Automatic DC voltage precision resistive divider with ratios between 10:1 and 107:1

At INRIM a DC Voltage precision resistive divider performing decade ratios from 10:1 to 107:1 was built. It can be automatically calibrated with a top-class calibrator and a precision multimeter calibrated in terms of deviation from linearity. It is made up of 90 kΩ, 9 kΩ, 900 Ω, 90 Ω, 9 Ω, 0.9 Ω, 90 mΩ and 10 mΩ bulk metal foil resistors connected in series, in four-terminal configuration. Peculiarities of the calibration method of the divider are: the evaluation of the DMM input impedance to correct its readings minimizing the load error and a solution to reduce the emfs effect of the relays. These operations are made during the calibration of the divider. The calibration and use uncertainties of the divider span respectively from 6.1 × 10 7 to 5.9 × 10 4 and from 6.7 × 10 7 to 6.5 × 10 4. The project is transferable to secondary laboratories in the framework of the INRIM knowledge transfer task

キャパシタンス標準に関する計測技術の研究

東京都市大学2013年度(平成25年

A Capacitance Build-Up Method to Determine LCR Meter Errors and Capacitance Transfer

partially_open4We present a capacitance build-up method suitable for the determination of the measurement error of a capacitance meter. The method requires only a small number of uncalibrated base capacitors, to be connected in parallel in various combinations, and a single calibrated capacitor, which provides measurement traceability. The outcome of the method is both the determination of the meter error and the calibration of all the base capacitors; it can therefore be also considered a capacitance scaling method. The method's equations, cast in matrix form, express estimates and uncertainties for all the quantities of interest. As an example of application, a commercial LCR meter is calibrated in the ranges of (100-1000) pF and (1-10) nF at 1.6 and 10 kHz, with an accuracy at the level of a few parts in 10(6). The calibration is validated by comparison with an ultrahigh accuracy capacitance bridge.mixedTran, NTM; D'Elia, V; Callegaro, L; Ortolano, MTran, Ntm; D'Elia, V; Callegaro, L; Ortolano,

A Capacitance Build-Up Method to Determine LCR Meter Errors and Capacitance Transfer

We present a capacitance build-up method suitable for the determination of the measurement error of a capacitance meter. The method requires only a small number of uncalibrated base capacitors, to be connected in parallel in various combinations, and a single calibrated capacitor, which provides measurement traceability. The outcome of the method is both the determination of the meter error and the calibration of all the base capacitors; it can therefore be also considered a capacitance scaling method. The method's equations, cast in matrix form, express estimates and uncertainties for all the quantities of interest. As an example of application, a commercial LCR meter is calibrated in the ranges of (100-1000) pF and (1-10) nF at 1.6 and 10 kHz, with an accuracy at the level of a few parts in 10(6). The calibration is validated by comparison with an ultrahigh accuracy capacitance bridge

The ampere and the electrical units in the quantum era

By fixing two fundamental constants from quantum mechanics, the Planck constant $h$ and the elementary charge $e$, the revised Syst\`eme International (SI) of units endorses explicitly quantum mechanics. This evolution also highlights the importance of this theory which underpins the most accurate realization of the units. From 20 May 2019, the new definitions of the kilogram and of the ampere, based on fixed values of $h$ and $e$ respectively, will particularly impact the electrical metrology. The Josephson effect (JE) and the quantum Hall effect (QHE), used to maintain voltage and resistance standards with unprecedented reproducibility since 1990, will henceforth provide realizations of the volt and the ohm without the uncertainties inherited from the older electromechanical definitions. More broadly, the revised SI will sustain the exploitation of quantum effects to realize electrical units, to the benefit of end-users. Here, we review the state-of-the-art of these standards and discuss further applications and perspectives.Comment: 78 pages, 35 figure

A Comprehensive Analysis of Error Sources in Electronic Fully Digital Impedance Bridges

open12sìFully digital impedance bridges are emerging as measuring instruments for primary electrical impedance metrology and the realization of impedance units and scales. This article presents a comprehensive analysis of electronic fully digital impedance bridges for both generating (based on digital-to-analog converters) and digitizing (based on analog-to-digital converters) bridges. The sources of measurement error are analyzed in detail and expressed by explicit mathematical formulas ready to be applied to the specific bridge and measurement case of interest. The same can be employed also as a basis to optimize the design and the operating parameters of digital bridges and evaluate the measurement uncertainty. A practical application of the analysis to the digital bridges developed and measurements performed in the framework of an international research project is presented.openOrtolano, Massimo; Marzano, Martina; D'Elia, Vincenzo; Mai Tran, Ngoc Thanh; Rybski, Ryszard; Kaczmarek, Janusz; Koziol, Miroslaw; Musiol, Krzysztof; Christensen, Andreas Elmholdt; Callegaro, Luca; Kucera, Jan; Power, OliverOrtolano, Massimo; Marzano, Martina; D'Elia, Vincenzo; Mai Tran, Ngoc Thanh; Rybski, Ryszard; Kaczmarek, Janusz; Koziol, Miroslaw; Musiol, Krzysztof; Christensen, Andreas Elmholdt; Callegaro, Luca; Kucera, Jan; Power, Olive

An uncertainty budget for the precursor Watt balance for South Africa

The 26th General Conference on Weights and Measures (CGPM) held on the 16th November 2018 has adopted the revision of the International system of units (SI) to be based on the fundamental physical constants

A cryogenic Strontium lattice clock

Optical clocks have moved to the forefront of frequency metrology. Their outstanding performances enable the exploration of new fields of research such as the search for dark matter and dark energy [1, 2], temporal drifts of the fine structure constant alpha [3, 5], violations of the Einstein equivalence principle (EEP) [6], and new applications such as chronometric leveling [7]. State-of-the-art optical clocks outperform the current realization of the SI-unit "Second" by the 133cesium fountain clocks, by two orders magnitude or more in instability and accuracy which triggers a discussion on a re-definition of the second. In 2016 the Consultative Committee for Time and Frequency (CCTF) of the International Bureau of Weights and Measures (BIPM) released a roadmap towards a redefinition of the SI second. One of the requests is the characterization of the systematic uncertainty of at least three independent clocks at the level of 10^-18. In this work, PTB's new cryogenic strontium lattice clock, Sr3, operating on the 1S0 - 3P0 clock transition in neutral 87Sr is described. Its systematic uncertainty has is evaluated to 2.7 x 10^-18 in fractional frequency units. This represents an improvement of more than a factor of 5 compared to its predecessor system Sr1 [8]. In Sr1 the dominant contribution of frequency uncertainty was about 1.4 x 10^-17 from the uncertainty of the black-body radiation (BBR) frequency shift. It arose from temperature gradients across the in-vacuum magnetic field coils that are placed close to the atoms. Reducing the gradients was not possible which ultimately limited the systems achievable systematic uncertainty. Sr3 features an in-vacuum dual-layer environment, the cryostat, that provides a very homogeneous temperature distribution for the atoms. This translates to a lower BBR frequency shift uncertainty as Sr1 at room temperature operation. The corresponding total systematic uncertainty for room temperature operation was evaluated to about 3.5 x 10^-18. Furthermore Sr3 features a closed-cycle pulse tube cooler that allows to operate the cryostat at any temperature ranging from room temperature to about 80K to further reduce the BBR frequency shift and uncertainty where the systematic uncertainty reaches the value of 2.7 x 10^-18 as mentioned above. Sr3 also features an arrangement of electrodes that allow the characterization of the dc-Stark frequency shift in three dimensional space. In this work the characterization of the electrode arrangement is described and the determination of the dc Stark shift. In Sr1 the this capability was limited to one direction that was pointing along the quantization magnetic field axis. During clock operation of Sr1, several high-accuracy comparisons to other atomic clocks have been performed. This includes many absolute frequency measurements yielding in a new record uncertainty in the transition frequency. An absolute frequency of Sr1 of f(Sr1) = 429 228 004 229 873.00(7)Hz [8] was measured that is in agreement withe the one measured of Sr3 of f(Sr3) = 429 228 004 229 872:94(19)Hz. The statistical uncertainty the measurements was significantly improved by using a H-Maser as a flywheel oscillator toeither extend the dataset or to bridge downtimes of the Sr-clocks [9]. Optical frequency ratio measurements between either of the two strontium clocks and the on-campus 171Yb+ single-ion clock have been carried out [10] for direct determination of their frequency ratio beyond the limitation of the primary frequency standards represented by Cs fountain clocks. The ratio measurements involving Sr1 span over a period of more than seven years and more than half a year with Sr3. The measurements have also revealed that the frequency ratio of the clocks, are reproducible within their uncertainties on short time scales but exhibits unexpected large scatter in the long term. The observed variations are on the order of several 10^-17 which is beyond any of the clocks reported systematic uncertainty. Despite an excessive search no uncontrolled frequency shifts were found. In the near future the in-vacuum cryostat is supposed to be updated with rotatable shutters. They will allow to minimize the BBR shift uncertainty during cryogenic operation. Prospectively a BBR shift uncertainty at the low 10^-19 level can be expected which paves the way for the system to reach a total systematic uncertainty of below 1 x 10^-18