Metrology and Measurement Systems

The paper is a review of analog and digital electronics dedicated to monitor nanosecond pulses. Choosing the optimal peak detector construction depends on many factors for example precision, complexity, or costs. The work shows some virtues and limitations of selected peak detection methods, for example standard peak detector with rectifier, sample and hold circuit with triggering units and ADC fast acquisition. However, the main attention is paid to problems of results from effective triggering signal for sample and hold operation. The obtained results allow for designing a peak detector construction as an alternative for costly and very complex fast acquisition systems based on ADC and FPGA technologies.

In the framework of non-destructive evaluation (NDE), an accurate and precise characterization of defects is fundamental. This paper proposes a novel method for characterization of partial detachment of thermal barrier coatings from metallic surfaces, using the long pulsed thermography (LPT). There exist many applications, in which the LPT technique provides clear and intelligible thermograms. The introduced method comprises a series of post-processing operations of the thermal images. The purpose is to improve the linear fit of the cooling stage of the surface under investigation in the logarithmic scale. To this end, additional fit parameters are introduced. Such parameters, defined as damage classifiers, are represented as image maps, allowing for a straightforward localization of the defects. The defect size information provided by each classifier is, then, obtained by means of an automatic segmentation of the images. The main advantages of the proposed technique are the automaticity (due to the image segmentation procedures) and relatively limited uncertainties in the estimation of the defect size.

In this paper both envelope approach and morphological filters for characterisation of surface textures were proposed, applied and thoroughly examined. Obtained results were compared with those received after appliance of commonly-used algorithms. The effect of appliance of proposed procedures on surface topography parameters (from ISO 25178 standard) was taken into consideration. The following types of surface textureswere assessed: two-process plateau-honed cylinder liners, plateau-honed cylinder liners with additionally burnished dimples, turned piston skirts, grinded and/or isotropic topographies. It was assumed that envelope characteristics (envelope filtration) can provide results useful for assessments of deep and/or wide oil-reservoirs especially when they are edge located. Moreover, some near-valley areas of surface texture details can be less distorted when envelope filtering is accomplished. It was also found that closing and/or opening envelope filtration can be valuable for reduction of some surface topography measurement errors.

The paper reports experimental results of the analysis of the 145Cr6 steel surface after erosion using the profilometrical technique by means of interferometry streaks. Erosive tests were carried out using abrasive containing quartz sand used in water jet cutting. Differences in the intensity of erosive wear were dependent on the angle of the abrasive stream (10◦ ; 15◦ ; 20◦ ; 30◦ ; 60◦ ; 90◦). In order to determine the characteristic features of the surface layer after the impact of the erosive stream, its characteristic parameters, such as roughness Ra and Sa for linear and field measurements, were analysed. Geometrical features of the regions investigated, such as shape, depth, angle of the abrasive stream, are presented. The analysis was carried out in two-dimensional (2D) and three-dimensional (3D) coordinate systems.

Due to the skin effect of eddy currents, the depth of cracks which can be detected by the traditional eddy current probe is very limited. In order to improve the ability of eddy current probes to inspect deep cracks in metal thick-walled structures, a new eddy current probe using an excitation system with phase shifted fields was proposed. Its feasibility for detecting deep cracks was verified by simulation and experiments. The results showed that the penetration depth of eddy currents in austenitic stainless steel is effectively enhanced by using the new probe.

A π-phase-shifted fiber Bragg grating (π-FBG) shows high sensitivity to the ultrasonic (US) wave as compared to the conventional FBG due to the strong slow-light phenomenon at the resonance peak. However, its sensitivity is limited by the interrogation schemes. A combination of π-FBG and unbalanced fiber Mach– Zehnder interferometer (F-MZI) are theoretically analyzed and optimized for the highly sensitive acoustic sensor. The coupled-mode theory (CMT) and transfer matrix method (TMM) are used to establish the numerical modelling of π-FBG. For the optimized grating parameters of π-FBG, the proposed sensing system shows the high strain sensitivity of 1.2 × 108/ε, the highest dynamic strain resolution of 4.1fε/√Hz, and the highest wavelength shift resolution of 4.9 × 10−9 pm. Further, the proposed sensing system strongly supports both time andwavelength division multiplexing techniques. Therefore, the proposed sensing system shows extreme importance in single as well as quasi-distributed US acoustic wave sensing networks.

Recently, transition metal oxides, which exhibit favorable catalytic abilities, have also been investigated as a material for the detection of hydrazine (N2H4). It has been reported that mixed metal oxides usually offer a higher electrochemical activity than binary oxides. In this work, a TiO2–Fe2O3 coupled system is presented as an enhanced material with major applications in electrochemical detectors. The electrochemical behavior of glassy carbon electrodes modified with TiO2–Fe2O3 in the absence and presence of hydrazine was evaluated via cyclic voltammetry (CV). Experimental results also suggest that the formation of the TiO2– Fe2O3 coupled system enhances electrochemical catalytic performance in N2H4 detection. The modification TiO2 + 2 mol% Fe2O3 provides good analytical performance of detection (0.13 mM) and quantification limits (0.39 mM). The presented coupled system provides the premise for a suitable material for a stable and sensitive N2H4 sensor.

ISFET (Ion Sensitive Field Effect Transistors) microsensors are widely used for pH measurements as well as analytical and biomedical applications. At the same time, ISFET is a good candidate for testing various materials for their applications in sensitive membranes. For example, hydrogen sensitive carbonaceous films containing Pd nanocrystallites (C–Pd) make this material very interesting for sensor applications. A cost effective silicon technology was selected to fabricate n-channel transistors. The structures were coupled to specially designed double-sided PCB (Printed Circuit Board) holder. The holder enables assembly of the structure as part of an automatic stand. The last step of production of MIS structures was deposition of the C–Pd layer. The C–Pd films were fabricated by the Physical Vapor Deposition (PVD) method in which C60 and palladium acetate were evaporated. Electrical resistance of structures with C–Pd films was measured during their interaction with hydrogen. Finally, a new type of highly sensitive FET hydrogen sensor with C–Pd layer was demonstrated and characterized.

Thiswork presents results of comparative studies of the optical absorption coefficient spectra of ion implanted layers in silicon. Three nondestructive and noncontact techniques were used for this purpose: spectroscopic ellipsometry (SE), modulated free carriers absorption (MFCA) and the photo thermal radiometry (PTR). Results obtained with the ellipsometric method are the proof of correctness of the results obtained with the MFCAandPTRtechniques. These techniques are usually used for investigations of recombination parameters of semiconductors. They are not used for investigations of the optical parameters of semiconductors. Optical absorption coefficient spectra of Fe+ and Ge+ high energy and dose implanted layers in silicon, obtained with the three techniques, are presented and compared.

Assessment of the state of a pulse power supply requires effective and accurate methods to measure and reconstruct the tracking error. This paper proposes a tracking error measurement method for a digital pulse power supply. A de-noising algorithm based on Empirical Mode Decomposition (EMD) is used to analyse the energy of each Intrinsic Mode Function (IMF) component, identify the turning point of energy, and reconstruct the signal to obtain the accurate tracking error. The effectiveness of this EMD method is demonstrated by simulation and actual measurement. Simulation was used to compare the performance of time domain filtering, wavelet threshold de-noising, and the EMD de-noising algorithm. In practical use, the feedback of current on the prototype of the power supply is sampled and analysed as experimental data.

The grid-tied inverter synchronizes with the network on the basis of the instantaneous voltage phase angle. This angle is computed by the so-called synchronization algorithms. During grid disturbances, it is estimated with a certain accuracy, which varies for different disturbances and depends on the choice of algorithm. The tests presented here determine how to make an optimal selection of the synchronization algorithm. The research methods used are modeling, simulation and analysis of the results obtained. One of the most important outcomes is the determination of the root-mean-square sync error and its dynamics denotation. The research conclusions should be of particular interest to designers of distributed energy systems with a large number of inverter energy sources.

The article presents the assumptions, characteristics and description of the implementation of a pilot system for on-line monitoring of partial discharges in heads of the high-voltage cable lines. The main purpose of the implementation was to increase the reliability of cable line heads by equipping them with a system of continuous assessment of technical condition with direct transmission of measurement data and alarms to the SCADA system. In order to achieve the assumed goal, unconventional methods for measuring partial discharges were used, the application of which does not require disconnecting the line from the voltage. The implementation was carried out on an active 110 kV high voltage cable line in the area of activity of one of the Distribution System Operators.