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The paper describes the design and mathematical model of a 50 mA coaxial current shunt developed at Silesian University of Technology (SUT) in Gliwice, Poland. The AC-DC transfer difference of the shunt transimpedance and its phase displacement were calculated based on the mathematical model of the shunt. The results of AC-DC transfer difference calculation were validated by calibration of the shunt at Swedish National Metrology Institute RiSE.

The hardware idea and experimental studies of a two-phase source of digitally synthesized sinusoidal voltage (DSS) intended for use in primary impedance metrology is described in the paper. The source is especially dedicated for fully-digital impedance bridges that can measure impedances across the whole complex plane of the impedance. The scope of the work covers description of the DSS, determination of its parameters that affect its applicability in sampling impedance bridges, i.e.: amplitude and phase stability of generated sine waves, impact of the source on the temperature changes, resolution, linearity and spectral purity.

One of the most precise standards of AC voltage in the frequency range from 1 MHz to 100 MHz is the Calorimetric Thermal Voltage Converter (CTVC) designed at National Research Council (NRC) in Ottawa, Canada. Unfortunately, this converter has a few times higher value of DC reversal error than other known thermal voltage converters (TVC). This article presents analysis of possible reasons of such a high DC reversal error and discusses possible ways of its reduction. The analysis is performed using finite element method (FEM) simulations. The correctness of the developed FEM model was validated with published results of investigation of the physical model of the CTVC designed and constructed in NRC. This article presents also improved construction of a CTVC and laboratory measurements of its DC reversal error which is about 89% lower than in the case of NRC CTVC.

A method for checking impedance comparison bridges, based on metrological triangles is presented in the paper. It is proved that, both in differential and ratio comparison circuits, it is possible to assess the consistency (and thus accuracy) of measurement basing on intercomparison of groups composed of at least three standards of unknown but stable values. In this paper the consistency level is defined. The triangle method was applied at various stages of construction of differential and ratio bridges. The method enabled us to detect and remove systematic errors in 1:1 bridge circuits and finally confirmed the accuracy assessed during construction of the bridges.