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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. Source

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). Source

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. Source

Baumann H.,Federal Institute of Metrology METAS | Eichenberger A.,Federal Institute of Metrology METAS | Cosandier F.,Federal Institute of Metrology METAS | Jeckelmann B.,Federal Institute of Metrology METAS | And 3 more authors.
Metrologia | Year: 2013

The kilogram is the last unit of the international system of units (SI) still based on a material artefact, the international prototype of the kilogram (IPK). The comparisons made in the last hundred years have clearly revealed a long-term relative drift between the IPK and the official copies kept under similar conditions at the Bureau International des Poids et Mesures. A promising route towards a new definition of the kilogram based on a fundamental constant is represented by the watt balance experiment which links the mass unit to the Planck constant h. For more than ten years, the Federal Institute of Metrology METAS has been actively working in the conception and development of a watt balance experiment. This paper describes the new design of the Mark II METAS watt balance. The metrological characteristics of the different components of the experiment are described and discussed. © 2013 BIPM & IOP Publishing Ltd. Source

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. Source

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