Special issue  

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 novel method for the detection of short pulses of gas at very low concentrations is presented. Applying the method to a doped SnO2 detector, gas pulses down to a dosage of 1 ppb times seconds can be detected. The gas transport inside the detector is simulated using the finite element method (FEM) to optimize the gas transport and to keep response and recovery time as short as possible. With this approach, we have demonstrated a detection limit for ethanol below 47 fg.

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.

Some results of the solid-state hydrogen peroxide vapor sensors made from semiconductor doped metal oxide nanostructured films have been presented during the international conference in Nuremberg. In this paper the extended version of our investigations of the detectors of hydrogen peroxide vapors are presented. The prepared sensors exhibit a response to very low concentration of hydrogen peroxide vapors. These detectors can be used in medicine, pharmacology, food and the textile industry.

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.

We prepared BaFe_(1-x)-0.01Al_0.01Ta_xO_3-δ (BFATx) thick films with x between 0.1 and 0.4 at room temperature using the aerosol deposition method and we measured Seebeck coefficients and conductivities between 600 and 800 °C at different oxygen concentrations. Deposited on a transducer that includes a heater, equipotential layers, and electrode structures, a dual thermoelectric–resistive oxygen sensor with almost temperature-independent characteristics of both measurands was realized using BFAT30.

In structural parts under vibrational loading fatigue cracks can initiate and grow, which can lead to structural failure. Conventional non-destructive testing methods for crack detection provide just a snapshot of fatigue crack evolution, whereas crack luminescence coating realizes clear visibility of the entire crack formation. Fatigue causing cyclic tensile tests and examinations on special test bodies allowing control of the crack opening width demonstrate a high sensitivity of the coating.

For detection of benzene, a multichannel gas sensor system was tested in two different laboratories at the concentration range from 0.5 ppb up to 10 ppb. A model is used to extract the channels and multilinear regression is done to compensate cross interference to other gases. Depending on the measurement conditions, the quantification accuracy is between ±0.2 ppb and ±2 ppb. Regression models for one laboratory were transferable between the labs under comparable measurement conditions.

The paper reviews the principles and applications of high-resolution ultrasonic spectroscopy in real-time, non-destructive analysis of molecular transformations, including transitions in polymers, ligand binding, self-assembly, crystallisation, gelation, phase diagrams, monitoring of chemical and biochemical reactions. High precision and useful capabilities of this technique enable its application in a broad range of systems, where other methods often fail or have high analytical cost.

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.

Current additive manufacturing allows for the implementation of electrically integrated 3-D printed sensors. In this contribution various technologies, sensing principles and applications are discussed. We will give both an overview of some of the sensors presented in literature as well as some of our own work on recent 3-D printed sensors.

A test method for narrowband wireless sensor/actuator networks is presented, facilitating affordable and efficient performance and compliance tests. Employing frequency/time division multiple access (F/TDMA) techniques and protocol synchronization, the complexity can siginificantly be reduced. Thus, complete communication testing becomes technically feasible and affordable.

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.

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.

In the context of the Industry 4.0 initiative, Cyber-Physical Production Systems (CPPS) or Cyber Manufacturing Systems (CMS) can be characterized as advanced networked mechatronic production systems gaining their added value by interaction with the ambient Industrial Internet of Things (IIoT). In this context IO-Link is one of the actual communication standards. This article presents IO-Link Wireless as the wireless extension to IO-Link.

A systematic investigation of a split-ring resonator for application as a biosensor is presented. The parameters responsible for the sensitivity of the setup were determined using a new approach to determine the resonance frequency depending on the relative permittivity of the sample. Based on these parameters, the resonator structure was optimized. Subsequently, a split-ring resonator was functionalized with aptamers and a selective detection of CRP could be shown.

Optical temperature sensors offer unique features which make them indispensable for key industries such as the energy sector. However, commercially available systems are designed to perform either distributed or hot spot temperature measurements. We have combined two measurement concepts to overcome this limitation, which allow distributed temperature measurements to be performed simultaneously with read-outs of optical hot spot temperature sensors at distinct positions along a fiber.

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.

Monitoring hydrocarbon concentrations in automotive exhausts is affected by flow rate changes. The signal of thermoelectric gas sensors is a thermovoltage. Its origin is a temperature difference that depends on the flow rate. To avoid this noise effect, the sensor can be installed in a defined bypass position. As shown by simulation and experiments, the gas flow around the sensor is almost turbulence-free and the signal only depends on the hydrocarbon concentration and not on the flow rate.

Temperature measurement in engine and exhaust systems is necessary for thermal protection of parts and optimizing the combustion process. The basic idea of this novel sensor concept is to use thick-film technology on component surfaces. Different standardized and especially nonstandard material combinations have been produced for validation of this concept. Application-oriented measurements took place in the exhaust system of a test vehicle and were compared to standard laboratory conditions.

In this paper, we have investigated ruthenated MWCNTs/SnO2 thick-film nanocomposite sensors in the presence of propylene glycol (PG), dimethylformamide (DMF) and formaldehyde (FA) vapors in the air. The minimal PG, DMF and FA gas concentrations at which the perceptible signal is registered are 13, 5 and 115 ppm, respectively. The optimal results are shown at 200 °C operating temperature. Dependence of the response on gas concentration is linear in all cases.

The degree of cross-linking and curing is an important value concerning the quality of cross-linked polyethylene (PE-X) and the functionality of adhesives and resin-based components. During this work the possibility of using single-sided NMR for the determination of this value in a non-destructive and much faster way than with the time-consuming standard laboratory measurements was shown. In addition, the usability of the measurement method for process quality control was investigated.

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.

A planar thermoelectric gas sensor is modeled. By coupling all influences (fluid flow, gas diffusion, heat transfer, chemical reactions, and electrical properties) a model was set up that mirrors the sensor behavior precisely, as the comparison with experimental data shows. The coupling of 3-D and 1-D geometry enables to calculate the temperature distribution, fluid flow, and the gas concentration distribution in the 3-D model, while the chemical reactions are very accurately calculated in 1-D.

This paper focuses on a novel carbon fibre sensor technology that exploits the low-cost and low-energy electrical reflectometry method for a spatially resolved strain measurement. The application of artificial neural networks for mapping the measured electrical signal to the existing strain profile is demonstrated. The potential and current limits are highlighted. The sensor is a promising part for the next generation of light-weight structures with operando health monitoring systems.

Electron capture detectors (ECDs) are widely used for the detection of electron affine substances such as pesticides or chlorofluorocarbons. In this work we present a new non-radioactive ECD and investigate the analytical performance depending on the operating parameters. We achieved limits of detection for 1,1,2-trichloroethane and sevoflurane, which are comparable to radioactive ECDs. Furthermore, a pulsed collector voltage mode was implemented, leading to an extended linear range.