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This paper presents a simple yet efficient proximity sensor obtained by combining inductive and capacitive sensing principles. Capacitive proximity sensors based on shielding of electric field are known for detecting presence of humans in its vicinity. Such systems may fail to distinguish the proximity of a human from grounded conductive objects. A novel, cost effective, sensing scheme that uses a...
This paper describes an implantable system for the in vivo measurement of both micromotion and migration in applications such as total hip arthroplasty (THA) and total knee arthroplasty (TKA). The system is based on a modified form of linear variable differential transformer (LVDT) whose null-point is set automatically by means of a self-calibration algorithm. The self-calibration process not only...
We present the results of an analytical study aimed at characterizing the mutual inductance M of Rogowski coils for generic paths of the primary wire and for nonuniform windings. In order to obtain such data, we performed a series of calculations based on the method of the mutual partial inductances and on the application of the Biot-Savart-Laplace law. Finally, we discuss the role of some critical...
A high-accuracy system for calibration of Rogowski coils at frequencies up to 10 kHz, based on a reference current transformer, an I/V converter, and a digital sampling system, is described in the paper. The calibration system has been automated and its performance evaluated. At the frequency of 10 kHz, the calibration system is capable of generating currents up to 100 A. At power frequencies, it...
This paper studies the measurement of magnetism in composite resonator structures. First, we report the main steps of a theoretical analysis developed by the authors in a recent study showing how a composite resonator structure can lead to obtain unusual magnetic behavior in the low and industrial frequency ranges. Then, we describe the single unit-cell setup and the resonator structure adopted for...
The characterization of hybrid aluminium / Carbon Fiber Reinforced Plastics (CFRP) sheets using multi-frequency eddy current sensors is presented in this paper. Both air-cored circular sensors and highly directional ferrite-cored sensors are designed for bulk conductivity measurements and directionality characterization. An analytical model describing the interaction of the circular sensors with the...
In order to reduce the interference from stray flux of adjacent bus bars on the error of heavy current transformer (HCT) which always has a large diameter, the interference mechanism was investigated theoretically in details based on magnetic circuit. It was concluded that there were mainly two interference ways that the stray flux affected the error of HCT, and then it was further verified by experiments...
The short circuit test is a special test for proving the mechanical integrity of a power transformer. Conventionally a change in reactance exceeding 2% after the test is an indication of failure. Concurrent high frequency excitation is shown to be more sensitive method for detecting winding deformation. A dasiabenchmarkpsila layer winding is used to validate the use of high frequency excitation. Axial...
The paper presents the interface designed for wireless data and power transmission. The interface operation idea was tested using build up hardware and software. The sample construction of the temperature sensor embedded with this type interface was designed. Measurements show that the sensor can be wirelessly supplied with energy and is capable to sent data (temperature readings) in 5 cm distance...
This paper is concerned with the characterization of depth profiles defects in metallic structures. Experimental work using giant magnetoresistors (GMR) scanning automatically a metallic plate with eddy currents induced by an excitation coil has been carried out and is described. The results are analyzed in comparison with the simulation results obtained with a commercial finite element model for...
This article presents the results obtained when a Duralumin plate with a slot was scanned with an inductive probe in order to measure the eddy currents' magnetic field. A 3D finite element numeric model was used to preview the eddy current distribution. An analysis of the produced data and of the consequences of using image filters is included.
In this work a novel inertial sensor is presented, which can be used as a low band accelerometer, a vibration sensor or an inclinometer. The device consists of a glass plate filled with deionized water surrounding a small volume of ferrofluid; a permanent magnet is used to fix the position of the ferrofluidic mass in a compliant position. The effect of an external stimulus can be estimated by measuring...
A tilt-sensitive measuring system exploiting a flux-gate sensor is described. The sensing configuration has been investigated using an electromagnetic modelling software first. Then, the prototype characterization has shown a system sensitivity up to 2.3491 V/deg and an Integral Non Linearity (INL) down to 1%.
This paper discusses about the spatial resolution performance on RTD-fluxgate prototypes having different ferromagnetic core geometry. This is of major importance when the magnetic target signal source is very confined in space and therefore the ability of the sensor to correctly point the target is dictated by its ability to resolve the target position. The readout strategy is based on the use of...
This paper presents the measurement of decarburization of steel rods with an electromagnetic sensor using an analytical model. 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...
Texture based segmentation is a topic where a lot of different approaches lead to more or less satisfying results. In general all of them try to match a particular feature or a feature vector which describes the analyzed region. Subsequently a threshold or threshold vector is applied and a texture class is assigned to the region. This paper describes how data mining algorithms can be used advantageously...
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