Contactless Sensor Research Articles

Uric acid detection by using contactless intensity modulation based displacement sensor

A simple and contactless intensity modulated displacement sensor is proposed and demonstrated for sensing uric acid concentration. For a concentration change of uric acid from 0 ppm to 500 ppm, two peak voltages are obtained from the displacement curve correspond to the highest reflectivity of each concentration. Those peak light intensities increase linearly with the concentration due to the increase of the refractive index of the uric acid solution. This implies that the higher concentration of uric acid tends to detect a stronger signal. The measured sensitivities are obtained at 0.0015 V/ppm and 0.0016 V/ppm for the first peak voltage and second peak voltage respectively. The result showed the percentage of similarity for the first peak to the second peak is almost 94% and the linearity more than 97% for both peak voltages is obtained suggested the consistency of the sensor system. The stability and simplicity of the contactless sensor offer a good and valuable opportunity for many applications especially in the hazardous chemical, pharmaceutical, process control and diagnostic sectors.

Fusion of Wearable and Contactless Sensors for Intelligent Gesture Recognition

Fusion of Wearable and Contactless Sensors for Intelligent Gesture Recognition

Fusion of Wearable and Contactless Sensors for Intelligent Gesture Recognition

A novel approach of fusing datasets from multiple sensors using a hierarchical support vector machine (HSVM) algorithm is presented. The validation of this method is experimentally carried out using an intelligent learning system that combines two different data sources. The sensors are based on a contactless sensor, which is a radar that detects the movements of the hands and fingers, as well as a wearable sensor, which is a flexible pressure sensor array that measures pressure distribution around the wrist. A HSVM architecture is developed to effectively fuse different data types in terms of sampling rate, data format, and gesture information from the pressure sensors and radar. In this respect, the proposed method is compared with the classification results from each of the two sensors independently. Herein, datasets from 15 different participants are collected and analyzed. The results show that the radar on its own provides a mean classification accuracy of 76.7%, whereas the pressure sensors provide an accuracy of 69.0%. However, enhancing the pressure sensors' output results with radar using the proposed HSVM algorithm improves the classification accuracy to 92.5%.

Reduced sleep efficiency, measured using an objective device, was related to an increased prevalence of home hypertension in Japanese adults

Few studies have reported the relationship between reduced sleep efficiency and the prevalence of hypertension independent of sleep duration in Japan. This study aimed to evaluate whether reduced sleep efficiency, measured using an objective device for >1 week, was related to an increased prevalence of hypertension independent of sleep duration in the general Japanese population. We conducted a cross-sectional study of 904 participants aged ≥20 years who lived in Miyagi Prefecture, Japan. Sleep efficiency was measured using a contactless biomotion sleep sensor for 10 continuous days. The participants were classified into two groups according to their sleep efficiency: reduced (<90%) or not reduced (≥90%). Hypertension was defined as morning home blood pressure ≥135/85 mmHg or self-reported treatment for hypertension. Multivariable logistic regression models were used to obtain odds ratios (ORs) and 95% confidence intervals (CIs) to assess the relationship between sleep efficiency and hypertension adjusted for potential confounders. The results showed that two hundred and ninety-four individuals (32.5%) had reduced sleep efficiency, and 331 (36.6%) had hypertension. Individuals with reduced sleep efficiency had a higher body mass index and shorter sleep duration. In the multivariable analysis, reduced sleep efficiency was significantly related to an increased prevalence of hypertension (OR, 1.62; 95% CI, 1.15–2.28). In conclusion, reduced sleep efficiency was significantly related to an increased prevalence of hypertension in Japanese adults. Improvements in sleep efficiency may be important to reduce blood pressure in Japanese adults.

Bringing Down the Curtain… Safely

Warner Electric has developed a contactless sensor to provide improved monitoring of electromagnetic brakes for elevator, and stage and theatre applications.

Generalized Approach for Fault Detection in Medium Voltage Distribution Networks Based on Magnetic Field Measurement

Noninvasive contactless methods for electric power line monitoring based on magnetic field measurement have become an interesting topic for researchers and the electric power industry since introduction of the Smart Grid concept. By measuring and analyzing magnetic field originating from currents in power line conductors, it is possible to detect faults in the network. In medium voltage distribution networks, where a variety of different pole geometries are present, different criteria for fault detection have to be employed for each geometry, which complicates detection and influences accuracy. This paper proposes a novel approach for fault detection in medium voltage distribution networks which is based on processing of signals measured by low cost contactless magnetic field sensors. In order to create a generalized method for fault detection, a sequence of mathematical transformations of the measured magnetic field components is applied. A novel geometric transformation which eliminates influence of pole geometry is introduced, providing signals from which steady-state symmetrical components of the rotating magnetic field are computed. Those components are used as general fault detection criteria. The proposed approach is confirmed to be applicable for different fault types by a set of experiments on three-phase overhead power line model scaled to laboratory conditions.

Magnetic Sensor Design for a Permanent Magnet Linear Motor Considering Edge-Effect

This article focuses on the design of a magnetic sensor (MS) in position detection of a permanent magnet linear motor (PMLM). The MS is composed of a hall-effect-integrated-circuit and magnetic materials, and it is well known as a contactless sensor with a simple structure, and low cost. As a result, it is preferred for precise linear positioning applications. The work presented in this article consists of the following three steps to achieve high accuracy and economy in the mover position detection for a PMLM. First, the initial design of the MS is described which has been optimized using response surface methodology to obtain very low total harmonic distortion value of the sensing signal. Second, the leakage flux of PMLM is analytically investigated, from which it is determined that shielding the leakage flux is most appropriate to ensure the accuracy of the MS. Finally, in an attempt to reduce manufacturing cost, three MS prototypes using different materials (silicon steel laminated core, steel solid core, and ferrite solid core) are fabricated and tested. To verify the analytical results, several experiments are conducted. The experimental data prove that the accuracy of the MS is sufficient to use for mover position detection for the PMLM.

Design and parameter optimization of contactless vertical inductive angle sensor

Contactless inductive angle sensors are widely used in the industrial field. To date, the contactless inductive angle sensor is a planar structure, and its physical structure limits the number of turns of the excitation coil, resulting in a small eddy current on the rotor, which increases the measurement accuracy error of the sensor. Therefore, in view of reducing the sensor volume and reducing the sensor measurement accuracy error, a contactless vertical inductive angle sensor is designed. Through modeling and simulation, when the position of the rotor and stator changes, the induced voltage in the receiving coil changes sinusoidally. The structural parameters that have the greatest influence on the measurement accuracy error of the sensor are obtained by simulation. Because of the complex electromagnetic structure of the sensor, the linearly-decrease inertia weight particle swarm optimization (LIWPSO) and finite element method (FEM) are used to optimize the sensor measurement accuracy error. In the simulation, the measurement accuracy error of the optimized sensor is 0.778% in the angle range of 0°–40°. The sensor is manufactured and tested for the optimized parameters, and the observed experimental measurement accuracy error is 0.981% in the angle range of 0°–40°.

Low Power Contactless Voltage Sensor for Low Voltage Power Systems.

Contactless measurements represent the desirable solution in many contexts, where minimal cabling is required or, in general, cabling is not possible. This paper presents a new contactless voltage sensor for low voltage power systems. It is based on a contactless capacitive probe, which surrounds the power cable. It has two concentric electrodes insulated by a shield. A low power analog conditioning circuit evaluates the power line voltage by measuring the current in one of the capacitances of the probe. All the single stages of the circuit have been designed by using low-power rail-to-rail operational amplifiers, supplied at 3.3 V, in order to minimize the power absorption. The sensor has been characterized in various conditions, with sine waves and distorted signals, varying the frequency and the harmonic distortion. The influence of the current, flowing into the power cable, on the voltage measurement has been evaluated too. It shows a good accuracy (lower than 0.3%) from 100 V to 300 V, with a power consumption less than 5 mW.

Application of Open-air Capacitive Sensors for Voltage Monitoring near Terminations in HV and EHV Insulated Connections

Contactless capacitive sensors are applied to monitor(over)voltages near the overhead line terminations of asubstation or at cable to line transitions. The sensor response isthe signal time derivative when loaded with a resistiveimpedance and the waveform is restored by integration. As partof this differentiating/integrating (D/I) measuring concept, theuse of open-air sensors results in excellent EMC characteristicsbut the inherent cross-coupling to other phases has to be dealtwith. Three applications are presented: 1) For a 150 kV cabletermination the partial discharge activity needs to be related tomomentary phase voltages; 2) Measured slow front overvoltageat a 380 kV cable termination from line energizationare compared with predictions from numerical simulation; 3)The perspectives of employing the D/I method for (very) fastfront overvoltages near a 380 kV circuit breaker are examined.

Development of an Automated Analytical System of Low Cost for High-Throughput Infrared Thermometric Titration

Thermometric titration is an enthalpimetric technique of analysis that uses the enthalpy variation of a reaction to determine the equivalence point of a titration for quantification of the analyte. One of the advantages of this technique is that it does not require sample preparation, such as digestion; it only needs to weigh the sample and add auxiliary reagents. Based on this technique, the aim of this work was to develop automated equipment for thermometric titration, using a contactless infrared temperature sensor. The equipment was manufactured using the concept of additive manufacturing. A Raspberry Pi microcomputer was used to interpret the signal from the temperature sensor and to control a micropump used to dispense titrant at a rate selected by the user. Components were designed using computer-aided design (CAD) software and printed on a fused deposition material printer. For evaluation of the equipment, tests were performed using neutralization and precipitation reactions, measuring the total acidity of vinegars and sodium in sauces. The temperature of reaction was plotted in an enthalpogram, from which the endpoint could be determined. Values of agreement between the method proposed and the reference method ranged from 100 to 104% for total acidity of vinegars and from 96 to 105% for the determination of sodium in sauce. The equipment proved to be technically feasible and of low cost, given that it used alternative and biodegradable materials such as polylactic acid.

Development of a Passive Capacitively Coupled Contactless Conductivity Detection (PC4D) Sensor System for Fluidic Channel Analysis Toward Point-of-Care Applications

A sensor system based on a modified capacitively coupled contactless conductivity detection sensor is proposed and developed. The proposed system provides a passive and wireless readout technique, through which the conductivity of fluidic flow can be analyzed and foreign objects occurring in the fluidic flow can be detected. The proposed sensor system takes advantage of the series resonance principle and detects shifts in the resonance frequency and reflection coefficient to estimate the conductivity of the fluidic flow. In this paper, the working principle of the device is proposed and analyzed using a multiphysics simulation, and its performance is validated experimentally. The sensing performance is confirmed by measuring the conductivity of the fluidic media and the detection of foreign objects, such as air bubbles or water droplets, occurring in the flow. The influence of the distance between the inductors on the resonance frequency for different solution conductivities is also investigated and reported. The proposed sensor system shows its potential for use in various applications in biomedicine and chemistry, particularly in point-of-care applications, where the sensing chip can be easily set up for measurement and disposed of after use.

Water Content Continuous Monitoring of Grapevine Xylem Tissue Using a Portable Low-Power Cost-Effective FMCW Radar

This paper presents the real-time monitoring of a grapevine’s water content that flows up through the xylem tissue by means of a frequency-modulated continuous-wave radar. The application of an optimization process, based on the super-resolution multiple signal classification algorithm, has enabled the reduction of the bandwidth required to discern the xylem water content and, thus, the operating frequency, achieving a depth resolution of at least 3 mm. This design advantage has resulted in a significant step forward toward a real life application, allowing the use of fully-integrated off-the-shelf components in order to implement a completely portable low-power cost-effective radar at 23.1 GHz with a 3.4-GHz bandwidth. The sensor performance has been evaluated by means of three different experiments: irrigation cycles, day/night cycles, and comparison between irrigation cycles at different temperatures. From the experimental results, it is possible to assert that the contactless sensor presented in this paper is very sensitive to changes in the plant’s water content, differentiating between daytime and nighttime. In addition, it has been proven that temperature has a noticeable influence over the evapotranspiration, observing negative drying slopes of 5.62 and 6.28 mV/cycle at 23 °C and 26 °C, respectively.

Surface Plasmon Resonance Based Temperature Sensors in Liquid Environment.

The aim of this work is to measure the temperature variations by analyzing the plasmon signature on a metallic surface that is periodically structured and immersed in a liquid. A change in the temperature of the sample surface induces a modification of the local refractive index leading to a shift of the surface plasmon resonance (SPR) frequency due to the strong interaction between the evanescent electric field and the metallic surface. The experimental set-up used in this study to detect the refractive index changes is based on a metallic grating permitting a direct excitation of a plasmon wave, leading to a high sensibility, high-temperature range and contactless sensor within a very compact and simple device. The experimental set-up demonstrated that SPR could be used as a non-invasive, high-resolution temperature measurement method for metallic surfaces.

Experimental and theoretical research of continuous motion of rotor on anisotropic gapped elastic support

Kinematic and dynamic features of flexible rotor rolling of an unlubricated uneven-stiffness gapped support are shown with the help of a theoretical model and full-scale tests. A combination of original approaches and well-known analytical and experimental methods is used. In particular, the motion equations are Lagrangian, derived in complex and complex-conjugate coordinates, and their solutions are sought in the exponential form, by excluding contact forces from consideration and by introducing a small parameter. Vibration measurements are not made on the rig frame using accelerometers, but at the source of vibration, i.e. by direct tracking of the rotor axle by a pair of eddy-current contactless displacement sensors installed in a XY configuration. Hence, the preciseness of the experimental data does not depend on the mechanical conductivity of the parts between the source rotor and the receiver sensors. As a result, the frequency, amplitude and existence domain of retrograde precession are reliably determined, and a conclusion is drawn that rolling under a certain combination of parameters is impossible in principle.

Real-time Subject-specific Head and Facial Mimic Animation System using a Contactless Kinect Sensor and System of Systems Approach.

Facial palsies due to stroke, accidental and sportive injuries or sometimes without etiology, affect the professional and personal lives of involved patients. These disorders are not only a functional handicap but also a social integration impairment. The recovery of facial mimics with a normal and symmetrical facial expression allows involved patients to improve their living conditions and social identity. Current approaches lack of visual feedbacks. To monitor facial mimics and head movements in a quantitative and objective manners, a computer-aided animation system needs to be developed. Numerous systems have been proposed using single camera, stereo camera, 3-D scanner, and Kinect approaches. In particular, Kinect contactless sensor has been proven to be very suitable for 3-D facial simulation applications. However, little studies have employed the Kinect sensor for real-time head animation applications. Consequently, this study developed a real-time head and facial mimic animation system using the contactless Kinect sensor and the system of systems approach. To evaluate the accuracy of the subject-specific Kinect-based geometrical models, magnetic resonance imaging (MRI) data were used. As results, the mean distance deviation between generated Kinect-based and reconstructed MRI-based geometrical head models are approximately 1 mm for two tested subjects. The generation times are 9.7 s ± 0.3 and 0.046 s ± 0.005 by using the full facial landmarks and MPEG-4 facial landmarks respectively. Real-time head and facial mimic animations were illustrated. Particularly, the system could be executed at a very high framerate (60 fps). Further developments relate to the integration of texture information and internal structures such as a skull and muscle network to develop a full subject specific head and facial mimic animation system for facial mimic rehabilitation.

Method for Stabilizing the Operation of Synchronous Machines Using a Virtual Load Sensor

The article considers the methods of increasing the stability of high-power synchronous machines when stabilizing the torque angle in the structure of the automatic excitation control system. A mathematical model of an electric machine in open and closed automatic control systems is obtained, studies of electromagnetic processes and analysis of existing and proposed optimal control systems are carried out. A contactless sensor of torque angle of the synchronous motor based on measuring the available parameters of the synchronous machine and allowing us to calculate the torque angle in static and dynamic modes of operation of synchronous generator and compatible with the new control system was developed. The presented excitation control system of synchronous machine with a measuring sensor of torque angle that provides higher performance in dynamic modes, as well as allowing to stabilize the reactive power, the power factor and the voltage on the stator of the synchronous machine.

Vital-sign monitoring and spatial tracking of multiple people using a contactless radar-based sensor

Various medical systems exist for monitoring people in daily life, but they typically require the patient to wear a device, which can create discomfort and can limit long-term use. Contactless vital-sign monitoring would be preferable, but such technology is challenging to develop as it involves weak signals that need to be accurately detected within a practical distance, while being reliably distinguished from unwanted disturbance. Here, we show that a radar-based sensor can be used to monitor the individual vital signs (heartbeat and respiration) of multiple people in a real-world setting. The contactless approach, which does not require any body parts to be worn, uses two antennas (one transmitter and one receiver) and algorithms for target tracking and rejection of random body movements. As a result, it is robust against moderate random body movements (limb movements and desk work) and can keep track of individual people during vigorous movement (such as walking and standing up). A radar-based sensor can monitor the individual vital signs—heartbeat and respiration—of multiple people in a real-world setting, keeping track of individual people during vigorous movement.

Data acquisition system for MAET with magnetic field measurements

Magneto-acousto-electrical tomography (MAET) is an imaging modality to image the electrical conductivity of biological tissues. It is based on electrical current induction by using ultrasound under a static magnetic field. The aim of this study is to develop a data acquisition system for MAET based on magnetic field measurements. The static magnetic field is generated by six permanent neodymium magnets. A 16-element linear phased array (LPA) transducer is utilized to generate acoustic pressure waves inside the phantom. To measure the magnetic field intensity generated by the induced currents, contactless receiver sensors are developed using two similar disk multiple layer coils, which are Helmholtz coil sensor. Physical properties and electrical characteristics of the sensors are assessed. A two-stage cascaded amplifier is designed and utilized in the receiving system. The gain of the cascaded amplifier at 1 MHz is adjusted to be 96 dB. Experimental studies are conducted with two different phantoms, having 3 S m−1 and 58 S m−1 electrical conductivity, respectively. A-scan and B-scan images of phantoms are obtained with the LPA transducer. Comparison of the ultrasound (A-scan) and MAET signals reveals that 3 S m−1 conductive inhomogeneity can be detected with this data acquisition system. Furthermore, the front and rear interfaces of an inhomogeneity () of 58 S m−1 conductivity are detectable.

VibroNet: Recurrent neural networks with multi-target learning for image-based vibration frequency measurement

Information on the vibration characteristics of machinery or civil structures is crucial in identifying or diagnosing potential malfunctions or faults. The use of cameras in vibration frequency measurement enables the acquisition of spatially high-density information of a distant measurement target. Cameras can be used for remote monitoring or as contact-less inspection sensors for machinery or civil structures owing to their low cost, high availability, and ease of installation. However, this requires complex image processing and signal processing algorithms to interpret the vibration frequency from image data. This paper proposes an image- and machine-learning-based method to measure the vibration frequency, in which long short-term memory-recurrent neural networks (LSTM-RNNs) and multi-target learning are used to predict the vibration frequency components directly. The results of the proposed method are compared against the results obtained using an accelerometer and eddy current sensor in the frequency domain. The methodology was applied in forced vibration and free vibration laboratory experiments and real-world structure experiments including a membrane structure and a cable bridge. The experimental results show that the proposed method is robust and accurate. Proposals for future applications and research directions of this methodology and limitations and challenges in real-world implementations are presented.