OPEN CIRCUIT DELAY DEVICES, SYSTEMS, AND METHODS FOR ANALYTE MEASUREMENT

• US 20090027040A1
• Filed: 07/25/2007
• Published: 01/29/2009
• Est. Priority Date: 07/25/2007
• Status: Active Grant

• Current Assignee: Cilag Gmbh International (Johnson & Johnson)
• Original Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Inventors: Kermani, Mahyar Z., Docherty, Edward, McInulty, John
• Granted Patent: US 7,794,658 B2
• Time in Patent Office: Days
• US Class Current: 324/123.R
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875

Abstract

System, circuits, and methods to reduce or eliminate uncompensated voltage drop between an electrode of an electrochemical cell usable for analyte measurement. In one example, a system is provided that includes a test strip, a reference voltage circuit, an operational amplifier connected to the reference voltage circuit to provide a predetermined fraction of a reference voltage substantially equal to the test voltage applied to the first line, the operational amplifier having an output configured for one of a connected or disconnected state to the first line, and a processing circuit connected to the output of the operational amplifier and the first line such that, during a disconnected state between the output and the first line, the processing circuit remains in connection with the first line. In another example, a method of measuring an electrochemical reaction of an electrochemical cell is provided that includes applying a test voltage to the first electrode and connecting the second electrode to ground; uncoupling the first electrode from the output of the circuit while allowing electrical communication from the first electrode to the processor; and coupling the first electrode to the output to measure a test current generated in the electrochemical cell without an uncompensated voltage drop.

Claims

1. A system to determine analyte concentration in a sample, the system comprising:

a test strip connector having a first line configured to connect to a first electrode of a test strip and a second line configured to connect to a second electrode of the test strip;

a reference voltage circuit that provides an output voltage;

an operational amplifier connected to the reference voltage circuit to provide a test voltage to the first line that is substantially equal to the output voltage, the operational amplifier having an output configured for one of a connected or disconnected state to the first line; and

a processing circuit connected to the output of the operational amplifier and the first line such that, during a disconnected state between the output and the first line, the processing circuit remains in connection with the first line.

2. The system of claim 1, further comprising a switch disposed between the output and the first line so that a nominal resistance of the switch in a closed state does not cause an uncompensated voltage drop between the working electrode and the reference electrode when the connector is coupled to the working electrode and the reference electrode.

3. The system of claim 1, in which the operational amplifier comprises a shut down logic circuit connected to the processing circuit.

4. A circuit for analyte measurement, the circuit comprising:

a test strip connector having a first line configured to connect to a first electrode of a test strip and a second line configured to connect a second electrode of the test strip to a ground;

an operational amplifier having a first input connected to a reference voltage circuit and a second input connected to both the first line and to an output of the operational amplifier via a feedback resistor; and

a switch disposed between the output and the second input of the operational amplifier to connect the output to the first line in a closed state of the switch and to disconnect the output from the first line in an opened state of the switch.

5. The circuit of claim 4, in which the reference voltage circuit comprises a reference voltage source and a voltage divider.

6. The circuit of claim 5, in which the output of the operational amp and the first line are connected to a filter.

7. The circuit of claim 6, in which the filter comprises a capacitor.

8. A circuit for analyte measurement, the circuit comprising:

a test strip connector having a first line configured to connect to a first electrode of a test strip and a second line configured to connect a second electrode of the test strip to a ground;

an operational amplifier having a first input connected to a reference voltage circuit and a second input connected to both the first line and to an output of the operational amplifier via a feedback resistor, the operational amplifier further including a shut down circuit configured to place the operational amplifier in a shut down mode.

9. The circuit of claim 8, in which the operational amplifier comprises an operational amplifier with leakage current of less than about one nanoampere upon activation of the shut down circuit.

10. The circuit of claim 8, in which the reference voltage circuit comprises a reference voltage source and a voltage divider.

11. The circuit of claim 10, in which the output of the operational amp and the first line are connected to a filter.

12. The circuit of claim 11, in which the filter comprises a capacitor.

13. A method of measuring an electrochemical reaction of an electrochemical cell having first and second electrodes with a circuit having a first input connected to a voltage source, a second input connected to the first electrode and a feedback coupled to an output of the circuit, and which output of the circuit is connected to a processor, the method comprising:

applying a test voltage to the first electrode and connecting the second electrode to ground;

uncoupling the first electrode from the output of the circuit while allowing electrical communication from the first electrode to the processor; and

coupling the first electrode to the output to measure a test current generated in the electrochemical cell without an uncompensated voltage drop.

14. The method of claim 13, in which the uncoupling comprises activating a shut down control circuit of an operational amplifier so that an open circuit can be created for a first pre-determined time interval between a working electrode and a reference electrode.

15. The method of claim 14, in which the coupling comprises de-activating the shut down control circuit of the operational amplifier so that a test voltage can be applied for a second pre-determined time interval between the working electrode and the reference electrode.

16. The method of claim 15, further comprising

measuring a magnitude of a test current value during the second pre-determined time interval;

and

correlating the test current value to an analyte concentration.

17. The method of claim 16, in which the measuring comprises converting the magnitude of the test current into a proportional voltage value.

18. The method of claim 17 further comprising an initial step of

detecting a presence of a physiological sample disposed on the working electrode and the reference electrode.

19. The method of claim 13, in which the applying comprises supplying a voltage of about zero volts and about +3 volts to the operational amplifier.

20. The method of claim 13, in which the applying comprises supplying a voltage of about −

3 volts and about +3 volts to the operational amplifier.