Method and apparatus for providing stable voltage to analytical system
Inventors
Diamond, Steven • Forest, Martin • Wei, Baoguo
Assignees
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Publication Number
US-8030942-B2
Publication Date
2011-10-04
Expiration Date
Abstract
An electrochemical cell has two terminals. One of the terminals is connected to a pulse-width-modulated (PWM) power supply and to a voltmeter. The other terminal is connected to circuitry capable of switching between amperometric and potentiometric measurement modes. A sequence of successive approximations permits selection of a PWM duty cycle giving rise to a desired voltage at the terminal connected with the power supply. In this way a stable excitation voltage is supplied to the cell even in the face of supply voltage instability or drift or instability in electronics coupled with the cell.
Core Innovation
The invention provides an analytical system using an electrochemical cell that has a working electrode and other electrodes. A microcontroller drives a PWM power supply to deliver an excitation voltage to the working electrode, and the system applies a successive-approximation procedure that adjusts the PWM duty cycle to achieve and maintain a desired stable excitation voltage at the working electrode despite supply drift or instability.
The system supports switching between amperometric and potentiometric measurement modes using operational amplifier and switch configurations. Calibration is performed before measurement, and the system performs recalibration after sample introduction, using the same successive-approximation approach to update the control used to maintain the desired excitation voltage.
After calibration and/or recalibration, the system measures sample current or cell voltage and relates the measurement to electrode potentials while considering offset and drift. The disclosed use case includes electrochemical measurement of an analyte in a sample, where bodily fluid such as blood and an enzyme such as glucose oxidase are referenced.
Claims Coverage
The partial content includes two independent claims. Across the independent claims, two main inventive features are repeatedly tied to successive approximation calibration of a potentially unstable voltage source and the use of a digital control signal to maintain a desired excitation voltage at an electrode for electrochemical measurement.
Maintaining a desired excitation voltage using successive-approximation calibration and a digital control signal
Performing a calibration step comprising applying an excitation voltage from a potentially unstable voltage source to the first and second electrodes in each of a plurality of successive steps to arrive by successive approximation at a digital control signal for the voltage source that produces the desired voltage to be applied to the electrodes; and applying the digital control signal to the voltage source to maintain the excitation voltage at the desired level.
Electrochemical measurement of an analyte using calibrated excitation voltage and current measurement
Calibrating an electrochemical device comprising a potentially unstable voltage source and first and second electrodes of an electrochemical cell by applying an excitation voltage to the first and second electrodes in each of a plurality of successive steps to arrive by successive approximation at a digital control signal for the voltage source that produces a desired voltage to be applied to the electrodes; introducing the sample into the electrochemical cell; applying the desired voltage to the first electrode using the digital control signal; and measuring current between the electrodes as an indication of the amount of analyte in the sample.
Both independent claims center on successive-approximation calibration of a potentially unstable voltage source to generate a digital control signal that produces and maintains a desired excitation voltage at electrodes, enabling electrochemical measurement where current between electrodes indicates the amount of analyte.
Stated Advantages
Maintains the excitation voltage at a desired level despite a potentially unstable voltage source.
Enables electrochemical measurement of an analyte by measuring current between electrodes as an indication of the amount of analyte in the sample.
Supports recalibration after sample introduction using successive approximation.
Documented Applications
Electrochemical measurement of an analyte in a sample, including bodily fluid such as blood, and using an enzyme such as glucose oxidase.
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