Parasitic direct currents in our alternating-current power grid affect the operation of power transformers. In this work, we present a fiber-optic current sensor system designed for the long-term monitoring of such direct currents, especially those arising from solar activity. The sensor demonstrator allows remote data access and sensor operation and was deployed at an electrical substation. For the first time, we show measurements of such currents on single phases of the power grid.

This research investigates the use of Capacitive Micromachined Ultrasonic Transducers (CMUTs) for underwater object detection and mapping in shallow-water environments. Experiments demonstrated their ability to detect small objects ( up to 4mm in size) and accurately reconstruct complex 3D surfaces. The findings highlight their potential for high-resolution underwater applications, especially for those requiring economic, compact, portable solutions.

This research presents a capacitive displacement sensor concept, designed for integration into a pin array gripper. The design is optimised for additive manufacturing, offering new design possibilities and enabling the creation of fully additive manufactured pin grippers with integrated displacement sensors. A prototype sensor was fabricated using additive manufacturing, and experimental results confirm the simulations and the functionality of the fabricated sensor for different pin materials.

The paper outlines a do-it-yourself optical sensor system for measuring water colour that can be used in citizen science projects to engage laypersons in science. The automated optical sensor system uses a camera with a Raspberry Pi computer to determine water colour according to the Forel–Ule colour scale. The collected data can be shared to the EyeOnWater database and used to provide insight and knowledge for further research in the fields of limnology and oceanology.

This study demonstrates how integrating silicon mechanical sensors into composites enables the detection of internal structural variations and how this can find applications in process monitoring or structural health monitoring (SHM). It introduces a novel, minimally intrusive process for embedding sensors within composites by means of a substrate-free transfer technique. Temperature and strain effects are studied. The sensor exhibits high sensitivity and is able to detect a creep effect at the core of the composite.

More traffic leads to more accidents involving wildlife, especially on rural roadcuts through habitats. Solutions like wildlife bridges and fences are needed, but there is no comprehensive solution yet. We have developed a system to detect and assess wildlife, including deer. This technology can work at night and in fog as animals cross roads in poor visibility. Radar sensors and infrared cameras are our solution.

Bistability is a mechanical phenomenon resulting in two stable, switchable states similar to a light switch. Micromachined piezoelectric bistable loudspeakers can utilize this effect to generate ultrasonic pulses with substantial loudness for applications such as distance measurements. In this work, we study different aspects of such a micromachined ultrasonic loudspeaker and demonstrate that such a device is feasible for ranging applications.

We present an automated, contactless method to map thin film thickness and stress across microelectromechanical systems (MEMS) wafers. Using white light interferometry on cantilevers and step profiles, we extract both mean and gradient stress with orientation sensitivity. Applied to six thin films, the approach reveals process-dependent variations, offering a reliable tool for evaluating and comparing MEMS materials and fabrication methods.

While electronic noses are designed to detect volatile organic compounds (VOCs) in complex odors, materials within sampling chambers and lines can emit their own gases, altering sensor responses. Our study confirmed that silicone and 3D-printed resin release compounds that poison sensors and reduce life span. In contrast, polyetheretherketone (PEEK) is a stable material that does not cause poisoning. Understanding these effects is crucial for designing reliable gas sensing platforms, ensuring accurate gas detection in different applications.

In this article we present a new method to measure the flow of a gas by means of ultrasound waves. Instead of sending pulses across the cross-section of the pipe, we make ultrasound travel along the length of the pipe. In other words, the pipe becomes an acoustic waveguide. This has the advantage that the travelling distance can become much longer, and so the measurement of the transit time becomes more sensitive to changes in the flow or the speed of sound.

The concept of an innovative energy harvester that could combine piezoelectric and reverse electrowetting-on-dielectric (REWOD) techniques is presented. By harnessing biomechanical vibrations from the cardiovascular system with piezoelectricity and a REWOD unit, the overall power output of the harvester was enhanced. This contributes to the advancement of self-powered, sustainable, wearable biosensors, enabling seamless and continuous data acquisition without relying on external batteries.

This research improves the performance of microbridge resonators for various applications, including gas sensing. By strategically designing the bottom electrode size relative to the microbridge length while keeping all other design parameters constant, the required operating voltage is reduced without compromising performance. Advanced modelling and experimental results demonstrate a 16 % reduction in operating voltage. These findings enhance resonator efficiency across diverse applications.

Automation in measurement tracking improves quality management by reducing human interaction and manual data risks. To enable this, all metrological and administrative data in quality certificates must be machine-readable. Digital calibration certificates (DCCs) meet this need and enable fully automated compliance checks. A temperature-monitoring demonstrator illustrates their automation potential. Its code is published for reuse.

This article presents first results from our research on the improvement of post-consumer recycled plastics in a suitable measurement situation on the compounding extruder, where the material is molten and by-products are removed by a vacuum. An extraction system was implemented, and samples were analyzed with laboratory methods. The results give insight into occurring substances and show the feasibility of the technique. Guidelines for an online sampling and monitoring system are derived.

Humans continue to use various units of measurement that are outside the internationally accepted System of Units (SI). This creates confusion that machines are unable to overcome. In the future, machines and sensor systems feeding data to those machines are expected to operate exclusively using the SI. This requires an internationally authoritative database for converting the non-SI units that humans enter to SI units at the level of the human–machine interface or human–sensor interface.

Scanning electron microscopy (SEM) and atomic force microscopy (AFM) enable sub-nanometer surface imaging and complement each other's limitations. Integrating AFM into a SEM vacuum chamber combines their strengths. However, vacuum increases the cantilever's Q factor and reduces scan speed. We develop a feedback circuit and a piezoelectric MEMS cantilever to tune the Q factor, enabling vacuum AFM at air-like speeds.

We developed a simple and versatile sensor that can detect harmful substances more effectively. By improving how the sensor's key component, the membrane, is made, we matched it better with the materials used to capture target chemicals. This makes the sensor easier to build and more reliable. Our work shows how choosing the right membrane material can greatly improve performance, opening the way for broader applications in detecting pollutants.

This paper is related to a theoretical background and the performance testing of lateral position sensing based on quadrature spatio-temporal modulation with adaptive parameter correction, implemented in a prototype micropower optical position sensor. There is a substantial improvement in position readout accuracy over a basic detection method (0.2 mm for sensing gaps >100 mm), and elevated tolerance to harsh field conditions (e.g. partial blockage in optical paths) has been demonstrated. 

We present an eight-channel evaluation board for ultrasound sonography and photoacoustic imaging. High frame rates enable averaging, improving signal-to-noise ratio. The board integrates a programmable preamplifier and an analog front-end with 12-bit analog-to-digital conversion, with data transmitted via Ethernet for PC evaluation. Gain distribution and its effect on signal-to-noise ratio in a multichannel photoacoustic receive chain are quantitatively characterized at 540 frames per second.

This article describes the determination of ferrite and austenite proportions in the weld zone of duplex steels using image processing and neural networks. These proportions allow conclusions to be drawn about the quality of the weld. For this purpose, neural networks of different architectures were applied to various image data configurations of metallography images. Depending on the architecture and application of the networks, error rates of 2 % to 3 % were achieved, which met expectations.

The size-of-source effect (SSE) is a systematic error requiring slow labor-intensive measurements. We propose a continuous approach using an iris diaphragm. Our method matched the accuracy of the traditional discrete method while providing more data and a reduction in measurement time. The method has no significant sensitivity to frame rate changes. Transient responses were observed using a neutral density filter, raising questions on how to measure and correct SSE in such configurations.

A non-contact, optical methodology suitable for high temperatures based on laser-Doppler vibrometry is presented to directly determine piezoelectric constants. LiTaO₃ is chosen as a model material as it is a representative piezoelectric material with applications in sensors and surface acoustic wave devices. The values determined range from 12 pm V^-1 at 21 °C to about 15 pm V^-1 at 400 °C, being in good agreement with the literature. Thus, the proof of concept for this approach has been obtained.

Methane plays an important role in global warming, and tracing its sources requires precise analysis of its isotopic fingerprint. In this study, we demonstrate the foundation of a system based on optical feedback cavity-enhanced absorption spectroscopy that achieves the stability needed for accurate isotope measurements. This work shows the potential of the method for future climate studies and environmental monitoring.

We present a 3D gas schlieren imaging sensor (3D-GSIS) for reconstructing vehicle exhaust plume density fields. It estimates plume size, laser absorption path lengths, intersection points of lasers, and local densities. Combined with advanced remote emission sensing, it enables direct measurement of pollutant concentrations in exhaust plumes.

Thin-film multilayers deposited on a wafer induce bending due to residual and thermal stresses that strongly depend on process conditions. The resulting curvature can be measured optically. We present a closed-form analytical model that relates the measured curvature to the residual stresses in individual layers. Using a small set of curvature measurements, layer-resolved residual stresses can be extracted without resource-intensive finite-element model simulations.