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

NBS monograph

From Introduction: "This monograph describes the calibration of standard platinum resistance thermometers at the NBS including the equipment, techniques, and procedures.

Neutron dosimetry with a water calorimeter

In certain situations neutron radiotherapy has potential advantages over conventional X-ray therapy. It has yet to be conclusively proven that neutron therapy is more efficacious than X-ray therapy, and in many institutions worldwide neutron therapy is currently being evaluated. It is important that the dosimetry of neutron beams is consistent so that clinical results from different centres can be compared. Due to the relatively large uncertainties in the measurement of absorbed dose in neutron beams this consistency is difficult to achieve. This work describes the application of a recently developed dosimetry method, namely water calorimetry, to the field of neutron dosimetry. The concept of absorbed dose and its measurement are discussed. The theory behind radiation calorimetry in general, and specifically water calorimetry, is outlined followed by a review of water calorimetry and calorimeters for neutron dosimetry. The calorimeter, which consists simply of a thermally insulated tank of water, and its construction are described. The temperature rise in the water was detected by a thermistor which was incorporated in a Wheatstone bridge circuit. The merits of different configurations of bridge circuit are discussed and the literature on the subject is reviewed. The circuit employed was an AC bridge having asymmetric, inductive ratio arms. The output of the bridge was detected by a lock-in amplifier and the signal was fed directly to a microcomputer which stored and analysed the data.Absorbed dose measurements with the calorimeter were made in 4 and 9 MV photon beams, a 10 MeV electron beam and a d(15) + Be neutron beam. Calorimetric determinations of absorbed dose were compared, under identical conditions, with ionisation chamber dosimetry. In the 4 MV 10 and 9 MV photon beams calorimetric measurements of absorbed dose to water were respectively 4.0 and 4.5% higher than ionisation chamber measurements. In the 10 MeV electron beam calorimetric measurements were 5.5% higher. These differences are due to the heat defect in water which is discussed in detail. In the neutron beam absorbed dose measured with the calorimeter was compared with that measured using an Exradin tissue equivalent ionisation chamber. Doses measured with the ionisation chamber were calculated according to the European protocol for neutron dosimetry. Absorbed dose to tissue measured with the calorimeter was 4.4% lower than that measured with the ionisation chamber. Relative to ionisation chamber dosimetry, dose measurements with the calorimeter were approximately 9% lower in the neutron beam than in the photon beams. The implications of this result, and those from other water calorimeters, are fully discussed

Methods and Results of Power Cycling Tests for Semiconductor Power Devices

This work intends to enhance the state of the research in power cycling tests with statements on achievable measurement accuracy, proposed test bench topologies and recommendations on improved test strategies for various types of semiconductor power devices. Chapters 1 and 2 describe the current state of the power cycling tests in the context of design for reliability comprising applicable standards and lifetime models. Measurement methods in power cycling tests for the essential physical parameters are explained in chapter 3. The dynamic and static measurement accuracy of voltage, current and temperature are discussed. The feasibly achievable measurement delay tmd of the maximal junction temperature Tjmax, its consequences on accuracy and methods to extrapolate to the time point of the turn-off event are explained. A method to characterize the thermal path of devices to the heatsink via measurements of the thermal impedance Zth is explained. Test bench topologies starting from standard setups, single to multi leg DC benches are discussed in chapter 4. Three application-closer setups implemented by the author are explained. For tests on thyristors a test concept with truncated sinusoidal current waveforms and online temperature measurement is introduced. An inverter-like topology with actively switching IGBTs is presented. In contrast to standard setups, there the devices under test prove switching capability until reaching the end-of-life criteria. Finally, a high frequency switching topology with low DC-link voltage and switching losses contributing significantly to the overall power losses is presented providing new degrees of freedom for setting test conditions. The particularities of semiconductor power devices in power cycling tests are thematized in chapter 5. The first part describes standard packages and addressed failure mechanisms in power cycling. For all relevant power electronic devices in silicon and silicon carbide, the devices’ characteristics, methods for power cycling and their consequences for test results are explained. The work is concluded and suggestions for future work are given in chapter 6.:Abstract 1 Kurzfassung 3 Acknowledgements 5 Nomenclature 10 Abbreviations 10 Symbols 12 1 Introduction 19 2 Applicable Standards and Lifetime Models 25 3 Measurement parameters in power cycling tests 53 4 Test Bench Topologies 121 5 Semiconductor Power Devices in Power Cycling 158 6 Conclusion and Outlook 229 References 235 List of Publications 253 Theses 257Diese Arbeit bereichert den Stand der Wissenschaft auf dem Gebiet von Lastwechseltests mit Beiträgen zu verbesserter Messgenauigkeit, vorgeschlagenen Teststandstopologien und verbesserten Teststrategien für verschiedene Arten von leistungselektronischen Bauelementen. Kurzgefasst der Methodik von Lastwechseltests. Das erste Themengebiet in Kapitel 1 und Kapitel 2 beschreibt den aktuellen Stand zu Lastwechseltests im Kontext von Design für Zuverlässigkeit, welcher in anzuwendenden Standards und publizierten Lebensdauermodellen dokumentiert ist. Messmethoden für relevante physikalische Parameter in Lastwechseltests sind in Kapitel 3. erläutert. Zunächst werden dynamische und statische Messgenauigkeit für Spannung, Strom und Temperaturen diskutiert. Die tatsächlich erreichbare Messverzögerung tMD der maximalen Sperrschichttemperatur Tjmax und deren Auswirkung auf die Messgenauigkeit der Lastwechselfestigkeit wird dargelegt. Danach werden Methoden zur Rückextrapolation zum Zeitpunkt des Abschaltvorgangs des Laststroms diskutiert. Schließlich wird die Charakterisierung des Wärmepfads vom Bauelement zur Wärmesenke mittels Messung der thermischen Impedanz Zth behandelt. In Kapitel 4 werden Teststandstopologien beginnend mit standardmäßig genutzten ein- und mehrsträngigen DC-Testständen vorgestellt. Drei vom Autor umgesetzte anwendungsnahe Topologien werden erklärt. Für Tests mit Thyristoren wird ein Testkonzept mit angeschnittenem sinusförmigem Strom und in situ Messung der Sperrschichttemperatur eingeführt. Eine umrichterähnliche Topologie mit aktiv schaltenden IGBTs wird vorgestellt. Zuletzt wird eine Topologie mit hoch frequent schaltenden Prüflingen an niedriger Gleichspannung bei der Schaltverluste signifikant zur Erwärmung der Prüflinge beitragen vorgestellt. Dies ermöglicht neue Freiheitsgrade um Testbedingungen zu wählen. Die Besonderheiten von leistungselektronischen Bauelementen werden in Kapitel 5 thematisiert. Der erste Teil beschreibt Gehäusetypen und adressierte Fehlermechanismen in Lastwechseltests. Für alle untersuchten Bauelementtypen in Silizium und Siliziumkarbid werden Charakteristiken, empfohlene Methoden für Lastwechseltests und Einflüsse auf Testergebnisse erklärt. Die Arbeit wird in Kapitel 6 zusammengefasst und Vorschläge zu künftigen Arbeiten werden unterbreitet.:Abstract 1 Kurzfassung 3 Acknowledgements 5 Nomenclature 10 Abbreviations 10 Symbols 12 1 Introduction 19 2 Applicable Standards and Lifetime Models 25 3 Measurement parameters in power cycling tests 53 4 Test Bench Topologies 121 5 Semiconductor Power Devices in Power Cycling 158 6 Conclusion and Outlook 229 References 235 List of Publications 253 Theses 25

Traceability of electrolytic conductivity measurements for ultra pure water

In quality control, one of the most commonly used parameters for the determination of the overall ionic purity of water is the electrolytic conductivity. The goal of the Istituto Nazionale di Ricerca Metrologica (INRiM) is to produce electrolytic conductivity values traceable to the International System of Units (SI) especially in the field of ultra- pure water, as required by many industrial sectors. About pure water, the most significant difficulties regard the pollution of the solution with the air CO2, the temperature monitoring and the resistance measurement that should not be affected by parasitic phenomena. European, Japanese and American Pharmacopoeia demand that the purity of the water is defined by electrolytic conductivity measurements with uncertainty of 1%. ASTM Designation prescribe the use of a flow system for solutions with a conductivity of less than 50 µScm-1. In order to carry out measurements of solutions with low electrolytic conductivity, at INRiM a new primary cell with extra devices has been developed and built. The measurement capability of the new primary cell has been verified taking part in the international Key Comparison CCQM-K92 "Electrolytic Conductivity at 0.05 S/m". Moreover, a Pyrex glass closed circuit consisted also by a secondary cell and an expansion chamber has been realised. Measurements were carried out using solutions at different electrolytic conductivity values: the repeatability of measurements has been improved, the drift over time using the flowing system decreases and the expanded uncertainty value has been reduced. From preliminary measurement, it was observed that the frequency value corresponding to the electrolytic conductivity value of ultra pure water is less than 1 Hz. Since the LCR commercial bridges do not reach frequencies below 20 Hz, an impedance spectrometer which allows the measurement of impedance spectra in the frequency range from mHz to kHz has been developed. Working in the direction of lower conductivity values, measurements on solutions containing water, KCl and ethanol have been carried out. This research activity is conducted under the patronage of the European project EMRP - ENG09 Metrology for biofuels, by means of participation in the international comparison EURAMET Study 1202 "Study on electrolytic conductivity reveals measurements of bioethanol". Closed circuit is also used to perform calibration of the secondary cell for comparison on the primary cell. The traditional method of calibration by substitution is affected by errors in the definition of the conductivity value due to the drift in temperature and concentration of the sample transfer, as it is measured in two separate cells. Using solutions with low electrolytic conductivity (eg < 50 μScm-1 ), the errors generated by this method are too large. To reduce the uncertainty the reference cell and the cell under calibration are inserted in the closed circuit and the measurement is performed using the same solution (that flows within the circuit). In this way it is possible to avoid problems related to the difference of the solution drift and the temperature. By means of this calibration method by comparison it is possible to improve the value of the expanded uncertainty of the measurements of an order of magnitude . Several activities related to the measurement of solutions with high conductivity values have been carried out: these research activities took place in the European project EMRP - ENV05 "Equivalence ratio of conductance measurement result of seawater". They were related to the international pilot comparison CCQM-P142 on aqueous solutions with a high content of KCl and marine waters (different dilutions) and to the international key comparison CCQM-K105 on measures of KCl solutions with a nominal value of electrolytic conductivity of 5.3 S/m, for which INRiM had the role of coordinating laborator

Metrology of fluid mechanics

CER66VAS32.June 1966

Introduction to modern instrumentation: for hydraulics and environmental sciences

Preface Natural hazards and anthropic activities threaten the quality of the environment surrounding the human being, risking life and health. Among the different actions that must be taken to control the quality of the environment, the gathering of field data is a basic one. In order to obtain the needed data for environmental research, a great variety of new instruments based on electronics is used by professionals and researchers. Sometimes, the potentials and limitations of this new instrumentation remain somewhat unknown to the possible users. In order to better utilize modern instruments it is very important to understand how they work, avoiding misinterpretation of results. All instrument operators must gain proper insight into the working principles of their tools, because this internal view permits them to judge whether the instrument is appropriately selected and adequately functioning. Frequently, manufacturers have a tendency to show the great performances of their products without advising their customers that some characteristics are mutually exclusive. Car manufacturers usually show the maximum velocity that a model can reach and also the minimum fuel consumption. It is obvious for the buyer that both performances are mutually exclusive, but it is not so clear for buyers of measuring instruments. This book attempts to make clear some performances that are not easy to understand to those uninitiated in the utilization of electronic instruments. Technological changes that have occurred in the last few decades are not yet reflected in academic literature and courses; this material is the result of a course prepared with the purpose of reducing this shortage. The content of this book is intended for students of hydrology, hydraulics, oceanography, meteorology and environmental sciences. Most of the new instruments presented in the book are based on electronics, special physics principles and signal processing; therefore, basic concepts on these subjects are introduced in the first chapters (Chapters 1 to 3) with the hope that they serve as a complete, yet easy-to-digest beginning. Because of this review of concepts it is not necessary that the reader have previous information on electronics, electricity or particular physical principles to understand the topics developed later. Those readers with a solid understanding of these subjects could skip these chapters; however they are included because some students could find them as a useful synthesis. Chapter 4 is completely dedicated to the description of transducers and sensors frequently used in environmental sciences. It is described how electrical devices are modified by external parameters in order to become sensors. Also an introduction to oscillators is presented because they are used in most instruments. In the next chapters all the information presented here is recurrently referred to as needed to explain operating principles of instruments. Unauthenticated Download Date | 10/12/14 9:29 PM VIII Preface Chapters 1 to 4 are bitter pills that could discourage readers interested in the description of specific instruments. Perhaps, those readers trying this book from the beginning could abandon it before arriving at the most interesting chapters. Therefore, they could read directly Chapters 5 to 11, going back as they feel that they need the knowledge of the previous chapters. We intended to make clear all the references to the previous subjects needed to understand each one of the issues developed in the later chapters. Chapter 5 contributes to the understanding of modern instrumentation to measure flow in industrial and field conditions. Traditional mechanical meters are avoided to focus the attention on electronic ones, such as vortex, electromagnetic, acoustic, thermal, and Coriolis flowmeters. Special attention is dedicated to acoustic Doppler current profilers and acoustic Doppler velocimeters. Chapter 6 deals with two great subjects; the first is devoted to instruments for measuring dynamic and quasi static levels in liquids, mainly water. Methods to measure waves at sea and in the laboratory are explained, as well as instruments to measure slow changes such as tides or piezometric heads for hydrologic applications. The second subject includes groundwater measurement methods with emphasis on very low velocity flowmeters which measure velocity from inside a single borehole. Most of them are relatively new methods and some are based on operating principles described in the previous chapter. Seepage meters used to measure submarine groundwater discharge are also presented. Chapter 7 presents methods and instruments for measuring rain, wind and solar radiation. Even though the attention is centered on new methods, some traditional methods are described not only because they are still in use, and it is not yet clear if the new technologies will definitely replace them, but also because describing them permits their limitations and drawbacks to be better understood. Methods to measure solar radiation are described from radiation detectors to complete instruments for total radiation and radiation spectrum measurements. Chapter 8 is a long chapter where we have tried to include most remote measuring systems useful for environmental studies. It begins with a technique called DTS (Distributed Temperature Sensing) that has the particularity of being remote, but where the electromagnetic wave propagates inside a fibre optic. The chapter follows with atmosphere wind profilers using acoustic and electromagnetic waves. Radio acoustic sounding systems used to get atmospheric temperature profiles are explained in detail as well as weather radar. Methods for ocean surface currents monitoring are also introduced. The chapter ends with ground penetrating radars. Chapter 9 is an introduction to digital transmission and storage of information. This subject has been reduced to applications where information collected by field instruments has to be conveyed to a central station where it is processed and stored. Some insight into networks of instruments is developed; we think this information will help readers to select which method to use to transport information from field to office, by means of such diverse communication media as fibre optic, digital telephony, Unauthenticated Download Date | 10/12/14 9:29 PM Preface IX GSM (Global System for Mobile communications), satellite communications and private radio frequency links. Chapter 10 is devoted to satellite-based remote sensing. Introductory concepts such as image resolution and instrument?s scanning geometry are developed before describing how passive instruments estimate some meteorological parameters. Active instruments are presented in general, but the on-board data processing is emphasized due to its importance in the quality of the measurements. Hence, concepts like Synthetic Aperture Radar (SAR) and Chirp Radar are developed in detail. Scatterometers, altimeters and Lidar are described as applications of the on-board instruments to environmental sciences. Chapter 11 attempts to transfer some experiences in field measuring to the readers. A pair of case studies is included to encourage students to perform tests on the instruments before using them. In this chapter we try to condense our ideas, most of them already expressed throughout the book, about the attitude a researcher should have with modern instruments before and after a measuring field work. As can be inferred from the foregoing description the book aims to provide students with the necessary tools to adequately select and use instruments for environmental monitoring. Several examples are introduced to advise future professionals and researchers on how to measure properly, so as to make sure that the data recorded by the instruments actually represents the parameters they intend to know. With this purpose, instruments are explained in detail so that their measuring limitations are recognized. Within the entire work it is underlined how spatial and temporal scales, inherent to the instruments, condition the collection of data. Informal language and qualitative explanations are used, but enough mathematical fundamentals are given to allow the reader to reach a good quantitative knowledge. It is clear from the title of the book that it is a basic tool to introduce students to modern instrumentation; it is not intended for formed researchers with specific interests. However, general ideas on some measuring methods and on data acquisition concepts could be useful to them before buying an instrument or selecting a measuring method. Those readers interested in applying some particular method or instrument described in this book should consider these explanations just as an introduction to the subject; they will need to dig deeper in the specific bibliography before putting hands on.Fil: Guaraglia, Dardo Oscar. Universidad Nacional de la Plata. Facultad de Ingeniería. Departamento de Hidraulica. Area Hidraulica Basica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Pousa, Jorge Lorenzo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Oceanografía Costera y Estuarios; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

Materials Research in Microgravity 2012

Reducing gravitational effects such as thermal and solutal buoyancy enables investigation of a large range of different phenomena in materials science. The Symposium on Materials Research in Microgravity involved 6 sessions composed of 39 presentations and 14 posters with contributions from more than 14 countries. The sessions concentrated on four different categories of topics related to ongoing reduced-gravity research. Highlights from this symposium will be featured in the September 2012 issue of JOM. The TMS Materials Processing and Manufacturing Division, Process Technology and Modeling Committee and Solidification Committee sponsored the symposium