Pressure transducer with capacitor pick-up means

• US 4,084,439 A
• Filed: 01/03/1977
• Issued: 04/18/1978
• Est. Priority Date: 10/01/1975
• Status: Expired due to Term

• Current Assignee: King Radio Corp. (Honeywell International Inc.)
• Original Assignee: King Radio Corp. (Honeywell International Inc.)
• Inventors: Rothers, Paul L., Maddock, James W., Teter, Robert D.
• Primary Examiner(s): Woodiel, Donald O.
• Application Number:
  US05/756,075
• Time in Patent Office: 470 Days
• Field of Search: 73/398 C, 73/398 R, 73/32 R, 73/406
• US Class Current: 73/718
• CPC Class Codes: G01L 9/0008 using vibrations

Abstract

A pressure transducer includes an electromagnetic drive coil which vibrates a thin walled cylinder at a natural vibrational mode. A capacitor unit senses the vibrational frequency of the cylinder and gives an output signal corresponding to the pressure differential between a fluid contained within the cylinder and a vacuum reference that is maintained adjacent to the exterior surface of the cylinder. Electric heaters maintain a constant operating temperature of the transducer.

Claims

1. A method of producing an electric signal indicative of the pressure differential between a fluid and a reference pressure, said method comprising the steps of:

providing a vibrational membrane;

maintaining said reference pressure on one side of said membrane;

bringing said fluid into contact with the other side of said membrane;

effecting vibration of said membrane in the fifth order vibrational mode thereof;

locating five capacitor plates at spaced positions in proximity to said membrane to cooperate therewith in providing a capacitor to sense the vibrations of said membrane; and

producing an oscillatory output signal from said capacitor corresponding in frequency to the vibrational frequency of said membrane, said output signal thereby being related to the pressure differential between said fluid and said reference pressure.

2. A pressure transducer for producing an electric signal indicative of the pressure differential between a fluid and a reference pressure, said pressure transducer comprising:

a support member;

a vibratory hollow member mounted on said support member and comprised of magnetic material, said hollow member having a first chamber defined therewithin;

a casing enclosing said hollow member and spaced outwardly thereof to present a second chamber between said hollow member and casing, said first and second chambers being isolated from one another, one of said first and second chambers being maintained at said reference pressure and the other of said chambers having an inlet for receiving said fluid;

an electric heater mounted on said support member within said hollow member, said heater being operable to emit heat;

means for effecting vibration of said hollow member in a natural vibrational mode thereof; and

capacitor means cooperating with said hollow member to sense the vibrations thereof, said capacitor means having an oscillatory electric output signal corresponding to the vibrational frequency of said hollow member and thus to the pressure differential between said fluid and said reference pressure.