CAPACITANCE-TYPE PRESSURE TRANSDUCER

• US 3,634,727 A
• Filed: 12/03/1968
• Issued: 01/11/1972
• Est. Priority Date: 12/03/1968
• Status: Expired due to Term

• Current Assignee: William Ronald R. Polye
• Original Assignee: William Ronald R. Polye
• Inventors: Polye, William Ronald R.
• Primary Examiner(s): Kallam, James D.
• Application Number:
  US04/780,666
• Time in Patent Office: 1,134 Days
• Field of Search: 317/234,235,231
• US Class Current: 361/434
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass
• CPC Class Codes: G01L 9/0086 using variations in capacitance

Abstract

A pressure sensor of the capacitance-type comprising a hollow capsule formed of a pair of discs of single crystal silicon doped to make it electrically conductive and having a layer of silicon dioxide on the surfaces of the discs with portions of the silicon dioxide layer and discs being cut away on opposing faces of the discs to form a cavity therebetween. The discs are insulated from one another and form the plates of a condenser which changes capacity when the sensor is subjected to pressure changes.

Claims

1. A pressure sensor comprising a hollow capsule having spaced opposing walls formed of single crystal silicon insulated from one another, said walls being movable relative to one another in response to changes in pressure for changing the capacitance therebetween.

2. A pressure sensor as described in claim 1 in which opposing faces of the walls are recessed to form a cavity therebetween.

3. A pressure sensor as described in claim 1 which is of the capacitance type and the walls form the plates of a capacitor.

4. A pressure sensor as described in claim 3 having means for connecting the capacitor plates electrically in a circuit.

5. A pressure sensor as described in claim 3 in which the silicon is doped to make it conductive.

6. A pressure sensor as described in claim 5 in which the walls are insulated from one another by a layer of silicon dioxide.

7. A pressure sensor as described in claim 5 in which the walls are insulated from one another by converting mating surfaces of the silicon to a conductivity-type opposite from that of the silicon.

8. A pressure sensor comprising a pair of discs formed of single crystal silicon doped to make it conductive, means for joining the discs together at their peripheries so that the discs are insulated from one another and form a cavity therebetween, and the discs forming the plates of a condenser which changes capacity upon being subjected to changes in pressure.

9. A pressure sensor as described in claim 8 in which a layer of silicon dioxide is provided on mating surfaces of the discs to insulate the discs from one another.

10. A pressure sensor as described in claim 8 in which the silicon is converted to opposite conductivity-type at a mating surface of at least one of the discs to insulate the discs from one another.

11. A pressure sensor as described in claim 8 having means for connecting the condenser plates in a circuit.

12. A pressure sensor as described in claim 8 in which the discs have recessed portions which form the cavity.