Polarographic sensor
First Claim
1. A polarographic, electrochemical cell instrument for determining the concentration of a selected gas in a mixture of gases;
- a polarographic cell having a thin electrolyte film disposed between a first cathode electrode formed of a noble metal capable of polarographically reducing oxygen and a gas permeable membrane and having a second, non-polarizable metal, anode electrode in electrical connection with the electrolyte, the combination therewith;
biasing means for applying a low controlled voltage bias at first polarity between said first and second electrodes at a polarographic reducing potential of the selected gas and below the reducing potential of other gases in the mixture;
manual, one-way turn-on switching means connected to the biasing means through activation means; and
activation means for automatically, at turn-on, applying a voltage pulse of second polarity to the first electrode and including electronic timing and cut-off means for terminating said pulse after about ten seconds from turn-on.
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Accused Products
Abstract
An apparatus and method for polarographically determining the amount of oxygen in a gaseous mixture containing interfering reducible gases such as nitrous oxide is disclosed. The invention has particular application to the determination of oxygen in nitrous oxide containing anesthetic gas mixtures. The oxygen content is determined by operating a special polarographic cell at about -0.6 volts, which is below the voltage at which nitrous oxide would be sensed polarographically. A special cathode is utilized in which the exposed cathode face is disposed near the periphery of a cathode support mounted centrally under the gas permeable membrane so that ion mobility is increased to decrease the internal resistance of the electrochemical cell. It is also found that at the low operating voltage the cathode tends to become passivated or inactive after use. In accordance with the invention the cathode is activated at turn-on by reversing polarity and applying a positive voltage pulse to the cell.
46 Citations
10 Claims
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1. A polarographic, electrochemical cell instrument for determining the concentration of a selected gas in a mixture of gases;
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a polarographic cell having a thin electrolyte film disposed between a first cathode electrode formed of a noble metal capable of polarographically reducing oxygen and a gas permeable membrane and having a second, non-polarizable metal, anode electrode in electrical connection with the electrolyte, the combination therewith; biasing means for applying a low controlled voltage bias at first polarity between said first and second electrodes at a polarographic reducing potential of the selected gas and below the reducing potential of other gases in the mixture; manual, one-way turn-on switching means connected to the biasing means through activation means; and activation means for automatically, at turn-on, applying a voltage pulse of second polarity to the first electrode and including electronic timing and cut-off means for terminating said pulse after about ten seconds from turn-on. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification