PRESSURE TRANSDUCER

• US 3,750,476 A
• Filed: 09/25/1967
• Issued: 08/07/1973
• Est. Priority Date: 09/25/1967
• Status: Expired due to Term

• Current Assignee: Neil L. Brown
• Original Assignee: Neil L. Brown
• Inventors: Brown, Neil L.
• Primary Examiner(s): Swisher, S. Clement
• Application Number:
  US04/670,210
• Time in Patent Office: 2,143 Days
• Field of Search: 73/398C 317/246
• US Class Current: 73/724
• CPC Class Codes: G01L 9/0005 using variations in capacitance G01L9/0072 takes precedence
• CPC Class Codes: G01L 9/12 by making use of variations in capacitance , i.e. electric circuits therefor

Abstract

This invention relates to a pressure transducer which is able to operate in all types of environments, including normally adverse environments, to provide an accurate indication of pressure. The pressure transducer is able to provide accurate indications of relatively high pressures in one embodiment and of relatively low pressures in a second embodiment. The pressure transducer provides such accurate indications by varying the distance between two plates of a capacitor in accordance with the variations in the pressure to be measured. The pressure transducer is made by novel methods also included within this invention.

Claims

1. In combination for use in a pressure transducer, a hollow tube made from a chemically inert, electrically insulating material having substantially linear stress-strain characteristics and capable of withstanding relatively low and high temperatures and having a relatively low temperature coefficient of expansion and capable of withstanding considerable pressure, the hollow tube having a pair of opposite ends to define a closure;

a rod made from a chemically inert, electrically insulating material having substantially linear stress-strain characteristics and capable of withstanding relatively low and high temperatures and having a relatively low temperature coefficient of expansion and capable of withstanding considerable pressures, the rod having a pair of opposite ends and a curved external surface between the opposite ends, the curved external surfaces on the rod corresponding to the curved internal surface in the tube;

the rod being disposed within the tube and being sealed to the tube at the opposite ends, the rod being snugly disposed against the tubes within the opposite ends and being tapered slightly at an intermediate position between the opposite ends relative to the tube to have a slight spacing from the tube;

the external surface of the rod and the internal surface of the tube being coated with an electrically conductive material at the intermediate positions between the opposite ends to define first and second plates of a capacitor;

there being a substantially uniform dielectric in the spacing between the tube and the rod; and

means for providing for an indication of variations in the value of the capacitor in accordance with variations in the spacing between the first and second plates.

2. The combination set forth in claim 1 wherein the rod and the tube are made from quartz and are substantially cylindrical.

3. The combination set forth in claim 1 wherein the hollow tube has an external surface which is coated with a conductive material to provide external shielding for the capacitor defined by the hollow tube and the rod.

4. In combination for measuring variations in pressure, a first quartz member having a first surface;

a second quartz member having a second surface;

first electrically conductive material on the first surface of the first quartz member;

second electrically conductive material on the second surface of the second quartz member;

the first and second quartz members being sealed to each other with the first and second surfaces having a particular spacing relative to each other to define plates of a capacitor;

one of the first and second quartz members being movable relative to the other quartz member in response to variations in pressure to produce a variable value for the capacitor in accordance with such variable pressure;

first and second electrical leads respectively connected to the first and second electrically conductive material to provide output indications of the variable value of the capacitor;

an electrical shield enveloping the first and second quartz members; and

the opposite extremities of the first and second quartz members being fused to produce the seal between the members.

5. In combination for measuring variations in pressure, a first quartz member having a particular configuration and defined by at least One extremity and having a first surface in the particular configuration;

a second quartz member having the particular configuration and defined by at least one extremity and having a second surface in the particular configuration;

the extremities of the first and second quartz members being sealed to each other with the first surface on the first quartz member and the second surface on the second quartz member in contiguous relationship;

a first thin electrically conductive coating uniformly disposed on the first surface of the first quartz member;

a second thin electrically conductive coating uniformly disposed on the second surface of the second quartz member;

a first electrical lead extending from the first thin electrically conductive coating;

a second electrical lead extending from the second thin electrically conductive coating;

an electrical shield being provided for the first and second quartz members; and

the opposite extremities of the first and second quartz members being fused to provide the seal.

6. In combination for use in a pressure transducer:

a first member made from a chemically inert, electrically insulating material having substantially linear stress-strain characteristics and capable of withstanding relatively low and high temperatures and having a relatively low temperature coefficient of expansion and capable of withstanding considerable pressures, the first member having a particular configuration and at least one extremity and having a first surface;

a second member made from a chemically inert, electrically insulating material having substantially linear stress-strain characteristics and capable of withstanding relatively low and high temperatures and having a relatively low temperature coefficient of expansion and capable of withstanding considerable pressures, the second member having the particular configuration and at least one extremity and having a second surface;

the first and second members being sealed to each other at their extremities with the first and second surfaces being disposed in contiguous and substantially uniformly spaced relationship;

the first and second surfaces being coated with an electrically conductive material to define opposite plates of a capacitor having a value dependent upon the spacing between the first and second surfaces;

first and second leads respectively connected to and extending from the electrical coatings on the first and second surfaces;

an electrical shield enveloping the first and second members; and

the extremities of the first and second members being fused to define the shields.