Patent ID: 8249683

Claim:
A system for calibrating a sensor of a characteristic monitoring system in real time by determining, and compensating for, an IR drop across unwanted resistances in a cell, said sensor including a counter electrode, a reference electrode, and a working electrode in communication with a user's blood or interstitial fluids to produce signals indicative of said characteristic, the system comprising: a first control unit having a potentiostat, said potentiostat including an operational amplifier connected in an electrical circuit to maintain substantial equality between the magnitude of a measured voltage across the sensor's working and reference electrodes and the magnitude of an applied voltage; a current-interrupt switch electrically connected between the operational amplifier's output and the sensor's counter electrode to provide a closed circuit when the switch is closed and an open circuit when the switch is opened; and a second control unit including a microprocessor and connected in the electrical circuit to maintain substantial equality between the magnitude of an optimally desired voltage across the sensor's working and reference electrodes and the magnitude of an effective amount of potential in the cell that drives electrochemical reactions at the working electrode, said effective amount of potential reflecting an adjustment for the magnitude of said IR drop, and said second control unit providing said applied voltage as an input to the operational amplifier, wherein the second control unit calculates the magnitude of said effective amount of potential in the cell by subtracting the magnitude of the IR drop from the closed-circuit magnitude of said measured voltage across the sensor's working and reference electrodes.