Pressure transducer apparatus

• US 5,485,345 A
• Filed: 11/14/1994
• Issued: 01/16/1996
• Est. Priority Date: 11/14/1994
• Status: Expired due to Fees

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Kawate, Keith W., Bishop, Robert P., Southworth, Robert O., Lukasiewicz, Stanley J.
• Primary Examiner(s): Ledynh, Bot L.
• Application Number:
  US08/339,039
• Time in Patent Office: 428 Days
• Field of Search: 361/283.1, 361/283.2, 361/283.3, 361/283.4, 73/718, 73/724
• US Class Current: 361/283.3
• CPC Class Codes: G01L 13/026 involving double diaphragm
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass

Abstract

A monolithic capacitive differential pressure transducer (10, 44,) is shown composed of ceramic material having first and second cavities formed adjacent to opposed face surfaces to form first and second flexible diaphragms (12, 14; 50, 52) and a motion transfer pin (24, 58) attached to and extending between the diaphragms. Capacitor plates are disposed on a surface of at least one flexible diaphragm and a stationary member to form a capacitive gap. Component parts are first pressed from ceramic powder and assembled into a unit using one of several methods including relatively high pressure to press them together or using a combination of low pressure along with raising the temperature of the material to soften the binder in the ceramic material at surfaces of the parts which are to be joined together. Selected gaps, both along the x-y direction and along the z direction may be obtained, particularly in assembling the parts using high pressure using consumable spacer material which is sublimated in a debinderization cycle prior to sintering of the unit to form a monolithic body.

Claims

1. A differential pressure transducer having a top surface and a bottom surface, a first recess formed adjacent to the top surface and a second recess formed adjacent to the bottom surface, the recesses each having a bottom wall, first and second diaphragm portions closing the respective first and second recesses, a passage extending between the first and second recesses, a motion transfer pin having opposite ends, one end integrally attached to a central part of the first diaphragm portion and the other end integrally attached to a central part of the second diaphragm portion, first and second capacitor plates disposed in at least one recess on a respective diaphragm portion and bottom wall spaced from one another to form a selected gap therebetween, means to electrically energize the capacitor plates and means to compensate for error due to common mode pressure subjected to the first and second diaphragm portions.

2. A differential pressure transducer according to claim 1 in which the means to compensate for error due to common mode pressure comprises the first and second diaphragm portions having unequal areas.

3. A differential pressure transducer according to claim 1 in which the first capacitor plate is disposed on the first diaphragm portion and the means to compensate for error due to common mode pressure comprises the second diaphragm portion having a selected area larger than the first diaphragm portion.