A proposal for a toroidal cross-capacitor

A proposal which describes the feasibility of both a secondary and an absolute transportable standard of capacitance having fixed intrinsic values rather then corresponding to a change of capacitance is illustrated. This has been achieved by the toroidal cross-capacitor (TCC) form which is exempt from “end” effects: The proposal evaluates the best form of the ring electrodes and the features of their design to fulfil this purpose with a relative uncertainty of a few parts in 10^-8 for a capacitance value in the range from 0.6 pF to 1.65 pF     

采用电补偿方案的新一代立式计算电容装置

针对立式计算电容最大不确定度来源的端部效应误差,中国计量科学研究院经过多年改进,研制出的最优中空电补偿电极在计算电容模型装置上,没有采用加装钉子头进行补偿的电补偿方案,并完成了诸如端部效应误差的补偿效果、偏心效应误差等电气性能验证试验,成功应用在新一代立式计算电容装置上。实验结果表明,采用电补偿方案的新一代立式计算电容装置复现1 pF电容单位的相对标准不确定度为1.0×10^-8。     

Improved capacitance measurements with respect to a 1-pF cross-capacitor from 200 to 2000 Hz

This paper describes frequency dependence measurements of fused-silica capacitance standards from 200 to 2000 Hz, using a 1-pF cross-capacitor as the reference. The measured frequency dependence of fused-silica capacitors was found to vary significantly, ranging from a change of less than 0.2 /spl mu/F/F for one standard to a change of 0.8 /spl mu/F/F for another over the frequency range. Increasing capacitances with decreasing frequency from 1592 Hz for all tested fused-silica capacitors indicates that dielectric relaxation due to dielectric bulk and/or interfacial defects is the dominant source of frequency dependence. The relative combined standard uncertainty at 200 Hz (the largest in the frequency range) is 0.07 /spl mu/F/F, which is smaller by about a factor of three than the uncertainty reported previously from the National Institute of Standards and Technology (NIST).     

Compact inductance standard

A portable Maxwell-Wien bridge as a part of the Korea Research Institute of Standards and Science (KRISS) inductance standard has been developed. Two auxiliary resistive-capacitive networks (analogous to a "Wagner ground") provide excellent stability of the bridge balance and impose less strict requirements on the components of the networks. Removable capacitance and ac/dc resistance standards used in the bridge arms make it possible to realize the inductance unit in terms of capacitance and resistance in the frequency range 500 Hz to 3 kHz. Investigations of the standard and results of preliminary (trial) comparison with the Mendeleyev Institute for Metrology demonstrate that the bridge can be used for measurement of 10 and 100 mH inductance standards with an uncertainty within (1-3) /spl mu/H/H at frequencies of 1 and 1.6 kHz. The use of this bridge as a constituent part of a transportable standard gives an opportunity to eliminate any uncertainty arising from instability of the standard inductors.     

微小电容测量仪500fF/1MHz溯源方法研究

fF量级高频微小电容测量在军工电子产品领域有着重要作用,针对微小电容测量仪500fF/1MHz点无法溯源的现状,研制了惰性气体封装的500fF高频标准电容器作为传递标准。建立高频小电容测量模型,基于“反算法”估算出500fF高频标准电容器分布参数,称作“理论推导”溯源方案,不确定度优于0.15%;利用3台同等量级的高频微小电容测量传递标准,称作“计量比对”溯源方案,不确定度优于0.07%。利用以上2种方案对同1台仪器开展溯源,实验数据结果基本一致,能够满足用户使用要求,为更低容值、更高频率的微小电容的溯源提供了可参考的路径。     

The MME-1 multivalued measure of capacitance

A small multivalued measure of capacitance in the 1 pF–10 F range has been developed for use at frequencies in the 50Hz–1 MHz band as a first-class standard. The construction and electric circuit are considered, and the frequency dependences of the capacitance of individual stages are given.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 55–56, November, 1994.     

A switched-capacitor interface for capacitive sensors with widedynamic range

A novel switched-capacitor interface for capacitive sensors has been developed based on a dual-slope analog-to-digital (A/D) conversion technique. The interface consists of a switched-capacitor integrator, a comparator, and digital circuits. The integrator first samples the sensor capacitance in the form of its proportional charge. A quantized reference charge is then extracted until the output voltage of the integrator becomes zero. An autoranging function is incorporated to achieve a wide dynamic range of sensor capacitance by changing the sampling count in a 2's geometric manner. A prototype interface built using discrete components has demonstrated a capacitance measurement over four decades with an accuracy better than 1%     

Measurement and testing specifications of voltage flicker in 220 V/60 Hz power systems

The International Electrotechnical Commission (IEC) flicker standard 61000-4-15, which was originally proposed for 230 V/50 Hz systems in Europe and further revised with an amendment to include the necessary modifications for 120 V/60 Hz systems in North America, is becoming more internationally adopted for evaluating the flicker severity. Since the IEC flicker standard is restricted to work on systems with 230 V/50 Hz or 120 V/60 Hz, however, the IEC standard cannot be directly applied to the other power systems beyond its coverage (e.g. 220 V/60 Hz systems in South Korea). A new weighting filter derived from lamp tests, new reference points and a new performance test specification to accommodate 220 V/60 Hz systems in South Korea, complying with the IEC standard, are proposed. The proposed weighting filter, reference points and performance test specification provide a practical guide to develop flicker meters for 220 V/60 Hz systems in South Korea.     

Frequency Dependence of a Cryogenic Capacitor Measured Using Single Electron Tunneling Devices

A new type of capacitance standard based on counting electronshas been built. The operation of the standard has alreadygiven very promising results for the determination of thevalue of a cryogenic vacuum-gap capacitor. The new capacitancestandard operates at an effective frequency close to dc,whereas capacitance metrology usually implies the use ofbridges operating at a fixed frequency around 1 kHz.Therefore, the frequency dependence of the cryogenic capacitoris critical to the practical application of this standard. Wepresent measurements of this frequency dependence using atechnique that involves the same single electron tunnelingdevices used in the capacitance standard.     

Nitrogen-oxygen co-doped corrugation-like porous carbon for high performance supercapacitor

Nitrogen-oxygen co-doped corrugation-like porous carbon (NO-PC) has been developed by direct pyrolysis of formaldehyde-melamine polymer containing manganese nitrate. The melamine, formaldehyde and manganese nitrate act as nitrogen, oxygen source and pore-foaming agent, respectively. NO-PC exhibits favorable porous architecture for efficient ion transfer and moderate heteroatom doping for additional pseudocapacitance, which synergistically enhances the electrochemical performance of the NO-PC-based supercapacitor. The electrode delivers specific capacitance of 240 F/g at 0.3 A/g when tested in 6 mol/L KOH electrolyte, good rate capability (capacitance retention of 83.3% at 5 A/g) as well as stable cycling performance (capacitance remains ~96% after 10000 cycles at 3 A/g). The facile synthesis with unique architecture and chemistry modification offers a promising candidate for electrode material of energy storage devices.     

电容传感器新型电容测量电路设计

提出了一种基于V／T变换的用于电容传感器的电容测量电路。它将被测微小电容变化量转换成时间信号并由单片机进行处理，电路结构简单，电路中没有影响测量稳定性和产生零点漂移的元器件，大幅度地降低了测量过程中的噪声。     

Metrological assurance of measuring instruments for capacitive parameters of varicaps

A set of standard measuring instruments (SMIs) has been developed for metrological assurance of newly produced fast meters for the capacitance and loss tangents tan of varicaps at 1 MHz. The SMIs incorporate a multivalued measuring standard for the range 1–1000 pF, a set of composite standards of tan in the range 2.10^–5–0.05 for the same capacitance, and a digital comparator. The errors of measurement are 0.01% for capacitance and 0.002 tan + (2–3)·10⁵ for tan. The SMIs are used to verify control specimens of varicaps used for periodic checking of fast capacitance and loss tangent meters.Translated from Izmeritel'naya Tekhnika, No. 12, pp. 43–44, December, 1994.     

Measurement Automation to Implement Evaluation Procedure of Four-Terminal-Pair Capacitance Standards Using S-Parameters

The evaluation procedure of four-terminal-pair capacitance standards using S-parameters is very complex as it involves the measurement of different parameters by multiple instruments. It also involves complex computation of effective capacitance as a function of frequency and its associated uncertainty in measurement. The reported paper presents the development of measurement automation program to implement evaluation procedure of four-terminal-pair capacitance standards of values varying between 1 and 1000 pF up to 30 MHz. The measurement automation increases the functionality with a comprehensive and flexible tool set for data acquisition, analysis, reporting and representation of results. The sequence of operations performed by the developed measurement automation program is described in detail. The program configures and measures S-parameters, converts S-parameters into corresponding impedance and admittance parameters, determines series and parallel resonance frequencies. Thereafter, it determines residual capacitive and residual inductive parameters and finally computes the effective value of each capacitance standard as a function of frequency along with the associated uncertainty in measurement. Measurement automation has provided precise and efficient way for the implementation of evaluation procedure of capacitance standards.     

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.     

Precision Capacitor Ratio Measurement Technique for Integrated Circuit Capacitor Arrays

The recent development of integrated circuit capacitor arrays and the growth of their applications have resulted in a need to perform precision testing as an aid to future design improvements. For reasons discussed in this paper, laboratory instruments such as capacitance bridges are not well-suited to this need. In order to test capacitor arrays accurately, a novel technique has been developed. It is based on a special algorithm in which the capacitor array is used as a precision voltage divider. A capacitor array tester consisting of both hardware and software has been built which executes this algorithm. This system has been used to perform measurements upon a large number (thousands) of NMOS and CMOS capacitor arrays. The standard deviation of this tester's measurement error is approximately 0.0009 percent of full scale (0.0088 LSB referenced to 10 bits). In contrast with manual testing with a capacitance bridge (requiring 10 min per array), the tester requires less than 5 s to fully test an array, mark the circuit and move to the next die position.     

A switched-capacitor interface for capacitive pressure sensors

A switched-capacitor interface for a capacitive pressure sensor is developed which provides a linear digital output. It consists basically of a sample/hold circuit followed by a charge-balancing analog-to-digital converter. The sensor capacitance changes hyperbolically with an applied pressure. To convert the nonlinear capacitance change into the linear digital output, two linearization methods are investigated. In either method, a linear digital output with an accuracy higher than 8-b is obtained. Because of its high-accuracy capability and compatible fabrication process, the interface described is best suited for a smart silicon capacitive pressure sensor     

A relaxation-oscillator-based interface for high-accuracyratiometric signal processing of differential-capacitance transducers

For high-accuracy signal processing of differential-capacitance transducers, an interface circuitry is developed based on a relaxation oscillator. Two capacitors of the transducer are multiplexed by diode switches to form the op-amp-based integrator. The duty ratio of the oscillator output then measures the ratio of two capacitances. A circuit analysis shows that the interface can detect the capacitance change as small as 0.01% of the total capacitance. Experimental results are also given to confirm the analysis     

Y5U multilayer ceramic capacitors with high-specific capacitance and low-equivalent series resistance

A dielectric powder material, for Y5U multilayer ceramic capacitors was developed in the Pb(Mg(1/3)Nb(2/3))O (3)-Pb(Ni(1/3)Nb(2/3))O(3)-PbTiO (3) ternary system by using an alkoxide process. Multilayer ceramic chip capacitors (10 muF) with high specific capacitances were fabricated using this powder. A Ag80%-Pd20% alloy was used for the internal electrodes. The alkoxide-derived capacitor had an extremely high specific capacitance of about 500 muF/cm(3) and a small temperature dependence meeting Y5U specifications of the EIA standard. The equivalent series resistance was approximately 20 mOmega at 500 kHz. The breakdown voltages of the capacitor were 300 V or higher. In accelerated load life tests and load humidity tests, no degradation of insulation resistance was found during 1000 h of testing.     

A microprocessor-based switched-battery capacitance meter

A microprocessor-based, switched-battery capacitance meter has been developed. It consists of an analog part, based on a previously designed capacitance meter, and a digital part in which a microprocessor and a timer perform the main functions. The capacitance is measured indirectly by means of a time constant measurement. Two phases of the measurement process are involved in measuring the capacitance. The first phase, when a capacitor is charged, is based on the software counter-timer measurements. The second phase, when the capacitor is discharged, requires a hardware timer controlled by the microprocessor. The digital hardware reflects a different approach than used for the previous construction     

NiCo2S4/CNTs复合材料的制备及电化学性能

采用一步水热法合成NiCo2S4和NiCo2S4/CNTs复合材料,通过进行XPS、XRD以及SEM对NiCo2S4、NiCo2S4/CNTs复合材料进行物理表征,采用三电极测试体系在电化学工作站上进行电化学测试。测试结果表明：通过掺杂CNTs改变了NiCo2S4的形貌结构,NiCo2S4在1 A/g电流密度下,比电容可以达到830 F/g,在10 A/g的大电流密度下,比电容保持率仅为78.3%;而NiCo2S4/CNTs复合材料在10 A/g下的比电容保持率可达到78.6%,并且在3 A/g电流密度下循环1000次,比电容保持率高达98.2%。