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In this article, a long-range length comparator, applicable for both static- and dynamic-index calibrations of a linear displacement sensor, is presented. The comparator consists of an air-floating linear motion generator (LMG) and an interferometric optical length calibrator (OLC). A novel design of the LMG made by multisegment splicing is introduced, in which a two-level vibration isolation arrangement, a multiple sliders’ setup, and an exoskeleton framework are adopted. The resulting linear motion can be extremely ideal even with a large stroke. The angular error is within $11.89~\mu $ rad covering the 12-m range. The maximum operating speed and the acceleration of the LMG are 10 m/s and 20 m/s2, respectively. A dual-path optical design of the OLC is displayed, resulting in high environmental tolerance and a small trigger delay of 4.75 ns. The best accuracy of the comparator can be ±($0.041+ 0.106L) \mu \text{m}$ with a resolution of 0.3 nm. The maximum error and operation speed of a 2-m range exposed encoder were successfully calibrated, and the grating pitch deviation was also found, by which the effectiveness of the comparator is proven. The proposed length comparator introduces a possible solution, for how a long-range linear displacement sensor, can be calibrated with high accuracy, efficiency, and applicability. [ABSTRACT FROM AUTHOR]

A new resistance bridge has been built at the Laboratoire national de métrologie et d’essais (LNE) to improve the ohm realization in the Système International (SI) of units from the quantum Hall effect. We describe the instrument, the performance of which relies on two synchronized and noise-filtered current sources, an accurate and stable current divider, and a cryogenic current comparator (CCC) having a low noise of $\mathrm {80~pA.t/Hz^{1/2}}$. The uncertainty budget for the measurement of the 100- $\Omega /(R_{\textrm {K}}/2)$ resistance ratio, where $R_{\textrm {K}}$ is the von Klitzing constant, amounts to a few parts in $10^{10}$ only. [ABSTRACT FROM AUTHOR]

The dual-coupled-linear congruential generator (LCG) (dual-CLCG) is a secure pseudorandom bit gene-rator (PRBG) method among various linear feedback shift register (LFSR), LCG, and chaotic-based PRBG methods for generating a pseudorandom bit sequence. The hardware implementation of this method has a bottleneck due to the involvement of inequality equations. Initially, a direct architectural mapping of the dual-CLCG method is performed. Since two inequality equations are involved for coupling, it generates pseudorandom bit at unequal interval of time that leads to large variation in output latency. In addition, it consumes a large area and fails to achieve the maximal period. Hence, to overcome the aforesaid drawbacks, a new efficient PRBG method, i.e., “coupled-variable input LCG (CVLCG),” and its architecture are proposed. The novelty of the proposed method is the coupling of two newly formed variable input LCGs that generates pseudorandom bit at every uniform clock rate, attains maximum length sequence, and reduces one comparator area as compared to the dual-CLCG architecture. The proposed architecture is implemented using Verilog-HDL and prototyped on the commercially available field-programmable gate array (FPGA) device. Furthermore, the sequences are captured through the logic analyzer and evaluated for randomness using the National Institute of Standard and Technology (NIST) standard test tool. The experimental result reports that the proposed PRBG method passes all the randomness tests with a high degree of consistency. [ABSTRACT FROM AUTHOR]

In this paper, a resolution enhancement method for direct interfacing of inductive sensors, without employing analog-to-digital converter and/or external driver circuit, is presented. In order to achieve better resolution with minimum relative error and current consumption factors, different schemes are implemented which vary in terms of: 1) step-input voltage provision methodology, i.e., through microcontroller ($\mu \text{C}$) pin or through external supply; 2) number of switches used; and 3) method of voltage detection, i.e., either using capture module or employing built-in comparator only. The maximum achievable resolution limits are explored by reducing the lower reference voltage ($\text{V}_{\mathrm {Ref L}}$) in case of detection through built-in analog comparator and/or reducing the series resistance. The one-point calibration technique is used to determine the accuracy. The experiments are performed at 16-MHz clock frequency in the inductance range of: 1) 10–100 $\mu \text{H}$ and 2) 100–1000 $\mu \text{H}$. The results show that in the limits of a maximum current sourcing/sinking capacity of a typical $\mu \text{C}$ , i.e., 40 mA, the proposed methodology enhances the resolution to $4~\mu \text{H}$ with a relative error of 1.2 in the percentage of full-scale span (%FSS). The maximum nonlinearity error in %FSS for inductance range 10–100 $\mu \text{H}$ and 100–1000 $\mu \text{H}$ is 1.1% and <0.4%, respectively. [ABSTRACT FROM AUTHOR]

An ultrastable low-noise current amplifier (ULCA) has been transferred between two laboratories, National Physical Laboratory (NPL) and Physikalisch-Technische Bundesanstalt, four times, with three of the transfers yielding a relative change in the transresistance gain of less than $2 \times 10^{-7}$. This is a new benchmark for interlaboratory transfer of small current. We describe in detail the use of a cryogenic current comparator to calibrate the ULCA at NPL, and the use of the ULCA to measure 1- $\text{G}\Omega $ resistors with relative uncertainties at the $10^{-7}$ level. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive investigation of several important error sources for the successive-approximation register (SAR) analog-to-digital converters (ADCs). The error sources that we discuss in this paper include the dynamic comparator offset, the dynamic gain error of digital-to-analog converter (DAC), the capacitor mismatch of capacitive DAC, the incomplete settling of DAC, the undershoot of reference voltage, and the input signal coupling. The integral/differential nonlinearities (INL/DNL) of SAR ADCs that are resulted from these error sources are analyzed and addressed. A diagnostic procedure is presented to identify the possible error sources based on the INL/DNL plots. In addition, design suggestions for overcoming these problems are also offered and recommended in this paper. [ABSTRACT FROM AUTHOR]

The four-terminal-pair (4TP) definition of impedance standards allows reaching ultimate accuracy in impedance metrology. In general, the 4TP definition requires dedicated circuitry to be included in the bridge network and the attainment of auxiliary bridge balances during the measurement. A careful choice of the network topology allows the bridge to be self-compensating: the 4TP definition is in large part achieved by the behavior of the network itself without any adjustment. The additional circuitry required for impedance definition can therefore be simpler, the balancing procedure becomes easier, and a more robust 4TP can be achieved. This paper analyzes a current comparator bridge network with a topology featuring self-compensation. A digitally assisted test bridge has been implemented; test measurements on ac resistance comparison in the 25–100- $\Omega $ range at kilohertz frequencies are reported. [ABSTRACT FROM AUTHOR]

We present the latest improvements in the traceable measurement and generation of small electric currents. A central tool in our traceability chain for small direct currents is a new binary cryogenic current comparator (CCC) with a total of 18 276 turns. This 14-bit CCC is well suited for the calibration of high-value resistors and current amplifiers, but also for the direct amplification of small currents. A noise level of 5 fA/ \surd Hz at 0.05 Hz is routinely achieved. The systematic uncertainty due to noise rectification was exemplarily investigated in a ratio-error test configuration, showing that a total uncertainty of about one part in 10^{6} can be achieved at 100 pA. For further improvement, a new instrument was developed, the ultrastable low-noise current amplifier (ULCA). Its transfer coefficient is highly stable versus time, temperature, and current amplitude within a full dynamic range of ±5 nA. The ULCA is calibrated with the 14-bit CCC at high current amplitude, and allows the measurement or generation of 100-pA direct current with an uncertainty of one part in 10^{7}$ . The novel setup was successfully used to investigate the uncertainty of the established capacitor charging method. A quantum metrology triangle experiment based on the presented instruments is proposed. [ABSTRACT FROM PUBLISHER]

A setup based on a direct current (dc) comparator, typically employed in high-current low-resistance calibrations, has been developed for the accurate calibration of dc current ratios for dc currents up to 600 A. For primary currents above 100 A, multiple turns of the primary conductor are made through the device under test. A full uncertainty analysis reveals that the 1 part in 10^6 total expanded uncertainty ( $k = 2$ ) in a calibration of a zero-flux device is limited by the behavior of the device, in particular the instability and sensitivity to the position of the primary current conductor. [ABSTRACT FROM PUBLISHER]

A new current-comparator-based dual-channel calibration system for AC currents and AC voltages in the millivolt range has been developed. The range of generated currents is 1 mA–5 A, and the range of generated voltages is 1–500 mV. The calibration system in-phase and quadrature expanded measurement uncertainties ( $k=2$ ) are within 25\cdot 10^{\mathrm {\mathbf {-6}}} . Although the system has been developed primarily for operation at power frequencies, it is also capable of operating at frequencies up to 1000 Hz with slightly increased uncertainties. The traceability to SI units is established through the calibration of AC voltage by means of AC/DC transfer and DC voltage reference, standard resistor, capacitor, and current comparator ratios. [ABSTRACT FROM PUBLISHER]

We present here the concept of three-arm current comparator impedance bridge, which allows one to perform comparisons among three unlike impedances. Its purpose is the calibration of impedances having arbitrary phase angles against calibrated nearly pure impedances. An analysis of the bridge optimal setting and proper operation is presented. To test the concept, a two-terminal-pair digitally assisted bridge has been realized; preliminary measurements of an air-core inductor and of an $RC$ network versus decadic resistance and capacitance standards, at kilohertz frequency, have been performed. The bridge measurements are compatible with previous knowledge of the standard values with relative deviations of parts in 10^{-5} . [ABSTRACT FROM PUBLISHER]

The homogeneity of the lattice spacing of silicon single crystals was investigated by a self-referenced lattice comparator. Strain measurements were performed on single crystals from an ^28 Si ingot (Avo28), which was used to determine the Avogadro constant. A swirl pattern was observed for sample 9.R1 cut from the tail side of the Avo28 ingot. The lattice spacing distribution of seed-side sample 4.R1 was smooth and homogeneous. The lattice spacing distribution was larger for the sample with higher impurities of carbon and oxygen. [ABSTRACT FROM PUBLISHER]

This paper presents the design and implementation of a rail-to-rail 460-kS/s 10-bit successive approximation register analog-to-digital converter (ADC) for the power-efficient capacitance measurement. The specifications of ADC are optimized at system level, emphasizing the ADC following a switched-capacitor capacitance-to-voltage (C2V) converter. To be compatible to the output of C2V, a bootstrap switch with body effect reduction is adopted to provide the rail-to-rail processing ability. The charge redistribution converter is implemented by a single-ended cascaded binary-weighted capacitive digital-to-analog converter (DAC). The total area of the DAC array is not only limited by the matching behavior but also by the noise performance of C2V. To relax the settling requirement and improve the power efficiency, self-timing technique is employed which borrows extra half clock period for open-loop settling of preamps. The balance between noise and power consumption of dynamic comparator with preamps is also considered. The ADC circuit was implemented in 0.18- \mu m CMOS technology and occupies an active area of 0.18 \mathrm{mm}^{2} . The tested prototype achieves a signal-to-noise-plus-distortion ratio of 54 dB and a spurious-free dynamic range of 68 dB. The integral nonlinearity and differential nonlinearity are 0.5 and 0.34 least-significant-bit, respectively. The total power consumption is 21 \mu $ W corresponding to 110 fJ/conversion-step figure of merit. [ABSTRACT FROM PUBLISHER]

This paper presents the results of a comparison of active/reactive power meter calibrations between the National Institute of Standards and Technology and National Research Council. The comparison was implemented using a transfer standard consisting of a highly stable commercial sampling-type power/energy meter. Active and reactive power measurements were made at 120 V, 5 A, 50 Hz, and 60 Hz. For active power, the measurements were made at applied current phase angles of 0°, +60°, and −60°. For reactive power, the measurements were made at applied current phase angles of +60°, +90°, −60°, and −90°. The results of the comparison indicate agreement to within the stated uncertainties of the participants.11

Contribution of the National Institute of Standards and Technology, U.S. Department of Commerce, not subject to copyright in the United States. [ABSTRACT FROM PUBLISHER]

The development and testing results of a new current transformer (CT) test set at Physikalisch-Technische Bundesanstalt are described. The operation range for the ratio based bridge is intended for frequencies from 16.7 Hz up to 20 kHz. Equal setups of magnetically shielded current comparators with primary windings for rated currents from 100 mA up to 5 A convert the secondary currents of the standard CT and of the transformer under test (TUT) into proportional voltages. The errors of the TUT are calculated from the subsequent measurement of the complex voltage ratio. This current bridge and the voltage-ratio-based method allow comparing CTs with nonequal ratios. At 50 Hz, the measuring system offers an extended measurement uncertainty of less than 2 ppm or \(\mu \) rad, respectively. The bridge is verified for use with uncertainties of below 200 ppm or 400 \(\mu \) rad at a frequency of 20 kHz. [ABSTRACT FROM PUBLISHER]

Power consumption of high-speed low-resolution analog-to-digital converters (ADCs) can be reduced by means of calibration. However, this solution has some drawbacks such as time slot allocation for calibration and die area increase. This paper presents a 5-bit 1-Gs/s ADC without calibration, fabricated in 90-nm CMOS. Low power consumption has been ensured by operating at both architecture and comparator levels. A folded interpolated architecture has been adopted. However, compared to standard solutions that use static preamplifiers, the interpolation technique has been implemented by taking recourse to dynamic comparators, enabling significant power saving. Moreover, despite the high operating frequency, intrinsic matching has been ensured while keeping low power consumption. The ADC uses double-tail dynamic comparators, operating with a fixed bias current and with reduced kickback noise. Large input transistors are used to guarantee the targeted matching, thereby avoiding calibration. The ADC achieves 4.3b-ENOB (effective number of bits) and 260-MHz effective resolution bandwidth while consuming 7.65 mW from a 1.2 V supply. The ADC figure of meritis 0.39 pJ/conv. step, which is the state-of-the-art performance for an uncalibrated ADC at this sampling frequency and resolution. [ABSTRACT FROM AUTHOR]

With proper design, accurate current ratios of direct current comparators (DCCs) can be achieved between series and parallel connections of n sections of primary windings with the same nominal number of turns. Based on this principle, a DCC could be calibrated with the windings connected in series, then operated in parallel, at rated current and therefore have its current ratio accurately extended by n times. By keeping the geometric position of the primary windings symmetrically and rigidly fixed to the cores, the leakage fluxes and their effects on the DCC current ratios would be minimized and relatively unchanged between the series and parallel connections. Four DCCs with current ratios of 10 A:1 A to 5 kA:5 A have been developed with relative ratio errors less than 2\times 10^-8 to 5\times 10^-7, and calibrated by the series parallel method through only four step measurements. These measurement techniques for the self-calibration of DCCs with current ratios of 10 A:1 A to 5 kA:5 A and corresponding uncertainties from 1.2\times 10^-8 to 1.6\times 10^-7(k=2) are described. [ABSTRACT FROM PUBLISHER]

We have developed a binary compensation unit for balancing measurement bridges with cryogenic current comparators (CCCs) commonly used in resistance metrology. We present the basic design ideas for the new microcontroller-operated module. It offers balance over a gapless range of resistance ratios of the resistors to be compared. The binary setup allows for convenient calibration when being combined with a binary CCC. The calibration can be performed using the CCC's control electronics and software. Examples of measurements demonstrate the unit's high flexibility and stability of resistance calibration well below one part in 10^9 over a period of 21 hours. [ABSTRACT FROM PUBLISHER]

A double current method is presented for absolute measurements of the current dependence (power variation) of dc resistors. Based on the resistance measurement principle of a direct current comparator (DCC), and adding another DCC-based extender with a turn ratio 1:1, the testing current in resistors to be tested is accurately doubled. Through three comparative measurements with two reference standard resistors connected in series as Kelvin resistive bridge inner arms, the change of resistance caused by doubling the currents is measured. Cyclically done, absolute measurement of current or power factor is realized. Examples of the current dependence of some commercial low-temperature coefficient 1 \Omega standard resistors are given using the presented method and their results are analyzed. [ABSTRACT FROM PUBLISHER]

This paper introduces the structure and the working principle of a high-accuracy current comparator. This paper also indicates the primary source of error: the leakage capacitance coupling current between the turns of the secondary winding. In order to reduce this error, the secondary winding is wound with a coaxial cable. With good shielding, the error introduced by the connecting windings is minimized. This paper also presents a new self-calibration method for the 1:1 current comparator and an innovative design of the current comparator. The self-calibration method can also be used to calibrate multiratio current comparators with an uncertainty of less than 5\times 10^-7 at a primary current ranging from 5 A to 2000 A. [ABSTRACT FROM PUBLISHER]

This paper describes a method to calibrate high current (20 kA) transformers, using a current comparator with a maximum test current of 100 A as a primary standard. In order to fill the large gap in the test current between 20 kA and 100 A, two novel techniques are developed, i.e., 1) the current-ratio transfer standard (CRTS), and 2) the improved equivalent ampere-turn method. The CRTS is a two-stage current transformer with two selectable current ratios of 500A/5A and 100A/5A. The two ratios are realized by the selection of parallel or series combination in the primary windings of the CRTS. The design and the performance of the 100-A primary standard, a coaxial-type self-calibratable current comparator, is also described. [ABSTRACT FROM PUBLISHER]

This paper describes the realization of a new system for resistance scaling from 10 k\Omega to 100 T\Omega. The resistance unit has been transferred from the quantum hall resistance (QHR) primary resistance standard to the resistance standard with a nominal value of 10 k\Omega by a cryogenic current comparator. For further transfer of the resistance unit from 10 k\Omega to 100 T\Omega, Hamon transfer devices (Hamon networks) are used. For its complete realization five devices have been developed: 10–100–1000 k\Omega, 1–10–100 M\Omega, 0.1–1–10 G\Omega, 10–100–1000 G\Omega, and 1–10–100 T\Omega. The first two devices have a single insulation, and the next three have a double isolation. In the transfer devices with the double insulation, triax-type connectors are used. All transfer devices have individual temperature stabilization within \pm0.01^\circC. In the paper, the factors influencing device accuracy have been described. The insulation leakage is recognized, and the error caused by it is calculated. The guarding network for the new design of Hamon transfer devices is presented. Voltage coefficients of resistance and settling times of resistors used in these devices have been determined and discussed. Uncertainties for the Hamon transfer devices ratios have been calculated. Calibration results have been presented. The developed system is currently tested in the Central Office of Measures in Poland. [ABSTRACT FROM PUBLISHER]

A current comparator impedance bridge, suitable for the comparison of four-terminal-pair impedance standards having similar phase angles (e.g., resistors or capacitors) in the audio frequency range at 1 : 1 and 10 : 1 nominal ratios, is here presented. The bridge is digitally assisted: Its accuracy is granted by an electromagnetic device, a high-permeability core current comparator, but the voltages and currents needed to achieve both principal and auxiliary equilibria are generated by programming a polyphase direct-digital-synthesis generator. The resulting implementation is neat and simple and does not include variable components such as decade dividers. The measurement is semiautomated: After an initial setting, the equilibrium can be achieved in a few minutes. Measurements performed on calculable resistors give a base accuracy of a few parts in 10^7 at kilohertz frequency, sufficient for calibration purposes, with the potential for further improvement. [ABSTRACT FROM PUBLISHER]

An improved power standard derived from a current comparator power bridge for calibrating active/reactive power and energy meters under sinusoidal conditions is described. Measurements can be made at any power factor from zero lag through unity to zero lead, at positive or negative power, at 120 V, 5 A, and 50 or 60 Hz. The improved power standard has an estimated uncertainty of not more than 2.5 \mu\W/VA at k = 1. Special high-accuracy current and voltage range extenders have been incorporated to extend the current and voltage ranges up to 200 A and 1200 V, respectively. [ABSTRACT FROM PUBLISHER]

A digital H\infty controller for a two-terminal cryogenic current comparator is designed. To this end, a set of mathematical models covering the actual system is proposed. Simulation results compare the open- and closed-loop systems based on the proposed controller and the traditional integral control. According to these results, the new controller can significantly reduce the noise in the superconducting quantum interference device sensor. [ABSTRACT FROM PUBLISHER]

This paper describes the calculation of the magnetic shielding effectiveness in current comparators, considering the air gap which is inevitable for the magnetic shielding. The method was verified to be accurate and effective by finite-element method analysis. Experiments were implemented to investigate the effect of the air gap as well. [ABSTRACT FROM PUBLISHER]

We propose a new design for a 10-\k\Omega quantized Hall resistance (QHR) array device. This design realizes quantized resistance values that approach decade values with fewer Hall bars. In this design, the 10-\k\Omega QHR array device consists of only 16 Hall bars, and this number is about 16 times lower than that in the previous design, although the nominal value is identical to the previous one. The nominal value of this device shows a relative difference of only 0.034 \mu\Omega/\Omega, based on RK - 90\ (=25\,812.807\ \Omega), from the exact value of 10 \k\Omega. This fact might allow us to evaluate each Hall bar in the array device. The parameters of this 10-\k\Omega QHR array device were measured by a conventional QHR and cryogenic current comparator using the 100- \Omega standard resistor. According to the measurement, the value of the 10-\k\Omega QHR array device agrees with its nominal value within around one part in 10^8. In the same manner, new combinations of Hall bars were designed for the 100-\Omega–1-\M\Omega range. [ABSTRACT FROM PUBLISHER]

In this paper, an approach for the current-consumption measurement of a field-programmable gate array (FPGA)-based embedded system is presented. This approach is based on the current conversion to pulsewidth using the external-to-FPGA capacitor charging circuit and comparator. The pulsewidth is then measured using the timer synthesized inside the FPGA. Measurement uncertainty budget analysis is performed. It reveals the parameters mostly affecting steady-state current measurement uncertainty. Sources contributing to the budget of current measurement uncertainty include directly measured pulsewidth, manufacturing scattering of measurement setup component parameters, and their fluctuations in response to the measured current value. A calibration procedure enabling to reduce the influence of charging circuit component manufacturing tolerances on measurement uncertainty is suggested. The current measurement prototype is developed and tested. Measured pulsewidth jitter is estimated experimentally using the prototype. The jitter influence on measurement uncertainty is modeled by including the corresponding quantity in the measurement model. The influence of the temperature on measurement uncertainty is estimated using Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

A long settling time of the bridge voltage in resistance comparison setups with cryogenic current comparators might become crucial with respect to the type-A uncertainty, because it effectively limits the frequency of current reversals. Using a new bridge voltage detector with considerably increased bandwidth, we were able to trace the transient distortions caused by current reversal. Significant influence of the cabling is observed. Comparing a 12.9-\k\Omega quantum Hall resistor and a 100- \Omega standard resistor, we achieved an expanded type-A uncertainty of about three parts in 10^10 after 24 min of measurement for current reversal frequencies down to 100 mHz. [ABSTRACT FROM AUTHOR]

The development of a computer-controlled current-comparator-based calibration system to determine the current ratio errors of high-voltage conventional and nonconventional current transformers (CTs) under actual operating conditions of high-voltage and distorted current waveforms up to 100 kV and 2000 A is described. The ratio errors of a CT are affected by the applied high voltage due to capacitive currents flowing in its winding. The errors are also affected by the phase angle of the primary currents with respect to the operating high voltage. Therefore, the new calibration system allows the phase angle of the test primary currents to be adjusted at power factors of zero lag through unity to zero lead. The uncertainty k = 2 of the new calibration system is estimated to be not more than 20 \times 10^-6 for both the in-phase and quadrature components of the measured ratio errors. [ABSTRACT FROM AUTHOR]

The Korea Research Institute of Standards and Science (KRISS) has established a reference 400-kV capacitive voltage divider for the purpose of calibrating industrial high-voltage measuring systems on site. In order to confirm the performance characteristics of the divider, a comparison of the calibration systems between KRISS and National Research Council Canada with the divider used as the transfer standard was conducted. This paper presents the comparison results and its analysis in obtaining the voltage-dependent performance characteristics of the reference 400-kV voltage divider over its entire range. [ABSTRACT FROM AUTHOR]

A modified technique for calibrating both the capacitance-ratio and dissipation-factor (DF) dials of a current-comparator-based high-voltage capacitance bridge has been developed at the Korea Research Institute of Standards and Science (KRISS). The capacitance-ratio and DF dials are calibrated in the ratio range from 1/1 to 1000/1 and in the DF range from 10 \times 10^-6 to 1 \times 10^-1 for both positive and negative polarities. From the calculated and measured values of the corresponding dial balanced readings, the errors in the capacitance-ratio- and DF-dial readings are derived. The relative uncertainty of the modified calibration technique is also obtained to be not more than 10 \times 10^-6 of unity for the ratio-dial calibration, whereas the relative uncertainty of the DF dials from 1 \times 10^-3 to 1 \times 10^-1 is not more than 0.4% of the dial indication except the dissipation lower than 1 \times 10^-3 for which the corresponding absolute uncertainty is 5 \times 10^-6. The comparison results of the calibration performed at KRISS and the National Research Council of Canada show a good consistency with the measurement uncertainty. [ABSTRACT FROM AUTHOR]

A new inductance comparator bridge has been constructed at the Institute of Measurements, Electronics, and Automatic Control (Gliwice, Poland) for the calibration of inductance standards in the frequency range of 100 Hz–10 kHz. Since the instrument belongs to the class of unbalanced transformer bridges, very accurate measurement of the voltage on the diagonal of the bridge is required. A vector voltmeter which enables the precise measurement of both components of the unbalance voltage is described in this paper. We report on the realization and characterization of the voltmeter which is an integral part of the new inductance comparator bridge. [ABSTRACT FROM AUTHOR]

Abstract-In this paper, we discuss the possibility of realizing high-accuracy digital-analog (DA) converters by exploiting the properties of R/βR(β > 2) ladder networks. Extensive simulations demonstrate that, if a proper value of β is chosen, high accuracy can be obtained by resorting to a very simple self-calibration algorithm. This is true, even in the case of large tolerance values for the resistors that make up the ladder network. Such a result may allow the design of a high-accuracy very low cost converter. The effect of the offset of the comparator needed for the self-calibration algorithm is also discussed. [ABSTRACT FROM AUTHOR]

We present an uncertainty evaluation of a new cryogenic current comparator (CCC) bridge that is designed to compare two-terminal 1 and 10 MΩ standard resistors with the quantized Hall resistance (QHR) and scale from these decade values to other decade values between 10 kΩ and 1 GΩ Use of the bridge over a wide range of resistance values results in a spectrum of dominant contributions to the uncertainty budget, and this analysis helps determine the optimum parameters of the measurements. Our theoretical analysis is compared with experimental data. [ABSTRACT FROM AUTHOR]

We have developed and tested an internally damped cryogenic current comparator (CCC) with a main 1 : 20000 winding ratio for the accurate measurement of small electrical currents. The key features of the CCC are the use of resistive CuNi wire for the windings and brass internal shields for additional damping of the internal resonance of the CCC. Inductance measurements of the CCC overlapping tube at 300 and 77 K, as well as the superconducting quantum interference device (SQUID) noise spectra of the complete CCC setup at 4 K, confirm the effectiveness of the damping of the CCC self-resonance with respect to other designs. At 4 K, the CCC is remarkably stable in measurements with external feedback mode; even mains-operated current sources can be used without unlocking the SQUID null detector of the measurement bridge. First measurements of currents in the range of 100-300 pA using this CCC are performed, resulting in deviations from the expected value in the range of about 20-50 μA/A. [ABSTRACT FROM AUTHOR]

We describe a mass comparison system in which a test mass artifact in air can directly be compared to a standard mass artifact in a vacuum using the same high-precision comparator balance. The system uses a magnetic levitation technique to couple the weighing pan of the comparator balance in a vacuum to the test mass in air. We will discuss motivation, design considerations, and preliminary results. [ABSTRACT FROM AUTHOR]

The dynamic range, ratio balance error, and current resolution have been evaluated for an upgraded prototype high-temperature superconductor (HTS) dc current comparator, which has been previously developed and demonstrated for the noninvasive sensing of charged particle beams. The addition of a custom- designed 2-SQUID gradiometer coupled to an S-shaped current concentrator is expected to provide an improvement in the flux sensitivity, as well as a reduction in the stray coupling of external fields. In the longer term, when the limiting factors have been fully identified, the technique may be considered for potential applications in fundamental metrology, for example, in a physical determination of the faraday by an ion-collection method. [ABSTRACT FROM AUTHOR]

A new versatile electronically coupled current comparator is presented in the paper. Its simpler design is more convenient for manufacturing yet it retains high accuracy in either manual or automated version. It provides a resolution of one part in 106 and has an estimated uncertainty less than 5.10-6 in magnitude and less than S μrad in phase at power frequencies. [ABSTRACT FROM AUTHOR]

A resistance bridge based on a cryogenic current comparator has been built at the Istituto Elettrotecnico Nazionale "G. Ferrails" (lEN). The use of this bridge simplifies the scaling down from the quantized Hall resistance to decadic standard resistors, at the same time reducing; the measurement uncertainty. The bridge is described and the result of a comparison at the level of 100 Ω, with the traditional scaling method used at IEN is reported. The two methods agree well within their uncertainties, for which detailed uncertainty budgets are given. [ABSTRACT FROM AUTHOR]

Measurements of room-temperature 100 MΩ standard resistors and cryogenic thin-film resistors based directly on a quantized Hall resistance standard have been made with a cryogenic current comparator (CCC) bridge. This 15 496:2 ratio CCC attains a current sensitivity of 10.7 fA/Hz½ in measurements of cryogenic thin-film resistors, without extensive shielding or filtering. A resistive primary winding helps the CCC maintain stability in the presence of external noise. The resistive-winding technique may be useful for the absolute measurement of small currents delivered by single-electron tunneling devices. [ABSTRACT FROM AUTHOR]

A new latching comparator probe is described. The probe is being developed as part of an effort to augment voltage measurement capability in the 10 Hz to 1 MHz frequency range. The probe offers an input voltage range of ± 10 V, input impedance of 1 MΩ and root mean square noise referred to the input as low as 55 &micro V. The probe's 3-dB bandwidth is approximately 20 MHz. Total harmonic distortion is as low as --93 dB at 50 kHz. Gain flatness is within ± µ V/V from 100 Hz to 100 kHz. Improved step settling performance is achieved using a technique that minimizes circuit thermal errors. The probe's input range can be extended with a frequency-compensated 1-MΩ input impedance attenuator allowing measurement of pulses in the microsecond regime up to 100 V. The attenuator can be compensated further with a digital filtering algorithm to achieve gain accuracy better than 100 µV/V. [ABSTRACT FROM AUTHOR]

Presents a study that dealt with the improvements of the National Bureau of Metrology-LNE single-electron tunneling (SET) experimental setup based on a cryogenic current comparator devoted to the high-accuracy measurement of current delivered by a single-electron tunneling pump. Improvement of the experimental setup; Characteristics of the R-pump in static mode; Conclusion.

Presents a study that developed a 1:30000 winding ratio cryogenic current comparator (CCC) for measurement of small currents. Experimental set up; Measurements on a dummy CCC; Conclusion.

Presents as study that examined high-temperature superconductor cryogenic current comparator for non-invasive sensing of charged particle beams. Experimental approach; Detection of a charged particle beam; Conclusion.

Presents a study which described a noninvasive and potentially absolute method for the real-time measurement of an ion or electron beams. Principle of the method; Current comparator design; High-temperature superconductor current comparator performance.

Presents a study which developed a split-toroid high-temperature superconducting (HTS) cyrogenic current comparator (CCC). HTS CCC designs; Prototype construction; Results.

Presents a study which developed a cyrogenic current source with linear output up to 1 ampere, by combining a 1 milliampere current source with a cyrogenic current comparator that operates as a current amplifier. Outline of the measurement apparatus; Structure and performance; Experimental results.

Presents a study which reported the status of the experimental set-up on the development of a current standard based on single electron transistor pumps. Discussion on the wiring of the dilution unit; Cyrogenic current comparator (CCC)-based amplifier; Description of the first experiments on a set with a CCC.