Jing Wen

High-resolution current sensor utilizing nanocrystalline alloy and magnetoelectric laminate composite

A self-powered current sensor consisting of the magnetostrictive/piezoelectric laminate composite and the high-permeability nanocrystalline alloys is presented. The induced vortex magnetic flux is concentrated and amplified by using an optimized-shape nanocrystalline alloy of FeCuNbSiB into the magnetoelectric laminate composite; this optimization allows improving the sensitivity significantly as well as increasing the saturation of the current sensor. The main advantages of this current sensor are its large dynamic range and ability to measure currents accurately. An analytical expression for the relationship between current and voltage is derived by using the magnetic circuit principle, which predicts the measured sensitivity well. The experimental results exhibit an approximately linear relationship between the electric current and the induced voltage. The dynamic range of this sensor is from 0.01 A to 150 A, and a small electric current step-change of 0.01 A can be clearly distinguished at the power-line frequency of 50 Hz. We demonstrate that the current sensor has a flat operational frequency in the range of 1 Hz-20 kHz relative to a conventional induction coil. The current sensor indicates great potentials for monitoring conditions of electrical facilities in practical applications due to the large dynamic range, linear sensitivity, wide bandwidth frequency response, and good time stability.

Self-Contained Wireless Hall Current Sensor Applied for Two-Wire Zip-Cords

A self-contained wireless current sensor applied for two-wire zip-cords is proposed in this paper, which consists of a Hall sensor, a wireless module, and an energy harvester along with the power management circuit. The energy harvester is constructed from a current transformer, where an EE-type magnetic core with two arms is specially designed by making a slit in one arm to produce unsymmetric field distributions: the field with low flux density is used for sensing and that with higher flux density for energy harvesting. In the energy scavenging operation, the sensor can generate 4.3 μW with a 217 Ω load resistor under 1 A zip-cord carrying current and supply power for the off-shelf Zig-bee nRF24LE1 wireless module to send one data for a time duration of about 5 min. In current-sensing operation, the sensor exhibits a sensitivity of 0.85 mV/A with a sensed current ranging from 1 A to 130 A.

Temperature dependences of photoluminescence and electroluminescence spectra in light-emitting diodes

The temperature influence on the luminescence characteristics of light-emitting diodes (LEDs) is investigated to reveal the connection of photoluminescence (PL) with photon absorption and electroluminescence (EL) through current injection. By inspecting the PL and EL spectra at identical injection intensities, it has been found that the normalized spectra in PL and EL exhibit obvious similarities in shape and apparent differences in spectral characteristic values. Furthermore, the differences are found to originate from the junction temperatures in diverse injection modes. The observations are conducted on AlGaInP red LED chips.

On sampling a subband of a bandpass signal by periodically nonuniform sampling

Periodically nonuniform sampling (PNS) is employed to sample an interesting component over a subband in a bandlimited signal exclusive of using a physical filter. By controlling the sampling clock and the interpolation algorithm with respected to the interesting component, the sampling and frequency selection can be implemented simultaneously. The sampling rate and order are considered to merely allow the successful reconstruction of the interesting component and the average sampling rate is desirable to be lower than that to sample the entire signal. By analyzing the possible spectral aliasing cases in the selected band, it is found that the number of spectral replicas is at most 2 less than the maximum number in any subband of the signal. In addition, through the analysis, it is found that whatever the support of the selected band is, the average sampling rate has a lower bound. The limitation is primarily determined by the bandwidth of the complete signal.

A high-sensitivity zero-biased magnetoelectric sensor using five-phase laminate composites based on FeCoV nanocrystalline soft magnetic alloy

This paper present a high-sensitivity zero-biased ME sensor consists of FeCoV/Terfenol-D/Pb(Zr1-x,Tix)O3(PZT)/Terfenol-D/FeCoV (FMPMF), whose magnetoelectric (ME) coupling characteristics and ME sensing performance have been investigated. Compared to traditional Terfenol-D/PZT/Terfenol-D (MPM) sensor, the zero-biased ME coupling characteristics of FMPMF sensor were significantly improved. Meanwhile, the induced zero-biased ME voltage of FMPMF sensor shows an excellent linear relationship to ac magnetic field both at the low frequency (1kHz) and the resonant frequency (115.14 kHz). The measured sensitivity at resonance is 1.95 V/Oe and the output resolution is approximately 2.43×10-8T. The proposed FMPMF sensors still have very good performance in the current sensing. The measured results shows an average sensitivity of 1.14 mV/A with highly linear behavior in the current range 1 A to 10 A at 50 Hz. Remarkably, it indicates that the proposed zero-biased miniature ME sensor give the prospect of being able t...

Multi-directional electromagnetic vibration energy harvester using circular Halbach array

In this paper, a multi-directional electromagnetic vibration energy harvester (EVEH) using the circular Halbach array (HA) is presented based on the Faraday’s law of electromagnetic induction. The circular HA is a specific arrangement of permanent magnets which could concentrate the magnetic field inside the circular array by a certain rule, while reduce the magnetic field outside the circular array to almost zero at the same time. The HA could break through the limitation of the related published vibration energy harvesters that could work in only one single direction. Thus, it could optimize the collecting efficiency. The experimental results show that the presented harvester could generate considerable electric output power in all vibrating directions. An optimal output power is 9.32 mW at a resonant frequency of 15.40 Hz with an acceleration of 0.5 g (with g=9.8 m/s2) across a 700-turn coil in the vibrating direction of 90°, which is 1.53 times than the minimum optimal one in the direction of 45°. The...

Effect of adjustable bias voltage on magnetoelectric properties of piezoelectric/magnetostrictive laminate transducer

The magnetoelectric (ME) properties of PZT5/Terfenol-D/PZT8 laminate transducer structure are analyzed and detected for adjusting the bias voltage across PZT5 plate. A control method of the first-order resonant frequency for a magnetostrictive/piezoelectric laminate magnetoelectric transducer structure is proposed. The resonant frequency of the magnetoelectric laminated structure can be adjusted by changing the bias voltage across PZT5 plate. The relationships between the control voltage and the resonant frequencies are analyzed. The resonant frequency of the laminate structure is almost a linear function of the applied dc bias voltage at a small strain. The magnetoelectric coefficient is hardly related to the control voltage. The experimental results verify the theoretical analyses. For a control voltage from -170V to +170V, the adjusted maximum of the resonant frequency is 1 kHz. The ratio of the adjusted resonant frequency to the bias control voltage is 2.94Hz/V.

Time delay estimation method for leak location of buried water distribution pipes

Losses due to leaking is severe in underground pipes, which necessitates studies on techniques for detecting and locating the leaks. The classical adaptive time delay estimation method, LMSTDE, will give a biased estimate when input data are contaminated with noise. This paper develops and analyses a new adaptive filter structure for time delay estimation (TDE), which can eliminate this bias. Simulation results are included to illustrate the superiority of the new model and corroborate the theoretical developments.

Online non-contact fault detection of LED chips

An online non-contact fault detection Method of LED chips is presented based on the photovoltaic effect in diodes. By observing the photo-generated current in the bonding lead frame of a LED chip, the LED chip and its electric connection with the lead frame during packaging are checked. The fault detection principle is described in detail in this paper. By using the method based on the law of electromagnetic induction, the photo-generated current can be measured without any touch. The experimental results show that the method can be easily realized, and thus can be used for online fault detection of LED chips in packaging.

Modal analysis of leakage-induced acoustic vibrations in different directions for leak detection and location in fluid-filled pipelines

The leakage-induced acoustic vibrations are guided by the pipelines and discretized into several modes. Different modes exhibit different dispersive behaviors and generate vibrations of different directions. In this study, the modal characteristics of acoustic vibrations in different directions are investigated theoretically and experimentally. The dispersive natures and the displacement distributions of the guided wave modes in fluid-filled pipelines are analyzed using the guided wave theory. Theoretical analysis predicts that the axial vibrations are dominated by a single non-dispersive longitudinal mode, while the radial and circumferential vibrations are dominated by more than one dispersive modes respectively in the frequency range 0-2.5kHz. Then the experimental investigations convince the theoretical predictions and demonstrate that the axial vibrations are dominated by an individual non-dispersive guided wave with small attenuation rate in the frequency region 0-2.5 kHz. These discoveries demonstrate that, at information acquisition stage, exclusively picking up the axial vibration can significantly improve leak detection and location in the pipelines compared to the conventional detection of the radial vibration.