IMEKO Event Proceedings

Page 816 of 851 Results 8151 - 8160 of 8504

Ranny Michalski, Marco Nabuco, Gustavo Ripper
UNCERTAINTY INVESTIGATION OF FIELD MEASUREMENTS OF AIRBORNE SOUND INSULATION

Sound insulation is very important for the acoustic quality of buildings. The Brazilian Association of Technical Standards, ABNT, published a set of standards concerning the evaluation of the performance of buildings up to five floors, ABNT NBR 15755, and sound insulation is one the considered topics. Minimum, intermediate and superior values are presented for some acoustic parameters. In order to make measurements carried out by different professionals comparable with the values established in the standards, the uncertainty of the results shall be expressed. The Guide to the Expression of Uncertainty in Measurement, ISO/IEC Guide 98 (GUM), is the international document that standardizes how to assess the uncertainty of a measurement result.
In general, two types of methods are used to measure sound insulation parameters: the classical method and the new method or impulsive response method. However, there is not an established and simple procedure to obtain the measurement uncertainty. Uncertainties estimates are available only for the classical method.
Measurements of airborne sound insulation between rooms were carried out in field conditions with the impulse response method and the work presents a study of the estimate of the uncertainties of the results, in accordance with the GUM.

Salvatore Caldara, Rosario Miceli, Pietro Romano, Ciro Spataro, Fabio Viola
Uncertainty management in the measurements of low frequency magnetic fields

The paper deals with low-frequency magnetic field measurements carried out by using a broadband and isotropic instrument. These measurements are characterized by very high uncertainty values, which imply a high risk of wrong decisions when there is the need to establish if a site complies or does not comply with specified emission limits. To reduce this risk, we decided to perform the so called “uncertainty management” that is the discipline of optimizing the cost of a measurement versus the uncertainty target. The task is achieved by using the PUMA method that is an iterative technique originally conceived for geometrical and mechanical measurements. The approach is completely based on the “Guide to the Expression of Uncertainty in Measurement” rules, but provides a more engineering methodology. By using this approach, it is possible to avoid the usage of too expensive instrumentations or, on the contrary, too expensive resources for the uncertainty estimation.

Yuri Machekhin
UNCERTAINTY MEASUREMENT AND DYNAMIC SYSTEM CHAOTICAL BEHAVIOUR

Chaotic behaviour of nonlinear dynamic system as a mechanism of influence on uncertainty measurement are discussed. Based on the logistic equation as a mathematical model, measeurement uncertainty investigated. In the case when dynamic chaos take place in the system, uncertainty measurement has anormal distribution.

Jan Blaška, Miloš Sedláček
UNCERTAINTY OF AMPLITUDE DFT SPECTRUM ANALYSIS IN POWERLINE SYSTEMS

Characterization of measurement by uncertainty becomes a commonly accepted practice. Since in case of several sources of uncertainties which may even be correlated finding the resulting uncertainty according to the Guide to the Expression of Uncertainty in Measurements [1] is not an easy task, computer simulations are a suitable tool respecting the possible correlations of quantities influencing uncertainty. Analysis of DFT spectrum uncertainty was published elsewhere for coherent sampling. We compare correction factors and remaining uncertainties of two methods of the DFT spectrum analysis applicable for noncoherent sampling. Simulations are performed on power-line frequency with predefined harmonic components and noise and ideal quantizer with selectable resolution.

Edi Kulderknup, Viktor Krutob, Jürgen Riim
UNCERTAINTY OF BRAKING PARAMETERS MEASUREMENTS BY VEHICLES TECHNICAL INSPECTION

Nowadays more widely is taken to use the road vehicles periodical inspection with aim to have knowledge of the technical level of item and to assure the safety. To have the assured right inspection results there shall be used various testing and measurement procedures. Among of the important are measurements of the parameters showing the road vehicles brakes correct operation. To give proper conformity estimation to the vehicles brakes operation shall be used uncertainty of measurement result. To give more confidence to the estimated uncertainty components suitable way is to carry out measurement comparisons of brakes parameters.

A. R. Valdés, A. Piratelli-Filho, D. P. Vieira Sato
UNCERTAINTY OF COMPONENTS OF VOLUMETRIC ERRORS

The aim of the present work is to calculate the uncertainty associated with volumetric error components in a Moving Bridge type Coordinate Measuring Machine (CMM). Two methodologies are presented for this purpose. The first consisted in equationing the components of the volumetric error using homogeneous transformations techniques; measurement of the geometric errors and Abbé offsets; mathematical models regarding each geometric error and Abbé offset were written and the law of uncertainty propagation was applied. The second methodology present simplified models to estimate the measurement uncertainty associated with volumetric error component, identifying the variables that influence the determination of geometry deviations, development of a mathematical model for the volumetric error components, development of a routine to evaluate uncertainty. It was concluded that the simplified models are adequate and easy to be applied. As conclusions, the components of volumetric error of X, Y and Z axes present uncertainty values close to 2.7, 4.0 and 2.0 mm, respectively.

F. Corrêa Alegria, A. Cruz Serra
UNCERTAINTY OF ESTIMATES OBTAINED WITH THE HISTOGRAM TEST OF ADCS

We present here expressions to determine the uncertainty interval of the estimates of transition voltages and code bin widths of an analogue to digital converter obtained with the Standard Histogram Test. We consider the presence of additive noise as it influences the precision and causes a bias on the test results.

Zhijie Zhang, Wei Wang, Wenlian Wang, Daihua Wang
UNCERTAINTY OF MEASUREMENT OF TRANSIENT PRESSURE

The measurement of air shock wave pressure is a typical problem of transient measurement. Because the measurement data in many cases is used to judge the quality of a product, or as a basis for changes being made during a development phase, uncertainty analysis or assessment of measurement data takes a very important role in the process of reporting experimental results. It is very difficult or impossible for most transient measurements to be experimented repeatedly under the same condition, so their uncertainty analysis differs from the method of analyzing static measurement data. The paper gives several main components of uncertainty and their experimental data of the measurement system of air shock wave pressure, especially analyses and processes dynamic sensitivity and overshoot values of the system excited by step pressure signal which is generated by shock tube. The results of uncertainty analysis are presented. The method of dynamic uncertainty provides a kind of solution to analyze and assess the result of single measurement or a few measurements.

Dusan Agrez
UNCERTAINTY OF NON-UNIFORM QUANTIZATION AND INFORMATION

In many analog-to-digital conversion schemes, numerical values are attained with successive approximations of the difference between the reference and measured quantity. For effectiveness of differential tracking, the non-uniform quantization must fulfil three conditions: partitions into halves, increasing quantization uncertainty with difference, and low overlapping of the quantization intervals. The best trade between the number of decision levels and the settling time is with pure exponential quantization rule. The fastest response is achievable with base 2. The information rate per step is a little below three. The number of bits decreases towards the end of conversion and the sharp stop of the uniform constant information flow is smoothed.

Edi Kulderknup
UNCERTAINTY OF OCCUPATIONAL HEALTH MEASUREMENTS

Occupational health measurements have considerable importance to safeguard the health of personnel in the working environment. Assurance of healthy conditions is prescribed in legal acts and if those requirements are not fulfilled can entrepreneur have considerable economical losses trough the authorities sanctions and charges for the damaged personnel. To have correct conformity estimation against legal limit values evaluator must have the reliable result of measurement and the truthful uncertainty estimation. Uncertainty estimation of occupational health measurements have some special particularities. Sound way to assure the best measurement capability is the interlaboratory comparison.

Page 816 of 851 Results 8151 - 8160 of 8504