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Richard P.,Federal Institute of Metrology METAS | Fang H.,Bureau International des Poids et Mesures BIPM | Davis R.,Bureau International des Poids et Mesures BIPM
Metrologia | Year: 2016

The redefinition of the kilogram, expected to be approved in the autumn of 2018, will replace the artefact definition of the kilogram by assigning a fixed numerical value to a fundamental constant of physics. While the concept of such a change is pleasing, the mass community as represented by the Consultative Committee for Mass and Related Quantities (CCM) was faced with a number of technical and procedural challenges that needed to be met in order to profit in any meaningful way from the proposed change. In the following, we outline these challenges and how the CCM has met and is meeting them. We focus especially on what the mass community requires of the new definition and the process by which the CCM has sought to ensure that these needs will be met. © 2016 BIPM & IOP Publishing Ltd.

Goma C.,Paul Scherrer Institute | Goma C.,ETH Zurich | Hofstetter-Boillat B.,Federal Institute of Metrology METAS | Safai S.,Paul Scherrer Institute | Voros S.,Federal Institute of Metrology METAS
Physics in Medicine and Biology | Year: 2015

This paper presents a method to experimentally validate the beam quality correction factors (kQ) tabulated in IAEA TRS-398 for proton beams and to determine the kQ of non-tabulated ionization chambers (based on the already tabulated values). The method is based exclusively on ionometry and it consists in comparing the reading of two ionization chambers under the same reference conditions in a proton beam quality Q and a reference beam quality 60Co. This allows one to experimentally determine the ratio between the kQ of the two ionization chambers. In this work, 7 different ionization chamber models were irradiated under the IAEA TRS-398 reference conditions for 60Co beams and proton beams. For the latter, the reference conditions for both modulated beams (spread-out Bragg peak field) and monoenergetic beams (pseudo-monoenergetic field) were studied. For monoenergetic beams, it was found that the experimental kQ values obtained for plane-parallel chambers are consistent with the values tabulated in IAEA TRS-398; whereas the kQ values obtained for cylindrical chambers are not consistent - being higher than the tabulated values. These results support the suggestion (of previous publications) that the IAEA TRS-398 reference conditions for monoenergetic proton beams should be revised so that the effective point of measurement of cylindrical ionization chambers is taken into account when positioning the reference point of the chamber at the reference depth. For modulated proton beams, the tabulated kQ values of all the ionization chambers studied in this work were found to be consistent with each other - except for the IBA FC65-G, whose experimental kQ value was found to be 0.6% lower than the tabulated one. The kQ of the PTW Advanced Markus chamber, which is not tabulated in IAEA TRS-398, was found to be 0.997 ± 0.042 (k = 2), based on the tabulated value of the PTW Markus chamber. © 2015 Institute of Physics and Engineering in Medicine.

Marti K.,Federal Institute of Metrology METAS | Fuchs P.,Federal Institute of Metrology METAS | Russi S.,Federal Institute of Metrology METAS
Metrologia | Year: 2013

The new cleaning techniques of low-pressure hydrogen plasma and UV/ozone were studied on stainless steel used in the manufacture of high-quality weight pieces, rhodium and gold using x-ray photoelectron spectroscopy (XPS) and a quartz crystal microbalance (QCM) for direct mass determination. Both cleaning techniques were directly compared with respect to the achieved cleanliness, the remaining contaminants, the speed of action and the change in mass. Both techniques proved to be very efficient for the removal of carbon compounds. Hydrogen plasma additionally also reduces oxides and oxygen compounds, whereas UV/ozone leads to an oxidation of weight steel and rhodium. Plasma cleaning is two to four times faster than UV/ozone and the remaining amount of contamination is lower. Cyclic cleaning using both techniques by turns clearly demonstrated that both modern methods delivered for each technique different but repeatedly and reversibly the same surface chemical state. The change in mass monitored directly with a QCM is in good agreement with the XPS data. The recontamination of the gold-coated quartz crystal after hydrogen plasma was monitored with the microbalance in situ. The gain in mass due to the accumulation of carbonaceous contamination can be explained by a self-limited growth model proposed recently. © 2013 BIPM & IOP Publishing Ltd.

Fuchs P.,Federal Institute of Metrology METAS | Marti K.,Federal Institute of Metrology METAS | Russi S.,Federal Institute of Metrology METAS
Metrologia | Year: 2013

The removal of a high mercury contamination on a Pt reference mass by thermal desorption was studied directly by x-ray photoemission spectroscopy (XPS). Subsequently the contamination mechanism was investigated. Samples of PtIr and AuPt exposed to vapour of mercury in air were studied using XPS and gravimetric mass determination. We find an extremely rapid mercury contamination which takes place within minutes and reaches an initial equilibrium state after 2 h to 4 h. Roughly 1 to 2 monolayers of mercury adsorbs directly on the metal surface. A natural contamination of carbon and oxygen compounds is at the top. Due to the accumulation of mercury, we find a gain in mass which corresponds to 20 g to 26 g for a PtIr standard. XPS data from a historical Pt standard give strong evidence for further average mercury accumulation of (1.3 ± 0.1) g/year during a period of more than a century. This can be explained by a two-step mechanism presented in this study. The speed of contamination depends on the initial surface conditions. Polishing activates the surface and results in an enhanced accumulation of mercury. Natural contamination by C and O can delay but not prevent contamination. We further demonstrate that the mercury contamination can be removed by both hydrogen plasma and thermal desorption. The removal of mercury by hydrogen plasma can directly be attributed to the synthesis of gaseous mercury dihydrides at low pressures. © 2013 BIPM & IOP Publishing Ltd.

Richard P.,Federal Institute of Metrology METAS
XXI IMEKO World Congress "Measurement in Research and Industry" | Year: 2015

The 25th General Conference on Weights and Measures (CGPM) adopted its Resolution 1 "On the future revision of the SI" [1]. According to this Resolution, new definitions for the kilogram, the ampere, the kelvin and the mole will be based on fixed numerical values of selected constants. The Consultative Committee for Mass and Related Quantities (CCM) and the Consultative Committee for Units (CCU) established a joint roadmap in order to ensure that all necessary steps are completed in time for the 26th CGPM in 2018. The paper present these steps and reviews the situation with the criteria proposed by the CCM in the light of the recent progress and published results.

Agustoni M.,Federal Institute of Metrology METAS | Mortara A.,Federal Institute of Metrology METAS
CPEM 2016 - Conference on Precision Electromagnetic Measurements, Conference Digest | Year: 2016

The working principle and the architecture of a calibration system for commercial test sets, operating with IEC 61850 standard, is described. Essential requirements for such devices are: generating a signal, in analog and digital form, with the most reliable synchronization possible. Preliminary studies show how the setup presents encouraging results in performing calibration measurements for test sets. © 2016 IEEE.

Overney F.,Federal Institute of Metrology METAS | Jeanneret B.,Federal Institute of Metrology METAS
CPEM 2016 - Conference on Precision Electromagnetic Measurements, Conference Digest | Year: 2016

A fully automated impedance simulator is used to calibrate a commercial LCR-meter over the whole complex plane. The amplitude of the synthesized impedance has been varied over 5 orders of magnitude i.e. from 100 Ω to more than 10 MΩ and the phase angle from-90 deg to +90 deg. The first measurements have been carried out at a frequency of 1 kHz, however, the bandwidth of the instrument is 20 kHz. © 2016 IEEE.

Mester C.,Federal Institute of Metrology METAS | Siegenthaler S.,Federal Institute of Metrology METAS
CPEM 2016 - Conference on Precision Electromagnetic Measurements, Conference Digest | Year: 2016

In recent years, test sets for both conventional and analogue non-conventional instrument transformers have been made commercially available. Reference transformers are still of the conventional type. Therefore, test sets need to compare an analogue signal of a conventional level with another analogue signal of a different order of magnitude or, in the case of current-To-voltage transformers, even a different quantity. Traditional designs based on bridge techniques are not suitable for this application. This paper describes a new calibrator that reaches uncertainties of the order of 10 × 10-6 while being suitable for the calibration of test sets for non-conventional analogue instrument transformers and fully computer-controlled. © 2016 IEEE.

Hoffmann J.,Federal Institute of Metrology METAS
CPEM Digest (Conference on Precision Electromagnetic Measurements) | Year: 2014

This paper presents an overview of the applications of near field scanning microwave microscopes. The difficulties and approaches to obtain calibrated and traceable measurements with a scanning microwave microscope are discussed. © 2014 IEEE.

Hof C.,Federal Institute of Metrology METAS
42nd International Congress and Exposition on Noise Control Engineering 2013, INTER-NOISE 2013: Noise Control for Quality of Life | Year: 2013

The hearing ability of persons can be objectively tested by means of audiometry. Thereby the persons' response to sounds of known levels is compared with tabulated values from otologically normal persons. To generate such known sounds an audiometer equipped with calibrated headphones or a calibrated free field facility is needed. As a result, a hearing loss may be assessed and quantified. In order to identify the medical condition causing a hearing loss, complementary measurements are needed. Bone conduction allows one to stimulate the inner ear directly. If carried out at defined levels, audiologists can discriminate between conductive and sensorineural hearing losses. Calibrations of bone conductors are crucial for these measurements to provide meaningful results. They have to be performed under equivalent mechanical loads as presented by typical human heads. This is achieved with artificial mastoids, the properties of whose have been specified in a standard (IEC 60318-6:2007) for several decades (since 1971). Unfortunately, the specification of the standard includes implicitly the physical properties of a testing device (impedance head) which is no longer commercially available. This situation is conceptually disturbing and will lead to problems for conformance testing in the future. Copyright© (2013) by Austrian Noise Abatement Association (OAL).

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