Special issue  

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.