OIML Guide 20 states that the key elements of metrological quality control for utility meters are initial verification, followed by subsequent verification at periodic intervals.
Focusing on subsequent verification, the PTB has developed a procedure that guarantees with high confidence that 95 % of the measuring instruments fulfil conformance standards at all times. This procedure exceeds the scope of OIML Guide 20, current practices and former German regulations that merely guarantee that measuring instruments fulfil conform ance standards at the time of inspection.
The procedure developed by the PTB consists of two complementary statistical methods that combine standard statistical sampling methods with the assumption of a linear decrease in the number of conforming meters over time. Without further know - ledge, standard sampling plans need to be applied to reliability levels higher than 95 % due to the linear transformation. The second of the two statistical methods permits application of the more efficient sampling plans contained in OIML Guide 20 (which ensure 92 % reliability), when more stringent conditions are tested and additional criteria are fulfilled.
This procedure will be enforced in Germany beginning in 2019. As a result, the level of consumer protection in utility billing will increase.
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Themenbereich der Metrologie
Mathematik und metrologische Informationstechnik
Zitierung
Klauenberg, K. & Elster, C. (2018). How to ensure the future quality of utility meters. OIML Bulletin, 59(3), 16–23.
