Centre for Metrology and Accreditation

Abstract We delve into theoretical and experimental considerations for determining the spectral bidirectional transmittance distribution function (BTDF) of thick samples across a broad viewing zenith angle range. Nominally, BTDF is defined as the ratio of transmitted radiance to incident irradiance measured from the same plane. However, when employing thick samples for BTDF measurements, the viewing plane of the transmitted beam may shift from the front to the rear surface of the sample, altering the measurement geometry compared to using the sample front surface as the reference plane. Consequently, the viewing zenith angle from the sample rear surface increases relative to the sample front surface, and the sample-to-detector-aperture distance decreases by an amount corresponding to the sample thickness. We introduce a method for determining the BTDF of thick samples, considering the transformation of practical measurement results to a scenario where the measurements are conducted at a very large distance from the sample. To validate the method, we utilize a BTDF facility equipped with two instruments that significantly differ in their sample-to-detector-aperture distances. We evaluate the impact of a 2 mm sample thickness on the BTDF by assessing the ratio of transmitted and incident radiant fluxes as a function of viewing zenith angle relative to the sample rear surface. The evaluation is conducted in the wavelength range from 550 nm to 1450 nm in 300 nm steps, and in the viewing zenith angle range from −70° to 70° in 5° steps. Measurements are performed in-plane at an incident zenith angle of 0°. It is concluded that consistent determination of BTDF of a thick sample is possible by converting the experimental parameters of the real measurements at relatively short distances from the sample to correspond to those that would be obtained from measurements at very large distances from the sample.

Main textIn this supplementary comparison depths of six v-shaped grooves with nominal values 5/20/50/200/600 and 900 μm were measured. The depths were measured according to ISO 5436-1. The PTB nickel depth setting standard was used as reference standard. PTB and MIKES measures all depths, CEM 2 and UME 3 larger depths. The results with associated uncertainties were in agreement.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 CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

An ultra-stable light source and optical detection set-up for high-precision measurements of 114Cd absorption lines is presented. The experimental setup for ultraviolet light at 326.2 nm is described with an aim toward primary thermometry.

This report present the results of the EURAMET inter-comparison carried out to compare the calibration of thermocouples from 419,527 °C (freezing point of Zn) up to 1492 °C (melting point of the Pd-C eutectic). This inter-comparison is intended to be used to support the calibration and measurement capabilities (CMCs) of the participants in the calibration of thermocouples.The comparison was organized in three loops with nineteen participating laboratories and it allowed the performance of the measurement either in fixed points and/or by comparison. The method used to analyse the results of the comparison was the generalized weighted mean that takes into account the full covariance matrix that includes correlations between the participants which have similar traceability sources and between measurements performed by the same laboratory (i.e. the pilots that performed measurements at the beginning and at the end of each loop and the measurements performed by the same laboratory in fixed points and by comparison at the same calibration point).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 CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Within the framework of the European Metrology Research Programme (EMRP), tools for the calculation of measurement uncertainties have been developed. The Joint Research Project (JRP) 63 of the "SI Broader Scope II" (SIB) call of the EMRP is entitled: "Force traceability within the meganewton range". The project was started in July 2013 and had a duration of 36 months. The aim of the SIB63 project was to improve the traceability of the force measurement especially in the meganewton range. This paper presents the results of work package 4 “Improved dissemination of the SI unit of force”. The tools developed by the partners are available from the website of the project.

The key comparison EURAMET.L-K8.2013 on roughness was carried out in the framework of a EURAMET project starting in 2013 and ending in 2015. It involved the participation of 17 National Metrology Institutes from Europe, Asia, South America and Africa representing four regional metrology organisations. Five surface texture standards of different type were circulated and on each of the standards several roughness parameters according to the standard ISO 4287 had to be determined. 32 out of 395 individual results were not consistent with the reference value. After some corrective actions the number of inconsistent results could be reduced to 20, which correspond to about 5% of the total and can statistically be expected. In addition to the material standards, two softgauges were circulated, which allow to test the software of the instruments used in the comparison. The comparison results help to support the calibraton and measurement capabilities (CMCs) of the laboratories involved in the CIPM MRA.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 CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Real-time detection and generation of single microwave photons would be important in many quantum technology applications. For single-microwave-photon sources, much of the groundwork has been done already within the framework of circuit quantum electrodynamics (cQED) in the frequency range 4 GHz – 8 GHz. However, currently there are no detectors that can reliably resolve single microwave photon events, unlike at optical frequencies. In June 2013, we started a joint research project to develop both microwave detectors and sources working at the single-photon level as a final goal. All devices operate at cryogenic temperatures, most of them below 100 mK. We also aim at improving the performance of other cryoelectronic quantum devices by understanding and eliminating the detrimental effects caused by microwave radiation. The work is done in project MICROPHOTON of the European Metrology Research Programme (EMRP). The goals and status of the project will be described in the presentation.

We report about technology of fabrication and optimization of a gas sensor based on epitaxial graphene. Optimized graphene/metal contact configuration exhibited low contact resistance. Complementary annealing of graphene sensor after each gas exposure led to significant improvement in the sensing performance. The response of the annealed sensor to the nitrogen dioxide (NO2) was tenfold higher than that of an as-fabricated graphene sensor. NO2concentration as low as 0.2 parts per billion (ppb) was easily detectable. Devices have high signal-to-noise ratio. The detection limit of the graphene sensor was estimated to be 0.6 ppt (parts per trillion). The present technology with additional annealing improves the performance of the graphene based sensor and makes it suitable for the environmental nitrogen dioxide gas monitoring.

Abstract:We are developing a novel gravimetric moisture measurement system for wood based materials. The measurement principle is based on combining the Loss on Drying (LoD) method with complementary water loss detection systems. In our setup, air flows through a sample container containing sample material from 5 g to 400 g. The sample container is placed in a thermally controlled enclosure, which can be heated up to 200 °C. The mass loss of water is studied by weighing the sample before and after heating, and by monitoring the humidity of the air exiting the sample container with a capacitive sensor. The amount of evaporated water is also studied by trapping the water from the through-passed air in a separately weighed cold trap. The material samples can be exposed to different heating cycles in order to study different binding degrees of the water. This paper presents the measurement concept and the setup.