Application of electrochemical impedance spectroscopy in sensor systems, devices, and related methods
View Patent ↗A diagnostic Electrochemical Impedance Spectroscopy (EIS) procedure is applied to measure values of impedance-related parameters for one or more sensing electrodes. The parameters may include real impedance, imaginary impedance, impedance magnitude, and/or phase angle. The measured values of the impedance-related parameters are then used in performing sensor diagnostics, calculating a highly-reliable fused sensor glucose value based on signals from a plurality of redundant sensing electrodes, calibrating sensors, detecting interferents within close proximity of one or more sensing electrodes, and testing surface area characteristics of electroplated electrodes. Advantageously, impedance-related parameters can be defined that are substantially glucose-independent over specific ranges of frequencies. An Application Specific Integrated Circuit (ASIC) enables implementation of the EIS-based diagnostics, fusion algorithms, and other processes based on measurement of EIS-based parameters.
1. A method for real-time detection of a signal dip for a working electrode of a glucose sensor, the method comprising:
periodically performing an electrochemical impedance spectroscopy (EIS) procedure to obtain values of real impedance at 1 kHz for said electrode;
measuring said electrode's current (Isig) over time;
monitoring, by a microprocessor, said values of real impedance over time;
based on said monitoring of said values of real impedance, determining, by said microprocessor, whether a dip exists in the signal generated by said working electrode, wherein a signal dip is determined to exist when, as the Isig decreases, the real impedance increases over time; and
based on the determination that a dip exists in said signal, determining, by said microprocessor, that said working electrode is unreliable for measuring glucose,
wherein use of said sensor for glucose measurement is delayed or sensor glucose values are blinded to a user of the sensor by the microprocessor based on the determination that the working electrode is unreliable.
2. The method of claim 1 , wherein said EIS procedure is performed for a predetermined range of frequencies.
3. The method of claim 1 , wherein said values of real impedance are substantially glucose-independent.
4. A method for real-time detection of a signal dip for a plurality of working electrodes of a glucose sensor, the method comprising:
periodically performing an electrochemical impedance spectroscopy (EIS) procedure for each of said plurality of working electrodes to obtain respective values of real impedance at 1 kHz for each said electrode;
measuring each said electrode's respective current (Isig) over time;
monitoring, by a microprocessor, said respective values of real impedance over time;
based on said monitoring of said respective values of real impedance, determining, by said microprocessor, whether at least one of said plurality of working electrodes is not experiencing a signal dip, wherein a signal dip is determined to exist when, as the respective Isig decreases, the respective value of real impedance increases over time; and
based on said determination, identifying, by said microprocessor, said at least one of said plurality of working electrodes that is not experiencing a signal dip for use to measure glucose,
wherein one or more of the plurality of working electrodes that are experiencing a signal dip are either powered down or turned off by said microprocessor.
5. The method of claim 4 , wherein each said EIS procedure is performed for a predetermined range of frequencies.
6. The method of claim 4 , wherein said respective values of real impedance are substantially glucose-independent.