Real-time self-calibrating sensor system and method
First Claim
1. A method of calibrating a sensor configured to produce a signal indicative of a characteristic of a user, wherein the sensor includes a counter electrode, a reference electrode, and a working electrode, said electrodes being in communication with the user'"'"'s blood or interstitial fluids and connected in an electrical circuit such that a first voltage V1 equal to the difference between the working electrode voltage and the reference electrode voltage provides a first input into an operational amplifier, a second voltage V2 provides a second input into the operational amplifier, and the output of the operational amplifier is electrically connected to the counter electrode via a current-interrupt switch, said method comprising:
- a. measuring V1 between the working and reference electrodes at a time when said switch is closed;
b. subsequent to step (a), opening the switch, using a control unit, while obtaining a multiplicity of successive measurements for V1 during a pre-determined time period that starts prior to, and ends after, the opening of the switch;
c. determining, using a processor unit, the magnitude of a third voltage V3=V1t=0, wherein V3 is indicative of an overpotential at the working electrode, and V1t=0 is the magnitude of V1 at the point in time when the switch is opened;
d. based on the determined value of V3 and a voltage Vset, calculating, using the processor unit, V2 in such a way as to have V3 become substantially equal to Vset, wherein Vset is the optimally desired voltage between the working and reference electrodes; and
e. applying, using the control unit, the calculated value of V2 as said second input to the operational amplifier.
1 Assignment
0 Petitions
Accused Products
Abstract
A system and method for calibrating a sensor of a characteristic monitoring system in real time utilizes a self-calibration module for periodic determination of, and compensation for, the IR drop across unwanted resistances in a cell. A current-interrupt switch is used to open the self-calibration module circuit and either measure the IR drop using a high-frequency (MHz) ADC module, or estimate it through linear regression of acquired samples of the voltage across the sensor'"'"'s working and reference electrodes (Vmeasured) over time. The IR drop is then subtracted from the closed-circuit value of Vmeasured to calculate the overpotential that exists in the cell (Vimportant). Vimportant may be further optimized by subtracting the value of the open-circuit voltage (Voc) across the sensor'"'"'s working and reference electrodes. The values of Vmeasured and Vimportant are then controlled by respective first and second control units to compensate for the IR drop.
-
Citations
79 Claims
-
1. A method of calibrating a sensor configured to produce a signal indicative of a characteristic of a user, wherein the sensor includes a counter electrode, a reference electrode, and a working electrode, said electrodes being in communication with the user'"'"'s blood or interstitial fluids and connected in an electrical circuit such that a first voltage V1 equal to the difference between the working electrode voltage and the reference electrode voltage provides a first input into an operational amplifier, a second voltage V2 provides a second input into the operational amplifier, and the output of the operational amplifier is electrically connected to the counter electrode via a current-interrupt switch, said method comprising:
-
a. measuring V1 between the working and reference electrodes at a time when said switch is closed; b. subsequent to step (a), opening the switch, using a control unit, while obtaining a multiplicity of successive measurements for V1 during a pre-determined time period that starts prior to, and ends after, the opening of the switch; c. determining, using a processor unit, the magnitude of a third voltage V3=V1t=0, wherein V3 is indicative of an overpotential at the working electrode, and V1t=0 is the magnitude of V1 at the point in time when the switch is opened; d. based on the determined value of V3 and a voltage Vset, calculating, using the processor unit, V2 in such a way as to have V3 become substantially equal to Vset, wherein Vset is the optimally desired voltage between the working and reference electrodes; and e. applying, using the control unit, the calculated value of V2 as said second input to the operational amplifier. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
-
-
20. A self-calibrating characteristic monitoring system for monitoring a characteristic of a user, said system comprising:
-
a sensor for producing a signal indicative of said characteristic, the sensor including a counter electrode, a reference electrode, and a working electrode in communication with the user'"'"'s blood or interstitial fluids; a sensor-calibration module having a first control unit, wherein the control unit comprises an operational amplifier connected in an electrical circuit such that a voltage V1 equal to the measured difference between the working electrode voltage and the reference electrode voltage provides a first input into the operational amplifier, an applied voltage V2 provides a second input into the operational amplifier, and the output of the operational amplifier is electrically connected to the counter electrode via a current-interrupt switch, said sensor-calibration module being configured to calibrate the sensor based on the value of the measured voltage V1 and the magnitude of an IR drop due to a resistance between the reference and working electrodes; and a remotely located data receiving device for receiving data indicative of said characteristic based on said signal. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52)
-
-
53. A machine-readable medium for use in conjunction with a sensor configured to produce a signal indicative of a characteristic of a user, wherein the sensor includes a counter electrode, a reference electrode, and a working electrode, said electrodes being in communication with the user'"'"'s blood or interstitial fluids and connected in an electrical circuit such that a first voltage V1 equal to the difference between the working electrode voltage and the reference electrode voltage provides a first input into an operational amplifier, a second voltage V2 provides a second input into the operational amplifier, and the output of the operational amplifier is electrically connected to the counter electrode via a current interrupt switch, said medium being encoded with instructions that, when executed, cause a computer to perform a sensor-calibration process comprising:
-
a. obtaining a measurement for V1 at a time when the current-interrupt switch is closed; b. transmitting an instruction to open the switch while obtaining a multiplicity of successive measurements for V1 during a pre-determined time period that starts prior to, and ends after, the opening of the switch; c. determining the magnitude of a voltage V3=V1t=0, wherein V3 is indicative of an overpotential at the working electrode, and V1t=0 is the magnitude of V1 at the point in time when the switch is opened; d. based on the determined value of V3 and a voltage Vset, calculating V2 in such a way as to have V3 become substantially equal to Vset, wherein Vset is the optimally desired voltage between the working and reference electrodes; and e. transmitting an instruction to close the current-interrupt switch and apply the calculated value of V2 as said second input to the operational amplifier. - View Dependent Claims (54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65)
-
-
66. A method of calibrating a sensor configured to produce a signal indicative of a characteristic of a user, wherein the sensor includes a counter electrode, a reference electrode, and a working electrode, said electrodes being in communication with the user'"'"'s blood or interstitial fluids and connected in an electrical circuit such that a first voltage V1 equal to the difference between the working electrode voltage and the reference electrode voltage provides a first input into a comparator, a second voltage V2 provides a second input into the comparator, and the output of the comparator is electrically connected to the counter electrode, said method comprising:
-
a. measuring V1 between the working and reference electrodes; b. determining, using a processor unit, the magnitude of a third voltage V3, wherein V3 is indicative of an overpotential at the working electrode; c. based on the determined value of V3 and a voltage Vset, calculating using the processor unit, V2 in such a way as to have V3 become substantially equal to Vset, wherein Vset is the optimally desired voltage between the working and reference electrodes; and d. applying, using a control unit, the calculated value of V2 as said second input to the comparator. - View Dependent Claims (67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79)
-
Specification