Patent ID: 7122110

Claim:
An electrochemical test sensor for detecting the concentration of an analyte in a fluid test sample, the test sensor comprising: (1) a non-conductive base which provides a flow path for the fluid test sample, the base having a front edge, and a counter electrode and a working electrode on an upper surface thereof, the counter and working electrodes being adapted to be in electrical communication with a detector of electrical current; (2) a reaction layer on at least the surface of the working electrode the reaction layer comprising an enzyme which reacts with the analyte to produce electrons which are transferred to the working electrode; and (3) a cover coupled with the base and forming a capillary space with an opening for the introduction of fluid test sample thereto, the space containing a flow path for the fluid test sample, a major portion of the counter electrode being located downstream relative to the opening and at least a portion of the working electrode, and wherein a sub-element of the counter electrode is located upstream from the working electrode such that when electrochemical communication occurs between only the sub-element of the counter electrode and the working electrode there is insufficient flow of electrical current through the detector to constitute a valid test for determining the concentration of the analyte in the fluid test sample, the sub-element of the counter electrode being located on the upper surface of the base and being flush with the front edge of the base.