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Application of electrochemical impedance spectroscopy in sensor systems, devices, and related methods

  • US 9,863,911 B2
  • Filed: 08/02/2017
  • Issued: 01/09/2018
  • Est. Priority Date: 06/08/2012
  • Status: Active Grant
First Claim
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1. A method of performing real-time sensor diagnostics on a subcutaneous or implanted sensor of a sensor system, said sensor including at least one working electrode and said sensor system including a microprocessor that is operatively connected to said sensor, the method comprising:

  • (a) periodically performing an electrochemical impedance spectroscopy (EIS) procedure to generate multiple sets of impedance-related data for said at least one working electrode;

    (b) calculating, by said microprocessor, respective values of a plurality of impedance-related parameters based on said multiple sets of impedance-related data, said plurality of parameters including impedance, phase angle, and Nyquist slope; and

    (c) based on said respective values, determining, by said microprocessor, whether the sensor is functioning normally, wherein the microprocessor;

    (i) performs a first test based on values of real impedance or phase angle;

    (ii) performs a second test based on values of respective frequencies at which successive EIS procedures are performed;

    (iii) performs a third test based on a comparison of current and post-sensor initialization impedance values at 1 kHz;

    (iv) performs a fourth test based on the value of post-sensor initialization impedance at 0.1 Hz;

    (v) performs a fifth test based on a global change in the value of Nyquist slope between 0.1 Hz and 1 Hz;

    (vi) performs a sixth test based on a change, over time, in the magnitude of real impedance;

    (vii) determines that the sensor is functioning normally if at least 3 of said first through sixth tests are satisfied by generating results that fall within respective predetermined criteria,wherein the microprocessor determines that the first test is satisfied if either |(Zn−

    ZI)/ZI|>

    30% at 1 kHz, wherein Z1 is the value of real impedance measured at a first EIS run and Zn is the value of real impedance measured at a subsequent EIS run, or the phase angle change is greater than 10°

    at 0.1 Hz between said first and subsequent EIS runs,wherein the microprocessor determines that the second test is satisfied if, at a phase angle of −

    45°

    , the difference in frequency between two consecutive EIS runs (f2-fl) is greater than 10 Hz, andwherein the microprocessor determines that the third test is satisfied if the current value of impedance is less than the post-initialization value of impedance at 1 kHz.

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