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A new reference resistive-capacitive voltage divider is presented in this paper, operating in dc and ac from 10 to 200 kHz. The ratio error is lower than 0.1% and the phase error is lower than $400~\mu $ rad (1.375’) at 100 kHz. The divider is stable and repeatable. The scale factor (SF) and the phase error repeatability, tested in 24-h continuous measurements repeated during 15 weeks, show an SF variation lower than 80 ppm and a phase error variation lower than 20 $\mu $ rad. This allows one to define a calibration matrix of the device bringing its relative measurement uncertainty lower than $0.5 \cdot 10^{-3}$. The divider calibration has been obtained with a step-up method, which could improve traceability in many laboratories and is described in this paper. The divider can be embedded in a calibration chain to test the accuracy of voltage transducers in the measurement of the ac voltage ripple, in the presence of a significant dc component, as it occurs in many power electronic systems. The voltage calibration chain is based on the use of the reference divider and a voltage injector, the secondary of which is placed in series with a stable dc source. By means of this calibration system, one of the best commercial voltage transducers on the market has been analyzed. This paper also highlights how the proposed voltage calibration chain could be used in perspective in a phantom power system for the development of a dc plus ac power standard. [ABSTRACT FROM AUTHOR]

The design and development of a new nonintrusive-type true-rms ac voltage measurement probe are presented in this paper. The measurement circuit of the capacitively coupled nonintrusive voltage sensor is designed to provide an output that is directly proportional to the rms value of unknown ac voltage $\text{V}_{\mathrm {X}}$ , which contains the power frequency (50 or 60 Hz) component along with the typical harmonic frequency components due to nonlinear loads. This is accomplished by a specially designed autobalancing signal conditioning circuit. The existing noncontact probes are designed for a set frequency and will not provide accurate rms value of a signal that has multiple frequency components. The output is independent of the coupling capacitance between the probe electrode and the insulated wire/cable under measurement. Thus, the sensor has low sensitivity to the variation due to the probe-to-wire capacitance, good linearity (0.95%), and accuracy (0.88%) over a range of voltages (0–1000 V) tested. Various parameters that affect the performance of the probe are analyzed, quantified, and discussed in this paper. A prototype of the probe along with the proposed autobalancing circuit has been designed and developed. The prototype has been tested in detail to evaluate the accuracy, linearity, and repeatability. The results obtained established the practicality of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper presents the wideband system identification (WSI) technique, i.e., an online method to identify power impedances over a wide frequency range from which the corresponding parametric impedance can be calculated online as well. The WSI technique exploits an existing custom 25-kW power electronic converter on the top of its power conversion function, which serves as power amplifier of an existing power hardware-in-the-loop (PHiL) simulation setup. The PHiL simulation technique allows connecting a real device under test (DUT) with the real-time simulated rest of system (ROS) at power level. An interface algorithm (IA) on simulation side and a power amplifier (the 25-kW power electronic converter) connect ROS and DUT. This paper shows the impact of the uncertainties in the WSI chain on the accuracy of the impedance identification and highlights how the WSI technique can be combined with the damping impedance method IA to improve both accuracy and stability of the PHiL test bench. The application of the method is illustrated for the scenario of a PHiL test of a dc microgrid with a passive load. [ABSTRACT FROM PUBLISHER]

Power quality is described by voltage fluctuation measures. Voltage fluctuation is understood as “a series of voltage changes or a continuous variation of the rms or peak value of the voltage.” Voltage variation is most often manifested by flicker, which might become obnoxious at a high enough intensity. One of the standard measures of voltage fluctuation is \boldsymbol Pst indicator. One of its major flaws is its limited diagnostic capabilities. Voltage fluctuation indices are the measure, which provides much bigger range of diagnostic capabilities. However, it has not been acknowledged as a standard measure. The initial part of this paper includes the description of the accepted method of reproducing voltage variation. It also presents general characteristics of the \boldsymbol Pst indicator and voltage fluctuation indices. The next part of this paper describes the methods of converting voltage fluctuation indices into \boldsymbol Pst indicator and vice versa. The capability of estimating the \boldsymbol Pst indicator on the basis of the indices has been confirmed. Three examples of measurement results of both these measures in low-voltage (LV) power grids have been presented. These results have proved the connection between the estimated values (on the basis of voltage fluctuation indices) and the results of the \boldsymbol Pst indicator measurements. [ABSTRACT FROM AUTHOR]

At present, the method of obtaining the voltage of transmission lines by using the inverse problem of the electric field is generally faced with the difficulties of solving data equations. Aiming at the above problems, the method that solves transmission wire voltage through spatial electric field integration based on D-dot sensor is proposed. In this paper, with the ground as the reference potential and the vertical line of the transmission line to the ground as the integral path, D-dot electric field sensor is applied to measure the instant electric field values of several nodes on the integral path and the transmission wire voltage is directly solved combined with Gauss–Legendre numerical integration algorithm. The Gauss–Legendre algorithm is verified by the electric field distribution data on the integration path obtained by simulation. Furthermore, the improvement of the Gauss–Legendre algorithm is realized through optimizing the integral interval so that the location of integral nodes is more reasonable. Finally, the measurement system based on LabVIEW is designed and the experiment platform of the analog transmission line is constructed. Experiment results show that the measurement method of transmission wire voltage through the improved Gauss–Legendre algorithm based on D-dot sensor owns high accuracy with an error of less than 1%. [ABSTRACT FROM AUTHOR]

This paper presents the design and implementation details of a complete noncontact (NC) voltage acquisition system, which allows the measurement of power-line voltage waveforms without galvanic contact. The system is composed by a novel capacitive probe, an analog front end (AFE), and a microcontroller-based digital signal processing stage. A deep experimental characterization of the noncontact measurement system was performed. The tests reported a high linearity (maximum nonlinearity of ±0.2%), a low input-referred noise (11 mVrms), and a low-frequency response distortion. Measurements of ±330-V triangular waveform signals were performed with maximum instantaneous errors below ±1.5 V. The power-line voltage (220 Vrms at 50 Hz) was acquired without galvanic contact with an instantaneous error lower than ±3 V, whereas the mean error on rms voltage measurements was 0.32% and the maximum 0.7%. A two-day continuous measurement of power-line voltage was accomplished for testing system’s stability, resulting in negligible accuracy variations. [ABSTRACT FROM AUTHOR]

Potential drop (PD) measurements are well established for use in materials testing and are commonly used for crack growth and strain monitoring. Traditionally, the experimenter has a choice between employing direct current (dc) or alternating current (ac), both of which have strengths and limitations. The dc measurements are afflicted by competing spurious dc signals and, therefore, require large measurement currents (tens or hundreds of amperes) to improve the signal-to-noise ratio, which in turn leads to the significant resistive Joule heating. The ac measurements have superior noise performance due to the utilization of phase-sensitive detection and a lower spectral noise density but are subject to the skin effect and are, therefore, not well suited to high-accuracy scientific studies of ferromagnetic materials. In this paper, a quasi-dc monitoring system is presented which uses very low-frequency (0.3–30-Hz) current which combines the positive attributes of both dc and ac while mitigating the negatives. Bespoke equipment has been developed that is capable of low-noise measurements in the demanding quasi-dc regime. A creep crack growth test and fatigue test are used to compare noise performance and measurement power against alternative DCPD equipment. The combination of the quasi-dc methodology and the specially designed electronics yields exceptionally low-noise measurements using typically 100–400 mA; at 400 mA, the quasi-dc system achieves a 13-fold improvement in signal-to-noise ratio compared to a 25-A dc system. The reduction in measurement current from 25 A to 400 mA represents a ~3900-fold reduction in measurement power, effectively eliminating resistive heating and enabling much simpler experimental arrangements. [ABSTRACT FROM AUTHOR]

Rapid voltage changes (RVCs) are power quality (PQ) events characterized by small and fast transitions between two steady-state root-mean-square (rms) voltage levels. RVCs occur quite often at the distribution level and are expected to be even more frequent in the future due to the increasing penetration of dynamic loads and renewable-based generators in the smart grid. Unlike other PQ events, RVCs are less critical, but also more difficult to detect than dips/sags and swells, due to their smaller voltage variations. Nevertheless, they can be harmful to generators’ control systems and electronic equipment in general. Moreover, they strongly affect flicker. The IEC Standard 61000-4-3:2015 clearly describes an algorithm for RVC detection. However, this approach is poorly characterized in the scientific literature. In fact, it suffers from some drawbacks. In this paper, some of them (e.g., rate-dependent detection limits and detection delays) are analyzed in depth. In addition, an alternative approach based on the estimation of the rate of change of rms voltage is proposed. Multiple simulation results show that the approach considered is more sensitive to noise, but also faster, especially when not so fast RVCs occur. Moreover, it allows measuring the rate of change of rms voltage, which is currently disregarded in the IEC Standard. [ABSTRACT FROM AUTHOR]

To establish a single European railway area, the European Commission requires, by 2019, that energy billings shall be computed on the actual energy consumed. So, in the near future, all the trains shall be equipped with an energy measurement system, whose measurement accuracy should be assessed and periodically reverified, as required by EN 50463-2. As for every energy and power measuring system, the voltage and current transducers play a crucial role as their accuracy could determine the performance level of the entire measurement chain. To answer to this emerging need, this paper presents a calibration system allowing the accurate testing of dc voltage and current transducers, up to 6 kV and 300 A and up to 10 kHz. It is able to reproduce all the tests prescribed by EN 50463-2, but in order to characterize the transducers in actual operating conditions, a series of additional tests can also be performed using synthetic complex waveforms or even signals acquired on-board trains. The expanded uncertainty (level of confidence 95%) of the calibration system is 43 $\mu \text{V}$ /V and 24 $\mu \text{A}$ /A at dc and 520 $\mu \text{V}$ /V and 820 $\mu \text{A}$ /A at 10 kHz. Moreover, the calibration of two commercial voltage and current transducers, currently installed in the trains of an Italian operator, is presented. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel conductance parallel-wire array probe (CPAP) to measure the interface characteristics of segregated horizontal oil–water two-phase flows. A measurement system of CPAP is designed to make it work in a cyclic excitation mode and detect the interfacial heights at different locations of a pipe cross section. A finite-element analysis and a static calibration experiment are conducted to access the relationship between the interfacial height and the dimension conductance detected by the CPAP. Through carrying out a dynamic experiment of horizontal oil–water flows, the 3-D oil–water interfaces are reconstructed using the CPAP responses to study the interfacial evolution and its effect on the droplet detachment. Finally, the average fluctuations of the oil–water interfaces are extracted based on the reconstructed 3-D oil–water interface. [ABSTRACT FROM AUTHOR]

This paper describes a new phase difference measurement system based on the three-voltmeter method (3VM) by introducing differential ac/single-ended dc switching for a thermal voltage converter (TVC). The 3VM-based phase difference measurement system has been developed in consideration of the simulation results and the loading effects derived from the TVC. The expanded uncertainties of differential voltage and phase difference measurements have been estimated (e.g., $80~\mu \text{V}$ and 0.0073° at 10 V/1 V, 1 kHz, and 60°). The phase difference measurement uncertainties of two voltage conditions ($V_{1} > V_{2}$ and $V_{1} = V_{2}$) have been focused and theoretically formulated. The phase difference measurements by the system have been made in the voltage range of 1 to 10 V at 1 kHz and 60°. The measurement results agree well with those obtained by a phase standard. [ABSTRACT FROM AUTHOR]

In this paper, we present a programmable ultralow dc current source developed at TÜBİTAK UME. The output current range is from 1 fA to 100 pA with 100 aA resolution and is directly traceable to dc voltage, capacitance, and time units. The principle of the device is based on applying a linear ramp voltage on standard capacitors with values between 1 and 1000 pF. These standard capacitors are commercial standard capacitors which are kept in a temperature controlled insulated box. Linear ramp voltage is generated using a commercial data acquisition card. Current source device is fully automated with computer control and can be used to generate any currents with 100 aA resolution in its full range. The uncertainty is 2.5 mA/A at 1 fA current. [ABSTRACT FROM AUTHOR]

New thin-film range resistors have been developed at the National Metrology Institute of Japan, to re-establish ac–dc voltage transfer standards in the 100–1000-V range at frequencies of 1–100 kHz. In earlier studies, the voltage dependence of the ac–dc transfer difference was observed during step-up procedures above 300 V. One of the possible reasons for this voltage dependence is the temperature rise due to the Joule heating, which may cause changes in the resistance of the resistor, as well as the temperature dependence of the dielectric losses in the resistor coating. In this paper, to reduce the voltage dependence, new thin-film heaters were directly fabricated on an aluminum nitride substrate to prevent heat from accumulating in the range resistor. The voltage dependence was evaluated by measuring the differences in impedance among various range resistors. Negligible voltage dependence in the step-up procedures from 100 to 1000 V was achieved. [ABSTRACT FROM AUTHOR]

This paper describes the application of GUM supplement 1 and supplement 2 in the intercomparison procedure of a group of four dc voltage reference standards. The results obtained are presented and according to these, the choice of a restriction is suggested to improve the uncertainty and avoiding the strong correlation of the estimated values. [ABSTRACT FROM AUTHOR]

Taylor–Fourier (TF) filters represent a powerful tool to design phasor measurement unit (PMU) algorithms able to estimate synchrophasor, frequency, and rate of change of frequency (ROCOF). The resulting techniques are based on dynamic representations of the synchrophasor, and hence, they are particularly suitable to track the evolution of its parameters during time-varying conditions. Electrical quantities in power systems are typically three-phase and weakly unbalanced, but most PMU measurement techniques are developed by considering them as a set of three single-phase signals; on the contrary, this peculiarity can be favorably exploited to improve accuracy and reduce the computational cost. In this respect, this paper proposes to directly perform the TF expansion of the space vector (SV) samples obtained from three-phase measurements. A new paradigm allows to independently estimate positive and negative sequence synchrophasors along with system frequency and ROCOF, leveraging the three-phase characteristics. The performance of the proposed technique is assessed by using test signals inspired by the standard IEEE C37.118.1-2011, including noise as well as magnitude and phase unbalance. Achieved results highlight the flexibility of the enhanced SV-based approach, which is capable to combine excellent dynamic performance together with an accurate estimation of both positive and negative sequence components. [ABSTRACT FROM AUTHOR]

This paper describes the determination of value of frequency-independent component of ac–dc voltage transfer difference of two calculable thermal ac voltage standards developed and maintained at the Silesian University of Technology Gliwice, Poland. According to our research, the value of this parameter determined with ac–dc transfer measurements is $0.0~\mu \text{V}$ /V with combined standard uncertainty ($k = 1$) equal to $0.3~\mu \text{V}$ /V. The obtained results were validated with fast-reversed direct current method and will be used to supplement the uncertainty budgets of these standards. The presented method does not require expensive quantum ac voltage standards. [ABSTRACT FROM AUTHOR]

This paper aims at characterizing and improving the metrological performances of current and voltage instrument transformers (CTs and VTs) in harmonic measurements in the power system. A theoretical analysis is carried out to demonstrate that, due to the iron core nonlinearity, CT and VT output signal is distorted even when the input signal is a pure sine wave. Starting from this analysis, a new method for CT and VT characterization and compensation is proposed. In a first step, they are characterized in sinusoidal conditions and the harmonic phasors of the distorted output are measured; in the second step, these phasors are used to compensate the harmonic phasors measured in normal operating conditions, which are typically distorted. The proposed characterization and compensation techniques are called SINusoidal characterization for DIstortion COMPensation (SINDICOMP). Several experimental tests, using high-accuracy calibration setups, have been performed to verify the proposed methods. The experimental results showed that the SINDICOMP technique assures a significant improvement of CT and VT metrological performances in harmonic measurements. [ABSTRACT FROM AUTHOR]

A novel measurement approach for power-flow analysis in medium-voltage (MV) networks, based on load power measurements at low-voltage level in each secondary substation (SS) and only one voltage measurement at the MV level at primary substation busbars, was proposed by the authors in previous works. In this paper, the method is improved to cover the case of temporary unavailability of load power measurements in some SSs. In particular, a new load power estimation method based on artificial neural networks (ANNs) is proposed. The method uses historical data to train the ANNs and the real-time available measurements to obtain the load estimations. The load-flow algorithm is applied with the estimated load powers, and the MV network state variables are obtained. The proposed method is validated for the real MV distribution network of the island of Ustica. The loads of selected SSs are estimated for two full days of different seasons. In comparison with previous works, satisfactory results are obtained in terms of uncertainty in the calculated power flows, thus suggesting the applicability of the proposed method for real-time monitoring of MV distribution networks. [ABSTRACT FROM AUTHOR]

Accurate power system state estimation facilitates power system control, optimization, and security analysis. In this paper, a joint filter approach is proposed to estimate both the static states (voltage magnitude and phase angle of bus) and the dynamic states (rotor angle, rotor speed, and transient voltages of generator) utilizing the measurements of phasor measurement unit. First, due to the complexity and dynamics of power system, the power system model is usually not known accurately. The uncertainties include both model uncertainty and noise statistics uncertainty. Therefore, $H_\infty $ filter is applied to reliable estimation of the static states. As a link between the static state estimation and the dynamic state estimation, the estimated static states are fed to dynamic state estimation. Next, to deal with the nonlinearity of synchronous generator model, an extended Kalman particle filter is employed to accurately estimate the dynamic states. The numerical tests on IEEE 30-bus system show that the proposed method is into both the static state estimation and the dynamic state estimation. [ABSTRACT FROM AUTHOR]

In-circuit impedance extraction of a time-variant electrical system is essential for real-time condition monitoring purpose. This paper looks into the design consideration of real-time in-circuit monitoring for a time-variant system based on inductive coupling approach and discrete Fourier transform in a moving window. By using two clamped-on-type inductive probes, the proposed setup eliminates the need of voltage sensors to measure the terminal voltages of system-under-monitoring (SUM) and, hence, eliminates direct electrical contact with the SUM. Therefore, it facilitates ease of mounting and disassembly. Experimental results show that with careful design consideration, the proposed method has the ability to measure the in-circuit impedance of a time-variant system in real time, which facilitates useful inputs for early detection of abnormality of the monitored electrical system that is time variant in nature. [ABSTRACT FROM AUTHOR]

A new method is developed for synchrophasor-based estimation of three-phase transmission line (TL) impedance parameters, applicable for both fully transposed and untransposed TLs. The method is based on accurate time-synchronized measurements of the voltage and current phasors at both ends of a TL. The method estimates the line impedance values using a robust estimator with the property that the influence of outliers on the final results is minimized. A robust estimator is chosen as an alternative to well-known ordinary least-squares estimators which are highly sensitive to outliers. The performance of the method has been evaluated using a laboratory setup simulating real power system conditions. The necessary conditions for algorithm convergence as well as the requirements for measurement accuracy have been studied. In addition, this paper describes validation results of the proposed method in real high-voltage power system conditions by measuring voltage and current phasors with two phasor measurement units installed on both terminals of a 400-kV fully transposed overhead TL. [ABSTRACT FROM AUTHOR]

This paper introduces a new data-driven bottom-up monitoring approach for distribution systems. In this approach, local estimations of the subsections into which the system is split are performed independently, thus leading to a scalable architecture. The monitoring approach is focused only on the estimation of voltage magnitude rather than the complete state of the system. This reduces the measurement requirements significantly, thus addressing economical and technical concerns for existing systems, while staying open to accommodating further incremental improvements in the available data and data quality. The estimation of each section is realized via an artificial neural network (ANN), for which a set of parameterizations is available to cope with different operating conditions. The estimation convergence is achieved even with relatively few measurements, although accuracy varies depending on the available measurements. At the Medium Voltage (MV) level, where reconfiguration is common, a configuration identification unit chooses the right ANN, the one trained for the actual network configuration. The estimation process is computationally simple and can be executed on low-cost hardware, as demonstrated in this paper by the implementation on a BeagleBone Black board. To demonstrate the concept, a prototype and a laboratory setup have been developed. The experimental test results are presented both for an Low Voltage distribution system and an MV distribution system. [ABSTRACT FROM PUBLISHER]

A single-contact voltage sensor designed for accurate measurements of ac voltages across a pair of conductors is described. The sensor design is motivated by remote monitoring applications where accurate voltage measurement of high-voltage transmission lines is required. The body of the sensor is electrically and mechanically attached to a single conductor: either the neutral or high-voltage conductor. A capacitive sensing plate attached to the sensor creates a capacitive voltage divider by using the stray capacitance to the noncontacted line. A very high-impedance buffer is used to measure the voltage across the divider output and estimate the line voltage. An important part of this paper includes a method of calibrating the sensor such that blind voltage measurements can be made without knowing the exact geometry of the conductors. Other important aspects of the design include a two-stage voltage divider for retaining accuracy and increasing the voltage range of the sensor. The work is supported by extensive numerical simulation models which were used to determine the optimum design for the sensing plate and to evaluate the sensitivity to different configurations including conductor spacing and the height above ground. For calibration values which are accurate to 1%, the line voltage can be measured with an accuracy of 10%. The paper describes the theory, design, and experimental verification of the sensor up to a line voltage of 7.5 kVrms. [ABSTRACT FROM PUBLISHER]

This paper presents an improved calibration setup for static bridge standards with a carrier frequency supply voltage in the frequency range between 225 Hz and 5 kHz. In the past, the small bridge differential voltage in the mV/V range was calibrated in two subsequent voltage ratio calibrations. However, this procedure is time-consuming and only works reliably if both voltages are stable over time. For this purpose, a new setup was developed that is able to measure the differential voltage of the bridge standard in one single measurement. This reduces the calibration time by approximately two thirds, thereby also reducing the uncertainty. [ABSTRACT FROM AUTHOR]

This paper proposes an innovative method for power consumption measurement in microcontroller-based systems that provides high accuracy on a wide dynamic range of current values, which makes it particularly suitable for all those applications characterized by alternating low-/high-power modes and fast current variations. We demonstrate that using an op-amp-based voltage feedback configuration, it is possible to use shunt resistor values higher than usual to obtain increased voltage drops without affecting the microcontroller’s power supply voltage. Consequently, it is possible to directly use a data acquisition board to acquire the shunt voltage, eliminating all those common errors, like offset and gain, due to the use of an additional intermediate amplification stage. The proposed scheme has been successfully used to accurately characterize the power consumption of a single sensor node of a wireless sensor network. [ABSTRACT FROM AUTHOR]

Accurate and fast characterization of voltage variations helps to evaluate their severity on equipment and activate protections. In this paper, a methodology for tracking and characterization of voltage variations, sample to sample, is presented. It consists of a Hilbert transform to estimate the voltage of the signal’s envelope, a fuzzy logic system to track down the type of voltage variation, and a rule-based method for the final identification and decision making according to IEEE Std 1159-2009. Unlike some techniques presented in the literature for tracking voltage variations such as the Kalman filter and adaptive linear network techniques, the proposed methodology requires neither a harmonic model nor an algorithm to adjust the model parameters, which in many cases increases the computational burden and time tracking. It is worth mentioning that the proposed classification stage does not need a training stage; therefore, its development is easier and its efficiency does not depend on a data training set. The performance of the proposed methodology is validated and tested using synthetic signals as well as real measurements of voltage variations. In addition, an implementation of our methodology into an field-programmable gate array based system is performed in an effort to offer a low-cost and portable system-on-a-chip solution for online and real-time monitoring of voltage variations. [ABSTRACT FROM PUBLISHER]

This paper presents a digital automatic unbalanced bridge designed for comparing the impedances of $R-R$ , $R-C$ , and $C-C$ . The measurement principle uses initial balancing of the bridge using two digital sine wave sources, then measuring the ratio of voltage drops on the compared impedances as well as the finite bridge unbalance voltage. The present method is novel because it is not necessary to obtain a complete voltage nulling and also because it is readily implemented with a commercial data acquisition (DAQ) card. An NI USB6281 DAQ card was used to obtain the results; this card combines the two 16-bit digital-to-analog converters with one multiplexed 18-bit analog-to-digital converter. Such a measurement system, which is relatively simple and inexpensive, can compare impedances with an error below 10 ppm. Some considerations concerning the relationship between the measurement accuracy of unbalanced voltage and the level of the bridge unbalance are given. [ABSTRACT FROM PUBLISHER]

Nowadays, voltage transducers in medium-voltage (MV) distribution networks operate in nonsinusoidal conditions while their calibration is still based on simple sine-wave tests. A more significant characterization could be achieved using complex multitone signals. However, this requires an MV generator able to apply arbitrary voltage waveforms to the transducer under test. The authors have recently proposed a simple MV signal generator that can be effectively employed for this purpose. In this paper, the performance of this MV generator has been carefully analyzed. A characterization procedure based on multisine excitation has been proposed and tested. In particular, the main causes of uncertainty have been identified and their impact on the accuracy of the generated voltage evaluated. The analysis considers both linear and nonlinear effects, such as harmonic distortion and hysteresis. [ABSTRACT FROM PUBLISHER]

We have evaluated the linearity of commercial digital voltmeters (DVMs) using a programmable Josephson voltage standard (PJVS) system. The PJVS system is composed of a 524 288-niobium nitride-based Josephson junction array that has the ability to generate arbitrary output voltages up to 17 V with a resolution of 12 bits. In our system, the junction array is operated in a 10-K compact cooler without a liquid-helium coolant. Up to now, we have succeeded in generating accurate dc voltage levels of up to approximately 13 V using this system. In this paper, we demonstrate our PJVS system as a tool for investigating the linearity characteristics of commercial DVMs, with an accuracy level of 0.1 \mu \textV /V or better, and discuss the uncertainty sources in these measurements. [ABSTRACT FROM PUBLISHER]

This present paper describes the development of a capacitance measurement system in the picofarad region. The system uses an universal serial bus port-based arrangement in conjunction with an indigenously developed Programmable Intelligent Computer microcontroller-based frequency synthesizer-vector voltmeter that can be used to measure the voltage in vector form and the capacitance can be determined using circuit solution technique. An intelligent two-layered, hierarchical reinforcement-based instrumentation scheme is proposed that can be integrated along with the original measurements to significantly improve the system performance. In layer 1, an extreme learning machine-based supervised phase reinforcement scheme is employed to improve the accuracy of the voltage measurement. Subsequently, in layer 2, local polynomial-based reinforcements are employed to improve both the resistive and reactive part measurements in the unknown capacitance. Three variants of ELM-based reinforcements are implemented for capacitance measurements in the range 100–10 000 pF and the utility of the hybrid ELM-polynomial-based reinforcements for such measurements is aptly demonstrated. [ABSTRACT FROM PUBLISHER]

This paper describes the design and performance of a wideband high-voltage dc (HVDC) reference divider module. The module has a nominal voltage of 200 kV, and it has been designed so that a number of modules can be stacked to extend voltages up to 1000 kV. The module, or a stack of modules, will be used for traceable calibration of HVDC measuring systems in customers' laboratories. The first priority in the design was the accuracy of HVDC measurements. In addition, the divider was designed to have wide bandwidth, both to enable measurement of ripple voltages and to prevent damage during possible flashovers. [ABSTRACT FROM PUBLISHER]