Sampling Voltmeter Research Articles

Constructing an uncertainty budget for voltage RMS measurement with a sampling voltmeter

This paper presents a way of constructing an uncertainty budget for root mean square (RMS) voltage measurement with an integrating sampling voltmeter and a discreet Fourier transform (DFT) algorithm. The construction of an uncertainty budget based on the Monte Carlo method is proposed. Such a budget makes it possible to analyse metrological properties of RMS measurement, especially in cases difficult to realize by the classical method of uncertainty determination. An application of the proposed research method is illustrated by voltage RMS measurement with a high-accuracy HP3458A sampling voltmeter. Selected simulation results have been experimentally verified.

Linearity evaluation of high-speed sampling ADC board

There are growing demands on the evaluation of accuracy for high-speed analog-to-digital converters which are increasingly needed in electrical metrology these days. Here, we have developed a system to measure the linearity error of analog-to-digital converters by adopting a reference sampling voltmeter and a dummy waveform generator. With the measurement setup, we evaluated the linearities for three units of Δ-Σ analog-to-digital converter, NI-5922, combined with three different PXI chassis. We found that the maximum linearity error can change with the PXI chassis up to about 15μV/V.

Calibration of Defibrillator Analyzers

Abstract:The Standards and Calibration Laboratory (SCL) in Hong Kong has set up a calibration facility for defibrillators and defibrillator analyzers. Defibrillators are medical devices designed to resume the normal heart pulse of a patient by discharging energy pulses to a person who is suffering from an emergency cardiac attack. They are commonly used in hospitals and medical institutes. At the SCL, the energy delivered by a defibrillator is measured using a high quality digital sampling system. The system includes a high voltage divider, a sampling voltmeter, an impedance analyzer, and a control computer. The sampled voltage waveform is digitally processed to derive the delivered energy. The system can also be used to check the accuracy of a defibrillator analyzer. The sampling system and its signal processing are described in this paper. To ensure the accuracy of the sampling system, it is calibrated against the laboratory's voltage and time reference standards. A standard waveform with calculable ene...

Generation of Reference DC Currents at 1 nA Level With the Capacitance-Charging Method

The capacitance-charging method is a well-established and handy technique for the generation of dc current in the 100 pA range or lower. This method involves a capacitance standard and a sampling voltmeter, highly stable devices easy to calibrate, and it is robust and insensitive to the voltage burden of the instrument being calibrated. In this paper, we propose a range extender amplifier, which can be employed as a plug-in component in existing calibration setups, and allows the generation of currents in the 1 nA range. The extender has been employed in the Istituto Nazionale di Ricerca Metrologica setup and validated with two comparisons at 100 pA and 1 nA current levels. The calibration accuracy achieved on a top-class instrument is 5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> at 1 nA.

Porównanie właściwości algorytmu DFT i klasycznego w pomiarze napięcia z zastosowaniem woltomierza próbkującego

The paper presents research results of metrological properties of algorithm DFT (4) and classical (5) for determining the RMS sinusoidal voltage measurements using an integrating sampling voltmeter. Tests were performed comparing measurement uncertainty calculated using a Monte Carlo method for both algorithms. Analyses were performed for selected, the most important sources of RMS voltage measurement uncertainty. Based on the results, it was found that the properties of both algorithms differ only in less accurate measurements. Below tens of ppm level voltage measurement uncertainty algorithms return the same results. (Comparison of DFT and classical algorithm properties in voltage measurement using a sampling voltmeter) Slowa kluczowe: pomiar napiecia skutecznego, algorytm DFT, algorytm klasyczny, niepewnośc pomiaru, metoda Monte Carlo, woltomierz probkujący.

Analog-to-digital conversion for low-frequency waveforms based on the Josephson voltage standard

A waveform synthesizer adopting a superconductor–normal metal–superconductor junction array has been developed, which can generate arbitrary stepwise waveforms with a number of quantum-voltage steps up to 1 V level amplitude. As an application of the synthesizer, we have built a sampling voltmeter that measures the differential voltages between a sinusoidal waveform produced by a semiconductor-based ac source and the Josephson waveforms. We carried out extensive sampling measurements for a 50 Hz sine wave with 1 V amplitude, applying sampling apertures in the range of 55 µs ⩽ta ⩽ 130 µs and using Josephson waveforms with 32, 60, 80 and 100 quantum steps. From the measurements, the amplitude of the ac waveform was determined with a type A uncertainty (k = 2) of 0.15 µV. Also, we elucidated how the phase jitter in the ac waveform is reflected in the overall uncertainty for the measurements. The type B uncertainty due to the jitter is at least one order of magnitude smaller than the type A uncertainty.

Traceability of Voltage Measurements for Non-Sinusoidal Waveforms

This paper describes the result of work performed at the Laboratoire National de Metrologie et d’Essais (LNE) aiming at developing a standard system to measure RMS value and harmonic contents of distorted voltage waveforms by means of a sampling voltmeter. Thermal converters are used to trace the RMS value to the SI units. The error of the DVM has been generally found less than 10 μV/V up to 2 kHz but can reach about 50 μV/V at 2.5 kHz for RMS voltage measurements for sine waves. For distorted waveforms, deviations within 15 μV/V have been obtained whatever the total harmonic distortion of the waveforms.

Influence of Sampling Voltmeter Parameters on RMS Measurements of Josephson Stepwise-Approximated Sine Waves

A binary Josephson-array voltage standard was used to investigate the influence of device settings on the reading of an 81/2-digit sampling voltmeter. This voltmeter is the heart of the primary standard for power at 50 Hz or 60 Hz at several National Metrology Institutes (NMIs). In this paper, we present results on the influence of the voltmeter synchronization and measurement parameters on the root-mean-square (RMS) measurements of Josephson stepwise-approximated sine waves for different frequencies. Our results show that for aperture times above 100 mus, the measured RMS voltage shows a large step in value with respect to shorter aperture times and is much more accurate. Furthermore, to obtain 0.2 muV/V accuracy, we show that for stepwise-approximated sine waves at 53 Hz, delay times higher than 10 mus are necessary. A slight delay time dependence limits the accuracy for frequencies above a few hundred hertz.

Precision Differential Sampling Measurements of Low-Frequency Synthesized Sine Waves With an AC Programmable Josephson Voltage Standard

We have developed a precision technique to measure sine-wave sources with the use of a quantum-accurate AC programmable Josephson voltage standard. This paper describes a differential method that uses an integrating sampling voltmeter to precisely determine the amplitude and phase of high-purity and low-frequency (a few hundred hertz or less) sine-wave voltages. We have performed a variety of measurements to evaluate this differential technique. After averaging, the uncertainty obtained in the determination of the amplitude of a 1.2 V sine wave at 50 Hz is 0.3 muV/V (type A). Finally, we propose a dual-waveform approach for measuring two precision sine waves with the use of a single Josephson system. Currently, the National Institute of Standards and Technology (NIST) is developing a new calibration system for electrical power measurements based on this technique.

The Josephson-Effect-Based Primary AC Power Standard at the PTB: Progress Report

This paper reports the incorporation of a Josephson waveform synthesizer (JWS) into the primary standard for AC electrical power at the Physikalisch-Technische Bundesanstalt (PTB). The increase to 10 V of the amplitude delivered by the JWS has allowed matching of the levels of the signals measured to determine the active, reactive, and apparent power-at the 120-V and 5-A level, which is also measured by the device under test. The inherent noise- and drift-free voltages delivered by the JWS allow calibration of the core sampling voltmeter of the PTB primary power standard with an uncertainty of 0.4 muV/V(k = 1) in 100 signal periods and as part of the measuring sequence.

Primary AC Power Standard Based on Programmable Josephson Junction Arrays

Josephson series arrays have been operated as digital-to-analog converters with fundamental accuracy to generate precision waveforms with accuracies better than one part in 107 at power frequencies. These waveforms have been used in the past to calibrate the sampling voltmeter in the primary standard for electrical power at the Physikalisch-Technische Bundesanstalt (PTB). The present contribution reports the integration of such a Josephson waveform synthesizer into the PTB primary power standard in order to continuously calibrate the sampling voltmeter and thus reduce the uncertainty for the measurement of active, reactive, and apparent power at the 120-V and 5-A levels

Quasi-Synchronous Microcontroller-Based Highly Accurate Digital Sampling of AC Signals

An easy-to-use and low-cost quasi-synchronous multichannel digital sampler controller to aid routine laboratory ac measurements by digital sampling is described. Using a single digital sampling voltmeter, accurate measurements of ac quantities can easily be done with uncertainties of a few microvolts per volt. Measurement results and consistent uncertainty calculations are described

Evaluation of the Uncertainties in the Measurement of Distorted Power by Means of the IEN Sampling System

A method for the uncertainty evaluation in the measurement of power in distorted signals is described. The power is obtained by a sampling system, which acquires the voltage and current and computes the power from the harmonic components obtained by the best fit. An equivalent algorithm is applied to derive a simplified relation between the correlation matrix of the harmonics and that of the samples. The uncertainties are then evaluated by a model of the uncertainty of a single sample given by the manufacturer of the sampling voltmeters.

Characterization of a High-Resolution Analog-to-Digital Converter With a Josephson AC Voltage Source

A Josephson AC voltage source was employed to characterize the dynamic behavior of a high-resolution 28-bit (8.5-digit) integrating analog-to-digital converter of a digital sampling voltmeter (DSV), which is widely used in AC metrology at the Physikalisch-Technische Bundesanstalt. Extensive measurements were carried out to validate previous mathematical models of the DSV when sampling AC signals. The characterization method is based on the discrete Fourier transform applied on sampled data of the ADC and on the known Josephson plateau values for quantifying the ratio of AC quantities and the nonlinearities of the DSV. The method shown allows considerable improvement of the accuracy of sampling techniques at low frequencies (DC up to some kilohertz) to be attained.

A new transfer device for the NRC Travelling Standard Program

This paper describes a computer controlled measurement system, which is now used as a transfer device for the National Research Council of Canada (NRC) Travelling Standard Program. The measurement system is based on two sampling voltmeters, custom built voltage and current input circuits, and a computer used for data acquisition and analysis. The new transfer device is used on-site with a stable AC source of voltage and current and a new 12-position pulse-frequency comparator to provide calibration and traceability for the revenue billing electrical quantities of the reference standards maintained by Canadian electrical utilities and electricity meter manufacturers. The accuracy of the measurement system is better than 30 parts in 10/sup 6/ for all the electrical quantities currently requiring traceability for revenue billing purposes. The repeatability of the new transfer device before and after an on-site calibration is generally better than 15 parts in 10/sup 6/.

A test system for calibrating flickermeters

This paper describes a new calibration system for testing flickermeters. The test system is used to generate and measure all the combinations of amplitude changes and frequencies required for calibrating flickermeters. Two computer-controlled waveform generators are used to produce the test conditions. The percent modulations of the test waveforms are measured with two high accuracy sampling voltmeters. Digital logic and software control ensures that the modulated signals are only measured when either maximum or minimum modulation occurs. Test data indicates that the percent modulation of the waveforms generated by the calibration system for square wave and sinusoidal modulations are within 0.002% and 0.005%, respectively, of the nominal values specified in IEC Standard 61000-3-3.

Nonrandom quantization errors in timebases

Timebase distortion causes nonlinear distortion of waveforms measured by sampling instruments. When such instruments are used to measure the RMS amplitude of the sampled waveforms, such distortions result in errors in the measured RMS values. This paper looks at the nature of the errors that result from nonrandom quantization errors in an instrument timebase circuit. Simulations and measurements on a sampling voltmeter show that the errors in measured RMS amplitude have a nonnormal probability distribution, such that the probability of large errors is much greater than would be expected from the usual quantization noise model. A novel timebase compensation method is proposed which makes the measured RMS errors normally distributed and reduces their standard deviation by a factor of 25. This compensation method was applied to a sampling voltmeter and the improved accuracy was realized.

A method for calibration of partial discharge calibrators

A method for calibration of partial discharge calibrators has been developed based on passive integration of the induced charge. The voltage over a known capacitor is measured by a calibrated digital sampling voltmeter and the charge is calculated as the voltage multiplied by the capacitance. The best achieved uncertainty is /spl plusmn/2% with a coverage factor k=2.

A simulation tool for the AC-DC transfer difference of thermal converters at low frequencies

To find the reason for the AC-DC transfer differences of the planar multijunction thermal converter (PMJTC) at low frequencies, where temperature oscillation is present due to the lack of integration of the oscillating Joule heat, the coupled electro-thermal mathematical problem has been solved. The dynamic nonlinear model includes the temperature dependence of all material parameters, of heat conduction through the air and radiation losses. The results of the simulation are compared with those of measurements using a sampling voltmeter with special software as a reference. A new design is proposed to improve the performance of the PMJTC at low frequencies.

Precision measurement of AC voltage below 20 Hz at IEN

A new system for ac voltage measurements at low frequencies has been built at the Istituto Elettrotecnico Nazionale (IEN). The system uses a sampling voltmeter working as an integrating analog to digital converter and software programs for data acquisition and processing. An algorithm for the reconstruction of the input voltage based on a model of the converter allows the precise evaluation of the signal parameters. Comparisons at 20 Hz and 40 Hz with measurements made using the thermal converters of the national standard have shown differences lower than a few parts in 10/sup 6/.