Water flow meter calibration with a master meter method

Master meter method is an efficient way to calibrate flow meters with less time and costs. The master meter method has simpler flow configuration than the gravimetric flow measurement method requires. Maintenance efforts of the master meter method are easier than the gravimetric method. However, the guidelines of master meter method have not been established completely. It is because the notion of relative deviations, which are used as a measure and for comparison calibration, is not clearly understood. On the other hand, the system uncertainty, which is typically used as the calibration and measurement capability of the gravimetric flow standards, are understood very well. In this study, a complete explanation on the master meter method is attempted. First, appropriate calibration conditions are assumed. Second, a suitable calibration procedure is suggested. Third, a mathematical model for the relative deviations is described. Fourth, uncertainty factors of the relative deviations are evaluated. Finally, two examples of the comparison calibration are explained in detail. The master meter method is compatible with the guide to the expression of uncertainty in measurement (GUM, ISO/IEC Guide 98-3:2008). In the examples, it is found that the master meter method can achieve the measurement uncertainty as low as 0.20%.