In this work, a broad overview in the field of strontium titanate (ST, SrTiO₃)-, barium titanate (BT, BaTiO₃)- and barium strontium titanate (BST, BaSrTiO₃)-based gas sensors is presented and discussed. The above-mentioned materials are characterized by a perovskite structure with long-term stability and therefore are very promising materials for commercial gas-sensing applications. Within the last 20 years, the number of papers where ST, BT and BST materials were tested as gas-sensitive materials has ten times increased and therefore an actual review about them in this field has been expected by readers, who are researchers involved in gas-sensing applications and novel materials investigations, as well as industry research and development center members, who are constantly searching for gas-sensing materials exhibiting high 3S parameters (sensitivity, selectivity and stability) that can be adapted for commercial realizations. Finally, the NO₂-sensing characteristics of the BST-based gas sensors deposited by the authors with the utilization of magnetron sputtering technology are presented.

Measurements of the properties of gas-sensitive materials are a subject of constant research, including continuous developments and improvements of measurement methods and, consequently, measurement set-ups. Preparation of the test set-up is a key aspect of research, and it has a significant impact on the tested sensor. This paper aims to review the current state of the art in the field of gas-sensing measurement and provide overall conclusions of how the different set-ups impact the obtained results.

Controlling environmental pollution is a burning problem for all countries more than ever. Currently, due to the increasing industrialization, the number of days when the limits of air pollutants are over the threshold levels exceeds 80–85% of the year. Therefore, cheap and effective sensors are always welcome. One idea is to combine such solutions with cars and provide real-time information about the current pollution level. However, the environmental conditions are demanding, and thus the developed sensors need to be characterized by the high 3S parameters: sensitivity, stability and selectivity. In this paper, we present the results on the heterostructure of CuO/SnO_x and SnO_x/CuO as a possible approach for selective NO₂ detection. The developed gas sensors exhibited lower operating temperature and high response in the wide range of NO₂ and in a wide range of relative humidity changes. Material characterizations and impedance spectroscopy measurements were also conducted to analyze the chemical and electrical behavior.

The sensitivity of tunneling magnetoresistance sensors is an important performance parameter. It depends on the derivative of resistance versus magnetic field (transfer curve) and the current and is expressed as the product of the two factors. Previous research has demonstrated that the bias voltage has a significant impact on the sensitivity. However, no research has been conducted into the dependence of current and the derivative on bias voltage magnitude and polarity, and their contribution to the sensitivity. Thus, this paper investigates the dependence of sensitivity, derivative of resistance versus magnetic field curve and current on bias voltage magnitude and polarity in CoFeB/MgO/CoFeB-based tunneling magnetoresistance sensors with weak, strong and no voltage-controlled perpendicular magnetic anisotropy modification. It demonstrates that the sensitivity dependence on bias voltage for sensors with voltage controlled magnetic anisotropy modification showed no saturation up to 1 V. Moreover, the sensitivity asymmetry with respect to bias polarity changed significantly with bias, reaching a ratio of 6.7. Importantly, the contribution of current and the derivative of resistance versus magnetic field curve to the sensitivity showed a crossover. The current dominated the bias dependence of sensitivity below the crossover voltage and the derivative above the voltage. Furthermore, the crossover voltage in sensors without voltage controlled magnetic anisotropy modification did not depend on polarity, whereas in sensors with voltage controlled magnetic anisotropy modification, it appeared at significantly higher voltage under positive than negative polarity.

Power transformers are one from more important and the most expensive elements of the AC electric power systems. For this reason, their in-service operation and management are usually based on the Condition Based Maintenance (CBM) strategy, which uses diagnostic data obtained by various methods to assess the real condition of supervised objects. The method analyzing the transfer function (TF) of the transformer windings makes it possible to track changes in the electrical and mechanical parameters of the windings due to the occurrence of the various operating stresses (e.g. high current short-circuits). The paper presents analysis regarding the use of wideband, random signals (applied from a pseudo-white noise generator) for determining the transfer function of transformer windings. Particularly, the influence of the basic digital signal processing parameters (e.g. waveforms sampling frequency, data record length and selected window function) on the evaluated characteristics of the transfer function is shown.

Metal-oxide surge arresters (MOSA) used as protective devices in electrical networks undergo during in-service operation aging processes that change their technical parameters. The main in-service stresses are: operating voltage, overvoltages, partial discharges and environmental factors. Exposures that result in the dissipation of electrical energy in the varistor structure cause an increase in its temperature and changes of the structure. The paper presents studies on the impact of pulsed electrical stresses, i.e. high-current surges 8/20 and 50 Hz AC bursts on the temperature of low-voltage arresters with metal-oxide varistors. During the tests, temperature contact measurements were made on a metal base of MOSA and registration of thermograms of their surface using a thermal imaging camera. Thermal processes occurring in the tested surge arresters are characterized by long time constants. For this reason, when researching these processes, AC bursts can be a suitable alternative to the use of high currents impulses.