In this paper Adaptive Chirp transform (ACT) and Chirp-z transform (CZT) for measurements of frequency spectrum are presented. Algorithms are adjusted according to IEC 61000-4-7 standard. Interpolated ACT with narrowed frequency span is used for Phase Lock Loop (PLL) synchronization. The CZT is used along with windows function, to obtain the amplitudes of signal harmonics and interharmonics. Window function length is defined by PLL. All parts of proposed algorithm are tested through various simulations with changing parameters of analysed signals. This paper shows that CZT can be adjusted to...
The paper is devoted to the numerical differentiation of measurement data. A new method, based on analytical differentiation of the least-squares approximation of data by means of shifted trigonometric functions, is proposed. It is compared with the most popular method of central difference and with a specialised version of the Kalman filter. Some conclusions, concerning metrological applicability of all three methods, are drawn.
We present two stochastic modelling approaches to improve state estimation in low and medium-voltage grids. First, a dynamic model for a disturbance observer state estimation is proposed, which introduces a stochastic component into the disturbance dynamics. Second, an approach based on a stochastic electrical power generation model is considered. This model is based on PV data and incorporates information about the seasons and the type of the PV generation units.
An inconsistency with respect to variable transformations in our previous treatment of the cosine error example with repositioning (Metrologia, vol. 47, pp. R1–R14) is pointed out and three remedial procedures are proposed. The problem refers to the measurement of the vertical height of a column of liquid in a manometer. A systematic effect arises because of the possible deviation of the measurement axis from the vertical, which may be different each time the measurement is performed. The proposed procedures are: a) merging of independent probability density functions for the measurand and...
The paper deals with the use of the Huang Hilbert Transform (HHT) for the analysis of transient signals in non linear circuits. Differently from traditional methods that decompose a signal as the sum of apriori adopted waveforms, HHT procedure decomposes the signal of interest in oscillatory modes aposteriori determined, in dependence on the signal characteristics, giving, thus, a better information about the physical characteristics of the observed system. The performance of the proposed analysis method has been evaluated by applying the HHT to the current acquired from an actual RLC...
The paper presents a brief analysis of works associated with the choice of transformation functions for smart pressure sensors. The notion of complexity factor and offer a way to assess the complexity of models for different types of transformation functions was given.
Paper presents a study under the Quality of Service in modern wireless sensor networks. Such a networks are characterized by small amount of data transmitted in fixed periods. Very often this data must by transmitted in real time so data transmission delays should be well known. This article shows multimode network simulated in packet OPNET Modeler. Also nowadays the quality of services is very important especially in multi-nodes systems such a home automation or measurement systems.
The paper presents an application of probabilistic model to describe a radio propagation delay in indoor environment. Model is based of delta functions sequence to describe retransmissions between a transmitter and a receiver. Theoretical considerations have been verified by measurement results obtained by using the experimental system developed for investigating delays caused by external disturbances influencing the wireless transmission. One of such a commonly occurring disturbances are walls in building where the radio signal is propagating.
The purpose of this paper is to show as the optimal linear filtering of measurements during calibration of the instrument can simultaneously consider the factors that affect the accuracy of estimates. The Kalman filter or linear quadratic estimation allows taking into account the previous changes of the device characteristics, the correlation between the points in the measurement range and working space.
Measurement results of continuous quantities are not precise numbers, but more or less non-precise. They are connected with different kinds of uncertainty: Variability, errors, and fuzziness. This fuzziness of individual measurement results is different from errors, and the best up to date description of this imprecision is by fuzzy numbers. Examples will be given how to obtain the characterizing functions of fuzzy data, and to illustrate the generalized analysis method, which uses fuzzy models.