直流高压标准装置国际近况

简单介绍电磁计量领域关键比对数据库中直流高压参数标准装置-直流高压分压器的原理,分析了电阻发热、电晕放电以及绝缘支架漏电对直流高压分压器的影响,归纳总结目前国际上先进计量机构的直流高压标准装置的结构型式以及在校准时引入的不确定度来源。给出了直流分压器达到10-6量级的必要条件。     

电机定子匝间绝缘测量用冲击分压器性能试验研究

在研究电机定子电气性能检验装置校准方法项目过程中,研制了一种采用高压无感电阻、等电位屏蔽措施、二级分压结构和分布电容调节技术的冲击分压器,它被用于电机定子匝间绝缘项目的冲击电压峰值和波前时间的测量。经过试验,该电阻分压器的分压比误差小于0.5%;上升时间小于100ns,满足测量指标要求。     

Digitally Controlled Absolute Voltage Division

In this paper, a principle for absolute voltage division is presented. The division ratio of a voltage divider on this principle does not depend on the values of its elements but depends exclusively on the configuration of the divider network. Hence, calibration is not necessary and not even possible. Absolute voltage division is obtained by cyclically shifting the network elements along all positions in the divider network. Each position is maintained for an equally long time interval. The average output voltage of such a dynamic divider is identical to that of a static divider with the same network configuration but composed of elements which all have the same value. To verify the principle in practice, a digitally controlled resistive voltage divider has been built. It has been realized with easily available electronic components, such as carbon resistors with ± 5-percent tolerance, junction field-effect transistors as electronic switches and digital integrated circuits for the generation of the switch drive signals. The inaccuracy of this divider is less than 5 ×10-6 and the temperature coefficient of the division ratio is less than 5 × 10-8/°C from 0°C to 40°C. It is expected that the performance, of this prototype can be improved.     

Progress Toward a 1 V Pulse-Driven AC Josephson Voltage Standard

We present a new record root mean square (rms) output voltage of 275 mV, which is a 25% improvement over the maximum that is achieved with previous ac Josephson voltage standard (ACJVS) circuits. We demonstrate the operating margins for these circuits and use them to measure the harmonic distortion of a commercial digitizer. Having exceeded the threshold of 125 mV rms for a single array of Josephson junctions, we propose and discuss the features of an eight-array circuit that is capable of achieving 1 V rms. We investigate the use of a resistive divider to extend the ACJVS voltage accuracy to higher voltages. By the use of a switched-input measurement technique, an integrating sampling digital voltmeter, a resistive voltage divider, and ACJVS synthesized sine waves as reference voltages, we characterize the stability of a commercial calibration source for a few voltages up to 2.7 V.      

10-kV High-Accuracy DC Voltage Divider

A high-accuracy voltage divider based on the Hamon/Rayleigh ratio principle has been made for the absolute measurement of the volt and also for building up the voltage scale to 10 kV. It is composed of 100 equal resistors of nominal value 100 k? and an adjustable 100-k? resistor with taps at 10 and 1 k?. By using appropriate connections, a total 10-M? divider with 1-k? output is constituted in which various voltage ratios up to 104 can be obtained. A guard circuit is provided to minimize the leakage currents. The calibration of the divider is simplified by using parallel or series-parallel connection of resistance elements so that all comparisons are made at a ratio of 1:1. For 10 kV only, two comparisons are required. The measurement of performance of the divider and the analysis of errors have been made. The most important factor affecting the voltage ratio is self heating, for which a correction is necessary. The total error would be less than 0.58 ppm.     

钨酸钠对取向硅钢绝缘涂层性能的影响

采用扫描电镜、爱波斯坦方圈、绝缘电阻测试仪、红外光谱仪和热分析仪等手段研究取向硅钢绝缘涂液中钨酸钠对制备的磷酸盐绝缘涂层微结构和性能的影响。结果表明:随着钨酸钠含量的逐渐增加,涂液与取向硅钢基底的润湿角先减小后增大;取向硅钢的层间电阻、叠装系数和磁感应强度均先增大后减小,铁损先减小后增大。当钨酸钠含量为2.0%(质量分数)时,涂液与硅钢基底的润湿性能最好,润湿角为39.3°;涂层致密、平整,绝缘涂层与硅酸镁底层之间存在0.8μm左右的过渡层,而且涂层的耐吸湿性能并不产生显著变化;取向硅钢的层间电阻、叠装系数、磁感应强度和铁损均达到最佳值,分别为14073Ω·mm~2,97.0%,1.893T和1.051W·kg~(-1)。     

Potential dividers with a constant output resistance

Conclusions Above wye and chain-connected potential dividers can be used in all cases when normal dividers with discrete scales are used, if the condition of their use does not require a strictly constant input resistance. Such dividers can be successfully used in various automatic compensation measuring instruments with digital recording [5] and in devices which convert discrete coded information into voltages [4]. In these instruments the simple switching consisting of separate two-position elements is effectively used.The possibility of reducing to a minimum the number of precision resistances in the composition of the divider and less strict requirement for the quality of contacts is of undoubted interest for metrology. Although in normal circuits for measuring emf these dividers cannot be used owing to their variable input resistance, they can still be used for comparative precision measurements.These dividers will find wide and diverse application in cases when a constant output resistance is required, and the use of normal dividers involves inevitable errors; for instance, in two-stage potentiometer circuits, electronic models, grid electrical integrators, and various electrical checking devices.     

Protection of the null indicator from leakage currents in voltage comparison circuits

Conclusions The circuit methods proposed for protecting the NI from leakage currents reduce the requirements on the insulation resistance by a substantial amount. As a rough guide it is recommended that in comparison circuits for emf's and voltages which contain only the sources being compared, the NI should have current protection because it is simpler to realize and to use, while in the circuits which include more auxiliary voltage sources it should have potential protection (Fig. 2a). A final choice of protection circuits is only possible after analyzing their effectiveness by the procedure proposed in this article.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 40–43, June, 1975.     

交流注入式电池内阻测试仪电阻参数的校准方法

分析了基于交流注入式电池内阻测试仪电阻参数的测量原理,研究了采用标准交流电阻和感应分压器对其进行校准的方法,利用多位双级感应分压器对标准交流电阻的电压进行分压,模拟产生多值高准确度交流电阻箱,解决了电池内阻测试仪校准缺乏高准确度标准器的问题,分析了标准交流电阻的时间常数和感应分压器的相位误差对测量结果的影响。将该方法校准结果与采用实物标准电阻的校准结果进行了比较,在全量程范围内相差小于0.02%,表明该方法具有较高准确度。     

Coaxial Capacitive Dividers for High-Voltage Pulse Measurements in Intense Electron Beam Accelerator With Water Pulse-Forming Line

In this paper, a new coaxial capacitive divider is investigated. The electrical characteristics of the capacitive divider are theoretically analyzed, and the parameters of the capacitive divider are calculated and measured. Its rise time is about 8 ns, and the divider ratio is over 2000. The divider is employed to measure the pulsed high voltages of an intense electron beam accelerator with a water pulse-forming line (PFL) in our laboratory. The capacitive divider can directly measure the diode voltage within nanoseconds, and when combined with an integrator, it can measure the PFL charging voltage with a duration of several microseconds. Compared with conventional resistance dividers, the capacitive divider has more advantages, such as compactness, stability, a relatively high divider ratio, a fast response time, and not much of an effect on the accelerator.      

Adjustment of division factors of step voltage dividers

Conclusions The suggested method of adjusting step voltage dividers consists in successively equalizing the divider resistors switched in a definite order and introduces no systematic error. Conditions have been formalized for the applicability of the method. Relations between the voltage transfer ratios of the divider after adjustment and the accuracy of resistance equalization have been derived.Translated from Izmeritel'naya Tekhnika, No. 9, pp. 49–53, September, 1977.     

On the Output Resistance of Self-Checking Voltage Dividers

This paper deals with the computation of the variable output resistance of Cutkosky's self-checking binary voltage divider. For an N-bit divider, the maximum output resistance was found to increase with N at the rate of N/9 times the divider's characteristic input resistance. To increase the divider's resolution while limiting its output resistance, a binary potentiometer as a termination is suggested.     

直流高电压电阻分压器的设计与实现

对直流高压电阻分压器的设计进行了较为详细的论述.通过对所用电阻的合理选择和组合,并采取了正确的分压比测量方案和等电位屏蔽措施,保证了分压比的准确和稳定.     

A Universal Potentiometer for the Range from One Nanovolt to Ten Volts

Recent interest in accurate dc measurements down to nanovolt levels has prompted the development of a wide voltage range potentiometer of a new type with 7 dial resolution and extremely high accuracy. The potentiometer design is almost perfectly "neutral." All switch contacts and resistors of the main potentiometer operate at high voltage levels, and contribute thermal EMFs which are attenuated by a factor of ten thousand times (to less than 0.1 nanovolt levels) on the nanovolt range. The device serves as an "autocertified" voltage potentiometer standard. It is certified traceable to National Bureau of Standards units using previously published " ratiometric" techniques and is capable of direct reading accuracy without correction from 2 ppm on the 10-volt range to 10 ppm of setting ±1 nanovolt on the 0.001-volt range. The Thevenin equivalent source resistance of the instrument is approximately 2.5 ohms on the 0.001-volt range, reducing Johnson noise levels to less than 1 nanovolt with practical null detector smoothing times. The instrument is designed so that it can be used both as a potentiometer and as a 7-dial Kelvin-Varley divider. The control portion of the instrument is separately packaged and can convert dividers now in use to this new type of universal potentiometer standard. This paper includes a complete theoretical study of the design characteristics of this state of the art potentiometer, and an analysis of all sources of error in the completed instrument.     

Measurement of AC and DC Insulation Leakage in Platinum Resistance Thermometers up to 960?��C

It is well known that insulation leakage at high temperatures can be one of the major contributions to uncertainties in measured temperatures above 600 °C. On the one hand, this insulation leakage shunts the sensor resistor leading to systematic errors in the measured temperatures, which are, in principle, characteristics of each thermometer. On the other hand, at high temperatures, degradation of the insulation materials used in the furnaces enhances the decrease of the insulation impedance between the thermometer and the furnace which also causes a systematic temperature measurement error. Two high-temperature standard platinum resistance thermometers have been used to measure these effects in different heat-pipe and three-zone furnaces. One of them was open-circuited by cutting the sensing element end allowing the measurement of the resistance between the two pairs of current?Cpotential leads. Two different setups were used to measure the AC and DC insulation resistances lead-to-lead and thermometer-to-furnace. The first one was a teraohmeter with a high value standard resistor in parallel with the leakage resistance to be measured and the other one an LCR meter to perform the AC measurements at different frequencies. In this article, results for both methods are presented.     

Humidity Threshold Model of Numerical Control Multilayer Printed Circuit Board for Electrochemical Migration

In this paper, numerical control finished boards are employed as test samples to evaluate the effects of the environment and bias voltage on the surface insulation resistance of printed circuit boards. The results indicate that the surface insulation resistance degradation processes leading to failure exhibit a relative humidity threshold value, which is mostly related to temperature, test patterns, and bias voltage. Then, a humidity threshold model is built on the basis of electrochemical migration to quantify the relationship between the relative humidity threshold and conductor spacing and bias voltage under the controlled environments. Finally, experiments and tests have been carried out to validate the effectiveness and practicability of the model. Furthermore, the residual analysis is applied to check the fitting effect of the proposed model. According to the new model, the humidity threshold value can be obtained to provide the guidance for reliability problems in application. It is crucial to the design and deployment of reliable printed circuit boards. Copyright © 2014 John Wiley & Sons, Ltd.     

Calculation of the errors of an inductive voltage divider with a balancing winding

A procedure for calculating the errors of the transfer factor due to the fact that the parameters of the sections of an inductive voltage divider with a balancing winding are not identical is proposed. The results of experimental investigations are presented.Translated from Izmeritelnaya Tekhnika, No. 10, pp. 40–43, October, 2004.     

Modeling and analysis of the electrical resistance measurement of carbon fiber polymer–matrix composites

The self-sensing damage detection method based on the electrical resistance measurement of carbon fiber polymer–matrix composites has been investigated for a decade. In order to eliminate the effect of contact resistance when using the two-probe method, the four-probe methods, which include the resistance, potential and voltage change methods, were proposed in literature. However, the basic problems involved in the four-probe methods remain unclear, i.e., the validity range and the applicability of the four-probe methods. In this paper, beam-type specimens with and without delamination damage are used to carry out numerical analyses for the above-mentioned problems. It is found that the four-probe resistance method is valid only when the through-thickness conductivity is comparable to or larger than the longitudinal conductivity. For the potential method, which measures directly the voltage values between the voltage contacts, the present results show that the percentage change in damage-induced voltage between a pair of voltage contacts is not consistent with the percentage change in resistance. The underlying reason is that the damage-induced voltage change depends on the location of the applied current, while the resistance change does not.     

Optimization of the internal admittance load of an inductivevoltage divider for low ratio error

The distributed capacitances between the strands of an inductive voltage divider degrade the voltage ratio. A calculation scheme to convert the distributed capacitances into equivalent concentrated capacitances at the taps is given. An optimized connection scheme for the strands is calculated to produce concentrated capacitances which are as equal and as small as possible. Capacitors are added at the taps for optimum equalization. The relative error of the output voltage for a 120-V:10-V divider has been reduced to less than 1×10^-7 in phase and less than 1 μrad in quadrature, at a frequency of 50 Hz     

Mitigation of ground loop effects in high-voltage measurements

Ground loops can affect voltage measurement systems, in particular those in high-power test circuits. The net or common-mode current through the signal cable shield induces interference in the signal circuit. A generalized transfer impedance Z_t describes this undesired coupling. In a low-frequency circuit model, Z_t decomposes into two terms which vary with the cable length l and with l ² respectively. Several divider setups are discussed; all employ the same high-voltage arm. The position and composition of the low-voltage arm vary. A proper design of the signal circuit ensures a low Z_t at the power frequency. Measurements confirm the model. With the low Z_t, the direct capacitive coupling between the high-voltage arm and neighboring circuits showed up as a comparable interference source