A method for measuring the amount of fluid contained in a reaction vessel in a clinical analyzer includes the steps of adding a first aliquot of fluid to the reaction vessel and measuring the quantity of fluid contained therein. A second aliquot of fluid is then added to the reaction vessel and the quantity of fluid contained therein is also measured. Measurement of the two fluid quantities can occur with or without removal of the first aliquot in between measurements. In obtaining the two quantity measurements and comparing them against a standard, the effects of well geometry can be minimized. Preferably, a delta or ratio measurement is obtained between the first and second liquid volume measurements which can be compared against a standard so as to normalize apparent volume losses or gains due to reaction well dimensional variation. This approach enhances the analytical capability to detect true fluid delivery errors.