Multiple range capacitive pressure transducer

• US 4,445,383 A
• Filed: 06/18/1982
• Issued: 05/01/1984
• Est. Priority Date: 06/18/1982
• Status: Expired due to Term

• Current Assignee: Stock Equipment Co. Inc. (Schenck Process Holding GmbH)
• Original Assignee: General Signal Corporation (SPX Corporation)
• Inventors: Binder, Paul B., Di Napoli, Louis D.
• Primary Examiner(s): Goldberg, Gerald
• Assistant Examiner(s): Chapman, Jr., John E.
• Application Number:
  US06/389,657
• Time in Patent Office: 683 Days
• Field of Search: 73/718, 361/283
• US Class Current: 73/718
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm

Abstract

There is provided a multirange, variable capacitance pressure transducer by bonding a diaphragm plate that is conductive between a pair of insulating plates with the diaphragm plate having a plurality of cavities provided on each side so that diaphragm deflection areas of different sizes are defined. The surfaces of the pair of plates in the cavities are covered by a conductive coating so that the coatings form capacitors with the deflection areas. A fluid communication path is provided to each cavity so that the pressure difference to be measured is placed across the deflection area. Electrical connection is made to selective combinations of said capacitors to provide pressure transducers for a number of ranges in one unit.

Claims

1. A multi-range, variable capacitance pressure transducer, comprising:

a pair of plates of non-conductive material;

a diaphragm plate bonded between the plates of said pair, said diaphragm plate having a plurality of conductive deflecting areas of different diameters defined by cavities on opposite sides of said diaphragm plate;

conducting areas deposited on the plates of said pair opposite the deflecting areas to form capacitors therewith;

means providing fluid communication to the cavities so that opposing sides of the deflecting areas are exposed to fluid pressures to be measured; and

means providing electrical connection to the conducting areas and said conductive deflecting areas of said diaphragm plate so that selected combinations of the capacitors formed between said conducting areas and associated conductive deflecting areas are connected to provide the same capacitance and capacitance change for pressure difference measurements of said fluid over different ranges.

2. Apparatus as set forth in claim 1 in which said pair of plates is constructed of borosilicate glass and said diaphragm plate is of silicon.

3. Apparatus as set forth in claims 1 or 2 in which the cavities are the result of the etching of the recesses forming said cavities in the diaphragm plate.

4. Apparatus as set forth in claims 1 or 2 in which said means providing fluid communication includes a manifold providing a common reference pressure to all cavities on one side of said diaphragm plate.

5. A multi-range, variable capacitance pressure transducer, comprising:

a pair of plates of inorganic electrically insulating material with a plurality of circular electrically conducting surfaces of differing sizes deposited over spaced areas on one surface of each of said plates;

a diaphragm plate of electrically conductive semiconductor material electrostatically bonded between said pair of plates, said semiconductor material having a plurality of circular recesses of differing sizes in both of its faces in opposing relationship and in registration with said conducting surfaces so as to form with the conducting surfaces of said pair of plates a plurality of capacitors in fluid-tight cavities on opposite sides of diaphragm deflecting areas defined by said recesses;

means providing fluid communication to the cavities so that the opposite sides of their respective diaphragm deflecting areas are exposed to the pressures to be measured; and

means providing for electrical connection to the conducting surfaces on each of said pair of plates and said diaphragm plate so that selected combinations of said capacitors can be connected together to provide for pressure measurement over different ranges of pressure difference.

6. A transducer as set forth in claim 5 in which said means providing fluid communication to the cavities includes:

aperatures through each of said pair of plates connecting to the cavities of said transducer, and

a manifold for interconnecting the apertures leading to the cavities on one side of said diaphragm plate.

7. A multi-range, variable capacitance pressure transducer, comprising:

a first plate;

a second plate bonded to the first plate, said second plate having a plurality of diaphragm deflecting areas of different diameters defined by cavities between said first and second plates;

opposing electrically conductive areas located on the first plate and the diaphragm deflecting areas of the second plate to form capacitors therebetween;

means providing fluid communication to the cavities so that the opposite sides of the diaphragm deflecting areas are exposed to a fluid pressure difference to be measured; and

means providing electrical connection to the conducting areas so that selected combinations of the capacitors formed by said conducting areas can be connected to provide the same capacitance and capacitance change for pressure difference measurements of said fluid over different ranges.

8. A multi-range, variable capacitance pressure transducer, comprising:

a pair of plates with a plurality of circular electrically conducting surfaces of differing sizes located over spaced areas on one surface of each of said plates;

a diaphragm plate of electrically conductive semiconductor material bonded between said pair of plates, said semiconductor material having a plurality of circular recesses of differing sizes in both of its faces in opposing relationship and in registration with said conducting surfaces so as to form with the conducting surfaces of said pair of plates a plurality of capacitors in fluid-tight cavities on opposite sides of diaphragm deflecting areas defined by said recesses;

means providing fluid communication to the cavities so that the opposite sides of their respective diaphragm deflecting areas are exposed to the pressures to be measured; and

means providing for electrical connection to the conducting surfaces on each of said pair of plates and said diaphragm plate so that selected combinations of said capacitors can be connected to provide for pressure measurement over different ranges of pressure difference.