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Electrochemical sensor

  • US 6,236,873 B1
  • Filed: 08/09/1999
  • Issued: 05/22/2001
  • Est. Priority Date: 09/30/1996
  • Status: Expired due to Fees
First Claim
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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:

  • 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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