Claims
- 1. An electrochemical sensor for detecting the concentration of analyte in a fluid test sample which comprises: 1) a base which provides a flow path for the fluid test sample having on its surface a counter electrode and a working electrode in electrical communication with a detector of electrical current; 2) a reaction layer on the surface of at least the working electrode comprising an enzyme which reacts with the analyte to produce electrons that are transferred to the working electrode; and 3) a cover which when mated with the base member forms a capillary space with an opening for the introduction of fluid test sample thereto which space contains the flow path for the fluid test sample in which the counter and working electrodes are situated so that the major portion of the counter electrode is located downstream of the opening from the working electrode with a sub-element of the counter electrode being upstream of the working electrode so that when electrical communication between only the sub-element and working electrode takes place there is insufficient flow of electrical current through the detector to constitute a valid test for the concentration of analyte in the fluid test sample and the detector is pre-programmed to emit an error signal in the event of such insufficient flow of electrical current.
- 2. The sensor of claim 1 wherein the counter electrode and the sub-element are physically connected.
- 3. The sensor of claim 1 wherein the cover is made of a deformable material which is deformed to provide a concave area in the central portion thereof such that when the cover is mated with the base member the cover and the base member form the capillary space with the opening therein.
- 4. The sensor of claim 1 wherein the opening to the capillary space is solely through the cover or the base member.
- 5. The sensor of claim 4 wherein the opening is solely through the cover.
- 6. The sensor of claim 1 wherein the base and cover are configured to form the opening when they are mated.
- 7. The sensor of claim 6 wherein there is a U shaped member between the cover and the base, so that the opening is formed by mating the cover and base with the U shaped member therebetween.
- 8. The sensor of claim 6 wherein the cover is concave and the opening is formed by mating the based with the concave cover.
- 9. The sensor of claim 1 wherein the enzyme in the reaction layer is combined with a hydrophilic polymer.
- 10. The sensor of claim 1 wherein the enzyme is glucose oxidase.
- 11. The sensor of claim 1 wherein a major portion of the working electrode is covered by a dielectric material leaving a minor portion of it exposed to the test fluid and the major portion of the counter electrode is located downstream (in terms of the direction of fluid flow along the flow path) from the exposed portion of the working electrode.
- 12. The sensor of claim 1 wherein the sub-element of the counter electrode is not physically connected to the main element of the reference electrode and the sub-element is connected to the detector by its own connecting element.
- 13. The sensor of claim 1 wherein the reaction layer is also on the surface of the counter electrode.
- 14. A system for detecting the concentration of analyte in a fluid test sample which comprises the sensor of claim 1 in electrical connection with a meter which has been algorithmically programmed to a) make multiple current measurements at different time periods when a driving potential is applied between the electrodes, b) convert the multiple current measurements into error checking parameters and c) check the values of these parameters against their corresponding tolerance bands to determine if a short fill has occurred.
- 15. The system of claim 14 wherein the analyte is glucose the system is programmed to apply a 0.4V potential for 10 seconds after the fluid test is applied, open the circuit (0V potential) for 10 seconds and apply a 0.4V potential for 10 seconds and,
A) making a current measurement at the end of the first 10 second period which is designated as Ir10, 5 seconds into the third 10 second period designated as Ir5 and at the end of the third 10 second period designated as Ir10, B) determining the decay factor which describes the shape of the current time course by solving the equation: 3k=ln(Ir5)-ln(Ir10)ln(10)-ln(5) and the Read-to-Burn ratio, (R/B) by solving the equation:R/B=Ir10/Ib10C) checking the values against their tolerance limits for K as:if |k−(ak1+bk1·G)|>wk is true when G≦dk1, orif |k−(ak2+bk2·G)|>wk is true when dk1<G≦dk2, orif |k−(ak3+bk3·G)|>wk is true when G>dk2 where ak1, ak2, ak3, bk1, bk2, bk3, wk, dk1, dk2 and dk3 are predetermined constants, G is the glucose measurement. And for R/B as: Condition 2 (R/B ratio checking).if |R/B−(ac1+bc1·G)|>wc is true when G≦dc, orif |R/B−(ac2+bc2·G)|>wc is true when G>dc where ac1, ac2, bc1, bc2, wc, and dc are predetermined constants, G is the glucose measurement, and D) concluding that there has been a short fill if either Condition 1 or Condition 2 is true.
Parent Case Info
[0001] This is a Divisional application of co-pending application Ser. No. 09/861,437 which in turn is a Continuation-In-Part of application Ser. No. 09/731,943 filed Dec. 8, 2000, now U.S. Pat. No. 6,531,040 B2, which is in turn a Continuation-In-Part of application Ser. No. 09/366,269, filed on Aug. 2, 1999, now abandoned.
Divisions (1)
|
Number |
Date |
Country |
Parent |
09861437 |
May 2001 |
US |
Child |
10864011 |
Jun 2004 |
US |
Continuation in Parts (2)
|
Number |
Date |
Country |
Parent |
09731943 |
Dec 2000 |
US |
Child |
09861437 |
May 2001 |
US |
Parent |
09366269 |
Aug 1999 |
US |
Child |
09731943 |
Dec 2000 |
US |