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

  • US 10,335,077 B2
  • Filed: 11/20/2017
  • Issued: 07/02/2019
  • 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;

    (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, and that the sensor is not functioning normally if less than 3 of said first through sixth tests are satisfied by generating results that fall within respective predetermined criteria,wherein 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,wherein the microprocessor determines that the fourth test is satisfied if the value of impedance is less than 300 kOhms at 0.1 Hz during post-initialization sensor operation, andwherein the microprocessor determines that the fifth test is satisfied if the value of Nyquist slope is determined to be globally increasing from 0.1 Hz to 1 Hz; and

    (d) based on said determination that the sensor is not functioning normally, sending an alert to a user of the sensor, by the microprocessor, that the sensor should be replaced.

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