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Sittakul V.,King Mongkuts University of Technology Thonburi | Pasakawee S.,National Institute of Metrology Thailand
IET Science, Measurement and Technology | Year: 2016

This study proposes a setup configuration for leakage signal measurement in a radio frequency or microwave system. The leakage signal usually influences on such a system and basically is defined as a source of uncertainties. In this configuration, a programmable attenuator is used as the device under test (DUT) in the system to fully study the leakage signal effects. The DUT is initially characterised in terms of phase as a function of attenuation before used to represent any electronic device with a specific insertion loss and frequency. Then, the amplitude and phase of the leakage signal are found and compared with the mathematical model to confirm the obtained results. Finally, the maximum amplitude deviation of the leakage signal is found and used to calculate as a limit of leakage error. © 2016. The Institution of Engineering and Technology.

Su C.-M.,Industrial Technology Research Institute of Taiwan | Lin W.-T.,Industrial Technology Research Institute of Taiwan | Masri S.,National Institute of Metrology Thailand
Mapan - Journal of Metrology Society of India | Year: 2011

This paper presents the establishment and verification of a primary low-pressure gas flow standard with the capacity of 0.005 L/min to 24 L/min (at 23 °C and 101.325 kPa), newly established at National Institute of Metrology of Thailand (NIMT). This facility is a mercury-sealed piston prover consisting of three precision-machined glass cylinders. Flow measurement can be carried out manually or semi-automatically. The electronics were installed in a separate console to minimize their thermal impact on the gas temperature. Special care was taken in designing the facility to ensure sound and representative gas pressure and temperature measurement. The relative expanded uncertainty of mass flow measurement was evaluated to be less than 0.13%. To verify the measurement capability and performance of the new facility, a bilateral comparison with the piston prover at Center for Measurement Standards (CMS), Taiwan was conducted. The transfer standard used was a set of three critical flow venturis with dedicated thermometers. Eight flow rates of dry air ranging from 42 mL/min to 14.5 L/ min at 0 °C and 101.325 kPa (0.055 g/min to 18.87 g/min) were tested. Comparison results showed that the E n values for the flow measurements at NIMT with reference to CMS were all well less than unity, demonstrating good agreement between the two participants. © 2011 Metrology Society of India.

Petchpong P.,National Institute of Metrology Thailand
International Journal of Thermophysics | Year: 2011

Impurities are a major source of uncertainty in the temperature of a thermometry metal fixed point (of the order of 1 mK). A better understanding of the impurity effect is required to improve top-level metrological thermometry. This investigation reports on some unusual effects of antimony doped into a high-purity (99.9999%) tin sample. The change in temperature and shape of the melting and freezing curves of the tin, caused by low concentrations of the Sb dopant, were measured in order to test the interpolation of previous data. Most historical experiments have worked at much higher impurity concentrations-say of the order of 100 ppm-and in arrangements that are not used on a day-to-day basis in a metrology laboratory. These measurements on the tin were done after doping at mass fractions of approximately (1 and 25) parts per million by weight (ppmw) of antimony. Repeated melting and freezing curves, before and after doping, confirmed the reproducibility of the temperature measurements in this tin cell. The freezing temperature of the tin after adding antimony was higher than for "pure" tin. However, the temperature change was less than expected, being an average (+0.06±0.03) mK • ppmw -1. Samples from the tin were analyzed by glow discharge mass spectrometry (GD-MS) before and after doping to detect the distribution of all the impurity elements. If the dopant level detected by GD-MS was used, then a value of (0.18 or 0.29) mK • ppmw -1 was calculated (much closer to the value interpolated from earlier works). There was evidence that the thermal history of metal phase transitions can cause considerable segregation of some impurities and that the effects of this segregation can be clearly seen on the shape of the melting curves of tin doped with Sb. (The segregation might be more pronounced as Sb forms a peritectic in tin, i.e., a "positive" impurity which increase the phase transition temperature). © 2011 Springer Science+Business Media, LLC.

Petchpong P.,National Institute of Metrology Thailand
International Journal of Thermophysics | Year: 2011

This work describes the deliberate doping of high purity (99.9999 %) aluminum with titanium (99.8 %) impurity and the effect of this on the temperature of the aluminum liquid-solid phase transition (660.323 °C). The aluminum sample was in the form of an ~0.3 kg ingot (that would normally be used to realize an ITS-90 fixed point) which was doped at ~0.9 ppmw Ti and ~1.8 ppmw Ti (mass fraction in parts per million by mass). Measurements were made with procedures and equipment normally used in a metrological thermometry laboratory, rather than using special arrangements. Samples cut from the aluminum ingot were chemically analyzed by glow discharge mass spectrometry (GD-MS) before doping and after the second doping (to 1.8 ppmw). The experimental temperature offsets were compared with those calculated by interpolation from a reference book value using the mass of dopant introduced, or the chemical analysis data. The results showed that the aluminum temperature increased after adding 0.9 ppmw Ti, but apparently the temperature did not change after further doping to 1.8 ppmw Ti; which was unexpected. The first result suggested that titanium impurity increases the Al transition temperature by +5.1 mK • ppmw -1. However, using the (total) temperature offset and the GD-MS value for the (total) added Ti impurities, then one calculates a value of 3.4 mK • ppmw -1 (much closer to a reference book value). The experimental undoped liquid-solid transition curves were also compared against theoretical curves (calculated using a theoretical model "MTDATA"). This suggested that GD-MS may not be "exposing" all the active impurities (some of which may be "hidden" in the carbon background). © 2011 Springer Science+Business Media, LLC.

Garcia-Sartal C.,University of Santiago de Compostela | Taebunpakul S.,LCG Group | Taebunpakul S.,Imperial College London | Taebunpakul S.,National Institute of Metrology Thailand | And 4 more authors.
Analytical and Bioanalytical Chemistry | Year: 2012

Edible seaweed consumption is a route of exposure to arsenic. However, little attention has been paid to estimate the bioaccessibility and/or bioavailability of arsenosugars in edible seaweed and their possible degradation products during gastrointestinal digestion. This work presents first use of combined inductively coupled plasma mass spectroscopy (ICP-MS) with electrospray ionization tandem mass spectrometry (ESI-MS/MS) with two-dimensional HPLC (size exclusion followed by anion exchange) to compare the qualitative and quantitative arsenosugars speciation of different edible seaweed with that of their bioavailable fraction as obtained using an in vitro gastrointestinal digestion procedure. Optimal extraction conditions for As species from four seaweed namely kombu, wakame, nori and sea lettuce were selected as a compromise between As extraction efficiency and preservation of compound identity. For most investigated samples, the use of ammonium acetate buffer as extractant and 1 h sonication in a water bath followed by HPLC-ICP-MS resulted in 40-61% of the total As to be found in the buffered aqueous extract, of which 86-110% was present as arsenosugars (glycerol sugar, phosphate sugar and sulfonate sugar for wakame and kombu and glycerol sugar and phosphate sugar for nori). The exception was sea lettuce, for which the arsenosugar fraction (glycerol sugar, phosphate sugar) only comprised 44% of the total extracted As. Interestingly, the ratio of arsenobetaine and dimethylarsinic acid to arsenosugars in sea lettuce extracts seemed higher than that for the rest of investigated samples. After in vitro gastrointestinal digestion, approximately 11-16% of the total As in the solid sample was found in the dialyzates with arsenosugars comprising 93-120% and 41% of the dialyzable As fraction for kombu, wakame, nori and sea lettuce, respectively. Moreover, the relative As species distribution in seaweed-buffered extracts and dialyzates was found to be very similar. Collection of specific fractions from the size-exclusion column to be analysed using anion-exchange HPLC-ESI-MS/MS enabled improved chromatographic selectivity, particularly for the less retained arsenosugar (glycerol sugar), facilitating confirmation of the presence of arsenosugars in seaweed extracts and dialyzates. Using this approach, the presence of arsenobetaine in sea lettuce samples was also confirmed. © 2011 Springer-Verlag.

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