Towards an Optical Gas Standard for Traceable Calibration-Free and Direct NO2 Concentration Measurements

We report a direct tunable diode laser absorption spectroscopy (dTDLAS) instrument developed for NO2 concentration measurements without chemical pre-conversion, operated as an Optical Gas Standard (OGS). An OGS is a dTDLAS instrument that can deliver gas species amount fractions (concentrations), without any previous or routine calibration, which are directly traceable to the international system of units (SI). Here, we report NO2 amount fraction quantification in the range of 100–1000 µmol/mol to demonstrate the current capability of the instrument as an OGS for car exhaust gas application. Nitrogen dioxide amount fraction results delivered by the instrument are in good agreement with certified values of reference gas mixtures, validating the capability of the dTDLAS-OGS for calibration-free NO2 measurements. As opposed to the standard reference method (SRM) based on chemiluminescence detection (CLD) where NO2 is indirectly measured after conversion to NO, titration with O3 and the detection of the resulting fluorescence, a dTDLAS-OGS instrument has the benefit of directly measuring NO2 without distorting or delaying conversion processes. Therefore, it complements the SRM and can perform fast and traceable measurements, and side-by-side calibrations of other NO2 gas analyzers operating in the field. The relative standard uncertainty of the NO2 results reported in this paper is 5.1% (k = 1, which is dominated (98%) by the NO2 line strength), the repeatability of the results at 982.6 µmol/mol is 0.1%, the response time of the instrument is 0.5 s, and the detection limit is 825 nmol/mol at a time resolution of 86 s.

Download Full-text

The NIST Johnson Noise Thermometry System for the Determination of the Boltzmann Constant

Journal of Research of the National Institute of Standards and Technology ◽

10.6028/jres.122.046 ◽

2017 ◽

Vol 122 ◽

Cited By ~ 5

Author(s):

Nathan E. Flowers-Jacobs ◽

Alessio Pollarolo ◽

Kevin J. Coakley ◽

Adam C. Weis ◽

Anna E. Fox ◽

...

Keyword(s):

International System ◽

Standard Uncertainty ◽

Boltzmann Constant ◽

Correlated Noise ◽

Johnson Noise ◽

Noise Thermometry ◽

Relative Standard ◽

System Of Units ◽

Johnson Noise Thermometry

In preparation for the redefinition of the International System of Units (SI), five different electronic measurements of the Boltzmann constant have been performed using different Johnson noise thermometry (JNT) systems over the past seven years. In this paper, we describe in detail the JNT system and uncertainty components associated with the most recent National Institute of Standards and Technology (NIST) determination of the Boltzmann constant: k = 1.380642 9(69) × 10−23 J/K, with a relative standard uncertainty of 5.0 × 10−6 and relative offset of −4.05 × 10−6 from the Committee on Data for Science and Technology (CODATA) 2014 recommended value. We discuss the input circuits and the approach we used to match the frequency response of two noise sources. We present new measurements of the correlated noise of the 4 K on-chip resistors in the quantum-accurate, pseudorandom, voltage-noise source, which we used to estimate the correlated, frequency-dependent, nonthermal noise in our system. Finally, we contrast our system with those used in other measurements and speculate on future improvements.

Download Full-text

Realization of an SI traceable small force of 10 to 100 micro-Newton using an electrostatic measuring system

ACTA IMEKO ◽

10.21014/acta_imeko.v6i2.336 ◽

2017 ◽

Vol 6 (2) ◽

pp. 4 ◽

Cited By ~ 1

Author(s):

Jile Jiang ◽

Gang Hu ◽

Zhimin Zhang

Keyword(s):

Laser Interferometer ◽

International System ◽

Feedback System ◽

Standard Uncertainty ◽

Measuring System ◽

Flexure Hinge ◽

Relative Standard ◽

System Of Units ◽

Capacitance Bridge ◽

Small Force

A small force of (10–100) micro-Newton traceable to the International System of Units (SI) has been realized using an electrostatic measuring system at the National Institute of Metrology, China. The key component of the measuring system is a pair of coaxial cylindrical electrodes. The inner electrode is suspended with the support of a self-balanced flexure hinge, while the outer electrode is attached to a piezoelectric moving stage. The stiffness of the self-balanced flexure hinge was also designed so as to be both sufficiently stable and sensitive to the small force applied to the inner electrode. Two sets of cameras were used to capture the shape of the electrodes and to obtain a better coaxial arrangement of the inner and outer electrodes. With the help of a capacitance bridge and a piezoelectric moving stage, the relative standard uncertainty of the capacitance gradient does not exceed 0.04 %. Associated with a laser interferometer and a DC voltage power source, the feedback system that controls the position of the inner electrode is responsible for the generation of a force of 10–100 micro-Newton. The standard uncertainty associated with the force of 100 micro-Newton does not exceed 0.1 %.

Download Full-text

TOWARD THE REDEFINITION OF THE KILOGRAM FROM THE 28Si INTERNATIONAL RESEARCH PROJECT

International Journal of Modern Physics Conference Series ◽

10.1142/s201019451360001x ◽

2013 ◽

Vol 24 ◽

pp. 1360001

Author(s):

KENICHI FUJII

Keyword(s):

International Research ◽

International System ◽

Physical Constant ◽

Standard Uncertainty ◽

Research Project ◽

Avogadro Constant ◽

Counting Procedure ◽

System Of Units ◽

Fundamental Physical ◽

International Research Project

In the international system of units, the kilogram in the only SI base unit still defined by a material artefact. In order to redefine this unit with a fundamental physical constant, an international research project was launched in 2004 for determining the Avogadro constant, NA, by counting the atoms in an isotopically enriched 28Si crystal. The counting procedure relies on the measurements of the molar and atomic volumes of 1 kg spheres made of the 28Si crystal. In 2011, the project succeeded in measuring the Avogadro constant with a smallest standard uncertainty, 3.0 × 10−8 NA. Because of an unexpected metallic contamination at the surface of the spheres, the measurement uncertainty was larger than the target of the project by a factor of 1.5. In order to further reduce the uncertainty, a new international research project was launched in 2012. Outline of the new project and the improvements of the measurements will be introduced at the forum. Note from Publisher: This article contains the abstract only.

Download Full-text

Measurement of the absolute spectral responsivity in the mid-infrared based on the cryogenic electrical substitution radiometer and an optimized thermopile detector

Journal of Sensors and Sensor Systems ◽

10.5194/jsss-8-195-2019 ◽

2019 ◽

Vol 8 (1) ◽

pp. 195-205 ◽

Cited By ~ 1

Author(s):

Tobias Pohl ◽

Peter Meindl ◽

Uwe Johannsen ◽

Dieter Taubert ◽

Lutz Werner

Keyword(s):

International System ◽

Absolute Measurement ◽

Spectral Responsivity ◽

Mid Infrared ◽

Housing Design ◽

Radiation Sources ◽

Relative Standard ◽

System Of Units ◽

The Absolute ◽

Radiant Power

Abstract. The Physikalisch-Technische Bundesanstalt (PTB) expanded its capabilities of the absolute measurement of radiant power to the spectral range of the mid-infrared (MIR) by implementing additional MIR laser radiation sources at one of the PTB's cryogenic electrical substitution radiometer facilities. This extension enables absolute calibrations of the spectral responsivity of detectors in the MIR traceable to the International System of Units (SI). The thermopile detector TS-76 was characterized and calibrated in view of its spectral responsivity s(λ) in the wavelength range between 1.5 and 10.6 µm at the expanded cryogenic electrical substitution radiometer facility. The relative standard measurement uncertainty was significantly reduced to 1.4 % by developing an optimized and thermally stabilized detector housing design. The TS-76 was established as a mid-infrared transfer detector for the SI traceable measurement of radiant power and the dissemination of the spectral responsivity s(λ) in the MIR.

Download Full-text

A SQUID-based primary noise thermometer for low-temperature metrology

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2015.0050 ◽

2016 ◽

Vol 374 (2064) ◽

pp. 20150050 ◽

Cited By ~ 9

Author(s):

A. Kirste ◽

J. Engert

Keyword(s):

Low Temperature ◽

Quantum Interference ◽

International System ◽

Thermodynamic Temperature ◽

Uncertainty Budget ◽

Standard Uncertainty ◽

Primary Thermometry ◽

Magnetic Field Fluctuation ◽

Noise Thermometer ◽

System Of Units

Practical temperature measurements in accordance with the international system of units require traceability to the international temperature scales currently in force. Along with the awaited redefinition of the unit of temperature, the kelvin, on the basis of the Boltzmann constant, in future its mise en pratique will allow the use of approved methods of primary thermometry for the realization and dissemination of the kelvin. To support this process, we have developed a DC superconducting quantum interference device-based noise thermometer especially designed for measurements of thermodynamic temperature in a broad temperature range from 5 K down to below 1 mK. In this paper, we describe in detail the primary magnetic field fluctuation thermometer and the underlying model applied for the temperature determination. Experimental measurement results are presented for a comparison with the Provisional Low Temperature Scale 2000 between 0.7 K and 16 mK including an uncertainty budget for the measured thermodynamic temperatures. In this set-up, the relative combined standard uncertainty is equal to 0.6%.

Download Full-text

Comparability of calibration strategies for measuring mercury concentrations in gas emission sources and the atmosphere

Atmospheric Measurement Techniques ◽

10.5194/amt-14-2317-2021 ◽

2021 ◽

Vol 14 (3) ◽

pp. 2317-2326

Author(s):

Iris de Krom ◽

Wijnand Bavius ◽

Ruben Ziel ◽

Elizabeth A. McGhee ◽

Richard J. C. Brown ◽

...

Keyword(s):

Reference Material ◽

Mercury Concentration ◽

International System ◽

Elemental Mercury ◽

Ambient Air ◽

The United States ◽

National Metrology Institute ◽

Calibration Methods ◽

System Of Units ◽

Gas Standard

Abstract. A primary mercury gas standard was developed at Van Swinden Laboratory (VSL) to establish an International System of Units (SI)-traceable reference point for mercury concentrations at emission and background levels in the atmosphere. The majority of mercury concentration measurements are currently made traceable to the empirically determined vapour pressure of mercury. The primary mercury gas standard can be used for the accurate and precise calibration of analytical systems used for measuring mercury concentrations in air. It has been especially developed to support measurements related to ambient air monitoring (1–2 ng m−3), indoor and workplace-related mercury concentration levels according to health standards (from 50 ng m−3 upwards) as well as stationary source emissions (from 1 µg m−3 upwards). The primary mercury gas standard is based on diffusion according to ISO 6154-8. Calibration gas mixtures are obtained by combining calibrated mass flows of nitrogen and air through a generator holding diffusion cells containing elemental mercury. In this paper, we present the results of comparisons between the primary gas standard and mercury calibration methods maintained by NPL (National Physical Laboratory in the United Kingdom), a National Metrology Institute (NMI), and the Jozef Stefan Institute (JSI), a Designated Institute (DI). The calibration methods currently used at NPL and JSI are based on the bell-jar calibration apparatus in combination with the Dumarey equation or a NIST (National Institute of Standards and Technology in the United States) reference material. For the comparisons, mercury was sampled on sorbent traps to obtain transfer standards with levels between 2 and 1000 ng with an expanded uncertainty not exceeding 3 % (k=2). The comparisons performed show that the results for the primary gas standard and the NIST reference material are comparable, whereas a difference of −8 % exists between results traceable to the primary gas standard and the Dumarey equation.

Download Full-text

A candidate liquid chromatography mass spectrometry reference method for the quantification of the cardiac marker 1-32 B-type natriuretic peptide

Clinical Chemistry and Laboratory Medicine (CCLM) ◽

10.1515/cclm-2016-1054 ◽

2017 ◽

Vol 55 (9) ◽

Cited By ~ 5

Author(s):

Attila F. Torma ◽

Kate Groves ◽

Sabine Biesenbruch ◽

Chris Mussell ◽

Alan Reid ◽

...

Keyword(s):

Mass Spectrometry ◽

Liquid Chromatography ◽

Amino Acid ◽

Natriuretic Peptide ◽

International System ◽

Reference Method ◽

Liquid Chromatography Mass Spectrometry ◽

Chromatography Mass Spectrometry ◽

System Of Units ◽

The Uk

AbstractBackground:B-type natriuretic peptide (BNP) is a 32 amino acid cardiac hormone routinely measured by immunoassays to diagnose heart failure. While it is reported that immunoassay results can vary up to 45%, no attempt of standardization and/or harmonization through the development of certified reference materials (CRMs) or reference measurement procedures (RMPs) has yet been carried out.Methods:B-type natriuretic peptide primary calibrator was quantified traceably to the International System of Units (SI) by both amino acid analysis and tryptic digestion. A method for the stabilization of BNP in plasma followed by protein precipitation, solid phase extraction (SPE) and liquid chromatography (LC) mass spectrometry (MS) was then developed and validated for the quantification of BNP at clinically relevant concentrations (15–150 fmol/g).Results:The candidate reference method was applied to the quantification of BNP in a number of samples from the UK NEQAS Cardiac Markers Scheme to demonstrate its applicability to generate reference values and to preliminary evaluate the commutability of a potential CRM. The results from the reference method were consistently lower than the immunoassay results and discrepancy between the immunoassays was observed confirming previous data.Conclusions:The application of the liquid chromatography-mass spectrometry (LC-MS) method to the UK NEQAS samples and the correlation of the results with the immunoassay results shows the potential of the method to support external quality assessment schemes, to improve understanding of the bias of the assays and to establish RMPs for BNP measurements. Furthermore, the method has the potential to be multiplexed for monitoring circulating truncated forms of BNP.

Download Full-text

Development of in-House Industrial Fluosilicic Acid Certified Reference Material: Certification of H2SiF6 Mass Fraction

Minerals ◽

10.3390/min11010092 ◽

2021 ◽

Vol 11 (1) ◽

pp. 92

Author(s):

Said Kounbach ◽

Mokhtar Ben Embarek ◽

Abdeljalil Chemaa ◽

Rachid Boulif ◽

Rachid Benhida ◽

...

Keyword(s):

Reference Material ◽

Certified Reference Material ◽

Analytical Methods ◽

Mass Fraction ◽

International System ◽

Measurement Data ◽

Metrological Traceability ◽

Standard Uncertainty ◽

System Of Units ◽

Fluosilicic Acid

Fluosilicic acid is a by-product of the chemical phosphate industry, mainly during the manufacture of phosphoric acid and triple super phosphate (TSP). To ensure the accurate measurement of the H2SiF6 mass fraction in this by-product, method validation is required, which needs a certified reference material (CRM) with its traceability to the International System of Units (SI). This work describes the development of a certified reference material of fluosilicic acid, which is commercially unavailable. Details of all steps, such as sample preparation, homogeneity and stability studies, value assignment, establishment of metrological traceability, and uncertainty estimation of the certified reference material, are fully described. The H2SiF6 mass fraction in the CRM was quantified by two analytical methods, i.e., UV-VIS as a primary method of analysis and flame mode atomic absorption spectroscopy (AAS) as a second method. It is worth noting that the results obtained from each method were in good agreement. The CRM certified value and corresponding expanded uncertainty, obtained from the combined standard uncertainty multiplied by the coverage factor (k = 2), for a confidence interval of 95%, was (91.5 ± 11.7) g·kg−1. The shelf life of the developed CRM is determined to be 1 year, provided that storage conditions are ensured. The developed CRM can be applied to validate analytical methods, improve the accuracy of measurement data as well as to establish the meteorological traceability of analytical results.

Download Full-text

THE INTERNATIONAL SYSTEM OF UNITS

The Mechanical Universe ◽

10.1017/cbo9780511818509.032 ◽

1985 ◽

pp. 563-564

Keyword(s):

International System ◽

International System Of Units ◽

System Of Units

Download Full-text

Dimensions of plane and solid angles and their units in the International System of Units (SI)

Izmeritel`naya Tekhnika ◽

10.32446/0368-1025it.2020-10-26-32 ◽

2020 ◽

pp. 26-32

Author(s):

M. I. Kalinin ◽

L. K. Isaev ◽

F. V. Bulygin

Keyword(s):

Solid Angle ◽

International System ◽

International Committee ◽

Plane Angle ◽

Arc Length ◽

Weights And Measures ◽

International System Of Units ◽

System Of Units ◽

In Series ◽

Solid Angles

The situation that has developed in the International System of Units (SI) as a result of adopting the recommendation of the International Committee of Weights and Measures (CIPM) in 1980, which proposed to consider plane and solid angles as dimensionless derived quantities, is analyzed. It is shown that the basis for such a solution was a misunderstanding of the mathematical formula relating the arc length of a circle with its radius and corresponding central angle, as well as of the expansions of trigonometric functions in series. From the analysis presented in the article, it follows that a plane angle does not depend on any of the SI quantities and should be assigned to the base quantities, and its unit, the radian, should be added to the base SI units. A solid angle, in this case, turns out to be a derived quantity of a plane angle. Its unit, the steradian, is a coherent derived unit equal to the square radian.

Download Full-text