diaphragm is maintained at an elevated temperature. Contraction of the diaphragm as it cools pretensions the diaphragm to substantially reduce hysteresis effects. An electrode advantageously includes two portions with one portion providing excellent bonding characteristics and the other portion having temperature characteristics corresponding to the body structure and the diaphragm. An alternative CDG includes two identical electrodes with a first electrode positioned proximate to the center of the diaphragm and with a second electrode positioned proximate to the perimeter of the diaphragm. The second electrode provides a second capacitance signal that is used to compensate for changes in capacitance between the diaphragm and the first electrode caused by temperature changes.
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Citations
6 Claims
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1. A capacitance diaphragm manometer comprising:
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a body structure having a front surface and a rear surface;
at least one electrode positioned through the body structure, the electrode having a front face substantially flush with the front surface;
a ring-shaped shim positioned on the front surface of the body structure, the shim having a thickness; and
a diaphragm having a first surface and a second surface, the first surface positioned on the shim and spaced apart from the front surface of the body structure by the thickness of the shim, the first surface of the diaphragm fixed to the shim under tension, the second surface of the diaphragm being a completely smooth and unobstructed exposed surface. - View Dependent Claims (2)
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3. A capacitance diaphragm manometer comprising:
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a body structure having a front surface and a rear surface, the front surface having a substantially flat central portion and being bounded by a raised perimeter portion having a thickness perpendicular to the flat central portion;
at least one electrode positioned through the body structure, the electrode having a front face substantially flush with the front surface; and
a diaphragm having a first surface and a second surface, the first surface positioned on the raised perimeter portion and spaced apart from the front surface of the body structure by the thickness of the raised perimeter portion, the first surface of the diaphragm fixed to the raised perimeter portion under tension, the second surface of the diaphragm being a completely smooth and unobstructed exposed surface. - View Dependent Claims (4)
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5. A capacitance diaphragm manometer comprising:
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a body structure having a front surface and a rear surface, the front surface having a substantially flat central portion and being bounded by a raised perimeter portion having a thickness perpendicular to the flat central portion;
a first electrode positioned through the body structure, the first electrode having a cylindrical body with a front face substantially flush with the front surface, the first electrode being located approximately at the center of the front surface, the front face of the first electrode having a size and a shape;
a second electrode positioned through the body structure, the second electrode having a cylindrical body with a front face substantially flush with the front surface, the second electrode being located proximate to the perimeter of the front surface, the front face of the second electrode having a size and a shape substantially the same as the size and the shape of the first electrode; and
a diaphragm having a first surface and a second surface, the first surface positioned on the raised perimeter portion and spaced apart from the front surface of the body structure by the thickness of the raised perimeter portion, the first surface of the diaphragm fixed to the raised perimeter portion under tension, the second surface of the diaphragm being a completely smooth and unobstructed exposed surface. - View Dependent Claims (6)
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Specification