Luka Ferkovic, Josip Butorac
DETERMINATION OF EQUIVALENT PARAMETERS FOR INDUCTANCE STANDARDS

The confidence in self inductance base can be obtained by regular comparisons between particular metrological laboratories and by mutual comparisons of inductance standards within own laboratory. Standard methods of inductance measurements in its applications don't give explicitly all of parameters of standard substitute circuit nor the accuracy which is requested by fundamental principles of inductance standard calibration. In order to ensure the adequate low measurement uncertainty, which suits these requirements, it is necessary to elaborate the procedure of standard calibration.

Giovanni Bucci, Ivano Caschera, Edoardo Fiorucci, Carmine Landi
A SMART POWER QUALITY SENSOR FOR THE EVALUATION OF FLICKER EFFECT

The monitoring of power quality (PQ) on supply networks is today an issue of worldwide interest. In this field, one of the most important parameter is the flicker effect, a phenomenon due to luminance fluctuations of the lighting caused by voltage variations. The IEC standardized the implementation of a flickermeter, to supply information about the human reaction to the voltage amplitude modulation. Starting from a different flicker measurement approach proposed by the authors, in this paper a low-cost smart flicker sensor has been designed and applied. The proposed sensor can transmit data over a TCP-IP network, in order to allow for a remote monitoring of power quality. The performance of the proposed device has been compared with a standard flickermeter and the main experiment results reported.

Jerzy Augustyn
A COMPARATIVE EVALUATION OF SOME LMS-BASED ALGORITHMS FOR CALCULATING OF IMPEDANCE COMPONENTS IN THE SAMPLING SENSOR INSTRUMENT

The properties of some algorithms based on digital signal processing for the impedance components evaluation in circuits with sampling sensor have been analysed. It is supposed that the voltage and current are sampled synchronously to the fundamental frequency of the generated sinusoidal signal. Two groups of fitting sine wave algorithms, which are based on the least mean square (LMS) technique, have been described. The first one reconstructs indirect measurement method. The second group of algorithms estimates the unknown impedance components by direct method. In all these algorithms to simplify the calculations one can use different form of input matrix. The uncertainty’s propagation by described algorithms can be analysed by means of covariance matrix. In order to verify the performance of the considered algorithms (e.g., accuracy, estimator bias and convergence) the Monte Carlo simulations are realised in MATLAB. It is shown that those algorithms provide minimisation of uncertainty for selected number of samples and phase angles. The influence of the quantization error of the AD converters and jitters of the sampling time upon the uncertainty of the processing results of described algorithms have been carried out.

Jan Fischer, Vladimír Haasz, David Slepicka, Josef Vedral
TRANSPORTABLE REFERENCE AD DEVICE – NEW INNOVATED VERSION

A transportable high stable reference AD device was designed and realised for a comparison of systems for testing a dynamic quality of ADCs or AD modules two years ago. In spite of the fact that several comparative measurements were successfully executed, some limitations and imperfections were found out. Therefore a new innovated version of the device was designed and developed based on existing experiences. The new solution is described in this paper.

Roman Flegar, Tanasko Tasic
SOFTWARE VALIDATION OF SERIAL LINE COMMUNICATION

The software validation of measuring instruments is a complex procedure, which can be divided into the validation of separate software functions. The paper deals with the software validation of functions for serial line communication. It describes methods for preparation and validation. Methods are based on demands and facts, which are important for measuring instruments under legal control. They were developed during type approval process of an automated liquid level measuring instrument, but they can be easily adopted and used with other measuring instruments or communication interfaces. At the end of validation procedure, results of methods are gathered together and evaluated.