We present a fully telemetric sensor concept for angle and position measurement. It is based on single-layer millimeter-wave metamaterials that exhibit an anisotropic resonant behavior in interaction with incident electromagnetic waves. The angle of rotation is determined from the reflected millimeter waves of the metamaterial target using a millimeter wave chip transceiver. We use a metamaterial geometry exhibiting anisotropic Fano-type resonant behavior. The Fano-type resonance shows a distinct minimum in the reflection spectrum, even with a single layer of metamaterial. The metamaterial target is manufactured on a printed circuit board (PCB) laminate with low-cost standard manufacturing methods. We present an analytical model estimating the resonance frequency of the metamaterial used. The model allows us to assess whether with the Fano-type metamaterial unit cell structure resonance frequencies in the millimeter wave regime are achievable and compliant with standard PCB manufacturing design rules. We performed proof-of-principle experiments with the metamaterial targets and a vector network analyzer, assisted by a detailed analysis of the sensor effect by means of finite-element method calculations. Finally, we implemented a demonstrator setup containing a state-of-the-art frequency-modulated continuous-wave (FMCW) radar chip and a metamaterial target manufactured with standard PCB manufacturing processes.
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. This leads to a reconsideration of the status of the non-SI units accepted for use with the SI. Here, the case of the non-SI units dalton (Da), neper (Np), bel (B) and decibel (dB) is considered.
The condition monitoring of the health status of lubricating greases used in axle box bearings can be realized by applying well-established electrical or optical measurement principles. Furthermore, some novel methods have been reported that make use of humidity sensors or of dielectric thermoscopy. One of the most important grease condition parameters is the water content of the lubricating grease, as water can degrade grease to the point that it is no longer able to provide suitable lubrication and can also damage the bearing due to corrosion and cavitation. In this study, a new approach for water detection in lubricated wagon components is presented that is based on commercially available humidity sensors. The core element of this sensor system is a robust humidity sensor mounted in the immediate atmosphere of the grease-lubricated wagon axle bearing. In the case of water intake, the humidity of the gaseous atmosphere above the grease increases and can be detected by the customized sensor concept Humidity Sensor in Axle Bearings (HSAB). As this sensor system has to be sufficiently robust, it must be able to withstand environmental impact factors. The most important of these factors are temperature, relative humidity, and mechanical load, like vibrations and shocks, depending on the relevant railway application. To mimic these field effects under controlled laboratory conditions, the “lab-to-field” approach was set up and employed. Of the utmost importance was the installation of a development environment for the sensors that enabled the transfer of laboratory results to the respective rail field application. As a result, the HSAB system shows promise with respect to enhancing the reliability of railway wagons and decreasing maintenance costs, thereby reducing the downtime of railway wagons significantly.
Phase-measuring deflectometry (PMD) with active display registration (ADR) is a ray-optics-based technique for the shape measurement of specular surfaces. To obtain quantitative results, the relative position of the cameras of the PMD–ADR setup needs to be determined by geometric calibration. Geometric calibration can be performed by inserting a planar mirror into the setup that brings all camera fields of view to overlap on an active pattern display. The mirror is tilted to multiple positions and each time the cameras capture the displayed images, which yields sufficient data to obtain the relative camera positions and the positions of the mirror. In this article, we give a more detailed description of PMD–ADR and its calibration. We also implement a laser-tracker-based reference method to measure the mirror positions and use its result to expose systematic errors in the geometric calibration.
Most applications which measure physical quantities, especially in harsh environments, rely on surface acoustic wave resonators (SAWRs). Measuring the variation of the resonance frequency is a fundamental step in such cases. This article presents a comparison between three techniques for best determining the resonance frequency in one shot from the point of accuracy and uncertainty: fast Fourier transform (FFT), discrete wavelet transform (DWT) and empirical mode decomposition (EMD). After proposing a model for the generation of synthetic SAW signals, the question of wavelet choice is answered. The three techniques are applied to synthetic signals with different central frequencies and signal-to-noise ratios (SNRs). They are also tested on experimental signals with different sampling rates, number of samples and SNRs. Results are discussed in terms of the accuracy of the estimated frequency and measurement uncertainty. This study is successfully extended to SAWR temperature sensors.
Following tightened regulations, selective catalytic reduction (SCR) of nitrogen oxides (NOx) by ammonia (NH3) has over the last couple of decades found wider adoption as a means of reducing NOx3x2) and water (H2O) on the surface of a specific catalyst, the NH3x33x333The sensor's NH32), water vapour (H2O), nitric oxide (NO), nitrogen dioxide (NO2), carbon monoxide (CO), and a model hydrocarbon, ethene (C2H4) – were thereby investigated for relevant concentration ranges under controlled conditions in the laboratory. While, at the prescribed sensor operation temperature of 300 ∘C, the influence of H2O, CO, and C2H43323 
We developed a pin-type current probe with high sensitivity, targeting electrical-probing printed circuit boards (PCBs). The developed sensor showed good enough characteristics, with 1 mA resolution on current measurements and up to 1 MHz operating frequency for analyzing highly integrated PCBs. During its characterization, however, we experienced a monotonously varying output signal in the time range of a few tens of minutes. We modeled it as the thermal-offset drift, being caused by Joule heating during sensor operation, and showed several solutions for reducing the offset by modifying the planar Hall resistance (PHR) layout and electric operation conditions and applying sensor circuitry with pulse width modulation.
A possible way to reduce the size and complexity of common gas chromatography (GC) systems is the economization of the column temperature regulation system. To this end, a temperature compensation method was developed and validated on a benchtop GC-PDD (pulsed discharge detector) with ethene. An in-house-developed algorithm correlates the retention index of a test gas to the retention index of a previously selected reference gas. To investigate further methods of cost reduction, commercial gas sensors were tested as cheap, sensitive, and versatile detectors. Therefore, CO22-specific IR (infrared) sensor, was used to set up a simple GC system and to apply this method on test measurements. Sorption parameters for ethene and CO2S−11.982 J mol−1 K−1
The temperature-dependent properties of sensor films for measuring the concentration of various gas components affect, to a large extent, the sensor characteristics of planar gas sensors. Therefore, it is important to know the temperature distribution of the gas-sensitive films of such sensors precisely. Using screen-printed thermocouples and a thermal-imaging camera, two principles for determining the temperature profile of gas sensors inside of a protection cap are shown and compared in this study. The data agree well, and the results can be used in future to determine the influences of varying flow and temperature conditions on the temperature profile of a sensor and to reduce such effects by adapting the periphery, e.g., by designing appropriate protection caps.
Temperature measurement at the surface of solids by means of contact thermometers has its own metrological characteristics, which are in contrast to characteristics of the measurement with immersed contact thermometers. They significantly influence the accuracy and the measurement uncertainty of the measured temperature and its deviations. Up to now, no national or international guideline exists which deals with the determination of the static and dynamic measurement deviations. Therefore, the guideline committee “VDI/VDE-GMA FA 4.62 Contact Thermometry” has developed the new VDI (Association of German Engineers) and VDE (Association for Electrical, Electronic and Information Technologies) guideline 3520 “Surface temperature measurement with contact thermometers”. It contains information about the most important properties of contact surface thermometers and error sources, and it presents typical measurement results for various applications. In addition, the parameters influencing the measurement result and test equipment for their determination are described, and concrete examples of thermometer data sheets are given.
The paper provides synthetic indications regarding the measuring performances of procedures for using a robotic total station (RTS) in emergency situations, such as the survey of the structural conditions of buildings and the assessment of the safety level for rescue operations after the occurrence of an earthquake. Particular attention is paid to operative aspects that could impact on the performance of the system in this situation; specifically considered is the effect of the layout of the measurement setup and of the number of monitoring points, depending on the geometry of the site and of the considered buildings, because the criticality of emergency conditions imposes geometrical solutions which are far from having optimal solutions. The analysis is carried out with reference to two different buildings, which have different characteristics from the point of view of height and distance from the instrument, and that implies different geometrical constraints for the instrument during the acquisition of the monitoring points. The methodology allows the evaluation of the repeatability, reproducibility, and detection limit of a RTS, in field conditions, referring to a 1-year observation period, with reference to different quantities, like positions of the monitoring points and the inclination of walls and façades. In particular, the analysis of the geometrical characteristics of reduced configurations of the monitoring points has highlighted interesting aspects in view of defining a simplified procedure, which is also suitable for speeding up the acquisition of reliable data in emergency conditions.
In the research work presented here, an integrating sphere demonstrator which is suitable for the non-destructive determination of the degree of cross-linking or curing and has the potential for use as an at-line device for in-process quality assurance was assembled and explored. The measurement system allows the analysis of absorption and scattering coefficients of materials independently by means of absolute optical spectroscopy. The two optical parameters showed a good correlation with the degree of cross-linking of cross-linked polyethylene (PE-X) and the degree of curing of different thermosets and adhesives, each of which was determined using different reference methods (wet chemical analysis, differential scanning calorimetry (DSC), and dielectric analysis (DEA)). The results show that different PE-X materials can be distinguished well by their absorption and scattering in the visual (VIS) and near-infrared (NIR) wavelength range, respectively, and conclusions on their degree of cross-linking are possible. Also, the curing of resins can be monitored based on the absorption. In addition, Raman spectroscopy was used to achieve a better understanding of the material changes during the cross-linking of the materials. It also showed a good suitability for monitoring the curing processes in thermosets. In summary, the new method can be used to determine the crucial parameters of these industrial important material types and fulfils the great demand for fast, non-destructive testing, which can be carried out during the process or on the finished product.
An inverse measurement procedure for the determination of a full set of piezoelectric material parameters using a single sample is presented. The basis for the measurement procedure is a measurement of the frequency-dependent impedance of the sample. To yield sufficient sensitivity of this measurement with respect to all material parameters (mechanical, electrical, and coupling parameters), an optimal electrode configuration for the sample is determined before the inverse measurement procedure is realised using a novel topology optimisation approach. After initial estimates for the material parameters are provided by analytical expressions, a sensitivity-based, staged, local optimisation procedure yields material parameters for the sample by fitting the impedance of a finite element simulation model to the measured electrical impedance. Results for different absorption models as well as for different piezoelectric materials (hard, soft, and lead-free piezoceramics) are included.
A new approach to assess the emanation of 222Rn from 226Ra sources based on γ-ray spectrometric measurements is presented. While previous methods have resorted to steady-state treatment of the system, the method presented incorporates well-known radioactive decay kinetics into the inference procedure through the formulation of a theoretically motivated system model. The validity of the 222Rn emanation estimate is thereby extended to regimes of changing source behavior, potentially enabling the development of source surveillance systems in the future. The inference algorithms are based on approximate recursive Bayesian estimation in a switching linear dynamical system, allowing regimes of changing emanation to be identified from the spectral time series while providing reasonable filtering and smoothing performance in steady-state regimes. The derived method is applied to an empirical γ-ray spectrometric time series obtained over 85 d and is able to provide a time series of emanation estimates consistent with the physics of the emanation process.
Hydrogel sensors are well suited to measuring the concentration of substances in liquids, and, because the hydrogel is biocompatible, they are ideal for medical use. Hydrogels change their volume in response to stimuli. The larger the hydrogel, the more pronounced the measurement signal. However, a larger volume also leads to slower swelling due to the longer diffusion paths. One method of determining the degree of swelling is to measure the swelling pressure using a piezoresistive pressure sensor. With current approaches, measurement times of several minutes can be achieved. By exploiting the bimorph effect, we were able to reduce the thickness of the hydrogel and, thus, reduce the response time of the entire sensor to less than 1 min. The aim of this paper is now to show how a sensor with short response times can be designed and manufactured and, in particular, how to find a suitable hydrogel composition, how to appropriately structure the hydrogel layer and how a robust adhesion of the hydrogel to the sensor chip can be achieved. As a result, we were able to show that such hydrogel sensors with response times of just a few seconds are possible.
The food industry relies on various technical processes, from storing, freezing, thawing, and packaging to logistics. With the increasing population and the equational growth in food production, it is preferred to have increased automation in the food industry to reduce human labor. To provide an automated and green solution, it is required to monitor and control food-processing steps, such as thawing. This research aims to design an ultrasound-based setup that can monitor the pre-thawing state of food. A change in the signal by 20 %–27 % for herring fish and 60.7 % for chicken soup was obtained when monitored from a frozen state to a room-temperature state. Various other sample food products were tested, and related challenges and observations are discussed.
Infrared attenuated total reflection (ATR) spectroscopy is a common laboratory technique for the analysis of highly absorbing liquids and solids, and a variety of ATR accessories for laboratory FTIR spectrometers are available. However, ATR spectroscopy is rarely found in industrial processes, where compact, robust, and cost-effective sensors for continuous operation are required. Here, narrowband photometers are more appropriate than FTIR instruments. We show the concept and implementation of a compact Si-based ATR module with a four-channel microelectromechanical systems (MEMS) detector. Measurements of liquid mixtures demonstrate the suitability for applications in the chemical industry. Apart from sapphire (for wavelengths below 5 µm) and diamond (extending to the far-infrared region), most materials for ATR elements do not have either high enough infrared transmission or sufficient mechanical and chemical stability to be exposed to process fluids, abrasive components, or aggressive cleaning agents. However, using diamond coatings on Si improves the stability of the sensor surface. In addition, by proper choice of incidence angle and coating thickness, an enhancement of the ATR absorbance is theoretically expected and demonstrated by first experiments using a compact sensor module with a diamond-coated Si ATR element.
For taking most advantage of live or real-time sensor measurements, data have to be processed by a single or even by a chain of models on the fly, in contrast to earlier offline simulation solutions. This requirement can be best met by concepts developed under the general term “digital twin” (DT). The step from the Internet of Things (IoT) to a full exploitation of DT solutions entails new challenges but also provides new features, which we discuss based on our example DT solution for remote monitoring of fruit during ocean transportation. A crucial challenge is the transformation of models into an updateable format, necessary to keep the physical object and its modelled representation in sync. A basic new feature of DTs is new software solutions for easy and flexible linking of different models through a streaming platform by implementing an event-driven architecture. We demonstrate a solution for controlling model execution during multiple life cycle phases of the fruit as physical object. An evaluation of response times showed that server performance is sufficient to handle more than 100 DT instances per second.
Novel approaches for the design of assistive technology controls propose the usage of eye tracking devices such as for smart wheelchairs and robotic arms. The advantages of artificial feedback, especially vibrotactile feedback, as opposed to their use in prostheses, have not been sufficiently explored. Vibrotactile feedback reduces the cognitive load on the visual and auditory channel. It provides tactile sensation, resulting in better use of assistive technologies. In this study the impact of vibration on the precision and accuracy of a head-worn eye tracking device is investigated. The presented system is suitable for further research in the field of artificial feedback. Vibration was perceivable for all participants, yet it does not produce any significant deviations in precision and accuracy.
Exhaustive analysis of chemical measurements requires considerable expenditure of time and personnel. However, many aspects of this can be automated by translating manual work into objective algorithmic routines. To this end, we developed adaptable software for gas chromatography data and validated analysis steps using whisky samples. We employed an unspecific, larger, in-house volatile organic compound (VOC) database and another specifically curated database of 217 known whisky chemicals, to automate database-matching based on mass spectra and retention indices. We managed to reduce the amount of necessary interaction, facilitated complex analysis for the less experienced user, and showed that characteristic whisky components constituted the majority of detected molecules in all 16 analyzed samples. With this approach, we present a decisive contribution towards the automated assessment of aroma profiles in food.