# US 11,998,327 B2 · Methods, systems, and devices for electrode capacitance calculation and application

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- Number: US 11,998,327 B2
- Document ID: US11998327B2
- Status: Granted
- Kind: B2
- Application number: 16/533,131
- Filed: 2019-08-06
- Published: 2019-11-28
- Granted: 2024-06-04
- Earliest claimed: 2016-04-28
- Assignees: Medtronic MiniMed, Inc.
- Applicants: Medtronic Minimed, Inc.
- Inventors: Wayne A. Morgan
- Web page: https://patentgrep.com/patent/US11998327B2

## CPC

- A61B 5/1473: invasive, e.g. introduced into the body by a catheter
- A61B 5/0002: {Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network (endoradiosondes A61B5/07)}
- A61B 5/053: Measuring electrical impedance or conductance of a portion of the body
- A61B 5/14532: {for measuring glucose, e.g. by tissue impedance measurement}
- A61B 5/14865: {invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors}
- A61B 5/1495: Calibrating or testing of in-vivo probes
- A61B 5/6849: {in combination with a needle set}
- A61B 5/7203: {for noise prevention, reduction or removal}
- A61B 5/7225: {Details of analogue processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation (input circuits for detecting, measuring, or recording bioelectric or biomagnetic signals A61B5/30; specific diagnostic methods using bioelectric or biomagnetic signals A61B5/316)}
- A61B 2560/0214: of power generation or supply
- A61B 2560/0223: of calibration, e.g. protocols for calibrating sensors
- A61B 2562/0214: Capacitive electrodes
- A61B 2562/166: the sensor is mounted on a specially adapted printed circuit board
- A61B 2562/227: Sensors with electrical connectors
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## 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.

## Claims

### Claim 1

A method for real-time monitoring of a subcutaneous glucose sensor, said subcutaneous glucose sensor including physical sensor electronics, a microcontroller, and a working electrode (WE), the method comprising:
(a) measuring, by said physical sensor electronics, a first current level for the working electrode;
(b) after measuring said first current level, open circuiting, by said microcontroller, the working electrode by discontinuing input current to the working electrode for a time period having a predefined duration;
(c) during said time period, measuring, by said physical sensor electronics, a first WE voltage value and a second WE voltage value, said first WE voltage value being measured at a first point in time after open circuiting the working electrode, said second WE voltage value being measured at a second point in time after open circuiting the working electrode, and said first and second WE voltage values being measured when a current level for the working electrode is substantially zero;
(d) calculating, by said physical sensor electronics or said microcontroller, the working electrode's capacitance by a relation C=(I)/(dV/dT), wherein I is the first current level, dV is a difference between said first and second WE voltage values, and dT is a difference between said first and second points in time;
(e) repeating operations of (a)-(d) periodically;
(f) determining, by said physical sensor electronics or said microcontroller, a change in the working electrode's capacitance over a time period;
(g) determining, by said physical sensor electronics or said microcontroller, whether the subcutaneous glucose sensor is previously used based on the change in the working electrode's capacitance over the time period; and
(h) responsive to determining that the subcutaneous glucose sensor is previously used, causing replacement of the subcutaneous glucose sensor.

### Claim 2 (depends on 1)

The method of claim 1, further including:
resuming said input current to the working electrode after said second point in time.

### Claim 3 (depends on 1)

The method of claim 1, wherein the operations of (a)-(d) are repeated about once every 5-15 minutes.

### Claim 4 (depends on 1)

The method of claim 1, wherein the operations of (a)-(d) are repeated about once every 5 minutes.

### Claim 5 (depends on 1)

The method of claim 1, wherein said subcutaneous glucose sensor includes a plurality of working electrodes, and wherein operations of (a)-(e) are performed for each of said plurality of working electrodes.

### Claim 6 (depends on 5)

The method of claim 5, wherein operations of (a)-(e) are performed for all of the plurality of working electrodes at the same time.

### Claim 7 (depends on 1)

The method of claim 1, wherein said predefined duration is shorter than 30 seconds.

### Claim 8 (depends on 1)

The method of claim 1, wherein said dT is between about 7 seconds and about 15 seconds long.

### Claim 9 (depends on 8)

The method of claim 8, wherein said dT is about 10 seconds long.