In order to differentiate between a wet and a dry road surface, the water film height should be measured by using an infrared-based sensor system. By means of different wavelengths, it is also possible to distinguish between ice and water. In this article, a sensor system for the determination of the physical state of water on different surfaces using infrared LEDs and one photodiode is presented. This shall serve as a basis for the calculation of the road condition.
In this paper we investigate an in-line concept for continuous monitoring of sodium, potassium, calcium and urea concentrations in blood serum using ion-selective electrodes. This concept is evaluated in a preclinical study with human packed red blood cells as a test medium. It has been shown that the electrolytes can be well monitored. In addition, we present the first measurements with ion-sensitive field-effect transistors in a miniaturized sensor assembly using a novel readout electronics.
Detecting faults in bearings is indispensable for the maintenance of many industrial machines or components. The faults are detected by recognizing patterns in vibration data that are measured at the bearing housing. The method can be trained with data of variable revolution speeds, therefore reducing the effort for the acquisition of training data. Moreover, incipient faults can be detected before they cause severe damage to the equipment.
For the determination of the refractive index of the lubricant used in the sheet-bulk metal forming process, a lubricant thin-film thickness standard was developed which represents a continuous measuring range from 6 to 100 μm. To determine the refractive index, the thin-film thickness standard was measured with a coaxial interferometric measurement system in various thickness ranges. The results show changing optical properties with increasing layer thickness.
Deep learning has become a state-of-the-art method in machine learning, with a broad range of successful applications. Our goal is to explore the benefits of deep learning techniques for computational optical form measurements. The research is based on solving a nonlinear inverse problem aimed at the reconstruction of optical topographies from given processed interferograms. A U-Net network structure is chosen and tested on a simulated database. The obtained results are promising.
Distributed fiber optic strain measurement based on Rayleigh scattering enables the monitoring of strain along the entire fiber length and the possibility of integration into material matrices. In this article, optical fibers were integrated into the concrete matrix of small prisms to measure the deformation by drying. In comparison with a reference measuring method, the losses of strain transfer were measured. The analysis shows a high correlation between the reference method and the fiber.
We present a work on gas sensors that can for example be used for the assessment of indoor air quality. These sensors suffer from deterioration by siloxanes, so we investigated these effects by a distinct operation mode and exposition to this gas that allows us to interpret different reactions on the sensor surface. We found that all processes on the sensor surface are slowed down by this treatment and a self-compensation by the evaluation of oxygen adsorption processes is likely to be found.
A completely new evaluation method for optical sensors is investigated in this paper. It originates from research that integrates optical sensors into radio-over-fibre networks. The laboratory-based experimental set-up is explained, and the findings are validated by a comparison to the conventional evaluation scheme. Finally, the work provides a detailed mathematical model to understand the implications of this new read-out method for practical applications.
The new concept of a unified pH scale can be used to compare acidities of different kinds of solvents and their mixtures. The aim of the work was to investigate the robustness of the measurement method with four commercially available glass electrodes for non-aqueous media in comparison with the rather specific type of cell used so far for this measurement. The measurement results in aqueous mixtures of ethanol show good agreement.
European EMPIR project MicroProbes aims to use large-cale tactile microprobes for contact resonance applications, an established measurement mode of atomic force microscopes (AFMs). Because of the size of these probes, some of the simplifications made for AFM probes are not applicable. This study presents a guide on how to systematically create a model that replicates the dynamic behavior of microprobes. The finished model is then verified by analyzing a series of measurements.
In a very specific way, this research paper shows how established systems – in this case a commercial soot sensor for the automotive sector – can be optimized by diving deep into the basic research. The approach here is to link macroscopic observations or signal behavior with processes taking place on the atomic level. Taking these fundamental processes into account, the sensor's specific response time could be shortened effectively by a change in operating strategy – without any design changes.
This article presents a classification concept based on deep learning as an additional optical test method for real-time visualization and analysis of electrical assemblies in the production environment. For this purpose, a neural convolutional network is used to identify the quality of the solder joint of surface-mounted chip components in the inspection images. The concept can be used to increase the detection performance of the solder joint inspection systems.
This paper introduces a new method to drastically reduce the anisotropic strain sensitivity of granular thin film strain gauges. As a result, these improved strain gauges produce a much higher sensor signal when used for force transducers with biaxial strain fields. This gauge type is also more advantageous for uniaxial stress measurements. The method is based on the creation of a certain topographic structure of the strain gauges; in our case, this was realized by a picosecond laser system.
Photoelasticity is considered a useful measurement tool for non-destructive and contactless determination of mechanical stresses or strains in the production of silicon wafers. In this work, a detailed derivation for the anisotropic stress-optic law is presented, and the corresponding stress-optical parameters are measured.
We present the metrological characterization and calibration of three different types of thermographic cameras for quantitative temperature measurement traceable to the International Temperature Scale (ITS-90). Relevant technical specifications are determined according to the requirements given in the series of Technical Directives VDI/VDE 5585. For the IETD and the NU, we also show how a significant improvement in the parameters can be achieved with the help of the data reference method.
To improve the energy efficiency of industrial processes, such as continuous steel casting, lab-scale experiments with liquid metals are performed. We present an ultrasound Doppler signal process for multiplane, high-frame-rate flow imaging. We achieve real-time operations with an efficient implementation in a field-programmable gate array (FPGA). We analyze the contributions to the uncertainty of the velocity measurement and relate it to its fundamental limit.
This paper covers the design study of a multicomponent transducer (MCT) for wind turbine test benches. The MCT will cover the characteristics of wind turbines in the power range of up to 6 MW. The motivation to develop a MCT such as this is to provide satisfying measurement accuracy of loads and moments for all 6 degrees of freedom in order to reduce the uncertainty in the traceability of the drive train behavior due to the applied loads.
The necessary reliability of wind turbine gearboxes increases the requirements for large gear measurements. However, standard measuring methods reach their limits for large gears with diameters > 1 m. Therefore a scalable optical gear measurement approach is presented. At first, simulation and experimental results prove the principle applicability of the measuring approach for small gear measurements. Geometric parameters of gears can be determined with a single-digit micrometer uncertainty.
Applications like air quality, fire detection and detection of explosives require selective and quantitative measurements in an ever-changing background of interfering gases. One main issue hindering the successful implementation of gas sensors in real-world applications is the lack of appropriate calibration procedures for advanced gas sensor systems. This article presents a calibration scheme for gas sensors based on gas profiles with unique randomized gas mixtures.
In this contribution, an inexpensive and robust impedimetric NOx sensor is presented. The impedance of a functional thick film depends selectively on the NOx concentration in the exhaust but shows a dependency on the oxygen concentration. Therefore, an additional temperature-independent resistive oxygen sensor structure was integrated on the same sensor platform. It serves not only to determine the oxygen concentration in the exhaust, but also to correct the oxygen dependency of the NOx sensor.
Traceably calibrated scanning Hall microscopy (SHM) is a versatile tool for the quantitative characterization of magnetic microstructures. To enable SHM with a resolution in the micrometer range under ambient conditions, two Hall sensor materials, gold and graphene, were investigated. A SHM setup utilizing a 5 μm gold Hall sensor was calibrated. The field sensitivity and the detailed uncertainty budget are discussed. The presented traceable calibration is validated by comparison to simulations.
A commercial solid electrolyte gas sensor of the type "Pt|YSZ|Pt, air" based on yttria-stabilized zirconia for colorimetric oxygen detection was operated in optimized dynamic electrochemical modes. Cyclic voltammetry and square-wave voltammetry were used for the detection of NO and O2 in N2 in the temperature range between 550 and 750 °C. Due to the differences of electrode kinetics of the single components it is possible to detect these redox active gases selectively and quasi-simultaneously.
In this paper, we present a tactile sensor based on the interaction of coils with a magnetic elastomer. The first experimental approach is sampling the sensor with indentations of constant depth at different positions. A mathematical model is used to reproduce the data. Afterwards, this model is applied to random indentations at the same depth. As a result, we provide conceptual proof for position determination in one direction as a basis for a refined sensor design and further model approaches.
This paper describes an optical sensor system based on the technique of laser speckle photometry (LSP) for the application of stress characterization and defect detection in ceramics. The purpose of the research is to develop an in-line inspection solution for the industrial field. The preliminary results show that the LSP technique has the potential to fulfill the task.
Symmetrical Pt | YSZ | Pt–NO gas sensors were produced with frit-containing and fritless Pt electrodes and fired between 950 and 1300 °C. The sensors were operated by pulsed polarization. With fritless pastes, the sensors responded significantly higher. The firing temperature affects the sensitivity only slightly. The low NO sensitivity of the frit-containing electrodes was attributed to a blocking effect at the triple-phase boundaries that inhibits the oxygen transport through the sensor.
The necessity to measure harmonic emissions between 2 and 150 kHz is outlined by several standard committees and electrical utilities. This paper presents a measurement system and its traceable characterization designed to acquire and analyze voltages up to 230 V and currents up to 100 A with harmonics up to 150 kHz that may occur in smart grids. The uncertainty estimation is carried out and described in detail for both the fundamental and suprahmarmonics components.
A miniaturized, field-applicable sensor system was developed for the measurement of low hydrogen (H2) concentrations in air. The sensor system is based on the application of a newly developed miniaturized coulometric detector with gas chromatographic (GC) pre-separation after injection. By optimizing all operational parameters, it was possible to conduct reproducible and 100 % selective H2 measurements with more than 90 % analyte turnover compared to Faraday's law.
In order to further increase the performance of neural networks in the field of optical quality assurance of soldered joints, a hierarchical classifier can be used instead of a single network. The global expansion of the classifier enables the inspection task to be distributed over several subnetworks, which results in higher accuracy. Since the individual sub-models only concentrate on the identification of certain characteristics, categorical problems can be solved more effectively.
Effective from 20 May 2019, the kilogram is now defined in terms of the numerical value of the Planck constant h. Replacing the artefact definition of the kilogram by a new one based on the mass of a particle, or the atomic mass constant mu, would have been preferable for ease of understanding, among other reasons. In this paper we will discuss some educational limitations of teaching to different audiences the new definition and corresponding realizations of the kilogram.
For safety, environmental and economic reasons, methane leak detection is one of the most requested tasks for gas measurement devices. This paper compares the performance of a laser-based optical and acoustical detection scheme at different wavelengths and laser types, respectively. This forms a good basis for further developments of methane leak detection devices or can help to choose the right configuration for a certain methane leak detection application.
The estimation of the six-degree-of-freedom position and orientation of an end effector is of high interest in industrial robotics. High precision and data rates are important requirements when choosing an adequate measurement system. In this work, a six-degree-of-freedom pose estimation setup based on laser multilateration is described together with the measurement principle and self-calibration strategies used in this setup. In an experimental setup, data rates of 200 Hz are achieved.
This paper deals with the electrical investigation of various sand mixtures used in foundries for mold and core production. It is possible to classify various molding sand mixtures reproducibly on the basis of their electrical characteristics. This knowledge can now be used to develop measurement systems for processes in the foundry industry and thus increase product quality. In addition, resources can be conserved, and functioning closed-loop systems can be integrated into foundry processes.
The selective catalytic reduction, an after-treatment method using diesel exhaust fluid (AdBlue), is needed to reduce the emissions of diesel combustion processes. It is crucial to monitor the diesel exhaust fluid. This article presents a platinum thin-film sensor using the 3-omega method to characterize the diesel exhaust fluid. The information about the concentration of urea in water can be extracted. The results show that this sensor can determine the urea content to within 1 % by weight.
Differential thermal analysis (DTA) was used to examine the effect of the particle size and morphology of Co3O4 on its thermal response under exposure to 1 % CH4. The DTA response results from the catalytic oxidation of methane. Co3O4 samples differing in particle size and morphology were produced by ball milling or were synthesized. The investigations performed with temperatures between 250 and 450 °C reveal that both particle size and shape have a considerable effect on thermal response.
The dose rate and spectral distribution of X-ray emissions from laser materials processing have been determined using a thermoluminescence detector (TLD)-based spectrometer. The penetration depth of the radiation into the spectrometer depends on its energy, so that the energy-resolved spectrum of the radiation can be calculated from the TLD dose values by means of mathematical methods (Bayesian deconvolution). The measurements are traceable to the SI.
A novel, low-cost measurement device for simultaneous high temperature measurements of the electrical conductivity and Hall coefficient has been developed. Simulations were used to design a suitable screen-printed planar platinum heating structure that generates temperatures of up to 600 °C. Simulations of the temperature distribution have been validated using thermal imaging. Measurements were compared with data from the literature to validate the functionality of the novel device.
NiCr-carbon thin-film strain gauges offer the outstanding characteristic of a very high strain sensitivity. This can be very advantageous for many high-precision mechanical sensors like load cells. A downside of sensors based on these NiCr-carbon strain gauges is a rather large creep error, meaning reversible signal deviations at a constant load. We present two applicable methods for adjustment of the creep error: a modification of the film composition and a modification of the strain transfer.
Ion-selective electrodes have been proven useful in water analysis. They are usually used as single-rod measuring chains in different designs, which are manufactured using precision mechanical manufacturing and assembling technologies. The paper describes a microsystem technology approach for the fabrication of miniaturized electrochemical sensors. Design, manufacture, and performance of the novel ceramic multilayer-based sensor array are presented in the paper using various examples.