Wideband digital phase comparator for high current shunts

A wideband phase comparator for precise measurements of phase difference of high current shunts has been developed at INRIM. The two-input digital phase detector is realized with a precision wideband digitizer connected through a pair of symmetric active guarded transformers to the outputs of the shunts under comparison. Data are first acquired asynchronously, and then transferred from on-board memory to host memory. Because of the large amount of data collected the filtering process and the analysis algorithms are performed outside the acquisition routine. Most of the systematic errors can be compensated by a proper inversion procedure. The system is suitable for comparing shunts in a wide range of currents, from several hundred of milliampere up to 100 A, and frequencies ranging between 500 Hz and 100 kHz. Expanded uncertainty (k=2) less than 0.05 mrad, for frequency up to 100 kHz, is obtained in the measurement of the phase difference of a group of 10 A shunts, provided by some European NMIs, using a digitizer with sampling frequency up to 1 MHz. An enhanced version of the phase comparator employs a new digital phase detector with higher sampling frequency and vertical resolution. This permits to decrease the contribution to the uncertainty budget of the phase detector of a factor two from 20 kHz to 100 kHz. Theories and experiments show that the phase difference between two high precision wideband digitizers, coupled as phase detector, depends on multiple factors derived from both analog and digital imprint of each sampling system.Comment: 20 pages, 9 figure

Development of a PJVS System for Quantum-Based Sampled Power Measurements

The paper deals with recent progresses at INRiM towards the development and characterization of a programmable Josephson voltage standard (PJVS) operating in a small liquid helium dewar as well as with its integration for the realization of a practical quantum sampling electrical power standard. The PJVS is based on a 1V superconductor-normal metal-superconductor (SNS) binary-divided array of 8192 Josephson junctions. To ensure proper operating conditions of the PJVS chip, a custom short cryoprobe was designed, built and successfully tested. The overall system is being developed in the framework of EMPIR project 19RPT01-QuantumPower. The goal is to establish a new quantum power standard (QPS) based on a single Josephson voltage standard for sampled power measurements and to gain confidence in running PJVS for precise calibration of digital sampling multimeters and arbitrary waveform digitizers used in the ac-voltage and power metrology community

Comparison of a Thermal AC Voltage Standard in the 1–30-MHz Frequency Range

This article presents results of a comparison of a traveling ac voltage standard, which was a fused-silica planar multijunction thin-film thermal converter (PMJTC) developed at the National Institute of Standards and Technology (NIST). The ac-dc voltage-transfer difference of the standard was measured at 2 V and selected frequencies from 1-30 MHz against primary thermal ac voltage standards at the Silesian University of Technology, Istituto Nazionale di Ricerca Metrologica, RISE Research Institutes of Sweden, and Trescal A/S Silkeborg

A calibration-verification testbed for electrical energy meters under low power quality conditions

open7A calibration/verification testbed for electrical energy meters is under development at the Istituto Nazionale di Ricerca Metrologica, the National Metrology Institute of Italy. The testbed will be employed for the calibration of commercial static power energy meters under low power conditions and for simulating the verification in the field of energy meters under real operational conditions. The activity is in collaboration with the Ministry for Economic Development and aims to the future development of regulatory documents for energy metering verification.openCallegaro, Luca; Aprile, Giulia; Cultrera, Alessandro; Galliana, Flavio; Germito, Gabriele; Serazio, Danilo; Trinchera, BrunoCallegaro, Luca; Aprile, Giulia; Cultrera, Alessandro; Galliana, Flavio; Germito, Gabriele; Serazio, Danilo; Trinchera, Brun

Tests of SNIS Josephson Arrays Cryocooler Operation

Cryogen-free operation of is essential to spread applications of superconductivity and is indeed unavoidable in some cases. In electrical metrology applications, higher temperature operation to reduce the refrigerator size and complexity is not yet possible, since arrays of Josephson junctions for voltage standard applications made with high-temperature superconductors are not yet available. The superconductor-normal metal-insulator-superconductor (SNIS) technology developed at INRIM uses low temperature superconductors, but allows operation well above liquid helium temperature. It is thus interesting for application to a compact cryocooled standard. We studied SNIS devices cooled with a closed-cycle refrigerator, both in DC and under RF irradiation. Issues related to thermal design of the apparatus are analyzed. The dependence of RF steps on the number of junctions observed is discussed in detail and interpreted as a consequence of power dissipated inside the chip

Laboratory reproduction of on-field low power quality conditions for the calibration/verification of electrical energy meters

– In this work we present a method for testing static active energy meters in low power quality conditions recorded at installation sites. Voltage and current waveforms recorded on the field with a calibrated portable instrument were reproduced with an accurate phantom power generator up to the 40th harmonic. The error on the active energy measurement of an energy meter under test (WDUT) in conditions reproduced from the on-field measurements was evaluated in comparison with a reference meter (WREF). On-field data were recorded at a 50 kW self production photovoltaic facility. This method allows the laboratory reproduction of realistic (distorted) on-field conditions in a metrologically traceable framewor

Realization of the farad from the dc quantum Hall effect with digitally-assisted impedance bridges

A new traceability chain for the derivation of the farad from dc quantum Hall effect has been implemented at INRIM. Main components of the chain are two new coaxial transformer bridges: a resistance ratio bridge, and a quadrature bridge, both operating at 1541 Hz. The bridges are energized and controlled with a polyphase direct-digital-synthesizer, which permits to achieve both main and auxiliary equilibria in an automated way; the bridges and do not include any variable inductive divider or variable impedance box. The relative uncertainty in the realization of the farad, at the level of 1000 pF, is estimated to be 64E-9. A first verification of the realization is given by a comparison with the maintained national capacitance standard, where an agreement between measurements within their relative combined uncertainty of 420E-9 is obtained.Comment: 15 pages, 11 figures, 3 table