Accredited Calibration Laboratory Research Articles

Improvement of metrology infrastructure in the area of extreme impedance calibrations

The paper describes how the Laboratory for Electrical Measurements at the Ss. Cyril and Methodius University in Skopje, an accredited calibration laboratory, enhanced its calibration and measurement capabilities for extreme values of electrical impedance. This was conducted through development of new calibration methods for instruments that measure extreme electrical resistance and inductance. The paper also explains how these methods were validated to ensure traceability and how the measurement uncertainty in impedance instruments calibration was innovatively estimated, by deploying the data fusion concept to increase the metrology infrastructure capacity. As the testing facilities for electrical quantities in Southeast Europe are not sufficiently developed, and some calibration areas of electrical instruments are not well provided by the existing laboratories, despite the economic and scientific demands, the relevance of this metrology infrastructure upgrade is evident.

Inter-laboratory comparison of a digital multimeter measurement in Turkey

The standard ISO/IEC 17043:2023 specifies the general requirements for proficiency testing providers and covers the development, operation, and reporting of proficiency testing schemes. The standard aims to ensure that the measurement results obtained by different laboratories are comparable and traceable to international measurement standards. Inter-laboratory comparisons are still rare in the meteorological services network of calibration laboratories, and there are not enough bodies accredited with the ISO/IEC 17043:2023 standard in Turkey. The existing inter-laboratory comparison measurements do not fully comply with the requirements of ISO/IEC 17043:2023 and are not compatible with the measurement capabilities and scopes of the laboratories, leading to difficulties when comparing meteorological data from different laboratories. This article presents a case study of a digital multimeter interlaboratory comparison measurement in accordance with the ISO/IEC 17043:2023 standard. The results obtained were analysed using statistical methods (En score) and compared to the reference values provided by a secondary accredited calibration laboratory. The analysis showed that the measurement results obtained by the participants were consistent and generally within the acceptable range of En. The case study presented in this paper demonstrates the effectiveness of the standard in ensuring reliable measurement results in a practical setting.

Perpendicularity assessment and uncertainty estimation using coordinate measuring machine

The validation of the conformity of parts according to the ISO 98-4 standard, cannot be achieved without an accurate estimation of the measurement uncertainty, which can become difficult when it comes to a complex measurement strategy to control a geometrical specification of a mechanical part using a Coordinate Measuring Machine (CMM). The purpose of the study in this paper is to analyze the measurement strategy following the Geometric Product Specification (GPS) Standard, to estimate the associated uncertainty of the different parameters of each step, to be able to achieve the uncertainty of the measurement of a given specification (perpendicularity error in our study) using the Guide to the expression of uncertainty in measurement (GUM). This uncertainty will be thereafter validated by a Monte Carlo simulation, and an interlaboratory comparison will be conducted to compare the obtained results according to the ISO 13528 standard. Our contribution is based on a more accurate estimation of the measurement strategy's parameters uncertainties. This approach can also be used by accredited calibration laboratories (ISO 17025) or in the general case in the control of perpendicularity specification of mechanical parts using a coordinate measuring machine. A case study has been conducted, controlling a perpendicularity specification with a tolerance limit of 15 µm, after the calibration of the CMM to obtain the variance-covariance matrices. The mechanical part perpendicularity error (12.55 µm) was below the limit, however, was judged “not conform” when considering the estimated uncertainty (4.06 µm) and the interlaboratory comparison was satisfactory despite the difference of the acceptance criterion.

Metrological traceability chains for high DC voltage and voltages ratio

The current stage of scientific and technical development is characterized by the widespread use of high-voltage technology. Metrological traceability has such important elements as calibration of measurement standards and measuring instruments and evaluation of measurement uncertainty. The range of values of specific measurands, the range of necessary measurement uncertainties and the measurement standards used are presented as metrological traceability chains. Building such chains for different types of measurements is important for national metrology institutes and calibration laboratories.
 An urgent task is to build metrological traceability chains for high direct current voltage measuring instruments. The proposed metrological traceability hierarchy chains are used in the State Enterprise “Ukrmetrteststandard” for calibration of working standards and working measuring instruments for high DC voltage and voltages ratio. These chains can be used also by accredited calibration laboratories, which carry out calibration of working measuring instruments for high direct current voltage and voltages ratio according to their own scope of accreditation.

Development of an air velocity and flow measurement system by using a novel circular disc

In this paper, development of a sensor using a circular disc for air velocity measurement based on the drag force equation is proposed. The air velocity measurement sensor is basically designed with a load cell in order to determine the drag force. The circular disc is used for creating a drag force, and by using load cell, the drag force that acts on the circular disc is measured. As the circular disc's drag coefficient can be considered constant at Reynolds numbers between 103 and 106, it can be possible to obtain the explicit equation of drag force. The remaining components of drag force equation are obtained by measurement. The proposed air velocity measurement sensor is characterized by wind tunnel measurements. All measurements were performed in an ISO/IEC 17025 accredited calibration laboratory – the Wind Tunnel of Turkish State Meteorological Service. The characterization measurements were performed at air velocities between 1 m/s and 20 m/s. The correction factors were calculated and a calibration curve for the proposed air velocity measurement sensor was obtained. The calibration curve's linearity was higher than 0.99 and a comparison the results from a Micromanometer with Pitot-Tube shows that for the designed working range, the sensor has an acceptable performance for time-averaged air velocity measurements according to the requirements of the World Meteorological Organization.

EURAMET supplementary comparison on calibration of RF current monitoring probe

Main textRF current monitoring probes are commonly utilized in measurements of disturbance currents of cables without making direct conductive contact with the source conductor and without modification of its circuit. They must be calibrated by National Metrology Institutes (NMIs) or accredited calibration laboratories in accordance with international standards such as CISPR 16-1-2 or ISO 11452-4. The RF current monitor probe comparison measurements were conducted with 8 participants; five national metrology institutes (NMIs), two designated institutes (DI) and one commercial calibration laboratory at the frequencies 0.01 MHz, 0.1 MHz, 1 MHz, 10 MHz, 100 MHz, 200 MHz, 300 MHz, 400 MHz and 500 MHz in order to obtain the transfer impedance of the RF current monitoring probe. The comparison measurements started in September 2019 and were completed in June 2020.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Benchmarking FLUKA Monte Carlo code with international measurement standard for air kerma

Various Monte Carlo codes have been used for a long time in gamma ray calibration. However, to the best of our knowledge, no studies have employed the FLUKA MC code for the simulation of photon transport in an accredited calibration laboratory. This study aimed to model the benchmark of the international standard of the air kerma rate and the air kerma rates calculated by FLUKA simulation. As a comparative analysis tool, the linear regression equation used in the accredited calibration laboratory was used. After normalizing the measured and simulated values, a deviation of up to 1.0% was observed, and all the calculated air kerma rates were consistent within the uncertainty. In the analysis using the linear regression equation, the slope and interpolation uncertainty were consistent. Furthermore, the regression error was extremely small, and excellent linearity was observed. Thus, the coefficient of determination was calculated to be five or more. Since calibration sets the standard of every measurement, our study will encourage the application of FLUKA for simulations in various fields involving photons.

Final report for GULFMET.M.M-K4: key comparison of 1 kg stainless steel mass standards

This report summarizes the results of the key comparison (KC) carried out among eight National Metrology Institutes (NMIs) and an Accredited Calibration Laboratory, six of which are member countries of Gulf Association for Metrology (GULFMET). The KC of two 1 kg stainless steel knob weights was decided during the 11th meeting of GULFMET TC Mass held in Abu Dhabi, 2017. TÜBİTAK UME (Turkey) acted as pilot laboratory. The comparison was linked to CCM.M-K4 via INRIM (Italy), METAS (Switzerland), KRISS (Republic of Korea). The results were evaluated by the generalized least square (GLS) estimation. Majority of results were consistent with each other and with the key comparison reference value of CCM.M-K4 within their expanded uncertainties with the coverage factor of k = 2.Main textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Industrial Calibration Procedure for Confocal Microscopes.

Coordinate metrology techniques are widely used in industry to carry out dimensional measurements. For applications involving measurements in the submillimeter range, the use of optical, non-contact instruments with suitable traceability is usually advisable. One of the most used instruments to perform measurements of this type is the confocal microscope. In this paper, the authors present a complete calibration procedure for confocal microscopes designed to be implemented preferably in workshops or industrial environments rather than in research and development departments. Therefore, it has been designed to be as simple as possible. The procedure was designed without forgetting any of the key aspects that need to be taken into account and is based on classical reference material standards. These standards can be easily found in industrial dimensional laboratories and easily calibrated in accredited calibration laboratories. The procedure described in this paper can be easily adapted to calibrate other optical instruments (e.g., focus variation microscopes) that perform 3D dimensional measurements in the submillimeter range.

Interlaboratory Comparisons of Calibration Results of the Measures of Electrical Resistance of Direct Current

For the accredited calibration laboratories in Ukraine, a second round of inter-laboratory comparisons (ILC) of the results of calibration of electrical resistance measures of direct current was conduc­ted. It is important to conduct such rounds of ILC of results with the involvement of an increasing number of calibration laboratories. This will, accordingly, establish the competence of an increasing number of calibration laboratories, which is quite relevant today. The article presents the results of the first round of ILC of the measures of electric resistance 1 Ohm, 10 Ohm and 100 Ohm on a direct current. As an comparison examples by reference laboratory measurement of electrical resistance of direct current P321 and P331, which were already used in the first round of ILC, were selected. The reference labo­ratory has research the measures of electrical resistance as a means of comparison, defined the reference values of comparison with the calculation of their extended uncertainties according to the mea­surement model. The comparison of the results of measurements obtained during the calibration of the measures of electrical resistance of eight laboratories took place according to the radial scheme from 2018 to 2019. The deviations of the results obtained by each laboratory were determined and their correctness was evaluated taking into account the uncertainty of measurements by one of the criteria for performance statistics for the selected electrical resistance ra­tings. The obtained En values show that for all laboratories participating satisfy the set criterion, except for the result of one laboratory for electrical resistance of 10 Ohms. A comparative analysis of the results of the calibration of resistance measures for laboratories that took part in the first and second rounds was carried out.

Evaluation of equivalent dose to eye lens through dose equivalent Hp(3)

PurposeIndividual dosimetry allows to quantify doses from ionizing radiation of exposed workers. Scientific and epidemiological evidences highlight the need for adequate measures for a greater protection of the eye and a reduction in annual doses. ICRP Publication 103, illustrating the operational dose quantity Hp(d) for the individual monitoring, proposes a depth d = 3 mm for eye lens monitoring, indicating that even the Hp(0.07) can be used. In this study, it was investigated if there are differences in the evaluation of the equivalent dose to eye lens (Hlens) using Hp(3) or Hp(0.07). Materials and methodsA slab phantom calibration was performed by an Accredited Calibration Laboratory in terms of Hp(3) and Hp(0.07) using ext-rad TLD-100 (LiF:Mg,Ti) dosimeters. Hp(0.07) and Hp(3) were measured for 26 exposed workers to assess Hlens. The measuring took place monthly in 2017 to obtain both semestral and annual doses. ResultsHlens(0.07) was always smaller than Hlens(3). However, the differences were not statistically significant (Mann-Whitney test, p > 0.05) for both semestral and annual doses. The percentage differences were 7 ± 3%, 6 ± 3% and 7 ± 2% for I semester, II semester and whole year, respectively. The mean underestimation index <10%, intra-class correlation coefficient >0.99, coefficient of variation <3% and the excellent correlation (R2 ≈ 0.999) for both semestral and annual doses highlighted that Hp(0.07) can be used to evaluate Hlens instead of Hp(3). ConclusionsNo statistical evidence was found that the use of Hp(0.07) underestimates the equivalent dose to eye lens obtained through Hp(3).

The Case Study of Water Flow Measurement Comparison in the Range of 12-120 L/min

Nowadays, the water flow measurement involves in our daily life such as water meters for tap water, hydrocarbon flow meters at petrol stations, etc. Those flow meters have to be calibrated by higher accuracy equipments with the accredited calibration laboratory. Therefore the accreditation laboratory has to complete the measurement comparison with reliable laboratory or the National Institute of Metrology (Thailand), NIMT which confirms the traceability chain and the measurement capability. However, the liquid primary standard at NIMT applies volumetric principle to measure flow rate which differs from other laboratories using gravimetric method. Thus, the case study of water flow measurement comparison has been done to verify the possibility of compatibility of those two methods. With high accuracy and good repeatability, the Coriolis mass flow meter was used as the transfer standard in the range of 12 – 120 litre per minute and 12 – 120 kilogram per minute. The comparison result of both measurement principles are considered by using the degree of equivalence, En ratio. The result shows that En ratio is less than 1 which means that both principles are agreed.

An investigation of the base metal thermocouples uncertainty components in ILC comparison

This paper is about unique the interlaboratory large comparison organized under EA-2/14 - Procedure for Regional Calibration ILCs in Support of EA MLA and describe final results of the comparison and several pitfalls when measuring temperature with base metal thermocouple. Interlaboratory comparison (ILC) serves as a tool for comparison of measurement results carried out by accredited or non-accredited calibration laboratories in the relevant field of measurement. ILC represents very effective means to demonstrate technical competence of the participant and also serves as a technical base for accreditation. The subject of this comparison was calibration of several pieces the N-type thermocouples. The pilot laboratory of this ILC was the Department of primary metrology of thermo-technical quantities of the Czech Metrology Institute. The reference values of the test items were provided by the above mentioned organizational unit this company. The evaluation of the measurement results of participating laboratories was performed on the basis of En score (EN ISO/IEC 17043). In this ILC program 47 accredited calibration laboratories from different European countries and also from Bosnia and Hercegovina, Switzerland and Turkey have participated. The results of this comparison demonstrate satisfactory agreement of the majority of the participants measured values with the reference ones within their stated expanded uncertainties. The article also highlights the basic and often neglected components of uncertainty.

CHARACTERISTICS OF INTERNAL AUDITS IN IMPROVEMENT OF QUALITY GOALS IN CALIBRATION LABORATORIES

The Quality Goals and Internal Audits are two important links in the quality management system. These two interrelated points are in many cases surprisingly not considered as they should be. Quality goals aren’t often subject to internal audits. Similarly with quality goals scarcely describe the improvement of internal audits as a tool to strengthen the quality management system. The fact, recent audit findings found no more than 11 out of 165 findings in 18 accredited calibration laboratories operated on the basis of ISO/IEC 17025 that relates to quality goals. This paper proves no strong correlation between quality goals and internal audit statistically. The importan thing for the improvement of quality goals – internal audits relationship is giving more clarification to clause 4.10 Improvements and add internal audit-based items on the quality goals.

Limited comparability of creatinine assays in patients with liver cirrhosis and their impact on the MELD score

Background & aimPatients with end-stage liver disease require valid estimations of mortality for organ allocation and risk stratification. The model of end-stage liver disease (MELD) score is used for this purpose in most countries and incorporates bilirubin, International Normalized ratio, and creatinine. The aim of this study was to evaluate the comparability of creatinine results from different routine assays in the serum samples of patients with liver cirrhosis. MethodsResidual material from 60 serum samples was available from patients in different stages of liver cirrhosis. Four centers participated; each center analyzed the samples with Jaffé-based and enzymatic routine assays in parallel. In addition, an accredited calibration laboratory certified the panel of samples by an internationally accepted reference measurement procedure (RMP) based on isotope dilution mass spectrometry (ID-MS). This method served as the independent reference. ResultsAll routine methods displayed a high correlation to the RMP (r ≥0.937, p<0.001). Two enzymatic and two Jaffé-based methods provided results that were all within a ±20% range of the RMP. The other methods showed deviations >20% in up to 27% of the samples. The enzymatic methods were systematically lower, whereas the Jaffé-based methods were systematically higher (p<0.001). The resulting MELD scores differed from 0 to 4 points. ConclusionsThere are systematic deviations from the RMP. Jaffé-based assays gave higher results, whereas the enzymatic-based assays gave lower results compared to the results of the RMP. The comparability of results is limited and could be disadvantageous to patients listed for liver transplantation.

EURADOS intercomparisons for individual monitoring services: Results of the 2015 extremity dosemeter intercomparison for photon and beta radiations

In 2008 EURADOS (the European Radiation Dosimetry Group) started a programme of regular dosemeter intercomparisons to assist harmonisation of individual monitoring services (IMS). In 2015, IC2015ext for extremity dosemeters was coordinated by the Seibersdorf Labor GmbH/Austria. In total 72 different systems were tested. These were from 52 IMS from 21 countries and one international institution. Extremity dosemeters (ring, wrist/ankle and fingertip) were irradiated, dose quantity Hp(0.07), with photon and beta radiations. Irradiations were carried out by the accredited calibration laboratory VSL (Dutch national metrology institute/Delft). The irradiation plan was designed to allow the systems to be tested for linearity, energy response and angular response. The results show that, in general, extremity dosemeters perform better for photon than for beta radiations. 57% of systems showed at least one outlier, as defined in ISO-14146, revealing that there is still scope for improvement in the field of extremity dosimetry. This paper presents the results of IC2015ext and compares these results with IC2009ext.

Bilateral comparison on electric field measurements between TÜBİTAK UME and SASO NMCC

Electromagnetic (EM) probes are widely utilized in the measurement of EM fields for non-ionizing radiation, electromagnetic compatibility (EMC) testing and other applications in the frequency range 5 Hz–60 GHz. They must be calibrated by National Metrology Institutes (NMIs) or accredited calibration laboratories in accordance with international standards such as IEEE 1309. The existing NMIs or emerging NMIs should refer to the international comparison measurements in order to assure the quality of their measurement results. Therefore, the electric field comparison measurements organized by TUBITAK UME were performed between TUBITAK UME and SASO NMCC at the 100 Hz, 1 kHz, 10 MHz, 100 MHz, 1 GHz, 10 GHz and 18 GHz frequencies in order to obtain the correction factors of the electric field probes. The comparison measurements were carried out in accordance with the Technical Protocol prepared by TUBITAK UME. The measurements started in October 2017 and were completed in January 2017. There was good agreement found for the correction factors.Main textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Software validation applied to spreadsheets used in laboratories working under ISO/IEC 17025

Several documents deal with software validation. Nevertheless, more are too complex to be applied to validate spreadsheets - surely the most used software in laboratories working under ISO/IEC 17025. The method proposed in this work is intended to be directly applied to validate spreadsheets. It includes a systematic way to document requirements, operational aspects regarding to validation, and a simple method to keep records of validation results and modifications history. This method is actually being used in an accredited calibration laboratory, showing to be practical and efficient.

Summary of Outside Micrometer Calibration Proficiency Testing (PT2014-KA02) in Taiwan

Abstract:Proficiency testing is an established way to demonstrate a laboratory's measurement capabilities. Accredited laboratories are usually requested to participate in proficiency testing conducted by the laboratory accreditation organizations in their countries. The Center for Measurement Standards / Industrial Technology Research Institute (CMS/ITRI) has long been committed to measurement technologies and statistical engineering in Taiwan and is one of the Proficiency Testing Providers (PTPs), with an accreditation number of P002, accredited by Taiwan Accreditation Foundation (TAF). This paper summarizes the results of a 2014 outside micrometer calibration proficiency testing scheme, number PT2014-KA02, held in Taiwan. Twenty-five TAF accredited calibration laboratories participated in the proficiency testing, and the |En| values of each participating laboratory are smaller than one. This implies that all the participants' results are satisfactory with respect to each other and that the measurement c...

Comparison of extrapolated and interpolated temperature scales from 1000 °C to 2500 °C between a national measurement institute and an ISO17025 accredited calibration laboratory

The current high temperature part of the international temperature scale of 1990 (ITS-90) is based on extrapolation from a reference fixed point, using Plancks law in ratio form. However in the near future the mise en pratique for the definition of the kelvin will also allow an interpolated thermodynamic scale based on high temperature references whose temperatures are known a priori. Both approaches to dissemination will be considered equally valid. A transfer radiation thermometer specifically designed with the dissemination to industry of a temperature scale based on the mise en pratique-kelvin approach has been constructed. It was calibrated at a national measurement institute and used to compare the two possible realisation schemes (i.e. radiation thermometer calibrated to ITS-90, and the same thermometer calibrated using high temperature references) to the local ITS-90 scale at an accredited industrial calibration laboratory. All the scales agreed within their respective uncertainties. It was found that the interpolation scheme could significantly reduce the uncertainties in a calibration laboratory without the full cost of maintaining ITS-90.