Greenhouse gas emissions from freshwaters are not well quantified on a global scale. Our prototype monitors aqueous concentrations of CH₄ and CO₂ at relevant timescales. Our low-cost design allows the application of replicated sensors to capture spatial heterogeneity and temporal variability in dissolved gases in highly dynamic ecosystems, thereby addressing a major bottleneck in the reliable estimation of emissions. We provide a detailed prototype description and share software code.

A new method for water detection in lubricated rail components is presented. It is based on a robust humidity sensor combined with robust data evaluation to determine the water content of greases. Based on a laboratory evaluation in the relevant environment, the presented approach offers an online monitoring tool to predict the water content of grease-lubricated rail parts, thereby enhancing the reliability and safety while reducing the maintenance costs and downtime of railway wagons.

There is a need to develop an unambiguous digital version of the International System of Units (SI), as required for information systems and distributed sensor networks. The unit kilogram could already replace the non-SI unit for atomic masses (dalton, Da) because the experimental uncertainties are now very close. But changing the current status of the well-known unit decibel would require considerably more time, until a digital version of a Unique SI Reference Point would be approved.

Phase-measuring deflectometry is an optical shape measurement technique for reflective surfaces. The basic idea is that a pattern that is observed through reflection on a curved surface gets distorted and reveals information about its shape. In this work we describe a method to move the pattern to obtain data for quantitative shape determination. The experimental setup is calibrated. With a laser tracker we reveal calibration errors and discuss their influence on the reconstructed shape.

This paper presents a conceptual approach for enhancing the communications between different calibration systems in a calibration ecosystem and enabling data exchange based on the digital calibration certificate (DCC) using the Beamex calibration ecosystem as an example. The presented system architecture concept introduces data exchange and DCC services that would allow the exchange of calibration data between the Beamex ecosystem and third-party systems.

In power electronics, materials like silicon carbide (SiC) are increasingly being used instead of silicon. They have a lot of advantages but also require defect inspection with high accuracy. Different defect types on SiC samples are measured with various methods to determine which one is most suitable for which defect. In conclusion, each examined measurement method is sensitive to the studied defects, although they differ in speed and specialized application fields.

We present a concept for angle and position measurement based on metamaterials. The distance between the sensor and the rotating or moving metamaterial target is not limited to a precise value. We use state-of-the-art millimeter wave radar chip technology for read-out, initially intended for applications such as gesture recognition or contactless switches. We implement a demonstrator test setup and show the proof of principle.

Many applications which measure physical quantities rely on wireless surface acoustic wave sensors. The accuracy of this sensor depends directly on the measurement of its main frequency. This paper aims to compare three methods for this measurement in one shot: fast Fourier transform, discrete wavelet transform, and empirical mode decomposition. Results show that the choice of the method is conditioned by the disturbance level and that the wavelet method is the best way for harsh environments.

Our research introduces an innovative method to improve the quality control of plastic granules, crucial in industries like manufacturing and automotive. We addressed a common issue: identifying "burn marks" on granules caused by overheating during processing. By combining advanced machine learning and a novel data augmentation technique called "cutout", we significantly enhanced the detection accuracy of these defects.

This study concerns development and evaluation of a high-temperature-resilient ammonia sensor tailored for ammonia slip monitoring to improve NO_x and NH₃ emission reduction from coal-fuelled, biomass-fuelled, heat and power plants. In particular, by tuning the gas-sensitive materials' nanostructure, the interference from carbon monoxide in the ammonia measurement could be markedly reduced, thus allowing more accurate ammonia monitoring in the flue gas from a real combined heat and power plant.

Essential steps for the establishment of a data cycle were discussed, boundary conditions were defined and possible technological solutions for the achievement of the objective were presented. The subaspects mentioned are data generation, archiving, database extraction and reuse. A special focus was on the data format DICONDE, whose structuring and archiving techniques primarily address test data. In addition, two examples were presented in which this schema was implemented.

Interferometric form measurement methods display ambiguities between certain form errors and the misalignment of measurement specimens. In this work, we present a concept for improving the accuracy of the form measurement of aspheres and freeform surfaces with a tilted-wave interferometer by introducing absolute distance measurements using a white light interferometer. A description of the laboratory setup and the corresponding data analysis is given together with first distance measurements.

High levels of nitrate can cause negative effects on aquatic plants, fishes and human health. A simple, reusable and sensitive electrochemical sensor based on silver nanoparticles with a modified gold screen-printed electrode has been developed for the detection of nitrate in water.  The sensor exhibited good performances such as high sensitivity, reproducibility, repeatability and selectivity. The proposed approach was successfully used to determine nitrate in freshwater.

The presented approach allows users to perform measurements of microphone responses directly in the array using the internal hardware and so to characterize the whole signal chain of microphone–preamplifier–ADC. The measurements do not need special equipment and can be carried out in ordinary reverberant locations. A loudspeaker driven by a voltage pulse is used to produce a sound wave with a short first wavefront. Processing only this wavefront suppresses reflected waves that arrive later.

3D thermograms are a good alternative when a single traditional 2D thermal image does not reveal enough information to analyze a complex object. However, the 3D thermography field is still under exploration. This paper shows a comparison of a thermography system operated with two different 3D sensors. The results indicate that the depth sensor with more accurate measurements captures the object geometry better, and therefore the interpretation of the 3D thermograms is improved.

An airborne measurement system with an onboard computer for data processing and recording that does not require constant radio communication for inspection and maintenance is presented. It detects, locates, and quantifies methane leaks using a gimbal-mounted sensor. A model that correlates wind speed with drone attitude is presented and compared to measurements made with an anemometer. The quantification of methane emissions was evaluated in a laboratory setup and at an open-area test site.

This study introduces four sensors utilizing multiple fiber Bragg grating constellations embedded in a silicon dioxide single-mode fiber for simultaneous pressure, temperature, and bending curvature measurement. By varying grating constellation, dimensions, and materials, researchers optimized sensor performance. Results indicate that the optimal configuration involves a high cladding-to-coating ratio, less-stiff coating, and the combination of two gratings to form a Fabry–Pérot interferometer.

A very small, anharmonic but periodic signal is separated from a noise background that is orders of magnitude larger than the pure signal. The approach consists of a sequence of filters and transformations and is demonstrated on an interferometric measurement of the high-temperature chemical expansion of a thin film, containing heat haze, thermal length drift, and parasitic vibrations. The displacement is 38 % larger and the uncertainty 35 % lower than when evaluated with previous approaches.

The paper presents a concept for fabricating a biosensor with enhanced long-term stability and offers new options for designing photonics-based microsystems aimed at analysing biosamples. In order to couple the light used to probe samples, a grating is illuminated from the back side, thus realizing an inverted grating configuration. This offers the possibility of designing microsystems that can be operated more conveniently and with a much extended lifetime.

The purpose of our study is to demonstrate the detection of hydrogen in a mixture with natural gas by means of ultrasound measurements. In the coming years, hydrogen will be mixed with natural gas and distributed in the available gas pipeline network; therefore, monitoring the hydrogen content in real time becomes a necessity. We show the implementation of miniature ultrasound transducers (CMUTs) for this purpose by measuring the speed of sound of the mixture.

This article describes a small prototype sensor designed to sense carbon dioxide (CO₂) levels for indoor air quality monitoring. The device uses a photoacoustic detector fabricated using a wafer-bonding process. This allows for high-volume production of the sensors. The prototype presented is small in size and can detect CO₂ levels as low as 81 ppm with a response time of 53 s. Our results show suitability for application in indoor air quality control systems.

A human activity recognition (HAR) system carried by masseurs for controlling a therapy table via different movements of legs or hip was studied. This work starts with a survey on HAR systems using the sensor position "trouser pockets". Afterwards, in the experiments, the impacts of different parameters and configurations on the classification accuracy is examined to get a thorough understanding of the classification process.

The temperature dependence of the resonance frequency of quartz resonators can be used for thermal infrared sensors. The quartz chips must be very thin to obtain a good sensor signal. This work describes how to manufacture and package sensors with 5 µm thin chips. Different sensor layouts are ion beam etched; they influence the vibration of the resonators, which is shown by impedance measurements. The temperature coefficient of the resonance frequency is determined to be around 90 ppm K^-1.