National Institute Of Metrology Thailand Research Articles

Enhancing particle size characterization performance through proficiency testing program: result and insights from inter-laboratory comparison

The proficiency testing (PT) for particle size characterization by inter-laboratory comparison was organized by the dimensional metrology department of the National Institute of Metrology Thailand (NIMT). This program aims to enhance and to expand the efficiency and capability of testing laboratories in the field of particle size characterization using various techniques, including atomic force microscope (AFM), transmission electron microscope (TEM), scanning electron microscope (SEM), and dynamic light scattering (DLS). The measurement range covers nanometer to micrometer scale. These instruments are importance for research and development especially to nanotechnology related industries. The PT program was conducted in 2022 where five artifacts were used: monodispersed gold nanoparticle (diameter 20 nm), monodispersed polystyrene particle (diameter 100 nm, 500 nm, and 1500 nm) and monodispersed silica oxide particle (diameter 100 nm). The monodispersed polystyrene particles, diameter 100 nm and 1500 nm are certified reference materials (CRMs). These two artefacts were used as the reference to evaluate accuracy of participant laboratories. The other 3 artefacts are reference material under development. Hence, the assigned values were calculated from consensus among all participants. To evaluate the performance of participant laboratories, En values and z-scores were calculated for each artefact and each measuring technique. The assessment of participant performance through performance scores allows the participant to determine how accurate and how appropriate the measurement results and measurement uncertainties evaluation are. From the results, unsatisfied results can be categorized into three scenarios. First, the measurement uncertainties were not appropriately evaluated. Secondly, measurands obtained from all measuring techniques are not the same. Lastly, the magnification used in microscopy techniques plays a crucial role to resolution and accuracy of size determination.

Comparison of four-terminal-pair 1 pF, 10 pF, 100 pF and 1000 pF capacitance standards at frequencies of 10 kHz, 100 kHz, 1 MHz and 10 MHz (APMP.EM-S15)

Main textIn order to calibrate an LCR meter, metrological traceability of capacitance above 10 kHz becomes more and more important. For this reason, NIM (National Institute of Metrology, China)，NPLI (National Physical Laboratory, India) and NIMT (National Institute of Metrology, Thailand) have carried out research on capacitance metrology from 10 kHz to 10 MHz.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 CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

GNSS time and frequency transfers through national positioning, navigation and timing infrastructure

Abstract GNSS signals have been a practical time transfer tool to realise a Coordinated Universal Time (UTC) and set civilian clocks around the world with respect to this atomic time standard. UTC time scale is maintained by the International Bureau of Weights and Measurements (BIPM) adjusted to be close to a time scale based on the Earth’s rotation. In Thailand, the official atomic time clocks are maintained by the National Institute of Metrology Thailand (NIMT) to produce UTC(NIMT) and Thailand standard time which is always 7 hours ahead of UTC(NIMT) because of the time zone differences between Greenwich and Bangkok. National Positioning, Navigation and Timing (PNT) infrastructure comprises of GNSS geodetic receivers uniformly distributed to continually observe GNSS signals, mainly for geodetic survey applications both real-time and post-processing services. NIMT is involved in order to provide time link to UTC and to determine the characteristics of GNSS receiver internal clocks; namely, fractional frequency offset and frequency stabilities by applying the GNSS time transfer techniques of common-view algorithms. Monitored time differences with respect to UTC(NIMT) are achieved from selected 4 ground stations in different parts of the country with observations of 21 days in order to determine the frequency stability at 1-day and 7-day modes. GNSS standard log files; in RINEX format, at these receivers are transformed into a time transfer standard format; CGGTTS, used to compute the time differences between two stations, the fractional frequency offset and the frequency stability. Averaged fractional frequency offsets are 2.8 × 10 − 13 Hertz/Hertz 2.8\times {10^{-13}}\hspace{2.38387pt}\text{Hertz/Hertz} and computed Allan deviation is around 1.5 × 10 − 13 Hertz/Hertz 1.5\times {10^{-13}}\hspace{2.38387pt}\text{Hertz/Hertz} for an averaging time of 1 day. The comparison of the national time scale and receiver clock offsets of every receivers in this national GNSS PNT infrastructure could be accomplished through common-view time transfer using GNSS satellites to maintain the time link of geodetic active control points to UTC as well as to determine receiver internal clock characteristics.

Collaboration between TISTR and NIMT: An application of the pressure metrology in an air speed measurement

This paper describes a collaboration between Thailand Institute of Science and Technological Research (TISTR) and National Institute of Metrology Thailand (NIMT) in an application of a differential pressure measurement to an air speed measurement. The aim of the collaboration is to link the measurement of an air speed by a pitot static tube anemometer at TISTR to the measurement of a differential pressure at NIMT. Upon completing the project, TISTR’s pitot tube anemometer is traceable to NIMT’s force balance piston gauge. TISTR’s pitot tube anemometer in combination with its Eiffel-type wind tunnel can be employed as a calibration system for an anemometer. The result of the collaboration leads to a lower cost of maintaining TISTR’s traceability in air speed measurement.

Final report of CCQM-K86.c. Relative quantification of genomic DNA fragments extracted from a biological tissue

Key comparison CCQM-K86.c was performed to demonstrate the capacity of National Metrology Institutes (NMIs) and Designated Institutes (DIs) in the determination of the relative quantity of two specific genomic DNA fragments present in a canola powder. The study provides direct support for the following measurement claim: "Quantification of the ratio of the number of copies of specified intact sequence fragments of a length up to 150 nucleotides following extraction from an unprocessed, high fat/oil ground seed matrix, with a copy number ratio from 0.001 to 1".The study was carried out under the auspices of the Nucleic Acids Working Group (NAWG) of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM) and was jointly coordinated by the National Research Council of Canada (NRC) and the EU Joint Research Centre, Geel (JRC). The following laboratories (in alphabetical order) submitted measurement results in this key comparison study: Centro Nacional de Metrología, Mexico ("CENAM"); D.I. Mendeleyev Institute of Metrology, Russia ("VNIIM"); EU Joint Research Centre, Geel (JRC); Hong Kong Government Laboratory ("GLHK"); Instituto Nacional de Metrología de Colombia ("INM"); LGC (United Kingdom); National Institute of Biology, Slovenia ("NIB"); National Institute of Metrology, P.R. of China ("NIM China"/"NIMC" [figures]); National Institute of Metrology, Thailand (NIMT); National Measurement Institute, Australia ("NMIA"); National Metrology Institute of Japan, AIST, Japan ("NMIJ"); National Metrology Institute of Turkey ("TÜBITAK").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 CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Establishment of Thailand’s national primary vacuum standard by a static expansion method

A novel primary standard system for a vacuum pressure calibration has been established at the National Institute of Metrology, Thailand (NIMT). The system, which cover the pressure range from 1.3 • 10-1 Pa up to 1.3 • 103 Pa is based on the static expansion method. By the series of re-expansion, the range could be extended to lower calibration pressures. The facility consists of two small and one large vessels, which provide an expansion ratio by a factor of approximately 102 to 103 for a single expansion and more for a multiple one. Six platinum resistance thermometers are attached to the vessel to ensure the correction of the non-isothermal effect during an expansion. The system could deliver the expanded (k = 2) relative uncertainties under 0.6% of reading at the lowest operating pressure. The measurement results of the system were verified by comparing with the calibration results of the capacitance diaphragm gauge (CDG) from Physikalisch-Technische Budensanstalt (PTB). The En ratios represent an excellent agreement between NIMT and PTB calibration results.

The Development of Small Water Flow Facility at National Institute of Metrology, Thailand

The flow and volume of liquid laboratory of the National Institute of Metrology, Thailand (NIMT) has developed the latest facility which covers the liquid flow measurement ranges from (10 – 1,000) g/h. This facility has been developed according to the need of high accuracy equipment in several industries such as pharmaceutical products, fuel cells, semiconductor and medical devices. For accuracy purposes, the gravimetric method is decisively implemented as the main principle of the calibration rig. It comprises of three main parts; water supply system, weighing system and data acquisition system. Practically, the capability of the facility is confirmed via a transfer standard. With high accuracy and repeatability, the Coriolis mass flow controllers were selected as the transfer standard. The facility can provide the best capability of calibration, CMC, at 0.30% of reading. Moreover, the evidence of unofficial comparison between NIMT and Federal Institute of Metrology, METAS, Switzerland, has confirmed this capability via the degree of equivalence, En ratio. The En ratios represent that the comparison of the flow rates from (10 – 1,000) g/h between NIMT and METAS is agreed.

Competency evaluation on electrolytic conductivity measurement in Indonesia by an unofficial bilateral comparison between RCChem-LIPI and NIMT

The Research Centre for Chemistry—Indonesian Institute of Sciences (RCChem-LIPI) organized an unofficial bilateral comparison on electrolytic conductivity with the Electrochemistry Laboratory—National Institute of Metrology Thailand (NIMT). The electrochemical laboratory RCChem-LIPI, as a Designated Institute for Chemical Metrology in Indonesia, started to develop the secondary method on electrolytic conductivity measurement in 2016. Therefore, the purpose of this unofficial bilateral comparison was to test the ability of RCChem-LIPI laboratory and see the capacity building progress in doing the conductivity measurement. There were two samples containing potassium chloride prepared by RCChem-LIPI, and both samples had the electrolytic conductivity value in the range of 1000 µS cm−1 to 20000 µS cm−1. The samples were sent to NIMT and then measured at the same time duration. The results were compared, analyzed and evaluated based on their assigned values. The assigned values were 15309 µS cm−1 and 6650 µS cm−1 for samples A and B, respectively. The deviation for each measurement result was determined, and the uncertainties were also calculated from the data reported by both laboratories. The data evaluation and analysis confirm that the measurement results for both participant laboratories were in agreement with the assigned value of this unofficial bilateral comparison.

Quality Assurance of Rice and Paddy Moisture Measurements in Thailand

A bilateral comparison in moisture measurement between the National Institute of Metrology Thailand (NIMT) and the Central Bureau of Weights and Measures (CBWM) was organized for quality assuring of rice and paddy moisture measurement in Thailand. The bilateral comparison was conducted by using the same batch of sample and moisture meter as transfer device. It consisted of two parts: moisture measurement in rice and in paddy. A rice moisture meter belonging to CBWM and rice standards prepared at the nominal moisture content of 10 %, 12 %, 14 % and 16 % at NIMT, were used for rice moisture comparison, while a paddy moisture meter belonging to NIMT and paddy standards prepared at the nominal moisture content of 12 %, 14 %, 16 % and 18 % at CBWM, were used for paddy moisture comparison. Both laboratories measured the moisture content of a sample by using the standard method in ISO 712 and used that sample to calibrate a moisture meter by means of the method based on ISO 7700-1. Since the moisture content of the sample can change during the comparison, correction values in moisture content between the standard value and the reading value from the moisture meter are used as calibration results for the comparison evaluation. For the rice moisture comparison, differences in the correction value measured by the two laboratories vary from 0.18 % to 0.46 %, with their combined comparison uncertainty of 0.37 % ( $$\hbox {k}= 2)$$ . The main contribution to the difference comes from the standard values from both laboratories differing from 0.27 % to 0.53 %, as the rice standard was found to drift in moisture content less than 0.05 %. Similarly to the rice moisture comparison, differences in the correction value for the paddy moisture measurement range from 0.08 % to 0.56 % with the combined comparison uncertainty of 0.38 % ( $$\hbox {k} = 2)$$ , whereas the stability in moisture content of the paddy sample at NIMT was found to be within 0.12 %.

Improving the Traceability of Meteorological Measurements at Automatic Weather Stations in Thailand

A joint project between the National Institute of Metrology Thailand (NIMT) and the Thai Meteorology Department (TMD) was established for improving the traceability of meteorology measurements at automatic weather stations (AWSs) in Thailand. The project aimed to improve traceability of air temperature, relative humidity and atmospheric pressure by implementing on-site calibration facilities and developing of new calibration procedures. First, new portable calibration facilities for air temperature, humidity and pressure were set up as working standard of the TMD. A portable humidity calibrator was applied as a uniform and stable source for calibration of thermo-hygrometers. A dew-point hygrometer was employed as reference hygrometer and a platinum resistance thermometer (PRT) traceable to NIMT was used as reference thermometer. The uniformity and stability in both temperature and relative humidity were characterized at NIMT. A transportable pressure calibrator was used for calibration of air pressure sensor. The estimate overall uncertainty of the calibration setup is 0.2 K for air temperature, 1.0 % for relative humidity and 0.2 hPa for atmospheric pressure, respectively. Second, on-site calibration procedures were developed and four AWSs in the central part and the northern of Thailand were chosen as pilot stations for on-site calibration using the new calibration setups and developed calibration procedures. At each station, the calibration was done at the minimum temperature, average temperature and maximum temperature of the year, for air temperature, 20 %, 55 % and 90 % for relative humidity at the average air temperature of that station and at a one-year statistics pressure range for atmospheric pressure at ambient temperature. Additional in-field uncertainty contributions such as the temperature dependence on relative humidity measurement were evaluated and included in the overall uncertainty budget. Preliminary calibration results showed that using a separate PRT probe at these AWSs would be recommended for improving the accuracy of air temperature measurement. In case of relative humidity measurement, the data logger software is needed to be upgraded for achieving higher accuracy of less than 3 %. For atmospheric pressure measurement, a higher accuracy barometer traceable to NIMT could be used to reduce the calibration uncertainty to below 0.2 hPa.

Report on AFRIMETS supplementary comparison: platinum resistance thermometer and digital thermometer calibrations against ITS-90 over the range -50 °C to 450 °C (AFRIMETS.T-S1)

A Regional Metrology Organization (RMO) supplementary comparison of platinum resistance thermometer and digital thermometer (AFRIMETS.T-S1) was carried out by the National Metrology Institute of South Africa (NMISA), National Institute for Standards Egypt (NIS), National Metrology Institute of Ethiopia (NMIE), Kenya Bureau of Standards (KEBS), National Institute of Metrology Thailand (NIMT), Uganda National Bureau of Standards (UNBS), Tanzania Bureau of Standards (TBS), Mauritius Standards Bureau (MSB) and Seychelles Bureau of Standards (SBS) between March 2008 and October 2010. The temperature range of the inter comparison is -50 °C to 450 °C. The results of this comparison are reported here, along with descriptions of the Artefacts and devices used during measurement. This report also presents the uncertainty budget. The results are analysed and normalized error (En) values are reported.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).

Pilot Comparison of Radiance Temperature Scale Realization Between NIMT and NMIJ

A pilot comparison of radiance temperature scale realizations between the National Institute of Metrology Thailand (NIMT) and the National Metrology Institute of Japan (NMIJ) was conducted. At the two national metrology institutes (NMIs), a 900 nm radiation thermometer, used as the transfer artifact, was calibrated by a means of a multiple fixed-point method using the fixed-point blackbody of Zn, Al, Ag, and Cu points, and by means of relative spectral responsivity measurements according to the International Temperature Scale of 1990 (ITS-90) definition. The Sakuma–Hattori equation is used for interpolating the radiance temperature scale between the four fixed points and also for extrapolating the ITS-90 temperature scale to 2000 \(^{\circ }\)C. This paper compares the calibration results in terms of fixed-point measurements, relative spectral responsivity, and finally the radiance temperature scale. Good agreement for the fixed-point measurements was found in case a correction for the change of the internal temperature of the artifact was applied using the temperature coefficient measured at the NMIJ. For the realized radiance temperature range from 400 \(^{\circ }\)C to 1100 \(^{\circ }\)C, the resulting scale differences between the two NMIs are well within the combined scale comparison uncertainty of 0.12 \(^{\circ }\)C (\(k=1\)). The resulting spectral responsivity measured at the NIMT has a comparable curve to that measured at the NMIJ especially in the out-of-band region, yielding a ITS-90 scale difference within 1.0 \(^{\circ }\)C from the Cu point to 2000 \(^{\circ }\)C, whereas the realization comparison uncertainty of NIMT and NMIJ combined is 1.2 \(^{\circ }\)C (\(k=1\)) at 2000 \(^{\circ }\)C.

Development of metrology for pH measurement in Thailand

It has not been long that metrology is well accepted as an important part in analytical chemistry since it helps the chemists to receive the best measurement and accurate results with traceability. The National Institute of Metrology Thailand (NIMT), which is a public agency under the supervision of the Ministry of Science and Technology, not only focuses on physical standards but also provides and maintains standards in chemical field. pH measurement is one of the most widely used in the laboratories including industries and medical area in Thailand. The chemical laboratory starts working on the project with the objective of disseminating an accurate result in routine pH measurement. In 2002, the laboratory provided a service in calibration of pH meter and organized the first local interlaboratory comparison program (NIMT-C-ILC-1: pH buffer) in pH measurement. There were three buffer solution samples in the range of acid, neutral, and base. A total of 44 laboratories participated in this program. The NIMT chemical laboratory also participated in the proficiency testing program that was conducted by PSB Corporation Testing Group in Singapore. In 2003, NIMT started research in preparation of secondary buffers by using highly accurate pH meters with glass electrode systems. The laboratory produced three secondary buffers, which were pH 4.01, 6.86, and 9.18 with uncertainty 0.020 pH at 25 ◦ C. The competence of the laboratory was shown by the measurement results of the pilot study (APMP.QM-P06), which was organized by the APMP electrochemical analysis working group (EAWG/TCQM)

APMP.EM-S6: Bilateral supplementary comparison of resistance

A bilateral supplementary comparison of resistance, APMP.EM-S6, was conducted between the National Institute of Metrology Thailand (NIMT) and the CSIRO National Measurement Laboratory of Australia (NML). The comparison covered seven values of resistance, 0.1 Ω, 1 Ω, 100 Ω, 10 kΩ, 100 kΩ, 1 MΩ and 100 MΩ. The 0.1 Ω resistor was a YEW type 2792, the 100 MΩ resistor was an IET type SRC and the other five resistors were Fluke type 742A.The resistors were supplied by NIMT, and NML was the pilot laboratory for the comparison. The measurements for the comparison were made between December 2003 and April 2004.The resistors were measured on three separate occasions by NIMT and between each of these occasions the resistors were sent to NML for measurement. The resistors of nominal values 0.1 Ω, 1 Ω, 100 Ω and 10 kΩ were measured as four-terminal resistors while the 100 kΩ, 1 MΩ and 100 MΩ resistors were measured as two-terminal resistors.The quantity En (the absolute value of the difference between the values obtained at the two laboratories divided by the root sum square of the expanded uncertainties of the two values) was calculated for each resistance value used in the comparison. In all cases En was less than 0.5.Main text. 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 kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the APMP, according to the provisions of the Mutual Recognition Arrangement (MRA).