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• Sampling volumes for seven commercially available EM sensors were determined. • A precise positioning system was used to characterize the sensors' fringing field. • Comprehensive sampling distance/volume were listed and visualized for each sensor. The sampling volume of electromagnetic (EM) soil moisture sensors is of significant interest due to the diverse applications for which they are utilized. However, this volume can vary considerably based on multiple factors, including the number, spacing, and length of sensor rods, as well as the operational frequency. The sensor's volume of influence is dictated by electric field lines or 'fringing fields' that develop between pairs of powered electrodes. This study involved the development of an accurate sensor positioning system employed to characterize the EM sensor's electrical fringing field in 3-directional - x, y, and z space. Sensor outputs were recorded at mm increments beginning with the sensor positioned 20 mm above the air-water interface followed by incremental immersion into a water bath until the maximum sensor output was achieved. For each measurement cycle, the sensor was repositioned to test signal output approaching the air-water interface in − x , + x , − y , + y , − z , and + z orientations. The sensor sampling volume was determined based on the normalized 99% output value, which was assumed to represent the sensor position relative to an air-water interface where the sensor fringing field just begins to 'sense' or to become impacted by the air phase, thereby reducing the signal amplitude. Our results vary somewhat from other studies using a similar evaluation approach, leading us to conclude that EM-sensor sampling volume determination is both complex and imprecise as a result of the global sensor market's varied circuits and electrode configurations. EM soil moisture sensors evaluated in this study exhibited sampling volumes of 386 cm3 (TDR-315), 66 cm3 (TDR-310H), 398 cm3 (CS655), 45 cm3 (EC-5), 40 cm3 (HydraProbe II), 148 cm3 (WET150), and 49 cm3 (TEROS 12), which were smaller than manufacturer reported volumes. [ABSTRACT FROM AUTHOR]

• Measurement errors of ε were determined for eight EM sensors in high EC solutions. • Visualized measurement errors for each sensor under varying EC conditions. • Verified feasibility of insulation-coated probes for measuring ε in high EC conditions. Soil water content stands as a pivotal parameter across numerous research disciplines and engineering applications. Electromagnetic (EM) sensors have gained widespread usage in monitoring soil water content. While commonly employed sensors are suitable for typical agronomic- or landscape-soil environments, they may exhibit significant deviations under conditions of high-salinity or -electrical conductivity (EC). We investigated sensing limits under the influence of increasing EC and the resulting accuracy of dielectric permittivity (ε) determinations using commercial soil water content sensors. Tests were conducted using eight commercially available EM sensors (CS655, HydraProbe II, TDR-305N, TDR-310N, TDR-315N, TEROS 12, TEROS ONE, and WET150). For these uncoated rod sensors, most were accurate within ±3 % relative permittivity errors in saline solutions within the range of 0‒4 dS m−1 while TDR-305N, TEROS ONE and WET150 maintained an accuracy of 5 % for EC values up to 9.24 dS m−1. We explored extending the working range of some sensors to high-saline environments by adding an insulating coating on sensor rods. Since the coated probe not only perceives the characteristics of the immersed medium but also interacts with the coating material itself, a calibration model was evaluated for determining the actual ε of the evaluated medium. The strong correlation between a four-point calibration and the model demonstrates the effectiveness of calibrating coated EM sensors for ε determination using only a limited number of calibration materials. The findings presented here could serve as a valuable resource when selecting EM sensors for use in high-saline environments. Results also shed light on the potential to extend the sensing range through the integration of insulating coatings. [ABSTRACT FROM AUTHOR]

Highlights • A full EM sensor-sample FE model determines the permeability of dual phase steel sheets. • Permeability and tensile strength are both affected by ferrite fraction and grain size in dual phase steels. • Tensile strength of dual phase steel sheets of any thickness can be predicted by an EM sensor. • Ferrite fraction of dual phase steels can be predicted by an EM sensor. Abstract It is desirable to be able to non-destructively evaluate the microstructural features and/or mechanical properties of steel strip. An electromagnetic sensor – sample FE model, developed in COMSOL multi-physics software, has been developed to determine the relationship between the low magnetic field relative permeability and microstructure (phase balance and grain size), and hence tensile strength, for commercial dual phase (DP) steel sheets of any thickness. The model for the effect of thickness on the sensor signal has been validated using DP steel sheets of 1 to 4 mm. It was found that the relative permeability is strongly dependent on the phase balance (fraction of ferrite and martensite) in the DP steels with an increasing relative permeability being seen for a higher fraction of ferrite. In addition, changes in the ferrite grain size also affect the relative permeability (increase in grain size increases relative permeability) and hence EM sensor signal, this being more significant for the higher ferrite content DP grades. Both these microstructural features affect the tensile strength (which decreases with an increase in ferrite fraction and increase in grain size), which results in a good correlation between the relative permeability and tensile strength. The results from the relative permeability – microstructure – tensile strength investigation and FE model to account for strip thickness have been combined to allow the prediction of tensile strength from EM sensor measurements on as-received commercial DP steel sheets of varying thickness and the approach has been tested. [ABSTRACT FROM AUTHOR]

This paper presents a modeling and experimental study using a multi-frequency electromagnetic (EM) sensor system, for non-destructive evaluation of rail decarburisation. The EM sensor is configured with a H-shaped ferrite core, which was excited with a multi-frequency waveform over the range of approximately 1–100 kHz. Finite-element (FE) simulation was carried out to establish the link between the EM sensor output and the level of decarburization. Rail samples with different levels of decarburisation, due to different bloom reheat times prior to rolling were tested in the laboratory. It was found that the zero-crossing frequency of the EM sensor response is linearly proportional to the decarburisation level by FE simulation, theoretic analysis and experiment. This finding is helpful in understanding the response of the EM sensor to rail decarburisation and could lead to a non-contact, non destructive method for use during rail manufacturing. In addition, on-site measurement (tests carried out in the Rail & Section Mill at Tata Steel) was taken on a 110 m long rail product, with the results indicating that the EM sensor response correctly follows the expected decarburisation profile along the rail length. [ABSTRACT FROM AUTHOR]

This paper presents the MSM structure magnetic detector device that normally detects the electromagnetic wave. The device is special design for magnetic field detector and still detects the electromagnetic wave as normal function. The schottky diode with the split contacts structure allows us to reach this target. The device operates with the saturation current and the magnetic response is the current difference between two contacts which is injected from one metal and deflected in semiconductor toward to another metal. From the simulation result by Sentaurus TCAD, the relative sensitivity is 14.19 mT -1 at the current 0.3 μA. This device is the first MSM multi-sensor for magnetic and electromagnetic wave detector. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop a new method for quantifying intersegmental motion of the spine in an instrumented motion segment L4–L5 model using ultrasound image post-processing combined with an electromagnetic device. A prospective test–retest design was employed, combined with an evaluation of stability and within- and between-day intra-tester reliability during forward bending by 15 healthy male patients. The accuracy of the measurement system using the model was calculated to be ± 0.9° (standard deviation = 0.43) over a 40° range and ± 0.4 cm (standard deviation = 0.28) over 1.5 cm. The mean composite range of forward bending was 15.5 ± 2.04° during a single trial (standard error of the mean = 0.54, coefficient of variation = 4.18). Reliability (intra-class correlation coefficient = 2.1) was found to be excellent for both within-day measures (0.995–0.999) and between-day measures (0.996–0.999). Further work is necessary to explore the use of this approach in the evaluation of biomechanics, clinical assessments and interventions. [ABSTRACT FROM AUTHOR]

Abstract: Analysis of the electromagnetic (EM) properties of power station steels, measured using a non-contact magnetic sensor, is of significance as such properties are indicative of the microstructure of the material and can be potentially exploited for non-destructive testing. In this paper, we present EM measurements of cylindrical power station steel samples (P9 and T22 grades) with different microstructures: normalised and tempered (representative of the initial condition), as normalised and after service exposure. In order to obtain the magnetic properties the B–H curves of these samples were measured. Cylindrical air-cored and printed circuit board (PCB) coil integrated sensors were used to measure the incremental permeability. Analytical and numerical methods (Finite Elements Methods) were employed to calculate the sensor response of these samples. The electromagnetic properties of the different steels were inferred by fitting the finite element models to the measured results. In addition, sensitivity and error analysis were carried out to evaluate the accuracy of the method. [Copyright &y& Elsevier]

Abstract: Based on the law of electromagnetic induction, a novel contactless absolute angular position sensor has been designed in the literature. It is mainly composed of three parts: two emitters, an annular encoder and a signal processing circuit. The emitter integrates a main coil and two groups of secondary windings, each of which comprises two series-wound coils with inverse enwinding directions. N and (N −1) copper sheets with regular shapes are arrayed uniformly in the outer and inner circles of the encoder which are corresponding to the two emitters respectively. The main coil stimulated by the external current can generate a magnetic field, which can be detected by two groups of secondary windings and a corresponding voltage signals will be exported. As the emitter rotated over any two neighboring copper sheets of the encoder, a period of sine and cosine signals will be outputted by two groups of secondary coils. The absolute angle position signals can be calculated based on the relationships between angles calculated by N and (N −1) periods of sine and cosine signals produced by the inner and the outer circles of emitters and the angles the emitter has rotated around the rotation axis. Experiment has been performed on a prototype of the angular position sensor and the results demonstrate the proposed scheme is feasible. Theoretic precision and testing error analysis of the sensor has been pursued at the end of the paper. [Copyright &y& Elsevier]

Abstract: This paper reports the evaluation of rail decarburisation based on eddy current methods using an H-shaped sensor. Rails with different levels of decarburisation, due to different bloom reheat times (195min–613min), were used. Experimental results have indicated that the measured inductance of the sensor is closely related to the reheat furnace dwell time of the rail samples. Quantification of the amount of decarburisation, using micro-hardness tests and visual evaluation, and the predicted amount (based on Fick''s law), have been compared with the eddy current approach, with reasonable agreement being seen. [Copyright &y& Elsevier]

Abstract: This paper presents a modelling and experimental study on an H-shaped ferrite core electromagnetic sensor for phase transformation detection in steel rolling and controlled cooling applications. It has been found that the response of the H-shaped sensor after normalisation can be described by a simple analytical model. Further, it has been found that the zero-crossing frequency for the real part of the inductance spectra and the peak frequency of the imaginary part of the inductance spectra are linearly proportional to the magnetic permeability of the steel strip under test. These findings are helpful in understanding the response of the EM sensor in an industrial set-up and possibly lead to more accurate determination of steel magnetic properties and hence characterise the micro-structural properties. [Copyright &y& Elsevier]

Abstract: This paper presents the measurement of decarburization of steel rods with an electromagnetic sensor using an analytical model both in online and offline scenarios. Loss of carbon (decarburization) at the steel surface can have a significantly detrimental effect on mechanical properties of products, since hardness, fatigue, strength and wear properties are strongly dependent on carbon content. Currently, measurement of decarburization is by destructive methods, such as metallographic observation or hardness tests on a sample cross-section after processing. A non-destructive EM method is proposed in this paper. An analytical solution for the inductance of a circular air-cored coil encircling a steel rod is deduced and further a simplified model is obtained which shows that for both online and offline cases, the thickness of the decarburisation layer is proportional to the inductance difference with and without decarburisation. Using this simplified model, decarburisation thickness can be obtained. The results have been verified by both finite element models and metallographic observations. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the measurement of ferrite/austenite phase fraction using a multi-frequency electromagnetic sensor. A simple analytical model was established that can describe the response of the sensor for samples containing varying fractions of ferromagnetic phase over a wide range of frequencies (100Hz–1MHz). In particular, a new feature, the peak frequency of the imaginary part of the inductance, is found to be able to distinguish between samples across the whole range of the ferrite percentages. FEM models were used to simulate representative real microstructures from the samples and to relate the relative permeability to the ferrite fraction. Experimental results suggest that the accuracy of ferrite/austenite percentage measurement is within 8%. [Copyright &y& Elsevier]

Abstract: Objective: Navigation systems enable neurosurgeons to guide operations with imaging data. Sensor-based neuronavigation uses an electromagnetic field and sensors to measure the positions of the patient''s brain anatomy and the surgical instruments. The aim of this investigation was to determine the accuracy level of sensor-based tracking in a large patient collection. Methods: This study covers 250 patients operated upon during a continuous 5.5-year period. The patients had a wide range of indications and surgical procedures. The operations were performed with a direct current (DC) pulsed sensor-based electromagnetic navigation system. Four kinds of errors were measured: the fiducial registration error (FRE), the target registration error (TRE), brain shift, and the position error (PE). These errors were calculated for five subgroups of indications: target determination and trajectory guidance, functional navigation, skull base and neurocranium, determination of resection volume, and transnasal and transsphenoidal access. Results: The overall mean FRE was 1.66mm (±0.61mm). The overall mean TREs were 1.33mm (±0.51mm) centroid and 1.59mm (±0.57mm) lesional. The overall mean brain shift for applicable cases was 1.61mm (±1.14mm). The overall mean PE was 0.92mm (±0.54mm). Conclusions: By and large, modern sensor-based neuronavigation operates within an acceptable and commonplace degree of error. However, the neurosurgeon must remain critical in cases of small lesions, and must exert caution not to introduce further interference from metal objects or electromagnetic devices. [Copyright &y& Elsevier]

Abstract: The combination of an electromagnetic and a dual energy X-ray transmission sensor is a new method for automatic sorting of scrap non-ferrous metals. It allows classification of metals based on differences in electrical conductivity and atomic number. Both sensors were developed and tested at Delft University of Technology. In a number of experiments non-ferrous metals from post-shredder scrap were identified and sorted based on the combined sensor output. The results and possible industrial applications in automatic sorting of scrap metals are discussed. A sorting system that includes both sensors allows replacement of conventional ferro-silicon based dense medium systems by an entirely dry process that does not require any washing. [Copyright &y& Elsevier]

Abstract: An electromagnetic sensor consisting of one exciter and three separated (triple) detectors is developed for both tracking the weld seam of a workpiece and controlling the sensor-to-workpiece distance (height) simultaneously. The left and right detectors are used to track the seam, while the fore and right detectors allow the sensor to determine the height and gap width by being coupled their outputs together. A series of experiments with the proposed sensor located above a mild steel plate containing a seam are carried out to examine the effectiveness of the sensor. The results revealed that the proposed sensor could fairly well track the desired seam and also well control the height to be constant even when the gap width of the seam varied. The gap width can be also determined during the seam tracking and height control by using the sensor outputs. As a consequence, these can provide the developed sensor with substantial improvement for industrial uses with respect to the previous electromagnetic sensors being used for the weld seam tracking. [Copyright &y& Elsevier]

Abstract: A multi-frequency electromagnetic sensor was used to measure the impedance and inductance of samples containing varying fractions of ferromagnetic phase over a range of frequencies (100Hz to 1MHz). The impedance values are approximately linearly related to ferrite fraction for random microstructures up to about 40% ferrite, at which point the ferrite increasingly forms connected pathways and the impedance signal does not increase significantly. The zero cross-point frequency was found to distinguish between samples with higher (>40%) ferrite percentages and can be related to the effective relative permeability of the sample. [Copyright &y& Elsevier]

• Two cells of split ring resonators are used to improve the electromagnetic interaction between the sensor and water/Glucose. • Water/Glucose is simulated in Comsol using a realistic model. • Return loss is a useful parameter for determining glucose level in water for this sensor. • Electronic prototype is proposed to improve the sensitivity at an optimal frequency. A microwave sensor for glucose concentration measurement is presented. The proposed sensor is composed of two cells of circular split ring resonator (SRR) with a liquid holder put on both cells. Those resonators are coupled to a coplanar line forming a two-port network whose S-parameter response provide an information about the dielectric properties of the liquid that is under study. This paper presents a numerical simulation and experimental study of our new configuration of the resonators to assess the sensitivity of the sensor toward small change in glucose concentrations in water. An electronic prototype has been used to improve the detection; a resolution of 1.665 mmol/l is reached at the frequency 1.9 GHz. The obtained results have shown the effectiveness of this new configuration of resonators sensor for non-invasive measurement on the small change in dielectric parameter ε r. Therefore, the proposed sensor is well fitted for real time measurement, non-destructive, precise, and low cost. [ABSTRACT FROM AUTHOR]

• An external electromagnetic (EM) sensor was developed. • Experimental and numerical investigations were carried out to demonstrate the effectiveness. • The external EM sensor has a good accuracy in estimating the mass loss of corroding steel. • Effects of parameters were investigated through numerical simulation. Corrosion of steel is one of the major causes for the degradation of reinforced concrete (RC) structures. In this regard, the assessment of reinforcement corrosion is critical in evaluating the service life of RC structures. The present study aimed to develop an electromagnetic-based apparatus which can be externally positioned on RC structures, to detect and monitor the corrosion of embedded steels. Experiments and numerical simulations based on finite element method (FEM) were carried out to verify the effectiveness of the external electromagnetic (EM) sensor. Different degrees of corrosion for steel in concrete specimens were obtained by impressing current method. Experimental results showed a linear relationship between the mass loss of corroding steel and the change of magnetic flux density sensed by the external EM sensor. Compared with the numerical results obtained from FEM simulations, a good accuracy was exhibited in estimating the mass loss of corroding steel in concrete by the change of magnetic flux density. Numerical simulations were further conducted to investigate the effects of the dimension and position of steel, the distance between testing surfaces of the EM sensor, and the magnitude of magnetic field intensity. As a non-destructive technique, a promising application of the external EM sensor was demonstrated in terms of evaluating the corrosion degree of steel in concrete, with the feasibility to increase its sensitivity by controlling the driving current and coil turns. [ABSTRACT FROM AUTHOR]

• Macro FE modelling on electromagnetic responses to steel microstructures/mechanical properties. • Non-destructively real-time in-line steel microstructure inspection using magnetic properties. • Dynamic control via varying the cooling strategies or heat treatment using EM sensor feedback. • High temperature tests using lab-based furnace and run-out table (ROT) with cooling system. Magnetic and electric properties (such as low field relative permeability and resistivity) are sensitive to changes in both steel microstructure and temperature. Recently an electromagnetic (EM) sensor system (EMspec™) has been installed to non-destructively on-line monitor the phase (microstructure) transformation in strip steels during the cooling process after hot rolling. To use an EM system to provide dynamic control via varying the cooling strategies or heat treatment using sensor feedback, which can give higher quality steel products with excellent mechanical properties at reduced cost, requires accurate interpretation of the EM sensor signals and predictive capability of the signals from desired microstructures at the relevant temperatures. A 3D FE model is reported here that allows the EMspec™ sensor output (Zero Crossing Frequency, ZCF) to be related to the steel microstructure (phase fraction) using the relationships between permeability and resistivity with microstructure and temperature. The model has been verified by room temperature measurements on various steel grades samples (varying microstructure and strip thickness). High temperature experimental tests have been carried out using a lab-based furnace and run-out table (ROT) with cooling system, mimicking the real-time monitoring of phase transformation of steel strip products. The experimental results have been compared to predicted sensor signals for the known transformation behaviour, determined independently using dilatometry. In this paper the process by which the model can be used to predict the ZCF values for different transformation behaviour, for example different ferrite fractions prior to bainite/martensite formation in a two phase steel, which in turn can be used to control the cooling strategy to achieve a desired microstructure and mechanical properties is discussed. [ABSTRACT FROM AUTHOR]