The aim of this paper is to estimate the limitations of parametric faults testing in analog circuits result from fault-driven instability. The linear fractional transformation (LFT) and structured singular value (SSV), the analysis methods from robust control theory, are employed to investigate which parameter could lead to instability of a circuit under test (CUT), and to quantify the deviation in component parameter value that will cause instability. The leapfrog filter is studied as CUT. The SSV based analysis procedure is applied to a Simulink model, which is realized as LFT...
The main objective of the metrological confirmation of industrial measurement systems, which is a reduction of probability of products or production processes qualification errors, is presented. The evolution of the standardization guidance, including the latest editions of International Standards ISO 9000:2000 and ISO 10012:2003 is described. The question why the system of periodic calibrations is essential but not satisfactory procedure to obtain complete metrological confirmation is explained.
This paper describes the procedures developed in the Laboratory for Ship and Marine Hydrodynamics (LSMH) of NTUA to test large models of ships at sea. It is common practice in experimental ship hydrodynamics to test scaled ship models in Towing Tank facilities, to investigate their performance in calm water and in waves. However, it is both time-consuming and very expensive to generate conditions, which simulate properly the actual sea environment. Parameters of the environment such as the incident wave angle, the short-crested nature of the waves encountered in real world, the effect of the...
For the design of smart sensors and measuring systems the information flow of measurement systems is of increasing importance. Therefore the maximum information flow of some systems and especially of some measuring systems with self-calibration is examined. The special information flow problems of self-calibration are regarded.
The traceability chain of the Primary Electromagnetic Laboratory (PEL) is presented, and the place of the resistance standard of 100 MΩ is analysed in details, as well as its construction and characteristics. Its one hundred 1-MΩ elements in parallel connection forms the 10-kΩ value, and can be easily compared to the reference 10 kΩ standard of PEL; in that way its long-term drift was found to be ≈ 0,067 ppm/day (ppm means parts per million). Furthermore, the method of comparison of 100 MΩ resistance standard by means of 100 pF capacitance standard and high-resolution digital voltmeters...
The past calibrations of the reference resistance standards of the Primary Electromagnetic Laboratory (PEL), the Leeds&Northrup (L&N) 1 Ω and 10 kΩ standards, carried out over a period of more than thirty years, have been analysed. The least-squares fitting was used and the regression coefficients of up to the 3 rd order polynomial were calculated and evaluated, by which their resistances can be predicted for a moment of interest. Both standards have been maintaining into the self-developed oil ultrathermostat, where a stable temperature of 23 °C is maintained by the computer-based regulator...
At IEN, a guarded switching system for automatic selection of high value resistors under calibration was developed and metrologically characterized. By means of this system it is possible to select and connect to the measurement system high value resistors in three terminals configuration. As a matter of fact, its guard system allows to reduce the effects due to all the dispersion currents, due to insulation resistances between the resistors under calibration and their shields and due to the switching and connection system (such as insulation resistances among connections, of cables and...
Primary electromagnetic laboratory in Zagreb maintains standards of four major electromagnetic units: volt, farad, ohm and second. Reference standards are periodically calibrated in PTB (Germany) and several methods has been realized for internal laboratory traceability check. RC-comparison method uses Hamon divider constructed of 100 equally balanced 1-megaohm resistors that connected in parallel or serially exhibit Hamon ratio of 100 MΩ : 10 kΩ with relative uncertainty of 10 -8 . Hamon resistance of 100 MΩ is directly compared with impedance of 100 pF capacitance reference at frequency of...
Partial Discharges calibrator principles and microprocessor controlled calibrator design are discussed. The calibrator charge generation technique is classic electrical with storing capacitor. The microprocessor control of the calibrator is perspective because of easy calibrator parameters modification and remote control.
The demands of statistical investigations in measurements inspired the remarkable development of probabilistic methods. However, the probability theory didn’t prove to be fully adequate for all types of uncertainty. Probability theory is excellent if the ambiguity is to be modelled, but its attempts to describe vagueness is quite inconsistent with common sense. Fuzzy theorists have often argued that a major motive behind the theory of fuzzy sets has been the treatment of uncertainty. In particular way, it’s well accepted that a measurement result (no matter what kind of instruments we are...