Methods, systems, and devices for electrode capacitance calculation and application
First Claim
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1. A method for real-time monitoring of a subcutaneous or implantable glucose sensor for measuring the level of glucose in a body of a user, said sensor including physical sensor electronics, a microcontroller, and a working electrode (WE) in an electrical circuit that provides an input current to the working electrode, the method comprising:
- (a) measuring, by said sensor electronics, a first current level for the working electrode current;
(b) after measuring said first current level, open circuiting, by said microcontroller, the working electrode by discontinuing said input current to the working electrode;
(c) after open circuiting the working electrode, measuring, by said sensor electronics, a first WE voltage value;
(d) after a predefined time interval after measurement of said first WE voltage value, measuring, by said sensor electronics, a second WE voltage value;
(e) calculating a WE voltage difference between said first and second WE voltage values and determining whether said difference exceeds a threshold WE-voltage difference value; and
(f) if said WE voltage difference exceeds said threshold output-voltage difference value, calculating the working electrode'"'"'s capacitance by the relation C=(I)/(dV/dT), wherein I is the first current level, dV is the difference between said first and second WE voltage values, and dT is the difference between respective points in time when said first and second WE voltage values were measured,wherein, if said WE voltage difference is less than or equal to said threshold WE-voltage difference value, the method further comprises;
(1) waiting for an amount of time equal to said predefined time interval and measuring an additional WE voltage value;
(2) calculating an updated WE voltage difference as the difference between said first WE voltage value and said additional WE voltage value;
(3) determining whether said updated WE voltage difference exceeds said threshold WE-voltage difference value; and
(4) if said updated WE voltage difference exceeds said threshold WE-voltage difference value, calculating the working electrode'"'"'s capacitance by the relation C=(I)/(dV/dT), wherein I is the first current level, dV is the value of said updated WE voltage difference, and dT is the difference between respective points in time when said first and additional WE voltage values were measured;
wherein, if said updated WE voltage difference is less than or equal to said threshold WE-voltage difference value, the method further includes, prior to step (4), iteratively repeating steps (1)-(3) until said updated WE voltage difference exceeds said threshold WE-voltage difference value; and
wherein said iterative repetition cannot occur beyond a time-out window.
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Abstract
The double layer capacitance of a working electrode of a sensor may be measured with minimal disruption to the sensor equilibrium by open circuiting the working electrode and measuring the voltage drift on a periodic, or as-needed, basis. The values of the double layer capacitance may be monitored over time to determine, e.g., sensor age and condition.
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Citations
18 Claims
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1. A method for real-time monitoring of a subcutaneous or implantable glucose sensor for measuring the level of glucose in a body of a user, said sensor including physical sensor electronics, a microcontroller, and a working electrode (WE) in an electrical circuit that provides an input current to the working electrode, the method comprising:
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(a) measuring, by said sensor electronics, a first current level for the working electrode current; (b) after measuring said first current level, open circuiting, by said microcontroller, the working electrode by discontinuing said input current to the working electrode; (c) after open circuiting the working electrode, measuring, by said sensor electronics, a first WE voltage value; (d) after a predefined time interval after measurement of said first WE voltage value, measuring, by said sensor electronics, a second WE voltage value; (e) calculating a WE voltage difference between said first and second WE voltage values and determining whether said difference exceeds a threshold WE-voltage difference value; and (f) if said WE voltage difference exceeds said threshold output-voltage difference value, calculating the working electrode'"'"'s capacitance by the relation C=(I)/(dV/dT), wherein I is the first current level, dV is the difference between said first and second WE voltage values, and dT is the difference between respective points in time when said first and second WE voltage values were measured, wherein, if said WE voltage difference is less than or equal to said threshold WE-voltage difference value, the method further comprises; (1) waiting for an amount of time equal to said predefined time interval and measuring an additional WE voltage value; (2) calculating an updated WE voltage difference as the difference between said first WE voltage value and said additional WE voltage value; (3) determining whether said updated WE voltage difference exceeds said threshold WE-voltage difference value; and (4) if said updated WE voltage difference exceeds said threshold WE-voltage difference value, calculating the working electrode'"'"'s capacitance by the relation C=(I)/(dV/dT), wherein I is the first current level, dV is the value of said updated WE voltage difference, and dT is the difference between respective points in time when said first and additional WE voltage values were measured; wherein, if said updated WE voltage difference is less than or equal to said threshold WE-voltage difference value, the method further includes, prior to step (4), iteratively repeating steps (1)-(3) until said updated WE voltage difference exceeds said threshold WE-voltage difference value; and wherein said iterative repetition cannot occur beyond a time-out window. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for determining whether a used subcutaneous or implantable glucose sensor is being used by a user for measuring the level of glucose in the user'"'"'s body, said sensor including physical sensor electronics, a microcontroller, and a working electrode (WE) in an electrical circuit that provides an input current to the working electrode, the method comprising:
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(a) measuring, by said sensor electronics, a first current level for the working electrode current; (b) after measuring said first current level, open circuiting, by said microcontroller, the working electrode by discontinuing said input current to the working electrode; (c) after open circuiting the working electrode, measuring, by said sensor electronics, a first WE voltage value; (d) after a predefined time interval after measurement of said first WE voltage value, measuring, by said sensor electronics, a second WE voltage value; (e) calculating the working electrode'"'"'s capacitance based on said first and second WE voltage values; (f) periodically repeating steps (a) (e) and monitoring the working electrode'"'"'s capacitance over a predetermined time interval, wherein said predetermined time interval is between about 15 and about 30 minutes; and (g) determining that the sensor is a used sensor if the change in the working electrode'"'"'s capacitance over said predetermined time interval is less than a threshold capacitance value, wherein said threshold capacitance value is between about 3% and about 5%. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification