Organic chemical sensor

• US 5,482,678 A
• Filed: 11/10/1994
• Issued: 01/09/1996
• Est. Priority Date: 05/25/1993
• Status: Expired due to Term

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Sittler, Fred C.
• Primary Examiner(s): Housel, James C.
• Assistant Examiner(s): Soderquist, Arlen
• Application Number:
  US08/337,135
• Time in Patent Office: 425 Days
• Field of Search: 73/24.06, 73/31.05, 73/31.06, 73/775-776, 73/778, 73/579, 338/2-5, 338/34-35, 422/68.1, 422/82.01, 422/82.02, 422/83, 422/90, 422/94, 422/98, 436/72, 436/139, 436/149, 436/151
• US Class Current: 422/90
• CPC Class Codes: G01B 7/16 for measuring the deformation in a solid, e.g. by resistance strain gauge
• CPC Class Codes: G01M 3/045 with electrical detection means
• CPC Class Codes: G01N 19/10 Measuring moisture content, e.g. by measuring change in length of hygroscopic filament; Hygrometers
• CPC Class Codes: Y10T 436/21 Hydrocarbon

Abstract

In this invention, a first sensor senses an organic gas, liquid or vapor and includes a first support having a first support surface with a layer of material fastened to it. In the presence of liquid, gas or vapor, the material swells and expands so as to vary at least one of its dimensions. Such expansion develops a stress at an interface between the first support surface and the material, and strain sensitive resistors detect the stress and produce an output which varies as a function of the stress at the interface. One of a pair of piezoresistors is located where there is increased stress and the other piezoresistor is disposed where there is reduced stress. If desired, a second sensor similar in structure to the first but exposed only to a reference organic liquid, gas or vapor temperature compensates the first. In another embodiment of the invention, an organic chemical responsive sensor includes a first support having a first support surface and a first capacitor plate fastened to the first support. A second support coupled to the first support spaces a second capacitor plate a distance away from the first plate. A material which expands in the presence of organic liquid, gas or vapor is applied to the first support surface so that upon expansion, the first support deflects and changes the distance between the two capacitor plates, thereby changing an electrical capacity between the plates. Another sensor of similar structure may optionally temperature compensate the first.

Claims

1. An organic chemical sensor for sensing at least one of an organic gas, liquid and vapor, comprising:

a container having a deflectable portion;

an electrically non-conductive material disposed in the container, the material exposed to at least one of the organic gas, liquid and vapor and formed of a substance varying a first of its dimensions in the presence of at least one of the organic gas, liquid and vapor so as to deflect the deflectable portion; and

a sensor operably coupled at the deflectable portion for detecting deflection and having an output varying as a function of the deflection.

2. The organic chemical sensor of claim 1 wherein the electrically nonconductive material varies a first of its dimensions in the presence of the at least one of the organic gas, liquid and vapor selected from the group consisting of hydrocarbons, chlorohydrocarbons, fluorocarbons and silicarbons.

3. The organic chemical sensor of claim 1 wherein the material is formed of a substance reversibly varying a first of its dimensions in the presence of at least one of the organic gas, liquid and vapor.

4. The organic chemical sensor of claim 1 wherein the container includes a hole allowing at least one of the organic gas, liquid and vapor to contact the material.

5. The organic chemical sensor of claim 4 wherein the container includes a plurality of holes allowing at least one of the organic gas, liquid and vapor to contact the material.

6. The organic chemical sensor of claim 1 wherein the sensor comprises a first capacitor electrode disposed on the deflectable portion and a second capacitor electrode spaced apart from the first capacitor electrode.

7. The organic chemical sensor of claim 1 wherein the material varies only in the first of its dimensions.