Qualifying watthour meters for use as MAP transport standards

One of the US National Institute of Standards and Technology (NIST) Measurement Assurance Programs (MAP) transfers the watthour using transport meters. A statistical design is used to determine the linear and nonlinear corrections for the response of each meter to varying conditions of voltage, current, temperature, and power factor. The process tests for nonlinearities and interaction terms in the response. The test points are distributed over a design volume and are chosen to determine the statistically significant corrections with the minimum number of measurements. For applications requiring less accuracy, a heuristic for dropping correction terms is given. Of the eight meters characterized, four are described adequately by a linear model, while the other four require a cubic model.<>