US4500391A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of and system for real time differential pulse detection
Assignee: ENVIROMENTAL TECHNOLOGIES GROUP Inc
•
Filing: 1983-10-13
•
Granted: 1985-02-19
•
Expires: 2003-10-13
Abstract
Abstract An electrochemical detection cell which includes, in the order named, a stack of components constituted by a first membrane, an electrode carrier having reference and counter electrodes thereon, a membrane support, an electrode carrier having a sensing electrode thereon, and a permselective membrane. Whatman filter papers are positioned between the sensing electrode and both the counter electrode and reference electrode, these being positionable in a central rectangular opening of the membrane support. The cell allows air or gas ambient to address the membranes and effects application of an electrolyte to space between the electrodes by, for example, a wick which extends between an electrolyte-containing reservoir and the Whatman filter papers. A system for detecting a gaseous agent uses the aforementioned detection cell coupled with circuitry capable of applying a fixed DC voltage bias to the reference electrode and superimposing a train of DC voltage pulses on the fixed bias. Further circuitry is coupled to and responsive to signals from the sensing electrode. This circuitry determines the difference between the sensing electrode signal at the end of each pulse minus that just before each pulse. The difference is proportional to the concentration of the test gas in the atmosphere adjacent to the sensor, and is a more specific and sensitive indication of the test gas concentration than prior art sensors.
Inventors
- 👤 John C. Schmidt
- 👤 Clifton A. Sands
- 👤 Donald N. Campbell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 13:03
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/26; G01N27/416; G01N27/48
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
211 words
A system for detecting a gas in an environment comprising an electrochemical detection cell having a reference electrode, a counter electrode and a sensing electrode; said reference electrode and said counter electrode spaced apart from each other and from said sensing electrode, an electrolyte in contact with said reference electrode, counter electrode and sensing electrode, a membrane having a first surface exposed to said environment for passing said gas in said environment through said membrane to said sensing electrode, an operational amplifier having an output terminal, an inverting input terminal and a non-inverting input terminal, said output terminal being coupled to said counter electrode, said reference electrode being coupled to one of said input terminals; means for applying a fixed D.C. voltage bias to the other of said input terminals; means for applying at least one differential D.C. voltage pulse to said other input terminal to superimpose same on said fixed D.C. voltage bias to provide a corresponding differential D.C. voltage pulse on its output terminal, and means coupled to said sensing electrode and responsive to current therefrom for determining difference in Faradaic currents produced during a period before application of the differential D.C. voltage pulse and a period before termination thereof as an indication of presence of a given gas.
Claim 2
Independent Claim
211 words
A system for detecting a gas in an environment comprising an electrochemical detection cell having a reference electrode, a counter electrode and a sensing electrode; said reference electrode and said counter electrode spaced apart from each other and from said sensing electrode, an electrolyte in contact with said reference electrode, counter electrode and sensing electrode, a membrane having a first surface exposed to said environment for passing said gas in said environment through said membrane to said sensing electrode, an operational amplifier having an output terminal, an inverting input terminal and a non-inverting input terminal, said output terminal being coupled to said counter electrode, said reference electrode being coupled to one of said input terminals; means for applying a fixed D.C. voltage bias to the other of said input terminals; means for applying at least one differential D.C. voltage pulse to said other input terminal to superimpose same on said fixed D.C. voltage bias to provide a corresponding differential D.C. voltage pulse on its output terminal, and means coupled to said sensing electrode and responsive to current therefrom for determining difference in Faradaic currents produced during a period before application of the differential D.C. voltage pulse and a period before termination thereof as an indication of presence of a given gas.
Claim 3
Dependent Claim
48 words
A system according to claim 1, wherein said reference electrode is coupled to said inverting input terminal of said operational amplifier, and said means for applying a fixed D.C. voltage bias and said means for applying a differential D.C. voltage pulse are coupled to said non-inverting input terminal.
Claim 4
Dependent Claim
17 words
A system according to claim 2, further including means for adjustably setting the fixed D.C. voltage bias.
Claim 5
Dependent Claim
18 words
A system according to claim 3, including means for adjustably setting amplitude of said differential D.C. voltage pulse.
Claim 6
Dependent Claim
20 words
A system according to claim 2, further including means for adjustably setting the amplitude of said differential D.C. voltage pulse.
Claim 7
Dependent Claim
70 words
A system according to claim 1, wherein said means coupled to said sensing electrode and responsive to current therefrom includes first storage means for storing a signal representative of current from said sensing electrode during a period before application of said differential D.C. voltage pulse and second storage means for storing a signal representative of current from said sensing electrode during a period before termination of said D.C. voltage pulse.
Claim 8
Dependent Claim
30 words
A system according to claim 6, wherein said first storage means and said second storage means comprise respective first capacitance means and second capacitance means, the signals being voltage signals.
Claim 9
Dependent Claim
31 words
A system according to claim 6, including means coupled to said first storage means and to said second storage means and responsive to the signals therefrom for determining the difference therebetween.
Claim 10
Dependent Claim
30 words
A system according to claim 8, wherein said first storage means and said second storage means comprise respective first capacitance means and second capacitance means, the signals being voltage signals.
Claim 11
Dependent Claim
29 words
A system according to claim 8, including alarm means, said alarm means being coupled to said means coupled to said first storage means and to said second storage means.
Claim 12
Dependent Claim
44 words
A system according to claim 10, including sample-and-hold circuit means for holding the highest signal representing the difference current, said sample-and-hold circuit means being coupled between said means coupled to said first storage means and to said second storage means, and said alarm means.
Claim 13
Dependent Claim
17 words
A system according to claim 10, wherein said alarm means comprises means for producing an audible signal.
Claim 14
Dependent Claim
17 words
A system according to claim 12, wherein said alarm means comprises means for producing a visual signal.
Claim 15
Dependent Claim
17 words
A system according to claim 10, wherein said alarm means comprises means for producing a visual signal.
Claim 16
Dependent Claim
35 words
A system according to claim 1, wherein said electrochemical detection cell comprises at least one further membrane positioned between said counter electrode and a gas-containing chamber and between said reference electrode and the gas-containing chamber.
Claim 17
Dependent Claim
19 words
A system according to claim 1, wherein said reference electrode, said counter electrode and said sensing electrode are meshes.
Claim 18
Dependent Claim
24 words
A system according to claim 1, wherein said sensing electrode is a mesh and said reference electrode and said counter electrode are composite electrodes.
Claim 19
Dependent Claim
21 words
A system according to claim 17, wherein said composite electrodes are of finely divided conductive powder and an inert plastic binder.
Claim 20
Independent Claim
183 words
A system for detecting a gas in an environment comprising an electrochemical detection cell having a reference electrode, a counter electrode and a sensing electrode, said reference electrode and said counter electrode spaced apart from each other and from said sensing electrode an electrolyte in contact with said reference electrode, counter electrode and sensing electrode, a membrane having a first surface exposed to said environment for passing said gas in said environment through said membrane to said sensing electrode, means for applying a fixed D.C. voltage bias to said counter electrode for supplying electrical current through said electrolyte to said sensing electrode to maintain a predetermined potential at said reference electrode, means for superimposing at least one differential D.C. voltage pulse on said fixed D.C. voltage bias, and means coupled to and responsive to Faradaic signals from said sensing electrode for determining the difference between Faradaic signals produced during a period before the at least one differential D.C. voltage pulse is superimposed on the fixed D.C. voltage bias and during a period before termination of the at least one differential D.C. voltage pulse.
Claim 21
Independent Claim
183 words
A system for detecting a gas in an environment comprising an electrochemical detection cell having a reference electrode, a counter electrode and a sensing electrode, said reference electrode and said counter electrode spaced apart from each other and from said sensing electrode an electrolyte in contact with said reference electrode, counter electrode and sensing electrode, a membrane having a first surface exposed to said environment for passing said gas in said environment through said membrane to said sensing electrode, means for applying a fixed D.C. voltage bias to said counter electrode for supplying electrical current through said electrolyte to said sensing electrode to maintain a predetermined potential at said reference electrode, means for superimposing at least one differential D.C. voltage pulse on said fixed D.C. voltage bias, and means coupled to and responsive to Faradaic signals from said sensing electrode for determining the difference between Faradaic signals produced during a period before the at least one differential D.C. voltage pulse is superimposed on the fixed D.C. voltage bias and during a period before termination of the at least one differential D.C. voltage pulse.
Claim 22
Dependent Claim
144 words
A system according to claim 19, wherein said means for superimposing at least one differential D.C. voltage pulse comprises means for superimposing a first train of differential D.C. voltage pulses on the fixed D.C. voltage bias, and said means responsive to signals from the sensing electrode includes: (1) means for producing a further train of pulses and an additional train of pulses both synchronized with the first train of pulses and having the same repetition rate and being timed to effect sampling of signals from the sensing electrode in periods before start and before termination of each differential D.C. pulse of the first train and (2) means responsive to the sampled signals for determining the difference between those produced during the periods before the respective differential D.C. voltage pulse and those produced during the periods before termination of the respective differential D.C. voltage pulses.
Claim 23
Dependent Claim
16 words
A system according to claim 20, including sample-and hold circuit means for storing the difference signal.
Claim 24
Dependent Claim
17 words
A system according to claim 20, including at least one alarm circuit responsive to the difference signal.
Claim 25
Independent Claim
166 words
A method for detecting a gaseous agent in an ambient with an electrochemical detection cell having a sensing electrode, a counter electrode and a reference electrode, said reference electrode and said counter electrode spaced apart from each other and from said sensing electrode and having an electrolyte in contact with said reference electrode, counter electrode and sensing electrode, comprising the steps of exposing said ambient to one side of a membrane capable of passing said gaseous agent, exposing said sensing electrode with the gas passing through said membrane, applying a fixed D.C. voltage bias to the counter electrode for supplying electrical current through said electrolyte to said sensing electrode to maintain a predetermined potential at said reference electrode, superimposing at least one differential D.C. voltage pulse on the fixed D.C. voltage bias and determining the difference between Faradaic signals produced from the sensing electrode during a period before superimposing the differential D.C. voltage pulse and in a period before termination of the differential D.C. voltage pulse.
Claim 26
Independent Claim
166 words
A method for detecting a gaseous agent in an ambient with an electrochemical detection cell having a sensing electrode, a counter electrode and a reference electrode, said reference electrode and said counter electrode spaced apart from each other and from said sensing electrode and having an electrolyte in contact with said reference electrode, counter electrode and sensing electrode, comprising the steps of exposing said ambient to one side of a membrane capable of passing said gaseous agent, exposing said sensing electrode with the gas passing through said membrane, applying a fixed D.C. voltage bias to the counter electrode for supplying electrical current through said electrolyte to said sensing electrode to maintain a predetermined potential at said reference electrode, superimposing at least one differential D.C. voltage pulse on the fixed D.C. voltage bias and determining the difference between Faradaic signals produced from the sensing electrode during a period before superimposing the differential D.C. voltage pulse and in a period before termination of the differential D.C. voltage pulse.
Claim 27
Dependent Claim
130 words
A method according to claim 23, wherein the step of superimposing at least one differential D.C. voltage pulse on the fixed D.C. voltage bias involves superimposing a first train of differential D.C. voltage pulses thereon, supplying a second train of pulses and a third train of pulses both synchronized with the first train of pulses and having the same repetition rate, and using respectively the second and the third train of pulses to affect sampling of signals from the sensing electrode in periods before start and before termination of each differential D.C. pulse of the first train, and determining the difference between the signals produced during the periods before the respective differential D.C. voltage pulses and those produced during the periods before termination of the respective differential D.C. voltage pulses.
References Cited (Backward Citations)
US4340885A
Cited
US4388822A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-02-19 | 1988-08-20 | 1989-02-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-02-19 | 1992-08-20 | 1993-02-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-02-19 | 1996-08-20 | 1997-02-19 | $7700.00 | Window Closed / Lapsed |