CC BY
0ASSESSMENT OF UNCERTAINTY AND ITS IMPACT ON THE
QUALITY OF MEASUREMENTS
*L.T.Marysheva, 2N.H. Latipova, 3B.A. Nazarbayev
1,2Tashkent University of Information Technologies 3Tashkent State Technical University https://doi.org/10.5281/zenodo.10674233
Abstract. This article shows the relationship between uncertainty and the quality of measurements, which directly affect all areas of human life. The uncertainty of measuring instruments gives us a wide scope for new research and improving the level of quality in enterprises and in all other areas.
Keywords: uncertainty, international union, quality, uncertainty assessment
Introduction. The concept of "uncertainty" in measurements, as a quantifiable characteristic of measurement accuracy, is relatively new in the history of measurement, in contrast to the terms "error" and "error analysis", which have long been used in the practice of metrology.
Despite the fact that in some countries measurement uncertainty began to be assessed relatively long ago, the lack of international unity on this issue led to the development of seven international organizations: International Bureau of Weights and Measures (BIPM), International Electrotechnical Commission (IEC), International Federation of Clinical Chemistry (IFCC), International Organization for Standardization (ISO), International Union of Pure and Applied Chemistry (IUPAC, IUPAC), International Union of Pure and Applied Physics (IUPAP), International Organization of Legal Metrology (OILM) such an international document as the "Guide to the Expression of Uncertainty in Measurements" (hereinafter referred to as the Guide). The objectives of this Guide are:
• provide full information on how to report uncertainty;
• provide a basis for international comparison of measurement results. In the era of global markets, it is necessary that the method for estimating and expressing uncertainty be uniform throughout the world so that measurements made in different countries can be easily compared. And it is precisely this universal method, applicable to all types of measurements and various levels of accuracy in many areas of measurement, ranging from the resistance store to fundamental research, that the Guide provides. The principles in this Guide are intended to be used in a wide range of measurements, including those required for:
• quality assurance during the production process;
• consistency and strengthening of laws and regulations;
• conducting fundamental and applied research in science and technology;
• standards and instruments for calibration and testing;
• development, maintenance and comparison of international and national standards, including standard samples of the composition and properties of substances and materials.
With the adoption of the international standard ISO/IEC 17025-2002 [1], which sets requirements for the competence of testing and calibration laboratories, the requirements for uncertainty assessment in accredited laboratories have become international. Thus, in the last
decade, "uncertainty" has become the single most complete and, most importantly, internationally recognized characteristic of measurement accuracy.
In accordance with GOST ISO/IEC 17025-2019 clause 7.6.3, the testing laboratory is required to assess the measurement uncertainty. If a test method does not provide a rigorous assessment of measurement uncertainty, then the assessment must be made based on an understanding of the theoretical principles or practical experience with the method.
According to GOST 34100.3-2017/Is0/IEC Guide 98-3:2008, measurement uncertainty, part 3, guidance on the expression of measurement uncertainty, is an expression of the fact that for a given measured quantity and a given measurement result there is not one, but an infinite number of values , scattered around the measurement result, which correspond to all observations and original data.
Uncertainty (of measurement) is a parameter associated with a measurement result that characterizes the spread of values that could reasonably be assigned to the quantity being measured.
The term "uncertainty" means doubt, and therefore, in a broad sense, "measurement uncertainty" implies doubt about the reliability of a measurement result.
Estimation of uncertainty for individual components. In some cases, especially when data on method performance are limited or unavailable, the most appropriate procedure may be to estimate each component of uncertainty separately.
The general method used when summing up individual components is to establish a detailed quantitative model of the experimental procedure, estimate the standard uncertainties associated with the input parameters, and sum them up [3].
From the definition of "uncertainty" it follows that it is a quantitative measure of the accuracy of the corresponding measurement result, and expresses the degree of confidence with which it can be assumed that the value of the measured quantity under measurement conditions lies within a certain range of values. Or in other words, uncertainty is a quantitative measure of how reliable an estimate of the measured value is the resulting measurement result. Uncertainty makes it possible to compare the results of different measurements of the same measured quantities with each other or with reference values.
One of the most common mistakes in testing laboratories is incorrectly calculating the uncertainty when evaluating applied techniques, thereby overlooking and not taking into account the importance of small and seemingly insignificant devices.
In addition, many laboratories have their own "decision rules" or similar rules, which are provided by the customer to record information about the conformity of the sample or product being tested in the measurement report. If the confidence level specified by the customer is insignificant, then the decision made by the laboratory based on the result obtained and the error added to it will be erroneous. The laboratory is responsible for this decision, reflected in the protocol, as well as for the reliability of the measured value.
Calculating measurement uncertainty is quite a labor-intensive task, even if you use a calculator or formulas written into spreadsheets. Typically, when working with a conventional instrument, the user is forced to manually make several measurements at each point, from which he then also manually calculates the measurement uncertainty. However, measuring instruments are now being produced that have a built-in calculator for calculating measurement uncertainty.
For example, a professional device for measuring illumination "Elite01" or a very inexpensive professional digital lux meter "Elite-mini". This became possible quite recently, thanks to the use of digital signal processing in such devices, which allows processing thousands of intermediate measurements and accompanying factors to obtain the final result.
Let us give an example of calculating measurement uncertainty. To calculate the uncertainty of measurement results, it is necessary to perform multiple measurements of a quantity.
If, when measuring illumination in the workplace, you use a conventional device - the Elite02 luxmeter-pulsimeter (the permissible basic relative error in illumination measurements is 8%), then you will have to take several measurements. For example, let the following 6 illumination values be obtained at the specified workplace: 388, 377, 369, 369, 370, 372 lux.
The calculation of uncertainty is carried out as follows:
Calculate the arithmetic mean of the illumination from all measurements at a given point:
1 n
E=11 E, (l )
n
i=1
1 2245
E =-( 388+377+369 + 369 + 370 + 372 ) = ^^ = 374 ak 66
2. For sources of uncertainty of a random nature, we calculate uncertainty according to type A:
For sources of uncertainty of a systematic nature (instrument error), we calculate
Uncertainty according to type B: where ±AE is the limits of permissible instrument error, and as the illumination value we take the average illumination value of 374 lux, calculated in paragraph 1, taking into account the error of 8% of the Elite02 device. 4. Calculate the total standard uncertainty:
5. For a confidence level (coverage probability) P = 0.95 (recommended in the Uncertainty Calculation Guide), we set the coverage factor k = 2 and calculate the expanded measurement uncertainty:
The result of calculating the uncertainty of illumination measurements for the Elite02 luxmeter: Expanded uncertainty of the illumination measurement results with the Elite02 device U(E) = 9.4%
REFERENCES
1. Ismatullaev P.R., Matyakubova P.M., Turaev Sh.A. Metrology, standardlashtirish va certificatelashtirish. Darslik. "Lisson-press", Tashkent, 2015. -423b.
2. Matyakubova P.M., Kuluev R.R., Sheina N.E. Metrology and standardization. Textbook-T:-2023, 312 s
3. STB ISO/IEC 17025-2002. General requirements for the competence of testing and calibration laboratories.
4. Zakharov I.P., Kukush V.D. Theory of uncertainties in measurements. Textbook: Kharkov, Consum, 2002. 281c.
5. Eshmuradov D., Bahronova S. ISO SERTIFIKATLASHTIRISH XALQARO STANDARTLARINING BIR TURI SIFATIDA //Engineering problems and innovations. -2023.
