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21 pages, 5808 KB

Open AccessArticle

Gyroscope Denoising Algorithm Based on EMD-SSA-VMD Double-Layer Decomposition

by Chuanqian Lv, Yaohong Zhao, Fangzhou Li and Haibo Luo

Sensors 2026, 26(4), 1367; https://doi.org/10.3390/s26041367 - 21 Feb 2026

Viewed by 1388

Abstract

To reduce random errors effectively and improve measurement precision in MEMS gyroscopes, we establish a dual-layer noise suppression method named EMD-SSA-VMD. The algorithm is grounded in empirical mode decomposition (EMD) and variational mode decomposition (VMD), incorporating the sparrow search algorithm (SSA) and entropy [...] Read more.

To reduce random errors effectively and improve measurement precision in MEMS gyroscopes, we establish a dual-layer noise suppression method named EMD-SSA-VMD. The algorithm is grounded in empirical mode decomposition (EMD) and variational mode decomposition (VMD), incorporating the sparrow search algorithm (SSA) and entropy theory. The process starts by breaking down the signal into a series of intrinsic mode functions (IMFs) and a residual via EMD. By calculating the power spectral entropy (PSE) of IMFs, we can sort the signal components into three categories: noise signals, mixed signals, and effective signals. The mixed signals then undergo VMD processing, where SSA optimizes the key decomposition parameters. The sample entropy (SE) of the IMFs from VMD is computed to distinguish between actual signal components and noise. Finally, we combine all valuable signals to reconstruct the denoising signal. MATLAB(R2024b) simulation results show that this algorithm improves both the Signal-to-Noise Ratio (SNR) and the Root Mean Square Error (RMSE), demonstrating a more efficient removal of noise. Experiments on actual gyroscope data confirm these improvements, yielding higher SNR and a waveform that closely matches the original signal. This proves the algorithm’s practical value in engineering applications. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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21 pages, 21562 KB

Open AccessArticle

A Redundant-Sensing-Based Six-Axis Force/Torque Sensor Enabling Compactness and High Sensitivity

by Seung Yeon Lee, Jae Yoon Sim, Dong-Yeop Seok, Yong Bum Kim, Jaeyoon Shim, Uikyum Kim and Hyouk Ryeol Choi

Sensors 2026, 26(3), 871; https://doi.org/10.3390/s26030871 - 28 Jan 2026

Viewed by 627

Abstract

Capacitive sensors are widely adopted in compact robotic systems due to their simple structure, ease of fabrication, and scalability for miniaturized designs. However, sensor miniaturization inevitably leads to reduced sensitivity and increased sensitivity imbalance, particularly in torque measurements, due to limited electrode area [...] Read more.

Capacitive sensors are widely adopted in compact robotic systems due to their simple structure, ease of fabrication, and scalability for miniaturized designs. However, sensor miniaturization inevitably leads to reduced sensitivity and increased sensitivity imbalance, particularly in torque measurements, due to limited electrode area and spatial constraints. To address these limitations, this paper presents a compact six-axis force/torque (F/T) sensor based on a redundant capacitive sensing architecture. The proposed sensing architecture employs a symmetric arrangement of multiple capacitive electrodes, providing redundant capacitance measurements that enhance sensitivity while reducing coupling errors under multi-axis loading conditions. By exploiting redundant capacitive responses rather than relying on complex mechanical separation, the proposed design effectively improves measurement robustness. Based on this architecture, a compact six-axis F/T sensor with a diameter of 20 mm and a height of 12 mm is developed. Experimental validation demonstrates that the proposed sensor achieves linearity (>98.2%) with reduced cross-axis interference, confirming improved sensitivity and reliable multi-axis F/T measurement. This work provides a practical and scalable solution for integrating high-performance six-axis F/T sensing into space-constrained robotic systems. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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20 pages, 7268 KB

Open AccessArticle

A Two-Dimensional (2-D) Sensor Network Architecture with Artificial Intelligence Models for the Detection of Magnetic Anomalies

by Paolo Gastaldo, Rodolfo Zunino, Alessandro Bellesi, Alessandro Carbone, Marco Gemma and Edoardo Ragusa

Sensors 2026, 26(3), 764; https://doi.org/10.3390/s26030764 - 23 Jan 2026

Viewed by 1036

Abstract

The paper presents the development and preliminary evaluation of a two-dimensional (2-D) network of magnetometers for magnetic anomaly detection. The configuration significantly improves over the existing one-dimensional (1-D) architecture, as it enhances the spatial characterization of magnetic anomalies through the simultaneous acquisition of [...] Read more.

The paper presents the development and preliminary evaluation of a two-dimensional (2-D) network of magnetometers for magnetic anomaly detection. The configuration significantly improves over the existing one-dimensional (1-D) architecture, as it enhances the spatial characterization of magnetic anomalies through the simultaneous acquisition of data over an extended area. This leads to a reliable estimation of the target motion parameters. Each sensor node in the network includes a custom-designed electronic system, integrating a biaxial fluxgate magnetometer that operates in null mode. Deep learning models process the raw measurements collected by the magnetometers and extract structured information that enables both automated detection and preliminary target tracking. In the experimental evaluation, a

5 \times 5

array of nodes was deployed over a

12 \times 12

m² area for terrestrial tests, using moving ferromagnetic cylinders as targets. The results confirmed the feasibility of the 2-D configuration and supported its integration into intelligent, real-time surveillance systems for security and underwater monitoring applications. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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18 pages, 8564 KB

Open AccessArticle

3D-Printed Components for Cost-Effective Polarisation Sensing of Terahertz Radiation

by Adrianna Nieradka, Mateusz Kaluza, Paweł Komorowski and Agnieszka Siemion

Sensors 2025, 25(23), 7106; https://doi.org/10.3390/s25237106 - 21 Nov 2025

Viewed by 854

Abstract

This study covers the research on 3D-printed structures for the polarisation sensing in the terahertz (THz) frequency range. Proposed polarisers can be combined with various detectors to obtain cost-effective and easily accessible polarisation-sensitive sensors. Multiple commercially available filaments for 3D printing with various [...] Read more.

This study covers the research on 3D-printed structures for the polarisation sensing in the terahertz (THz) frequency range. Proposed polarisers can be combined with various detectors to obtain cost-effective and easily accessible polarisation-sensitive sensors. Multiple commercially available filaments for 3D printing with various additives were used to obtain good-quality, efficient optical components. Fused deposition modelling (FDM) was selected as the manufacturing technique due to the reliable and repeatable results of 3D printing technology. The research focused on elements with sub-THz features designed to determine the polarisation of incident radiation. Manufactured polarisers have been tested in two setups, verifying narrow-band operation at the design wavelength as well as broad-band operation across the THz spectrum. Both setups allowed the change of the angular position of the examined elements around the optical axis. The final results proved the possibility of obtaining cost-efficient polarisers functioning comparable to the commercially available wire-grid polarisers. Constructive conclusions were drawn to determine the proper materials, their additives, the chosen fill factors (FFs), and the dimensions of the polarisers, ensuring optimal performance and efficiency in manipulating THz radiation. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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22 pages, 2436 KB

Open AccessArticle

Assessing BME688 Sensor Performance Under Controlled Outdoor-like Environmental Conditions

by Enza Panzardi, Ada Fort, Valerio Vignoli, Irene Cappelli, Luigi Gaioni, Matteo Verzeroli, Salvatore Dello Iacono and Alessandra Flammini

Sensors 2025, 25(23), 7102; https://doi.org/10.3390/s25237102 - 21 Nov 2025

Viewed by 3666

Abstract

Low-cost miniaturized gas sensors are increasingly considered for outdoor air quality monitoring, yet their performance under real-world environmental conditions remains insufficiently characterized. This work evaluates the dynamic gas response of the Bosch BME688 sensor, whose metal oxide sensing layer is based on tin [...] Read more.

Low-cost miniaturized gas sensors are increasingly considered for outdoor air quality monitoring, yet their performance under real-world environmental conditions remains insufficiently characterized. This work evaluates the dynamic gas response of the Bosch BME688 sensor, whose metal oxide sensing layer is based on tin dioxide (SnO₂) material, focusing on its sensitivity, selectivity, and dynamic response to four representative air pollutants: nitrogen dioxide (NO₂), carbon monoxide (CO), sulfur dioxide (SO₂), and isobutylene. This study provides both quantitative performance metrics and a physicochemical interpretation of the sensing mechanism. Controlled experiments were conducted in a custom test chamber to facilitate the precise regulation of temperature, humidity, and gas concentrations in the ppm to sub-ppm range. Despite large variability in the baseline resistance across devices, normalization yields consistent behavior, enabling cross-sensor comparability. The results show that the optimum operating temperatures fall in the range of 360–400 °C, where response and recovery times are reduced to a few minutes, compatible with mobile sensing requirements. Moreover, humidity strongly influences sensor behavior: it generally decreases sensitivity but improves kinetics, and in the case of CO, it enables enhanced responses through additional hydroxyl-mediated pathways. These findings confirm the feasibility of deploying BME688 sensors in distributed outdoor monitoring platforms, provided that humidity and temperature effects are properly addressed through calibration or compensation strategies. In addition, the variability observed in baseline resistance highlights the need for normalization and, consequently, individual calibration steps for each sensor under reference conditions in order to ensure cross-sensor comparability. The findings provided in this study provide support for the design of robust, low-cost air monitoring networks. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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29 pages, 5693 KB

Open AccessArticle

Outdoor Microphone Range Tests and Spectral Analysis of UAV Acoustic Signatures for Array Development

by Gabriel Jekateryńczuk and Zbigniew Piotrowski

Sensors 2025, 25(22), 7057; https://doi.org/10.3390/s25227057 - 19 Nov 2025

Viewed by 4291

Abstract

Acoustic sensing is a passive and cost-effective option for unmanned aerial vehicle detection, where both signal processing and microphone hardware jointly determine field performance. In this study, we focus on the hardware front-end as a foundation for improving the reliability of subsequent DSP- [...] Read more.

Acoustic sensing is a passive and cost-effective option for unmanned aerial vehicle detection, where both signal processing and microphone hardware jointly determine field performance. In this study, we focus on the hardware front-end as a foundation for improving the reliability of subsequent DSP- or AI-based detection methods. We present a detection-focused comparison of several microphones in outdoor tests, combining calibrated range measurements with spectral analysis of real unmanned aerial vehicle emissions from three platforms. We report hardware metrics only: signal-to-noise ratio, effective detection range, attenuation slope with distance, and the low-frequency background floor. Across wind conditions and source orientations, the RØDE NTG-2 with WS6 windshield delivered the most balanced performance: in strong wind, it extended the detection range over the bare NTG-2 by approximately 31–131% (depending on azimuth), lowered the low-frequency noise floor by about 2–3 decibels, and matched or increased the wideband signal-to-noise ratio by 1.8–4.4 decibels. A parabolic NTG-2 achieved very low background noise levels at low frequencies and strong on-axis reach but proved vulnerable to gust-induced transients. Based on this evidence, we propose an eight-channel, dual-tier array of NTG-2 + WS6 elements that preserves near-hemispherical coverage and phase coherence, establishing a practical hardware baseline for outdoor acoustic unmanned aerial vehicle detection and a reproducible platform for subsequent localization and classification studies. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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15 pages, 2134 KB

Open AccessArticle

Enhanced Reaction Time Measurement System Based on 3D Accelerometer in Athletics

by Antonio Pousibet-Garrido, Juan A. Moreno-Pérez, Pablo Escobedo, Israel Caraballo, José V. Gutiérrez-Manzanedo, José L. González-Montesinos and Miguel A. Carvajal

Sensors 2025, 25(21), 6730; https://doi.org/10.3390/s25216730 - 3 Nov 2025

Cited by 2 | Viewed by 2590

Abstract

Reaction time (RT) is a key measure of neuromuscular and cognitive performance, but most existing methods rely on laboratory equipment or focus on localized actions such as finger taps or foot lifts, limiting their relevance for whole-body movements. In this work, we present [...] Read more.

Reaction time (RT) is a key measure of neuromuscular and cognitive performance, but most existing methods rely on laboratory equipment or focus on localized actions such as finger taps or foot lifts, limiting their relevance for whole-body movements. In this work, we present a portable inertial measurement unit (IMU)-based system specifically designed to measure RT during sprint starts. The device integrates a triaxial accelerometer (ICM-20948, ±16 g) and an ESP32 microcontroller, which generates an auditory stimulus, acquires acceleration data at 1 kHz, and computes movement onset in real time. A fixed acceleration threshold, determined from calibration against a high-speed camera reference, was used to detect the first voluntary movement. Both desktop and smartphone applications were implemented to control the system, provide feedback, and store test data. Validation experiments showed good agreement with the high-speed camera used as a reference (R² = 0.9391), with a mean bias of –1.35 ms and 95% limits of agreement within ±25 ms. The proposed system combines high temporal resolution, portability, and straightforward deployment, enabling reliable assessment of whole-body RT in realistic sports and research environments. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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21 pages, 2960 KB

Open AccessArticle

AudioUnlock: Device-to-Device Authentication via Acoustic Signatures and One-Class Classifiers

by Alfred Anistoroaei, Patricia Iosif, Camelia Burlacu, Adriana Berdich and Bogdan Groza

Sensors 2025, 25(21), 6510; https://doi.org/10.3390/s25216510 - 22 Oct 2025

Viewed by 970

Abstract

Acoustic fingerprints can be used for device-to-device authentication due to manufacturing-induced variations in microphones and speakers. However, previous works have focused mostly on recognizing single devices from a set of multiple devices, which may not be sufficiently realistic since in practice, a single [...] Read more.

Acoustic fingerprints can be used for device-to-device authentication due to manufacturing-induced variations in microphones and speakers. However, previous works have focused mostly on recognizing single devices from a set of multiple devices, which may not be sufficiently realistic since in practice, a single device has to be recognized from a very large pool of devices that are not available for training machine learning classifiers. Therefore, in this work, we focus on one-class classification algorithms, namely one-class Support Vector Machine and the local outlier factor. As such, learning the fingerprint of a single device is sufficient to recognize the legitimate device and reject all other attempts to impersonate it. The proposed application can also rely on cloud-based deployment to free the smartphone from intensive computational tasks or data storage. For the experimental part, we rely both on smartphones and an automotive-grade Android headunit, exploring in-vehicle environments as the main area of application. We create a dataset consisting of more than 5000 measurements and achieve a recognition rate ranging from 50% to 100% for different devices under various environmental conditions such as distance, altitude, and component aging. These conditions also serve as our limitations, however, we propose different solutions for overcoming them, which are part of our threat model. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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22 pages, 3283 KB

Open AccessArticle

Enhanced Near-Surface Flaw Detection in Additively Manufactured Metal Ti-5Al-5V-5Mo-3Cr Using the Total Focusing Method

by Kate van Herpt, Mohammad E. Bajgholi, P. Ross Underhill, Catalin Mandache and Thomas W. Krause

Sensors 2025, 25(20), 6425; https://doi.org/10.3390/s25206425 - 17 Oct 2025

Cited by 1 | Viewed by 1030

Abstract

Additive manufacturing (AM) enables the fabrication of complex components with high geometric freedom, but it can introduce near-surface flaws due to rapid solidification, resulting in porosity and lack of fusion. In addition, localized melting and steep thermal gradients favor the formation of micro-cracks. [...] Read more.

Additive manufacturing (AM) enables the fabrication of complex components with high geometric freedom, but it can introduce near-surface flaws due to rapid solidification, resulting in porosity and lack of fusion. In addition, localized melting and steep thermal gradients favor the formation of micro-cracks. Conventional ultrasonic techniques have shortcomings in detecting such flaws because of front-wall interference, further affected by surface roughness and anisotropy. This study evaluates the effectiveness of the Total Focusing Method (TFM), an advanced ultrasonic imaging technique implemented in Full Matrix Capture (FMC), for near-surface flaw detection in Laser Powder Bed Fusion (LPBF) AM components. To assess TFM performance, subsurface side-drilled holes (SDHs) in AM Ti-5Al-5V-5Mo-3Cr (Ti-5553) material were used as the reference reflectors and compared with Phased Array Ultrasonic Testing (PAUT) under identical conditions. Results showed that TFM achieved higher spatial resolution and more reliable detection of shallow flaws, successfully detecting features as shallow as 0.40 ± 0.05 mm below the surface, whereas PAUT was limited to greater depths. These findings demonstrate TFM as a reliable non-destructive evaluation method for shallow flaws in AM parts, while contributing one of the first systematic comparative datasets of PAUT and TFM for shallow SDHs in LPBF titanium alloys. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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18 pages, 3326 KB

Open AccessArticle

Micro-Vibrations Analysis in LEO CubeSats Using MEMS Accelerometers

by Sándor Gyányi, Róbert Szabolcsi, Péter János Varga, Gyula Horváth, Péter Horváth and Tibor Wührl

Sensors 2025, 25(18), 5917; https://doi.org/10.3390/s25185917 - 22 Sep 2025

Cited by 1 | Viewed by 1466

Abstract

Small satellites or CubeSats orbiting in low Earth orbit (LEO) have become increasingly popular in Earth Observation missions, where high-resolution imaging is essential. Due to the lower mass of these spacecrafts, they are more sensitive to vibrations, and image quality can be particularly [...] Read more.

Small satellites or CubeSats orbiting in low Earth orbit (LEO) have become increasingly popular in Earth Observation missions, where high-resolution imaging is essential. Due to the lower mass of these spacecrafts, they are more sensitive to vibrations, and image quality can be particularly negatively affected by micro-vibrations. These vibrations originate from on-board subsystems, such as the Attitude Determination and Control System (ADCS), which uses reaction wheels to change the orientation of the satellite. The main goal of our research was to analyze these micro-vibrations so that the acquired data could be used for post-correction of camera images. Obuda University, as a participant in a research project, was tasked with designing and building a micro-vibration measuring device for the LEO CubeSat called WREN-1. In the first phase of the project, the satellite was launched into orbit, and test data were collected and analyzed. The results are presented in this article. Based on the data obtained in this way, the next step will be to analyze the images taken at the same time as the vibration measurements and to search for a correlation between the image quality and the vibrations. Based on the results of the entire project, it could be possible to improve the image quality of the onboard cameras of microsatellites. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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16 pages, 1755 KB

Open AccessArticle

Development of an Equivalent Circuit to Analyze the Receiving Characteristics of a Class IV Flextensional Transducer

by Eunseo Kang and Yongrae Roh

Sensors 2025, 25(18), 5661; https://doi.org/10.3390/s25185661 - 11 Sep 2025

Viewed by 901

Abstract

Flextensional transducers are widely utilized as underwater acoustic transducers with broadband and high-sensitivity characteristics in low-frequency ranges. In this study, we have developed an equivalent circuit to facilitate the design of a class IV flextensional hydrophone. The end-plate of the class IV transducer [...] Read more.

Flextensional transducers are widely utilized as underwater acoustic transducers with broadband and high-sensitivity characteristics in low-frequency ranges. In this study, we have developed an equivalent circuit to facilitate the design of a class IV flextensional hydrophone. The end-plate of the class IV transducer is essential for sustaining the structure while keeping the hydrophone waterproof in underwater environments, and the presence or absence of the end-plate changes the hydrophone’s receiving performance. Previous studies have not included the end-plate in their equivalent circuit configurations, but this study proposes a new equivalent circuit model that incorporates an elastic boundary condition representing the constraint imposed on the shell by the compressive force of the end-plate. The receiving voltage sensitivity, calculated using the proposed equivalent circuit model, shows a high degree of agreement with the finite element analysis results, confirming that the mechanical influence of the end-plate significantly affects the hydrophone’s acoustic receiver characteristics. The proposed equivalent circuit approach offers faster computation while maintaining sufficient accuracy compared to the finite element analysis, making it a useful tool for future hydrophone design. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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15 pages, 4761 KB

Open AccessArticle

A Scalable Sub-Picosecond TDC Based on Analog Sampling of Dual-Phase Signals from a Free-Running Oscillator

by Roberto Cardella, Luca Iodice, Lorenzo Paolozzi, Thanushan Kugathasan, Antonio Picardi, Carlo Alberto Fenoglio, Pierpaolo Valerio, Fulvio Martinelli, Roberto Cardarelli and Giuseppe Iacobucci

Sensors 2025, 25(17), 5577; https://doi.org/10.3390/s25175577 - 6 Sep 2025

Viewed by 1824

Abstract

This work presents a novel time-to-digital converter based on the analog sampling of dual-phase periodic signals generated from a free-running oscillator. A proof-of-concept ASIC, implemented in 130 nm CMOS technology, achieves an average single-shot precision of 0.9 ps-rms for time intervals up to [...] Read more.

This work presents a novel time-to-digital converter based on the analog sampling of dual-phase periodic signals generated from a free-running oscillator. A proof-of-concept ASIC, implemented in 130 nm CMOS technology, achieves an average single-shot precision of 0.9 ps-rms for time intervals up to 3 ns, with a best performance of 0.79 ps-rms. It maintains a precision below 3.7 ps-rms for intervals up to 25 ns. The design demonstrates excellent linearity, with a peak-to-peak differential nonlinearity of 0.56 LSB and a peak-to-peak integral nonlinearity of 1.43 LSB. The free-running oscillator is shareable across multiple channels, enabling power consumption of approximately 4.1 mW per channel and efficient area utilization. These features make the design highly suitable for detection systems requiring picosecond-level precision and high channel density, such as silicon pixel sensors, SPADs, LiDARs, and time-correlated single-photon counting systems. Furthermore, the architecture shows strong potential for use in high-count-rate applications, reaching up to 22 Mcps. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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15 pages, 4427 KB

Open AccessFeature PaperArticle

AlScN Thin Films for the Piezoelectric Transduction of Suspended Microchannel Resonators

by Yara Abdelaal, Marco Liffredo and Luis Guillermo Villanueva

Sensors 2025, 25(17), 5370; https://doi.org/10.3390/s25175370 - 31 Aug 2025

Cited by 1 | Viewed by 2527

Abstract

Suspended microchannel resonators (SMRs) are powerful tools for mass, density, and viscosity sensing. Among various transduction methods, full piezoelectric transduction offers key advantages, including on-chip integration, low energy dissipation, and linear response. This work explores sub-200 nm Al_0.6Sc_0.4N thin [...] Read more.

Suspended microchannel resonators (SMRs) are powerful tools for mass, density, and viscosity sensing. Among various transduction methods, full piezoelectric transduction offers key advantages, including on-chip integration, low energy dissipation, and linear response. This work explores sub-200 nm Al_0.6Sc_0.4N thin films for SMR transduction, benchmarking them against their well-established AlN predecessor. By integrating the piezoelectric stack into low-stress silicon nitride (ls-SiN_x) beam resonators, we investigate the impact of bottom electrode design, photoresist removal prior to deposition, and deposition bias on film quality. Characterization includes X-ray diffraction (XRD), scanning electron microscopy (SEM), d₃₁ piezoelectric coefficient, relative dielectric permittivity, and breakdown field measurements. Results illustrate the impacts of the studied parameters and demonstrate a fourfold increase in d₃₁, compared to AlN, confirming the strong potential of Al_0.6Sc_0.4N for high-performance SMR transduction. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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21 pages, 11834 KB

Open AccessArticle

Influence of the Ozonation Process on Expanded Graphite for Textile Gas Sensors

by Paulina Rzeźniczak, Ewa Skrzetuska, Mohanapriya Venkataraman and Jakub Wiener

Sensors 2025, 25(17), 5328; https://doi.org/10.3390/s25175328 - 27 Aug 2025

Viewed by 1111

Abstract

In view of the growing demand for flexible, conductive and functional materials for textile gas sensor applications, the effects of ozonation on the properties of expanded graphite (EG) in textile structures were analyzed. Four types of fabrics (cotton, polyamide, viscose, para-aramid) coated with [...] Read more.

In view of the growing demand for flexible, conductive and functional materials for textile gas sensor applications, the effects of ozonation on the properties of expanded graphite (EG) in textile structures were analyzed. Four types of fabrics (cotton, polyamide, viscose, para-aramid) coated with pastes containing EG, which had previously been subjected to a 15-min and 30-min ozonation process, were examined. The paste was prepared using Ebecryl 2002 and the photoinitiator Esacure DP250 and then applied by screen printing. Surface resistance, scanning microscopy and wetting angle analyses were performed. The results showed that short-term ozonation (15 min) notably improved the electrical conductivity and adhesion of EG to the textile substrate, while longer exposure (30 min) led to deterioration of the conductive properties due to excessive functionalization and fragmentation of the conductive layer. The lowest surface resistance was observed in the sample subjected to 15 min of ozonation. The conclusions indicate that a properly controlled ozonation process can increase the usability of EG in sensor applications, especially in the context of smart clothing; however, the optimization of the modification time is crucial for maintaining the integrity and durability of the conductive layer. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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13 pages, 3218 KB

Open AccessArticle

Design of a Rapid and Accurate Calibration System for Pressure Sensors with Minimized Temperature Variation

by Juntong Cui, Shubin Zhang and Yanfeng Jiang

Sensors 2025, 25(17), 5288; https://doi.org/10.3390/s25175288 - 25 Aug 2025

Viewed by 5788

Abstract

Miniaturized pressure sensors fabricated via micro-electro-mechanical systems (MEMSs) technology are ubiquitous in modern applications. However, the massively produced MEMS pressure sensors, prior to being practically used, need to be calibrated one by one to eliminate or minimize nonlinearity and zero drift. This paper [...] Read more.

Miniaturized pressure sensors fabricated via micro-electro-mechanical systems (MEMSs) technology are ubiquitous in modern applications. However, the massively produced MEMS pressure sensors, prior to being practically used, need to be calibrated one by one to eliminate or minimize nonlinearity and zero drift. This paper presents a systematic design for the testing and calibration process of MEMS-based absolute pressure sensors. Firstly, a numerical analysis is carried out using finite element method (FEM) simulation, which verifies the accuracy of the temperature control of the physical calibration system. The simulation results reveal a slight non-uniformity of temperature distribution, which is then taken into consideration in the calibration algorithm. Secondly, deploying a home-made calibration system, the MEMS pressure sensors are tested automatically and rapidly. The experimental results show that each batch, which consists of nine sensors, can be calibrated in 80 min. The linearity and temperature coefficient (TC) of the pressure sensors are reduced from 46.5% full-scale (FS) and −1.35 × 10⁻⁴ V·K⁻¹ to 1.5% FS and −8.8 × 10⁻⁷ V·K⁻¹. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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21 pages, 5062 KB

Open AccessArticle

Experimental Evaluation of Rolling Resistance in Omnidirectional Wheels Under Quasi-Static Conditions

by Sławomir Duda, Grzegorz Gembalczyk, Tomasz Machoczek and Zygmunt Kowalik

Sensors 2025, 25(16), 5026; https://doi.org/10.3390/s25165026 - 13 Aug 2025

Cited by 3 | Viewed by 1679

Abstract

This paper presents the results of experimental research on rolling resistance forces occurring during the motion of omnidirectional wheels equipped with dual rows of passive rollers. Due to the complexity of wheel–surface interactions and the stochastic nature of contact transitions, such wheels are [...] Read more.

This paper presents the results of experimental research on rolling resistance forces occurring during the motion of omnidirectional wheels equipped with dual rows of passive rollers. Due to the complexity of wheel–surface interactions and the stochastic nature of contact transitions, such wheels are often characterized experimentally rather than analytically. A custom-built test stand was used to measure resistance forces for different wheel orientations (0°, 30°, 45°, 60°, and 90°) and two vertical loads (117.7 N and 215.8 N) on two surface types: industrial concrete and anodized aluminum. The results demonstrated a strong influence of wheel orientation on resistance, with the highest mean force recorded at 60° for both loads. The results revealed an oscillatory pattern in the resistance force, strongly influenced by the angular position of the wheel. For concrete, mean forces ranged from 1.04 N to 10.34 N, while for aluminum, they ranged from 1.08 N to 10.11 N. Significant oscillations and occasional negative force values were observed, attributed to roller geometry and wheel irregularities. The data obtained are useful for validating numerical models and improving the design and control of mobile robots using omnidirectional wheels. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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15 pages, 4403 KB

Open AccessArticle

ColorX: A Fitness Tracker-Based Device for Rapid, Optical Sensing of Water Quality Parameters

by Venkata V. B. Yallapragada, Adarsh Ananthachar, U. Gowda, F. ní Chlochasaigh, L. O’Faolain and G. C. R. Devarapu

Sensors 2025, 25(16), 4935; https://doi.org/10.3390/s25164935 - 9 Aug 2025

Viewed by 1568

Abstract

Optical sensors have emerged as a popular technology for sensing biological and chemical analytes in various fields, including environmental monitoring, toxicology, disease/infection screening, and food processing, due to their ease of use, high sensitivity, and specificity. In this study, we introduce ColorX, an [...] Read more.

Optical sensors have emerged as a popular technology for sensing biological and chemical analytes in various fields, including environmental monitoring, toxicology, disease/infection screening, and food processing, due to their ease of use, high sensitivity, and specificity. In this study, we introduce ColorX, an ultra-portable and smart spectrophotometric device based on a commercially available fitness tracker. ColorX exploits the in-built LEDs and photodiodes of a fitness tracker for wavelength-specific absorption measurements and can be controlled wirelessly using a companion smartphone app. The device’s raw data are transmitted via Bluetooth and stored on the app for analysis and data visualisation. We validated the performance of ColorX against a standard benchtop spectrophotometer by experimentally testing five different measurements related to water quality: nitrite (>0.07 mg/L, %avgCV: 1.06)), sulphate (>18 mg/L, %avgCV: 0.39), chromium (>0.002 mg/L, %avgCV: 0.51), free chlorine (>0.005 mg/L, %avgCV: 0.68), and turbidity (>2.97 NTU, %avgCV: 1.04). Our results showed that ColorX had comparable performance to the benchmark spectrophotometer (R² values > 0.9 in all cases). Due to its ultra-portability, water-proof design, wireless control, and smartphone-aided data analysis, we believe ColorX will be highly beneficial for a wide range of on-field spectrophotometric applications. Our work demonstrates the potential of frugal science to develop affordable and accessible technology for optical sensing. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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21 pages, 5425 KB

Open AccessArticle

Designing a Capacitive Sensor to Detect Series Arcs in Aircraft HVDC Electrical Systems

by Gema Salinero and Guillermo Robles

Sensors 2025, 25(16), 4886; https://doi.org/10.3390/s25164886 - 8 Aug 2025

Viewed by 1542

Abstract

The transition toward more electric aircraft (MEA) and all-electric aircraft (AEA) has driven the adoption of high-voltage DC (HVDC) electrical architectures to meet increasing power demands while reducing weight and enhancing overall efficiency. However, HVDC systems introduce new challenges, particularly concerning insulation reliability [...] Read more.

The transition toward more electric aircraft (MEA) and all-electric aircraft (AEA) has driven the adoption of high-voltage DC (HVDC) electrical architectures to meet increasing power demands while reducing weight and enhancing overall efficiency. However, HVDC systems introduce new challenges, particularly concerning insulation reliability and the detection of in-flight series arc faults. This paper presents the design and evaluation of a capacitive sensor specifically developed to detect series arc faults in HVDC electrical systems for aerospace applications. A model of the sensor is proposed and validated through both simulations and experimental measurements using a step response test. The results show excellent agreement between the model and the physical setup. After validating the capacitive coupling value and its response to high-frequency signals, series arcs were generated in the laboratory to evaluate the sensor’s performance under realistic operating conditions, which involve different signal dynamics. The results are highly satisfactory and confirm the feasibility of using capacitive sensing for early arc detection, particularly aligned with the stringent requirements of more electric aircraft (MEA) and all-electric aircraft (AEA). The proposed sensor thus enables non-intrusive detection of series arc faults in compact, lightweight, and safety-critical environments. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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22 pages, 4262 KB

Open AccessArticle

Tribo-Dynamics of Dual-Star Planetary Gear Systems: Modeling, Analysis, and Experiments

by Jiayu Zheng, Yonggang Xiang, Changzhao Liu, Yixin Wang and Zonghai Mou

Sensors 2025, 25(15), 4709; https://doi.org/10.3390/s25154709 - 30 Jul 2025

Cited by 1 | Viewed by 1039

Abstract

To address the unclear coupling mechanism between thermal elastohydrodynamic lubrication (TEHL) and dynamic behaviors in planetary gear systems, a novel tribo-dynamic model for dual-star planetary gears considering TEHL effects is proposed. In this model, a TEHL surrogate model is first established to determine [...] Read more.

To address the unclear coupling mechanism between thermal elastohydrodynamic lubrication (TEHL) and dynamic behaviors in planetary gear systems, a novel tribo-dynamic model for dual-star planetary gears considering TEHL effects is proposed. In this model, a TEHL surrogate model is first established to determine the oil film thickness and sliding friction force along the tooth meshing line. Subsequently, the dynamic model of the dual-star planetary gear transmission system is developed through coordinate transformations of the dual-star gear train. Finally, by integrating lubrication effects into both time-varying mesh stiffness and time-varying backlash, a tribo-dynamic model for the dual-star planetary gear transmission system is established. The study reveals that the lubricant film thickness is positively correlated with relative sliding velocity but negatively correlated with unit line load. Under high-speed conditions, a thickened oil film induces premature meshing contact, leading to meshing impacts. In contrast, under high-torque conditions, tooth deformation dominates meshing force fluctuations while lubrication influence diminishes. By establishing a test bench for the planetary gear transmission system, the obtained simulation conclusions are verified. This research provides theoretical and experimental support for the design of high-reliability planetary gear systems. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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15 pages, 1991 KB

Open AccessArticle

Hybrid Deep–Geometric Approach for Efficient Consistency Assessment of Stereo Images

by Michał Kowalczyk, Piotr Napieralski and Dominik Szajerman

Sensors 2025, 25(14), 4507; https://doi.org/10.3390/s25144507 - 20 Jul 2025

Viewed by 1645

Abstract

We present HGC-Net, a hybrid pipeline for assessing geometric consistency between stereo image pairs. Our method integrates classical epipolar geometry with deep learning components to compute an interpretable scalar score A, reflecting the degree of alignment. Unlike traditional techniques, which may overlook subtle [...] Read more.

We present HGC-Net, a hybrid pipeline for assessing geometric consistency between stereo image pairs. Our method integrates classical epipolar geometry with deep learning components to compute an interpretable scalar score A, reflecting the degree of alignment. Unlike traditional techniques, which may overlook subtle miscalibrations, HGC-Net reliably detects both severe and mild geometric distortions, such as sub-degree tilts and pixel-level shifts. We evaluate the method on the Middlebury 2014 stereo dataset, using synthetically distorted variants to simulate misalignments. Experimental results show that our score degrades smoothly with increasing geometric error and achieves high detection rates even at minimal distortion levels, outperforming baseline approaches based on disparity or calibration checks. The method operates in real time (12.5 fps on 1080p input) and does not require access to internal camera parameters, making it suitable for embedded stereo systems and quality monitoring in robotic and AR/VR applications. The approach also supports explainability via confidence maps and anomaly heatmaps, aiding human operators in identifying problematic regions. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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23 pages, 3721 KB

Open AccessArticle

Influence of Surface Isolation Layers on High-Voltage Tolerance of Small-Pitch 3D Pixel Sensors

by Jixing Ye and Gian-Franco Dalla Betta

Sensors 2025, 25(14), 4478; https://doi.org/10.3390/s25144478 - 18 Jul 2025

Viewed by 802

Abstract

In recent years, 3D pixel sensors have been a topic of increasing interest within the High Energy Physics community. Due to their inherent radiation hardness, demonstrated up to a fluence of

3 \times 10^{16}

1 MeV equivalent neutrons per square centimeter, 3D [...] Read more.

In recent years, 3D pixel sensors have been a topic of increasing interest within the High Energy Physics community. Due to their inherent radiation hardness, demonstrated up to a fluence of

3 \times 10^{16}

1 MeV equivalent neutrons per square centimeter, 3D pixel sensors have been used to equip the innermost tracking layers of the ATLAS and CMS detector upgrades at the High-Luminosity Large Hadron Collider. Additionally, the next generation of vertex detectors calls for precise measurement of charged particle timing at the pixel level. Owing to their fast response times, 3D sensors present themselves as a viable technology for these challenging applications. Nevertheless, both radiation hardness and fast timing require 3D sensors to be operated with high bias voltages on the order of ∼150 V and beyond. Special attention should therefore be devoted to avoiding problems that could cause premature electrical breakdown, which could limit sensor performance. In this paper, TCAD simulations are used to gain deep insight into the impact of surface isolation layers (i.e., p-stop and p-spray) used by different vendors on the high-voltage tolerance of small-pitch 3D sensors. Results relevant to different geometrical configurations and irradiation scenarios are presented. The advantages and disadvantages of the available technologies are discussed, offering guidance for design optimization. Experimentalmeasurements from existing samples based on both isolation techniques show good agreement with simulated breakdown voltages, thereby validating the simulation approach. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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43 pages, 6150 KB

Open AccessArticle

The Effect of Surface Roughness on Supersonic Nozzle Flow and Electron Dispersion at Low Pressure Conditions

by Pavla Šabacká, Jiří Maxa, Robert Bayer, Tomáš Binar and Petr Bača

Sensors 2025, 25(13), 4204; https://doi.org/10.3390/s25134204 - 5 Jul 2025

Cited by 1 | Viewed by 1118

Abstract

This study investigates supersonic flow within a nozzle under low-pressure conditions at the continuum mechanics boundary. This phenomenon is commonly encountered in applications such as the differentially pumped chamber of an Environmental Scanning Electron Microscope (ESEM), which employs an aperture to separate two [...] Read more.

This study investigates supersonic flow within a nozzle under low-pressure conditions at the continuum mechanics boundary. This phenomenon is commonly encountered in applications such as the differentially pumped chamber of an Environmental Scanning Electron Microscope (ESEM), which employs an aperture to separate two regions with a great pressure gradient. The nozzle geometry and flow control in this region can significantly influence the scattering and loss of the primary electron beam traversing the differentially pumped chamber and aperture. To this end, an experimental chamber was designed to explore aspects of this low-pressure regime, characterized by a varying ratio of inertial to viscous forces. The initial experimental results obtained using pressure sensors from the fabricated experimental chamber were utilized to refine the Ansys Fluent simulation setup, and in this combined approach, initial analyses of supersonic flow and shock waves in low-pressure environments were conducted. The refined Ansys Fluent system demonstrated a very good correspondence with the experimental findings. Subsequently, an analysis of the influence of surface roughness on the resulting flow behavior in low-pressure conditions was performed on this refined model using the refined CFD model. Based on the obtained results, a comparison of the influence of nozzle roughness on the resulting electron beam scattering was conducted for selected low-pressure variants relevant to the operational conditions of the Environmental Scanning Electron Microscope (ESEM). The influence of roughness at elevated working pressures within the ESEM operating regime on reduced electron beam scattering has been demonstrated. At lower pressure values within the ESEM operating regime, this influence is significantly diminished. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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19 pages, 4767 KB

Open AccessArticle

Risk Mitigation of a Heritage Bridge Using Noninvasive Sensors

by Ricky W. K. Chan and Takahiro Iwata

Sensors 2025, 25(12), 3727; https://doi.org/10.3390/s25123727 - 14 Jun 2025

Cited by 1 | Viewed by 1075

Abstract

Bridges are fundamental components of transportation infrastructure, facilitating the efficient movement of people and goods. However, the conservation of heritage bridges introduces additional challenges, encompassing environmental, social, cultural, and economic dimensions of sustainability. This study investigates risk mitigation strategies for a heritage-listed, 120-year-old [...] Read more.

Bridges are fundamental components of transportation infrastructure, facilitating the efficient movement of people and goods. However, the conservation of heritage bridges introduces additional challenges, encompassing environmental, social, cultural, and economic dimensions of sustainability. This study investigates risk mitigation strategies for a heritage-listed, 120-year-old reinforced concrete bridge in Australia—one of the nation’s earliest examples of reinforced concrete construction, which remains operational today. The structure faces multiple risks, including passage of overweight vehicles, environmental degradation, progressive crack development due to traffic loading, and potential foundation scouring from an adjacent stream. Due to the heritage status and associated legal constraints, only non-invasive testing methods were employed. Ambient vibration testing was conducted to identify the bridge’s dynamic characteristics under normal traffic conditions, complemented by non-contact displacement monitoring using laser distance sensors. A digital twin structural model was subsequently developed and validated against field data. This model enabled the execution of various “what-if” simulations, including passage of overweight vehicles and loss of foundation due to scouring, providing quantitative assessments of potential risk scenarios. Drawing on insights gained from the case study, the article proposes a six-phase Incident Response Framework tailored for heritage bridge management. This comprehensive framework incorporates remote sensing technologies for incident detection, digital twin-based structural assessment, damage containment and mitigation protocols, recovery planning, and documentation to prevent recurrence—thus supporting the long-term preservation and functionality of heritage bridge assets. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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20 pages, 9505 KB

Open AccessArticle

ARMA Model for Tracking Accelerated Corrosion Damage in a Steel Beam

by Sina Zolfagharysaravi, Denis Bogomolov, Camilla Bahia Larocca, Federica Zonzini, Lorenzo Mistral Peppi, Marco Lovecchio, Luca De Marchi and Alessandro Marzani

Sensors 2025, 25(8), 2384; https://doi.org/10.3390/s25082384 - 9 Apr 2025

Cited by 3 | Viewed by 2852

Abstract

This paper proposes an enhanced vibration-based damage detection index leveraging autoregressive moving average (ARMA) time-series modeling. The method relies on the fact that material deterioration alters the vibration features of the structure. Thus, the proposed method employs an innovative usage of the ARMA [...] Read more.

This paper proposes an enhanced vibration-based damage detection index leveraging autoregressive moving average (ARMA) time-series modeling. The method relies on the fact that material deterioration alters the vibration features of the structure. Thus, the proposed method employs an innovative usage of the ARMA time-series modeling to capture subtle shifts in the vibration response. Specifically, first, a reference ARMA model is fitted on the acceleration response of the undamaged structure. Next, a damage index (DI) is built from the goodness of fit between predicted responses from the reference ARMA model and the actual measured damaged-state acceleration data. Experimental validation was conducted on a steel beam subjected to a controlled accelerated corrosion (up to 40% thickness loss), simulating real-world degradation. Accelerations due to quick-release tests were collected using two accelerometers, along with thickness measurements providing ground-truth damage progression. Results demonstrate that the proposed method can provide sufficient sensitivity in detecting early-stage corrosion progression. This finding highlights the proposed usage of ARMA model’s potential for early structural damage detection, offering significant advantages for safety and maintenance strategies in civil engineering applications. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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25 pages, 2523 KB

Open AccessReview

Risks Related to Advanced Bridge Monitoring Technologies

by Michal Miške, Pasquale Daponte, Luca De Vito and Lucia Figuli

Sensors 2026, 26(5), 1603; https://doi.org/10.3390/s26051603 - 4 Mar 2026

Viewed by 697

Abstract

Bridge monitoring has undergone a significant transformation with the integration of advanced technologies, including structural health monitoring systems, Internet of Things sensors, unmanned aerial vehicles, artificial intelligence, and cloud computing. These technologies enable continuous real-time data acquisition, processing, and early detection of structural [...] Read more.

Bridge monitoring has undergone a significant transformation with the integration of advanced technologies, including structural health monitoring systems, Internet of Things sensors, unmanned aerial vehicles, artificial intelligence, and cloud computing. These technologies enable continuous real-time data acquisition, processing, and early detection of structural degradation. However, their deployment also introduces a range of emerging risks that require careful consideration. This paper presents descriptive risk listings and proposes a comprehensive risk-governance framework for advanced bridge monitoring using the SWOT analysis. The framework integrates a unified risk taxonomy and assessment that links sensor and AI performance with cyber threat modeling and data governance requirements. The application of two real deployments, the Jindo Bridge SHM program and the Stava Bridge digital-twin implementation, shows how the framework converts heterogeneous measurements for improving bridge lifecycle management with the implementation of advanced monitoring technologies. Compared with prior studies that primarily catalog risks, the contribution of the paper is an interdisciplinary, operationalizable method that couples reliability, security, and governance into a single process, thereby ensuring that advanced technologies enhance, rather than erode, the safety and resilience of bridge infrastructure. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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51 pages, 735 KB

Open AccessReview

Microgrids as a Tool for Energy Self-Sufficiency

by Sławomir Bielecki, Tadeusz Skoczkowski and Marcin Wołowicz

Sensors 2025, 25(21), 6707; https://doi.org/10.3390/s25216707 - 2 Nov 2025

Cited by 2 | Viewed by 3368

Abstract

The article presents an overview of knowledge in the field of energy microgrids as smart structures enabling energy self-sufficiency, with particular emphasis on decarbonisation. Based on a review of the literature and technical solutions, the characteristics have been classified and, emphasising the potential [...] Read more.

The article presents an overview of knowledge in the field of energy microgrids as smart structures enabling energy self-sufficiency, with particular emphasis on decarbonisation. Based on a review of the literature and technical solutions, the characteristics have been classified and, emphasising the potential for integrating different technologies within microgrid structures, the role that microgrids and their users can play in the functioning of the energy system has been defined. Energy microgrids can be the pillar on which smart energy structures and smart grids, including energy systems using multiple energy carriers, will be based. Microgrids can guarantee energy self-sufficiency within their area of operation and support the entire energy system in this respect. Sensors that respond to both electrical and non-electrical quantities must play a special role in such structures, as they form the technical basis for the functioning of the smart energy sector. Full article

(This article belongs to the Special Issue Feature Papers in Physical Sensors 2025)

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