## IMEKO Event Proceedings

Page 815 of 851 Results 8141 - 8150 of 8504

**UNCERTAINTY FOR NOISE ATTENUATION MEASUREMENTS OF HEARING PROTECTORS BY REAT METHOD**

The objective of this paper is to present a model for the calculation of measurement uncertainty for noise attenuation measurements of hearing protector by REAT method. The uncertainty calculation was based on the document: "Guide to expression of uncertainty in measurement" by the International Organization for Standardization, first edition, corrected and reprinted in 1995, Geneva, Switzerland. The uncertainty of each source of error was estimated. The overall uncertainty of the noise attenuation measurement of hearing protectors was calculated for each 1/1 octave band frequency test and the results applied in the single number (NRRSF - Noise Reduction Rating for subject fit) uncertainty calculation.

**UNCERTAINTY IMPROVEMENT OF GEOMETRICAL THICKNESS MEASUREMENT OF A SILICON WAFER USING A FEMTOSECOND PULSE LASER**

We describe a method to simultaneously measure geometrical thickness and refractive index of a silicon wafer using a femtosecond pulse laser having 100 nm spectral bandwidth. The improved phase measurement algorithm is applied to increase insensitivity to environmental disturbances and interferometer noise. The measurement results show that the geometrical thickness and refractive index of a silicon wafer were measured to be 320.699 µm and 3.621 respectively, which are the improved results by about one order of magnitude in comparison with previous research. By considering the dispersion effect caused by 100 nm bandwidth source, the conclusion can be reached that there is no dispersion effect on measurement of geometrical thickness.

**UNCERTAINTY IN MEASUREMENT: A KEY CRITERION FOR DEFINING THE COVERAGE FACTOR ASSOCIATED WITH THE MANUFACTURING PROCESS OF WOVEN FABRICS**

This study evaluates the *fractional coverage factor* (Cf_{T}) of a woven fabric before and after the manufacturing process is completed. The uncertainty associated with Cf_{T} was evaluated for specific conditions of mechanical strain of the thread yarns during the weaving process. The economic impact from undesirable geometric deviations of Cf_{T} is performed by making use of the *Taguchi’s Loss Function*. The proposed method proved to be effective to correlate the limits of acceptability of geometrical deviations with the *coverage factor* for a given tolerance of the manufacturing process, thereby reducing the degree of waste.

**UNCERTAINTY IN MEASURING THE NOISE FACTOR OF CASCADE-CONNECTED LINEAR TWO-PORTS**

The paper presents the derived dependence on the total noise factor of cascade-connected linear two-ports in the conditions of energy mismatching. The method of assessing the uncertainty in measuring this factor, which takes into account propagation of standard partial uncertainties of the measurement of the set of four noise parameters, disposable power gains and input and output impedance of particular two-ports, is determined. The uncertainty analysis takes into account the correlation among these parameters. A strict dependence between the mismatching stages of two-ports in the cascade and the uncertainty in measuring the total noise factor is shown. Sensitivity coefficients determining the participation of particular standard partial uncertainties are defined. The results of the analyses and simulations of particular uncertainties components, which were carried out for a typical communications receiver, are presented.

**Uncertainty in Measuring the Power Spectrum Density of a Random Signal**

The method to assess uncertainty in measuring the power spectrum density of a random waveform is presented. Then, the evaluation of assessing uncertainty of power spectrum density is carried out. It takes into account propagation of uncertainties associated with each sample recording in the algorithm of digital signal processing and an error of the estimator bias resulting from a mathematical model of the measured value. The dependences for uncertainties in measuring the power spectrum density of a random waveform are introduced.

**UNCERTAINTY IN PRIMARY GAS FLOW STANDARDS DUE TO FLOW WORK PHENOMENA**

Static gravimetric and static volumetric gas flow standards are both affected by uncertainty components related to the measurement of the change of mass of gas within the inventory volume. In the process of diverting gas into the collection vessel, rapid pressure and temperature changes occur in the inventory volume. A low uncertainty gas flow standard requires thorough understanding of these transients so that appropriate instrumentation, system design, and operating procedures may be developed. A thermodynamic model for the flow work phenomena is presented and compared to experimental measurements and strategies for minimizing their effects on flow uncertainty are discussed.

**UNCERTAINTY IN THE ADC TRANSITION VOLTAGES DETERMINED WITH THE HISTOGRAM METHOD**

This paper, presents an innovative study of the uncertainty in the ADC transition voltages, determined by the Histogram Method for ADC testing. The new approach used, allows for a global and uniform overview of this subject, improving the existing knowledge about the workings of the Histogram Method.

**UNCERTAINTY IN THE TEMPERATURE OF SILICON WAFERS MEASURED BY RADIATION THERMOMETRY BASED UPON A POLARIZATION TECHNIQUE**

The emissivity behaviour of a silicon wafer under various conditions was theoretically and experimentally investigated. As a result, the quantitative relationship between the ratio of p-polarized radiance to s-polarized one, and polarized emissivities was obtained irrespective of the emissivity change of wafers due to the oxide film thickness under the wide variations of resistivity. Based on the result, we propose a new radiation thermometry method that can measure both the temperature and the spectral polarized emissivity of the silicon wafer, and estimate the uncertainty of the measurements. Currently, the uncertainty of the temperature measurement is estimated to be 3.52 K (*k* = 2) and 3.80 (*k* = 2) for p-polarization and s-polarization, respectively, in the temperature range over 900 K.

**UNCERTAINTY IN TORQUE CALIBRATION USING VERTICAL TORQUE AXIS ARRANGEMENT AND SYMMETRICAL TWO FORCE MEASUREMENT**

Calibration machines up to a torque range of 20 kN·m need extensive design if the force is performed by dead weights. A machine based on two force reference standards and a vertical torque axis may serve to avoid these specific problems. The precision force transducers work at a lever arm of precision length. The test piece is mounted in vertical arrangement between a hydraulically operating rotary-actuator and the torque measuring system. Such a calibration machine allows additionally performing easily continuous calibration. Regarding an overall relative uncertainty not greater than 2·10^{-4} there are some significant problems. The estimation of the uncertainty has been proved by comparative tests with the national torque standard by the PTB according to the guidelines EA-10/14 and EA-2/03.

**Uncertainty in uncalibrated microwave resonant measurements**

We present an extended study on the uncertainty in resonant measurements. The uncertainty of the resonant frequency and quality factor was estimated. The effect of the use of uncalibrated resonant curve on uncertainty was extensively studied. For the uncalibrated data the systematic contribution to uncertainty was determined.

Page 815 of 851 Results 8141 - 8150 of 8504