混合型高电压超级电容器的研究

通过优化组合电解电容器的阳极和电化学电容器的阴极,以Ta/Ta2O5为阳极,活性炭为阴极,研制了一种单元工作电压为100V的混合型超级电容器。该电容器与超级电容器相比较,工作电压得到了提高。测试表明其具有高储能密度和快速充放电的能力,频谱阻抗(EIS)分析显示其具有优良的阻抗特性和频率特性。     

用安捷伦4395A扩频测量铝电解电容器频率特性

频率特性是电容器重要的电气特性,它是设计电路的基础,可通过阻抗分析仪获得。研究采用Agilent4395A阻抗分析仪扩频测量铝电解电容器频率特性及其电气参数的方法具有实际意义。实测证明,用Agilent4395A扩频测量铝电解电容器频率特性是有条件的,测量结果是准确的。     

交流量子电阻传递电桥的研制

国际单位制变革后,阻抗参数需溯源至量子化霍尔电阻,其中将交流量子电阻传递到被测交流标准电阻是主要难点之一,需要研制10^–8量级的阻抗电桥,而常规精密阻抗电桥的准确度在10^–4至10^–5量级,仅有四端对同轴阻抗电桥在理论上能实现10^–8量级的准确度,但结构十分复杂,需要多次平衡,其过程存在相互影响,使平衡收敛十分缓慢,测量效率很低,同时存在频点单一的问题。针对以上不足,提出微差补偿网络隔离供电和可调虚部补偿输入比例的措施,大幅提高电桥收敛速度,并实现用于交流量子电阻传递的多频点四端对同轴阻抗电桥。同时给出四端对同轴阻抗电桥的校验方法和整体验证的标准器,验证结果表明：研制的交流量子电阻传递电桥10∶1的测量不确定度达到10^–8量级。     

新概念阻抗器

<正>笔者提出建立新型阻抗器的构想和理论。(1)抛物线电极四端电阻器,其电流引线和电压引线的结点位于电阻体内,严格满足四端电阻的定义。(2)三角形电容器具有三夹角电容之和为常数的特点,提高了稳定性。(3)同轴孪生互感线圈具有等电位梯度保护空间,提高了耦合     

射频阻抗标准器量值定标及溯源技术研究

射频阻抗标准器是验证射频阻抗测量仪器计量性能的关键装置,可建立仪器内部存储的基准数据与国家阻抗基准的溯源关系。本文分析了10cm同轴无支撑空气线、短路标准器、开路标准器和50Ω阻抗匹配标准器的结构,基于传输线理论,运用等效、样条插值等算法,对射频阻抗标准器进行定值,并对定标值进行不确定度评定,建立了射频阻抗标准器量值与物理尺寸及国家微波阻抗基准的溯源关系,解决了目前射频阻抗量值溯源和量值传递的交叉重叠问题。     

铁镓合金阻抗频率特性测量与分析

通过测量铁镓合金在不同磁场下的阻抗频率特性,确定铁镓合金的柔顺系数S33和磁机械耦合系数K33,为铁镓合金在致动器和换能器等系统中的应用提供设计参考。分别测量棒状样品和片状样品在不同磁场下的阻抗频率特性,确定共振频率和反共振频率,计算S33和K33,并将片状样品与棒状样品特性参数进行对比分析。结果表明,片状和棒状样品的S33和K33随磁场的增加先增大后减小,在同一磁场下片状样品的柔顺系数小于棒状样品,片状样品的磁机械耦合系数大于棒状样品。随磁场的增加先增大后减小，在同一磁场下片状样品的柔顺系数小于棒状样品，片状样品的磁机械耦合系数大于棒状样品。     

基于TEM小室的探头校准系统不确定度评定

TEM小室是一个常用的电磁场发生装置,使用TEM小室组建场强探头校准系统,可以对射频电磁场探头进行校准。针对一套300 kHz～100 MHz频段的场强探头校准系统进行分析,以磁场探头为例,给出该频段范围内5个频点校准的不确定度评定结果。该不确定度分析过程考虑了TEM小室内空间波阻抗,以及探头与小室内标准场之间的相互作用等,对于分析电磁场探头的校准过程具有参考意义。     

CO20-G型小电容标准的研制

为了适应小电容测量仪器定标的需要,填补我国小电容标准的空白,我们经过几年的努力,研制成功了CO20-G型(1～0.001pF)小电容标准。一、技术指标及结构小电容标准由四只电容器组成,电容器是以惰性气体为介质的标准空气电容器。其主要技术指标列于表1。对于我国目前的情况,士0.1％的精度一般就能满足需要,考虑到今后计量科学事业的发展,我们将指标作了适当提高。电容器均制作成同轴型电极。电极、电极支架等,全部采用殷钢材料,以减小电容器的温度系数。1pF电容器(图1a)的内电极5、外电极8均制成圆筒形,由1、2、7、9四个氧化铝高频瓷环固定在支架上,其容量由两端保护环3、6间的内电极长度确定。用微调螺钉4进行细调,可获得1×10~(-4)的调整精度。     

高准确度大电容标准的研制

本文介绍了用补偿式电流互感器和双级电压跟随器技术从根本上改善了传统大电容的性能，从而大大提高了大电容器容量的不确定度，且克服了传统大电容器频率特性差。电压系数大的缺点。     

NIM新一代二端对电容电桥装置

基于一种交流电桥自动辅助平衡方法,中国计量科学研究院(NIM)研制了新一代二端对电容电桥装置。电桥采用固定比率的感应耦合比率臂电桥,通过复用比率,用单一电桥即实现了计算电容过渡和电容10:1传递;采用一种改进的靴带法实现电桥感应比率臂比率的精确校验。该装置用于电容单位的量值复现和标准电容器的高准度量值传递。利用新一代二端对电容电桥装置,可从计算电容装置复现1 pF电容值,并实现电容 1~100 pF的十进制量值传递,电容量值传递相对标准不确定度可达5×10^-9(1592 Hz)。采用该电桥参加了10 pF和100 pF电容国际关键比对(CCEM.K4-2017),中国比对成绩优异,数据均非常接近关键比对参考值(KCRV),其中100 pF的结果最接近KCRV,与KCRV取得了很好的一致性,从而获得国际互认。     

Evaluation of a Capacitance Scaling System

An improved error analysis of an existing capacitance scaling system for supporting measurements of higher valued (10 nF to 100 ) ceramic-dielectric four-terminal-pair (4TP) capacitance standards over the 100-Hz to 100-kHz frequency range is described. The capacitance scaling system uses a commercial impedance (inductance-capacitance-resistance) meter and a single-decade inductive voltage divider as an impedance comparator. Four-terminal-pair capacitors in decade (10 : 1) steps from 10 nF to 100 F are measured. The system's 10 : 1 scaling error is determined using 100-pF and 1-nF air-dielectric 4TP capacitance standards with known capacitance and loss characteristics over frequency. This paper discusses the significant reductions in measurement uncertainty that were attained through the use of improved calibration standards and measurement method refinements. Details of the uncertainty analysis for a 10-nF capacitor (in the 100-Hz to 10-kHz frequency range) and verification data are presented.     

Evaluation of the frequency dependence of the resistance and capacitance standards in the BIPM quadrature bridge

The Bureau International des Poids et Mesures (BIPM) has established a measurement chain allowing calibration of capacitance standards in terms of the quantized Hall resistance (QHR). An important element in the chain is a quadrature bridge linking a pair of ac resistors of values 2R/sub K/ /spl ap/ 51.6 k/spl Omega/ to a pair of capacitance standards. The quadrature bridge can be operated at five different frequencies: 513, 1027, 1541, 3082, and 6164 Hz. For such measurements, we use different ratios (1/1, 4/1 and 1/4) for the main inductive voltage divider in the quadrature bridge and three different pairs of capacitors of values 3000, 2000, and 1000 pF. A calculable coaxial resistance of 1290.6 /spl Omega/ (R/sub K//20) is used as a reference to evaluate the frequency dependence of the 51.6-k/spl Omega/ resistances. This allows the calibration of capacitance standards at the five different frequencies. The measured frequency dependences of 10 and 100 pF capacitance standards are reported.     

Towards accurate measurement of the frequency dependence of capacitance and resistance standards up to 10 MHz

Progress toward an understanding of the frequency dependence of capacitance and resistance standards at frequencies up to 10 MHz is presented. A qualitative comparison is also made for capacitance and dissipation factor measurements between the National Physical Laboratory (NPL) high-frequency four terminal-pair (4TP) bridge and a commercial impedance analyzer for the first time. A set of novel high-frequency calculable coaxial resistance standards, of nominal 100 /spl Omega/ and 1 k/spl Omega/ values, have been developed and their calculated frequency dependence up to 1 MHz is given.     

New multifrequency method for the determination of the dissipation factor of capacitors and of the time constant of resistors

A new method for the simultaneous determination of the dissipation factor of capacitors and of the time constant of resistors by a multifrequency method is presented. This method is based on the measurement of impedance ratios at two or more frequencies. A bridge is set up with a programmable two-channel ac voltage source and the impedances to be compared. The impedance ratios are determined by synchronous sampling procedures and application of discrete Fourier transform. In a first experiment, a high-grade gas-filled 1 nF standard capacitor was compared with a stable 1 M/spl Omega/ ac resistor at frequencies between 31 Hz and 666 Hz. The estimated standard uncertainties (k=1) are 0.6/spl middot/10/sup -6/ for the dissipation factor of the capacitor and 0.4 ns for the time constant of the ac resistor.     

Characterization of Capacitance Standards at High Frequency at National Physical Laboratory,India

Four-terminal-pair air dielectric capacitance standards with nominal values of 1000 and 100 pF have been characterized up-to 10 MHz at NPLI. The procedure employed involves the determination of all capacitive and inductive parameters of the simple electrical-equivalent-circuit-model of these capacitance standards. The effective capacitance of each standard has also been computed as a function of frequency from 1 kHz to 10 MHz. The capacitive parameters have been measured at 1 kHz while inductive parameters have been estimated up to 10 MHz using linear regression analysis by employing least-squares-approximation method. The paper highlights the computation procedure of impedance terms which further requires the determination of various capacitive and inductive terms involved in the calculation of effective capacitance. The method employed for the estimation of inductive parameters as a function of frequency is also discussed in detail. The present work will help in the establishment of metrological traceability of capacitance standards at high-frequency at NPLI which will be further used to establish calibration facility for LCR meters and RF impedance analyzers for capacitance parameter up-to 10 MHz.     

Design methodology of Miller frequency compensation with current buffer/amplifier

Current buffers/amplifiers are used in series to the Miller compensation capacitor with the aim of eliminating the positive zero introduced by the forward path. They are increasingly adopted because of their low-voltage features, high-speed performance and, recently, for their suitability to be used with large capacitive loads (when a current gain is introduced). The authors propose a novel and simple design approach for the frequency compensation of a two-stage amplifier exploiting a current buffer/amplifier. The procedure has been profitably applied to a class-AB two-stage CMOS operational transconductance amplifier, having a 100 pF load. In particular, three compensation networks were designed using a 1.3 pF, 0.6 pF and 250 fF compensation capacitor alternatively. Moreover, the adopted compensation topology provides an improvement in terms of power supply rejection ratio, which was also analytically demonstrated. Simulations that are in very good agreement with theoretical results are also given.     

New Fused-Silica-Dielectric 10-and 100-pF Capacitors and a System for Their Measurement

New instruments have been designed to bring to standards laboratories the improved accuracy of capacitor calibrations developed by the National Bureau of Standards. The new 10-and 100-pF reference standard capacitors, based upon an NBS design, use a fused-silica dielectric with gold electrodes to provide the time and voltage stability required for calibrations to parts in 107. To maintain the capacitor temperature constant to within 0.01 °C, one model of the capacitors is designed for use in an oil bath, the other model is fitted with a new, stable, thermostatically controlled air bath. The system to measure these capacitors with a precision of parts in 108 consists of a bridge, detector, and oscillator. For these special measurements and for the general calibration of a wide range of capacitors, the new transformer-ratio-arm bridge has 12 capacitance decades and a range of 10 MAF-10-7 pF, and five conductance decades and a range of 103110-10 tmho. The new phasesensitive detector and power oscillator provide high sensitivity to bridge imbalance over the frequency range 10 Hz-100 kHz.     

Field of hypersonic displacements at the impedance dispersion frequencies in a multilayer ferroelectric film capacitor

Distribution of the amplitude of mechanical displacements generated by a microwave electric field at the frequencies of acoustic resonance in a plane-parallel Pt/(Ba,Sr)TiO₃/Pt/Si thin-film capacitor structure has been studied. The acoustic eigenmodes of the multilayer resonator are determined, the excitation of which leads to a frequency dispersion of the electric impedance of the ferroelectric film capacitor. The frequency dependences of the real and imaginary components of the microwave current in the capacitor are analyzed with allowance for the induced piezoelectric effect.     

Frequency dependence of the complex impedances and dielectric behaviour of some Mg-Zn ferrites

Complex impedances of some magnesium-zinc ferrites, MgxZn1-xFe2O4 (x=0.4, 0.5, 0.6 and 0.7), in the frequency range of 1 mHz-10 MHz were measured at 300 K. The complex-plane impedance spectrum from each sample indicates that the capacitive and the resistive properties of the materials are mainly attributed to the processes that associated with the bulk (grain) and the grain boundary. A low-frequency dispersion (LFD) and a negative capacitance regions are also observed at low frequencies. A small series resistance of about the same value for all samples is also observed. The bulk and the grain boundary components are analysed by assuming a two-layer leaky capacitor. The simulated complex impedances using the Cole-Cole expression are in agreement with the measured values. The dielectric properties of the materials are attributed to the interfacial polarization and LFD at low frequencies and the orientational polarization at high frequencies. These properties result in the dielectric loss which composed of a Debye-like loss peak at high frequency end and a strong LFD below 1 Hz. Both regions exhibit universality with regard to the power-law relation between the dielectric loss (ε″r or χ″) and frequency as given by ε″r∝ωn-1, where n=0.14 and n=0.02, respectively. The exponent is marginally negative, n=−0.03, in the region of negative capacitance below 3–4 mHz. The variations of the above properties and the characteristic parameters for different compositions of the Mg-Zn ferrites are discussed. This revised version was published online in November 2006 with corrections to the Cover Date.