The Effect of the Imperfect Realization of the Artificial Mains Network Impedance on the Reproducibility of Conducted Emission Measurements

Closed form formulas are derived permitting to evaluate the non-reproducibility of conducted emission measurements due to the imperfect realization of the artificial mains network impedance. Since this is the dominant contribution to the combined standard measurement instrumentation uncertainty, the availability of such formulas permits to tailor the uncertainty value to the actual measurement capability of testing laboratories. Further, analytical formulas provide guidance both to the technical committees involved in the standardization process, when they set tolerances on the complex impedance of coupling/decoupling networks, and to the manufacturers of instrumentation, since they have to optimize the design of the networks in order to comply with the standards specifications. The non-reproducibility error is quantified in terms of its expected value and standard uncertainty. A simple and reasonably accurate approximation of its probability density function is also obtained. A comparison with the material reported in the relevant international standards is offered in order to highlight the common and the innovative aspects of the results derived here.