Metrology, Volume 5, Issue 1 (March 2025) – 18 articles

Medical laboratories are perhaps the largest measurement industry in the world. The metrology terminology is relevant for effective and efficient communication, particularly where metrology activities are carried out by operators with different metrology skills. The World Association of Societies of Pathology and Laboratory Medicine (WASPaLM) and SIPMeL have had some opportunities to propose changes to the documents in preparation for the Clinical and Laboratory Standards Institute (CLSI) and the ISO/TC 212 in order to harmonize the terminology with the Metrology Vocabulary (VIM) of the Joint Committee for Guides in Metrology (JCGM). Many proposals have been accepted. Here, we summarize some particularly critical points for metrological terms. The main terms discussed are the following: measuring, measuring range, examination, pre-examination, post-examination, manufacturer, measuring instrument, quantitative, qualitative, semi-quantitative, processing, measurement error, maximum permissible error of measurement, total error of measurement, monitoring, variability, performance, reliability, influence, interference, selectivity, sensitivity, detection limit, reliability, comparability, compatibility, control material. Despite all the efforts to coordinate terminologies, it is inevitable that overlapping and inconsistent terminologies will continue to be used because documents and policies are produced in different contexts. In some ISO/TC 212 and CLSI documents, the phenomenon of magnetic attraction toward common words (such as “analysis” and derivatives), without any consideration of the true metrological meaning, is noted. The ISO/TC 212 and CLSI working groups show, alongside moments of openness, phenomena of true self-referential conservatism. Full article

The testing of rolling stock for the assessment of disturbance in signalling circuits is considered with a focus on the measurement process and the selection of operating conditions. The definition of interference limits is briefly reviewed, but they are considered an external input. The spectral behavior of acquired signals and the evaluation of repeatability are instead discussed with the help of three different real test cases, considering correspondence between similar operating points and differences as rolling stock operation evolves during a test run. Repeatability evaluated as standard deviation is in the order of 3% to 5% in the harmonic and audio frequency range for the different systems, slightly lower for AC railways; above about 10–15 kHz it increases to 30%. Uncorrelated components (with much lower amplitudes) may show much higher dispersion. Full article

Assessing the binder performance of thermal characterization is critical for quality control. This is pertinent for recovered binders from mixtures, which may not be in adequate quantities to evaluate their performance, particularly in mixtures containing reclaimed asphalt pavement (RAP). The present study deployed a thermogravimetric analyzer to evaluate compositional changes in recovered binders from RAP-containing mixtures, focusing on thermograph and derivative of thermograph (DTG) characteristics and correlating the results to rheological features. Incorporating RAP in mixtures influenced recovered binders’ DTG shapes, reducing low-combusted components (%LCC) and increasing residues (%R). The recovered binder from the zero-RAP-containing mixture showed a 4.36% increase in %LCC and a 1.97% decrease in %R compared to the short-term aged original binder. Binders recovered from RAP-containing mixtures exhibited greater stiffness than the short-term aged original binders. The %LCC dropped from 7.22% to 25.52%, while the %R increased from 20.69% to 33.06%. Uncertainty analyses showed that the DTG area and %R had the least uncertainty and that the %LCC had greater uncertainty. Analysis through regression revealed that DTG area and %R can predict G*/sinδ well, showing a correlation between better thermal stability and binder stiffness. This research puts a number on the correlation between thermal and rheological properties, which helps to improve quality control for binders. Full article

We present the design, construction, measurement, and troubleshooting of a prototype hybrid Halbach quadrupole magnet. This magnet was significantly under-strength due to local demagnetization in the permanent magnet material. We discuss how this effect was uncovered, how it was verified by performing Hall probe measurements of the individual magnet blocks, and how the effect was reconstructed in simulations. Full article

This paper introduces a method for calibrating radar sensors in a multi-sensor cinemometer system using a reference cinemometer based on CW Doppler radar. The method involves synchronizing sensors, pairing data with reference measurements, and performing polynomial corrections. Tests conducted on various traffic sites demonstrate the accuracy and reliability of the calibration process. Results show low uncertainties compared to regulatory standards. Validation against a calibrated lidar system confirms accuracy. This method ensures precise speed measurements, surpassing regulatory requirements, and demonstrating practical applicability in real-world scenarios. Full article

The capability of low-cost photogrammetric systems to provide live six degrees of freedom (6DoF) tracking of multiple objects offers great value in providing high-quality and consistent part production by automated manufacturing systems. However, monitoring of high-speed components, such as cutting heads, presents several unique challenges that existing systems struggle to meet. The solution given here uses a small number of short-exposure imaging sensors coupled with high-intensity lighting and retrorefective markers to allow for high-speed capture. The use of an initial characterization process carried out using IDEKO’s VSET© system is followed by live object tracking in bespoke image processing software running on a consumer-grade computer. Once this system is in use, it can simultaneously capture images of multiple markers in less than 0.1 milliseconds and use these to determine the 6DoF of the objects that the markers define. 6DoF recalculation of all objects within each measurement instance makes the system resilient to large movements, object occlusion, and sensor relocation. Feasibility tests of a four-camera system as a machine characterization tool tracking a cutting tool spinning at up to 3000 rpm across a volume of 1 m³ achieved a mean reference marker agreement between tool poses of 2.5 µm with markers moving at up to 17.5 ms⁻¹. Given good photogrammetric geometry, 6DoF parameters of the spinning tool were determined to standard deviations of 37.7 µm and 0.086°. Full article

The development and study of Smart Grid technologies rely heavily on high-fidelity data from Phasor Measurement Units (PMUs). However, the scarcity of real-world PMU data due to privacy, security, and variability issues poses significant challenges to researchers, developers, and related industries. To address these challenges, this article introduces the bases for a digital metrology framework, focusing on a newly designed and developed synthetic PMU data generator, that is both metrologically accurate and easy to adapt to various grid configurations for data generation from point-on-wave (PoW) data. This initial phase for a Smart Grid research framework aligns with Open Science principles, ensuring that the generated data are Findable, Accessible, Interoperable, and Reusable (FAIR). By embracing these principles, the generated synthetic data not only facilitate collaboration for Smart Grid research but also ensure their easy integration into existing Smart Grid simulation environments. Additionally, the proposed digital metrology framework for Smart Grid research will provide a robust platform for simulating real-world scenarios, such as grid stability, fault detection, and optimization. Through this open science approach, future digital metrology frameworks can support the acceleration of research and development, overcoming current limitations, e.g., lack of significant amounts of real-world scenarios by PMU data. This article also presents an initial case study for situational awareness and control systems, demonstrating the potential for future Smart Grid research framework and its direct real-world impact. All research outcomes are provided to highlight future opportunities for reusability and collaborations by a novel approach for research on sensor network metrology. Full article

Ultrasonic flow meters (UFMs) by transit time are ubiquitous in industrial applications, mainly for their versatility and practicality. They are widely used in gas and liquid installations, such as the oil and gas industry or feedwater systems in nuclear power plants. Computational fluid dynamics (CFD) techniques can be used as a tool to potentially improve the ultrasonic flow measurements. CFD may contribute to predicting the velocity profile and the profile factor in disturbed flows, integrating fluid flow and acoustic ray, improving the calibration of UFMs, or assisting in design optimization. This communication presents the working principle of the UFM, discusses how CFD can be used as a tool to support improvements, and shows relevant trending fields that deserve further investigation to promote significance on this subject. Full article

Advances in silicon carbide fabrication techniques enable the fabrication of high aspect ratio non-line-of-sight structures. The further development of non-line-of-sight fabrication tools and the use of the non-line-of-sight structures requires a set of measurement techniques. The goals of the measurement techniques are to (1) quickly detect the success of the fabrication and determine when a failure occurs, (2) accurately measure the shape of the subsurface structure, and (3) accurately characterize the structure. The first goal is attained using subsurface optical microscopy and single point confocal microscopy with a demonstrated resolution of 3 μm. The second goal is attained using X-ray computer tomography with a resolution of 500 nm. The third goal requires the accuracy of scanning electron microscopy. The substructures are brought to the surface through focused ion beam milling if the structures are less than 30 μm deep and through ablation cleaving and polishing for deeper substructures. Full article

Waveform generation as part of on-chip built-in self-test (BIST) circuitry often necessitates sufficient linearity without expensive hardware overhead. Achieving high linearity is critical for accurate signal generation, especially in applications requiring high precision, such as biomedical and instrumentation applications. Currently, achieving the high linearity and precision required in signal generators often relies on costly hardware such as automated test equipment (ATE). This paper presents a DAC-based arbitrary waveform generator (AWG). We use a low-cost DAC and a fully digital on-chip testing and calibration approach to nullify the effect of the DAC’s non-linearity on the generated waveform. The ultra-low cost and high linearity benefit of the proposed waveform generator makes it highly suitable for integration into resource-constrained systems. The proposed approach is validated using simulation results of the small-area DAC designed in TSMC 0.18 μm technology and the testing and calibration algorithms implemented in MATLAB. The DAC, designed with a matching accuracy at only the 5-bit level, is able to generate a signal with an ENOB of 12 bits alongside an SFDR and THD surpassing 100 dB. This high level of signal purity is consistently maintained across 100 Monte Carlo simulations, demonstrating the robustness of the architecture against PVT variations as well as random mismatches. Full article

Environmental monitoring and remediation of hydrocarbon contamination in soil, particularly through passive methods, has become a critical area of focus for oil companies adapting to current environmental standards. Natural source zone depletion (NSZD) is a passive remediation process in which the degradation of petroleum hydrocarbons by microorganisms produces measurable thermal effects on the subsurface. Accurate estimation of the NSZD rate is heavily dependent on the precision of temperature measurements, as small uncertainties in temperature can cause significant variations in the estimated rates. Despite growing interest in using subsurface temperature data for NSZD monitoring, there is a lack of studies addressing the impact of temperature measurement uncertainty on the reliability of depletion rate estimates. This paper proposes a Monte Carlo method approach to assess the propagation of temperature measurement uncertainties through the NSZD rate estimation process. By simulating different uncertainty scenarios, this work defines acceptable limits for temperature measurement errors to ensure accurate and representative NSZD rate calculations. For the analyzed case study, it was determined that the relationship between uncertainties was nearly linear, with a slope of 52.5 L m⁻² year⁻¹ in the estimated NSZD rate for each degree Celsius of uncertainty in the temperature measurements. Full article

There is growing concern regarding the environmental and operational safety aspects of fuel. The result of a physicochemical measurement is the outcome of a series of steps that begin with the sampling process. The information obtained from this step and the contribution from the analytical process define the measurement uncertainty, although most laboratories consider only the analytical contribution as a quality parameter. On the other hand, this variability can be used as vital information to evaluate conformity to a specification. This study aimed to use uncertainty information considering only the analytical uncertainty and, next, the analytical and sampling uncertainties in compliance assessment, taking physicochemical measurements of fuel as case studies. The first scenario, which is traditional and focused solely on analytical uncertainty, showed to be less rigorous than the second scenario, which combined sampling uncertainty with analytical uncertainty. The results indicated that for the flash point in jet fuel, the sulfur mass fraction in gasoline-ethanol blends, and the kinematic viscosity in diesel, the risks to consumers—first considering only analytical uncertainty and then combining analytical uncertainty with sampling uncertainty—were the following: 2.6% and 5.6%; 4.4% and 7.1%; and 1.6% and 18.9%, respectively. Since the initial result of each pair was below 5%, compliance with the specification is suggested. However, when accounting for sampling uncertainty, there is an indication of potential non-compliance with the specification. Therefore, it is concluded that the contribution of uncertainty arising from sampling must be considered in a conformity assessment. Full article

This paper proposes a metrologically interpretable soft sensing method for estimating the liquid flow rates in hydraulic systems from non-invasive vibration frequency power band data. Despite considerable interest in non-invasive flow estimation, state-of-the-art methods provide little to no metrological capabilities. In this work, a dedicated test rig was developed to automatically acquire vibration and flow rate data from a centrifugal pump, in a flow rate range between 0.05 × 10⁻⁵${\mathrm{m}}^3$/$\mathrm{s}$ and 9.11 × 10⁻⁵${\mathrm{m}}^3$/$\mathrm{s}$. The vibration data were processed into power bands, which were subsequently used to optimize and train a multilayer perceptron neural network for flow soft sensing. The trained model was compared with models with different vibration processing methods from literature. The power band processing model resulted in a root mean squared error 75.4% smaller than the second-best model in cross-validation, and 51.5% smaller with test data. The uncertainty of the proposed regression model was estimated using a combination of ensemble learning and Monte Carlo simulations, and combined with the reference flow sensor uncertainty to obtain the total combined uncertainty of the soft sensor, found to be between 3.9 × 10⁻⁶${\mathrm{m}}^3$/$\mathrm{s}$ and 6.1 × 10⁻⁶${\mathrm{m}}^3$/$\mathrm{s}$ throughout the measured flow range. The reference flow sensor accuracy was found to be the largest individual contribution for the final uncertainty, closely followed by the regression model uncertainty. Full article

This study focuses on a detailed analysis of the cutting forces in rotational turning, a novel machining process designed to achieve high surface quality and productivity. Unlike traditional longitudinal turning, rotational turning employs a helical cutting-edged tool that performs a circular feeding movement, introducing complex kinematics that complicates the accurate measurement of the cutting forces. To address this, the theoretical background was described for modeling the cutting force removal. The process was experimentally simulated on a CNC milling machine using a custom-designed measurement system. The major cutting force, passive force, and feed force were successfully measured and analyzed under varying feed conditions for both rotational and longitudinal turning. The results demonstrate a significant reduction in the passive force during rotational turning compared to longitudinal turning, which directly contributes to lower elastic deformation in the radial direction of the workpiece. This reduction improves the dimensional accuracy and stability during machining. Additionally, the feed force was observed to be slightly higher in rotational turning, reflecting the influence of the rotational movement of the tool. These findings highlight the advantages of rotational turning for applications requiring precision and surface quality, particularly where radial deformation is a critical concern. This study establishes a reliable methodology for force measurement in rotational turning and provides valuable comparative insights into its performance relative to conventional turning processes. Full article

The microfluidic industry faces a significant challenge due to the lack of sensitive and standardized methods. One critical need is the measurement of internal channel dimensions in fully assembled chips. This study presents and compares several protocols for measuring these dimensions, including optical profilometry, optical microscopy, and tiled digital imagery. Standardized chips made from two materials commonly used in microfluidics (borosilicate glass and Cyclic Olefin Copolymer) were evaluated using each protocol. A consistency analysis using normalized error statistics identified optical profilometry as the most reliable method, offering the lowest uncertainty and the highest consistency with nominal geometry values. However, all protocols encountered difficulties with vertical depth measurements of internal structures. Future research should focus on addressing these limitations, including investigating the influence of multiple refractive surfaces on optical profilometry and exploring confocal microscopy. In conclusion, this work provides a comprehensive comparison of measurement protocols for internal microfluidic structures and offers a practical solution for applications in the microfluidic industry, while also identifying important directions for future research. Full article

Sensor networks, which are increasingly being used in a broad range of applications, constitute a measurement paradigm involving ensembles of sensors measuring possibly different quantities at a discrete sample of spatial locations and temporal points outside the laboratory. If sensor networks are to be considered as true metrology systems and the measurement results derived from them used for decision-making, such as in a regulatory context, it is important that the results are accompanied by reliable statements of measurement uncertainty. This paper gives a preview of some of the work undertaken within the European-funded ‘Fundamental principles of sensor network metrology (FunSNM)’ project to address the challenges of measurement uncertainty evaluation in some real-world sensor network applications. The applications demonstrate that sensor networks possess features related to the nature of the measured quantities, to the nature of the measurement model, and to the nature of the measured data. These features make conventional methods of measurement uncertainty evaluation, and established guidelines for measurement uncertainty evaluation difficult to apply. An overview of some of the modelling tools used to address the challenges of measurement uncertainty evaluation in those applications is given. Full article

There is a growing field that is devoted to developing inexpensive microscopes and measurement devices by leveraging low-cost commercial parts that can be controlled using smartphones or embedded devices, such as Arduino and Raspbery Pi. Examples include the use of Blu-ray optical heads like the PHR-803T to perform cytometry, spinning disc microscopy, and lensless holographic microscopy. The modular or disposable nature of these devices means that they can also be used in contaminating and degrading environments, including radioactive environments, where replacement of device elements can be expensive. This paper presents the development and operation of a confocal microscope that uses the PHR-803T optical device in a Blu-ray reader for both imaging and detection of temperature variations with between 1.5 and 15 µm resolution. The benefits of using a PHR-803T confocal system include its relatively inexpensive design and the accessibility of the components that are used in its construction. The design of this scanning confocal thermal microscope (SCoT) was optimized based on cost, modularity, portability, spatial resolution, and ease of manufacturability using common tools (e.g., drill press, 3D printer). This paper demonstrated the ability to resolve microscale features such as synthetic spider silk and measure thermal waves in stainless steel using a system requiring <USD 1000 in material costs. Full article

This article examines how water content is a crucial parameter for the preservation of wooden artworks and buildings, focusing on non-invasive ways of measuring water content through capacitive methods. A personalized, low-cost probe to measure the dielectric properties of oak and poplar wood at various water content levels and frequencies is described. The accuracy of the probe is confirmed by testing it with reference materials like air, PTFE, PLA, glass and Bakelite, demonstrating an accuracy error below 2%. Next, the probe is used to evaluate the relationship between water content and permittivity, indicating possible uses in conservation projects. Measurements were conducted on two types of wood, poplar and oak, at five varying levels of water content. The dielectric permittivity between 10 and 100 kHz was assessed. Using the vertical shift from the single interpolant of the dataset, a graduation curve was estimated. Finally, an R² = 0.98 value demonstrates that a sigmoidal function reflects the relationship between the percentage water content and the permittivity of materials. Full article