On a new principle of a smart multisensor based on magnetic effects

In this paper, a new principle of a smart sensor is proposed, based on three different magnetic effects or operational modes, using the same sensor topology, which consists of a magnetic wire as sensing core, two coils as excitation or search means, and two electric contacts at the ends of the magnetic wire. The magnetic effects currently involved are magnetostriction, magneto-impedance and re-entrant flux reversal. Operating the sensor in these three different modes separately and sequentially, one can obtain the response of the sensor related to three different physical quantities, such as stress, temperature, and field. This paper refers to the first experimental results based on this principle, thus initiating the research work in this field. It has been experimentally observed that the total output of the sensor in each one of the three different modes is equal to the product of each corresponding physical quantity function concerned, provided that a given threshold of the ambient field and preloaded stress is used to bias the sensing element. Therefore, the three unknown parameters of stress, temperature, and field can be determined from a 3/spl times/3 matrix equation. Other magnetic effects may also be involved. Furthermore, other physical quantities may also be determined, such as position, pressure, load, etc.     

New Magnetic Field Sensor Based on Combined Flux-Gate/Hall-Effect Arrangement

A novel planar magnetic field sensor is presented that is based on a combined flux-gate/Hall-effect arrangement capable of measuring the three components of a three-dimensional quasi-static magnetic field. The proposed device involves a thin, isotropic, circular magnetic core, the magnetization of which is driven to saturation by means of a rotating excitation-field, produced by four printed planar coils. That way, the core magnetization rotates, without Barkhausen jumps inducing a flux-density change that is sensed by a Hall device positioned at the edge of the core. The presented sensor consists of a discrete Hall device, electronic modulation-demodulation circuitry and a circular amorphous core packaged on a printed circuit board (PCB), constructed as a proof of concept for the proposed magnetic field measuring method.     

Evaluation of Barkhausen Noise and Magnetoacoustic Emission Signals Properties for Plastically Deformed Armco Iron

The paper presents the results of the investigation of the influence of different modes of plastic deformation on the magnetoacoustic properties of Armco iron. Two sets of samples have been investigated—the first one consisted of preannealed samples that had been subsequently cold rolled, and the second one consisted of samples cut out from commercially available Armco plates, subjected to tensile loading. The process of cold rolling leads to the broadening of the envelopes and to the appearance of the third central peak [attributed to the domain-wall (DW) pinning]. In the case of the nonannealed samples, the Barkhausen envelope for the as-received sample reveals one, broad maximum that is transformed by the following tensile deformation initially into two and then three peaks. In order to detect subtle changes of the Barkhausen noise (BN) properties, a multiparameter [fast Fourier transform (FFT), pulse height distribution, wavelet transform] analysis was performed. As for the magnetoacoustic emission (MAE) signal, both deformation modes result in visible increase in peak separation as well as in the increase of the MAE intensity. As for the peak separation, it can be understood as the result of both the increase of the coercivity of the samples and the decrease of the slope of the B(H) loops since the MAE signal is generated mainly during creation/annihilation of DW occurring mainly at the “knee” regions of the B(H) loops.      

Energy efficiency improvement of water pumping system using synchronous reluctance motor fed by perovskite solar cells

Perovskite solar cells (PSCs) are in the forefront of third-generation of photovoltaics and gained a lot of attention as a very promising green technology toward direct solar energy conversion to electricity. PSCs are fabricated following solution-processed techniques at low temperature and they present high power conversion efficiency exceeding 25%, enabling them to be attractive alternative to the silicon-based devices. This research work proposes an efficient and cost-effective photovoltaic (PV) pumping system based on PSCs. For this purpose, lab-scale PSCs were fabricated and their characteristics were determined. In parallel, the geometry of a synchronous reluctance motor (SynRM) driving a 350 m³/day water pump was optimized for maximizing the output power, while minimizing the torque ripple simultaneously. In addition, a perovskite solar array feeding the SynRM via an inverter was designed and implemented. The inverter was properly regulated by a control system which optimized the maximum available power of the PSCs solar array and the SynRM characteristics. Finally, laboratory measurements were performed, including a power generator simulating the behavior of the PSCs array feeding the SynRM. The obtained results confirmed the experimental validation of the proposed approach.     

Force sensors based on distortion in delay lines

The principle of operation of force sensors based on distortion in delay lines type of sensor is the distortion of an acoustic signal, in a pulse-excited magnetostrictive delay line due to a force applied at any point between the point where the pulse is generated and the receiving coil. A conductor orthogonal to the delay line is used for pulsed current transmission and its distance is fixed with respect to the delay line. The input and the output of the system are the applied force on the delay line support and the amplitude of the detected output V _o, respectively. Under fixed amplitude of the pulsed current, V_o has a maximum value under zero input and decreases as the applied force increases. Experimental results show that the response of the sensor is a monotonic, exponential function of the applied force. A method is also proposed, according to which an integrated sensor array could be made based on this principle     

Explosively Consolidated Powder-In-Tube MgB$_{2}$ Superconductor Aided by Post-Thermal Treatment

A MgB₂ superconductor was prepared from Mg flakes or powders and B powders using the powder-in-tube technique with explosive consolidation. Compaction of Mg and B powders resulted in a two-phase alloy, due to the relatively low temperature developed during compaction as well as the very short duration of the process. Formation of MgB₂ was obtained after subsequent heat treatment in argon atmosphere at a maximum temperature of 950degC.