DC Voltage Calibrator Research Articles

Development of portable dc voltage calibrators with additive offsets adjusting

Improvement of portable equipment for controlling the DC voltage measuring channels of cyber-physical systems at the operating sites is proposed. Additive offsets and drifts make a dominant contribution to the error of portable DC voltage calibrators. Automatic correction based on the method of double switching inversion provides the opportunity to increase the productivity of multichannel system voltage meters at the operating sites. It is shown that the additive offsets during the DC voltage reproduction, in addition to the equivalent offset voltages of the operational amplifiers, ADCs or DACs, are caused by common type noises and leakage currents through the isolation of the power supply units. In the developed structure of the DC voltage calibrator, it is proposed to use the method of double switching inversion with subsequent analog averaging of the output signal for the automatic correction of the additive offsets. The error analysis and simulation showed the principal possibility of the calibrator additive offsets correction to the values limited by the non-identity of parameters of the closed pairs of switches. The analysis of the results of experimental studies of the voltage calibrator layout showed the invariance of the reproduced voltages from the voltage value and the location of the simulator of the additive error component in the layout structure. The uncorrected error value in the manual mode did not exceed ±1 μV for all reproduced values of the output voltage of the layout. It has been experimentally shown that the minimum value of the uncorrected error lies at a switching frequency of about 1.2 kHz within ±5 μV. The developed scheme can be implemented in the basis of programmable systems on the chip, which significantly improves the metrological characteristics, reduces the cost and unifies portable voltage calibrators and DC resistance simulators.

Metrological Properties Analysis of Portable Dc Voltage Calibrator with Errors Correction

It is shown that, it is expedient to use a DC voltage calibrator with automatic error correction by double switching inverting method and averaging the output voltage with a low frequency filter for operational monitoring and remote calibration of measuring channels was shown in this paper (Figre 1). A comparison of the dynamic and metrological characteristics of DC voltage calibrators with single- and two-period demodulation has been carried out and operator and time mathematical models have been proposed (Figure 2). Computer simulation of both structures of voltage calibrators in manual and automatic control modes was carried out. The results of experimental studies of a DC voltage calibrator model with single-phase demodulation and averaging by an active low frequency filter are described (Figure 3). Conclusions about the good convergence of experimental results with theoretical assumptions were made; the unadjusted value of the additive displacements in the manual control mode did not exceed ±1 μV. A certain frequency dependence of the additive displacements unadjusted value of the made model has been established and it is determined that its minimum value is at a frequency near 1.2 kHz. Conditions of practical realization of a DC voltage calibrator with automatic correction of additive displacements by the proposed method of switching inverting in the basis of programmable systems on a chip are discussed. Emphasized that in the future it will also adjust the multiplier and additional errors during the reproduction of DC voltage small values in working conditions.
 The scientific results, presented in this article, were obtained in the frame of research project number 0115U000446, 01.01.2015 - 31.12.2017, financially supported by the Ministry of Education and Science of Ukraine.

High performance selectable-value transportable high dc voltage standard

Abstract At National Institute of Metrological Research (INRIM), a selectable-value transportable high dc voltage standard (THVS) operating in the range from 10 V to 100 V in steps of 10 V, was developed. This standard was built to cover the lack of high level dc voltage standards at values higher than 10 V to employ mainly as transportable standard for inter-laboratory comparisons (ILCs) or eventually as laboratory (local) high level dc voltage standard. An electronic technique was used to improve the THVS accuracy of the high values. The THVS shows lower noise, better short- term stability and accuracy than top level dc voltage and multifunction calibrators (MFCs) and satisfactory suitability to be transported. The project is extensible to 1000 V.

Аналіз частотних характеристик коригування адитивних зміщень у калібраторах напруги постійного струму

Аналіз частотних характеристик коригування адитивних зміщень у калібраторах напруги постійного струму

Удосконалення структурних методів коригування адитивних похибок калібраторів напруги постійного струму

Удосконалення структурних методів коригування адитивних похибок калібраторів напруги постійного струму

Evaluation of Two Alternative Methods to Calibrate Ultrahigh Value Resistors at INRIM

In the framework of the preparation of the National Institute of Metrological Research (INRIM) to its participation at the “Supplementary Comparison EURAMET.EM-S32 Comparison of Resistance Standards at 1 TΩ and 100 TΩ,” an evaluation of two measurement techniques for high resistance measurements at INRIM has been made. The first method, working between 10 MΩ and 1 TΩ, is based on a digital multimeter and on a dc voltage (dcv) calibrator, the second, working up to 100 TΩ, is based on a modified Wheatstone bridge with two programmable dcv calibrators in two arms of the bridge and a programmable electrometer as null detector. A description of both methods, a detailed uncertainties budget at 1 TΩ at 1000 V level according to the ISO Guide to the Expression of Uncertainty in Measurements, and the comparison of the results at 100 GΩ and at 1 TΩ are reported.

Hamon 10 × 100 MΩ resistor based traceable source for calibration of picoammeters in the range 100 pA–100 nA

This paper describes a measurement method developed at National Institute of metrological Research (INRIM) to calibrate picoammeters in dc current from 100 pA to 100 nA. The current source is based on a traceable to the dc resistance national standard 10 × 100 MΩ Hamon resistor developed at INRIM and on a traceable to the dc voltage national standard high precision dc voltage calibrator. The expanded uncertainties of the method for the calibration of picoammeters span from 9.4 × 10 −4 for the gain of a picoammeter at 100 pA to 4.0 × 10 −4 for the gain at 100 nA. A detailed uncertainties budget at 10 nA level and the results of a comparison with a different technique are also reported.

Hamon-Guarded $10 \times 100\ \hbox{M}\Omega$ Network to Increase the Accuracy of the Transfer of the Resistance Unit up to 1 $\hbox{G}\Omega$ at INRIM

In the framework of the revision and optimization of the measurement techniques for high-resistance measurements at the National Institute of Metrological Research (INRIM), a 100 MOmega-step Hamon-guarded network was projected and built. With this transfer standard, the 2sigma uncertainty of the maintained 1 GOmega standard at INRIM is now on the order of 7.0 times 10-6 at a measurement voltage of 100 V. Details of the Hamon network and stability data in parallel configuration are given and discussed. The result of a verification of the performance of the Hamon network with a measurement method based on a digital multimeter (DMM) and a dc voltage calibrator (DcVC) is reported. A description of the measurement steps from 10 kOmega to 1 GOmega together with an uncertainty budget is also reported.

Metrological management of the high dc resistance scale at INRIM

In the framework of the revision of the high dc resistance scale from 10kΩ to 1TΩ at National Institute of Metrological Research (INRIM) a measurement method for calibration of high value resistors based on the use of a digital multimeter (DMM) and of a dc voltage calibrator (DCVC) was projected, developed and characterized. A method based on the Hamon scaling technique was revised and extended to 1GΩ. Two other methods, based respectively on a modified Wheatstone bridge and on a current comparator bridge, were implemented. A new 100MΩ step Hamon standard, a humidity generator to characterize high value resistors vs. relative humidity and a scanner for high resistances were developed and characterized. The relative 2σ best measurement capabilities, obtained in the range 10kΩ÷1TΩ at INRIM with all these methods, span from 2.0×10−7 of the 10kΩ standard resistor at the measurement voltage of 10V to 1.0×10−3 of the 1TΩ standard resistor at a voltage of 100V. The relative standard uncertainties of the utilized methods at INRIM are summarized.

A precision setup and method for calibrating a dc voltage divider's ratios from 10 v to 1000 v

Resistive dividers are often used to calibrate DC voltage calibrators and voltmeters above 10 V, with ratio uncertainties lower than 10/sup -6/. The dividers need therefore to be calibrated with uncertainties lower than 5/spl times/10/sup -7/. A setup and method for the calibration of a resistive divider at its working voltage has been developed. The repeatability was found to be good enough to give standard deviations of the mean lower than /spl plusmn/1/spl times/10/sup -8/ in the measured ratio 1000/10. The total uncertainties were estimated to be less than /spl plusmn/1.5/spl times/10/sup -7/ (k=1) for all measured ratios.

DC voltage calibrator based on an array of high-temperature superconductor josephson junctions

We have developed and investigated the main parts of a voltage calibrator with an output voltage up to 10 V. The calibrator is based on a quantum DC voltage which is generated by an array of high-temperature superconductor Josephson junctions. The described concept and the demonstrated parameters of the main parts of the instrument show, that a combined uncertainty of the output voltage of a few parts in 10/sup 8/ can be obtained.

A new automatic reference and switching unit for calibration of high value resistors in the range 100 kΩ to 10 TΩ

We describe a Reference and Switching Unit (RSU), that, with a digital multimeter (DMM) and a dc voltage calibrator, constitutes a system for calibration of standard resistors in the range 100 kΩ–10 TΩ at measurement voltages up to 1000 V. This system represents an implementation of a DMM-based system already developed at IEN. We report the characteristics of the DMM-based system, the metrological and electronic features of the RSU, the uncertainty levels that can be achieved with the DMM-based and whit the RSU-based systems. Finally, we show the obtained results in order to check the compatibility of the two systems in the calibration of standard resistors in the range 1 GΩ–1 TΩ. The 2 σ best measurement capabilities of the RSU-based system span from 6.3×10 −6 for the calibration of a 100 kΩ standard resistor at 10 V, to 1.2×10 −3 for the calibration of 10 TΩ standard resistor at 1000 V.

The electrical DC resistance scale from 100 kΩ to 1 TΩ at IEN

At IEN, the scale of resistance in the field 100 k/spl Omega/ to 1 T/spl Omega/ has been revised through the characterization of a series of new standard resistors. The preliminary study, realization and characterization of four measurement methods are also described in this paper. The complete description of a new automatic method for the calibration of high-value standard resistors, particularly in the range 10 M/spl Omega/-1 T/spl Omega/, and their measurement at different voltage levels are also reported. It makes use of a programmable high-stability dc voltage calibrator which supplies a voltage V/sub out/ to the series of an unknown resistor R/sub x/, and of a standard resistor R/sub s/. A high-precision programmable multimeter (DMM) is used to measure V/sub out/ and the voltage Vs across the standard resistor, from which the value of the current I is determined. The value of R/sub x/ is given by R/sub x/=(V/sub out/-V/sub s/)/I. The best measurement capabilities of IEN using these four measurement methods span from 0.7/spl times/10/sup -6/ for the calibration of the 100 k/spl Omega/ standard resistor at the measurement voltage of 10 V, to 7.1/spl times/10/sup -4/ for the calibration of 1 T/spl Omega/ standard resistor at the measurement voltage of 500 V.

A microprocessor-controlled current-comparator-based DC voltage calibrator

A microprocessor-controlled current-comparator-based dc voltage calibrator is described. A self-balancing dc comparator is used to establish voltages proportional to a reference signal. The calibrator features an automatic self-calibration mode, two ranges of −10 to +10 V and −120 to +120 V with an output uncertainty of less than 2 and 3 parts per million (ppm) of full scale, respectively, a resolution of 1 ppm, and a linearity error of less than 1 ppm of full scale.

NBS Provides Voltage Calibration Service in 0.1-10-Hz Range Using AC Voltmeter/Calibrator

Prompted by the need to support vibration and pressure measurements at frequencies down to 0.5 Hz (with expected future needs to 0.1 Hz), NBS now offers a calibration service for voltage standards and rms voltmeters in the range of 0.1-10 Hz. The means for the service is an Voltmeter/Calibrator, an NBS-developed instrument containing an rms digital voltmeter and ac and dc voltage calibrators. The methods used to calibrate the ac voltage calibrator are discussed; also, application of the ac Voltmeter/Calibrator to the calibration of customers' voltage and voltmeter standards is described. Finally, a multifrequency voltage reference source with frequency-independent amplitude is proposed as a more suitable transfer standard than thermal voltage converters (TVC's) for the 0.1-10-Hz range.

Utilization of R345 and R309 potentiometers as dc-voltage calibrators

Utilization of R345 and R309 potentiometers as dc-voltage calibrators