PRESSURE-SENSING CAPACITOR

• US 3,858,097 A
• Filed: 12/26/1973
• Issued: 12/31/1974
• Est. Priority Date: 12/26/1973
• Status: Expired due to Term

• Current Assignee: William Ronald Polye
• Original Assignee: William Ronald Polye
• Inventors: Polye, William Ronald
• Primary Examiner(s): Goldberg, E. A.
• Application Number:
  US05/428,476
• Time in Patent Office: 370 Days
• Field of Search: 317/246,247,248 73/398C
• US Class Current: 361/283.1
• CPC Class Codes: G01L 9/0086 using variations in capacitance
• CPC Class Codes: G01L 9/125 with temperature compensating means non electric temperature compensating means G01L19/04
• CPC Class Codes: H01G 4/04 Liquid dielectrics

Abstract

A capacitance type pressure transducer which avoids errors due to changes in temperature has a pressure responsive capacitor and a fixed reference capacitor connected in a circuit to provide an output proportional to the ratio of the capacitances as a function of pressure. Since both capacitors are subjected to the same temperature changes any variations in capacitance due to temperature is cancelled out in the ratio.

Claims

1. A pressure transducer of the capacitance type comprising a hollow body having spaced opposing walls of insulating material supported at their edges, the portions of the walls spaced from the edges being deflectable relative to one another in response to changes in pressure and the portions of the walls adjacent the edges being substantially nondeflectable relative to one another with changes in pressure, electrical conducting means on opposing surfaces of the deflectable portions of said walls forming the plates of a pressure sensitive capacitor, and electrical conducting means on opposing surfaces of the substantially nondeflectable portions of said walls forming the plates of a reference capacitor.

2. A pressure transducer as described in claim 1 adapted for use in an environment which changes temperature over a substantially wide range, the capacitors being formed and arranged to change capacitance corresponding amounts due to changes in temperature.

3. A pressure transducer as described in claim 1 having means for connecting the capacitor plates in a circuit to provide an output proportional to the ratio of the capacitors.

4. A pressure transducer as described in claim 1 in which the hollow body is made of quartz.

5. A pressure transducer of the kind described in claim 1 in which the body is circular and the spaced opposing walls are supported circumferentially at their edges.

6. A pressure transducer as described in claim 1 in which the capacitances of the pressure sensitive capacitor and the reference capacitor are equal.

7. A pressure transducer of the capacitance type comprising a hollow circular body having spaced opposing walls supported circumferentially at their edges, the portions of the walls spaced from the edges being deflectable relative to one another in response to changes in pressure and the portions of the walls adjacent the edges beIng substantially nondeflectable relative to one another with changes in pressure, circular electrical conducting means positioned centrally on the deflectable portions of said walls forming the plates of a pressure sensitive capacitor, and annular electrical conducting means positioned adjacent the edges on the substantially non deflectable portions of said walls forming the plates of a reference capacitor.