The paper presents a method for digital compensation of the ratio and phase angle errors of a resistive voltage divider. The system consists of a separate electrical circuit of a resistive divider, and a digital compensation system based on National Instruments (NI) PCI eXtension for Instrumentation (PXI) PXI-5922 digital acquisition cards (DAQ). A novel approach to the real-time compensation is presented, using digital signal processing. The algorithm is based on Wiener filtering and finite-impulse-response (FIR) filters. The proposed digital compensation, using FIR digital filtration and NI PXI DAQs, gives maximum magnitude error below 400 ppm and the phase angle error below 4500 μrad, in the frequency band 50 Hz–100 kHz. The algorithm allows the fine-tuning of the compensation to adjust to the possible change in the original transfer function due to the aging of the components.

AC current shunts are used for precise current measurements. The application of AC current shunts requires that their amplitude phase characteristics are known. A group of three geometrically identical current shunts and a reference shunt are observed in this paper. The phase characteristics of the reference shunt have been previously obtained. A relative phase comparison has been made between the three geometrically identical shunts, and phase displacement values for each have been obtained. After this, the results are verified with the reference shunt. The relative method is most suitable for shunts, where their respective RC and L/R values are small (compared with 1/ω) and of the same order. The ratios of the nominal resistance values of the shunts used in this paper are at the limit of the given statement. The conclusion is that the method applied at the mentioned limits, in terms of the metrology-grade phase angle determination of current shunts, is not to be considered reliable at frequencies higher than 1 kHz.

Direct-current transformers (DCCTs) rely on small toroidal cores made of soft magnetic materials with high permeability, whose magnetic properties affect the sensitivity and linearity of the sensor. Reliable characterization of such small cores and of the resulting sensor component requires measurements with stated uncertainties, which are rarely reported together. This paper applies and integrates established measurement methods, namely, dynamic hysteresis loop measurements on ring specimens and dc current detection from the asymmetry of the saturation current peaks, into a laboratory test setup for the characterization of DCCT sensor components. Permalloy and nanocrystalline toroidal cores are characterized at 50 Hz. The nanocrystalline cores exhibit a maximum relative permeability of approximately 300 × 10³ and a coercivity of approximately 1.1 A/m, compared with approximately 100 × 10³ and 4.2–4.9 A/m for the permalloy cores. The sensor component with the tested core is calibrated against a reference current shunt for both current polarities, showing a linearity error of 0.59% FS in the range from −4 A to +4 A. The expanded uncertainty of the reference current measurement is ± 926 µA/A according to the GUM and ±906 µA/A using the Monte Carlo method (k = 2). The results show that the tested nanocrystalline cores are better suited for sensitive dc current detection and provide a basis for core selection and DCCT design.