微机控制工频方波交(直)流电源的研究

本文就工频方波交(直)流电源用微机控制进行了试验,筒述了应用计算机控制方波电源主回路电流输出以及焊接时序的方法,并就输出电流的静态精度要求,对可控硅控制角的量化问题进行了分析,给出了相应的控制算法及程序设计的原则与流程图。实验结果表明,利用微机控制该种电源的外特性、脉冲电流,交流正负半波电流比的调节及焊接程序是完全可以实现的,且其静态控制精度及参数调节灵活性均优于普通电子电路控制。     

直流标准功率源校准方法的研究

本文介绍了直流标准功率源的组成,讨论了直流标准功率源的校准方法并给出了不确定度的评定.     

弧焊电源变压器绕组温升快速测量的新方法

针对弧焊电源主器绕组温升检测需要进行绕组电阻值精确测量的问题，本文在恒温源法和双臂电地的基础上，利用计算机速测试物特性，提出了比较法的测量方案，由于孤焊电源器绕组可等效为电感Ｌ与电阻Ｒ的率联电路，当一恒流流过时，电流达到稳定的时间较长，根据阻尼振荡的大批量，Ｒ－Ｌ与一电容Ｃ构成欠阻尼的二阶系统，可使由电感引起的过渡过程的稳定时间缩短在一秒钟以内，从而实现了对绕组温升的快速，准确测量。     

A Precision Stabilized Sine-Wave Source for AC Power Measurements

The design of a stable sine-wave source for error determination of ac-measuring instruments is discussed. The electronic amplitude control circuit has been constructed using standard integrated circuits. The fluctuations of its rms output voltage, observed over the period of 1 h, are 1 · 10-6 peak-to-peak. Since the total harmonic distortion is less than 1 · 10-3, its contribution to the error of the rms value may be neglected.     

A New Method for Measuring the Level Dependence of AC Shunts

We report on a new method for the measurement of the level dependence of the ac–dc difference of current shunts. The method is based on the use of a binary inductive current divider. A method to compare two ac shunts at common ground is described. Measurement results on two 1-A ac shunts, which consist of different numbers of resistors, indicate that the level dependence between 0.5 and 1 A is less than 2 $muhbox{A/A}$ with an uncertainty of less than 7 $mu hbox{A/A}$ from 1 to 100 kHz.      

Method of Measuring the Mass Discharge and Consistency of a Flow Carrying A Suspension

A method is developed for determining the mass discharge and consistency of a pipe flow carrying a suspension under pressure. Mass discharge and consistency are determined by using readings of the power used by the hydraulic dredger which moves the flow.     

智能仪器测量信号功率的不确定度评定模型

针对基于交流采样原理的智能仪器,提出一种新的测量不确定度评定模型。以信号功率测量为例,受硬件条件以及信号频率波动的影响,无法确保同步采样,利用已有测量算法将使测量结果出现误差。将该误差视为系统效应,通过近似处理,提出简单且实用的修正算法。将测量过程中的量化噪声、信号传输中的干扰当作具有已知分布特征的随机变量,利用统计方法,并依据测量不确定度传播定律,评定了经修正算法修正后的测量结果的不确定度。这种先修正系统效应、再评定随机因素造成不确定度的模型,更符合测量过程的实际情况。物理实验和仿真计算均验证了所得结论的有效性。     

Study the Performance of the AC/DC Resistors During Their DC and AC Measurements

Some of traceability chains for the AC resistance measurements are based on AC/DC resistors. In this paper, performance of two types of them with different values has been investigated for their optimum utilization. Tinsley and Cambridge AC/DC resistors have been measured as DC resistors using different measurement methods and as AC resistors at various frequencies. DC direct method using digital reference multimeter is more accurate for the resistance values 1, 10, 100 Ω, and 1 kΩ. For the values 10 and 100 kΩ; measurement results are very near by using the DC direct and ratio methods. At 100 kΩ; representation of the resistance as an equivalent series resistance is not suitable at frequencies above 10 kHz, while for 100 mΩ and 1 Ω; the equivalent parallel representation is not suitable above the same frequency. The uncertainty analysis is also studied for all the obtained results.     

A Vacuum-Free Method for Producing Cubic Titanium Carbide in the Plasma of Low-Voltage Direct-Current Arc Discharge

Technical Physics Letters - The results of a study on the production of cubic titanium carbide in direct-current arc discharge plasma initiated in open air are presented. A feature of the method is...     

电弧法制备碳包覆金属纳米微粒的研究进展

碳包覆金属纳米微粒既可以避免金属纳米微粒的氧化,又能保持其同有性能小变,其潜在科研和应用价值引起了研究者的广泛关注.本文介绍了电弧法制备碳包覆金属纳米微粒的原理,综合评述了碳包覆金属纳米微粒的电弧法制备技术的国内外研究现状,讨论了金属与碳作用后的反应路径,产物类型以及碳包覆金属纳米微粒的形成机理.     

用电位差计法检定直流测温电桥的数据处理方法

直流测温电桥检定规程中用电位差计方法检定测温电桥的数据处理方法不是很详细 ,容易引起歧义 ,有些检定员的数据处理方法甚至会得到不正确的结论。本文针对该数据处理方法谈谈自己的看法     

基于交流测量法的蓄电池内阻测量装置的研究

对传统的几种蓄电池单体电池内阻测量方法如密度法、开路电压法和直流放电法进行了比较分析 ,指出了它们的优缺点。提出了一种新的蓄电池单体电池内阻测量装置 ,该装置以MC6 8332单片机为控制核心 ,采用交流测量法 ,实现了蓄电池单体电池内阻的在线测量。着重介绍了该装置的工作原理以及硬件与软件设计     

The Calibration of DC Resistance Standards by an AC Method

Techniques recently developed at the National Physical Laboratory (NPL) have enabled the zero-frequency (or dc) value of 4-terminal Laboratory Standard Resistors readily to be determined to an accuracy of two parts in 107 from a few measurements made in the frequency band 40 c/s to 600 c/s. A Kelvin double-bridge network is used, the ratio arms consisting of inductively-coupled voltage dividers with an accuracy and discrimination of one part in 107 over the whole frequency range. Experimental results and constructional details of the inductive dividers are given together with the theoretical considerations underlying the principle of the method.     

New Method of Measuring the Discharge and Quantity of One-Phase Media with Measurement Systems Containing Constrictors

The prospects for widening the range of application of variable-pressure-gradient flowmeters with constrictors are analyzed. That range narrowed appreciably with the promulgation of the standards GOST 8.563.1–97 and GOST 8.563.3–97. It is shown that the range of application of measurement systems with constrictors could be broadened within the limits imposed by RD 50-213–80. The capability of such systems would be enhanced by the use of a new method proposed by VNIIMS to measure the discharge, quantity, and energy content of substances.     

浅谈圆弧半径间接测量的数据处理方法

本文作者提出的数据处理方法大幅度地减少了运算量 ,大大提高了效率。给出的圆度计算公式有明显的几何意义     

基于混合采样方法的交流功率转换器

提出了一种混合采样的交流功率转换器 ,叙述了该种采样功率测量的原理 ,推导了功率测量的算法和功率测量误差。通过计算机仿真 ,分析了量化误差对混合采样功率测量方法的影响。最后给出了采用 12 bitA D和D A转换器、频率范围为 4 5～ 6 5Hz时的功率测量实验数据 ,结果表明 :混合采样功率转换器的准确度为 3× 10 - 4,比数字采样方法的测量误差有明显的改善     

New Method for Measuring Statistical Distributions of Partial Discharge Pulses

A new digital detection system is described for measuring pulsating partial discharges (PDs). The PD detection system can continuously record all PD pulses that occur over extended periods of time, with a minimum inter-pulse time separation of 6 μs and a vertical amplitude resolution of 12 bits. Earlier PD detection systems detected PD pulse amplitude and time using complex custom-designed hardware while the present system continuously records the complete electrical waveform that carries the PD pulses using a commercial data acquisition board and extracts, in real time, the time and amplitude information of all PD pulses in software. The current approach considerably reduces the development and maintenance cost of the PD detection system, significantly increases the system portability, and may prove to be a crucial step for transferring the digital PD detection and analysis technology developed in laboratories to industry. The features of the new system are illustrated by the study of dc-excited PD pulses occurring in a point-to-plane gap in air. A new surface-mediated burst mode of PDs is discovered in which a PD pulse has a certain probability to induce another pulse. The probability is determined for several gap voltages and is found to vary strongly with the applied voltage.     

采用高温氮气氛直流电弧放电法制备大直径碳管

在高温氮气氛以及铁、钴、镍的氧化物混合催化剂作用下,采用直流电弧放电法制备了具有不同形貌特征的外径超过100 nm的大直径碳管(LDCTs).透射电子显微镜(TEM)表征结果表明,LDCTs的外径为90~160 nm,内径为70~150 nm,管壁厚度为9~24 nm.高分辨透射电子显微镜(HRTEM)表征结果表明,LDCT的管壁内层为石墨层结构(平均厚度约为4~7 nm),外层为无定形碳结构(平均厚度约为4 nm),管壁间的隔层亦为石墨层结构.能量色散X射线(EDX)谱图和选区电子衍射(SAED)表征结果表明,LDCTs中掺杂有氮和过渡金属元素.初步探讨了LDCTs的生长机理.