Patent ID: 6908593

Claim:
A medical diagnostic device for measuring at least one of an analyte centration and a property of a biological fluid, comprising a) a sample inlet for introducing a sample of the biological fluid into the medical diagnostic device; b) a first capillary channel for conveying the sample from the sample inlet to a branching point; c) a capillary connecting channel for conveying a first part of the sample from the branching point through a measurement area, in which is measured a physical parameter of the sample that is related to the at least one of the analyte concentration and property of the biological fluid, and, thereafter, to a first stop junction; d) a capillary bypass channel for conveying a second part of the sample in a first direction from a first region, proximate to the branching point, to an overflow region, distal to the branching point, the first region having a capillary dimension in a second direction substantially perpendicular to the first direction; e) a second stop junction in the capillary bypass channel, comprising a boundary region that i) separates the first region and overflow region, ii) has a second predetermined dimension in the second direction that is greater than the capillary dimension, and iii) is triangular in shape with two legs that define an angle of less than 90 degrees that points toward the first region, whereby excess sample that enters the sample inlet will pass through the second stop junction into the overflow region; and wherein the second stop junction impedes sample flow into the overflow region while the first part of the sample is being conveyed through the measurement area and the second stop junction is weaker than the first stop junction such that the excess sample passes through the second stop junction into the overflow region only after sample has filled the measurement area.