System Of Units Research Articles

Test-retest reliability and construct validity of Inosen’s Silat Momentum Test

Problem Statements: The kick in Pencak Silat has a magnitude called momentum, which requires a tool capable of measuring several variables based on the International System of Units (SI) in real-time. Nowadays, there are affordable and reliable sensor technologies to meet these needs. Purpose: The research aimed to design a test instrument that utilizes sensor technology to measure kick momentum in the sparring category of Pencak Silat following the applicable SI, and to test its reliability and validity. The resulting instrument is named Inosen’s Silat Momentum Test. Approach: This study followed Johnson and Nelson’s seven-test construction process. Twenty-four Pencak Silat athletes, consisting of 12 elite and 12 non-elite participants, were involved in the evaluation process. The test’s reliability was assessed by examining the correlation between the test and retest results. The construct validity test was conducted by comparing the results of the front kick tests of elite and non-elite Pencak Silat athletes. Data analysis was performed using Pearson correlation and independent t-tests using Minitab 21.4.1 software. Results: The results of the test and retest indicate a very high correlation (r = 0.923), demonstrating the consistent ability of Inosen’s Silat Momentum Test to measure kick momentum. The study found a statistically significant difference in the Inosen’s Silat Momentum Test scores (p < 0.05) between the elite fighter group (average score of 463.3 kg.m/s) and the non-elite fighter group (average score of 375 kg.m/s). The results indicate that Inosen’s Silat Momentum Test is an effective instrument for differentiating kick momentum based on fighter performance. Conclusions: Based on the findings, it is inferred that Inosen’s Silat Momentum Test is a reliable and valid instrument for measuring Pencak Silat kick momentum according to SI standards. Keywords: biomechanics, kick momentum, pencak silat, performance test, sensor technology.

Measuring the purity of organic chemicals: general approaches and development of an appropriate procedure for research of pure organic chemicals

Pure materials are in demand in many sectors of the national economy, including the metrological service. High purity organic material is the ultimate source of metrological traceability in organic analysis to the basic units of the International System of Units (SI). This article presents the general approaches to determining the mass fraction of the main component in pure organic chemicals, which provide a traceable connection between the certified value of substance purity and the basic SI units - mass (kilogram) and amount of substance (mole), the features of using direct and indirect measurement approaches are considered, specific analytical methods that can be used for this purpose are discussed. Determining the purity of an organic material in most cases is not a plain analytical and metrological task. Solving this issue requires the relevant instrumental methods and appropriate measurement procedure, which is able to provide a comprehensive study of organic matter and guarantee the necessary accuracy of the certified value. Taking in consideration the vast diversity of organic chemicals, the determination of the purity of organic substances will never be a standardized procedure.

Magnification calibration of X-ray 3D microscopy using micro-line structures.

X-ray microscopy using computed tomography (CT) is an excellent three-dimensional imaging instrument. Three-dimensional X-ray microscopy (3DXRM) is a nondestructive imaging technique used to inspect internal and external structures in units of submicrometers or less. The 3DXRM, although attractive, is mostly used as an observation instrument and is limited as a measurement system in quantitative evaluation and quality control. Calibration is required for use in measurement systems such as coordinate measurement systems, and specific standard samples and evaluation procedures are needed. The certified values of the standard samples must ideally be traceable to the International System of Units (SI). In the 3DXRM measurement system, line structures (LSs) are fabricated as prototype standard samples to conduct magnification calibration. In this study, we evaluated the LS intervals using calibrated cross-sectional scanning electron microscopy (SEM). A comparison of the evaluation results between SEM and 3DXRM for the LS intervals provided the magnification calibration factor for 3DXRM and validated the LSs, whereby the interval methods and feasibility of constructing an SI traceability system were evaluated using the calibrated SEM. Consequently, a magnification calibration factor of 1.01 was obtained for 3DXRM based on the intervals of the LSs evaluated by SEM. A possible route for realizing SI-traceable magnification calibration of 3DXRM has been presented.

Ultra-low frequency calibration of broadband seismometers using a tilt table

Abstract The calibration of current broadband seismometers with the aim to provide traceability to the International System of Units (SI) is an active topic in the vibration metrology community. As it turns out, this exercise has its specific challenges at very low frequencies. A major problem faced at that end of the applicable frequency range, is the influence of tilt as a disturbance on the measured motion component of the sensor. In the presented work, the roles of the quantities are swapped. Tilt is used as a means of excitation of a seismometer and the rectilinear motion is considered as a disturbance, which is, however, well defined by the facilitated set-up. As it is demonstrated, this approach can be very beneficial for very low frequency calibration, and if applied correctly, it can provide a reliable link to base units of the SI.

Development of a new reference material for accurate measurements of lithium in Li-clays

Currently, there are no national and international certified reference materials (CRM) in lithium clays that can make reliable and traceable lithium measurements for the International System of Units (SI). Hence, it is necessary to have references to meet the needs in terms of mining and activities that involve the use of lithium to favor the economy derived from its multiple uses and associated benefits in the exploration, exploitation, and handling of lithium ore. In this study, a candidate for reference material (RM) of Li in clays was developed and certified based on the provisions of ISO 17034:2016 and ISO Guide 35:2017. Different mass sizes of the RM (0.05, 0.1, and 0.25 g) were used to evaluate homogeneity. An isochronous study (short-term stability) was carried out in the assessment of stability, influenced by the effects of transport at different temperatures (20, 40, and 50 °C) for a determined time of 6 weeks, in addition to a classic (long-term) study for 19 weeks. The sample was treated using microwave-assisted acid digestion and Li measurements were performed using the analytical technique of Flame Atomic Absorption Spectrometry (FAAS). The CRM is homogeneous for the sample mass sizes of 0.05 and 0.1 g, and the mass fraction of w(Li) was stable in the RM for temperatures of 20, 40, and 50 °C. The determined period of validity was 3 years.

Development of a certified reference material for D-phenylalanine with evaluation of enantiomeric purity.

D-Phenylalanine (D-Phe) is a small chiral organic molecule that is both an important pharmaceutical intermediate and used as a calibrator for quantifying amino acids in liquid chromatography-circular dichroism. We have developed a process for a national certified reference material (CRM) for D-Phe following ISO 17034:2016. The identity of D-Phe was confirmed using mass spectrometry (MS) and nuclear magnetic resonance (NMR), infrared, and ultraviolet (UV) spectroscopy. The absolute optical conformation was also determined using circular dichroism (CD) spectroscopy and optical rotation measurements. Impurities were identified via liquid chromatography (LC) with a UV-Vis detector and a charged aerosol detector (CAD) and LC-MS. Both mass balance and quantitative NMR were employed for value assessment, and the associated uncertainty was evaluated. The certified purity was determined to be 0.995 ± 0.003g/g, a validation that was confirmed by CD using L-Phe CRM as a calibrator. Twenty milligrams of raw material was packed in sealed brown glass tubes for storage, and no inhomogeneity was observed. Stability tests revealed that the D-Phe CRM remained stable at -20°C for at least 26months, at 4°C for at least 14days, and at 25°C and 60°C for at least 7days. The D-Phe CRM can be used to ensure the accuracy and reliability of D-Phe quantitation in the pharmaceutical field and also as a calibrator to ensure traceability to the International System of Units (SI) for L-Phe quantitation and protein purity analysis using LC-CD methods. The approach outlined in this paper also has potential for use in the development of other chiral CRMs.

Proof of concept and new developments on a Kibble extension

Abstract This article describes the proof of concept of a Kibble extension for vacuum mass comparators and its further development. A Kibble extension is a technical extension for vacuum mass comparators to connect to the new definition of the International System of Units (SI) of 2019. A commercially available high-vacuum prototype mass comparator from Sartorius serves as the basis. It is used to compare kilogram prototypes, such as the international prototype kilogram ( K ) $(\mathfrak{K})$ , directly with other kilogram mass standards in order to realize a calibration chain. According to the new definition of the SI in 2019, the kilogram is defined by the Planck constant (h), therefore the Kibble extension is designed to enable high-vacuum mass comparators to be converted by technical modifications to allow mass to be realized according to the new definition. The aim is to realize kilogram prototypes and mass standards in the range from 1 mg to 1 kg according to the E1 standard of OIML R111-1 (2004). Initial measurement results with a prototype of the Kibble extension are presented and evaluated. Based on the experience gained, a lightweight magnet system developed with the use of simulation methods is presented. This is intended to contribute to the further development of the Kibble extension.

Metrology for sensor networks: metrological traceability and measurement uncertainties for air quality monitoring

Abstract In situ calibration of sensors delivering SI traceable measurement results still provides an open question to the design and operation of sensor networks. Particularly when addressing low-cost sensors, currently, the use of sensor networks for air quality monitoring is limited by the low or unknown accuracy of measurements that they can achieve, while the data quality of individual sensor networks is mainly derived by algorithms. Standardization bodies like DIN and CEN therefore announced the need for investigations of validation methods on gas phase species and particulate matter on the one hand side, and for the development of fully digitized quality assurance/quality control and calibration techniques for sensor networks on the other (CEN/CENELEC, Opportunity for Standardisation to Contribute to the European Partnership on Metrology EPM under Horizon Europe). This contribution concentrates on the metrological traceability of sensor networks for air quality monitoring to the international system of units (SI) based on FAIRified intra-network communications (M. Wilkinson, et al., “The FAIR guiding principles for scientific data management and stewardship,” Sci. Data, vol. 3, 2016, Art. no. 160018) and including delocalized Optical Gas Standards operated according to the digital TILSAM method (O. Werhahn, et al., The TILSAM Method Adapted into Optical Gas Standards – Complementing Gaseous Reference Materials, PTB Open Access Repository, 2021). Informed by related activities in EURAMET (Partnership project FunSNM, EMNs COO & POLMO, TC-IM 1551) (European Metrology Network Climate and Ocean Observation (COO), European Metrology Network Pollution Monitoring (POLMO), EURAMET Project TC-IM 1551, Project Database) this contribution discusses the importance of measurement uncertainties in the context of sensor networks, comprising different sensor principles and promoting an efficient uptake of state-of-the-art methods. We discuss how the sensor network case can be addressed with sensors individually using the GUM principles (Joint Committee for Guides in Metrology, Guide to the Expression of Uncertainty in Measurement (GUM), JCGM 100: 2008 (E)). For sensor network measurements becoming metrologically traceable to the SI, documented and unbroken chains of calibrations need to be implemented each contributing to the measurement uncertainty. This applies to each individual sensor of the network including the potential gold standard among them, but also to the network’s output viewed as a single entity. The contribution provides first approaches to be tested and validated that are underpinned by fundamental design strategies for sensor networks. It follows on practical applications in real world scenarios aside from model uncertainties discussed in artificial intelligence prospects.

Calibrating the global network of gravitational wave observatories via laser power calibration at NIST and PTB

Current gravitational wave (GW) observatories rely on photon calibrators that use laser radiation pressure to generate displacement fiducials used to calibrate detector output signals. Reducing calibration uncertainty enables optimal extraction of astrophysical information such as source distance and sky position from detected signals. For the ongoing O4 observing run that started on 24 May 2023, the global GW detector network is employing a new calibration scheme with transfer standards calibrated at both the National Institute of Standards and Technology (NIST) and the Physikalisch-Technische Bundesanstalt (PTB). These transfer standards will circulate between the observatories and the metrology institutes to provide laser power calibration traceable to the International System of Units (SI) and enable assessment and reduction of relative calibration errors for the observatory network. The Laser Interferometer Gravitational-Wave Observatory (LIGO) project and the Virgo project are currently participating in the new calibration scheme. The Large-scale Cryogenic Gravitational-wave Telescope project (KAGRA) is expected to join in 2024, with the LIGO Aundha Observatory in India joining later. Before implementing this new scheme, a NIST-PTB bilateral comparison was conducted. It validated the scale representation by both laboratories, with a degree of equivalence of −0.2% and an associated expanded uncertainty of 0.32% (k = 2) which is significantly lower than previous studies. We describe the transfer of power sensor calibration, including detailed uncertainty estimates, from the transfer standards calibrated by NIST and PTB to the sensors operating continuously at the interferometer end stations. Finally, we discuss the ongoing calibration of Pcal-induced displacement fiducials for the O4 observing run. Achieved combined standard uncertainty levels as low as 0.3% facilitate calibrating the interferometer output signals with sub-percent accuracy.

Step height measurement of monoatomic silicon crystal lattice steps with a commercial atomic force microscope

Abstract Precise control of advanced materials relies on accurate dimensional metrology at the sub-nanometre scale. At this scale, the accuracy of scanning probe microscopy (SPM) has been limited by the lack of traceable transfer standard artefacts with calibration structures of suitable dimensions. With the adoption in 2019 of the silicon crystal lattice spacing as a secondary realization of the metre in the International System of Units (SI), SPM users have direct access to a realization of the SI metre at the sub-nanometre level by means of the step height of self-assembled monatomic lattice steps that can form on the surface of silicon crystals. A key challenge of successfully adopting this pathway is establishing the need for established protocols to minimize measurement errors and artifacts in routine laboratory use.
In this study, step height measurements of monoatomic lattice steps in an ordinal/staircase structure on a Si(111) crystal surface have been derived from images acquired with a commercially available, research-level atomic force microscope (AFM). Measurement results derived from AFM images using three different SPM image processing and analysis software packages are compared. Significant sources of measurement uncertainty are identified; principally the contribution from the dependence on scan direction. The calibration of the
AFM derived from this measurment was used to traceably measure the sub-nanometre lattice steps on a silicon carbide crystal surface to demonstrate the viability of this calibration pathway.

The investigation of traceable preparation technique of submicron particle number concentration standards in liquids

The concentration of particles at the nano- and submicron-meter scale in liquid is crucial in multiple fields including the biomedical and semiconductor industry. However, there is still a lack of metrological standards or Certified Reference Materials (CRMs) for liquid-borne particle number concentration (PNC) which could be traceable to the International System of Units (SI). To address this issue, a quantitative and value-traceable preparation technique for liquid-borne particle number concentration CRMs (PNC-CRMs) in a submicron-meter scale based on controllable aerosol generation and collection was developed in this study. In this technique, by using commercial differential electrostatic mobility analyzer (DMA) and calibrated condensation particle counter (CPC), monodisperse aerosol particle with known concentration was initially generated. Then for quantitatively transforming the aerosol particles to the liquid, an aerosol particle collection system was designed and developed by hydrodynamic (CFD) simulations and experiment conducting, and crucial parameters of the collection system, e.g. the nozzle diameter of the aerosol particle outlet, the distance from the nozzle to the liquid surface, and the state of the liquid interface, were investigated and optimized. Under the optimized collected parameters, the collection efficiency for aerosol particles of the newly-developed system could reach over 90%. Because the PNC in aerosol is SI-traceable, combined with the obtained collection efficiency and collection time, the PNC in the collection liquid with could be obtained finally and trace to SI unit. Using this technique, two kinds of PNC-CRMs with nominal sizes of 100 and 500 nm were developed successfully, where, certified values were (7–9) × 106 particles/mL and 1.7 × 106 particles/mL, and standard uncertainties are 4.2%.

Traceable Calibration of Atmospheric Oxidized Mercury Measurements.

Most previous measurements of oxidized mercury were collected using a method now known to be biased low. In this study, a dual-channel system with an oxidized mercury detection limit of 6-12 pg m-3 was deployed alongside a permeation tube-based automated calibrator at a mountain top site in Steamboat Springs Colorado, USA, in 2021 and 2022. Permeation tubes containing elemental mercury and mercury halides were characterized via an International System of Units (SI)-traceable gravimetric method and gas chromatography/mass spectrometry before deployment in the calibrator. The dual-channel system recovered 97 ± 4 and 100 ± 8% (±standard deviation) of injected elemental mercury and HgBr2, respectively. Total Hg permeation rates and Hg speciation from the gravimetric method, the chromatography system, the dual-channel system, and an independent SI-traceable measurement method performed at the Jožef Stefan Institute laboratory were all comparable within the respective uncertainties of each method. These are the first measurements of oxidized mercury at low environmental concentrations that have been verified against an SI-traceable calibration system in field conditions while sampling ambient air, and they show that accurate, routinely calibrated oxidized mercury measurements are achievable.

Avogadro and Planck Constants, Two Pillars of the International System of Units

The International System of Units (SI), the current form of the metric system and the world’s most used system of units, has been continuously updated and refined since the Metre Convention of 1875 to ensure that it remains up to date with the latest scientific and technological advances. The General Conference on Weights and Measures, at its 26th meeting in 2018, decided to adopt stipulated values of seven physical constants linked to seven measurement units (the second, meter, kilogram, ampere, kelvin, mole, and candela). This paper reviews the technologies developed, in intense and long-standing work, to determine the Avogadro and Planck constants, which are now integral to realising the kilogram.

CIPM MRA support for hydrogen metrology – A case study

The CIPM Mutual Recognition Arrangement (CIPMMRA) provides one of the most profound frameworks for internationally recognized metrological traceability to the international system of units (SI). National Metrology Institutes demonstrate the international equivalence of their measurement standards and the calibration and measurement certificates they issue through the CIPMMRA. CIPMMRA activities comprise the organization and evaluation of key and supplementary comparisons (KCs/SCs) and the declaration of calibration and measurement capabilities (CMCs) in the BIPM key comparison database (KCDB). In this contribution we showcase up-to-date CIPMMRA activities that could be used in support of hydrogen as a future option for the diversification of energy sources. Relevant metrology areas are chemistry and biology, thermometry, mass, and length. There are already 3 KCs in progress within the CIPMMRA that are directly related to the hydrogen topic and a number of earlier KCs/SCs on other relavant quantities. Todate, the KCDB contains CMCs published by National Metrology Institutes which are dealing exactly with hydrogen as the analyte or which relate to measurement capabilities that are relevant in the context of hydrogen as future energy source.

Results from 2023 interlaboratory comparison in Southeast and East Asia on OSL personal dosimeter performance in photon fields

The intercomparison of personal dose equivalent (Hp(10)) among nine economies was carried out at 27 Individual Monitoring Service (IMS) Laboratories in Southeast and East Asia in 2023. In this programme, a whole-body dose assessment from Cs-137 and N-80 X-rays with two different incident beam angles (0 deg and 30 deg) was performed using an Optically Stimulated Luminescence (OSL) dosimeter. The trumpet curve recommended by IAEA GSG-7 was used as the criterion of acceptance value. The results showed that 95% of all data were within the acceptable value, with 13 items of data from two laboratories being unacceptable. After the intercomparison programme was concluded, these two laboratories implemented system improvement, including reader performance checks, calibration, configuration adjustment, and dose evaluation method enhancement. The results after improvement fell within the acceptable limit, indicating successful system enhancement. This study contributes to the harmonisation of individual monitoring service laboratories in Southeast and East Asia, ensuring that measurement results are traceable to the International System of Units (SI). Each laboratory fulfils the performance standard requirements to ensure the validity of the results for the individual monitoring service laboratory. Moreover, the complementary study induced by this exercise indicates the necessity of the intercomparison programme and successful outcome of the system improvement.

Linking Seismic Measurements to the International System of Units

AbstractThe current state of the art in the calibration of seismometers is given by internal calibration procedures which give only incomplete information about a seismometer’s response and are based on transfer functions supplied by manufacturers. Calibrations traceable to the International System of Units (SI) provide an independent and comprehensible characterization of seismometers. These calibrations take part in a laboratory using an electrodynamic shaker or shake table. To overcome the issue that seismometers placed in seismic stations are not supposed to be moved to a calibration laboratory, novel on-site calibration methods incorporating a reference seismometer were developed. Such a reference is placed near the sensor to be calibrated, and the transfer function of the seismometer under test can be derived based on the output of both sensors.

Linearizing the vertical scale of an interferometric microscope and its effect on step-height measurement.

The vertical scale calibration of an interferometric microscope is important for establishing traceability of surface topography measurements to the International System of Units (SI) unit of length, the meter. Building on the calibration procedure for the amplification coefficient developed by de Groot and Beverage [Proc. SPIE 9526, 952610 (2015)], this paper describes a calibration procedure that yields the response curve for the entire vertical scan motion of a coherent scanning interferometric microscope. The method requires only a flat mirror as an artifact, a narrow band spectral filter, an aperture to reduce the effective numerical aperture, and the ability to raise and lower the microscope head so that the center of the interferogram can be varied within the scan range. The local frequency of the interferogram is determined by fitting sections of the interferogram to a sinusoidal function. The nonlinearity determined from the local frequency data can be used to estimate the uncertainty in uncorrected vertical height measurements. We describe how optical profile data can be corrected for nonlinearity due to dynamic effects in the scan motion and show that the correction improves the reproducibility of step height measurements by at least a factor of three and close to that of the repeatability.

Purity Assessment of Tripropyl Phosphate through Mass Balance and 1H and 31P Quantitative Nuclear Magnetic Resonance.

Tripropyl phosphate (TnPP) is a commonly used organic phosphate flame retardant in the textiles, plastics, and coating industries. Residues are commonly detected in samples from the environment and food. The availability of certified reference materials (CRMs) is essential to ensure the accuracy and traceability of detection results. In this study, a comprehensive characterization of a CRM for TnPP was carried out, and its purity was evaluated using two distinct methodologies: mass balance (MB) and quantitative nuclear magnetic resonance spectroscopy (qNMR). In the MB method, the levels of structurally related organic impurities are 1.37 mg/g. The water content was determined to be 3.16 mg/g, while inorganic impurities were found to be 0.87 mg/g, and no residual organic solvents were detected. Benzoic acid and monocrotophos were chosen as internal standards for 1H-qNMR and 31P-qNMR, respectively. The purity of the TnPP CRM was assessed as 994.6 mg/g, 994.1 mg/g, and 993.5 mg/g using MB, 1H-qNMR, and 31P-qNMR techniques, respectively. The verified purity of the TnPP CRM was ultimately determined to be 994.1 mg/g, with an expanded uncertainty of 3.4 mg/g (k = 2), ensuring traceability to the International System of Units (SI). This CRM can be effectively utilized for preparing calibration solutions suitable for the routine monitoring of TnPP residues in plastics and food samples.

Development of 3β,4α-dihydroxy-5α-androstan-17-one standard solution for doping analyses.

Doping analyses are essential for sporting events because some athletes might use prohibited substances to win games. To obtain reliable results from doping analyses, it is important to use both reliable standard solutions and validated analytical methods at accredited laboratories. Among the focused compounds related to prohibited substances listed by the World Anti-Doping Agency, we developed a certified reference material (CRM) for 3β,4α-dihydroxy-5α-androstan-17-one (DHAS), a metabolite of formestane that is used to conceal prohibited anabolic steroids, in methanol solution (NMIJ CRM 6212-a). To develop a CRM traceable to the International System of Units (SI), we newly applied different analytical methods with an SI-traceable internal standard for quantitative NMR (qNMR) instead of mass balance approach because this CRM solution was required to develop rapidly using a limited amount of high-purity DHAS. One method was gravimetric blending using the purity of DHAS powder evaluated by both qNMR and a combination of qNMR and high-performance liquid chromatography (HPLC), and the other was direct quantification of the DHAS mass fraction in the candidate solution CRM by both qNMR and qNMR/HPLC. Because the values obtained by gravimetric blending and direct quantification of the mass fraction were comparable, the arithmetic mean was applied to obtain the certified value. Considering homogeneity and stability according to ISO Guide 35: 2017, the certified values with expanded uncertainties (coverage factor k = 2, approximate 95% confidence interval) were (135.2 ± 9.5) μg/g for the mass fraction and (107.0 ± 7.5) μg/ml for the mass concentration.

Two new 222Rn emanation sources – a comparison study

Abstract. More than 50 % of naturally occurring radiation exposure to the general public is due to the noble gas radon (222Rn) and its progenies, causing considerable health risks. Therefore, the European Union has implemented Council Directive 2013/59/EURATOM to measure 222Rn activity concentrations and to identify radon priority areas (RPAs) to specify areas where countermeasures are most needed. Although 222Rn measurements are far spread across Europe, traceability to the International System of Units (SI) is still lacking for radon activity concentrations below 300 Bq m−3. Consequently, measurement results cannot be reliably compared with each other. The European Metrology Research Programme for Innovation and Research (EMPIR) 19ENV01 traceRadon project aimed to address this issue and has developed two new 222Rn emanation sources, intended to be used as calibration standards for reference instruments. The goal of this paper is to investigate and compare the two sources to ensure their quality by comparing the calibration factors estimated from both sources for the same reference instrument. This was done for three reference instruments in total at two experimental sites. Differences in calibration factors for one reference instrument of up to 0.07 were derived. Despite the small differences between the calibration factors, all uncertainties are well within the intended target uncertainty of 10 % for k = 1.