Towards a New Realization of the SI-Base Unit “Candela“
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A Learner's Guide to SI Units and Their Conversion
A Learner's Guide to SI Units and their Conversion October 2004 Workbook for students Learner's Guide to SI Units and their Conversion their and Units SI to Guide Learner's Edexcel A London Qualifications is one of the leading examining and awarding bodies in the UK and throughout the world. It incorporates all the qualifications previously awarded under the Edexcel and BTEC brand. We provide a wide range of qualifications including general (academic), vocational, occupational and specific programmes for employers. Through a network of UK and overseas offices, our centres receive the support they need to help them deliver their education and training programmes to learners. For further information please call Customer Services on 0870 240 9800, or visit our website at www.edexcel.org.uk Authorised by Jim Dobson Prepared by Sarah Harrison All the material in this publication is copyright © London Qualifications Limited 2004 CONTENTS Introduction 1 What are units? 2 Operations with units 5 Submultiple and multiple units 9 Conversion of units 11 Conversion examples and exercises 13 Length 13 Area 14 Volume 15 Mass 16 Time 17 Temperature 18 Density 19 Force 20 Stress and pressure 21 Answers to exercises 23 Introduction One of the important areas where Science and Technology students need support is in the conversion of units. This booklet is designed to be useful for students in all Science, Technology and Engineering subjects. This booklet has been produced to: S introduce students to SI base and derived units and S help students with the conversion of multiple and sub-multiple units to SI base and derived units. -
2.1 Definition of the SI
CCPR/16-53 Modifications to the Draft of the ninth SI Brochure dated 16 September 2016 recommended by the CCPR to the CCU via the CCPR president Takashi Usuda, Wednesday 14 December 2016. The text in black is a selection of paragraphs from the brochure with the section title for indication. The sentences to be modified appear in red. 2.1 Definition of the SI Like for any value of a quantity, the value of a fundamental constant can be expressed as the product of a number and a unit as Q = {Q} [Q]. The definitions below specify the exact numerical value of each constant when its value is expressed in the corresponding SI unit. By fixing the exact numerical value the unit becomes defined, since the product of the numerical value {Q} and the unit [Q] has to equal the value Q of the constant, which is postulated to be invariant. The seven constants are chosen in such a way that any unit of the SI can be written either through a defining constant itself or through products or ratios of defining constants. The International System of Units, the SI, is the system of units in which the unperturbed ground state hyperfine splitting frequency of the caesium 133 atom Cs is 9 192 631 770 Hz, the speed of light in vacuum c is 299 792 458 m/s, the Planck constant h is 6.626 070 040 ×1034 J s, the elementary charge e is 1.602 176 620 8 ×1019 C, the Boltzmann constant k is 1.380 648 52 ×1023 J/K, 23 -1 the Avogadro constant NA is 6.022 140 857 ×10 mol , 12 the luminous efficacy of monochromatic radiation of frequency 540 ×10 hertz Kcd is 683 lm/W. -
Guide for the Use of the International System of Units (SI)
Guide for the Use of the International System of Units (SI) m kg s cd SI mol K A NIST Special Publication 811 2008 Edition Ambler Thompson and Barry N. Taylor NIST Special Publication 811 2008 Edition Guide for the Use of the International System of Units (SI) Ambler Thompson Technology Services and Barry N. Taylor Physics Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899 (Supersedes NIST Special Publication 811, 1995 Edition, April 1995) March 2008 U.S. Department of Commerce Carlos M. Gutierrez, Secretary National Institute of Standards and Technology James M. Turner, Acting Director National Institute of Standards and Technology Special Publication 811, 2008 Edition (Supersedes NIST Special Publication 811, April 1995 Edition) Natl. Inst. Stand. Technol. Spec. Publ. 811, 2008 Ed., 85 pages (March 2008; 2nd printing November 2008) CODEN: NSPUE3 Note on 2nd printing: This 2nd printing dated November 2008 of NIST SP811 corrects a number of minor typographical errors present in the 1st printing dated March 2008. Guide for the Use of the International System of Units (SI) Preface The International System of Units, universally abbreviated SI (from the French Le Système International d’Unités), is the modern metric system of measurement. Long the dominant measurement system used in science, the SI is becoming the dominant measurement system used in international commerce. The Omnibus Trade and Competitiveness Act of August 1988 [Public Law (PL) 100-418] changed the name of the National Bureau of Standards (NBS) to the National Institute of Standards and Technology (NIST) and gave to NIST the added task of helping U.S. -
2019 Redefinition of SI Base Units
2019 redefinition of SI base units A redefinition of SI base units is scheduled to come into force on 20 May 2019.[1][2] The kilogram, ampere, kelvin, and mole will then be defined by setting exact numerical values for the Planck constant (h), the elementary electric charge (e), the Boltzmann constant (k), and the Avogadro constant (NA), respectively. The metre and candela are already defined by physical constants, subject to correction to their present definitions. The new definitions aim to improve the SI without changing the size of any units, thus ensuring continuity with existing measurements.[3][4] In November 2018, the 26th General Conference on Weights and Measures (CGPM) unanimously approved these changes,[5][6] which the International Committee for Weights and Measures (CIPM) had proposed earlier that year.[7]:23 The previous major change of the metric system was in 1960 when the International System of Units (SI) was formally published. The SI is a coherent system structured around seven base units whose definitions are unconstrained by that of any other unit and another twenty-two named units derived from these base units. The metre was redefined in terms of the wavelength of a spectral line of a The SI system after the 2019 redefinition: krypton-86 radiation,[Note 1] making it derivable from universal natural Dependence of base unit definitions onphysical constants with fixed numerical values and on other phenomena, but the kilogram remained defined in terms of a physical prototype, base units. leaving it the only artefact upon which the SI unit definitions depend. The metric system was originally conceived as a system of measurement that was derivable from unchanging phenomena,[8] but practical limitations necessitated the use of artefacts (the prototype metre and prototype kilogram) when the metric system was first introduced in France in 1799. -
Indoor Selectable- Output Horns, Strobes, and Horn Strobes for Wall Applications
Indoor Selectable- Output Horns, Strobes, and Horn Strobes for Wall Applications SpectrAlert® Advance audible visible notification products are rich with features guaranteed to cut installation times and maximize profits. Features The SpectrAlert Advance series offers the most versatile and easy-to-use line of horns, strobes, and horn strobes in the industry. • Plug-in design with minimal intrusion into the back box With white and red plastic housings, wall and ceiling mounting • Tamper-resistant construction options, and plain and FIRE-printed devices, SpectrAlert Advance • Automatic selection of 12- or 24-volt operation at can meet virtually any application requirement. 15 and 15/75 candela Like the entire SpectrAlert Advance product line, wall-mount horns, • Field-selectable candela settings on wall units: 15, 15/75, strobes, and horn strobes include a variety of features that increase 30, 75, 95, 110, 115, 135, 150, 177, and 185 their application versatility while simplifying installation. All devices • Horn rated at 88+ dBA at 16 volts feature plug-in designs with minimal intrusion into the back box, • Rotary switch for horn tone and three volume selections making installations fast and foolproof while virtually eliminating costly and time-consuming ground faults. • Universal mounting plate for wall units • Mounting plate shorting spring checks wiring continuity before To further simplify installation and protect devices from construction device installation damage, SpectrAlert Advance utilizes a universal mounting plate • Electrically Compatible with legacy SpectrAlert devices with an onboard shorting spring, so installers can test wiring continuity before the device is installed. • Compatible with MDL3 sync module • Listed for ceiling or wall mounting Installers can also easily adapt devices to a suit a wide range of application requirements using field-selectable candela settings, automatic selection of 12- or 24-volt operation, and a rotary switch for horn tones with three volume selections. -
Worksheet 2 the Metric System and SI Units
Unit Conversions Worksheet 2 The Metric System and SI Units 1 © MathTutorDVD.com Here is a helpful list of all the prefixes and their exponents and abbreviations: 109 giga G one billion 106 mega M one million 103 kilo k one thousand 102 hecto h one hundred 101 deca da ten 10-1 deci d one tenth 10-2 centi c one hundredth 10-3 milli m one thousandth 10-6 micro µ one millionth 10-9 nano n one billionth 10-12 pico p one trillionth 2 © MathTutorDVD.com 1. Give the abbreviation for each of the SI base units below. a. kilogram b. Kelvin c. meter d. second 2. State what quantities the following SI units are used to measure. a. kg b. m c. s d. K 3. Give the power of 10 that each of the following prefixes represents. a. kilo b. micro c. centi d. deca e. mega 3 © MathTutorDVD.com 4. Write the following numbers in their base units. a. 5 kilometers b. 12 centimeters c. 2 micrograms d. 4.1 megagrams 5. Write the abbreviations for the following measurements. a. 67 micrograms b. 831 kilometers c. 1.2 meters d. 791 megagrams 4 © MathTutorDVD.com 6. Express the following numbers with an appropriate SI prefix (e.g., 5,000 g = 5 kg). a. 7800 m b. 5.0 x 10-6 g c. 7.8 x 106 m d. 1.6 x 10-3 g 7. Convert the following to scientific notation using the base SI unit. a. 4.51 microseconds b. 6700 grams c. -
The International System of Units (SI)
NAT'L INST. OF STAND & TECH NIST National Institute of Standards and Technology Technology Administration, U.S. Department of Commerce NIST Special Publication 330 2001 Edition The International System of Units (SI) 4. Barry N. Taylor, Editor r A o o L57 330 2oOI rhe National Institute of Standards and Technology was established in 1988 by Congress to "assist industry in the development of technology . needed to improve product quality, to modernize manufacturing processes, to ensure product reliability . and to facilitate rapid commercialization ... of products based on new scientific discoveries." NIST, originally founded as the National Bureau of Standards in 1901, works to strengthen U.S. industry's competitiveness; advance science and engineering; and improve public health, safety, and the environment. One of the agency's basic functions is to develop, maintain, and retain custody of the national standards of measurement, and provide the means and methods for comparing standards used in science, engineering, manufacturing, commerce, industry, and education with the standards adopted or recognized by the Federal Government. As an agency of the U.S. Commerce Department's Technology Administration, NIST conducts basic and applied research in the physical sciences and engineering, and develops measurement techniques, test methods, standards, and related services. The Institute does generic and precompetitive work on new and advanced technologies. NIST's research facilities are located at Gaithersburg, MD 20899, and at Boulder, CO 80303. -
Measuring Luminance with a Digital Camera
® Advanced Test Equipment Rentals Established 1981 www.atecorp.com 800-404-ATEC (2832) Measuring Luminance with a Digital Camera Peter D. Hiscocks, P.Eng Syscomp Electronic Design Limited [email protected] www.syscompdesign.com September 16, 2011 Contents 1 Introduction 2 2 Luminance Standard 3 3 Camera Calibration 6 4 Example Measurement: LED Array 9 5 Appendices 11 3.1 LightMeasurementSymbolsandUnits. 11 3.2 TypicalValuesofLuminance.................................... 11 3.3 AccuracyofPhotometricMeasurements . 11 3.4 PerceptionofBrightnessbytheHumanVisionSystem . 12 3.5 ComparingIlluminanceMeters. 13 3.6 FrostedIncandescentLampCalibration . 14 3.7 LuminanceCalibrationusingMoon,SunorDaylight . 17 3.8 ISOSpeedRating.......................................... 17 3.9 WorkFlowSummary ........................................ 18 3.10 ProcessingScripts.......................................... 18 3.11 UsingImageJToDeterminePixelValue . 18 3.12 UsingImageJToGenerateaLuminance-EncodedImage . 19 3.13 EXIFData.............................................. 19 References 22 1 Introduction There is growing awareness of the problem of light pollution, and with that an increasing need to be able to measure the levels and distribution of light. This paper shows how such measurements may be made with a digital camera. Light measurements are generally of two types: illuminance and lumi- nance. Illuminance is a measure of the light falling on a surface, measured in lux. Illuminanceis widely used by lighting designers to specify light levels. In the assessment of light pollution, horizontal and vertical measurements of illuminance are used to assess light trespass and over lighting. Luminance is the measure of light radiating from a source, measured in candela per square meter. Luminance is perceived by the human viewer as the brightness of a light source. In the assessment of light pollution, (a) Lux meter luminance can be used to assess glare, up-light and spill-light1. -
Radiometry and Photometry
Radiometry and Photometry Wei-Chih Wang Department of Power Mechanical Engineering National TsingHua University W. Wang Materials Covered • Radiometry - Radiant Flux - Radiant Intensity - Irradiance - Radiance • Photometry - luminous Flux - luminous Intensity - Illuminance - luminance Conversion from radiometric and photometric W. Wang Radiometry Radiometry is the detection and measurement of light waves in the optical portion of the electromagnetic spectrum which is further divided into ultraviolet, visible, and infrared light. Example of a typical radiometer 3 W. Wang Photometry All light measurement is considered radiometry with photometry being a special subset of radiometry weighted for a typical human eye response. Example of a typical photometer 4 W. Wang Human Eyes Figure shows a schematic illustration of the human eye (Encyclopedia Britannica, 1994). The inside of the eyeball is clad by the retina, which is the light-sensitive part of the eye. The illustration also shows the fovea, a cone-rich central region of the retina which affords the high acuteness of central vision. Figure also shows the cell structure of the retina including the light-sensitive rod cells and cone cells. Also shown are the ganglion cells and nerve fibers that transmit the visual information to the brain. Rod cells are more abundant and more light sensitive than cone cells. Rods are 5 sensitive over the entire visible spectrum. W. Wang There are three types of cone cells, namely cone cells sensitive in the red, green, and blue spectral range. The approximate spectral sensitivity functions of the rods and three types or cones are shown in the figure above 6 W. Wang Eye sensitivity function The conversion between radiometric and photometric units is provided by the luminous efficiency function or eye sensitivity function, V(λ). -
Candelas, Lumens and Lux by Owen Ransen
Candelas, Lumens and Lux By Owen Ransen A light introduction to illumination terms, ideas, and mathematics. Samples of the first two pages of each chapter. Table of Contents How to use this book.................................................................................5 1. Candelas, Lumens and Lux...................................................................6 2. Luminance.............................................................................................34 3. Photometries.........................................................................................50 4. Internal Lighting...................................................................................64 5. Glare.......................................................................................................84 6. Roadway Lighting...............................................................................112 7. Light sources and efficiency.............................................................134 How to use this book This book is for people who are starting to learn about lighting engineering or who need to know the basics of the subject. I've made it as simple, using graphical explanations of mathematical and physical ideas. There is mathematics in this book, but nothing beyond high school level, a few formulas, a tiny bit of trigonometry, nothing you need to be scared of! As we've seen in the financial crisis of 2008/2009, mathematics without a concrete idea of what it is happening in the real world can lead to disaster. So this book has -
The International System of Units (SI) - Conversion Factors For
NIST Special Publication 1038 The International System of Units (SI) – Conversion Factors for General Use Kenneth Butcher Linda Crown Elizabeth J. Gentry Weights and Measures Division Technology Services NIST Special Publication 1038 The International System of Units (SI) - Conversion Factors for General Use Editors: Kenneth S. Butcher Linda D. Crown Elizabeth J. Gentry Weights and Measures Division Carol Hockert, Chief Weights and Measures Division Technology Services National Institute of Standards and Technology May 2006 U.S. Department of Commerce Carlo M. Gutierrez, Secretary Technology Administration Robert Cresanti, Under Secretary of Commerce for Technology National Institute of Standards and Technology William Jeffrey, Director Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose. National Institute of Standards and Technology Special Publications 1038 Natl. Inst. Stand. Technol. Spec. Pub. 1038, 24 pages (May 2006) Available through NIST Weights and Measures Division STOP 2600 Gaithersburg, MD 20899-2600 Phone: (301) 975-4004 — Fax: (301) 926-0647 Internet: www.nist.gov/owm or www.nist.gov/metric TABLE OF CONTENTS FOREWORD.................................................................................................................................................................v -
How to Measure and Characterize LED Lighting Fixtures
How to Measure and Characterize LED Lighting Fixtures. Explanation of Photometric Quantities and Measurement Instruments Requirements According to CIE Standards and Other International Norms by Mikolaj Przybyla, Brand Director About GL Optic : GL Optic is the brand name of JUST Normlicht GmbH Germany the world's leading supplier of the standardized light solutions for printing and graphic arts industries. For more than 30 years Just has been developing the innovative solutions which are of the highest quality in standard-light viewing conditions. About GL Optic : The spectral light measurement project was created at the end of 2009 by Michael Gall the owner and CEO of Just Normlicht in cooperation with Jan Lalek, a Polish physicist who had been involved in the creation of the innovative LED tunable standard lighting systems. They also developed together the light quality assurance instruments installed at Just spectral measurements laboratory. How to measure LEDs When designing an LED lighting fixtures, we instantly had to deal with parameters and issues such as Flux and Colour shift with temperature and current, accurate current control and heat management are just a few of them. Therefore the accurate light measurement system is crucial for the development of these LED products. This presentation will cover basic information on light measurement procedures, international standards as well as the presentation of available instrumentation for very different measurement tasks from luminous flux measurement with integrating spheres to luminance