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Recent advancements and perspectives of INRiM’s time-dependent Josephson voltage standards
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Quantum sampling AC standard for electrical power metrology based on programmable Josephson junction series array
Full text linkThe INRIM Role of Inter-laboratory Comparison Provider for Electrical Power and Energy at Industrial Frequency: A Two-Year Activity Report
Full text linkThe technical surveillance of secondary calibration laboratories accredited according to the ISO/IEC 17025 standard for electrical power and energy at industrial frequency is very important, as these measurements are the basis of the commercial relations between an electricity supplier and a user. An effective technical surveillance requires the execution of inter-laboratory comparisons (ILCs). With them, it is possible to verify the competence of the laboratories and the correctness of the dissemination process from the national standards of power and energy, usually maintained at national metrology institutes (NMI), to these laboratories. The paper deals with the ILCs that the National Institute of Metrological Research (INRIM) provided and carried out as reference measurements provider for Italian accredited laboratories for power and energy (active and reactive) at industrial frequency. The ILCs were carried out involving various instrument types and at different uncertainty levels. The 2 relative uncertainties of the INRIM calibrations ranged from 1.0104 to 1.5103. The ILCs had satisfactory results confirming the correctness of both the dissemination from INRIM and the accreditation process by the Italian accreditation body for calibration laboratories
Thermal Performances of an Improved Package for Cryocooled Josephson Standards
Full text linkComplex cryogenics still represents a strong limitation to the spread of Josephson voltage standards, and cryogenfree cooling is particularly suitable to simplify their operation. The main downsides of liquid-helium-free systems are related to the chip thermalization: Indeed, at low temperature, the heat transfer between the chip and the coldplate of a cryocooler in vacuum is strongly affected by the quality of the interfaces. In order to increase the thermal performances of cryocooled programmable Josephson standards, we devised and tested a special cryopackage: The chip is embedded into a sandwich structure with high-thermal-conductivity materials subject to a controlled mechanical pressure to reduce the thermal contact resistances. A thin sapphire lamina placed upon the chip allows the heat to be dissipated from the top, thus creating an additional path for the thermal flow. A special bridgelike system with a screw is used as a reproducible torque-to-force converter to exert known pressures to the sandwich. Furthermore, we analyzed the effect of thermal contraction to the actual pressure exerted on the chip, showing a nonnegligible increase when cooled down to cryogenic temperature that can be calculated and corrected for
New IEC standards for the measurement of sheet resistance on large-area graphene using the van der Pauw and the in-line four-point probe methods
Full text linkGraphene has evolved from a scientific research subject to an industrial product, in need of a normative basis for its key control characteristics. Recently two new IEC technical specifications that establish standardized procedures for assessing the sheet resistance R S of monolayer graphene have been published. These new standards, part of the IEC TS 62607-6-xx series, outline protocols for employing two contact methods: i) van der Pauw, and ii) in -line four -point probe. In the following we present and discuss illustrative examples of the scientific experiments designed and performed to inform the standardization process behind the presented standards. In particular we report about the investigation of mechanical contacting of chemical -vapor -deposited monolayer graphene and the measurement of the R S in cm 2 area graphene samples with non uniform resistivity distributions. This paper includes an overview of the broader IEC context, detailing the key steps in the development of the standards themselves
1 kV Wideband Voltage Transducer, a Novel Method for Calibration and a Voltage Measurement Chain
Full text linkA new reference resistive-capacitive voltage divider is presented in this paper, operating in DC and AC from 10 kHz up to 200 kHz. The ratio error is lower than 0.1% and the phase error is lower than 400 urad (1.375’) at 100 kHz. The divider is stable and repeatable. The scale factor and the phase error repeatability, tested in 24 hours continuous measurements repeated during 15 weeks, show a scale factor variation lower than 80 ppm and a phase error variation lower than 20 urad. This allows one to define a calibration matrix of the device bringing its relative measurement uncertainty lower than 0.5∙10^-3 . The divider calibration has been obtained with a step-up method, which could improve traceability in many laboratories, and is described in the paper. The divider can be embedded in a calibration chain to test the accuracy of voltage transducers in the measurement of the AC voltage ripple, in the presence of a significant DC component, as it occurs in many power electronic systems. The voltage calibration chain is based on the use of the reference divider and a voltage injector, the secondary of which is placed in series with a stable DC source. By means of this calibration system, one of the best commercial voltage transducers on the market has been analyzed. The work also highlights how the proposed voltage calibration chain could be used in perspective in a phantom power system for the development of a DC plus AC power standard
DISPOSITIVO DI TERMALIZZAZIONE.
No full textÈ descritto un dispositivo di termalizzazione atto al raffreddamento uniforme di almeno un campione dotato di una struttura a strati, tale struttura a strati è composta da almeno una lamina termoconduttiva elettroisolante, almeno una struttura elastica termoconduttiva, almeno un substrato su cui è depositato il campione e almeno un mezzo di supporto
DISPOSITIVO DI TERMALIZZAZIONE
No full textÈ descritto un dispositivo di termalizzazione atto al raffreddamento uniforme di almeno un campione dotato di una struttura a strati, tale struttura a strati è composta da almeno una lamina termoconduttiva elettroisolante, almeno una struttura elastica termoconduttiva, almeno un substrato su cui è depositato il campione e almeno un mezzo di supporto
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