CAPACITANCE DETECTION IN ELECTROCHEMICAL ASSAY WITH IMPROVED RESPONSE

• US 20110309846A1
• Filed: 08/11/2011
• Published: 12/22/2011
• Est. Priority Date: 02/25/2010
• Status: Active Grant

• Current Assignee: Cilag Gmbh International (Johnson & Johnson)
• Original Assignee: LifeScan Scotland Limited (Johnson & Johnson)
• Inventors: ELDER, David, Dilleen, John
• Granted Patent: US 8,742,773 B2
• Time in Patent Office: Days
• US Class Current: 324/683
• CPC Class Codes: G01N 27/22 by investigating capacitance
• CPC Class Codes: G01N 27/3274 Corrective measures, e.g. error detection, compensation for temperature or hematocrit, calibration coding of calibration information G01N33/48771

Abstract

Methods and systems are provided to determine capacitance of the electrochemical test cell.

Claims

11-1. The method of claim 11, in which the percentage comprises a range from about 5% to about 30% of the first sampling-time interval.

17. A method to evaluate a condition of an electrochemical test strip having at least two electrodes disposed in a test cell and connected to corresponding connectors, the method comprising:

depositing a fluid sample in the electrochemical test cell;

applying an oscillating signal of a predetermined frequency to the fluid sample in the electrochemical test cell;

measuring an amplitude of the output signal from the electrochemical test cell;

determining a phase angle between the output signal and the oscillating signal from the electrochemical test cell;

establishing a resistance of the test cell with the total impedance and a predetermined resistance between the test cell and one of the connectors;

quantifying a capacitance for the electrochemical test cell based on the resistance of the test cell and an impedance of the test cell;

annunciating an error whenever at least one of (a) the measured resistance of the test cell is outside a resistance range or (b) the quantified capacitance of the electrochemical test cell is outside a capacitance range.

18. The method of claim 17, in which the resistance range comprises from about zero ohms to about 100,000 ohms.

19. The method of claim 18, in which the capacitance range comprises from about 410 nanoFarads to about 450 nanoFarads.

20. The method of claim 18, in which the capacitance range comprises from about 590 nanoFarads to about 630 nanoFarads.

21. The method of claim 18, in which the predetermined resistance comprises a value selected from a range of about zero ohms to about 200 ohms.

22. The method of claim 18 in which the predetermined resistance is selected from a range of values of about zero ohms, about 50 ohms, about 100 ohms, about 150 ohms, about 200 ohms, the resistance range comprises from about zero ohms to about 100,000 ohms, and the capacitance range comprises from about 410 nanoFarads to about 630 nanoFarads.

23. The method of claim 17, in which the establishing comprises:

ascertaining a total impedance of the test cell from the phase angle;

arriving at a resistance of the test cell with the predetermined resistance.

24. The method of claim 23, in which the quantifying comprises extracting the complex impedance from the ascertaining and arriving.

25. The method of claim 24, in which the extracting comprises calculating a new phase angle without the predetermined resistance.

26. The method of claim 25, in which the calculating comprises transforming the new phase angle into a capacitive reactance.

27. The method of claim 26, in which the capacitance of the test cell is related to the capacitive reactance by a product of the ratio of a circle'"'"'s circumference to its diameter and the predetermined frequency.

28. The method of one of claim 17 or claim 27, in which the predetermined resistance range comprises a range from about zero ohms to about 120,000 ohms and the predetermined capacitance range comprises a range from about 500 nanoFarads to about 650 nanoFarads.

29. A system to evaluate a condition of an electrochemical test strip, the system comprising:

a test strip comprising;

at least two electrodes having respective electrode ends disposed in a test cell; and

at least two connectors coupled to the respective at least two electrodes such that a strip electrical resistance is established between at least one of the connectors and the electrodes; and

a microcontroller connected to a strip port connector having at least two terminals that connect to respective connectors of the test strip, the microcontroller configured to supply an oscillating signal to the chamber via the at least two electrodes, measure capacitive and resistive responses from the test cell based on a phase angle response of the test cell and the strip electrical resistance, and designate a test strip as defective whenever the capacitive and resistive responses are outside of a range of capacitance of the test cell with respect to a range of resistance of the test cell.

30. The system of claim 29, in which the resistance range comprises from about zero ohms to about 100,000 ohms.

31. The system of claim 29, in which the capacitance range comprises from about 410 nanoFarads to about 450 nanoFarads.

32. The system of claim 29, in which the capacitance range comprises from about 590 nanoFarads to about 630 nanoFarads.

33. The system of claim 29, in which the predetermined resistance is a value selected from a range of about zero ohms to about 200 ohms.

34. The system of claim 29, in which the predetermined resistance is selected from any value of about zero ohms to about 200 ohms, in which the resistance range comprises from about zero ohms to about 100,000 ohms, and in which the capacitance range comprises from about 410 nanoFarads to about 630 nanoFarads.