Secondary Calibration Laboratories Research Articles

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.

GUI development for SSDL to calibrate photon measuring equipment

Current legislation mandates the inspection and calibration of operational survey radiation monitoring instruments used in nuclear medicine, radiotherapy departments, and other fields utilizing ionizing radiation sources. To comply with national and international radiation protection standards, Morocco's National Secondary Standard Dosimetry Laboratory provides reliable calibration results with high accuracy and covers various measurement ranges using attenuators provided by the automated Gamma G10 irradiator or validated beam qualities produced by the X-ray irradiator type X80–320 kV.This study aims to develop a digital graphical user interface using Python programming language, designed for calibrating radiation protection measuring instruments . The interface is intended to facilitate all operations and calculations related to determining calibration factors and measurement uncertainties in accordance with the ISO 4037 standard, ensuring minimal processing time and minimizing potential error sources . The interface enables calculations to be recorded, as well as the establishment and electronic archiving of the calibration certificate and the report in PDF format using the Hypertext Preprocessor FPDF library (PHP FPDF). With the development of this interface, multiple instruments can be processed per day with high accuracy, streamlining the calibration process and improving efficiency.•The importance of compliance with international standards to ensure the quality and reliability of measurements in radiation protection was examined.•Description of X-ray and Gamma-ray irradiators designed for the calibration of radiation protection measuring instruments within the Secondary Dosimetry Calibration Laboratory (SSDL) which is a member of the WHO/IAEA network within the National Center for Radiation Protection of Morocco•Graphical User Interface using python for the calibration of photon measurement instruments for radiation protection purposes was developped.

New S-chamber Mid-Term electrets: Experimental characterization and uncertainty evaluation

Electret ion chambers are widely used passive detectors, employed for measurements of radon activity concentration in air. These devices are made of a Teflon electret coupled to an interchangeable ion chamber. A new type of electret produced by Rad Elec Inc., named Mid-Term, is used together with the S-type (200cm3) chamber. It is designed to be operated in an intermediate range with respect to the standard Short-Term and Long-Term electrets. This work describes the complete characterization of such device, performed according to the ISO guidelines. The characterization was carried out in the secondary standard calibration laboratory of Politecnico di Milano Italy, and with a traceable radon chamber. The coefficients and equations presented can be used by operators to assess both the radon activity concentration and the related uncertainty, with the only requirement of the knowledge of the background gamma air kerma rate of the specific measurement site and its related uncertainty.

Measurement uncertainty evaluation model in radial composite gear inspection

A general expression to estimate the measurement uncertainty of double-flank gear rolling tests, according to the uncertainty budget method outlined in the GUM, is presented in this paper. This method is more precise than the comparator method and it allows us to know the individual contributions of each error source. Therefore, it is often applied in secondary calibration laboratories or industrial facilities that require a better understanding of their measurement process capability. Furthermore, the proposed expression can be adapted to estimate the measurement uncertainty of any gear tester configuration that works under rolling principles. The paper describes a case study where the uncertainty budget developed is applied to a double-flank worm gear rolling tester. Using experimental values of calibration and characterization of the gear tester, the expanded uncertainties of the rolling parameters Fi”, Fr” and fi” were calculated. Finally, an optimized uncertainty budget is proposed where the main detected error sources are minimized improving therefore the measurement capacities of the tester.

Measurement comparisons: A tool to guarantee the reliability of measurement systems and of high-tech industry

Measurement comparisons or inter-laboratory comparisons (ILCs) are the main tool to establish the measurements' compatibility between different laboratories or different measurement methods. Therefore, they are a mean to establish the equivalence of national standards maintained at the National Measurement Institutes (NMI), the correctness of the measurement traceability transfer from NMIs to secondary calibration laboratories, of their accreditation processes and the suitability of their operators' competence and equipment. ILCs' role is then of strategic importance as the NMIs and the secondary calibration laboratories lay at the top of a chain representing the measurement system of each modern industrialized country. Each step of this chain has to be under control to assure that final products (or product parts) could eventually assembled with other parts made in other countries. At the level of NMI, high-level key comparisons are carried out to compare national standards while at the national level, ILCs between NMIs and secondary laboratories are useful to verify the capabilities of these laboratories. Secondary laboratories calibrate standards and instruments of lower level and industrial laboratories. As these last ones support directly the industrial and manufacturing sectors, it can be concluded that ILCs are the main tool to assure the reliability of measurement systems and thus a strategic support for high-tech modern industry.

The INRIM Role of Inter-laboratory Comparison Provider for Electrical Power and Energy at Industrial Frequency: A Two-Year Activity Report

The technical surveillance of secondary calibration laboratories accredited according to the ISO/IEC 17025 standard for electrical power and energy at industrial frequency is very important, as these measurements are the basis of the commercial relations between an electricity supplier and a user. An effective technical surveillance requires the execution of inter-laboratory comparisons (ILCs). With them, it is possible to verify the competence of the laboratories and the correctness of the dissemination process from the national standards of power and energy, usually maintained at national metrology institutes, to these laboratories. The paper deals with the ILCs that the National Institute of Metrological Research (INRIM) provided and carried out as reference measurements provider for Italian accredited laboratories for power and energy (active and reactive) at industrial frequency. The ILCs were carried out involving various instrument types and at different uncertainty levels. The 2σ relative uncertainties of the INRIM calibrations ranged from 1.0 × 10−4 to 1.5 × 10−3. The ILCs had satisfactory results confirming the correctness of both the dissemination from INRIM and the accreditation process by the Italian accreditation body for calibration laboratories.

Comparison of the uncertainties of several European low-dose calibration facilities

The typical uncertainty of a low-dose rate calibration of a detector, which is calibrated in a dedicated secondary national calibration laboratory, is investigated, including measurements in the photon field of metrology institutes. Calibrations at low ambient dose equivalent rates (at the level of the natural ambient radiation) are needed when environmental radiation monitors are to be characterised. The uncertainties of calibration measurements in conventional irradiation facilities above ground are compared with those obtained in a low-dose rate irradiation facility located deep underground. Four laboratories quantitatively evaluated the uncertainties of their calibration facilities, in particular for calibrations at low dose rates (250 nSv/h and 1 μSv/h). For the first time, typical uncertainties of European calibration facilities are documented in a comparison and the main sources of uncertainty are revealed. All sources of uncertainties are analysed, including the irradiation geometry, scattering, deviations of real spectra from standardised spectra, etc. As a fundamental metrological consequence, no instrument calibrated in such a facility can have a lower total uncertainty in subsequent measurements. For the first time, the need to perform calibrations at very low dose rates (< 100 nSv/h) deep underground is underpinned on the basis of quantitative data.

Comparison of methods for H*(10) calculation from measured LaBr3(Ce) detector spectra

The Universitat Politecnica de Catalunya (UPC) and the Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT) have evaluated methods based on stripping, conversion coefficients and Maximum Likelihood Estimation using Expectation Maximization (ML-EM) in calculating the H*(10) rates from photon pulse-height spectra acquired with a spectrometric LaBr3(Ce)(1.5″ × 1.5″) detector. There is a good agreement between results of the different H*(10) rate calculation methods using the spectra measured at the UPC secondary standard calibration laboratory in Barcelona. From the outdoor study at ESMERALDA station in Madrid, it can be concluded that the analysed methods provide results quite similar to those obtained with the reference RSS ionization chamber. In addition, the spectrometric detectors can also facilitate radionuclide identification.

Accurate comparison between INRIM and a secondary calibration laboratory using a top-class multifunction electrical calibrator

Abstract An accurate inter-laboratory comparison (ILC) concerning the electrical quantities in low frequency between the laboratory for the calibration of multifunction electrical instruments of the National Institute of Metrology Research (INRIM) and a secondary high level electrical calibration laboratory was performed with satisfactory results. The instrument involved in the ILC was a top class multifunction electrical calibrator, chosen for its wide measurement fields and its excellent definability requiring therefore very small uncertainties to calibrate it. This ILC was the first high accuracy comparison exercise at INRIM involving a grid of about one hundred and thirty measurement points. The ILC allowed to check adequately the measurement capabilities, techniques and uncertainties of this secondary laboratory. Attention was paid to evaluate the correlated terms between the two laboratories measurements. The calibrator showed high stability and resulted more appropriate than fixed standards or than a 8.5 digits multimeter to the aim of the ILC.

Analysis of a national comparison in the field of electrical low dc resistance

In this paper a measurements comparison between the National Institute of Metrological Research (INRIM), acting as pilot Laboratory, and nineteen Italian Secondary Calibration Laboratories in the field of low dc Electrical Resistance is presented and discussed. This comparison was carried out on commission by the Italian Accreditation Body of Calibration Laboratories ACCREDIA-DT. As traveling standards three Tinsley mod 3504C four terminal standard resistors to be calibrated in oil respectively at 5A and 20A (1mΩ), 1A and 5A (10mΩ), 0.1A and 1A (100mΩ) were involved. The temperatures at the measurements thermal regimen allowed a correction at 23°C of the results. The comparison results, shown graphically and as distribution of the normalized errors, were satisfactory, except in the case of a Laboratory whose measurements were outside its accreditation field.

The New Kilogram Definition and its Implications for High-Precision Mass Tolerance Classes.

The SI unit of mass, the kilogram, is the only remaining artifact definition in the seven fundamental units of the SI system. It will be redefined in terms of the Planck constant as soon as certain experimental conditions, based on recommendations of the Consultative Committee for Mass and Related Quantities (CCM) are met. To better reflect reality, the redefinition will likely be accompanied by an increase in the uncertainties that National Metrology Institutes (NMIs) pass on to customers via artifact dissemination, which could have an impact on the reference standards that are used by secondary calibration laboratories if certain weight tolerances are adopted for use. This paper will compare the legal metrology requirements for precision mass calibration laboratories after the kilogram is redefined with the current capabilities based on the international prototype kilogram (IPK) realization of the kilogram.

Inter-laboratories comparison at 100 GΩ and 1 TΩ level to evaluate the traceability transfer from INRIM in the field of high dc resistance

A National inter-laboratories comparison of dc resistance at 100GΩ and 1TΩ among the National Institute of Metrological Research (INRIM) and eight Secondary Electrical Calibration Laboratories was carried out in 2010. All the involved Laboratories made their measurements with a method based on a Multifunction Calibrator (MFC) and on a digital multimeter (DMM), both used in their dc voltage function.These and other Secondary Electrical Laboratories are traceable to National Standards by means of the calibration at INRIM of a complete set of primary standards or, alternatively, by means of the calibration of a high accuracy DMM or of a Multifunction Transfer Standard (MTS) or of few primary standards. All the relative differences between each Laboratory’s value and its reference value obtained in the comparison were within their relative expanded uncertainties. This result showed that the traceability transfer methods from INRIM to Electrical Secondary Laboratories lead to satisfactory results in the field of high dc resistance.

SU‐EE‐A2‐04: Traceability to National Measurement Standards for Electronic Brachytherapy Calibrations

Purpose: To establish a primary air‐kerma standard for the Xoft miniature x‐ray brachytherapy source. Method and Materials: A new calibration facility has been designed at the National Institute of Standards and Technology (NIST) to directly realize air kerma from electronic brachytherapy sources operated up to 50 kV. The previously established primary x‐ray standard, the Lamperti free‐air ionization chamber, has been dedicated for this measurement capability. The spectrum emergent from the source is measured with a high‐purity germanium spectrometer. To account for possible anisotropy of emissions from the source, both the free‐air chamber and the spectrometer are rotated about the long axis of the source. Well‐chamber measurements are also performed to study the variability in the ratio of well‐chamber current to air‐kerma rate in anticipation of developing a method for transferring the NIST standard to secondary calibration laboratories and/or therapy clinics. Results: Comparisons of the air‐kerma rate realized by two NIST x‐ray primary standards, the Lamperti free‐air chamber (10 kV to 60 kV) and the Ritz free‐air chamber (20 kV to 100 kV), were in agreement to better than 1% as is typical for well‐established primary x‐ray standards. This comparison validated the use of the Lamperti chamber in establishing the measurement techniques required for the determination of air kerma. Conclusion: NIST has designed, constructed, and validated the experimental apparatus necessary for the measurement of air‐kerma from an x‐ray brachytherapy source using a primary standard. NIST acknowledges the support of Xoft, Inc., in this project.

Clinic based transfer of the calibration coefficient using a linear accelerator

Ionization chambers used for reference dosimetry require a local secondary standard ionization chamber with a absorbed dose to water calibration coefficient traceable to a national primary standards dosimetry laboratory or an accredited secondary dosimetry calibration laboratory. Clinic based (in‐house) transfer of this coefficient to tertiary reference ionization chambers has traditionally been accomplished with chamber cross calibration in water using a beam; however, access to teletherapy machines has become increasingly limited for clinic based physicists. In this work, the accuracy of alternative methods of transferring the calibration coefficient using 6 and 18 MV photon beams from a linear accelerator in lieu of has been investigated for five different setups and four commonly used chamber types.

Radiation dose reduction in direct digital panoramic radiography

Objectives (a) To measure the absorbed radiation doses at 16 anatomical sites of a Rando phantom and (b) to calculate the effective doses including and excluding the salivary gland doses in panoramic radiography using a conventional and a digital panoramic device. Study design Thermoluminescent dosimeters (TLD-100) were placed at 16 sites in a Rando phantom, using a conventional, Planmeca Promax and a digital, Planmeca PM2002CC Proline 2000 (Planmeca Oy, 00880 Helsinki, Finland) panoramic device for panoramic radiography. During conventional radiography the selected exposure settings were 66 kVp, 6 mA and 16 s, while during digital radiography two combinations were selected 60 kVp, 4 mA, 18 s and 66 kVp, 8 mA, 18 s with and without image processing function. The dosimeters were annealed in a PTW-TLDO Harshaw oven. TLD energy response was studied using RQN beam narrow series at GAEC's Secondary Standard Calibration Laboratory. The reader used was a Harshaw, 4500. Effective dose was estimated according to ICRP 60 report ( E ICRP60). An additional estimation of the effective dose was accomplished including the doses of the salivary glands ( E SAL). A Wilcoxon signed ranks test was used for statistical analysis. Results The effective dose, according to ICRP report ( E ICRP60) in conventional panoramic radiography was 17 μSv and E SAL was 26 μSv. The respective values in digital panoramic radiography were E ICRP60 = 23 μSv and E SAL = 38 μSv; while using the lowest possible radiographic settings E ICRP60 was 8 μSv and E SAL was 12 μSv. Conclusions The effective dose reduction in digital panoramic radiography can be achieved, if the lowest possible radiographic settings are used.

Sapphire Whispering Gallery Thermometer

An innovative sapphire whispering gallery thermometer (SWGT) is being explored at the National Institute of Standards and Technology (NIST) as a potential replacement for a standard platinum resistance thermometer (SPRT) for industrial applications that require measurement uncertainties of ≤ 10 mK. The NIST SWGT uses a synthetic sapphire monocrystalline disk configured as a uniaxial, dielectric resonator with whispering gallery modes between 14 GHz and 20 GHz and with Q-factors as large as 90,000. The prototype SWGT stability at the ice melting point (0°C) is ≤ 1 mK with a frequency resolution equivalent to 0.05 mK. The prototype SWGT measurement uncertainty (k= 1) is 10 mK from 0°C to 100°C for all five resonance modes studied. These results for the SWGT approach the capabilities of industrial resistance thermometers. The SWGT promises greatly increased resistance to mechanical shock relative to SPRTs, over the range from −196°C to 500°C while retaining the low uncertainties needed by secondary calibration laboratories. The temperature sensitivity of the SWGT depends upon a well-defined property (the refractive index at microwave frequencies) and the thermal expansion of a pure material. Therefore, it is expected that SWGTs can be calibrated over a wide temperature range using a reference function, along with deviations measured at a few fixed points. This article reports the prototype SWGT stability, resolution, repeatability, and the temperature dependence of five whispering gallery resonance frequencies in the range from 0°C to 100°C.

A Current Source for Picoammeter Calibration

A current source, which is to be employed in the calibration of low-current meters (picoammeters and electrometers), is presented here. The output current range is 100 fA to 100 pA and is directly traceable to calibrated standards of dc voltage, capacitance, and time period. The source is based on a low- frequency (ap1 mHz) trapezoidal signal generator, which charges and discharges a gas-dielectric capacitor; the voltage is monitored with a voltmeter that is triggered by a precision time base. The source has been employed during March 2006 for the Italian participation to the supplementary comparison EUROMET.EM-S24 and will be part of an extension of the Italian national standard of dc current. However, being composed of low-cost electronics and common commercial instrumentation, the source can also find useful application in secondary calibration laboratories.

Inter-comparison among different TLD-based techniques in a standard multisphere assembly for the characterisation of neutron fields

In the framework of collaboration among the ENEA Radiation Protection Institute (Bologna), the ENEA Fusion Department (Frascati) and the INFN-LNF-Radiation Protection Group (Frascati), an experimental campaign was organised on the usage of thermoluminescence dosemeters (TLDs) for the dosimetric and spectrometric characterisation of neutron fields. Commercially available TLDs of different material and different sensitivity to photons and thermal neutrons were selected, namely TLD600H and TLD700H from Harshaw, GR206 and GR207 from SSDML (China), MCP-6s from TLD Poland. The detectors were first calibrated in standard fields of photons ((60)Co) and thermal neutrons at the ENEA-IRP Secondary Standard Calibration Laboratory of Bologna, then exposed in fast neutron standard fields of different energy, using a standard multisphere moderating assembly. The paper compares the dosimetric characteristics of the studied TL detectors, underlining the (n-gamma) discrimination capability, and discusses their spectrometric performances addressed to radiation protection applications.

Uncertainties evaluation for electrets based devices used in radon detection

In recent years uncertainty evaluation in measurements has achieved great importance. National and international standards offer guidelines to evaluate uncertainties, but these procedures are, until now, not well understood by the operators. This is because of the fact that a detailed uncertainty evaluation is not an easy operation and a standard rule to apply in all cases is not available. Every measurement procedure has its own uncertainty evaluation. In this work, attention is focused upon the electret ion chambers (EIC), widely used in radon concentration measurements. Measurements of gamma radiation sensitivity are performed in a secondary standard calibration laboratory and measurement of radon concentration sensitivity is performed in a radon chamber 0.8 m3 in volume. Raw data are analysed to evaluate the calibration factors and the combined uncertainties are determined. The aim of the work is to give a practical method to assess the uncertainty of a radon measurement.

Characterization of a new alanine film dosimeter: relative humidity and post-irradiation stability

The alanine dosimetry system is now preferred by all primary and secondary calibration laboratories for their high-dose ionizing radiation calibration services. Alanine dosimeters in the form of cylindrical pellets have been available in commercial quantities for several years. Despite their high quality, the physical dimensions of the dosimeter were not suitable for many electron-beam processing dosimetry applications. Alanine in the form of a thin-film would be more appropriate for electron-beam applications. However, a reliable manufacturer/supplier for high-quality alanine film dosimeters was lacking. To fill this void Bruker BioSpin and Kodak have teamed up to successfully develop an alanine film dosimeter that appears to have excellent dose measurement properties in a highly robust form. Described here are the characterization studies for this new dosimeter that assess the effects of relative humidity and the post-irradiation temporal stability of the alanine film dosimeter.