Influence of test methods accuracy on conformity assessment of domestic water flow meters

In gravimetric calibration tests for water meters, the mass of water passing through a meter under test (MUT) is generally measured by weighing it on a scale and collecting it in a tank. This mass is then transformed into a volume, which requires determining the water density. The novelty of this study lies in the improvement of the accuracy and uncertainty of measurements during the test conformity assessment of domestic water flow meters. The manual and semi-automatic systems were updated to an automatic system to automatically record the meter reading by converting the number of revolutions of the meter core into frequency and then converting the frequency into liters.

In this study, we tested 16 domestic water meters set up in series within a test rig to evaluate the errors and conduct a conformity assessment. The error rates of the MUT were identified using three different methodologies: manual, semi-automatic, and automatic. We also examined how these methods influenced measurement uncertainties. The findings indicated that the automatic method, which employed a laser, was the most accurate and consistent, significantly improving the efficiency by allowing a larger number of meters to be tested daily. The measurement uncertainty was reduced to 0.25 % with this method compared to 1 % using the manual approach, as it effectively eliminated visual errors often introduced by human oversight. In addition, the automatic method resulted in a smaller standard deviation within a normal distribution than the manual method. This means that the data groups were more closely grouped around the mean, leading to a slightly clearer bell-shaped curve.