Power quality assessment is a complex measurement task, requiring the usage of a system with suitable metrological properties. This complex measurement task in the real power grid is performed with the use of power quality analysers that measure and record the parameters determining the power quality. The paper presents selected research results for a class A power quality analyser in the specially prepared measurement system containing measuring instruments calibrated by the Main Office of Measures. The measurement results were completed with a presentation of the uncertainty budget. The influence of the phenomenon of spectrum leakage on metrological properties of the tested power quality analyser was considered in the paper. To assess this influence, the simulation studies with the use of MATLAB and the experimental studies were carried out for selected test signals. The Metrological interpretation of the research results is presented in the paper.

This paper discusses the issue of the self-heating effect of resistance sensors during temperature measurement. The self-heating effect causes temperature measurement errors. The aim of this work was to develop a method for in situ assessment of the thermal resistance between a self-heating thermometer and its surrounding environment, the temperature of which is measured. The proposed method is used to assess the uncertainty resulting from the heat transfer from the thermometer to the surrounding environment, which allows increased measurement accuracy. The proposed method consists of experimental determination of the sensor’s temperature characteristics in relation to the heating power for different values of the measuring current. Sample measurements were carried out on a representative group of resistance temperature sensors. The relationship of the internal thermal resistance to the type of sensor design and the relationship of the external resistance to the ambient conditions were demonstrated. The developed method allows the appropriate measuring current of the resistance temperature sensor to be selected according to its design, the mounting method, and the environmental conditions, which ensures that measurement errors are maintained at an appropriately low level.

The paper presents a possible application of integrated LabVIEW environment to the final evaluation of measurement results in direct measurement. The possibilities of presenting and visualizing the uncertainty of measurement results in a convenient and user-friendly form are also discussed. The topics discussed in the paper were presented using a developed application in LabVIEW. The paper discusses the topic of measurement of direct voltages in the presence of strong electromagnetic interferences. These problems are frequently omitted or hardly emphasized. It presents a suitable measuring system, a virtual measuring instrument created in the LabVIEW environment, and the results of tests carried out for an example NI PCI-6221 data acquisition board. The described approach can be applied also in other measurement situations.

For newly developed measuring systems, it is easy to estimate type-B uncertainties based on technical data from the measuring modules applied. However, it is difficult to estimate A-type uncertainties due to the unknown type and level of interferences infiltrating the measuring system. This is a particularly important problem for measurements carried out in the presence of typical of power grid disturbances. The aim of the research was to develop a method and a measurement stand for experimental assessment of uncertainties in a measuring system that makes use of data acquisition modules containing analog-to-digital converters (ADCs). The paper describes, in detail, the design of a completed test stand. It presents an original application in the LabVIEW environment, which enables testing the dependence of the uncertainties with the quantity of the measurements averaged in a series, for different kinds and levels of interferences infiltrating the measuring path. The results of tests for several popular measuring modules are presented. An analysis of the determined uncertainties was carried out in relation to the parameters of the tested measurement modules and for various levels of interferences. It is proved that an increase in the number of averaged measurements to approx. 100–200 always results in a decrease in uncertainty for each tested module and under all conditions. However, a further increase in the quantity of measurements, even up to 1000 averaged measurements, proved reasonable only for high-accuracy modules, in particular with a high level of interferences. An excessive increase in the quantity of averaged measurements proved a low effect for modules characterised by a low resolution and with a low level of interferences. The measurement results also proved that when estimated, uncertainties in the interference probability distribution are significant, especially if they deviate from normal distribution.

W niniejszej publikacji przedstawiono podstawowe metody pomiaru częstotliwości. W pracy autorzy ograniczyli się do cyfrowych metod pomiaru tej wielkości. Omówiono metody pomiarowe z wykorzystaniem mikrokontrolerów. Przedstawiono stanowisko pomiarowe, wraz z opisem, bazujące na mikrokontrolerze ATmega 16. Przedstawiono wykorzystanie opracowanego układu pomiarowego do pomiaru odległości z wykorzystaniem sondy ultradźwiękowej. Pomiar częstotliwości odbywał się z wykorzystaniem trybu przechwytywania –„capture

The indirect thermographic measurement of the temperature of a semiconductor element consists of two stages. The first involves a thermographic measurement of the case temperature of the semiconductor element. The second involves determining the relationship between the case temperature and the semiconductor element's temperature. This is possible based on simulation studies using the finite element method (FEM). This type of measurement is subject to a certain level of uncertainty. The measurement uncertainty depends on a number of factors that affect the measurement result, as well as on the probability distributions assigned to them. As a result of the conducted research, the uncertainty value was determined. This uncertainty concerns the indirect thermographic measurement of the semiconductor element's temperature.