Gas sensor

Abstract

A gas sensor assembly is provided with a non-conductive housing portion and a plurality of conductive housing portions, each of which are conductively separated from each other, and the conductive housing portions are composed of a conductive plastic material. A gas-sensing agent is disposed in a receptacle formed in the housing, and a plurality of electrodes are disposed in conductive contact with the gas-sensing agent. The gas sensor has an electrode support sheet with a plurality of electrodes formed thereon, and a seal is formed between the electrode support sheet and the housing, the seal being formed by the sealing of a portion of one of the electrodes to a portion of the housing.

What is claimed is:  
     
         1 . A gas sensor assembly comprising: 
 a housing having a receptacle formed therein, said housing having a non-conductive housing portion and a plurality of conductive housing portions, each of said conductive housing portions being conductively separated from each other, said conductive housing portions being composed of a conductive plastic material;    a gas-sensing agent disposed in said receptacle;    a plurality of electrodes disposed in conductive contact with said gas-sensing agent;    a conductive agent disposed on an area on a first of said conductive housing portions;    a conductive agent disposed on an area on a second of said conductive housing portions;    a first conductor disposed in conductive contact with said conductive agent on said area on said first conductive housing portion; and    a second conductor disposed in conductive contact with said conductive agent on said area on said second conductive housing portion.    
     
     
         2 . A gas sensor assembly as defined in  claim 1 , 
 wherein said area on said first conductive housing portion has a first surface area,    wherein said area on said second conductive housing portion has a second surface area,    wherein said first conductor makes contact with said area on said first conductive housing at a first contact area having a surface area of less than about one-half of said first surface area, and    wherein said second conductor makes contact with said area on said second conductive housing at a second contact area having a surface area of less than about one-half of said second surface area.    
     
     
         3 . A gas sensor assembly as defined in  claim 1 , 
 wherein said area on said first conductive housing portion has a first surface area,    wherein said area on said second conductive housing portion has a second surface area,    wherein said first conductor makes contact with said area on said first conductive housing at a first contact area having a surface area that is not equal to said first surface area, and    wherein said second conductor makes contact with said area on said second conductive housing at a second contact area having a surface area that is not equal to said second surface area.    
     
     
         4 . A gas sensor assembly as defined in  claim 1  wherein said conductive agent disposed on said areas on said conductive housing portions comprises a sprayed-on conductive ink coating.  
     
     
         5 . A gas sensor assembly as defined in  claim 1  wherein said conductive agent disposed on said areas on said conductive housing portions comprises a mixture of conductive ink and an adhesive.  
     
     
         6 . A gas sensor assembly as defined in  claim 1  wherein said conductive agent disposed on said areas on said conductive housing portions comprises a mixture of conductive ink, an adhesive, and a thinner.  
     
     
         7 . A gas sensor assembly as defined in  claim 1  wherein said conductive agent disposed on said areas on said conductive housing portions comprises a mixture of about 15% to about 25% by volume of a conductive ink, about 15% to about 25% by volume of an adhesive, and about 50% to about 70% by volume of a thinner.  
     
     
         8 . A gas sensor assembly as defined in  claim 1  additionally comprising a printed circuit board and wherein said first and second conductors are disposed on said printed circuit board.  
     
     
         9 . A method of forming a gas sensor assembly having a housing with a non-conductive housing portion and a plurality of conductive housing portions composed of conductive plastic material, said method comprising the steps of: 
 (a) forming said housing to have said non-conductive housing portion and said conductive housing portions;    (b) applying a conductive agent to an area on a first of said conductive housing portions and to an area on a second of said conductive housing portions;    (c) placing a contact surface of said first conductor in conductive contact with said conductive agent on said area on said first conductive housing portion, said first conductor making contact with said first conductive housing portion at a first contact area; and    (d) placing a contact surface of said second conductor in conductive contact with said conductive agent on said area on said second conductive housing portion, said second conductor making contact with said second conductive housing portion at a second contact area.    
     
     
         10 . A method as defined in  claim 9  wherein said step (b) comprises the step of applying a conductive agent comprising a mixture of a conductive ink and an adhesive to an area on a first of said conductive housing portions and to an area on a second of said conductive housing portions.  
     
     
         11 . A method as defined in  claim 9  wherein said step (b) comprises the steps of: 
 (b1) applying said conductive agent to an area on said first conductive housing portion having a surface area of at least about twice the surface area of said first contact area; and  
 (b2) applying said conductive agent to an area on said second conductive housing portion having a surface area of at least about twice the surface area of said second contact area.  
 
     
     
         12 . A method as defined in  claim 9  wherein said step (b) comprises the step of spraying said conductive agent on said areas on said first and second conductive housing portions.  
     
     
         13 . A gas sensor assembly comprising: 
 a housing having a receptacle formed therein, said housing having a non-conductive housing portion and a plurality of conductive housing portions, each of said conductive housing portions being conductively separated from each other, said conductive housing portions being composed of a conductive plastic material;    a gas-sensing agent disposed in said receptacle;    a plurality of electrodes disposed in conductive contact with said gas-sensing agent;    an electrode support sheet having a plurality of electrodes formed thereon; and    a seal formed between said electrode support sheet and said housing, said seal being formed by the sealing of a portion of one of said electrodes to one of said conductive housing portions so that a substantially liquid-tight seal is accomplished and so that said portion of said one electrode is conductively coupled to said one conductive housing portion.    
     
     
         14 . A gas sensor assembly as defined in  claim 13  wherein said electrode support sheet comprises PTFE and wherein said electrodes comprise a conductive metal.  
     
     
         15 . A gas sensor assembly comprising: 
 a housing having a receptacle formed therein, said housing having a non-conductive housing portion and a plurality of conductive housing portions, each of said conductive housing portions being conductively separated from each other, said conductive housing portions being composed of a conductive plastic material;    a gas-sensing agent disposed in said receptacle;    a plurality of electrodes disposed in conductive contact with said gas-sensing agent;    an electrode support sheet having a plurality of electrodes formed thereon;    a seal formed between said electrode support sheet and said housing, said seal being formed by the sealing of one of said conductive housing portions to said electrode support sheet.    
     
     
         16 . A gas sensor assembly as defined in  claim 15  wherein said seal provides a conductive connection between said electrode support sheet and said one conductive housing portion.  
     
     
         17 . A gas sensor assembly as defined in  claim 16  wherein said seal provides a conductive connection between said electrode support sheet and said one conductive housing portion and wherein said seal provides a substantially liquid-tight connection between said electrode support sheet and said one conductive housing portion.  
     
     
         18 . A method of forming an electrode sheet for a gas sensor assembly, said method comprising the steps of: 
 (a) forming a support sheet having a first side and a second side;    (b) applying a liquid electrode solution to a plurality of different areas on said first side of said support sheet; and    (c) after said step (b), subjecting said second side of said support sheet to a reduced pressure in order to pull said liquid electrode solution disposed on said first side of said support sheet towards said second side of said support sheet.    
     
     
         19 . A method as defined in  claim 18  additionally comprising the step of (d) forming a mask having a plurality of openings corresponding to said areas on said first side of said support sheet, said mask being formed prior to said step (b), and wherein said step (c) comprises the step of applying said liquid electrode solution to said areas on said first side of said support sheet through said openings in said mask.  
     
     
         20 . A method as defined in  claim 18  wherein said step (a) comprises the step of forming said support sheet from PTFE.  
     
     
         21 . A method as defined in  claim 18  wherein said step (b) comprises the step of applying a liquid electrode solution containing platinum to said areas on said first side of said support sheet.  
     
     
         22 . A gas sensor assembly comprising: 
 a housing having a receptacle formed therein;    a gas-sensing agent disposed in said receptacle;    a wick disposed within said receptacle formed in said housing, said wick being impregnated with said gas-sensing agent and having a surface; and    a plurality of conductive patterns formed on said surface of said wick, each of said conductive patterns extending from an interior portion of said wick to a peripheral portion of said wick.    
     
     
         23 . A gas sensor assembly as recited in  claim 22  wherein said wick comprises a substantially flat member having a substantially circular shape.  
     
     
         24 . A gas sensor assembly as recited in  claim 22  wherein said conductive patterns formed on said surface of said wick comprise platinum.  
     
     
         25 . A gas sensor assembly as recited in  claim 22  wherein said conductive patterns formed on said surface of said wick comprise platinum vacuum-deposited on said wick.  
     
     
         26 . A gas sensor assembly as recited in  claim 22  wherein said housing comprises a non-conductive housing portion and a plurality of conductive housing portions, each of said conductive housing portions being conductively separated from each other, said conductive housing portions being composed of a conductive plastic material, and wherein each of said conductive patterns formed on said surface of said wick is conductively coupled to a respective one of said conductive housing portions.  
     
     
         27 . A method of forming a gas sensor assembly, said method comprising the steps of: 
 (a) forming a wick composed of a gas sensing agent-adsorbent material having a first side and a second side;    (b) applying a liquid electrode solution to a plurality of different areas on said first side of said wick;    (c) after said step (b), subjecting said second side of said wick to a reduced pressure in order to pull said liquid electrode solution disposed on said first side of said wick towards said second side of said wick; and    (d) incorporating said wick in a gas sensor so that said wick is in contact with a gas-sensing agent disposed in said gas sensor.    
     
     
         28 . A method as defined in  claim 27  additionally comprising the step of (e) forming a mask having a plurality of openings corresponding to said areas on said first side of said wick, said mask being formed prior to said step (b), and wherein said step (c) comprises the step of applying said liquid electrode solution to said areas on said first side of said wick through said openings in said mask.  
     
     
         29 . A gas sensor assembly comprising: 
 a housing having a receptacle formed therein;    a gas-sensing agent disposed in said receptacle;    a plurality of electrodes;    a wick disposed within said receptacle formed in said housing, said wick having an elongate portion and a flat portion in contact with said elongate portion, said wick causing said gas-sensing agent to be disposed in contact with said electrodes; and    a wick support disposed within said receptacle formed in said housing, said wick support having a first portion which supports said flat portion of said wick and a second portion which supports said elongate portion of said wick.    
     
     
         30 . A gas sensor assembly as recited in  claim 29  wherein said first portion of said wick support is generally flat and wherein said second portion of said wick support comprises a hollow tube in which said elongate portion of said wick is disposed.  
     
     
         31 . A gas sensor assembly as recited in  claim 29  wherein said first portion of said wick support has a plurality of holes formed therein to allow said flat portion of said wick to come into direct contact with said gas-sensing agent disposed in said receptacle formed in said housing when said gas sensor assembly is turned over.  
     
     
         32 . A gas sensor assembly as recited in  claim 29  wherein said second portion of said wick support has an elongate slot formed therein to allow said elongate portion of said wick to come into fluid contact with said gas-sensing agent disposed in said receptacle formed in said housing.  
     
     
         33 . A gas sensor assembly as recited in  claim 29  wherein said elongate portion of said wick has a diameter of no greater than about one-eighth of an inch.  
     
     
         34 . A gas sensor assembly as recited in  claim 29  wherein said housing comprises a non-conductive housing portion and a plurality of conductive housing portions, each of said conductive housing portions being conductively separated from each other, said conductive housing portions being composed of a conductive plastic material.