Ultrafast response of As-implanted GaAs photoconductors

The photoconductive response of an optoelectronic switch fabricated from GaAs implanted with arsenic ions is measured to have a duration as short as 0.7 ps and a relaxation time as fast as 0.5 ps. The switching efficiency and relaxation time of the photoswitches using the As-implanted GaAs substrates are determined to be comparable to photoconductive devices employing GaAs grown by low-temperature molecular-beam epitaxy (LT-GaAs). For high dc-bias values, persistent photocurrent tails from transient leakage currents are found to be very prominent in bulk GaAs devices that were implanted with 10¹⁶ cm^-2 arsenic ions at 200 keV. This behavior has been determined to arise from substrate leakage current underneath the thin implanted layer, which recrystallizes and exhibits, as does LT-GaAs, arsenic-precipitate formation after annealing. In order to reduce this leakage current, multiple ion dosages with various implantation energies have been implemented. An epitaxial GaAs layer has also been implanted with arsenic ions, isolated from its semi-insulating substrate, and bonded onto a fused silica wafer in order to verify that the persistent tail response from the photoconductive switches was not actually due to the implanted region of the GaAs     

Picosecond-domain radiation pattern measurement using fiber-coupledphotoconductive antenna

The photoconductive terahertz measurement technique was used for measurement of the radiation pattern from thick metal slits. Picosecond pulses were generated and detected by an ultrafast optoelectronic technique using a femtosecond pulse laser and a subpicosecond photoconductor. Photoconductive sampling measurements of the polarization-dependent diffraction of the picosecond electromagnetic pulses showed the highly polarized radiation characteristics of the photoconductive probing antenna (PCPA) compared with the finite-difference time-domain simulation. The radiation patterns from the slits were measured using a fiber-coupled PCPA. Investigation of the spatiotemporal radiation pattern from a thick metal slit shows the usefulness of the measurement set-up for time-domain and broadband antenna characterization. Together with the time-domain radiation pattern, the frequency-domain radiation pattern from the experimental transient response is presented in both amplitude and phase. It is demonstrated that the time-domain radiation pattern measurement using the photoconductive terahertz radiation technique is a promising characterization method for millimeter-wave and submillimeter-wave antenna time-domain testing     

500kV变电站开关操作瞬态电场测量与研究

变电站断路器和隔离开关操作会产生瞬态电场。该文对国内正在调试的两座500kV变电站开关操作产生的瞬态电场进行了测量。这是国内首次进行现场测量。本次测量使用三维球形有源瞬态电场探头，该探头最大可测48kV/m。测量项目包括隔离开关分合空载母线和短线、断路器合长线和投空载变压器等。对测量的数据进行分析获得关于断路器和隔离开关操作产生瞬态电场的一些重要特征。这些结果对变电站电磁干扰分析和保护与控制设备抗扰度研究具有重要的理论意义和实用价值。     

Eddy current testing by upgraded microloop magnetic sensor array

A micro-eddy current testing (ECT) probe, which consists of a planar microloop inductive magnetic sensor array and a pancake-type exciting coil, was developed to upgrade the ECT technology, especially as it is used for inspecting steam generator tubing in a pressurized nuclear power plant (PWR). Eddy currents and resultant magnetic fields are perturbed due to a flaw in a conductor. The flaw is detected via perturbation of the electromotive force (EMF) and phase from the array. Flaws manufactured by electric discharge machining in INCONEL 600 planar specimens, the thickness of which was 1.25 mm, were detected and reconstructed by using stacked database and simplified algorithm. Even an outer-edged 10 percent flaw could be detected. Measured EMF and phase signals were compared with numerical results obtained by using a three-dimensional eddy current and field analysis code and then verified. The experiment confirmed that the spatial resolution of detection of the micro-ECT probe is superior to that of the conventional pancake-type ECT probe. Finally, it was demonstrated that it is possible to establish the same measurement speed using the micro-ECT probe as it is by using the pancake-type ECT probe.     

数字式无线工频电场测量仪的研制

有源电场探头在高压电场测量中应用广泛.笔者说明了球形和柱形有源电场探头的测量原理,计算了圆柱形探头对电场的畸变,并介绍了一种有源无线数字式工频电场测量系统.该系统所用的圆柱形探头尺寸小(Φ=26 mm,H=13 mm),通过2.4 GHz无线信号通讯,可在计算机或手机屏幕上直接读出被测点的场强值,并可看到被测点电场的波...     

便携式工频电场测量装置的设计

为了了解设备表面和内部的工频电场,从而更好地研究设备运行的状态及优化改进设备,笔者介绍了一维球型电场传感器的测量原理,设计了一种基于C8051F410单片机的便携式工频电场测量装置,讨论了不同形状及规格电场探头对测量结果的影响并完成了电场探头的选型。在500 kV交流输电线下方和实验室简化同心圆球电极内使用该装置与国外标准仪器进行了对比测量,现场测试结果表明该装置测量数据与国外仪器相比具有较大的相关度,能准确地测量电力系统工频电场,具有很好的实用性。     

真空触发开关导通瞬间电场强度的计算

提出了一种高压真空触发开关导通瞬间高频脉冲电流的测量方法,并构建了相应的测量系统,实验测得了开关导通瞬间的脉冲电流波形.依据电流波形,我们计算出了开关周围的电场强度,为进一步研究真空触发开关的导通原理及其应用提供了实验依据.     

高压隔离开关触指镀银层现场测厚技术开发

高压隔离开关触指镀银层的厚度是影响其电接触性和可靠性的重要因素。利用手持式XRF合金分析仪开发了一种针对高压隔离开关触指镀银层的现场测厚技术,测量方法简单,结果准确,具有推广价值。     

Electromagnetic 2/spl times/2 MEMS optical switch

This paper presents the design, fabrication, and measurement results of a 2/spl times/2 microelectromechanical systems optical switch. The switch comprises an electromagnet and lensed fibers assembled with a micromachined movable vertical micromirror. The optical switch utilizes the out-of-plane motion of the vertical micromirror actuated by electromagnetic force compared to the comb-driven linear actuation achieved by the electrostatic force. At a wavelength of 1550 nm, the insertion loss of 0.2-0.8 dB and the polarization-dependent loss of 0.02-0.2 dB are measured. The switching time is 1 ms. A novel method of realizing a latchable optical switch using an electromagnetic actuator is also provided and verified. The latch mechanism is based on the latchability of the electropermanent magnet instead of the mechanical one using conventional arch-shaped leaf springs.     

平行板型三维脉冲电场传感器的研制

宽频带传感器是脉冲电磁场测量的关键设备之一,目前用于脉冲电场测量的传感器大都是单极化形式,只能测量半空间、单极化方向上的电场。为此,研制了一种可用于脉冲电场测量的三维平行板型结构传感器,它由三维电场天线和光发射机组成,与相应的光纤传输系统配合,可以对三维脉冲电场进行同时、全空间测量。应用FDTD法对三维电场测量天线模型进行了数值模拟,重点分析了三维天线的极间耦合、三维场分量的合成与频率特性。计算结果表明,平行板型三维电场天线可以满足脉冲电场测量要求。根据数值模拟的结果实际制作了三维电场传感器并对该传感器进行了实验验证。测量结果表明,该三维电场传感器的性能达到了设计要求。     

DC-probes for electric field distribution measurements

The principles of how DC fields can be measured using an isolated probe coupled by fiber optics to a separate receiver are discussed. The construction of some practical systems is described, with attention given to induced current, voltage, power, and dipole systems. The electric fields around a full size wall bushing energized to 600 kV in rain were measured. The results of this measurement and other measurements are presented, demonstrating the usefulness of isolated DC field measurements     

A Technique for Pressure Measurement in the Active Electrical Zone of a Wire-Cylinder Electrostatic Precipitator

Probe techniques are discussed which have proven useful in the measurement of the current induced pressure distribution in the active electrical zone of a wire-cylinder electrostatic precipitator. The cylindrical electrode configuration is somewhat unique in that the pressure distribution is exactly known in the case of negligible axial flow and thus provides a check on the experimental technique. The measurement strategy combines alignment of the probe on an equipotential surface, control of probe current drainage to a level consistent with the probe's size and location in the field, and use of a guard electrode near the probe insertion point. Pressure measurements made with probe electrical characteristics indicating a minimally perturbed electric field are in close agreement with analytical prediction, and the experimental techniques appear to be applicable to other types of flow measurement in cylinder and duct precipitators.     

真空开关真空度在线检测系统的设计与实现

利用自行开发的电场探头研究了真空开关屏蔽罩电位的有效值与真空度之间的关系，得出了相应曲线，系统通过测量真空开关屏蔽罩的电位相对正常值的变化情况，运用趋势检测方法和比较算法对检测数据进行综合分析，消除了由于电磁环境变化引入的误差．该方法由于综合考虑了真空开关屏蔽罩处电场的有效信息，诊断性能得到了较大的改善，为真空开关的在线检测提供了科学依据．     

同塔双回高压直流线路地面合成电场的计算方法

我国计划在实际工程中采用同塔双回高压直流线路,由于该类线路在世界上无工程应用先例,需要研究其地面合成电场的有效计算方法,以满足工程设计和环境保护需求。考虑极导线对地距离不同和极导线布置方案对每一极导线起晕电压的影响及正负极导线起晕场强的差别等因素,提出一种计算同塔双回高压直流线路地面合成电场的方法。利用同塔双回直流模拟试验线段,对极导线按不同方案布置时的地面合成电场进行测试,并采用该文方法对地面合成电场进行计算。结果表明,采用该文方法计算极导线按不同方案布置时同塔双回直流线路的地面合成电场,其分布规律与实测结果基本吻合;地面最大合成电场计算值与实测结果基本一致。     

基于MSP430的高压开关柜火灾预警系统的研制

采用红外热电堆为温度传感器,设计了一种基于MSP430单片机的高压开关柜火灾预警系统,该系统由温度传感器,信号调理电路,单片机,RS485网络和上位机组成。系统能实现对多个开关柜内接点进行温度实时测量,并具有温度预警功能,其测量误差不超过1℃。通过RS485网络,该系统能够与变电站综合自动化系统相连,实现远程监测。该系统为高压开关柜提供了超温预警,有效地预防了电气火灾的发生。     

基于TMS320F2812和C8051F040的目标测量系统电模拟器研制

本文应用TMS320F2812DSP和C8051F040微处理器,对某型卫星地面电联试系统中的目标测量系统电模拟器进行开发,以实现目标测量系统电模拟器的电接口和通信协议与目标测量系统原型样机的完全一致,同时通过应用软件开发来实现各目标测量系统电模拟器的测量功能。基于TMS320F2812DSP和C8051F040单片机所开发的目标测量系统电模拟器具有处理功能强大、接口功能丰富、软件开发效率高、通用性强等优点。最后将所研制的目标测量系统电模拟器接入某型卫星地面电联试系统中,完成了该卫星地面电联试系统的飞行任务演示闭环试验,从而为某型卫星目标测量系统的方案论证提供了有效的实验和验证平台。     

GIS very fast transients overvoltage testing using electric field measurements

ABSTRACT

The Insulated problem, which is caused by very fast transients overvoltage (VFTO) associated with the switch operation of GIS (Gas Insulated Substations), is becoming increasingly serious. According to the linear relationship between electric field intensity and the voltage of the circuit, in this paper describes a method for measurement of VFTO based on electric field measurement. To measurement of VFTO, the data, which is collected by electric field sensor on basis of the electric field change along with the voltage change in GIS switch circuits, will be used for examining the relationship between electric field intensity and the voltage of the circuit, as well as be used for seeking the experimental best-fit. Then, this paper firstly makes theoretical modeling of VFTO, make numerical simulation calculation. Meanwhile, the response characteristics and the frequency band of the electric field sensor were tested by sine sweep test and square-wave response test. Especially, the sensor has the low-frequency cut-off frequency (<20 Hz) and the high-frequency cut-off frequency (>134 MHz). After that, the paper will carry out the high voltage amplitude measurement experiment. Finally, according to the assessment by building a simulation test platform based on theoretical modeling to measure VFTO, the finding demonstrates that the sensor can measure the very fast transient overvoltage effectively.     

Time-domain magnetic field waveform measurement near printed circuit boards

This paper describes a time domain magnetic field measurement process for measuring magnetic fields near printed circuit boards (PCBs) with a loop probe. In carrying out these measurements, the loop probe needs to be calibrated in the frequency domain. In this process, a microstrip line with a teflon substrate serving as the standard magnetic field source is employed as a means of calibrating the probe. The standard magnetic field intensities of the line are calculated by using an approximate equation obtained from Ampère's law to simplify the calibration. The sensor-factor of the probe obtained from this method agrees with that obtained through the use of a standard G-TEM cell in 2 dB at frequencies below 1 GHz. The waveforms of magnetic fields near a PCB having a four-layer construction are measured using a 10 mm diameter loop probe as the calibrated magnetic field sensor. The generation of magnetic field waveforms causing the radiated emission from the PCB is found to depend on the circuit operating conditions. Our results clarify the fact that the time domain magnetic field measurement process is an effective tool for analyzing the sources of emission radiated from PCBs and for investigating the radiation mechanism. © 1998 Scripta Technica, Electr Eng Jpn, 125(4): 9–18, 1998     

基于锁相技术的感应电流检测方法研究

针对电引爆装置在复杂电磁辐射环境中会通过电磁耦合产生感应电流,导致电引爆装置失火的问题,提出了一种基于锁相技术的非接触式感应电流检测方法.采用基于隧道磁阻效应的电流探头,根据电磁感应原理,结合锁相技术对隧道磁阻探头的输出信号进行分析,从而对感应电流进行实时监测,避免失火;得出基于锁相技术的非接触式感应电流检测方法相比于...