NMi VSL Research Articles

Adiabatic Calorimetry as Support to the Certification of High-Purity Liquid Reference Materials

The certification of high-purity liquid reference materials is supported by several analytical techniques (e.g., gas chromatography, liquid chromatography, Karl Fischer coulometry, inductively coupled plasma mass spectrometry, differential scanning calorimetry, adiabatic calorimetry). Most of them provide information on a limited set of specific impurities present in the sample (indirect methods). Adiabatic calorimetry [1] complementarily provides the overall molar fraction of impurities with sensitivity down to few μmol · mol−1 without giving any information about the nature of the impurities present in the sample (direct method). As the combination of adiabatic calorimetry with one (or more than one) indirect chemical techniques was regarded as an optimal methodology, NMi VSL developed an adiabatic calorimetry facility for the purity determination of high-purity liquid reference materials [2]. Within the framework of collaboration with NMIJ, a benzene-certified reference material (NMIJ CRM 4002) from NMIJ was analyzed by adiabatic calorimetry at NMi VSL. The results of this measurement are reported in this paper. Good agreement with the NMIJ-certified purity value (99.992 ± 0.003) cmol · mol−1 was found. The influence of different data analysis approaches (e.g., extrapolation functions, melting ranges) on the measurement results is reported. The uncertainty of the measured purity was estimated.

ITS-90 Scale Realization on the New Radiation Thermometer Calibration Facility at NMi VSL

In the first half of 2005, Nederlands Meetinstituut Van Swinden Laboratorium B.V. (NMi VSL) redesigned their facilities for radiation thermometry in a new laboratory building and an opportunity arose to implement new measurement methods. The new facility is used for ITS-90 realization and dissemination in the temperature range from − 50 °C to 3,000 °C. A study was performed to compare a silver-point realization with a fixed-point blackbody radiator (FP-BBR) to a sodium heat-pipe blackbody radiator (HP-BBR) traceable via a HTSPRT to a contact thermometry silver point. It was found that the fixed-point realization transfer to the sodium heat pipe results in an uncertainty from 0.2 K to 2.4 K for the ITS-90 over the temperature range from 961.78 °C to 3,000 °C.

Isotope and Impurity Content in Water Triple-Point Cells Manufactured at NMi VSL

The isotopic and impurity content of 15 water triple-point cells, manufactured at NMi VSL in the past three years, were investigated. The isotopic analyses were performed on water specimens sampled at three different stages of the manufacturing process. This allowed us to separate and quantify the influence of the source water and of the manufacturing process (distillation, degassing) on the final isotopic composition of the water in the cells. Inductively coupled plasma mass spectrometry (ICPMS) was conducted on selected water samples to investigate the potential contamination of the source water during the manufacturing process, and to evaluate the impact of impurities on the water triple-point temperature. The temperature differences among the manufactured cells were measured, and correlations between the observed differences and the results of isotope and chemical analysis were studied.

The Dutch National Realization of the ITS-90 over the Range 13.8033 K–273.16 K

The facility constructed at NMi VSL to realize the ITS-90 in the capsule standard platinum resistance thermometer range (CSPRT, 13.8033–273.16K) is presented. To demonstrate the performance of our facility, the results of a recent measurement campaign are reported, in which 3 NMi VSL CSPRTs were calibrated in the range 13.8–273.16K at all of the fixed points required by the ITS-90. The uncertainty of the calibration of the CSPRTs at each of the fixed points is evaluated in accordance with the most recent recommendations of the Consultative Committee for Thermometry and its Working Groups 1 and 3.

Novel calibration method for filter radiometers

We present a new method for the calibration of inhomogeneous irradiance or illuminance meters. Using this method, a lux meter equipped with a mosaic filter was calibrated with an estimated uncertainty of 0.15 % (1 σ). A preliminary illuminance comparison has been performed between the new scale and a lamp-based scale maintained at the Nederlands Meetinstituut Van Swinden Laboratorium (NMi VSL). The observed difference is equal to the uncertainty of this comparison, 0.4 %.

International comparison of power measurements at 33 GHz (GT-RF/92-4)

A measurement comparison of effective efficiency has been carried out between eight national metrology laboratories at 33 GHz in rectangular waveguide IEC R320. Two waveguide thermistor mounts were measured. The following national laboratories participated: BNM-LCIE (France), NIST (U.S.), NRC (Canada), KRISS (Korea), CSIRO (Australia), PTB (Germany), NMi VSL (The Netherlands), and NPL (U.K.). The Bureau National de Metrologie-Laboratoire Central des Industries Electriques (France) acted as the pilot laboratory for the comparison. Excellent harmony is observed between results given by the participants, especially for the item LCIE-92021.

Using 10 V Josephson voltage standards to estimate the uncertainty of Zener voltage references as traveling standards

In anticipation of a European comparison of 10 V Josephson array voltage standards (EUROMET project 429 led by the NMi VSL), the BIPM and the BNM-LCIE Josephson standards have been compared by means of Zener traveling references. A mean difference of 5 parts in 10/sup 9/ has been found with a standard uncertainty of 6 parts in 10/sup 9/. The results show that the performance of the Zener references could be the main cause of uncertainty in such a comparison.