Monitoring and compensating for temperature-related error in an electrochemical sensor
A method for compensating for a temperature-related error in an electrochemical sensor without using separate sources of temperature measurement by measuring sensor current, temporarily lowering sensor voltage to a first level below a reaction-sustaining threshold, measuring a first offset current, adjusting sensor voltage to a second level below the threshold, measuring a second offset current, calculating a difference between the offset currents, deriving a temperature compensation value from the difference based on empirical data, and adding the value to the measured sensor current. A computer system may execute the method as an algorithm stored in memory, provide automatic control of the sensor, and provide continuous display of corrected output values.
1. A method of compensating for temperature-related errors in an electrochemical sensor that outputs a current proportional to an analyte concentration when a voltage is applied to the sensor, the method comprising:
measuring current output from the sensor;
lowering sensor voltage to a first voltage level below a reaction-sustaining threshold;
measuring a first offset current corresponding to the first voltage level;
adjusting sensor voltage to a second voltage level below the reaction-sustaining threshold, wherein said second voltage level is different from said first voltage level;
measuring a second offset current corresponding to the second voltage level;
calculating a difference between the first and second offset currents;
deriving a temperature compensation value based in part on the difference; and
adding the temperature compensation value to the measured current output to obtain an analyte concentration corrected for temperature.
2. The method of claim 1 wherein the sensor voltage is applied to a counter electrode or a working electrode on the electrochemical sensor.
3. The method of claim 1 wherein the sensor comprises a glucose sensor.
4. The method of claim 3 wherein the glucose sensor includes glucose oxidase.
5. The method of claim 1 wherein the sensor comprises first and second working electrodes.
6. The method of claim 5 wherein the first working electrode comprises glucose oxidase and the second working electrode comprises a reference electrode.
7. The method of claim 1 wherein the reaction-sustaining threshold is a reduction threshold or an oxidation threshold.
8. The method of claim 1 further comprising displaying a value representing the temperature-corrected analyte concentration.
9. A system for compensating for temperature-related errors in an electrochemical sensor that outputs a current proportional to an analyte concentration when a voltage is applied to the sensor, comprising:
a sensor having a working electrode;
a potentiostat for adjusting voltage applied to the working electrode;
a processor coupled to memory; and
temperature compensation software stored in the memory and executable by the processor, wherein responsive to the processor executing the software, the potentiostat temporarily lowers the voltage of the working electrode to a first voltage level below a reaction-sustaining threshold, and thereafter to a second voltage level below that reaction-sustaining level, and wherein said first and second offset currents measured at said first and second voltage levels are then compared to obtain a temperature compensation value for correcting sensor output when the voltage of the working electrode is raised above the reaction-sustaining threshold, wherein said first and second voltage levels are different from one another.
10. The system of claim 9 wherein the sensor comprises a glucose sensor.
11. The system of claim 10 wherein the glucose sensor includes glucose oxidase.
12. The system of claim 9 further comprising a display coupled to the processor for displaying analyte concentration corrected according to the temperature compensation value.
13. The system of claim 9 wherein the reaction-sustaining threshold is a reduction threshold or an oxidation threshold.