Electrical impedance spectroscopy, in which a sine-wave test voltage or current is applied to the sample under test to measure its impedance over a suitable frequency range, is a powerful technique to investigate the electrical properties of a large variety of materials. This paper presents an updated review of EIS main applications such as measure of bacterial concentration, analysis of human body composition and characterization of food products, as well as other non-biological applications.
“Industrie 4.0” or the Industrial Internet of Things (IIoT) describe the current (r)evolution in industrial automation and control. This is fundamentally based on smart sensors, which generate data and allow further functionality from self-monitoring and self-configuration to condition monitoring of complex processes. The paper reviews the development of sensor technology over the last 2 centuries and highlights some of the potential that can be achieved with smart sensors and data analysis.
This work presents a novel design of a low power high-temperature MEMS elliptical capacitive pressure sensor that can be utilized within wireless sensor systems, e.g. TPMS. Throughout numerical and analytical analysis, it was found that sensor sensitivity and temperature resistance could be increased if the diaphragm area has two symmetrical segments of chords parallel to the major axis removed, and if diaphragm deformation increases the separation distance between the sensing capacitor plates.
The basis of our work presented in this paper stems from the research on new materials, especially temperature-stable thin films that transform strain into a resistance change very effectively, allowing higher sensitivity and higher operating temperatures. Different sensor concepts for time-resolved cylinder pressure monitoring of combustion engines are realized and evaluated. Reliable sensors with a minimum of internal components are provided.
Traceable wind velocity measurements with high resolution play a critical role in the field of wind energy. In this article we present a novel bistatic wind lidar system that has a high spatial and temporal resolution and a reduced measurement uncertainty compared to conventional systems as evidenced by comparison measurements. A first validation measurement in a wind tunnel with a laser Doppler anemometer as a flow velocity reference confirms the high accuracy of the bistatic lidar system.
We compared the temperature, relative humidity, total volatile organic compounds, carbon dioxide equivalents, and fine particulate matter measurements from Foobot to highly accurate instruments. The results suggest that Foobot offers a relatively low-cost and straightforward solution for identifying high pollutant exposures with potential health risks and for providing data at high granularity. Foobot characteristics make it a useful tool to evaluate occupant pollutant exposure.
An approach for detecting hazardous volatile organic compounds (VOCs) in ppb and sub-ppb concentrations is presented. Using metal oxide semiconductor (MOS) gas sensors in temperature cycled operation, VOCs in trace concentrations are successfully identified against a varying ethanol background of up to 2 ppm. For signal processing, linear discriminant analysis is applied to single sensor data and sensor fusion data. Integrated gas sensor systems using the same MOS sensors were characterized.
We present in our paper two types of optical sensors that are capable of measuring the environmentally significant gases such as carbon oxide and dioxide as well as methane and water through absorption of light even in harsh environments of high temperature and pressure. Thus the sensors render it possible to measure inside combustion engines or in civilian fireplaces, which is necessary to meet the increasing demands of environmental protection regulations.
A planar resonant radio-frequency gas sensor was equipped with an integrated heater. By simulative geometry optimization it now can be operated up to 700 °C. Sensitive materials with gas-dependent dielectric properties at higher temperatures can now be used. By coating the sensor with zeolite, ammonia could be detected. Depending on the working temperature, the sensor returns either a dosimeter signal (low temperatures) or a gas-concentration-dependent radio-frequency signal (high temperatures).
Strategic considerations and publications dealing with the future of industrial production are significantly influenced these days by the concept of "Industrie 4.0". For this reason the field of measurement technology for industrial production must also tackle this concept when thinking about future trends and challenges in metrology.
To determine the efficiency of multi-MW wind turbines, the torque measurement in wind turbine test benches has to be performed with a high accuracy. To this end, the torque measurement has to be traced to national standards. This can be done by using a novel torque transfer standard in combination with a newly developed torque calibration procedure under constant rotation. The calibration procedure was performed on a wind turbine test bench.
In this contribution a multi-sensor measuring system is presented. With this measurement system comparative measurements using five different surface measurement sensors are performed under identical conditions in a single set-up. The presented measurement results show different transfer behaviour of each sensor and indicate unique advantages for tactile and optical sensors. Comparative measuring enables the investigation of measurement deviations and helps to improve appropriate techniques.
In this work, genetically modified cells of the yeast Saccharomyces cerevisiae BY4741 were confined in a four-chamber microfluidic cell, providing an optical monitoring of the cell behaviour and their supply with the nutrients. The measurements of the time-dependent fluorescence intensity were performed with different concentrations of the drug diclofenac, and the sensitivity of yeast cells to diclofenac was demonstrated. Cell viability was monitored by simultaneous impedance recording.
This paper examines the new study of hand orientation as a substitute for computer-mouse movement and is evaluated based on ISO/TS 9241 part 411:Ergonomics of human–system interaction. Two pairs of hand-orientation candidates were evaluated, pitch–roll and pitch–yaw, to substitute up–down and left–right mouse-cursor movements. The empirical findings in this study provide a new suggestion for a suitable level of difficulty when using an inertial sensor to emulate the movement of a mouse cursor.
Fluorescence spectroscopy represents a very sensitive method, but fluorescence sensors are mainly used in academia and rarely in industrial processes. In this work, we present a newly developed functional model of an online fluorescence sensor. The sensor was miniaturised and constructed without any movable parts to detect important biologic fluorophores. Its performance was evaluated by calibration curves and selectivity tests and it was used for a biomass prediction of E. coli cultivations.
The measurement of humidity in industrial applications is still an important research issue. Especially under rough operation conditions the current humidity sensor comes to its limitations. To this end, we are developing an integrated sensor system using a metal oxide sensor with impedance spectroscopy as multi-signal generation allowing the discrimination of humidity and reducing gases. The submitted paper focuses on the modeling of the humidity-dependent aspects of impedance.
The climate conditions in underground transportation facilities, especially the current airflow in terms of direction and speed, are the key factor driving smoke propagation in the case of a tunnel fire. Sensing this airflow is cost-intensive. Therefore, this paper focuses on gaining the information from temperature sensing along the tunnels using already installed optical fibers normally used for communications. This technique can replace thousands of temperature sensors.
Future vehicle safety systems based on forward-looking sensors require a very robust validation system. This study describes such a validation sensor system and an algorithm to trigger safety systems in a crash. The presented sensor concept can detect the first contact and estimate the position of impact and the overlap in the initial few milliseconds of crash. The results highlight the temporal advantage of such a sensor over the present systems.
We focus on the implementation of monitoring algorithms for the induction machine in WSNs. As there are restrictions on the sensor node, such as low cost, low power, weak calculation and small memory size, the algorithm should be simple and efficient. The model-based method is used for the temperature estimation algorithm development. The experiments prove that the KF algorithm implementation is suitable for real-time temperature estimation on a wireless sensor node.
Millimetre-wave radar is an emerging technique for non-destructive testing: it is less costly than X-rays and has no ionizing radiation. Compared to ultrasound it does not require the device under test to be immersed in water. This article presents methods for high-resolution millimetre-wave radar imaging without a priori knowledge of the object's shape. A polymer device with simulated material defects is examined, which could be depicted precisely.
Soft pressure sensors fabricated by means of carbon-based material and polymers have the potential to sense pressure starting from 2 g to 18 kg. Such pressure sensors also exhibit high sensitivity, high durability, easy integration and long-term stability. These sensors can be integrated into robotic parts like fingers and feet to monitor the grasping force and the gait of the robot respectively.
Images of an infrared camera show blurring effects while recording a moving object. Not only the contrast is corrupted by the motion but also the object temperature seems to be lower. It is shown how such images and the true temperature with a good approximation can be restored. Since the detection mechanism of an infrared camera is different from usual digital cameras, also the restoration is different. Examples are presented for motion deblurring used to restore images with different motions.
Reliable detection of hydrocarbons can be achieved with a flame ionization detector (FID). However, these devices have not been implemented as true field devices yet. Miniaturization by using ceramic multilayer technology leads to a strong reduction of gas consumption and allows autonomous operation of the FID with gas supply by electrolysis. Thus, this research enables the use of the FID in the field. Characterization of this new FID reveals a performance comparable to conventional FIDs.
This paper presents an explosion-proof two-channel Raman photometer designed for chemical process monitoring in hazardous explosive atmospheres. Due to its design, alignment of components is simplified and economic in comparison to spectrometer systems. The described embedded sensor is ideally suited as a process analytical technology (PAT) tool for applications in environments with limitations on power input.
In this article we have investigated how the arbitrary orientation of a passive localization object in a magnetic field affects that field. For that we have identified the two sources of uncertainty, the geometrical extent of the object and the field inhomogeneity, and have quantified their effect analytically. Based on that we have compared the performance of several localization algorithms on that field variation. Results show that a dipole model is sufficient for the localization algorithm.
Predictions about systems too complex for physical modeling can be made nowadays with data-based models. Our software DAV³E is an easy way to extract relevant features from cyclic raw data, a process often neglected in other software packages, based on mathematical methods, incomplete physical models, or human intuition. Its graphical user interface further provides methods to fuse data from many sensors, to teach a model the prediction of new data, and to check the model’s performance.
We assessed the applicability of bacterial surface layer proteins of Lysinibacillus sphaericus JG-B53 and Sporosarcina ureae ATCC 13881 for the detection of metal ions in water. Based on the interactions of the cell components with metal complexes, two potential sensor systems, one colorimetric with functionalized gold nanoparticles and the other using a regenerative sensor layer, were developed. The systems' detection limits of YCl3 in water were 1.67 x 10−5 and 1 x 10−4 mol L−1, respectively.
Reverberation chambers are well-proven test environments for RF measurements. Typically, mean values are taken from the measurements to characterize the equipment under test. In the novel approach presented in this paper, the correlation of measured sample sequences is utilized to detect deviations, in particular of the radiation characteristics, from reference equipment.
Virtual experiments have become an indispensable tool for the design and the accuracy assessment of novel measurement procedures and instruments. In this paper, we present SimOptDevice, a library for opto-mechanical virtual experiments. We describe the mathematical tools used for solving the related numerical tasks and give examples of application scenarios.
We combine two modern trends in component fabrication, namely, the integration of sensors into machine parts and the 3-D-printing technology, which is rapidly emerging in the fabrication of standardized and customized components and prototypes. We present a 3-D-printed ‘smart’ screw with an integrated strain gauge. The signal of the sensor can be used to monitor the fastening process of the screw as well as the reduction in strength of the screw joint over time.
An advanced-material-based thin, flexible sensor mat has been synthesized to record and visualize both the position and pressure of applied load. Such a pressure measurement system bears great potential in human health monitoring applications like long-term patient monitoring mattresses or insoles for gait monitoring.
A method for amplitude–phase calibration of tri-axial accelerometers in the low-frequency range is proposed, based on a linear slide, used to excite all the axes of the accelerometer at the same time, and a laser Doppler vibrometer (LDV) as a reference. Results show that the phase is a critical aspect to consider in calibration, more than the amplitude, and the comparison with the theoretical model is useful to verify the hypotheses. Different behaviours result, depending on the measuring chain.
The analysis of aeroacoustic phenomena is crucial for deeper understanding of the damping mechanisms of a sound-absorbing bias flow liner. Simultaneous three-component velocity measurements of the superposed sound field and the flow field in a 3-D region of interest with over 4000 measurement points are presented. The natural Helmholtz–Hodge decomposition is applied to separate both fields from the measured velocity field in the spatial domain. This reveals new insight into the aerodynamic flow.
Cadmium is one of heavy metals that can cause serious health complications if humans are excessively exposed. This research was conducted to detect the amount of cadmium inside herbal plants using a new sensor modified with graphene and ionic liquid. The amount of cadmium inside herbs A, D, M and C were 0.0035, 0.0237, 0.0267 and 0.0251 milligrams/litre, respectively. The results showed that the herbs were safe to be consumed. The developed sensor was comparable to existing detection methods.
An original platform embedding multiple sensors and an energy harvesting unit is described. It is versatile and requires little or no maintenance. Multiple platforms can be connected to a hub device in a wireless sensor network. Emphasis was put on the reduction of power consumption and on the energy harvesting unit. With the addition of a small solar panel the system can be fully autonomous indoors. Characterization of power consumption and a test in real-world operation are presented.
Computed tomography measurements can be subject to specific image artefacts, which can be dependent on the effective rotation axis of the work piece during the scan. The presented approach is to combine several CT scans with different rotation axes of the work piece using a data fusion approach. To improve the fidelity of the result, surface points are weighted individually within the algorithm, dependent on the local surface quality of the measurement.
Many applications in high-voltage environments require electrically isolated sensors. We demonstrate a purely optical sensor link using only low-cost high-brightness LEDs and only one polymer optical fiber (POF) for remote powering of isolated electronic sensor nodes of as well as for data transmission of sensor data to a central unit. No optical couplers or special photo diodes are required, to save costs and reduce size. This enables us to install sensor networks in the field with low effort.
Wood-log- and wood-chip-fuelled low-power combustion systems emit high amounts of uncombusted gaseous components like CO and particulate matter. Emissions can be effectively reduced by optimized combustion process control using high-temperature gas sensors. The sensing behaviour of gas sensors for continuous analysis of uncombusted components and their long-term stability have been studied. The sensor signals are used to improve the combustion process control and to monitor combustion quality.