National Measurement Laboratory Research Articles

Extended channel characterization of the low-cost sampling devices for the application in high-precision electric power measurement

The paradigm of low-cost metrology implies the application of low-cost measuring devices in order to achieve satisfactory precision of the relevant measuring quantities. This is particularly important in underdeveloped countries where it is necessary to improve their metrology capabilities to ensure satisfactory standards for industry requirements. Therefore, the previously published conference paper is extended, and the performance of low-cost sampling devices is investigated for the purpose of high-precision electricity measurement in relevant national metrology institutes or measurement laboratories. The performance of the DMM 3000 device and the DAQ970A digitizers compared with high-resolution (24-bit) ADC-based sampling devices such as the NI PXI 5922 and NI PXI 4461. One of the main contributions of this article is the characterization of the channels of the low-cost digitizers in sinusoidal and non-sinusoidal regimes along with the uncertainty analysis using Monte Carlo method which has been carried out as well.

Preface

11th Brazilian Congress on Metrology (Metrologia 2021) The Metrology 2021 congress was held from October 18th to 21st, 2021. It was a remote event, with all activities done in virtual rooms. The general president of Metrology 2021 was Americo Bernardes, president of the Brazilian Society of Metrology and professor at the Federal University of Ouro Preto.Metrology 2021 Magna session was the lecture Dr. Claire M. Saundry (NIST) gave on the first day, October 18th. Dr. Saundry spoke about the main activities of the Interamerican Metrology System (or “Sistema Interamericano de Metrologia” – SIM) regarding capacity building and knowledge transfer.Following the Magna session, on the morning of October 18th, the work began with the plenary lecture given by Dr. Daniel Varela Magalhães from the Mechanical Engineering Department at USP. The speaker gave a general outline of the new edition of the International Vocabulary of Metrology (VIM).Further after, on the afternoon of October 18th, two virtual rooms were held in parallel with the sessions related to CBM (general metrology) and CBMRI (ionizing radiations). CBMRI sessions also featured four thematic discussions on specific topics of interest.The second day of the congress, October 19th, started with the lecture of Dr. Thomas Hartung from the Johns Hopkins Bloomberg School of Public Health. He spoke about assessing the health effects of drugs and chemicals, which is considered a scientific revolution and a critical application of Metrology in the Health Area. Continuing in the Health area, Dr. Cameron Miller from NIST presented his lecture on documentary standards and the development of measurement methods for UV disinfection technologies. The plenary lectures were closed by Dr. Renato Garcia from UFSC, who spoke about quality programs in medical equipment used in primary health care, specifically about post-market safety and performance trials.Later, on the afternoon of October 19th, two virtual rooms were held in parallel sessions related to CBM (general metrology) and CBMO (optical metrology).The third day of the congress started with an exciting round table about female researchers’ presence in ionizing radiations. A plenary lecture by Stephane Solve from the “Bureau International de Poids et Mesures” (BIPM) Radiometry-Photometry group followed. The main subject was an extension of the BIPM on-site primary voltage standards comparisons to AC voltages, an important topic in Electrical Metrology. Further on, the morning works ended with a round table about Metrology in Health, featuring Renata Souza from FIOCRUZ and Roberto Macoto Ichinose from the Biomedical Engineering of COPPE/UFRJ.The afternoon of the third day started with two virtual rooms that held parallel sessions related to SEMETRO (electrical metrology) and to CIMMEC (mechanical metrology). Later on, there was another round table about Metrology in Health, specifically about metrological traceability of laboratory tests, with lectures by Dr. Marcelo Medeiros from INMETRO, Debora Michele Morone D’Aiuto from FIOCRUZ, Rafael Monsores from the company CONTROLLAB and MD Luisane Maria Falci Vieira, manager of the laboratory Álvaro Apoio.The event’s last day, October 21st, started with a plenary lecture by Dr. Jim Huggett from National Measurement Laboratory (NML), talking about the role of measurement science in supporting a molecular diagnosis of SARS-COV-2, a very current and hot topic. A vivid discussion on Metrology Education followed the plenary lecture.The afternoon of the last day started with two virtual rooms that held parallel sessions related to REMEQ (chemical metrology) and CBM (general metrology). Later, round tables were held in the two parallel virtual rooms, discussing hot topics such as metrological traceability, quality control on COVID-19 diagnostics, alternative methods applied to toxicology, and a web app developed for the performance evaluation of laboratories.Metrologia 2021 disclosed about 170 articles. After the second round of revision, the editorial committee selected the best 35 to be published by IOP JPCS.Metrology 2021 had sponsors from the industrial sector (Fluke Calibration and Sartorius do Brasil (Gold sponsors) and institutional support (ARBB Consultoria em Metrologia e Qualidade, RMMG, Canal Metrologia, REDE, SBLUZ and GM Metrologia). The event’s next edition will be face-to-face in 2023, from 28th to 30th November, in Itaipava, a gorgeous area belonging to the “Imperial City” of Petrópolis, Rio de Janeiro state. You are all welcome to join us! Rio de Janeiro, RJ, Brasil, August 28th, 2023. List of Editorial committee, Organizing committee are available in this Pdf.

Applying uncertainty analysis to assess the variation of operator performance when manually gating Flow Cytometry data

Background & Aim The use of Flow Cytometry (FC) for cell identification and counting is prevalent within the biomanufacture of Advanced Therapy Medicinal Products (ATMPs) both in clinical centres and biomanufacturing facilities. Operators involved in the use of FC and the analysis of the resultant datasets have the option of manually gating cell clusters or using a range of automated software platforms (supplied by FC instrument manufacturers, or third party). It is well known that many operators prefer to manually gate on the basis of speed and simplicity, however with increasing data complexity (especially when dealing with multi-colour FC instruments) there is significant potential for variation in final cell count to increase as a function of operator subjectivity. Understanding this relationship between increasing data dimensionality and operator subjectivity during manual gating techniques is important because it allows process facilities to comprehend and quantify the potential for process error as a function of incorrect measurement data. This research has specifically considered how uncertainty analysis can be used to better define operator variation over and beyond traditional measures such as the Coefficient of Variation (CV), where CV is typically only representative of the final gating process and does not provide resolution of understanding at each gating step. Methods, Results & Conclusion Three stages of cell model complexity were designed and trialled (3, 5 and 8 step), measuring variation in manual gating sequence steps to obtain a target cell population, with operators selected from academic and industrial research, and national measurement laboratory process team environments. Increasing operator variation was found as a function of increasing FC data complexity. When considering 3 step, 5 step and 8 step FC analysis, operator CV was found to range from 6% to 57% (3 step to 8 step data respectively). At the same time uncertainty analysis was applied to each gating analysis step providing clear definition of variation at each step allowing the generation of inter- and intra-operator variation statistics. Resultant combined uncertainty statements expressed at a one sigma coverage factor (67%) showed variation from 12% (3 step data) through to 34% (8 step data). Process improvement for manually gated FC analysis can therefore take advantage of this more detailed variation analysis framework and provides a benchmark for future comparison with FC automated software platforms.

Clinical application of ionization density dependence of the glow curve for measuring linear energy transfer in therapeutic proton beams

Linear energy transfer (LET) is related to the relative biological effect caused by particle therapy. LET is a candidate parameter for optimizing proton therapy treatment plans by considering the biological effects. Therefore, being able to measure LET in clinical sites has become crucial. The purpose of this study was to develop a feasible LET measurement system for clinical therapeutic proton therapy by using the ionization density dependence of the heating-induced fluorescence (LiF):Mg,Ti glow curve in the high-temperature region. The integrated thermoluminescent (TL) intensity over the specified high-temperature region after exposure to a proton beam was divided by that after exposure to a photon beam to obtain the high-temperature ratio (HTR). The relationship between the HTR and LET was determined. TL dosimeters (TLDs) were irradiated with the same dose at several depths of a water phantom using three types of radiation: a60Co gamma source at the National Measurement Laboratory of the Institute of Nuclear Energy Research, a 6-MV photon beam, and a 190-MeV proton beam at Chang Gung Memorial Hospital. The LET dependence on depth was simulated using a Monte Carlo code called TOPAS (version 3.0.1). The LET values ranged from 1 to 10 keV/μm in estimations using LiF:Mg,Ti for a proton beam. The LET measurement system was developed by comparing TL signals caused by proton beams with those caused by 60Co gamma rays or 6-MV X-rays. A system incorporating Linac X-rays would be most convenient for the majority of hospitals. Therefore, TLDs can not only be dosimeters but also LET detectors in proton therapeutic sites.

Proficiency testing in analytical chemistry, microbiology and laboratory medicine: discussions on current practice and future directions

A summary of the working group discussions on proficiency testing (PT) and external quality assessment (EQA) held at the Eurachem Workshop, Berlin, Germany, 6–9 October 2014 is provided. The working groups covered a range of issues concerned with current practice and future directions: review of ISO/IEC 17043; user perspective of PT/EQA; sampling PT/EQA; the revised ISO 13528; PT/EQA in developing countries; and harmonisation of performance assessment in qualitative PT/EQA. Delegates from 64 countries attended the workshop, and this diversity of different backgrounds was represented on each of the working groups in order to capture a range of views and experience from a number of different measurement sectors. Working group representatives included PT/EQA providers, participants in PT/EQA schemes, end-users of PT/EQA results such as accreditation bodies and regulatory authorities, national measurement institutes, laboratory associations, universities and independent consultants from countries around the world.

A study of quantum Hall devices with different working magnetic fields for primary resistance metrology

Two kinds of quantum Hall devices with different working magnetic fields are fabricated and compared with the LEP (Laboratoires d’Electronique Philips) device, which is currently used in the primary resistance standard system of the National Institute of Metrology (NIM) of China. The comparison is made by calibrating the same 1 Ω standard resistor made by the National Measurement Laboratory of Australia using a Tinsley 100 Ω resistor as the intermediate standard and a cryogenic current comparator. The calibrated values from the NIM device with high working magnetic field and those from the LEP device agreed to within −0.69 × 10−9 with an uncertainty of 4.9 × 10−9. The values from the NIM device with low working magnetic field and those from BIPM-2 agreed to within 2.5 × 10−9 with an uncertainty of 7.1 × 10−9.

The equilibrium liquidus temperatures of rhenium–carbon, platinum–carbon and cobalt–carbon eutectic alloys

The eutectic alloys rhenium–carbon, platinum–carbon and cobalt–carbon have been proposed as reference standards for thermometry, with temperature and uncertainty values specified within the mise en pratique of the definition of the kelvin. These alloys have been investigated in a collaboration of eleven national measurement institutes and laboratories. Published results reported the point-of-inflection in the melting curve with extremely low uncertainties. However, to be considered as standards it is necessary to stipulate what phenomenon a temperature value has been ascribed to; specifically, this should be a thermodynamic state. Therefore, the data have been further evaluated and the equilibrium liquidus temperatures determined based on a consideration of limits and assuming a rectangular probability distribution. The values are: for rhenium–carbon 2747.91 ± 0.44 K, for platinum–carbon 2011.50 ± 0.22 K and for cobalt–carbon 1597.48 ± 0.14 K, with uncertainties at approximately a 95% coverage probability. It is proposed that these values could be used as the basis of thermodynamic temperature measurement at high temperatures (above 1300 K).

PRELIMINARY RESULTS OF BTDF CALIBRATION OF TRANSMISSIVE SOLAR DIFFUSERS FOR REMOTE SENSING.

Satellite instruments operating in the reflected solar wavelength region require accurate and precise determination of the optical properties of their diffusers used in pre-flight and post-flight calibrations. The majority of recent and current space instruments use reflective diffusers. As a result, numerous Bidirectional Reflectance Distribution Function (BRDF) calibration comparisons have been conducted between the National Institute of Standards and Technology (NIST) and other industry and university-based metrology laboratories. However, based on literature searches and communications with NIST and other laboratories, no Bidirectional Transmittance Distribution Function (BTDF) measurement comparisons have been conducted between National Measurement Laboratories (NMLs) and other metrology laboratories. On the other hand, there is a growing interest in the use of transmissive diffusers in the calibration of satellite, air-borne, and ground-based remote sensing instruments. Current remote sensing instruments employing transmissive diffusers include the Ozone Mapping and Profiler Suite instrument (OMPS) Limb instrument on the Suomi-National Polar-orbiting Partnership (S-NPP) platform,, the Geostationary Ocean Color Imager (GOCI) on the Korea Aerospace Research Institute's (KARI) Communication, Ocean, and Meteorological Satellite (COMS), the Ozone Monitoring Instrument (OMI) on NASA's Earth Observing System (EOS) Aura platform, the Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument and the Geostationary Environmental Monitoring Spectrometer (GEMS).. This ensemble of instruments requires validated BTDF measurements of their on-board transmissive diffusers from the ultraviolet through the near infrared. This paper presents the preliminary results of a BTDF comparison between the NASA Diffuser Calibration Laboratory (DCL) and NIST on quartz and thin Spectralon samples.

Cryogenic Current Comparators for the Realisation of Electrical Quantum Standards

The cryogenic current comparator has played a central role in the realisation of electrical quantum standards over the last 40 years. It is the method of choice for National Measurement Laboratories in realising a quantum Hall effect primary standard of resistance. Single electron transport devices are expected to provide a primary standard of current within the next few years and this paper considers how they will be integrated into electrical metrology.

The set up of primary calibration system for shock acceleration in NML

This paper mainly describes Taiwan’s metrology National Measurement Laboratory (NML) to set up and evaluate a shock accelerometer calibration system which follows the ISO 16063-13:2001 standard. The environmental shock testing of electro-acoustics or electronic spare parts, the product packing falling impact, the automobile collision and the helmet impact test and so on are more and more important for quality and safety. In consideration of that, NML has started to establish the primary shock calibration system which calibrates the accelerometer sensitivity and trace to the metric unit since 2009. The shock machine structure comprises three parts; they are the electromagnetic high-speed hammer, airborne hammer and airborne anvil. The shock machine impact source of primary shock calibration system is excited by electromagnetic method.The electromagnetic controller inputs a DC voltage to drive electromagnetic high-speed hammer through the DC power source supply. Then the electromagnetic high-speed hammer impacts an airborne hammer, after that, the airborne hammer proceed to impact the PU rubber which is fixed on the end surface of airborne anvil with rigid body motion way. An accelerometer which is mounted on the other end surface of anvil will output the voltage signal during the instantaneous impact. According to different input DC voltage value and different hardness rubber accelerometer will produce different acceleration and duration time. At the same time the accelerometer displacement is measured by combination of modified Michelson and Mach–Zehnder interferometer and acceleration of the accelerometer is derived through two numerical differentiations and two low-pass digital filtering from the displacement.At present the acceleration capability of primary shock calibration system is from 200m/s2 to 5000m/s2, the shock pulse duration time is less than 3ms. The final evaluated relative expanded uncertainty is less than 1.0% within coverage factor k=1.96. We shall continue to improve and expand the system acceleration from 100m/s2 to 10,000m/s2 for various customers in the future.

Thermodynamic Temperature Measurements Traceable to Photometric Standards

The replacement of ITS-90 temperature measurements by direct thermodynamic temperature measurements based on radiometric techniques in the temperature range above 1000 °C has been proposed by many national measurement laboratories. This article reports on work at NMIA to develop a simple and robust traceability scheme for thermodynamic temperature, based on the use of photometers and a Thermogage furnace with a graphite tube element modified to improve its temperature uniformity and emissivity. A simple luminance meter was constructed using a commercial photometer and pairs of precision apertures to view the rear of the blackbody cavity. This photometer was calibrated against NMIA reference illuminance lamps, and relative spectral responsivity measurements were used to determine the color-temperature correction between the lamps and the Thermogage blackbody. Thermodynamic temperature determinations made using various combinations of apertures and photometers showed a range of less than 0.2 °C at 1700 °C, consistent with the calculated uncertainty of 0.29 °C (k = 2). ITS-90 measurements made by NMIA’s LP5 and HTSP primary radiation thermometers with an uncertainty of 0.16 °C (k = 2), are consistent with the thermodynamic measurements. It is suggested that routine thermodynamic temperature determinations can now be made with an effort comparable to that required to realize the ITS-90 above 1000 °C.

Practical interpretation of metrological traceability on gauge block as to VIM 3

In ISO/IEC Guide 99:2007, i.e. the International Vocabulary of Basic and General Terms in Metrology-3rd edition (VIM 3), the term “traceability” is replaced by “metrological traceability”, giving it a new definition as property of a measurement result which can be related to a reference. In essence, “metrological traceability” can offer an evidence of measurands tracing to the primary standards which can realize the SI units, and offer a documented unbroken chain of calibrations, thus considered as one of the most important terms in VIM 3. National Measurement Laboratory (NML, Chinese Taipei) has long operated its main mission of calibration implemented along with peer assessed traceability of its measurement systems, which demonstrate a calibration hierarchy conventionally in schematic approach. In dealing with definition of the new term “metrological traceability” in VIM 3, this paper elaborates in taking additionally a newly mathematical approach rather than schematic approach only to realize the practical interpretation of “metrological traceability” to show how the unbroken calibration chain is functioning seamless and robust on the gauge block measurement system in NML. Through such study activities, we well assure our strong confidence on technology inheritance of gauge block and the other measurement systems with sufficient metrological know-how in NML, which can continually pass to each entry level metrologist.

Prediction of vibrations induced by trains on line 8 of Beijing metro

This paper mainly discusses the problem of ground-borne vibrations due to the planned line 8 of Beijing metro which passes under the National Measurement Laboratory. A lot of vibration sensitive equipments are placed in the laboratory. It is therefore necessary to study the impact of vibrations induced by metro trains on sensitive equipments and important to propound a feasible vibration mitigation measure. Based on the coupled periodic finite element-boundary element (FE-BE) method, a 3D dynamic track-tunnel-soil interaction model for metro line 8 has been used to predict vibrations in the free field induced by trains running at variable speeds between 30 km/h and 80 km/h. Four types of track structures commonly used on the Beijing metro network have been considered: (1) high resilience direct fixation fasteners, (2) Vanguard fasteners, (3) a floating slab track and (4) a floating ladder track. For each of these track types, the vibration isolation efficiency has been compared. The results of the numerical study can be used to predict vibrations in nearby buildings and to decide upon effective vibration countermeasures.

Clarifying the Relationship between Quality of Global Positioning System Data and Precision of Positioning

This study selected five indexes to determine the relationship between data quality and positioning precision. These indexes are multipath on L1, multipath on L2, observations by cycle slips, clock offset, and clock stability. To reduce the number of common errors, six types of global positioning system (GPS) receivers are selected and set up in an Ultra-Short Distance Network at the National Measurement Laboratory, Taiwan, for 3 days. The first three indicators are calculated with the Teqc software, and the last two indicators are computed using the Bernese software. Moreover, the observations from three GPS tracking stations, namely, short baseline (about 25 km), middle baseline (about 150 km), and long baseline (around 2000 km), were downloaded from the Internet and processed using Bernese software. Analytical results indicate that clock stability and observations divided by cycle slips are found to be very important positioning factors. Clock offset and multipath effects do not significantly affect th...

Identifying the degraded environment and bad receivers setting by using the GPS data quality indices

To ensure the accuracy of positioning, an accurate and efficient system for calibrating the Global Positioning System (GPS) receivers must be constructed, especially when thousands of GPS tracking stations around the world are established for a variety of applications. In Taiwan, an auto-analytical system for analysing data quality is already established to monitor the GPS stations. However, the relationships between the data quality and positioning precision are not clearly addressed yet, and this is the main goal we want to achieve. In this study, six indices are chosen to characterize the relationship between the data quality and GPS positioning precision. They are the number of observations, multipath on L1, multipath on L2, occurrence of cycle slips, relative frequency offset and frequency instability. To reduce common errors, fourteen types of GPS receivers were selected and set up at an Ultra-Short Distance Network of NML (National Measurement Laboratory, Taiwan) in the years 2002, 2003 and 2004. The results of this study indicate that the frequency instability is the most critical factor among the six indices of interest to influence the GPS positioning precision. The frequency instability may cause a positioning difference of as much as 17.5 mm in the precision of three-dimensional coordinates. The second and third most critical error sources are the number of observations and the multipath effect, respectively, with a maximum difference of 10.7 mm. In contrast, for the method of parameter estimation, the cycle slips and relative frequency offset have minor effects on positioning precision with a few occasional exceptions. The findings of this study will serve as a crucial indicator to classify the positioning error of the tracking stations for long term analysis.

Establishing an invar leveling calibration system

Precise height systems are widely utilized in civil engineering projects such as high‐speed railroads, and highways and bridge construction. However, highly precise height data is obtained using precise leveling. An extremely precise invar leveling rod is necessary for obtaining precise results. In this study, an automatic calibration system for invar leveling has been established by the National Measurement Laboratory (NML). The content belongs to the long scales calibration system of D17 of the NML. This system utilizes a steady frequency laser interferometer, a CCD microscopic monitor, and a precise moving mechanism. With this system, an invar rod and a mark invar leveling rod are applied to estimate uncertainty with a 95% confidence level. Uncertainty results are 22 μm and 21 μm for the invar leveling rods and mark invar leveling rods, respectively.

Traceability in nuclear medicine

Accurate, reproducible measurement of radioactivity in nuclear medicine applications is vital to ensure the safety and effectiveness of disease diagnosis and treatment using unsealed radioactive sources. The need to maintain a high degree of confidence in those measurements requires that they be carried out so as to be traceable to national and international standards. In addition, measurement traceability for radioactivity in medicine helps ensure international consistency in measurement at all levels of practice (national measurement laboratories, research institutions, isotope producers, radiopharmaceutical manufacturers and clinics). This paper explores the importance of radioactivity measurement in nuclear medicine and demonstrates how traceability can be extended from international standards to the quantity of the drug administered to the patient.

Application of the CIPM MRA to radionuclide metrology

The adoption of the Mutual Recognition Arrangement by the CIPM in 1999 had an almost immediate affect on the approach national measurement laboratories took in the measurement of radioactivity and how their abilities in radionuclide metrology were relayed to customers and stakeholders. In order to meet the need presented by the CIPM MRA for validated claims to calibration and measurement capabilities, radionuclide measurement laboratories have taken an accelerated track to international comparisons and expanding quality systems, leading to a more rigorous approach to radionuclide metrology.

Construction and uncertainty evaluation of a calibration system for GPS receivers

GPS is already a main method of positioning measurement in geodesy and is applied widely in many fields. In order to maintain and ensure the accuracy of positioning, an accurate and efficient system for calibrating the GPS receivers must be established. A highly accurate GPS calibration network, tied to the ITRF coordinates of IGS stations, can be effectively used to evaluate the performance of GPS receivers. This study addresses the feasibility of establishing a system for calibrating GPS receivers and the system's traceability in metrology. Uncertainties of the GPS calibration networks were established and maintained by NML (National Measurement Laboratory, Taiwan). Furthermore, the networks are evaluated based on the method suggested by the ISO (International Organization for Standardization). The uncertainties of NML network coordinates are obtained and used as a basis for calibration. The results of the slope distances between pillars measured by the GPS processing units and the precise EDM units are discussed. Analytical results indicate that the 3D expanded uncertainty of the main station TNML of the network in the ITRF system is around 33.2 mm at the 95% confidence level. The 3D expanded uncertainties of the calibration points of the ultra-short distance network and the short distance network are evaluated to be about 2.2 mm and 3.4 mm, respectively in relation to the main station TNML at the 95% confidence level. The precision of the NML network coordinates suffices to calibrate the geodetic and navigational GPS receivers of regional users and is available through the Internet.

Final report on the key comparison CCAUV.A-K3

This is the final report for key comparison CCAUV.A-K3 on the sensitivity calibration of laboratory standard microphones in the frequency range from 31.5 Hz to 31.5 kHz. Fifteen national measurement laboratories took part in this key comparison and the Centro Nacional de Metrología (CENAM), Mexico, piloted the project with the assistance of the Danish Primary Laboratory for Acoustics (DPLA), Denmark. Four travelling standard microphones were circulated to the participants in two loops linked through the measurements of the CENAM and the DPLA. The participants' results in the form of sensitivity measurements (dB re 1 V/Pa) and full uncertainty budgets were collected throughout the project. Reference values for all four standard microphones have been calculated using a linear least squares minimization method. The differences between measurements and references have been averaged to obtain the degrees of equivalence per laboratory and interlaboratory. The deviations are all below 0.1 dB, except at 31.5 kHz. A frequency of 1000 Hz has been chosen to illustrate the degrees of equivalence. In all cases, the deviation is smaller than the associated uncertainty.Main text.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 kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).