Induction Coil Sensor Research Articles

Application and Performance Analysis of Hollow Cores in Lightweight Design of Induction Coil Sensor

Application and Performance Analysis of Hollow Cores in Lightweight Design of Induction Coil Sensor

Evaluation of Airport Pavement Base Layer Stiffness Characteristics via Embedded Field Sensors

Real-time stiffness monitoring of unbound aggregate layers using embedded field sensors is crucial for advanced airport pavement design and management. This paper describes research findings on monitoring base layer stiffness characteristics for airport pavements using an embedded bender element (BE) field sensor, inductive coil sensors, and pressure cells. A full-scale pavement test section was constructed at the Federal Aviation Administration (FAA)’s National Airport Pavement Test Facility (NAPTF). A BE field sensor, inductive coil sensor pairs, and pressure cells were installed in the unbound aggregate base to evaluate the layer stiffness, applied load stress, and deformation characteristics. A triple dual tandem gear loading module applied 58,000 lb per wheel to the tested section with a wander pattern consisting of 66 passes arranged in nine lateral wander positions. Dynamic responses of coil sensors and pressure cells were collected during the traffic test, whereas BE signals were collected after completing each wander pattern. Laboratory repeated load triaxial tests with BE instrumentation were also conducted to establish a correlation for converting BE field sensor readings to layer modulus properties. The in situ modulus characteristics of the aggregate base layer were evaluated during full-scale testing using two methods: shear wave velocities from a BE field sensor, and strain and stress measurements from coil sensors and pressure cells. The moduli estimated using both approaches fell into typical ranges of crushed aggregate bases and were highly comparable. The moduli from the dynamic sensor measurements clearly showed the effect of vehicle wander on aggregate base layer measured responses.

Multifunctional Induction Coil Sensor for Evaluation of Carbon Content in Carbon Steel

Carbon steel has proven to be an important structural and functional material that plays an irreplaceable role in the worldwide economy. The influence of carbon on the mechanical and magnetic properties of the steel is well understood. Thus, the precise knowledge of the amount of carbon content in steel is crucial. Magnetic Barkhausen noise (MBN), magnetic hysteresis loop (MHL), and impedance measurements are reliable tools to assess carbon content. In this work, a multifunctional induction coil sensor used for MBN, MHL, and impedance measurements is designed and optimized. A multifunctional measurement system using the optimized induction coil is employed to measure MBN, MHL, and impedance signals. The parabolic dependence of the maximum value of MBN envelope on carbon content in steel is theoretically analyzed and experimentally verified. Coercive field and remanence from MHL measurements as well as the maximum impedance value are found to be proportional to carbon content and their dependence is explained with analytical simulations.

A novel core structure of inner-ringed multi-pitch rods for lightweight induction coil sensor design

A novel inner-ringed multi-pitch rods core structure for lightweight induction coil sensor design, in which the higher-permeability magnetic rods are located in the inner ring of the induction coil, is proposed. The abbreviation for the novel core structure is “IRMPR core structure”. It is theoretically shown that the induction coil sensor sensitivity of the IRMPR core structure is equal to that of the single-rod solid structure. Compared with the traditional single-rod solid magnetic core structure, the mass of magnetic core of the IRMPR core structure is reduced more than 28%, however, the sensor sensitivity is not sacrificed. Besides, the performance of the IRMPR core structures with permalloy and Zn-Mn alloy magnetic cores were tested under 500Hz and 1–22kHz band conditions, and the performance was improved compared with the single-rod structure of the same materials. The results demonstrate the potential for IRMPR core structure application to various induction coils with different inner-ringed magnetic core materials under broadband conditions. The study also provides a method to vary the sensitivity and resonant frequency of the induction coil sensor by changing the magnetic core arrangement. Furthermore, thinner magnetic rod is more cost-effective and IRMPR core structure will be more compact for the integration of the sensors and their electronics within a single housing.

유도코일을 이용한 3상 전류 검출기용 센서모듈 설계

According to the increase of required load capacity for the low-voltage AC system, compact current detection modules are required to secure the safety of electric systems. In particular, low-voltage infrastructure is required due to the increase in electricity demand for intelligence, customer convenience, and safety in the railway sector. In this paper, design consideration of inductive coil sensor for 3-phase current detector is proposed to expand linearity and improve measurement precision. The design method considering the limited space and practical implementation constraints was studied. To verify the proposed method, a 150A-class prototype was designed. Several induction coil sensor output variations with different specifications were verified through experiments.

A Novel Method for Thickness Measurement in Conducting Materials by Apparent Conductivity Calculation Through Transient Eddy Current NDE

This paper describes a novel method for thickness measurement in conducting material by combining the measurement of the decaying induced eddy current and its associated apparent conductivity calculation. In conventional frequency domain NDE (Non-destructive Evaluation), the skin depth is the limiting factor due to the single frequency excitation. In contrast, with a pulsed excitation, the induced eddy currents decay with time and the decay of the eddy current consists of continuum of frequencies and hence the entire thickness of the conducting material could be investigated in a single shot. The time at which the decay of the eddy current is maximum is called diffusion time “tm” and the corresponding calculated value of apparent electrical conductivity “σmapp” both of which can be directly correlated to the thickness of the material. Since the induction of the eddy current and its associated secondary magnetic field measured by using suitable magnetic sensors [hz α (σ/t)3/2 for B-field and Vz α (σ3/2/t5/2) for an induction coil] is directly related to the conductivity of the materials, one can calculate the apparent conductivity σapp(t) as a function of decay time. Apparent conductivity calculations have been made for aluminum plates based on the thin conducting sheet model in which the applied magnetic field is uniform throughout the thickness. Subsequently, transient measurements have been performed with stacks of aluminum plates by using pickup coils in the form of an absolute as well as differential configuration. From this, it has been shown that the square root of the ratio of the maximum diffusion time, tm and the corresponding apparent conductivity, σmapp called as maximum diffusion depth, δm which is proportional to the plate thickness. The diffusion depth is a parameter derived from standard electromagnetic equations which is analogous to the skin depth in the frequency domain. In this work, induction coil sensors of both types have been used to measure the transients, and the other instruments such as transmitter, transmitter controller and data acquisition system used for this work are the same ones used for TDEM (time domain electro-magnetic) based geophysical applications.

Ultralow Noise Low Offset Chopper Amplifier for Induction Coil Sensor to Detect Geomagnetic Field of 1 mHz to 1 kHz

An induction coil sensor (ICS) is important for measuring low-frequency (DC-1kHz) geomagnetic field. The accuracy of the preamplifier is one key factor determining the performance of the sensor. But the preamplifier is susceptible to 1/ f noise, offset voltage and drift. In order to eliminate these influences, a preamplifier circuit with three amplifier stages based on chopper technology has been designed, and its performance has been tested. The results show that: 1) The 1/ f noise corner frequency is 3 mHz, the equivalent input voltage noise (EIVN) level of the circuit is [Formula: see text] and [Formula: see text]; 2) The equivalent input current noise (EICN) level of the circuit is [Formula: see text]; 3) The offset voltage is about 600 nV, and the time drift performance is excellent. In conclusion, the preamplifier circuit has characteristics of ultralow noise, low offset voltage and low time drift. It can effectively amplify low-frequency weak geomagnetic signals from 1 mHz to 1 kHz and provides excellent performance for low-frequency ICS.

Comparison and analysis of multiple signal processing methods in steel wire rope defect detection by hall sensor

Steel wire rope (SWR) defect signal processing techniques and methods are the key to exact defect detection and identification, which is important in guaranteeing human lives and property. But the inspection signals sensed by the commonly used inductive coil sensor are often susceptible to the detector’s scanning speed, wire rope shaking and vibration, whereas they are unaffected when induced by hall element sensor. Thus, the experiments for wire rope local fault (LF) of broken wire inspection by hall sensors and magnetic flux leakage (MFL) testing method are conducted, and different groups of original signals are obtained. Then, performances of multiple signal processing methods are compared and evaluated in the perspective of baseline drift elimination and signal denoising. Besides, the main impact parameters in these signal processing methods are investigated and revealed. Finally, comparisons and discussions for different filtering methods are analyzed and presented.

Analysis, design and optimization of compact ultra-high sensitivity coreless induction coil sensors

For contactless inductive flow tomography we require a compact magnetic field measurement system with a dynamic range of 5 orders of magnitude in order to detect the amplitude and the phase of an alternating magnetic field of 1 mT strength with a precision better than 5 nT and a phase error no larger than 10−2 deg. In some applications a static magnetic field of about 300 mT is also present, resulting in a total dynamic range of 7 orders of magnitude.We present theoretical and experimental analyses of absolute and first order gradiometric induction coil sensors with sensitivities larger than 500 V/T · Hz) and diameters of 28 mm. From their equivalent circuits, we derive the associated complex-valued transfer functions and fit these to calibration measurements, thereby determining the value of the equivalent circuit components. This allows us to compensate their non-linear frequency-dependent amplitude and phase behaviour. Furthermore, we demonstrate the optimization of coils based on Brooks’ design of equal squares in the adaptation by Murgatroyd, which maximizes the inductance (and thereby most likely the sensitivity) of the coils. Finally, we design a new coil with a diameter of 74 mm and a sensitivity of 577 V/(T · Hz) with an analytically predicted equivalent magnetic field noise of around in the 1 Hz frequency range, which is then confirmed by measurements on the manufactured prototype.

Current and Magnetic Field of a Simplex Wave Winding in a DC Generator

The DC generator is widely used in the fields of industry motor control and energy transfer, and the simplex wave winding (SWW) is the main winding pattern of the DC generator. In this paper, a brief introduction to the structure of the SWW is presented first. Then the characteristics of the current and electromagnetic fields of the SWW are analyzed particularly in a commutation cycle and two typical concepts of the “central slot” (CS) and the “widest magnetic peak area” (WMPA) are proposed respectively. The characteristic frequency which is 63 and 21 times higher than the fundamental frequency (FF) of the voltage between two brushes is obtained and verified from 6 conditions of different speeds and currents. Furthermore, with the help of an induction coil sensor between two main poles, the characteristic frequency 84 times higher than the FF of the WMPA is also verified in 6 conditions and the results coincides with the theory well.

A flexible printed-circuit coil for scanning transversal magnetic-fields errors in accelerator magnets

The proof of principle of an induction coil sensor for scanning transverse magnetic-field errors is presented. This sensor allows to build a rotating-coil transducer that is not sensitive to the axial magnetic field component in the magnets. The main design objective is to optimize the positions of each coil loop in the sensor's transverse cross-section, to guarantee the desired sensitivity factors to the specific field-harmonic components. After illustrating the magnetic measurement principle, the design and the manufacturing technology of the flexible circuit board are presented. Then the metrological characterization, the calibration and the functional tests are discussed.

Computational and Experimental Study of Gradiometer Coil Sensor Design for Single-Sided Magnetic Particle Imaging

This paper presents the design and construction of an induction coil sensor, suitable for single-sided Magnetic Particle Imaging (MPI) scanner. Tomographic images of the magnetic nanoparticles (MNPs) used as tracer need to be formed from the voltage induced in the pickup coil as a result of the particles’ magnetization response when excited by a superimposed magnetic field from the excitation and selection fields. The coil sensor is looped in the form of the solenoid (Maxwell arrangement) and inserted into the coaxial arrangement of the excitation and selection field coils to form the single-sided scanner geometry. A first-order gradiometer is realized by winding two identical coils, each coil having 208 turns, with a baseline distance of 30 mm. Simulation and experimental results revealed that the induced voltage is directly proportional to the excitation field, and inversely proportional to the distance away from the excitation coil. Results obtained showed that the designed gradiometer pickup coil is sufficient for single-sided MPI scanner, to be applied in the sentinel lymph node biopsy (SLNB) for breast cancer detection.

Measurement and Analysis of the Dynamic Effects in an HTS Dipole Magnet

The EuCARD-2 project, co-funded by the European Commission, supports the design, production, and standalone cold testing of a high-temperature superconducting demonstrator insert-magnet. The so-called Feather-M2 dipole magnet was built at CERN, using Roebel cable consisting of REBCO coated conductor tapes. In this paper, we will discuss the preparation and results of the magnetic measurements performed on the Feather-M2 model magnet, operated in forced-flow helium gas. For this test, the magnet was instrumented with cryogenic Hall-Sensors, which are cross-calibrated “ in situ ” using induction-coil sensors. We present the measurement procedure, the instrumentation used, and the measurement results. These include the transfer function and dynamic field effects. The most exciting scientific result is the low level of persistent current effects observed in this model magnet.

A portable diagnostic device for cardiac magnetic field mapping

In this paper we present a portable magnetocardiography device. The focus of this development was delivering a rapid assessment of chest pain in an emergency department. The aim was therefore to produce an inexpensive device that could be rapidly deployed in a noisy unshielded ward environment. We found that induction coil magnetometers with a coil design optimised for magnetic field mapping possess sufficient sensitivity ( noise floor at 10 Hz) and response ( at 10 Hz) for cycle averaged magnetocardiography and are able to measure depolarisation signals in an unshielded environment. We were unable to observe repolarisation signals to a reasonable fidelity. We present the design of the induction coil sensor array and signal processing routine along with data demonstrating performance in a hospital environment.

Development of a low noise induction magnetic sensor using magnetic flux negative feedback in the time domain.

Time-domain electromagnetic system can implement great depth detection. As for the electromagnetic system, the receiver utilized an air coil sensor, and the matching mode of the sensor employed the resistance matching method. By using the resistance matching method, the vibration of the coil in the time domain can be effectively controlled. However, the noise of the sensor, especially the noise at the resonance frequency, will be increased as well. In this paper, a novel design of a low noise induction coil sensor is proposed, and the experimental data and noise characteristics are provided. The sensor is designed based on the principle that the amplified voltage will be converted to current under the influence of the feedback resistance of the coil. The feedback loop around the induction coil exerts a magnetic field and sends the negative feedback signal to the sensor. The paper analyses the influence of the closed magnetic feedback loop on both the bandwidth and the noise of the sensor. The signal-to-noise ratio is improved dramatically.

Using induction coil sensor optimization techniques for designing compact geophysical transmitters

We have developed and tested code to optimise electromagnetic (EM) sensors to improve performance of the ARMIT B field induction coil sensor at desired frequencies. We aim to use the optimised parameters to develop a compact air core transmitter, which will form the basis for developing a compact ferromagnetic core transmitter. Techniques for optimising induction coil sensors are well established in literature and use analytical equations for the objective and constraint functions. Alternatives for EM sensor design are also well documented. In contrast, the design of compact transmitter systems needed for portability or in boreholes have limited discussion in the literature and have many more design constraints than sensors. Our ultimate intention is to use established sensor optimisation techniques to build a compact transmitter with sufficient magnetic dipole moment. To optimise an ARMIT induction current sensor we develop the algebraic expression for the total internal sensor noise to use as a constraint function. The objective function is the weight of the sensor. We aim to achieve noise goals of v / and v / frequencies of 1Hz and 2 kHz, respectively. 1 Hz was chosen because that is a common base-frequency for conductive sulphide exploration and 2 kHz was chosen as being appropriate for nuclear magnetic resonance investigations. We use numerical non-linear constraint optimization techniques to predict a target noise level of 1 pT at 1 Hz. , At this stage we predict the best 2 kHz sensor to have 4 fT noise at 2 kHz. This was based on existing dimensional and weight constraints on the induction coil sensor. We introduce an analogous method of transmitter optimisation using transmitter dipole moment as the objective function.

A Generalized Study of Coil-Core-Aspect Ratio Optimization for Noise Reduction and SNR Enhancement in Search Coil Magnetometers at Low Frequencies

Here, a generalized induction coil sensor model (more generalized than other models) has been considered at low frequencies (within 0.1–100 Hz), and the equivalent magnetic field of the coil’s thermal noise and the sensor’s signal-to-noise ratio (SNR) were calculated theoretically based on the dimensions and geometry of the coil winding and its core. In our suggested theoretical consideration, all involved parameters were considered and optimized without any assumption and constraint, while some authors in their latest reports, have been used some assumptions and constraints in their sensor calculations (such as holding constant the sensor’s volume and aspect ratio). Our calculations indicated that the equivalent magnetic field of the thermal noise can be minimized by the coil-to-core weight ratio. Moreover, it was found that the sensor’s SNR can be maximized with only a special value of core aspect ratio (length to diameter of core ratio). The obtained theoretical results were evaluated experimentally by fabricating a search coil magnetometer model, using the optimum parameters. The resonance frequency and the parasitic capacitance of the coil were measured. Moreover, the variations of the transfer function of the magnetometer, with respect to frequency, were studied. Thus, it was shown that, at low frequencies, our experimentally measured noise data exhibit better agreement with our suggested theoretical results with respect to the state of the art.

A seafloor electromagnetic receiver for marine magnetotellurics and marine controlled-source electromagnetic sounding

In planning and executing marine controlled-source electromagnetic methods, seafloor electromagnetic receivers must overcome the problems of noise, clock drift, and power consumption. To design a receiver that performs well and overcomes the abovementioned problems, we performed forward modeling of the E-field abnormal response and established the receiver’s characteristics. We describe the design optimization and the properties of each component, that is, low-noise induction coil sensor, low-noise Ag/AgCl electrode, low-noise chopper amplifier, digital temperature-compensated crystal oscillator module, acoustic telemetry modem, and burn wire system. Finally, we discuss the results of onshore and offshore field tests to show the effectiveness of the developed seafloor electromagnetic receiver and its performance: typical E-field noise of 0.12 nV/m/rt(Hz) at 0.5 Hz, dynamic range higher than 120 dB, clock drift lower than 1 ms/day, and continuous operation of at least 21 days.

Detection of damage precursors with embedded magnetostrictive particles

Polymer composites subjected to cyclic loading would exhibit damage precursors, such as crazes and microcracks, during the first few load cycles. However, damage precursors are not readily detectable with existing sensing techniques, and as such current service life prediction methods depend on macroscopic damage measures. For critical airframe structures, information on macroscopic damage does not provide adequate warning time for corrective actions. This article explores the feasibility of embedding particulate magnetostrictive particles for sensing damage precursors during the early stage of fatigue damage. The sensing is based on the notion that magnetostrictive particles undergo irreversible changes in magnetization intensity when subjected to cyclic loading, and that this change can be captured with an induction coil sensor. In the sequel, Terfenol-D particles are embedded between layers of pre-preg AS4/3501-6 material system. The specimen is then subjected to fatigue loading while monitoring the change in the strength of the magnetic flux density using pickup coil. Results show that the embedded system exhibits a change in magnetic state, in tens to hundreds of millivolts of pickup coil, starting from the first few load cycles. Scanning electron microscopy and acoustic emission data were used to validate the observed results.

The Effect of Textile-Based Inductive Coil Sensor Positions for Heart Rate Monitoring

In the research related to heart rate measurement, few studies have been done using magnetic-induced conductivity sensing methods to measure the heart rate. The aim of this study was to analyze the effect of the position of a textile-based inductive coil sensor on the measurement of the heart rate. In order to assess the capability of the textile-based inductive coil sensor and the repeatability of measured cardiac muscle contractions, we proposed a new quality index based on the morphology of measured signals using a textile-based inductive coil sensor. We initially explored eight potential positions of the inductive sensor in a pilot experiment, followed by three sensor positions in the main experiment. A simultaneously measured electrocardiography (ECG) signal (Lead II) which was used as a reference signal for a comparison of the R-peak location with signals obtained from selected positions of the textile-based inductive coil sensor. The result of the main experiment indicated that the total quality index obtained from the sensor position 'P3', which was located 3cm away from the left side from the center front line on the chest circumference line, was the highest (QI value = 1.30) among the three positions across all the subjects. This finding led us to conclude that (1) the position of the textile-based inductive coil sensor significantly affected the quality of the measurement results, and that (2) P3 would be the most appropriate position for the textile-based inductive coil sensor for heart rate measurements based on the magnetic-induced conductivity sensing principle.