An analysis system for determining an analyte of a body fluid comprises a test element and an analysis instrument having a measurement and evaluation unit. The test element has a sample application zone and two analysis zones and a reagent system, whose reaction with the analyte results in a detectable change characteristic for the desired analytical result. The measurement and evaluation unit comprises two analog measuring units, in each of which an analog measurement signal corresponding to one of the analysis zones is generated, two analog-digital converters for digitizing the analog measurement signal, a comparator unit for comparing control data values based on the digitized measurement signals, and a final processing unit, in which, if the determined deviation between the control data values of the digitized measurement signals is less than a predefined value, at least one of the control data values is allowed to pass for further processing into the desired analytical result.