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Real-time self-calibrating sensor system and method

  • US 7,774,038 B2
  • Filed: 12/30/2005
  • Issued: 08/10/2010
  • Est. Priority Date: 12/30/2005
  • Status: Active Grant
First Claim
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1. A method of calibrating a sensor configured to produce a signal indicative of a characteristic of a user, wherein the sensor includes a counter electrode, a reference electrode, and a working electrode, said electrodes being in communication with the user'"'"'s blood or interstitial fluids and connected in an electrical circuit such that a first voltage V1 equal to the difference between the working electrode voltage and the reference electrode voltage provides a first input into an operational amplifier, a second voltage V2 provides a second input into the operational amplifier, and the output of the operational amplifier is electrically connected to the counter electrode via a current-interrupt switch, said method comprising:

  • a. measuring V1 between the working and reference electrodes at a time when said switch is closed;

    b. subsequent to step (a), opening the switch, using a control unit, while obtaining a multiplicity of successive measurements for V1 during a pre-determined time period that starts prior to, and ends after, the opening of the switch;

    c. determining, using a processor unit, the magnitude of a third voltage V3=V1t=0, wherein V3 is indicative of an overpotential at the working electrode, and V1t=0 is the magnitude of V1 at the point in time when the switch is opened;

    d. based on the determined value of V3 and a voltage Vset, calculating, using the processor unit, V2 in such a way as to have V3 become substantially equal to Vset, wherein Vset is the optimally desired voltage between the working and reference electrodes; and

    e. applying, using the control unit, the calculated value of V2 as said second input to the operational amplifier.

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