Instruments

8 pages, 983 KB

Open AccessArticle

Determination of Super Luminescent Diode Junction Temperature via Static Modulated Fourier-Transform Spectrometer

by Ju Yong Cho and Won Kweon Jang

Instruments 2026, 10(1), 12; https://doi.org/10.3390/instruments10010012 - 8 Feb 2026

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The accurate and rapid measurement of junction temperature is critical for optimizing the performance and ensuring the longevity of a super luminescent diode. However, due to diverse diode structures, directly measuring and monitoring the junction temperature of a super luminescent diode are often [...] Read more.

The accurate and rapid measurement of junction temperature is critical for optimizing the performance and ensuring the longevity of a super luminescent diode. However, due to diverse diode structures, directly measuring and monitoring the junction temperature of a super luminescent diode are often challenging and impractical. We propose a non-invasive methodology to precisely determine the junction temperature and spectral characteristics of a super luminescent diode. This method utilizes a modified static modulated Fourier-transform spectrometer alongside a generalized analyzing expression derived from Gaussian components. Fast acquisition of spectral information is achieved through the modified static modulated Fourier-transform spectrometer and analyzing method. The proposed model has exceptional accuracy, yielding an average coefficient of determination R² of 0.99 across a range of operating currents and junction temperatures. Our analysis reveals a distinct linear correlation between the extracted fitting parameters—specifically the carrier temperature, the spectral shape parameter and the physical junction temperature. These findings demonstrate that the critical internal physical conditions of the diode can be accurately inferred directly from its measured spectrum, providing a robust tool for device characterization. Full article

(This article belongs to the Section Optical and Photonic Instruments)

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18 pages, 2559 KB

Open AccessArticle

Calibration of a Capacitive Coupled Ring Resonator for Non-Invasive Measurement of Wood Moisture Content

by Livio D’Alvia, Ludovica Apa, Emanuele Rizzuto, Erika Pittella and Zaccaria Del Prete

Instruments 2026, 10(1), 11; https://doi.org/10.3390/instruments10010011 - 5 Feb 2026

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Abstract

The accurate and non-invasive measurement of moisture content in wood is essential for the preservation of historical and artistic artifacts. This study presents the calibration of a planar Microwave Planar Capacitive Coupled Ring Resonator (MPCCRR) designed to indirectly and non-destructively assess the water [...] Read more.

The accurate and non-invasive measurement of moisture content in wood is essential for the preservation of historical and artistic artifacts. This study presents the calibration of a planar Microwave Planar Capacitive Coupled Ring Resonator (MPCCRR) designed to indirectly and non-destructively assess the water content in wood samples. The method relies on analyzing shifts in the resonant frequencies and variations in the transmission parameter |S21| resulting from changes in the material’s dielectric permittivity. After preliminary characterization via parametric simulations (εr = 1–10) and validation with low-permittivity reference materials, the sensor was tested on three wood species (poplar, fir, beech), including measurements at two sensor positions and with different grain orientations. The results demonstrate a monotonic, repeatable response to increasing moisture content with frequency shifts up to ≈220 MHz and normalized sensitivities ranging from 3 to 9 MHz/% water content, depending on species and measurement position. Position 2 showed the greatest sensitivity due to stronger field–sample interaction, while Position 1 provided a quasi-isotropic response with excellent repeatability. Linear regression analyses revealed good correlations between the frequency shifts and the gravimetric water content (R² ≥ 0.85). The MPCCRR sensor therefore proves to be a promising tool for the non-invasive monitoring of wood moisture, which is particularly suitable for the low-moisture range encountered in cultural heritage conservation, with an estimated moisture uncertainty of 0.12–0.35% under controlled laboratory conditions. Full article

(This article belongs to the Section Sensing Technologies and Precision Measurement)

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9 pages, 20032 KB

Open AccessArticle

Wide-Aperture Diffraction-Based Beam-Shaping Structures for Enhanced Directivity in Next-Generation High-Frequency Communication Systems

by Vladislovas Čižas, Simonas Driukas, Andrius Masaitis, Kotryna Nacienė, Kasparas Stanaitis, Egidijus Šideika and Linas Minkevičius

Instruments 2026, 10(1), 10; https://doi.org/10.3390/instruments10010010 - 4 Feb 2026

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Abstract

Sub-terahertz (sub-THz) frequencies are in the spotlight in the ongoing development of sixth-generation (6G) wireless communication systems, offering ultra-high data rates and low latency for rapidly emerging applications. However, employment of sub-THz frequencies introduces strict propagation challenges, including free-space path loss and atmospheric [...] Read more.

Sub-terahertz (sub-THz) frequencies are in the spotlight in the ongoing development of sixth-generation (6G) wireless communication systems, offering ultra-high data rates and low latency for rapidly emerging applications. However, employment of sub-THz frequencies introduces strict propagation challenges, including free-space path loss and atmospheric absorption, which limit coverage and reliability. To address these issues, highly directional links are required. The conventional beam-shaping solutions such as refractive lenses and parabolic mirrors are bulky, heavy, and costly, making them less attractive for compact systems. Diffractive optical elements (DOEs) offer a promising alternative by enabling precise wavefront control through phase modulation, resulting in thin, lightweight components with high focusing efficiency. Employing the fused deposition modelling (FDM) using high-impact polystyrene (HIPS) allows cost-effective fabrication of DOEs with minimal material waste and high diffraction efficiency. This work investigates the beam-shaping performance of the FDM-printed structures comparing DOEs and spherical refraction-based structures, wherein both are aiming for application in sub-THz communication systems. DOEs exhibit clear advantages over classically employed solutions. Full article

(This article belongs to the Section Optical and Photonic Instruments)

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16 pages, 533 KB

Open AccessReview

The Intelligent Knife (iKnife): Revolutionizing Intraoperative Tissue Diagnosis Through Rapid Evaporative Ionization Mass Spectrometry (REIMS)

by Gabriel Amorim Moreira Alves, Mohan Dodeja, Fazal Khan, Mary Szocik and Arosh Shavinda Perera Molligoda Arachchige

Instruments 2026, 10(1), 9; https://doi.org/10.3390/instruments10010009 - 3 Feb 2026

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Abstract

The intelligent surgical knife (iKnife), based on rapid evaporative ionization mass spectrometry (REIMS), represents a transformative advance in intraoperative tissue characterization. By integrating mass spectrometry with electrosurgical dissection, the iKnife enables real-time differentiation between cancerous and healthy tissues through molecular fingerprinting of the [...] Read more.

The intelligent surgical knife (iKnife), based on rapid evaporative ionization mass spectrometry (REIMS), represents a transformative advance in intraoperative tissue characterization. By integrating mass spectrometry with electrosurgical dissection, the iKnife enables real-time differentiation between cancerous and healthy tissues through molecular fingerprinting of the aerosol generated during cutting. This innovation significantly shortens operative time by eliminating delays associated with conventional histopathological analysis and enhances surgical precision by providing continuous feedback on tissue composition. Since its inception by Zoltán Takáts and colleagues, the iKnife has demonstrated remarkable diagnostic accuracy across multiple cancer types, including breast, ovarian, and colorectal malignancies, with reported sensitivities and specificities > 90% in selected tumour types. Beyond oncology, REIMS technology also shows promise for microbial identification and metabolomic profiling. This review provides a comprehensive overview of the iKnife’s development, underlying principles, clinical validation, and emerging applications, as well as its integration into surgical workflows and the challenges remaining for widespread clinical adoption. Future perspectives include miniaturization, AI-driven spectral interpretation, and expansion into robotic and image-guided surgery. Full article

(This article belongs to the Section Analytical Science and Biomedical Instruments)

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46 pages, 4088 KB

Open AccessSystematic Review

A Systematic Review of Deep Reinforcement Learning for Legged Robot Locomotion

by Bingxiao Sun, Sallehuddin Mohamed Haris and Rizauddin Ramli

Instruments 2026, 10(1), 8; https://doi.org/10.3390/instruments10010008 - 30 Jan 2026

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Abstract

Legged robot locomotion remains a critical challenge in robotics, demanding control strategies that are not only dynamically stable and robust but also capable of adapting to complex and changing environments. deep reinforcement learning (DRL) has recently emerged as a powerful approach to automatically [...] Read more.

Legged robot locomotion remains a critical challenge in robotics, demanding control strategies that are not only dynamically stable and robust but also capable of adapting to complex and changing environments. deep reinforcement learning (DRL) has recently emerged as a powerful approach to automatically generate motion control policies by learning from interactions with simulated or real environments. This study provides a systematic overview of DRL applications in legged robot control, emphasizing experimental platforms, measurement techniques, and benchmarking practices. Following PRISMA guidelines, 27 peer-reviewed studies published between 2018 and 2025 were analyzed, covering model-free, model-based, hierarchical, and hybrid DRL frameworks. Our findings reveal that reward shaping, policy representation, and training stability significantly influence control performance, while domain randomization and dynamic adaptation methods are essential for bridging the simulation-to-real-world gap. In addition, this review highlights instrumentation approaches for evaluating algorithm effectiveness, offering insights into sample efficiency, energy management, and safe deployment. The results aim to guide the development of reproducible and experimentally validated DRL-based control systems for legged robots. Full article

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16 pages, 2752 KB

Open AccessArticle

Evaluation of Gap and Flush Inspection Algorithms in a Portable Laser Line Triangulation System Through Measurement System Analysis (MSA)

by Guerino Gianfranco Paolini, Sara Casaccia, Matteo Nisi, Cristina Cristalli and Nicola Paone

Instruments 2026, 10(1), 7; https://doi.org/10.3390/instruments10010007 - 26 Jan 2026

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Abstract

The shift toward Industry 5.0 places human-centred and digitally integrated metrology at the core of modern manufacturing, particularly in the automotive sector, where portable Laser Line Triangulation (LLT) systems must combine accuracy with operator usability. This study addresses the challenge of operator-induced variability [...] Read more.

The shift toward Industry 5.0 places human-centred and digitally integrated metrology at the core of modern manufacturing, particularly in the automotive sector, where portable Laser Line Triangulation (LLT) systems must combine accuracy with operator usability. This study addresses the challenge of operator-induced variability by evaluating how algorithmic strategies and mechanical support features jointly influence the performance of a portable LLT device derived from the G3F sensor. A comprehensive Measurement System Analysis was performed to compare three feature extraction algorithms—GC, FIR, and Steger—and to assess the effect of a masking device designed to improve mechanical alignment during manual measurements. The results highlight distinct algorithm-dependent behaviours in terms of repeatability, reproducibility, and computational efficiency. More sophisticated algorithms demonstrate improved sensitivity and feature localisation under controlled conditions, whereas simpler gradient-based strategies provide more stable performance and shorter processing times when measurement conditions deviate from the ideal. These differences indicate a trade-off between algorithmic complexity and operational robustness that is particularly relevant for portable, operator-assisted metrology. The presence of mechanical alignment aids was found to contribute to improved measurement consistency across all algorithms. Overall, the findings highlight the need for an integrated co-design of algorithms, calibration procedures, and ergonomic aids to enhance repeatability and support operator-friendly LLT systems aligned with Industry 5.0 principles. Full article

(This article belongs to the Special Issue Instrumentation and Measurement Methods for Industry 4.0 and IoT)

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22 pages, 4689 KB

Open AccessArticle

A Procedure for Performing Reproducibility Assessment of the Accuracy of Impact Area Classification for Structural Health Monitoring in Aerospace Structures

by Luciano Chiominto, Giulio D’Emilia, Antonella Gaspari, Emanuela Natale, Francesco Nicassio and Gennaro Scarselli

Instruments 2026, 10(1), 6; https://doi.org/10.3390/instruments10010006 - 26 Jan 2026

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Abstract

The principal objective of this work is to develop an optimized procedure that guarantees the reproducibility of results across different applications and laboratories, facilitating potential field applications of methodologies for Structural Health Monitoring in aerospace structures. The focus is to accurately detect and [...] Read more.

The principal objective of this work is to develop an optimized procedure that guarantees the reproducibility of results across different applications and laboratories, facilitating potential field applications of methodologies for Structural Health Monitoring in aerospace structures. The focus is to accurately detect and localize impact areas on planar structures using in situ transducers and Machine Learning (ML) techniques. The research concentrates on an aluminum plate where impacts are generated by metal spheres of different masses dropped from a fixed height. The resulting Lamb waves are detected by PZT sensors glued on the surface. Various data processing and feature extraction algorithms are implemented and compared to extract the differences in Time of Flight (ΔToF). The obtained features are used for training ML classification models. Then, the influence of various parameters in signal acquisition and data processing are assessed along with the reproducibility of the results. For this reason, an interlaboratory comparison is conducted in which the trained models are applied to data collected under varying conditions. The experimental results show that the most influencing factors for impact area classification are the algorithm for ΔToF estimation, the number of training points used in ML models, the type of classification model, the distribution of the impact points on the component, and their balance in the classification area. This evidence suggests approaches for reducing both issues, therefore improving the reproducibility of results. Full article

(This article belongs to the Special Issue Instrumentation and Measurement Methods for Industry 4.0 and IoT)

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22 pages, 4873 KB

Open AccessArticle

Button Sample Holders for Infrared Spectroscopy

by Robert L. White

Instruments 2026, 10(1), 5; https://doi.org/10.3390/instruments10010005 - 26 Jan 2026

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Abstract

The design features and applications of button sample holders are described. The similarities and contrasts between the button method and the transmission cell and attenuated total reflection techniques are discussed. Different button sample holder analysis methodologies are outlined, and examples are provided for [...] Read more.

The design features and applications of button sample holders are described. The similarities and contrasts between the button method and the transmission cell and attenuated total reflection techniques are discussed. Different button sample holder analysis methodologies are outlined, and examples are provided for mid-infrared spectroscopy measurements of solids, liquids, and pastes. Results obtained for 10-nonadecanone powder, a vitamin C tablet, a soil sample, and poly(methyl methacrylate) are used to illustrate different solid sample analysis approaches. Time-dependent spectrum variations detected during evaporation of a blood drop are elucidated and spectra obtained from different quantities of liquid chlorobenzene loaded into buttons and transmission cells are characterized. Infrared spectra derived from three toothpaste brands are compared and a sample perturbation study to identify temperature-dependent changes to the structure of poly(bisphenol A carbonate) is provided as an example of variable temperature infrared spectroscopy. Full article

(This article belongs to the Section Optical and Photonic Instruments)

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16 pages, 2826 KB

Open AccessArticle

Characterization of the Extraction System of Supersonic Gas Curtain-Based Ionization Profile Monitor for FLASH Proton Therapy

by Farhana Thesni Mada Parambil, Milaan Patel, Narender Kumar, Bharat Singh Rawat, William Butcher, Tony Price and Carsten P. Welsch

Instruments 2026, 10(1), 4; https://doi.org/10.3390/instruments10010004 - 25 Jan 2026

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Abstract

FLASH radiotherapy requires real-time, non-invasive beam monitoring systems capable of operating under ultra-high dose rate (UHDR) conditions without perturbing the therapeutic beam. In this work, we characterized the extraction system of Supersonic Gas Curtain-based Ionization Profile Monitor (SGC-IPM) for its capabilities as a [...] Read more.

FLASH radiotherapy requires real-time, non-invasive beam monitoring systems capable of operating under ultra-high dose rate (UHDR) conditions without perturbing the therapeutic beam. In this work, we characterized the extraction system of Supersonic Gas Curtain-based Ionization Profile Monitor (SGC-IPM) for its capabilities as a transverse beam profile and position monitor for FLASH protons. The monitor utilizes a tilted gas curtain intersected by the incident beam, leading to the generation of ions that are extracted through a tailored electrostatic field, and detected using a two stage microchannel plate (MCP) coupled to a phosphor screen and CMOS camera. CST Studio Suite was employed to conduct electrostatic and particle tracking simulations evaluating the ability of the extraction system to measure both beam profile and position. The ion interface, at the interaction region of proton beam and gas curtain, was modeled with realistic proton beam parameters and uniform gas curtain density distributions. The ion trajectory was tracked to evaluate the performance across multiple beam sizes. The simulations suggest that the extraction system can reconstruct transverse beam profiles for different proton beam sizes. Simulations also supported the system’s capability as a beam position monitor within the boundary defined by the beam size, the dimensions of the extraction system, and the height of the gas curtain. Some simulation results were benchmarked against experimental data of 28 MeV proton beam with 70 nA average beam current. This study will further help to optimize the design of the extraction system to facilitate the integration of SGC-IPM in medical accelerators. Full article

(This article belongs to the Special Issue Plasma Accelerator Technologies)

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19 pages, 6653 KB

Open AccessArticle

Scalable Relay Switching Platform for Automated Multi-Point Resistance Measurements

by Edoardo Boretti, Kostiantyn Torokhtii, Enrico Silva and Andrea Alimenti

Instruments 2026, 10(1), 3; https://doi.org/10.3390/instruments10010003 - 31 Dec 2025

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Abstract

In both research and industrial settings, it is often necessary to expand the input/output channels of measurement instruments using relay-based multiplexer boards. In research activities in particular, the need for a highly flexible and easily configurable solution frequently leads to the development of [...] Read more.

In both research and industrial settings, it is often necessary to expand the input/output channels of measurement instruments using relay-based multiplexer boards. In research activities in particular, the need for a highly flexible and easily configurable solution frequently leads to the development of customized systems. To address this challenge, we developed a system optimized for automated direct current (DC) measurements. The result is based on a

4 \times 4

switching platform that simplifies measurement procedures that require instrument routing. The platform is based on a custom-designed circuit board controlled by a microcontroller. We selected bistable relays to guarantee contact stability after switching. We finally developed a system architecture that allows for straightforward expansion and scalability by connecting multiple platforms. We share both the hardware design source files and the firmware source code on GitHub with the open-source community. This work presents the design and development of the proposed system, followed by the performance evaluation. Finally, we present a test of our designed system applied to a specific case study: the DC analysis of complex resistive networks through multi-point resistance measurements using only a single voltmeter and current source. Full article

(This article belongs to the Section Sensing Technologies and Precision Measurement)

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14 pages, 1296 KB

Open AccessArticle

Shoulder Muscle Strength Assessment: A Comparative Study of Hand-Held Dynamometers and Load Cell Measurements

by Carla Antonacci, Arianna Carnevale, Letizia Mancini, Alessandro de Sire, Pieter D’Hooghe, Michele Mercurio, Rocco Papalia, Emiliano Schena and Umile Giuseppe Longo

Instruments 2026, 10(1), 2; https://doi.org/10.3390/instruments10010002 - 20 Dec 2025

Viewed by 761

Abstract

Accurate measurement of shoulder muscle strength is important for diagnosis, treatment planning, and monitoring recovery. Hand-held dynamometers (HHDs) are widely used in clinical practice but are affected by operator strength, patient positioning, and device stabilization, particularly under high-load conditions. No previous study has [...] Read more.

Accurate measurement of shoulder muscle strength is important for diagnosis, treatment planning, and monitoring recovery. Hand-held dynamometers (HHDs) are widely used in clinical practice but are affected by operator strength, patient positioning, and device stabilization, particularly under high-load conditions. No previous study has directly compared HHD measurements with a reference load cell in a rigid serial configuration or evaluated the effect of different load cell signal processing strategies on the final strength value. The aim of this study was to compare HHD measurements with those obtained from a reference load cell in a rigid serial configuration and to assess how different signal processing strategies applied to load cell data influence the final outcomes. A custom 3D-printed support was developed to align a commercial HHD and a load cell in series, ensuring identical loading conditions. Measurements were performed under two conditions: (i) application of known weights (9.81–98.10 N) and (ii) standardized strength tasks in five healthy volunteers. Agreement between instruments was evaluated using Bland–Altman analysis and Root Mean Square Error (RMSE). In static validation (i.e., experiments applying know weights), the load cell demonstrated stable performance, with standard deviations below 1% of the applied load. HHD variability increased with load, with RMSE rising from 0.55 N at 9.81 N to 5.06 N at 98.10 N. In human testing, the HHD consistently underestimated muscle strength compared with the load cell, with mean differences ranging from −15 N to −19 N, over exerted force ranges of approximately 20–90 N. Overall, the load cell provided stable reference measurements, while the choice of signal processing strategy influenced the results: plateau-phase analysis tended to reduce systematic bias but did not consistently narrow the limits of agreement. Full article

(This article belongs to the Special Issue Instrumentation and Measurement Methods for Industry 4.0 and IoT)

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18 pages, 3133 KB

Open AccessArticle

Gamma and Neutron Irradiation Effects on Wavelength Shifting Materials for Nuclear and High Energy Physics Applications

by Jessica Scifo, Beatrice D’Orsi, Francesco Filippi, Silvia Cesaroni, Andrea Colangeli, Ilaria Di Sarcina, Basilio Esposito, Davide Flammini, Stefano Loreti, Daniele Marocco, Guglielmo Pagano, Adriano Verna and Alessia Cemmi

Instruments 2026, 10(1), 1; https://doi.org/10.3390/instruments10010001 - 20 Dec 2025

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Abstract

Wavelength-shifting (WLS) materials are used in radiation detectors to convert ultraviolet photons into visible light, enabling improved photon detection in systems such as scintillators and optical diagnostics for nuclear fusion devices. However, the long-term performance of these materials under radiation is still a [...] Read more.

Wavelength-shifting (WLS) materials are used in radiation detectors to convert ultraviolet photons into visible light, enabling improved photon detection in systems such as scintillators and optical diagnostics for nuclear fusion devices. However, the long-term performance of these materials under radiation is still a critical issue in high-dose environments. In this work, we investigated the radiation tolerance of three WLS compounds (TPB, NOL1, and SB2001), each deposited on reflective substrates (ESR and E-PTFE), resulting in six distinct WLS/substrate systems. The samples underwent gamma irradiation at absorbed doses of 100 kGy, 500 kGy, and 1000 kGy, as well as fast neutron (14.1 MeV) irradiation up to a fluence of 1.9 × 10¹³ n/cm². Qualitative photoluminescence and reflectance measurements were performed before and after irradiation to assess changes in optical performance. Gamma exposure caused spectral broadening in several samples, particularly those with TPB and SB2001, with variations of the two metrics used to compare the performance of the materials exceeding 10% at the highest doses. Neutron-induced effects were generally weaker and did not exhibit a clear fluence dependence. Reflectance degradation was also observed, with variations depending on both the WLS material and the deposition method. These findings contribute to the understanding of WLS material stability under radiation and support their qualification for use in optical components exposed to harsh nuclear environments. Full article

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Instruments, Volume 10, Issue 1 (March 2026) – 12 articles

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