共查询到20条相似文献,搜索用时 0 毫秒
1.
《Vehicular Technology, IEEE Transactions on》1978,27(2):65-68
The measurement of vehicle magnetic moments and the results from use of a fluxgate magnetic sensor to actuate a lighting system from the magnetic fields of passing vehicles is reported. A typical U.S. automobile has a magnetic moment of about 200 A-m2(Ampere-meters2), while for a school bus it is about 2000 A-m2. When the vehicle is modeled as an ideal magnetic dipole with a moment of 200 A-m2, the predicted results from an analysis of the sensor-vehicle geometry agree closely with observations of the system response to automobiles. 相似文献
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《Solid-State Circuits, IEEE Journal of》1983,18(4):426-428
The authors present a novel, fully integrated magnetic field sensor made in the standard, polysilicon-gate CMOS technology. The circuit shows a sensitivity of 1.2 V/T with 10 V supply voltage and 100 /spl mu/A current consumption. The circuit consists of a pair of split-drain MOS transistors in a CMOS-differential amplifier-like configuration. 相似文献
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《Electron Devices, IEEE Transactions on》1984,31(7):996-999
We present two-dimensional numerical solutions of the coupled, nonlinear, partial differential equations governing the electric potential, carrier drift, diffusion, generation, and recombination in a finite semiconductor slab in the presence of a magnetic field. This enables device modeling for general geometries, doping levels, and injection conditions, where the effect of the magnetic field cannot be expressed simply in terms of Hall voltage, Lorentz deflection, or magnetoconcentration. 相似文献
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Location and calculation-free node-scheduling schemes in large wireless sensor networks 总被引:1,自引:0,他引:1
In wireless sensor networks that consist of a large number of low-power, short-lived, unreliable sensors, one of the main design challenges is to obtain long system lifetime without sacrificing system original performance (sensing coverage and sensing reliability). To solve this problem, one of the potential approaches is to identify redundant nodes at the sensing interface and then assign them an off-duty operation mode that has lower energy consumption than the normal on-duty mode. In our previous work [J. Wireless Commun. Mobile Comput. 3 (2003) 271; Processing of ACM Wireless Sensor Network and Application Workshop 2002, September 2002], we proposed a node-scheduling scheme, which can provide a 100% sensing coverage preservation capability. This, however, requires each node to be aware of its own and its neighbors’ location information. Also, in that scheme, each node has to do accurate geometrical calculation to determine whether to take an off-duty status. In this paper, we propose and study several alternative node-scheduling schemes, which cannot completely preserve the original system coverage, but are nonetheless light-weighted and flexible compared with the previous one. Our simulation results compare these schemes with the previous one and demonstrate their effectiveness. 相似文献
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提出了一种检测三维磁场的真空微电子磁敏传感器。该传感器采用Spindt阴极阵列作为电子源,阳极分为五个区域,以便检测发射电子在磁场作用下的偏移。通过不同阴极电压下电子束流的偏移量的国赤出器件所在位置磁场的三个分量。对传感器的灵敏度和误差进行了模拟计算,并研究了它们与阳极电压、阴-阳极间距及阳极电压变化步长的关系。结果表明该传感器的灵敏度约为800%,相对误差为3%。 相似文献
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New results on the polarization properties of a matched fiber-coil (i.e. one beat length per turn) immersed in a magnetic field are described. It is shown that both components H y and H z, perpendicular to the coil axis, can be simultaneously measured. Sensing coils of 1-cm diameter, with multiple turns of fiber, were fabricated. Using 100-turn heads, a sensitivity of 0.01 G was achieved for the vectorial fiber sensor 相似文献
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Stuchly M.A. LePoncher H. Gibbons D.T. Thansandote A. 《Electromagnetic Compatibility, IEEE Transactions on》1991,33(4):275-280
An active magnetic field sensor consisting of an electrically small loop, two ferrite core transformers, and a balanced amplifier with a low input impedance is suitable for measurements of fields, in a broad range of frequencies, and transients. The sensor provides a flat transfer function from approximately 600 Hz to 200 MHz (3 dB roll-off frequencies) and high-fidelity reproduction of pulses with a risetime of 2 ns. The sensor can be used to measure fields from less than 0.2 mA/m to approximately 0.2 A/m. The sensor has a minimal response to the electric field (at least -20 dB). The sensor's dimensions are 6 cm×6 cm, and the electronic circuitry is contained in a box of approximately 5 cm×8 cm×3 cm 相似文献
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《Electron Devices, IEEE Transactions on》1972,19(11):1178-1180
The sensor is a gas-filled tube of the Geiger-Mueller type, in which an electron emitted from a photocathode is accelerated by an applied electric field to cause ionization of the fill gas. Although the operating principle is not new, this tube differs from others in that the cathode consists of a semitransparent layer of metal on the inside of the cylindrical tube envelope, which is applied by sputtering after filling and sealing. Used as a cathode during sputtering, the anode consists of a pin along the axis of the tube, providing the cylindrical symmetry for uniform wide-angle viewing. The performance of the tube is compared with that of a tube of the same external dimensions, but with more conventional parallel wire electrodes. The counting rate for the sputtered tube was a factor of 10 higher than the conventional tube, due to the larger sensitive cathode area, and uniform over 360° in a plane perpendicular to the tube axis, due to cylindrical symmetry. The counting rate for the sputtered tube was 2000/min in response to a flame 7 ft away burning natural gas at the rate of 138 cm3/min. 相似文献
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A maximum likelihood (ML) method is developed for estimation of direction of arrival (DOA) and associated parameters of narrowband signals based on the Taylor's series expansion of the inverse of the data covariance matrix R for large M, M specifying number of sensors in the array. The stochastic ML criterion function can thus be simplified resulting in a computationally efficient algorithm for DOA estimation. The more important result is the derivation of asymptotic (large M) expressions for the Cramer-Rao lower bound (CRB) on the covariance matrix of all unknown DOA angles for the general D source case. The derived bound is expressed explicitly as a function of snapshots, signal-to-noise ratio (SNR), sensors, separation, and correlation between signal sources. Using the condition of positive definiteness of the Fisher information matrix a resolution criterion is proposed which gives a tight lower limit on the minimum resolvable angle 相似文献
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提出了一种基于硅桥结构的MEMS磁场传感器结构。其结构由制作在硅桥敏感膜表面的惠斯通电桥和在膜中间沾上铁磁体制成。当传感器处于磁场中时,铁磁体在外磁场中磁化产生磁力,磁力会使硅敏感膜弯曲从而引起压阻改变进而使惠斯通电桥产生电压输出以达到测量磁场的目的。文章通过有限元软件仿真对铁磁体的尺寸进行了优化。实验结果和理论结果较接近。实验测得该传感器最大灵敏度为48mV/T,分辨率为160μT,该传感器可以用来进行强磁场的测量。实验结果结果表明:传感器的重复性和动态响应时间分别约为0.66%和150ms。 相似文献
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小型化相机是支持低成本微型飞行器或微小卫星对地观测等多项应用的关键设备,由此提出了一种高分辨率大面阵的小型化成像系统。首先预估了该成像系统用于目标观测的像元分辨率和幅宽。然后阐述了该系统的电子学方案,对其中的关键芯片OV14825的工作原理进行了介绍,并分析了基于FPGA的串行差分数据接收转发的软件设计。最后基于设计的相机样机开展了成像实验,在13m成像距离条件下获取图像分辨率优于0.5mm,而且图像细节丰富,层次分明,证明该方案切实可行。高分辨率大面阵微型相机具有很好的应用价值。 相似文献
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A MEMS piezoresistive magnetic field sensor based on a silicon bridge structure has been simulated and tested.The sensor consists of a silicon sensitivity diaphragm embedded with a piezoresistive Wheatstone bridge,and a ferromagnetic magnet adhered to the sensitivity diaphragm.When the sensor is subjected to an external magnetic field, the magnetic force bends the silicon sensitivity diaphragm,producing stress and resistors change of the Wheatstone bridge and the output voltage of the sensor.Good agreeme... 相似文献
16.
《Optical Fiber Technology》2014,20(2):100-105
Novel magnetic field sensor based on magnetic fluids infiltrated dual-core Photonic Crystal Fibers (PCFs) is proposed in this paper. Inside the cross-section of the designed PCFs, the two fiber cores filled with magnetic fluids (Fe3O4) are separated by an air hole, and then form two independent waveguides with mode coupling. The mode coupling under different magnetic field strength is investigated theoretically. A novel and simple magnetic field sensing system is proposed and its sensing performances have been studied numerically. The results show that the magnetic field sensor with 15-cm PCFs has a large sensing range and high sensitivity of 4.80 pm/Oe. It provides a new feasible method to design PCF-based magnetic field sensor. 相似文献
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In this paper, magnetic fluid (MF), a new type of optical functional nanomaterial with interesting optical characteristics under the external magnetic field, is adopted to form a novel fiber-optic magnetic field sensor. The proposed sensor is based on Mach-Zehnder interferometer (MZI) and has a multimode-singlemode-multimode (MSM) fiber structure. The MSM structure was fabricated by splicing a section of uncoated single mode fiber (SMF) between two short sections of multimode fibers (MMFs) using a fiber fusion splicer. The magnetic field sensing probe was made by inserting the fiber-optic structure in an MF-filled capillary tube. Variations in an external magnetic field is seen to cause changes in the refractive index of MF. This tunable change in the refractive index with magnetic field strengths between 0.6 mT to 21.4 mT produces a shift in the peak position of the wavelength. The shift of the valley wavelength with magnetic field intensity has a good linearity of up to 99.6%. The achieved sensitivity of the proposed magnetic field sensor is 0.123 nm/mT,which is improved by several folds compared with those of most of the other reported MF-based magnetic field sensors. Furthermore, we build the corresponding circuit-based measurement system, and the experimental results show that the voltage change indirectly reflects the change of the external magnetic field strength. Therefore, this provides the potential to fiber-based magnetic field sensing applications. 相似文献
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《Electron Devices, IEEE Transactions on》1984,31(3):286-291
We report a novel integrated magnetic field sensitive device. Its structure is reminiscent of the bipolar transistor, but its operation is essentially that of a magnetodiode: a reverse-biased p-n (collector) junction plays a role similar to that of the high recombining surface of classical magnetodiodes. The device can be manufactured in standard bulk CMOS or bipolar technology. Sensitivity up to 25 V/T at 10-mA current is achieved. Voltage-current characteristics shows saturation and negative resistance regions, which are explained by JFET and UJT effects, respectively. 相似文献
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