European National Metrology Institutes Research Articles

Rola i znaczenie cyfrowych mostków impedancji we współczesnej metrologii

The article presents current trends in impedance metrology of the highest accuracy. Attention was paid to digital non-quantum impedance bridges, which have been developed in many European National Metrology Institutes over the last decade. Particular attention in the article was devoted to the digital impedance bridge currently being developed at the Central Office of Measures in Warsaw. The conceptual diagram, system implementation and the progress of work related to the development of this bridge and its implementation in the near future into the national measurement system are presented as well.

Demonstration of a Transportable Fabry-Pérot Refractometer by a Ring-Type Comparison of Dead-Weight Pressure Balances at Four European National Metrology Institutes.

Fabry-Pérot-based refractometry has demonstrated the ability to assess gas pressure with high accuracy and has been prophesized to be able to realize the SI unit for pressure, the pascal, based on quantum calculations of the molar polarizabilities of gases. So far, the technology has mostly been limited to well-controlled laboratories. However, recently, an easy-to-use transportable refractometer has been constructed. Although its performance has previously been assessed under well-controlled laboratory conditions, to assess its ability to serve as an actually transportable system, a ring-type comparison addressing various well-characterized pressure balances in the 10-90 kPa range at several European national metrology institutes is presented in this work. It was found that the transportable refractometer is capable of being transported and swiftly set up to be operational with retained performance in a variety of environments. The system could also verify that the pressure balances used within the ring-type comparison agree with each other. These results constitute an important step toward broadening the application areas of FP-based refractometry technology and bringing it within reach of various types of stakeholders, not least within industry.

Case studies for the MATHMET Quality Management System at VSL, the Dutch National Metrology Institute

The European Metrology Network MATHMET is a network in which a large number of European national metrology institutes combine their forces in the area of mathematics and statistics applied to metrological problems. One underlying principle of such a cooperation is to have a common understanding of the ‘quality’ of software, data and guidelines. To this purpose a flexible, lightweight Quality Management System (QMS), also referred to as Quality Assessment Tools (QAT), is under development by the EMN. In this contribution the application of the QMS to several use cases of different nature by VSL is presented. The benefits and usefulness of the current version of the QMS are discussed from the particular viewpoint of a particular employee of VSL, and an outlook for possible future extensions and usage of the QMS is given.

ALTECH 2021 – Analytical Techniques for Precise Characterization of Nano Materials

ALTECH 2021 – Analytical Techniques for Precise Characterization of Nano Materials

Vision for a European metrology network for energy gases

Abstract As Europe moves towards decarbonising its energy infrastructure, new measurement needs will arise that require collaborative efforts between European National Metrology Institutes and Designated Institutes to tackle. Such measurement needs include flow metering of hydrogen or hydrogen enriched natural gas in the gas grid for billing, quality assurance of hydrogen at refuelling stations and equations of state for carbon dioxide in carbon capture and storage facilities. The European metrology network for energy gases for the first time provides a platform where metrology institutes can work together to develop a harmonised strategy, prioritise new challenges, and share expertise and capabilities to support the European energy gas industry to meet stringent EU targets for climate change and emissions reductions.

Single photon sources for quantum radiometry: a brief review about the current state-of-the-art

Single-photon sources have a variety of applications. One of these is quantum radiometry, which is reported on in this paper in the form of an overview, specifically of the current state of the art in the application of deterministic single photon sources to the calibration of single photon detectors. To optimize single-photon sources for this purpose, extensive research is currently carried out at the European National Metrology Institutes (NMIs), in collaboration with partners from universities. Single-photon sources of different types are currently under investigation, including sources based on defect centres in (nano-)diamonds, on molecules and on semiconductor quantum dots. We will present, summarise, and compare the current results obtained at European NMIs for single-photon sources in terms of photon flux, single-photon purity, and spectral power distribution as well as the results of single-photon detector calibrations carried out with this type of light sources.

EURAMET Key Comparison EURAMET.M.D-K4.2020: Hydrometer calibration comparison from 600 kg/m3 to 2000 kg/m3

Main textThis report presents the results of the key comparison EURAMET.M.D-K4.2020 (EURAMET 1496) that covered the calibration of high-resolution hydrometers for liquid in the density range 600 kg/m3 to 2000 kg/m3 at the reference temperature of 20 oC. Nine laboratories participated in this key comparison, eight European national metrology institutes and one from Asia Pacific metrology: NIM from China. The participating laboratories were initially divided into two petals linked by two density laboratories: INRIM and PTB. In each petal, four similar transfer standards, hydrometers in the density range 600 kg/m3 to 2000 kg/m3 are used.The equipment used by the participants was found to have very similar characteristics. Most of the declared relative uncertainties were within the 5x10-5.The results of all participated laboratories have been linked to the CIPM key comparison CCM.D-K4 by INRIM and PTB. Discrepant results have been reported for three laboratories, which, however, do not affect their CMCs.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

A comparison of relative humidity calibration facilities at temperatures up to 170 °C

Three European National Metrology Institutes (NMIs), VSL, LNE-CETIAT and INRiM, extended their relative humidity calibration capabilities to temperatures up to 170 °C, dew-point temperatures up to 150 °C and pressures up to 600 kPa. In order to test the equivalence of the respective calibration set-ups, 4 commercial high-temperature relative humidity sensors were exchanged among the three NMIs and calibrated at different combinations of relative humidity (19 %rh to 70 %rh), air temperature (100 °C to 170 °C) and pressure (100 kPa to 500 kPa), realizing dew-point temperatures of either 81.5 °C or 127 °C. The initial and final measurements at VSL showed that the stability of the selected sensors was sufficient for comparing the different calibration set-ups. The results of the comparison showed that VSL and LNE-CETIAT facilities agreed within their claimed uncertainties (≤0.3 %rh), while discrepancies of up to 4 %rh were observed between VSL and INRiM facilities.

A study to develop a robust method for measuring the detection efficiency of free-running InGaAs/InP single-photon detectors

The challenges faced in a comparison of measuring the detection efficiency of free-running InGaAs/InP single-photon avalanche detectors (InGaAs/InP SPAD) were studied by four European National Metrology Institutes (NMIs) meeting at a single laboratory. The main purpose of this study is to develop a trustable measurement technique and to provide a snapshot of the methods used by the four NMIs for measuring such photon-counting detectors at telecom wavelengths in order to establish proper procedures for characterising such devices. The detection efficiency measurements were performed using different experimental setups and reference standards with independent traceability chains at the wavelength of 1550 nm. A dedicated model to correct the dead time and dark count effects on the SPAD’s free-running counting process was developed, allowing the correct value of the photon rate impinging on the detector to be recovered from simple ratemeter measurements. The detection efficiency was measured for mean photon number per pulse between 0.01 and 2.4, corresponding to photon rates between approximately 1100 photon/s and 193,000 photon/s, respectively. We found that the measured values reported by the participants are all consistent within the stated uncertainties, proving the consistency of the measurement approach developed.

Design and Validation of the MBW Standard Humidity Generators

MBW Calibration AG (MBW) is the Designated Institute (DI) for humidity appointed by the Federal Institute of Metrology, METAS. MBW currently offers calibration and measurement capabilities (CMC) for frost/dew-point hygrometers by comparison with precision chilled-mirror transfer standards that have been calibrated using the primary standards of leading European National Metrology Institutes or DI. The design, construction and validation of two standard humidity generators to be used as the Swiss national standards for the primary realization of frost/dew-point temperature in the range from − 90 °C to + 95 °C are presented and discussed. The generators are operated as continuous flow “single-pressure” generators in the range from − 80 °C to − 10 °C with saturation over ice and from 0.5 °C to + 95 °C with saturation over water. Additionally, they are used in “two-pressure” mode for saturation over ice down to frost-point temperatures of − 90 °C and down to − 20 °C for saturation over water. The main saturators of both generators have been designed to fit in commercially available calibration baths with either ethanol or distilled water as the heat transfer fluid for saturator temperatures below and above 0 °C, respectively. Saturator temperature is measured using standard platinum resistance thermometers and a purpose-built precision thermometer. Pressure measurements are taken with gauge pressure transducers and a separate barometric sensor, to reduce the influence of the atmospheric pressure on the measurement of the pressure ratio and make full use of the correlation of pressure measurements and enhancement factors when operating in two-pressure mode. A totally automated pre-saturation and flow control system facilitates the calibration of state-of-the-art chilled-mirror transfer for standards without manual readjustment of the generated flowrate to ensure a constant volumetric flow at the conditions of the mirror. The uncertainty budget leading to the CMC for frost/dew-point temperature realization is presented in the context of the experimental validation performed. The results in the overlapping range of both generators are presented and used as further evidence of the saturation efficiency of both standards.

The European Research Project on Metrology for Hydrogen Vehicles - MetroHyVe

A large hydrogen infrastructure is currently in development across Europe. However, the industry faces the dilemma that they are required to meet certain measurement requirements set by European legislation that cannot currently be followed due to the lack of available methods and standards. The EMPIR Metrology for Hydrogen Vehicles project will be the first large scale project of its kind that will tackle the four measurement challenges that currently prevent the industry from meeting requirements set by International Standards such as flow metering, quality control, quality assurance and sampling. This paper presents a brief overview of the specific objectives of the project and focuses on the flow metering work package and the presentation of its planned tasks, which comprise laboratory and measurements in the field. Laboratory work will assess the use of substitute fluids to hydrogen to provide a safer and more cost effective method for the type approval of Hydrogen Refuelling Stations (HRS). To be able to link laboratory work to field testing, mobile primary standards will be developed and the design of a field testing primary standard will be addressed. The aim is to inform what the European national metrology institutes are currently developing in the field of hydrogen flow metering and quality control of HRS.

Speeding-up Scientific Knowledge Transfer and Improvement of Capabilities of emerging European National Metrology Institutes and Designated Institutes in the field of thermal measurements: Benefits and Impacts

Within the frame of a European project called Eura-Thermal, the general objective was to upgrade the regional metrological infrastructure (Bosnia & Herzegovina, Croatia, Ireland, Serbia…) with new capabilities, especially in the field of thermal measurements. This paper highlights the strategy used for improving in the short term, scientific knowledge transfer and the capabilities of different emerging institutes. Furthermore, as a main output, the impacts and benefit for Industry and for the end-users are also presented as examples.

Exploitation of a novel thermo-invariant multi-feature bar for high-precision CMMs and machine tool testing

A novel thermo-invariant Multi-Feature Bar (MFB) for Machine Tools (MTs) geometric errors' identification has been designed and manufactured. The proposed design of the MFB allows extracting three intrinsic parameters: one linear positioning and two straight-ness errors. The calibration of the MFB was performed on accurate coordinate measuring machines (CMMs) by applying the reversal technique, in order to separate the geometric errors between the MFB and the CMMs. Furthermore , an intercomparison was conducted between four European National Metrology Institutes (LNE, PTB, CMI, UM) to evaluate the reliability of the proposed calibration methodology and the geometric stability of the proposed material standard with respect to a detailed technical procedure. The collected results show sufficient dimensional stability over time.

Calibration of Contact Surface Thermometers

Some of the national metrology institutes (NMIs) have developed devices which generate a standard surface temperature under conditions which resemble, as closely as possible, those encountered during the routine use of surface sensors. Several comparisons of measurements among European NMIs, coordinated by MKEH, were undertaken in order to validate the methods used and the reference conditions. The characteristics of the reference surface significantly influence the measurement error, as its temperature, inclination and thermophysical properties. This paper presents a method of determining a correction function, containing the effects of these factors. The measurements have been taken in the temperature range from \(100\,^{\circ }\hbox {C}\) to \(500\,^{\circ }\hbox {C}\), with a specific sensor having an inflexible head. The technique developed of MKEH is suitable for quantifying the effect of the above parameters, optimizing the surface temperature measurements in this regard.

Development of the High-Temperature Dew-Point Generator Over the Past 15 Years

At VSL a humidity generator was designed and constructed in the early 1990s. This generator was of the re-circulating-single-pressure type. Over the years, the generator has been thoroughly revised and several critical components have been replaced. Among others the pre-saturator and the change from re-circulation to single-pass mode. Validating experiments showed that the range of the new setup could be extended from $$70\,{^{\circ }}\hbox {C}$$ to $$95\,{^{\circ }}\hbox {C}$$ dew-point temperature, and the last modification allows an uncertainty of $$0.048\,{^{\circ }}\hbox {C}$$ (k = 2) at the maximum temperature. In 2009 the setup was used in the Euramet-T-K8 humidity intercomparison at temperatures up to $$95\,{^{\circ }}\hbox {C}$$ . In the period from 2003 to 2015, four state-of-the-art chilled mirror hygrometers were regularly calibrated with the generator. One of these was also calibrated with the primary dew-point standards of several other European National Metrology Institutes, which made it possible to link the VSL generator to the generators used in these institutes. An analysis of the results of these calibrations shows an agreement in calibration capabilities within $$0.01\,{^{\circ }}\hbox {C}$$ with PTB and NPL.

Intercomparison of flatness measurements of an optical flat at apertures of up to 150 mm in diameter

Recently, a scientific comparison of flatness measuring instruments at European National Metrology Institutes (NMIs) was performed in the framework of EURAMET. The specimen was a well-polished optical surface with a maximum measurement aperture of 150 mm in diameter. Here, we present an evaluation concept, which allows the determination of a mean flatness map taking into account different lateral resolutions of the instruments and different orientations of the specimen during measurement. We found that all measurements are in agreement with the mean flatness map within the uncertainty intervals stated by the participants. The aim of this scientific comparison is to specify an appropriate operation and evaluation procedure for future comparisons.

EURAMET.M.P-S9 / EURAMET 1170, LOOP2. Comparison in the negative gauge pressure range -950 to 0 hPa

This report gives the results of a comparison of pressure standards of seven European National Metrology institutes in the range of negative gauge pressure from -950 hPa to 0 hPa.This comparison was piloted by LNE and was carried out from January 2011 to March 2012. This work is a part of the EURAMET project 1170 and is registered as a supplementary comparison EURAMET.M.P-S9. The transfer standard used was a pressure monitor RPM4 A160Ks manufactured by DH Instruments Inc., with a resolution of 0.1 Pa. The reference values have been determined from the weighted mean of the deviations reported by the participants for each specified pressure. Seventy-three of the seventy-seven values (96%) reported by the laboratories agree with the reference values within the expanded uncertainties with a coverage factor k = 2.Main textTo 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 CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Interlaboratory comparison on 137Cs activity concentration in fume dust

Abstract A comparison was conducted, between 11 European National Metrology Institutes and EC-JRC, on measurement of 137Cs activity concentration in fume dust. As test material an activity standard produced from real contaminated fume dust was used. The standard material consisted of 13 cylindrical samples of compressed fume dust. The material contained 137Cs and 60Co of reference activity concentrations of (9.72±0.10) Bq/g and (0.450±0.018) Bq/g, respectively, for the reference date of 1 June 2013, determined using the comparison results. The organization and results of the intercomparison, as well as the process of obtaining reliable reference values are presented.

Status and Strategy for Moisture Metrology in European Metrology Institutes

Measurement of moisture in materials presents many challenges, due to diverse measuring principles, sample interactions with atmosphere, and variation in what is measured (either water content alone or moisture including other liquids). Calibrations are variously referenced to published standard methods, primary calibration facilities, or certified reference materials, but each of these addresses limited substances and ranges of measurement. Overall, metrology infrastructure is not as fully developed or coherent for this field as it is for many other areas of measurement. In order to understand the metrology needs and to support developments, several European national metrology institutes (NMIs) have undertaken some collaborative activities. These have included a “cooperation in research” project for sharing of information, a survey of moisture capabilities at NMIs, the formulation of a strategy for moisture metrology at the NMI level, and a funded research project to develop improved metrology for the moisture field. This paper summarizes the information gathered, giving an overview of the status of moisture metrology at NMIs, and it reports a proposed strategy to improve the current situation.

Measurement uncertainty consideration in the case of nonlinear models for precision length measurement

The requirements on the precision lengths and precision load measurement rise due to the rapid technical development, in particular of nanotechnologies and precision optics. According to the roadmap "Dimensional metrology for micro- and nanotechnology" of the European National Metrology Institutes (iMERA)2 in the next few years "traceable 2D (3D) metrology at (sub)-nm accuracy over several 100 mm range" will be required.