## IMEKO Event Proceedings

Page 790 of 822 Results 7891 - 7900 of 8218

**UNCERTAINTY PROPAGATION IN MULTI-STAGE MEASUREMENTS USING LINEAR REGRESSION ANALYSIS AND MONTE CARLO SIMULATION**

Linear Regression Analysis (LRA) is one of the statistical tools most intensively used in all branches of science, with many applications in the study of measurement processes and is therefore important in metrology. The implementation of metrology in quality systems, led to a widespread evaluation of measurement uncertainties based on the GUM uncertainty framework (Guide to the Expression of Uncertainty in Measurement). This methodology, however, has its own restrictions among which one could include the use of LRA in multi-stage measurement. To overcome these restrictions, an alternative approach considers the use of the Monte Carlo method to evaluate LRA uncertainties and, subsequently, to use it further in the evaluation of uncertainties in multi-stage measurement processes.

**UNCERTAINTY REDUCTION IN MEASUREMENT SYSTEMS BY STATISTICAL PARAMETER DESIGN**

In measurement system design, uncertainty is usually reduced by a cost increase: more accurate components are selected and narrower variations to influence parameters are imposed. In this paper, an alternative cost-saving approach is proposed: suitable values of design parameters capable of minimizing the measurement uncertainty due both to component’s uncertainty and to influence parameters are identified without any loss in other metrological performances. With this aim, a general method based on statistical parameter design is proposed. The method effectiveness is highlighted by an experimental case study related to the design of a pass-band passive filter.

**UNCERTAINTY RELATED WITH THE USE OF LINEAR REGRESSION ANALYSIS FOR THE CORRECTION OF CALIBRATED INSTRUMENTS**

Linear Regression Analysis (LRA) is a technique commonly applied in many different branches of science. The present study investigates the use of LRA in Metrology and aims to develop a mathematical approach to adequately take into account its contribution for the uncertainty budget in a measurement.

In a calibration involving many standards and measuring instruments, the LRA technique is an important tool for the estimation of conventional true values based on certificate results. This statistical treatment usually intends to reduce the errors measured in the calibration process in order to achieve lower residual errors. The operation, however, introduces statistical uncertainties, which can be of significance when compared with the uncertainty contributions from other input quantities.

This document also presents the results of a measurement uncertainty evaluation related to the calibration of a length measuring machine, including the LRA contribution based on the application of the mathematical expression proposed. The relative influence of this contribution is also investigated.

**Uncertainty Reproduction of the Three-phase Voltages System’s Asymmetry Analysis**

Methods of reproduction of one-phase alternative voltage is widely known in measuring techniques. Developers apply the same methods to reproduce electric power quality indexes (EPQI) of three-phase networks, which consist of direct, reverse and zero symmetrical sequences. However these parameters depend not only on the amplitude of one vector of voltage of three-phase networks but on amplitudes of all of them and also on the phase angle between them, which is not taken into account by developers. It generates substantial disparity between the real uncertainty and uncertainty, caused only by inaccuracy of value of the amplitude of one vector of voltage of the network. On paper, the uncertainty of reproducing one of the parameters of quality of electric power was analysed in detail, taking into consideration its complex character. The result of comparing the uncertainty, which was calculated with consideration her complex character and without it, is given.

**UNCERTAINTY SCOPE OF THE FORCE CALIBRATION MACHINES**

Using the method specified in EAL-G22 (new ref. EA-10/04) with corresponding mathematical model functions for each type of force calibration machine and providing a practical example, the paper describes the approach adopted to apply EAL-R2 (new ref. EA-4/02) to the statement of the best measurement capability achievable for forces. The scope of the calibration laboratory can thus be defined according to the criteria of the accreditation body ensuring that the normalized error remains < 1, when inter-laboratory comparisons are performed.

**Uncertainty to harmonic measurements with DFT techniques**

The harmonic content generated by the use of non-linear loads can cause an electrical device to operate improperly. For this reason, reliable measurements of this parameter are fundamental to guarantee the results needed by the electronics industry and medical devices. The aim of this work is to describe the development of a measurement system of harmonic signals with traceability to the international system of units (DC voltage), and its uncertainty levels. The system consist a software developed in Visual Basic language based on a voltmeter with a General Purpose Interface Bus (GPIB) able to digitalize a signal with sampling rates up to 100,000 samples per second. A Discrete Fourier Transform algorithm is used to evaluate the harmonic content of the signal. The work consists of a tool for the calibration services provided by the laboratory LABELO-PUCRS, and its results indicate the best capability (uncertainty) to harmonic measurements.

**UNCERTAINTY VALIDATION IN THE CALIBRATION OF INDUSTRIAL PLATINUM RESISTANCE THERMOMETERS (IPRT) USING MONTE CARLO METHOD**

Monte Carlo method by simulation has been done to validate calibration of IPRT. The work is based on the Callendar van Dusen equation for 0 °C to 500 °C calibration range. How to derive the mathematics model for running the simulation is also described. Results are compared with results obtained by the propagation of uncertainty (GUM) which shows good agreement and coherent.

**Uncertainty-based combination of signal processing techniques for the identification of rotor imbalance**

This paper describes a method for the uncertainty-based combination of signal processing techniques for the identification of rotor imbalance. The main idea of the proposed method is to compute the imbalance with different algorithms and to average their results. The method is based on the data fusion at feature level and uses the measurement uncertainty of the imbalance as a figure of merit for the weight computation. A static and a dynamic implementation are presented. In the static one, the weights are computed in a dedicated training phase, in which four algorithms (Fourier transform and quasi-harmonic fitting of signal denoised with Hilbert-Huang Transform, Hilbert Vibration decomposition, and Wavelet Packet decomposition) have been used to estimate the known imbalance of car wheels. In the dynamic one, the weights are computed at runtime by estimating the difference between each predictor and the actual signal. Experimental results evidenced the validity of the proposed method, with uncertainty reductions between 10 and 40%, with larger benefits in presence of localized disturbances.

**Unconventional double-current circuit – accuracy measures and application in two-parameter measurement**

In this paper some interesting and novel features of a four-terminal (4T) network are presented. A single DC current source is switched over and connected in turns to opposite arms of the four-element bridge circuit. This two-voltage-output circuit is called a double current bridge. The output voltages are dependent on the arm resistance increments and their values are given in absolute and relative units. The accuracy measures (limited errors and standard uncertainties) of two transfer functions are presented. A simple application with two sensors acting as strain gauges and RTD’s is presented. The simplified signal conditioning formulas of two- parameter measurement of strain and temperature of a cantilever beam are discussed. Some results achieved with the use of the circuit are presented.

**UNDERESTIMATED IMPACT OF MEASURING CABLES ON HIGH-PRECISION CARRIER FREQUENCY AMPLIFIER RESULTS AND COMPENSATION METHODS THEREFOR**

The resolution when acquiring transducer results is physically limited. To ensure accurate measurements of resistive transducers in full bridge circuitry, in addition to the amplifier's precision, the use of appropriate measuring cables and their proper connection are very important.

Sources of errors with respect to the used measurement cables and their compensation to achieve the high accuracy class are shown. If these principles are not observed, there will be inescapably significant errors.

Page 790 of 822 Results 7891 - 7900 of 8218