Method and apparatus for providing a stable voltage to an analytical system
First Claim
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1. An apparatus comprising a circuit for applying a stable voltage to an electrochemical test cell received within the apparatus, said circuit comprising:
- (a) a first connector for making contact with a working electrode in the electrochemical test cell,(b) a second connector for making contact with a counter electrode in the electrochemical test cell,(c) a working-side circuit connected to the first connector,(d) a counter-side circuit connected to the second connector, and(e) a microcontroller receiving input from the working-side circuit and the counter-side circuit, said microcontroller being programmed to provide output of an amount of analyte in a liquid sample disposed within the electrochemical cell when the electrochemical cell is in contact with the first and second connectors,whereinthe working-side circuit comprisesa first operational amplifier having the output and inverting input connected to the first connector,a first signal input controllable by the microcontroller, said first signal input being connected to the non-inverting input of the first operational amplifier,a first working-side signaling line connected to the first signal input or a second working-side signaling line connected between the output of the first operational amplifier and the first connector, or both; and
the counter-side circuit comprisesa voltage referencesecond, and third operational amplifiers andfirst and second switches controllable by the microprocessor,said second signal input being connected to the microcontroller via a first counter-side signal line,said second connector being connected to the microprocessor via second operational amplifier and a second counter-side signal line when first switch is closed, said second operational amplifier acting as a current sensing device or current to voltage converter (I/V) with respect to the signal from the second connector, and having second signal input connected to the non-inverting input,said third operational amplifier connecting the second connector to the microcontroller via a third counter-side signal line, andsaid second switch being disposed in a loop connecting the inverting input an the output of the second operational amplifier, whereby opening or closing the second switch alters the gain of the second operational amplifier.
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Abstract
A method and apparatus for provide a stable voltage to an electrochemical cell used for measurement of an analyte such as glucose in a liquid sample. The apparatus uses a circuit in which multiple switching positions provide both calibration information for use in calibration of electronic components in the circuit and error checking functionality.
114 Citations
15 Claims
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1. An apparatus comprising a circuit for applying a stable voltage to an electrochemical test cell received within the apparatus, said circuit comprising:
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(a) a first connector for making contact with a working electrode in the electrochemical test cell, (b) a second connector for making contact with a counter electrode in the electrochemical test cell, (c) a working-side circuit connected to the first connector, (d) a counter-side circuit connected to the second connector, and (e) a microcontroller receiving input from the working-side circuit and the counter-side circuit, said microcontroller being programmed to provide output of an amount of analyte in a liquid sample disposed within the electrochemical cell when the electrochemical cell is in contact with the first and second connectors, wherein the working-side circuit comprises a first operational amplifier having the output and inverting input connected to the first connector, a first signal input controllable by the microcontroller, said first signal input being connected to the non-inverting input of the first operational amplifier, a first working-side signaling line connected to the first signal input or a second working-side signaling line connected between the output of the first operational amplifier and the first connector, or both; and the counter-side circuit comprises a voltage reference second, and third operational amplifiers and first and second switches controllable by the microprocessor, said second signal input being connected to the microcontroller via a first counter-side signal line, said second connector being connected to the microprocessor via second operational amplifier and a second counter-side signal line when first switch is closed, said second operational amplifier acting as a current sensing device or current to voltage converter (I/V) with respect to the signal from the second connector, and having second signal input connected to the non-inverting input, said third operational amplifier connecting the second connector to the microcontroller via a third counter-side signal line, and said second switch being disposed in a loop connecting the inverting input an the output of the second operational amplifier, whereby opening or closing the second switch alters the gain of the second operational amplifier. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A system for electrochemical measurement of an analyte in a liquid sample, said system comprising an apparatus and an electrochemical test cell received within the apparatus, wherein the apparatus comprises apparatus comprising a circuit for applying a stable voltage to the electrochemical test cell, said circuit comprising:
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(a) a first connector for making contact with a working electrode in the electrochemical test cell, (b) a second connector for making contact with a counter electrode in the electrochemical test cell, (c) a working-side circuit connected to the first connector, (d) a counter-side circuit connected to the second connector, and (e) a microcontroller receiving input from the working-side circuit and the counter-side circuit, said microcontroller being programmed to provide output of an amount of analyte in a liquid sample disposed within the electrochemical cell when the electrochemical cell is in contact with the first and second connectors, wherein the working-side circuit comprises a first operational amplifier having the output and inverting input connected to the first connector, a first signal input controllable by the microcontroller, said first signal input being connected to the non-inverting input of the first operational amplifier, a first working-side signaling line connected to the first signal input or a second working-side signaling line connected between the output of the first operational amplifier and the first connector, or both; and the counter-side circuit comprises a voltage reference second, and third operational amplifiers and first and second switches controllable by the microprocessor said second signal input being connected to the microcontroller via a first counter-side signal line said second connector being connected to the microprocessor via second operational amplifier and a second counter-side signal line when first switch is closed, said second operational amplifier acting as a current sensing device or current to voltage converter (I/V) with respect to the signal from the second connector, and having second signal input connected to the non-inverting input, said third operational amplifier connecting the second connector to the microcontroller via a third counter-side signal line, and said second switch being disposed in a loop connecting the inverting input an the output of the second operational amplifier, whereby opening or closing the second switch alters the gain of the second operational amplifier. - View Dependent Claims (11)
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12. A method for providing a stable voltage to an electrochemical test cell comprising the steps of:
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inserting an electrochemical test cell into an apparatus comprising a circuit for applying a stable voltage to the electrochemical test cell, performing a hardware diagnosis and calibration step on the apparatus; introducing a liquid sample into the electrochemical test cell; recalibrating the apparatus after introduction of the liquid sample; and performing an electrochemical assay for an analyte in the liquid sample, wherein the circuit for applying a stable voltage comprises; (a) a first connector for making contact with a working electrode in the electrochemical test cell, (b) a second connector for making contact with a counter electrode in the electrochemical test cell, (c) a working-side circuit connected to the first connector, (d) a counter-side circuit connected to the second connector, and (e) a microcontroller receiving input from the working-side circuit and the counter-side circuit, said microcontroller being programmed to provide output of an amount of analyte in a liquid sample disposed within the electrochemical cell when the electrochemical cell is in contact with the first and second connectors, wherein the working-side circuit comprises a first operational amplifier having the output and inverting input connected to the first connector, a first signal input controllable by the microcontroller, said first signal input being connected to the non-inverting input of the first operational amplifier, a first working-side signaling line connected to the first signal input or a second working-side signaling line connected between the output of the first operational amplifier and the first connector, or both; and the counter-side circuit comprises a voltage reference second, and third operational amplifiers and first and second switches controllable by the microprocessor, said second signal input being connected to the microcontroller via a first counter-side signal line, said second connector being connected to the microprocessor via second operational amplifier and a second counter-side signal line when first switch is closed, said second operational amplifier acting as a current sensing device or current to voltage converter (I/V) with respect to the signal from the second connector, and having second signal input connected to the non-inverting input, said third operational amplifier connecting the second connector to the microcontroller via a third counter-side signal line, and said second switch being disposed in a loop connecting the inverting input an the output of the second operational amplifier, whereby opening or closing the second switch alters the gain of the second operational amplifier, and wherein the calibration step and/or the recalibration step comprises determining an offset for the second operational amplifier from a comparison of the observed reference voltage at the first counter-side signal line and the potential at the second counter signal line with the first switch open and the second switch closed, and determining the offset of the third operational amplifier from a comparison of two or more of the observed reference voltage at the first counter-side signal line, the potential at the third counter-side signal line and the potential at the second counter signal line with the first switch closed and the second switch open or closed. - View Dependent Claims (13, 14, 15)
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Specification