Using an Arbitrary Six-Port Junction to Measure Complex Voltage Ratios

An arbitrary six-port junction is analyzed as a microwave vector voltmeter, measuring the amplitudes and phase differences of two input signals in terms of power readings taken at the remaining four ports. The junction may be calibrated for measuring the complex ratio of these two signals using a self-calibration procedure which requires no attenuation or phase standards.     

液晶显示数字电压表的设计

在现代检测技术中,常常需要用数字电压表进行现场检测,将检测到的数据送入到微计算机系统,完成计算、存储、控制和显示等功能。因此,设计了一种实用的液晶显示数字电压表,其不仅能够对直流电压进行测量,还可以方便地进行量程的自动转换、与计算机通信等功能,并在液晶显示器上显示。该液晶显示数字电压表采用AT89S52单片机为控制平台,重点设计了量程自动转换、A/D转换和液晶显示等硬件功能电路和系统软件。现场实验显示,该液晶显示数字电压表具有转换速度快、可靠性高、性能稳定等优点,具有很好的使用价值。     

基于单片机的数字电压表设计与仿真

由于纯硬件数字电压表结构复杂,测量精度低,价格高,而在日常使用中,使用频率高,导致万用表经常损坏,故障率高,给使用和维修带来很多不便.为了设计一种高精度数字电压表,采用AT89C52单片机和ADC0809模/数转换相结合的方法,做了大量Proteus仿真实验,获得了普通纯硬件数字电压表无法达到的测量效果.实验结果证明,使用软硬件相结合设计的数字电压表,具有结构简单,测量精度高,故障率低等功能.     

基于数字集成电路的数字式智能电压表的研制

为了解决一般数字电压表自动转换量程、被测电压极性判断、幅度变换、超量程显示及报警信号等智能化问题,采用数字电路芯片,通过数字逻辑控制关系实现电压表使用功能的智能化。阐明了电路设计原理,介绍了电路系统的组成、各部分电路的功能及特点、电路元件的选择、信号处理的过程等内容。通过实物验证,实现了设计功能,并由此设计得到了一台自制数字式智能电压表。     

采用时间标签抗干扰算法的高精度直流电压测量

提出了采用一种改进的移动防脉冲抗干扰平均数字滤波算方法,设计了一种高精度、高性价比的直流电压表。在传统滤波法基础上,算法设计采用时间标签实现了移动防脉冲干扰平均数字滤波的采样值实时更新,从而提高了采样的时效和精度;硬件设计采用高精度的A/D转换芯片HI-7159A。实验证明该电压表的精度最高可达到5 ppm。     

Measured Output Voltages of Piezoelectric Devices Depend on the Resistance of Voltmeter

Piezoelectric mechanical energy harvester (MEH) has been developed as an important emerging variant of piezoelectric devices. Experiments in the literature show that the voltage–time curves of piezoelectric devices encompass both positive and negative characteristics even though the strain in the piezoelectric material is always positive during the applied cycling load. This does not agree with the results predicted by the piezoelectric theory of open circuit. Here, both the experiments and theory are performed to understand this important problem. A zirconate titanate (PZT) MEH is fabricated and the output voltages are recorded with three voltmeters. It is found that the measured voltages depend on the resistance of voltmeter. The peak value of voltage increases with the increase of the resistance of voltmeter, which is contrary to the established knowledge that the measurement results are independent of the instruments used. A theoretical model considering the voltmeter with finite resistance is established. The charge is allowed to go through the voltmeter and switch the directions during increasing and releasing of strain. The results by this model agree well with those from the experiments. The findings suggest that the resistance of voltmeter should be reported for voltage measurement of the piezoelectric devices.     

State-space models for current programmed pulsewidth-modulatedconverters

State-space models are derived for pulse-width-modulated (PWM) converters operating at constant switching frequency under current programmed control. One model neglects the sample-and-hold effect of the current loop and is therefore representative of the traditional approach to modeling current programmed converters. The order of the model is the same as that of the power stage. A second state-space model is derived which incorporates the sample-and-hold effect. The order of this model is two higher than that of the power stage. A comparison of the two models is made which clearly demonstrates the superiority of the second modeling approach. As the models are in state-space form they may be quite readily used in a CAD package for general converter analysis and design, to determine all transfer functions and associated pole/zero locations of interest     

高功率半导体激光器测试系统

利用SGI40-125AAA型程控直流电源、PCI-GPIB卡、电压表、功率计表以及光谱仪等建立高功率半导体激光器测试系统,并在LabVIEW环境下开发了测试软件,通过软件控制直流电源、功率计表等仪器的触发输出、触发输入实现测试设备的同步工作,在保证测试准确性的同时,实现了快速(每个测试点的工作时间约300 ms)的扫描测试,在测试速度上比多个仪器单独测试有了明显提高。可以实现千瓦级连续工作半导体激光器的光功率P、电压V、电光转换效率η、阈值电流、光谱等参数的扫描测试。建立的测试系统准确度高,扫描速度快,测试软件界面操作方便,显示结果直观、全面。     

基于虚拟仪器的多路电压测量的设计与实现

针对在电路测量中需要同时测量几处电压而没有足够的电压表、多点测量操作不便的问题,本文在利用虚拟仪器技术的基础上设计出了一种新型多路数字电压表。该多路虚拟数字电压表除数据采集由DAQ实现外,其他功能均由软件LabVIEW实现。其设计具有灵活性和可扩展性,有利于系统的集成。经过测试,该多路数字电压表性能稳定,能够很好的达到多路测量的目的。     

基于FPGA的新型数字电压表设计

准确可靠的电压测量在大学物理教学中具有重要意义。在研究目前主流电压表设计方案的基础上,提出一种基于FPGA技术的新型数字电压表的设计方法,极大地增强了系统集成度和电路可靠性。以Altera公司高性价比的CycloneⅡ系列EP2C5T144芯片为控制核心,以较高性能的模／数转换器为信号采集芯片,完成电压数据的采集、转换、处理、显示,并实现了档位的自动转换和较宽的测量范围。详细讨论仪表关键电路的设计思路以及关键算法的实现步骤。测试结果表明,该仪表测量误差不大于0．02V,具有较高的测量精度,满足教学实验中的电压测量要求。     

利用波形换算判断交流电压表的检波方式

为了确定某一未知交流电压表的检波方式,根据交流电压表测量电压时的波形换算方法及其适用范围,提出了一种判断交流电压表检波方式的新方法：将正弦波信号和方波信号分别接到所用电压表上,调节信号幅度,使电压表的示值相等,保持这两种信号不变,根据示值得出两种信号的有效值、平均值和峰值并比较其大小。若两者峰值相等,则可判断检波方式为峰值检波;若两者平均值相等,则可判断为均值检波;若两者有效值相等,则可判断为有效值检波。通过实验实例证实了该方法简单可行,进而提供了一种判断交流电压表检波方式的有效方法。     

谈电压、电流测量中的方法误差

由于仪表内耗功率不为零所产生的误差称为方法误差。用电流表、电压表测量电流、电压时存在方法误差。方法误差的大小与电流表、电压表内阻有关。适当选择仪表内阻减小方法误差。如没有适当仪表,可用毫伏表或毫安表与已知电阻构成电流表、电压表达到同样的目的。要避免方法误差只能采用比较测量法,运用补偿法的电位差计可以避免方法误差。     

一种量程自动切换数字电压表的设计

利用单片机AT89C51、A/D转换模块和LED数码显示器,实现了一种具有量程自动切换功能的直流数字电压表,该电压表具有测量精确度高,性能稳定,扩展功能强及显示清晰度高等特点。     

数字电压表容许误差的简便计算方法

为了得到求数字电压表容许误差的简便计算方法,通过对数字电压表显示特点和容许误差表示方法的描述,及对先求绝对误差,后运用相对误差公式求解的方法的介绍及探讨,得出了一种根据数字电压表显示特点提出的新方法--直接由容许误差表示公式得出容许误差,并总结出了一个有效的公式.通过实例验证了该公式的正确性和方便性.     

BSO/fibre-optic voltmeter with excellent temperature stability

A new BSO/fibre-optic voltmeter for measurement of AC voltage from 0 to 500 V has been successfully developed for practical use in various fields. This voltmeter has been given outstanding temperature stability of within ± 0.2% from ?10°C to 85°C by using the electro-optic effect of a 4.7 mm-thick Bi12SiO20.     

Characterization of programmed charge lateral distribution in a two-bit storage nitride flash memory cell by using a charge-pumping technique

In this paper, we use a modified charge pumping technique to characterize the programmed charge lateral distribution in a hot electron program/hot hole erase, two-bit storage nitride Flash memory cell. The stored charge distribution of each bit over the source/drain junctions can be profiled separately. Our result shows that the second programmed bit has a broader stored charge distribution than the first programmed bit. The reason is that a large channel field exists under the first programmed bit during the second bit programming. Such a large field accelerates channel electrons and causes earlier electron injection into the nitride. In addition, we find that programmed charges spread further into the channel as program/erase cycle number increases.     

Peak pulse voltage measurement

Several methods are presently being used for the measurement of pulse voltage. Oscilloscopes are particularly useful because they provide information concerning the shape of the pulse, besides a measure of the peak voltage. In addition to the oscilloscope, several peak voltmeter circuits are mentioned. These include pulse stretching, sampling, and the slideback method. A standard pulse generator is described which provides a calibrated pulse voltage suitable for voltmeter calibration and other uses.     

Power conditioning systems for a magnetically levitated test vehicle

The power conditioning for a magnetically levitated linear-motor propelled test vehicle is described. Control circuits have been developed to provide a constant air gap for levitation and improved damping of lateral motion due to force disturbances. Transistorized magnet drivers supply the required magnet current. A longitudinal control system with programmed limits on the second and third derivatives of the position command allows both precise position stopping and control of acceleration and jerk. A programmable controller is used for sequencing and monitoring the levitation and propulsion systems.     

基于ATmega16单片机的数显电压表设计

针对测试仪器内部直流电平检测的需要,设计了一款以ATmega16为核心,结合电阻分压网络以及反相求和电路的数显电压表。用单片机自带的十位内部ADC进行模拟数据的采集和转换,设计软件精度校准的方法实现对-19.9~+19.9 V正负量程范围内直流电平的精确测量,并用三位数码管显示,超过设定阈值产生报警。实际测试结果表明,该系统误差不超过0.1 V,具有测量精度高、成本低、性能可靠、显示清晰等优点,有着很好的实用价值。     

Multipath tolerant ranging and data transfer techniques for air-to-ground and ground-to-air links

This work addresses data acquisition problems associated with an improved air traffic control system. A mathematical theory of scattering which describes the multipath process is developed. From this model, the optimum signal structure required for ranging and communicating data through the multipath propagation medium is derived. It is shown that the Reed-Solomon Codes have near optimum properties for ranging and data communications. A baseline data transmission system for air traffic control is designed which will accommodate 4000 aircraft per second at the rate of 100 bits per second in a 60 by 120 mile area. The baseline system combines coding with frequency hopping as the best means of combating severe multipath interference. Several coding systems are compared and curves relating error rate to Eb/N0(signal-to-noise energy per bit) for a channel characterized by Rayleigh fading are presented. This paper concludes that a ground-to-air and air-to-ground high capacity data link at a reasonable cost will be feasible for an improved air traffic control system.