Electrochemical sensor
First Claim
1. A method for eliminating an influence of double-layer capacitance in an electrochemical measurement of a concentration of oxygen in blood, comprising the steps of:
- providing a working electrode, a reference electrode and a counter-electrode in contact with blood;
placing said working electrode in an electrically floating state so that said working electrode is at a floating potential relative to said reference electrode;
sampling and holding said floating potential of said working electrode;
subsequently placing said working electrode at a first potential relative to said reference electrode during a first predetermined measurement period t1 to t2, said first potential being sufficiently high to cause an electrochemical reaction at said working electrode;
subsequently placing said working electrode at a second potential relative to said reference electrode equal to the sampled and held floating potential during a second measurement period t2 to t3 immediately following and equal in length to said first measurement period;
identifying a first electrical charge Q1 produced during said first measurement period starting at a time ti after t1, with t1<
ti<
t2 and identifying a second electrical charge Q2 of opposite polarity to Q1 during said second measurement period at said time ti after t2, with t2<
ti<
t3;
forming a difference Δ
Q by adding Q1 and Q2, and using Δ
Q as a proportional indicator of an amount of oxygen in said blood.
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Accused Products
Abstract
In a method and apparatus for eliminating the influence of double-layer capacitance in electrochemical measurements of the concentration of oxygen in blood using a working electrode, a reference electrode and a counter-electrode in contact with blood, a first potential is applied to the working electrode during a first measurement period and a second potential is applied to the working electrode during a second measurement period, the second potential being equal to a floating potential of the working electrode measured while the working electrode is in an electrically floating state. Charge generated by an output current from the working electrode respectively in the first and second measurement periods is accumulated, and the accumulated charge is used as a proportional representation of the amount of oxygen in the blood.
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Citations
6 Claims
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1. A method for eliminating an influence of double-layer capacitance in an electrochemical measurement of a concentration of oxygen in blood, comprising the steps of:
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providing a working electrode, a reference electrode and a counter-electrode in contact with blood;
placing said working electrode in an electrically floating state so that said working electrode is at a floating potential relative to said reference electrode;
sampling and holding said floating potential of said working electrode;
subsequently placing said working electrode at a first potential relative to said reference electrode during a first predetermined measurement period t1 to t2, said first potential being sufficiently high to cause an electrochemical reaction at said working electrode;
subsequently placing said working electrode at a second potential relative to said reference electrode equal to the sampled and held floating potential during a second measurement period t2 to t3 immediately following and equal in length to said first measurement period;
identifying a first electrical charge Q1 produced during said first measurement period starting at a time ti after t1, with t1<
ti<
t2 and identifying a second electrical charge Q2 of opposite polarity to Q1 during said second measurement period at said time ti after t2, with t2<
ti<
t3;
forming a difference Δ
Q by adding Q1 and Q2, and using Δ
Q as a proportional indicator of an amount of oxygen in said blood.- View Dependent Claims (2, 3)
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4. An apparatus for eliminating an influence of double-layer capacitance in an electrochemical measurement of a concentration of oxygen and blood, comprising:
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a working electrode;
a reference electrode;
a counter-electrode, each of said working electrode, said reference electrode and said counter-electrode being in contact with blood;
means for measuring a floating potential at said working electrode, relative to said reference electrode, when said working electrode is in an electrically floating state, and for temporarily retaining said floating potential;
means for placing said working electrode at a first potential relative to said reference electrode during a first predetermined measurement period t1 to t2 and thereby causing an electrochemical reaction at said working electrode;
means for placing said working electrode at a second potential relative to said reference electrode, equal to said retained floating potential, during a second measurement period t2 to t3 immediately following and equal to said first measurement period;
means for identifying a first electrical charge Q1 producing during said first measurement period starting at a time ti after t1, with t1<
ti<
t2 and for identifying a second electrical charge Q2 of opposite polarity to Q1 during said second measurement period at said time ti after t2, with t2<
ti<
t3; and
means for forming a difference Δ
Q by adding Q1+Q2, with Δ
Q being proportional to an amount of oxygen in said blood.- View Dependent Claims (5, 6)
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Specification