Metrology Laboratory Research Articles

Least squares approach to standard platinum resistance thermometer subrange inconsistency reduction with redundant gallium and indium fixed points

The International Temperature Scale of 1990 (ITS-90) defines several different and sometimes overlapping temperature subranges. Where overlap occurs, different definitions of the temperature t90 exist that have equal status but produce different results. This discrepancy is called type 1 non-uniqueness or subrange inconsistency (SRI).In this paper, the SRI of the water-aluminum/water-zinc (SRI(Al:Zn)) and of the water-zinc/water-tin (SRI(Zn:Sn)) subranges of the ITS-90 were investigated for three cases. In the first case, the calculations followed the ITS-90 prescribed procedure. In the second case, the SPRT was calibrated at all fixed points of the subrange and its deviation function was then determined using the least squares method. In the third case, the least squares method was weighted by the uncertainties at each of the fixed points. One benefit of the least squares approach over exact interpolation is the reduction in uncertainty propagated from the fixed points. The calculations were applied to a large ensemble of 30 different SPRTs from the database of the Laboratory of Metrology and Quality at the University of Ljubljana, Slovenia. The sample consisted mainly of SPRTs manufactured by Fluke, Rosemount and AccuMac.The difference in the mean and standard deviation of SRI(Al:Zn) for the three cases was small, amounting to less than 0.06 mK. On the other hand, the mean of SRI(Zn:Sn) decreased from 0.73 mK to 0.01 mK and the standard deviation decreased from 1.25 mK to 0.43 mK when the weighted least squares approach was applied. Furthermore, the total propagated uncertainty from the fixed points decreased in particular temperature ranges with weighted least squares, especially from 50 °C to 300 °C (by about 50% compared to the ITS-90 case) and to a lesser extent from 400 °C to 600 °C (by about 10% compared to the ITS-90 case). The contribution of the difference in the uncertainty propagation between pairs of subranges to SRI was estimated to be at least 50% in all cases. According to the presented results, it can be advantageous to calibrate the SPRT at all available fixed points in the selected temperature subrange and then determine its deviation function using the weighted least squares method.

Developments of interlaboratory comparisons on pressure measurements in the Philippines

The National Metrology Laboratory of the Philippines, Industrial Technology Development Institute under the Department of Science and Technology (ITDI-DOST) offered first of its kind interlaboratory comparison in pressure measurement in the country following a demand survey identifying the gaps in proving the competency of local calibration laboratories. This paper presents the development in implementing the two interlaboratory comparisons in the Philippines with six years interval using the same pressure artefact. With its many objectives, the program also aimed to provide these laboratories access to proficiency testing (PT) to comply with the ISO/IEC 17025 requirements. Comparatively, while both are considered successfully implemented, the improved awareness and commitment to quality of the participants and the enhanced competency of the pilot laboratory in implementing such activity are a few of the enumerated factors instigating the increase in the number of participants as well as those obtaining satisfactory results in the latter PT. The interlaboratory comparison schemes offered aimed at sustaining the demands of metrology stakeholders and continuously develop this service to support further progress in the calibration and measurement capabilities of local laboratories in the country.

Estimation of scattered radiation influence on neutron beams at a calibration laboratory using Monte Carlo simulation of a long counter

At the Neutron Calibration Laboratory (LCN) of IPEN/CNEN, a 241AmBe source was used to test and calibrate neutron detectors. The neutrons emitted by the source reach the detector as intended, but they also scatter undesirably from the building's floor, ceiling, and walls, leading to indirect detection. A Long Counter (LC) detector was modeled using the MCNPX Monte Carlo code. The objective of this study was to measure the contribution of scattered radiation at the LCN / IPEN, and to determine the fluence rate, at different points in the calibration room at source-to-detector distances of 100 cm and 150 cm; subsequently, the results were compared with those of the Brazilian Laboratory of Metrology of Ionizing Radiation (LNMRI). The results show that the fluence rates of LCN / IPEN are comparable to those of this neutron laboratory for the 100 and 150 cm source-to-detector distances using a 241AmBe source (37 GBq). The results show that the calibration of neutron detectors should be performed at distances less than 100 cm, where the contribution of scattered radiation is within the 40% limit recommended by ISO 8529-1.

Синтез трехканального ПИД-регулятора для управления трехзонной среднетемпературной печью

Currently, in metrological laboratories there is a need to transfer temperature units from standards of the highest category by reproducing the fixed points of the international temperature scale. The reproduction process of fixed point involves heating, melting, overheating and solidification of the metal and can sometimes take more than one working day. The purpose of this work was to create and practically test an algorithm that takes into account heat flows in a three-zone furnace for uniform heating and relatively fast reaching the solidification area. Over the past twenty years, several algorithms have been used making it possible to go through all four stages within one working day. This paper describes a practically tested algorithm for controlling three-zone furnaces for reproducing the fixed points of the temperature scale in the range from 156.5985 °C to 1084.62 °C. It takes into account the requirements for maintaining the minimum temperature gradient along the height of the fixed point cell. This algorithm has been used in the furnaces of the West Siberian branch of FSUE "VNIIFTRI". The controller model is based on the principles of automatic control theory using a multi-channel discrete proportional-integral-derivative or PID controller. The model was modified in accordance with the system structure. The main idea is to represent the model of a three-zone furnace as a three-channel control object with mutual influence between the channels. The corresponding controller model is a three-channel control system. In each channel of it there is a PID controller. Depending on the phase of the playback process, the three-channel controller changes its structure and tunes its coefficients. Such a structure made it possible to achieve sufficient productivity of the furnace.

Analysis of Ambient Air Mercury Levels in The Mercury Laboratory and Metrology Centre for Environmental Quality Instrumentation Standardization

Today the use of heavy metals can be found in almost all aspects of life. However, the use of heavy metals causes a process of bioaccumulation of toxins from heavy metals into the body. One type of heavy metal that is very toxic is Mercury (Hg). According to the list of hazardous substances published by the Agency for Toxic Substances and Disease Registry (ATSDR), mercury occupies the third position among 275 substances harmful to human health. The mercury and metrology laboratory is a laboratory that functions to test mercury levels in both water, soil and air matrix samples. In carrying out a test or measurement of Mercury levels, employees at the Mercury and Metrology Laboratory of Centre for Environmental Quality Instrumentation Standardization (PSIKLH) always use Mercury in the process, so there is a possibility that the air in the Mercury and Metrology laboratory of PSIKLH is contaminated with Mercury because of the activities in it. That is the reason of researchers to test mercury levels in the ambient air around the Mercury laboratory and Metrology PSIKLH. This study aims to determine the level of mercury in the ambient air around the mercury and metrology laboratory of PSIKLH. The method used in this study is a quantitative analysis method using the Mercury Analyzer WA-5F from Nippon Instruments Corporation (NIC) which includes curve making, sampling, and measuring mercury levels in the sample. This research was conducted at the Mercury and Metrology Laboratory of PSIKLH. Based on research that was conduct, it shows that the highest concentration of mercury in the ambient air around the PSIKLH Mercury and Metrology Laboratory is found in the Atomic Absorption Spectrophotometer (AAS) room, the sampling equipment room, and the Hg tool room. Mercury levels contained in the three rooms were more than 0.01 mg/m3. However, mercury levels in the Mercury and Metrology Laboratory are still classified as normal because they have not passed the threshold of 0.05 mg/m3.

Conformity Assessment in Senegal: Conformity Tests in Laboratories as the Basis for Quality Infrastructure

This work focuses on quality infrastructure in the solar photovoltaic field in Senegal. On the one hand, it deals with the improvement of the quality infrastructure and on the other hand, conformity assessment accompanied by metrology and performance tests on batteries. We felt it was necessary to revisit the concepts of quality infrastructure and conformity assessment. Then in the improvement of this infrastructure metrology tests were carried out on electrical components by performing maximum error calculations to check the conformity on the voltage, the current, frequency and resistance of electrical quantities at a metrology laboratory, the African Laboratory of Metrology and Testing (LAME). We have also carried out compliance tests on batteries with the measuring equipment of the Laboratory for Quality Control of Solar photovoltaic components (LCQS), a laboratory for testing photovoltaic solar components in Senegal. The study of the batteries covers two (2) elements in one cycle with a nominal capacity of 1080Ah. The capacities calculated after the tests performed on the two (2) elements are respectively C1(t)=1223Ah and C2(t)=1318Ah.

Geometrical and thermal optimization of cylinder-conical blackbody cavities to uniform radiance temperature profiles in the infrared

Large-area blackbody cylinder conical cavities are generally used as primary radiation sources for calibrating and characterizing radiation thermometers and quantitative thermal imagers in the infrared, both in metrology laboratories or for industrial applications. The radiation temperature of the emitted radiation depends on effective emissivity and surface (contact) temperature. The instrument’s field of view generally only covers the cavity bottom since this is where contact temperature is best measured. A non-uniform effective emissivity profile at the bottom poses a problem if instruments with a different field of view have to be calibrated with the same blackbody. Spatial uniformity depends principally on the cone angle and temperature gradient along the cavity. In this paper, we analyse blackbody optimization in terms of uniform radiance temperature profiles as a function on geometric parameters and temperature. For the isothermal case, we conclude that angles between 160° and 170° are the optimum, depending on intrinsic emissivity and length-to-diameter ratio of the cavity. For non-isothermal cavities, the effect of the temperature gradient on uniformity is relatively small, with only the temperature near the bottom proving significant. The use of multi-zone maintenance furnaces would allow temperature gradients to be designed that can improve uniformity in addition to geometric optimization.

Fast neutron response characterization of an EJ-276 plastic scintillator for use as a neutron monitor

EJ-276 is a recent development in plastic scintillators that comes with improved pulse shape discrimination over its predecessor EJ-299-33. In this work, the neutron response functions, proton light output function, and detection efficiency of EJ-276 were measured using mono-energetic neutron reference fields at the national metrology laboratory, Physikalisch-Technische Bundesanstalt, in the neutron energy range 1.5–19 MeV. In particular, the proton light output in the range 14–19 MeV is presented for the first time. The optimization of Pulse Shape Discrimination has also been investigated using an 241Am-Be source and results are presented. Finally, we study how, using a shadow-cone method and time of flight method, we can discriminate scattered and other spurious neutrons from the mono-energetic beam. The characterized EJ-276 detector is to be used in the monitor of the neutron fields and gamma background at the new Neutron Irradiation Laboratory for Electronics facility at the Rutherford Appleton Laboratory.

High-accuracy parallelism measurement of coated cube by dual-autocollimators

A simple, cost-effective and high-accuracy measurement of parallelism by dual-autocollimators is proposed. A differential measurement was chosen to eliminate most of the environmental noises and systematic errors. The accuracy of parallelism measurement can reach the level of 1.6 μrad (1σ). This method can be widely used for parallelism measurements of components with reflective coating, such as glass blocks in metrology laboratories and test masses in the gravitational reference sensor.

In Situ Calibration of Wetlabs Chlorophyll Sensors: A Methodology Adapted to Profile Measurements

Measurement of chlorophyll a content in the ocean is essential for biomass assessment, finding the optical properties of seawater, and calibration of satellite remote sensing. The instruments used for this purpose are mostly fluorescence sensors. The calibration of these sensors becomes a crucial point to ensure the reliability and quality of the data produced. The technology of these sensors is based on the principle that a concentration of chlorophyll a in µg per liter can be calculated from an in situ fluorescence measurement. However, the study of the phenomenon of photosynthesis and cell physiology teaches us that the yield of fluorescence depends on many factors that are difficult or impossible to reconstitute in a metrology laboratory. This is the case, for example, of the algal species, its physiological state, the greater or lesser presence of dissolved organic matter in the water, the turbidity of the environment, or the surface illumination. What approach should be adopted in this context to achieve a better quality of the measurements? This is the objective of the work we present here, which is the result of nearly ten years of experimentation and testing to optimize the metrological quality of chlorophyll a profile measurement. The results we obtained allowed us to calibrate these instruments with an uncertainty of 0.2-0.3 on the correction factor, with correlation coefficients higher than 0.95 between the sensor values and the reference value.

Skinfold calipers: which instrument to use?

The considerable amount of original and generic types of skinfold calipers available is a source of systematic measurement error. This study is a brief report that critically examines the original and illustrated structural configuration of the three main types of skinfold calipers. For more than half a century, the Harpenden®, Lange® and Slim Guide® skinfolds calipers have been widely used in clinical and research settings. It is well established that the physical, mechanical and functional specificity of each type of skinfold caliper makes its interchangeable use impossible. Our report suggests that commercially available technical specifications are insufficient to judiciously choose a skinfold caliper. The area of the jaws, the coefficient of spring and the static and dynamic downward pressure of each type of skinfold caliper must be determined in the metrological laboratory and added to the technical user manual. Choosing a type of skinfold caliper for regular use, without conflict of commercial interest, requires a critical understanding of the physical, mechanical and functional characteristics that configure it. Therefore, a new downward static calibration test and the first eligibility flowchart for a skinfold caliper have been proposed. Finally, the information gathered in this report may be useful for manufacturers of anthropometric instruments and health professionals who use the skinfold technique as a tool for diagnosis and nutritional control.

Virtual Training Laboratory for Primary Impedance Metrology

This article presents the concept and some aspects of the physical implementation of a virtual training laboratory (VTL) in the field of primary impedance metrology. The creation of a VTL provides a novel method of disseminating metrological knowledge and expertise in a practical way and at a low cost. It will expose new users to the live experience of operating a digital impedance bridge thus helping to encourage the uptake of this novel and useful impedance measurement technology. The VTL was developed as part of the EMPIR projects VersICal 17RPT04, A versatile electrical impedance calibration laboratory based on digital impedance bridges, and GIQS 18SIB07, Graphene impedance quantum standard.

Uncertainty evaluation in activity measurements with HPGe using two relative methods

Radionuclide metrology laboratories aim to provide radioactive standards for detector calibrations in nuclear safety areas with low uncertainties. Such standards are applied in nuclear industries, according to the requirements of monitoring programmes. The standard radionuclides of 133Ba, 152Eu and 166mHo are suitable to the determination of efficiency curves in HPGe detectors due to their multi-gamma emissions, which are intense and well separate in the spectrum. With efficiency curves it is possible to do the measurements without needing to use standards. In this work was made a verifying of the uncertainties obtained for the two relative methods: comparative (sample-standard) and efficiency curve. The total uncertainties obtained by sample-standard method varied from 0.4 to 1.2 % (k=1). The results using efficiency curve method are between 0.9 to 2.2 % (k=1).

Software for measurement uncertainty assessment and actual metrological characteristics of viscometers

The issue of implementation of software for rapid assessment of uncertainty of metrological control results of measuring instruments used in the field of state metrological control and supervision in calibration and evaluation of actual metrological characteristics of operating viscosimeters was considered. An interpretation of the application of the EXCEL program and other software for the special methodology for automating uncertainty calculations developed by us was carried out, which significantly simplified the work and reduced the time spent by specialists in the metrological laboratory. Basic requirements of comparison of software for calculation, calculation and estimation of uncertainty in the realm of mathematical models of validated techniques are determined. The experimental results of the comparative analysis taking into account the set tasks are presented, the most common and effective universal software for calculating the uncertainty of the results of the experiment. The object of the study is universal software for estimating the uncertainty of measurements and other metrological characteristics of viscometers, structured by types of measurements, in the graphic programming environment. The software can be used both in laboratories and in industrial premises. The workplace can be both a metrological laboratory, the working area of which is a table with instruments, and a production room. As a rule, accredited laboratories do not have a special staff of metrologists or specialists who perfectly understand the basics of mathematical statistics and the concept of measurement uncertainty. The complexity and necessary amounts of calculations that are carried out in assessing the uncertainty of measurements require significant laboratory resources.

Practical X-ray beam spectrometry with cadmium telluride detector in 10–300 kVp range at Czech Metrology Institute. Part I. Instrumentation

The paper describes instrumentation used at Czech Metrology Institute for measurement of photon fluence spectra directly in X-ray beams. Detector with a cadmium telluride (CdTe) sensor was characterized by means of energy resolution and precise energy calibration. The hole trapping effect in CdTe causing full-energy peak deformations in measured spectra was adopted consisting of analytical models of incomplete charge collection and carrier trapping based on Hecht equation. The detector collimator provided by the manufacturer was modified with additional tungsten shielding that effectively absorbs the majority of photons scattered in the collimator body resulting in significant improvement of the consistency of measured and Monte Carlo simulated detector response. The purpose-made alignment platform increased the accuracy of orientation of the collimator axis improving the measurement in high photon fluence rate beams using collimation disks with very small apertures (down to 100 μm in diameter). The adopted instrumentation and methods for X-ray beam spectrometry enabled to fulfil the requirements of the new ISO 4037:2019-ed.2.0 standard for reference metrology laboratories. Software-focused part dealing with Monte Carlo simulations and procedures for photon fluence spectra unfolding is summarized in [1].

Investigation of Therapeutic Ultrasound Dose on Muscle Phantom: An Experimental Study Investigation of Therapeutic Ultrasound Dose

Objective: The study aims to investigate the standardized, traceable dose amounts that will create the desired therapeutic physiological change in the tissue and prevent the risk of tissue damage in the light of metrology principles 
 Methods: In the study carried out in TÜBİTAK National Metrology Institute Medical Metrology Laboratory, a muscle phantom simulating the acoustic properties of muscle tissue was created and thermocouples were placed in it. Ultrasound at different intensities and durations at 1 MHz frequency was applied to the phantom. The temperature changes measured by the thermocouples were recorded. Each measurement was repeated three times and averaged 
 Results: 14 minutes application at 1 W/cm2 density, 10 minutes application at 1.5 W/cm2 density, ~7 minutes application at 2 W/cm2 density, and ~4 minutes application at 2.5 W/cm2 density have been achieved for the temperature range needed to produce therapeutic effect. 
 Conclusions: In order to achieve the therapeutic effect, the ultrasound doses used in the procedure should be checked. Measurements in multi-layer phantoms would be useful in future research.

A new method of optimizing the thickness of metrological surface plate using simulation analysis

The challenges of choosing an optimally thick surface plate (SP) were noticed during the calibration of pressure measuring instruments against pressure balance type primary and secondary standards. This has motivated authors to investigate this issue in detail. It is observed that the traditional workstation made of steel sheets may not be flat enough to generate accurate pressure measurement results. These SPs are also regularly used in the metrology laboratories, inspection rooms, and manufacturing industries. Whenever precise and accurate measurements and inspections are performed, the irregularities of the working surfaces lead to incorrect results. Therefore, focused research is carried out by analyzing some of the standard granite plates. Usually, manufacturers design, fabricate, and install the SPs as per the recommendation of the respective documentary standards. The standards provide the requirements and specifications of the flatness tolerances for different sizes of the SPs. However, these standards do not precisely specify the optimum thickness of the SP. Standards also suggest using finite element analysis to avert complex mathematical procedures. The simulation method precisely represents the individual case of installation/design. Therefore, the bending cases due to self-weight and rigidity tests are simulated to determine the deformations of the various sizes of granite SPs. Their results led to devising the proposed optimization of the thickness of metrological surface plates. In the present investigation, granite SPs of different sizes are simulated. The critical thickness is observed when the deformation reduces to its optimum level. The surface deflection against the load is minimum at critical thickness values. The results obtained in the optimization are compared with the standard values.

Determination of Al2O3 Powder Thermal Conductivity Using DSC at NIS-Egypt

The mission of the thermal metrology laboratory is to maintain, disseminate, develop and realize the International Temperature Scale 1990 (ITS-90). One of the services that the laboratory has introduced is the routine calibration to all industrial sectors that covers almost all fields inside and outside Egypt. This paper explains how to use Differential Scanning Calorimeter (DSC) to determine the thermal conductivity of unknown powders. The paper is based on the ability to determine the thermal conductivity (k) of powders from the melting peak of the reference metal. This technique assists for the first time to establish a new activity at the National Institute for Standardization to test the thermal conductivity of powders, which had been requested by many clients. Experiments were carried out using alumina powder Al2O3 and metal reference beads of Sn and Zn which have diameter ranges from 1.9 mm up to 4.12 mm in an atmosphere of nitrogen during Sn and Zn melting. The results show good performance. The results showed confidence that will enable to do more studies at NIS to see if this technology can be applied to a wider spectrum of materials.

Stable Optical Frequency Comb Distribution Enabled by Hollow‐Core Fibers

AbstractOver the last two decades, optical frequency combs (OFCs) have enabled some of the most accurate measurements in physics. Distributing light from OFCs via optical fibers could make these high‐accuracy measurement tools available more widely, from a few dedicated metrology laboratories to other laboratories and industry. However, the performance of distributed OFCs is strongly limited by impairments of standard single mode fiber (SMF), most notably its thermal sensitivity of chromatic dispersion, for which no compensation technique has been shown to date. To overcome this limitation, use of a new class of optical fiber is suggested here: a hollow core fiber (HCF), which offers more than an order of magnitude lesser such impairment. The measured OFC frequency stability of the optical mode and mode spacing reaches 1.8 × 10−19 and 1.5 × 10−17 at a few thousand seconds, respectively, after transmitting through 7.7 km of HCF. To the best of knowledge, this is the best ever performance for km‐lengths of fiber‐based OFC distribution. Besides, other HCF advantages over SMF in this application are discussed. Specifically, HCFs offer over an order of magnitude lower thermal sensitivity of propagation delay, several orders of magnitude lower optical nonlinearity, and almost ten times lower chromatic dispersion.

Workplace monitoring in the Radiation Physics and Metrology Laboratory (LAF-RAM)

The values of environmental equivalent dose H*(10) using thermoluminescent dosimeters (TLD) in the Radiation Physics and Metrology Laboratory (LAF-RAM) from 2019 to 2021 are presented. Fifteen measuring points are monitored on a total of 23 monitoring periods. The selected locations include the public areas, the supervised areas. The characterization of the environmental dosimetry of LAF-RAM was possible finding no significative variations in the temporal evolution of the evaluated periods and the results do not indicate any risk to occupational workers or members of public.