National Institute of Metrology Thailand

Pathum Thani, Thailand

National Institute of Metrology Thailand

Pathum Thani, Thailand
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Ongrai O.,National Institute of Metrology Thailand | Elliott C.J.,National Physical Laboratory United Kingdom
International Journal of Thermophysics | Year: 2017

In 2015, NIMT first established a Co-C eutectic temperature reference (fixed-point) cell measurement capability for thermocouple calibration to support the requirements of Thailand’s heavy industries and secondary laboratories. The Co-C eutectic fixed-point cell is a facility transferred from NPL, where the design was developed through European and UK national measurement system projects. In this paper, we describe the establishment of a Co-C eutectic fixed-point cell for thermocouple calibration at NIMT. This paper demonstrates achievement of the required furnace uniformity, the Co-C plateau realization and the comparison data between NIMT and NPL Co-C cells by using the same standard Pt/Pd thermocouple, demonstrating traceability. The NIMT measurement capability for noble metal type thermocouples at the new Co-C eutectic fixed point (1324.06∘C) is estimated to be within ±0.60K (k= 2). This meets the needs of Thailand’s high-temperature thermocouple users—for which previously there has been no traceable calibration facility. © 2017, Springer Science+Business Media New York.


Sanponpute T.,National Institute of Metrology Thailand | Wattong C.,National Institute of Metrology Thailand
Acta IMEKO | Year: 2017

The aim of this study was to fabricate a torque transducer that has two measurement signals in order to simultaneously measure torque value and check its stability. The transducer has two sensing bodies aligned in the same measurement axis. The first sensing body was designed to be a measurement signal and the second sensing body was designed to be a check signal. The capacity of the check signal was designed at least two times larger than that of the measurement signal. Transducers with various capacity ratios of check signal and measurement signal with ratios 2:1, 3:1 and 4:1 were fabricated. To confirm the assumption that the fabricated transducers are able to check stability by themselves, they were overloaded from 100 % to 800 % of their capacity. The experimental results showed that the function ratios of the check signal and measurement signal corresponds with the stability measured by a torque standard machine. Thus it can be used to predict stability. Stabilities of the check and zero signals are used to find the appropriate capacity ratio. It was found that the stability of check and zero signals showed drift caused by overload. Therefore, the capacity ratio should be designed at least 3:1 for transducers made of steel and 2:1 for transducers made of aluminum. A prototype of a torque transfer wrench was also made according to the concept of the torque transducer with check standard combination. Experimental results corresponds with results of the torque transducer. It could also check the stability itself. © 2017 IMEKO.


Manoi A.,National Institute of Metrology Thailand | Saunders P.,New Zealand Institute for Industrial Research and Development
International Journal of Thermophysics | Year: 2017

The size-of-source effect (SSE) for six infrared (IR) thermometers with direct reading of temperature was measured in this work. The alternative direct method for SSE determination, where the aperture size is fixed and the measurement distance is varied, was used in this study. The experimental equivalence between the usual and the alternative direct methods is presented. The magnitudes of the SSE for different types of IR thermometers were investigated. The maxima of the SSE were found to be up to 5 %, 8 %, and 28 % for focusable, closed-focus, and open-focus thermometers, respectively. At 275∘C, an SSE of 28 % corresponds to 52∘C, indicating the severe effect on the accuracy of this type of IR thermometer. A method to realize the calibration conditions used by the manufacturer, in terms of aperture size and measurement distance, is discussed and validated by experimental results. This study would be of benefit to users in choosing the best IR thermometer to match their work and for calibration laboratories in selecting the technique most suitable for determining the SSE. © 2017, Springer Science+Business Media New York.


Ranusawud M.,National Institute of Metrology Thailand | Ranusawud M.,King Mongkut's University of Technology Thonburi | Limsuwan P.,King Mongkut's University of Technology Thonburi | Somthong T.,National Institute of Metrology Thailand | Vacharanukul K.,National Institute of Metrology Thailand
Precision Engineering | Year: 2013

The environment parameters, i.e. temperature, pressure, humidity and CO2 concentration affecting the refractive index of air play an important role on the long gauge block measurement using interferometer. In this paper, the environment parameters in a measurement chamber had been continuously investigated more than 24 h. The refractive index was then calculated by using an updated Edlén equation. The stability of the refractive index of air in the experiment is 0.1 × 10-6 with the measurement uncertainty of 4.32 × 10-8 at the confidential level k = 2. While the sensitivity of the pressure of air was small, it was an evidence that the pressure of air mainly contributed to the stability of the refractive index of air due to its large variation. Furthermore, the calculated refractive index of air was employed to correct the length of long gauge blocks. The correction for 1 m long gauge block in interferometer system is 0.270 mm, 0.269 mm and 0.267 mm which are respectively based on the three laser wavelengths at 532 nm, 633 nm and 780 nm. © 2013 Elsevier Inc.


Somkun S.,National Institute of Metrology Thailand | Moses A.J.,University of Cardiff | Anderson P.I.,University of Cardiff
IEEE Transactions on Magnetics | Year: 2012

Magnetostriction of nonoriented electrical steel was measured under rotating flux magnetization conditions which occur in AC electrical machine stator cores, and compared with the magnetostriction calculated from a model based on a mechanical elasticity analogy. Shear magnetostriction and magnetostriction perpendicular to the magnetization direction are accounted for in the model which leads to an accurate representation of magnetostriction throughout the electrical steel lamination plane. This has the potential for improving the accuracy of stator core deformation and vibration calculations. © 2012 IEEE.


Heamawatanachai S.,University of Utah | Heamawatanachai S.,National Institute of Metrology Thailand | Bamberg E.,University of Utah
International Journal of Machine Tools and Manufacture | Year: 2010

This paper presents an analytical, ductile cutting force model of a novel micromachining tool that is based on micro-orbital motion of a single-point tool tip. The single-point tool tip used in this study is a single crystal diamond stylus that consists of a cone section of 50° and a spherical tip with radius less than 1 μm. The tool is actuated by a piezo tube that generates a high frequency micro-orbital motion of a single-point tool tip in a circular trajectory. Unlike conventional micromilling, where the cutting occurs at the edges of the tool flutes, a single-point tool may utilize any point on the circumference surface of the tool tip. Also, due to its extreme negative rake angle at small depths of cut, the technique can machine brittle materials such as silicon in the ductile regime. Experiments were performed on an aluminum alloy (AL2024) to obtain the specific cutting force and the coefficient of friction in order to calculate the cutting forces in all 3 axes and to verify the model. © 2010 Elsevier Ltd. All rights reserved.


Petchpong P.,National Institute of Metrology Thailand | Head D.I.,21 Chelsea Close
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 | Head D.I.,21 Chelsea Close
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.


Saenkhum N.,National Institute of Metrology Thailand | Sanponpute T.,National Institute of Metrology Thailand
Measurement: Journal of the International Measurement Confederation | Year: 2016

This paper presents the optimized parameters of continuous (quasi-static) torque calibration by comparing it with the step-by-step (purely static) calibration facilities in order to prove the influence of the procedural conditions on the uncertainty of calibration. The filter setting (low pass Bessel: 0.2. Hz, 1.25. Hz, 5. Hz and 10. Hz) and speed of applying torque (≈140-35. s/F.S.) were varied to examine the effects of both parameters on the measurement results and to optimize the continuous calibration. The measurement was made by a torque calibration machine (TCM) with two reference torque transducers and the HBM MGC. plus ML30B amplifier system.The results of this experiment show the relative deviation between the step-by-step and continuous calibration within ±0.02% of reading that was enough for class 0.2 torque measuring devices (DIN 51309) and torque transfer wrench (DAkkS-DKD-R 3-7) calibration. For the step-by-step measurement, the duration time in each torque step (from applying torque to data record) must be adequate for processing time interval of the filter. For the continuous measurement, the speed of applying torque and filter setting should be optimized for best measurement capability. © 2016 Elsevier Ltd.


Buajarern J.,National Institute of Metrology Thailand | Somthong T.,National Institute of Metrology Thailand | Ali S.H.R.,National Institute for Standards of Egypt | Tonmeuanwai A.,National Institute of Metrology Thailand
International Journal of Precision Engineering and Manufacturing | Year: 2013

Error separation technique is the one of the best ways for accurate and precise determination of roundness form. The multi-step technique is an important method of roundness error separation. Many national metrology institutes (NMIs), industrial calibration laboratories and research institutes have been using the multi-step method for high precision and high accuracy in roundness measurement. Number of step used by various institutes is different. In this paper, effect of number of step employed for the error separation was investigated. The results of these experiments successfully indicate that number of step used in multi-step method plays an important role to the accuracy level of the roundness measurement result. In order to achieve accuracy at the ultra-high level, at least 10 steps should be employed using multi-step method to satisfy the geometrical form of roundness measurement. © 2013 Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg.

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