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In this work, biochar was introduced as a filler into the aliphatic-aromatic copolyester and polylactide blend. Properties and the changes during degradation of obtained materials were evaluated. A new application path was also determined by lowering the surface resistivity by increasing the biochar content. Measurements of electrostatic properties showed that surface resistivity of the poly(1,4-butylene adipate-co-1,4-butylene terephthalate)/polylactide/biochar composites is strongly dependent on the biochar content. Six-fold reduction of the surface resistivity after introduction of the 30 wt% of carbon to the reference specimen was observed. Degradation tests were conducted under abiotic and composting conditions. Visual evaluation indicated that the increase of biochar content had caused cracks to increase on the sample surfaces. The values of thermal properties after degradation do not indicated on the biochar influence on polymer matrix degradation mechanism. Nuclear magnetic resonance analysis revealed that after 42 days of hydrolytic degradation amount of polylactide was 0–2%.

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.

In this paper some numerical algorithms generating the full invertible matrices and full matrices with a given spectrum are presented.

This paper is focused on the ambient temperature coefficient of the output frequency of thermal piezoacoustic sensors operating in a twin configuration (differential mode). The sources of the ambient temperature coefficient of the sensor are pointed out and the partial temperature coefficients of each block of the measurement chain are analysed with special attention to the influence of the non-linearity and mismatch of the frequency-temperature characteristics of the active and reference sensor. The derived equations are verified experimentally using the model of a thermal r.m.s. converter. A method for the reduction of the ambient temperature coefficient based on the proper choice of resonance frequency of the reference sensor is proposed. The presented analysis is valid for small variations of the ambient temperature, within the range of a few degrees Kelvin.