Measurement of substances in liquids

Abstract

In accordance with the present invention a measuring device compares the current generated by two working sensor active areas and gives an error indication if they are too dissimilar, i.e., the current at one sensor active area differs too greatly from what would be expected from considering the current at the other. Not only can this method detect when one of the sensor parts has not been properly covered with sample liquid, but it can also detect if there is a manufacturing defect in either sensor part or if either has been damaged after manufacture, since even with complete coverage of the working sensor parts, an anomalous current will be generated at the affected sensor part under such circumstances.

1 - 16 . (canceled)  
     
     
         17 . A disposable test strip for measuring the concentration of a substance in a sample liquid; said device comprising: 
 a first working sensor active area for generating charge carriers in proportion to the concentration of said substance in the sample liquid, said first working sensor active area being electrically contiguous;    a second working sensor active area downstream from said first working sensor active area also generating charge carriers in proportion to the concentration of said substance in the sample liquid, said second working sensor active area being electrically contiguous, wherein said first and second working sensor active areas are arranged such that, in the absence of an error condition, the quantity of said charge carriers generated by said first working sensor active area are substantially identical to the quantity of said charge carriers generated by said second working sensor active area; and    a reference sensor upstream from said first and second working sensor active areas which reference sensor is a common reference for both the first and second working sensor active areas, said reference sensor and said first and second working sensor parts being arranged such that the sample liquid is constrained to flow substantially unidirectionally across said reference sensor and said first and second working sensor active areas;    
     
     
         18 . The disposable test strip claimed in  claim 17  arranged such that the sample liquid is constrained to flow substantially unidirectionally.  
     
     
         19 . The disposable test strip claimed in  claim 17  wherein said working sensor active areas are both provided downstream of the reference sensor part.  
     
     
         20 . The disposable test strip claimed in  claim 17  wherein said working sensor active areas are provided downstream of one another.  
     
     
         21 . The disposable test strip claimed in  claim 17  wherein said working sensor active areas are both provided downstream of the reference sensor.  
     
     
         22 . The disposable test strip claimed in  claim 17  wherein said working sensor active areas are substantially equal.  
     
     
         23 . The disposable test strip claimed in  claim 17  arranged to measure said currents after a predetermined time following application of the sample.  
     
     
         24 . The disposable test strip claimed in  claim 17  wherein the substance to be measured is glucose, and each of the working sensor parts generates charge carriers in proportion to the concentration of glucose in the sample liquid wherein.  
     
     
         25 . A disposable test strip for measuring the concentration of a substance in a sample liquid comprising: 
 a base member;    two working sensor active areas provided on the base member a first of said working sensor active areas being arranged upstream of a second of said working sensor active areas; and    a reference sensor upstream from said working sensor active areas which is a common reference for each working sensor active area, each working sensor active area being arranged in use to generate charge carriers in proportion to the concentration of said substance in the sample liquid wherein said two working sensor active areas are arranged such that, in the absence of an error condition, the quantity of said charge carriers generated by a first of said working sensor active areas are substantially identical to the quantity of said charge carriers generated by a second of said working sensor active areas, arranged such that the sample liquid is constrained to flow substantially unidirectionally across said reference electrode and said working sensor active areas.    
     
     
         26 . The disposable test strip as claimed in  claim 25  arranged such that the sample liquid is constrained to flow substantially unidirectionally across said working sensor active areas.  
     
     
         27 . The disposable test strip as claimed in  claim 25  wherein said working sensor active areas are provided one downstream of the other.  
     
     
         28 . The disposable test strip as claimed in  claim 26  wherein said working sensor active areas are both provided downstream of said reference sensor part.  
     
     
         29 . The disposable test strip as claimed in  claim 26  wherein said working sensor active areas each have the same area.  
     
     
         30 . The disposable test strip as claimed in  claim 28  wherein said working sensor active areas are substantially identical.  
     
     
         31 . The disposable test strip as claimed in  claim 26  wherein the substance to be measured is glucose, and each of the working sensor active areas generates charge carriers in proportion to the concentration of glucose in the sample liquid.