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

ACTA IMEKO ◽  
2017 ◽  
Vol 6 (2) ◽  
pp. 4 ◽  
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

<p><span lang="EN-US">A small force of (10</span><span lang="EN-US">–</span><span lang="EN-US">100) micro-Newton traceable to the International System of Units (SI) has been realized using</span><span lang="EN-US"> an</span><span lang="EN-US"> electrostatic </span><span lang="EN-US">measuring system</span><span lang="EN-US"> 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 </span><span lang="EN-US">used</span><span lang="EN-US"> 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 %.</span></p>

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

2017 ◽  
Vol 122 ◽  
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.

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

2021 ◽  
Vol 11 (12) ◽  
pp. 5361
Author(s):  
Javis A. Nwaboh ◽  
Zhechao Qu ◽  
Olav Werhahn ◽  
Volker Ebert
Keyword(s):  
International System ◽  
Line Strength ◽  
Reference Method ◽  
Standard Uncertainty ◽  
Tunable Diode Laser ◽  
Relative Standard ◽  
System Of Units ◽  
Gas Standard ◽  
Calibration Free ◽  
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.

A NEW SCHEME TO REALIZE THE MEASUREMENT STANDARD OF MICROFORCE

2005 ◽  
Vol 04 (04) ◽  
pp. 689-694
Author(s):  
HSIEN-CHI YEH ◽  
SWEE HOCK YEO ◽  
SHEAU-SHI PAN ◽  
JUN LUO
Keyword(s):  
Gravitational Force ◽  
Gravitational Constant ◽  
Force Measurement ◽  
International System ◽  
Torsion Balance ◽  
Measuring Instruments ◽  
Measurement Standard ◽  
System Of Units ◽  
Small Force ◽  
Newtonian Gravitational Constant

To increase the accuracy of mechanical characterizations of microstructures and nanomaterials on the molecular- and nano-scale, the measurement standard of microforce ranging from 10-6 N to 10-9 N must be realized for calibrating the testing and measuring instruments. In this paper, a new scheme based on the equal-arm torsion balance is proposed. This precision torsion balance detects accurately the gravitational force between two mass standards, and links the small force measurement to the International System of Units and Newtonian gravitational constant G. Such a balance might serve as a force standard machine operating in the regime below 10-6 N with an accuracy of 0.1%.

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

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.

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

2019 ◽  
Vol 8 (1) ◽  
pp. 195-205 ◽  
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.

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

2016 ◽  
Vol 374 (2064) ◽  
pp. 20150050 ◽  
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%.

scholarly journals The Tortuous Road to the Adoption of katal for the Expression of Catalytic Activity by the General Conference on Weights and Measures

2002 ◽  
Vol 48 (3) ◽  
pp. 586-590 ◽  
Author(s):  
René Dybkær
Keyword(s):  
Catalytic Activity ◽  
International System ◽  
Measurement Procedure ◽  
Enzymic Activity ◽  
Measuring System ◽  
Medical Laboratory ◽  
International Union ◽  
Weights And Measures ◽  
System Of Units ◽  
Global Standardization

Abstract Background: The “unit” for “enzymic activity” (U = 1 μmol/min) was recommended by the International Union of Biochemistry and Molecular Biology (IUB) in 1961 and is widely used in medical laboratory reports. The general trend in metrology, however, is toward global standardization through defining units coherent with the International System of Units (SI). Approach: Several proposals were advanced from the IFCC, International Union of Pure and Applied Chemistry, and IUB regarding the definition for enzymic activity as well as the terms for kind-of-quantity, units, symbol, and dimension. In 1977, international agreement was reached between these bodies and WHO that “catalytic activity” (z), of a catalyst in a given system is defined by the rate of conversion in a measuring system (in mol/s) and expressed in “katal” (symbol, kat; equal to 1 mol/s). The katal is invariant of the measurement procedure, but the numerical quantity value is not. Gaining support for the katal from the final arbiter, the General Conference on Weights and Measures, was slow, but Resolution 12 of 1999 adopted the katal (symbol, kat) as a special name and symbol for the SI-derived unit, mol/s, used in measuring catalytic activity. Conclusions: Laboratory results for amounts of catalysts, including enzymes, measured by their catalytic activity can now officially be expressed in katals and are traceable to the SI provided that the specified indicator reaction reflects first-order kinetics. The conversion from “unit” is: 1 U = 16.667 × 10−9 kat. Further derived quantities have coherent units such as kat/L, kat/kg, and kat/kat = 1.

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

Minerals ◽  
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.

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