Measuring device and methods for use therewith
View Patent ↗The ability to switch at will between amperometric measurements and potentiometric measurements provides great flexibility in performing analyzes of unknowns. Apparatus and methods can provide such switching to collect data from an electrochemical cell. The cell may contain a reagent disposed to measure glucose in human blood.
1. A test equipment for receiving an electrochemical cell comprising at least first and second electrodes and a reagent reactive with a constituent of a human bodily fluid, said equipment comprising:
at least first and second connectors for providing electric contact between the test equipment and at least first and second electrodes of a received electrochemical cell,
a source of potential for applying a potential difference between the at least first and second electrodes through the at least first and second connectors;
potentiometric circuitry;
electronic control means, the electronic control means coupled with the source of potential to controllably apply the source of potential to the electrochemical cell, thereby allowing current to flow through the cell; and
amperometric means external to the electrochemical cell for measuring the flow of current through the electrochemical cell;
wherein the electronic control means is coupled with the potentiometric circuitry to automatically cease application of potential to the electrochemical cell, and then cause the potentiometric circuitry to measure a decay in chemical potential at the electrochemical cell in the absence of the applied potential.
2. The test equipment of claim 1 further comprising a housing, having an opening for receiving the electrochemical cell and placing it in electrical connection with the at least first and second connectors, and wherein the housing contains the source of potential, the potentiometric circuitry, and the electronic control means.
3. The test equipment of claim 2 , wherein the electronic control means comprises a first switch for selectively disconnecting the first electrode from the source of potential, to cease the application of potential to the electrochemical cell by opening the first switch.
4. The test equipment of claim 3 , wherein the electronic control means further comprises a second switch for selectively disconnecting the second electrode from the source of potential, to cease the application of potential to the electrochemical cell by opening the second switch.
5. The test equipment of claim 1 wherein the source of potential comprises a constant-potential source.
6. The test equipment of claim 5 , further comprising a display for displaying to a human user an indication of the constituent of the bodily fluid.
7. The test equipment of claim 1 for receiving an electrochemical cell comprising at least first, second and third electrodes and a reagent reactive with a constituent of a human bodily fluid, said equipment further comprising a third connector for providing electric contact between the test equipment and the third electrode a received electrochemical cell.
8. The test equipment of claim 7 , wherein the first connector connects to a first electrode in the electrochemical cell that serves as a working electrode, the second connector connects to a second electrode in the electrochemical cell that serves as a counter electrode, and the third connector connects to a third electrode in the electrochemical cell that serves as a reference electrode, and the potentiometric circuitry measures the potential difference between the first electrode and the second electrode and wherein the electronic control means comprises two switches, a first switch for isolating the counter electrode from an input voltage signal from an amplifier, and a second switch for isolating the working electrode from the amperometric means.
9. The test equipment of claim 8 , where the electronic control means further comprises a third switch that isolates the reference electrode from the feedback path of the amplifier.
10. The test equipment of claim 7 , wherein the first connector connects to a first electrode in the electrochemical cell that serves as a working electrode, the second connector connects to a second electrode in the electrochemical cell that serves as a counter electrode, and the third connector connects to a third electrode in the electrochemical cell that serves as a reference electrode, and the potentiometric circuitry measures the potential difference between the first electrode and the third electrode and wherein the electronic control means comprises at least two switches, a first switch for isolating the reference electrode from the feedback path of an amplifier through which an input voltage is applied to the counter electrode, and a second switch for isolating the working electrode from the amperometric means.
11. The test equipment of claim 10 , where the electronic control means further comprises a third switch that isolates the counter electrode from the input voltage signal from the amplifier.