DOCSLIB.ORG

The National Measurement System for Radiometry and Photometry

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

NATL INST jjlllllll A11107 QSfl07Q PUBLICATIONS NBSIR 75-939 The National Measurement System for Radiometry and Photometry H. J. Kostkowski Institute for Basic Standards National Bureau of Standards Washington. D C. 20234 November 1977 Final \ 5 loo J.S. DEPARTMENT OF COMMERCE NATIONAL BUREAU OF STANDARDS NBSIR 75-939 THE NATIONAL MEASUREMENT SYSTEM FOR RADIOMETRY AND PHOTOMETRY H. J. Kostkowski Institute for Basic Standards National Bureau of Standards Washington, D C. 20234 November 1977 Final U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary Dr. Sidney Harman, Under Secretary Jordan J. Baruch, Assistant Secretary for Science and Technology NATIONAL BUREAU OF STANDARDS. Ernest Ambler. Acting Director CONTENTS EXECUTIVE SUMMARY 1 1. INTRODUCTION 3 2. STRUCTURE OF THE MEASUREMENT SYSTEM 3 2.1 Conceptual System 3 2.2 Basic Technical Infrastructure 5 2.2.1 Documentary Specification System 5 2.2.1.1 Standardization Institutions 5 2.2.1.2 Survey of Documentary Standards 6 2.2.2 Instrumentation System 6 2.2.2.1 Measurement Tools and Techniques 6 2.2.2.2 The Instrumentation Industry 7 2.2.3 Reference Data 7 2.2.4 Reference Materials 7 2.2.5 Science and People 7 2.3 Reference Data 8 2.4 Dissemination and Enforcement Network 8 2.4.1 Central Standards Authorities 8 2.4.2 State and Local Office of Weights and Measures 8 2.4.3 Standards and Testing Laboratories and Services 8 2.4.4 Regulatory Agencies 8 2.5 Organizational Input-Output Transactions Matrix 8 2.5.1 Analysis of Suppliers and Users 8 2.5.2 Highlights of Transaction Matrix 9 3. IMPACT, STATUS AND TRENDS OF MEASUREMENT SYSTEM 11 3.1 Impact of Measurements 11 3.1.1 Functional, Technological, and Scientific Applications .... 11 3.1.2 Economic Impacts -- Costs and Benefits 12 3.1.3 Social, Human, Man-on-the-Street Impacts 13 3.2 Status and Trends of the System 14 4. SURVEY OF NBS SERVICES 14 4.1 The Past 14 4.2 The Present -- Scope of NBS Services 15 4.2.1 Description of NBS Services and Program 15 4.2.2 Users of NBS Services 16 4.2.3 Alternate Sources 16 4.2.4 Funding Sources for NBS Services 16 4.2.5 Mechanism for Supplying Services 16 4.3 Impact of NBS Services 17 4.3.1 Economic Impact of Major User Classes 17 4.3.2 Technological Impact of Services 17 4.3.3 Pay-off from Changes in NBS Services 18 4.4 Evaluation of NBS Program 19 4.5 Future 19 5. SUMMARY AND CONCLUSIONS 19 APPENDIX A 20 APPENDIX B 26 APPENDIX C 27 REFERENCES 23 i THE NATIONAL MEASUREMENT SYSTEM FOR RADIOMETRY AND PHOTOMETRY Henry J. Kostkowski Optical Physics Division November 1977 EXECUTIVE SUMMARY This National Measurement System Study is time, and the responsivity of most radiom- on the measurement of light. More specifi- eters also varies with these and other cally it is concerned with the measurement parameters, making such measurements a of the energy or power in ultraviolet, difficult, multi-dimensional problem. In visible and infrared radiation. addition, most of the people needing radiom- The study was undertaken to determine the etry have not been trained in the field. importance of such measurements in the U.S., There are relatively few experts available. the accuracy and ease with which they could As a result of these two factors, measurement be made, the adequacy of this capability, accuracy is poor and large differences in and the nature of the program NBS should measurement are widespread. Much time and pursue in this measurement area. money is spent trying to resolve these In the last ten years, the economic and differences, particularly when mass produced social impact of radiometric and photometric products require components from various measurements has increased significantly. companies and these components must meet Such measurements are required in the man- radiometric or photometric specifications. ufacture of cameras, color TV and copying The cost of inadequate radiometry and machines. Ultraviolet radiation is being photometry is very high. The electro- used extensively for the polymerization of optical industry alone has annual sales industrial coatings. An attempt is being approaching 15 billion dollars per year. A made to use radiometry in measuring atmos- leading instrument manufacturer estimates pheric temperatures for the purpose of that about $200 million is spent each year forecasting weather. New solid-state lamps in calibrating radiometric systems or (LEDs) are used in a variety of visual resolving discrepancies in radiometric displays. Phototherapy is used almost measurements. If better radiometry can exclusively in the treatment of some diseases improve long-term weather forecasting as (e.g. jaundice in the newborn). Regulatory predicted, the economic impact would be agencies are concerned with the hazardous tremendous. It is virtually impossible to effects of UV on the eyes and skin (skin estimate the cost of inadequate radiometry cancer), particularly in industrial environ- relative to medical and safety applications, ments. Dentists are now using a commercially but public health and safety are certainly available "UV gun" for curing various new given a high priority in this country. dental materials. Applications in the lamp Adequate radiometry today means making industry are increasing because of our measurements with a few percent accuracy energy problems. Twenty-five percent of the commonplace. This will require greater U.S. electrical power is used for lighting, expertise in the system and more accurate, and thus, developing lamps that will produce easy-to-use, and less expensive standards the same light for less electrical power has and techniques. a high priority. Improving the utilization NBS has addressed itself to solving of solar energy will require better measure- these problems. It helped organize the ments than are now available. All of these Council for Optical Radiation Measurement uses and applications of light require (CORM), a group largely representing industry radiometry or photometry. Many of them will and providing detailed information and a require a state-of-the-art accuracy of a few consensus of the needs in the system. It per cent in order to achieve their objectives. has worked with the Illuminating Engineering Unfortunately, the current radiometric Society (IES), the Commission Internationale and photometric measurement system is inade- de L'Eclairage (CIE), and the Infrared Infor- quate for the many uses and applications mation Symposia (IRIS). NBS is developing described. Radiometric measurements are more accurate, easy-to-use, less expensive among the most difficult measurements to standards and techniques and is beginning make. The radiant power varies with position, to monitor the capability of the system by direction, wavelength, polarization and inter! aboratory comparisons. It has created specialized publications to insure that all this information is efficiently disseminated. Finally, NBS is also starting to produce a Self-Study Manual for Optical Radiation Measurements. This is expected to signifi- cantly upgrade the level of expertise in the U.S. in this area. In summary, this study has shown that radiometry and photometry are having a significant economic and social impact in the U.S. today and this impact is expected to increase. The capability of this portion of the measurement system is inadequate for today's needs. An accuracy of a few percent is frequently needed; 10-50 percent is commonplace. The reason is that radiometric and photometric measurements are very difficult to make, and there is too little expertise to make these difficult measurements. NBS' program is designed to improve the situation by (1) making the measurements easier through simpler, inexpensive standards and techniques and (2) increasing the expertise through a Self-Study Manual on the subject. 2 1. INTRODUCTION Everyone has his own built-in photom- NBS. During and following the preparation eter -- the eye. The normal eye can see of these reports, a new NBS program in differences in light intensity and color of radiometry and photometry evolved. 1%. Yet the most sophisticated instruments In general, the approach used in con- available today do not measure the absol ute ducting this National Measurement System intensity of light with an accuracy of Study was to try to answer the following better than 1%. Discrepancies of 10" are four questions: common and the 1% accuracy is only realized 1. Why are radiometry and photometry in a few cases and in the best standards important in the U.S. today? laboratories of the world. 2. What is the status of radiometry In spite of this situation, the accuracy and photometry in the U.S.? and efficiency with which radiometry and 3. What is needed? photometry can be performed affects every- 4. How should NBS respond? one in this country. Such measurements are Information was obtained primarily from per- important in sonal discussions and correspondence with - Developing more efficient lamps (one- many concerned individuals in industry and fourth of the electricity used in the government. Extensive interaction with U.S. is for lighting) industry and other government agencies is - Developing the use of solar energy continuing. Conditions and needs change. - Treating various diseases by photo- The NBS program in radiometry and photometry therapy (e.g. jaundice in over 10,000 must be updated to take account of these infants born in the U.S. each year) changes. The current report is a "snapshot", - Specifying and controlling ultra- "taken" in March 1975, of the U.S. National violet radiation hazards (these can Measurement System for Radiometry and cause eye damage and skin cancer) Photo-metry. It is a summary of what we - Pollution monitoring have learned about the System and what we - Weather forecasting are trying to do to improve it. - Automating the production of many manufactured products such as lamps, 2.
Recommended publications
  • Glossary Physics (I-Introduction)

    Glossary Physics (I-Introduction)

    1 Glossary Physics (I-introduction) - Efficiency: The percent of the work put into a machine that is converted into useful work output; = work done / energy used [-]. = eta In machines: The work output of any machine cannot exceed the work input (<=100%); in an ideal machine, where no energy is transformed into heat: work(input) = work(output), =100%. Energy: The property of a system that enables it to do work. Conservation o. E.: Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes. Equilibrium: The state of an object when not acted upon by a net force or net torque; an object in equilibrium may be at rest or moving at uniform velocity - not accelerating. Mechanical E.: The state of an object or system of objects for which any impressed forces cancels to zero and no acceleration occurs. Dynamic E.: Object is moving without experiencing acceleration. Static E.: Object is at rest.F Force: The influence that can cause an object to be accelerated or retarded; is always in the direction of the net force, hence a vector quantity; the four elementary forces are: Electromagnetic F.: Is an attraction or repulsion G, gravit. const.6.672E-11[Nm2/kg2] between electric charges: d, distance [m] 2 2 2 2 F = 1/(40) (q1q2/d ) [(CC/m )(Nm /C )] = [N] m,M, mass [kg] Gravitational F.: Is a mutual attraction between all masses: q, charge [As] [C] 2 2 2 2 F = GmM/d [Nm /kg kg 1/m ] = [N] 0, dielectric constant Strong F.: (nuclear force) Acts within the nuclei of atoms: 8.854E-12 [C2/Nm2] [F/m] 2 2 2 2 2 F = 1/(40) (e /d ) [(CC/m )(Nm /C )] = [N] , 3.14 [-] Weak F.: Manifests itself in special reactions among elementary e, 1.60210 E-19 [As] [C] particles, such as the reaction that occur in radioactive decay.
  • CIE Technical Note 004:2016

    CIE Technical Note 004:2016

    TECHNICAL NOTE The Use of Terms and Units in Photometry – Implementation of the CIE System for Mesopic Photometry CIE TN 004:2016 CIE TN 004:2016 CIE Technical Notes (TN) are short technical papers summarizing information of fundamental importance to CIE Members and other stakeholders, which either have been prepared by a TC, in which case they will usually form only a part of the outputs from that TC, or through the auspices of a Reportership established for the purpose in response to a need identified by a Division or Divisions. This Technical Note has been prepared by CIE Technical Committee 2-65 of Division 2 “Physical Measurement of Light and Radiation" and has been approved by the Board of Administration as well as by Division 2 of the Commission Internationale de l'Eclairage. The document reports on current knowledge and experience within the specific field of light and lighting described, and is intended to be used by the CIE membership and other interested parties. It should be noted, however, that the status of this document is advisory and not mandatory. Any mention of organizations or products does not imply endorsement by the CIE. Whilst every care has been taken in the compilation of any lists, up to the time of going to press, these may not be comprehensive. CIE 2016 - All rights reserved II CIE, All rights reserved CIE TN 004:2016 The following members of TC 2-65 “Photometric measurements in the mesopic range“ took part in the preparation of this Technical Note. The committee comes under Division 2 “Physical measurement of light and radiation”.
  • Fundametals of Rendering - Radiometry / Photometry

    Fundametals of Rendering - Radiometry / Photometry

    Fundametals of Rendering - Radiometry / Photometry “Physically Based Rendering” by Pharr & Humphreys •Chapter 5: Color and Radiometry •Chapter 6: Camera Models - we won’t cover this in class 782 Realistic Rendering • Determination of Intensity • Mechanisms – Emittance (+) – Absorption (-) – Scattering (+) (single vs. multiple) • Cameras or retinas record quantity of light 782 Pertinent Questions • Nature of light and how it is: – Measured – Characterized / recorded • (local) reflection of light • (global) spatial distribution of light 782 Electromagnetic spectrum 782 Spectral Power Distributions e.g., Fluorescent Lamps 782 Tristimulus Theory of Color Metamers: SPDs that appear the same visually Color matching functions of standard human observer International Commision on Illumination, or CIE, of 1931 “These color matching functions are the amounts of three standard monochromatic primaries needed to match the monochromatic test primary at the wavelength shown on the horizontal scale.” from Wikipedia “CIE 1931 Color Space” 782 Optics Three views •Geometrical or ray – Traditional graphics – Reflection, refraction – Optical system design •Physical or wave – Dispersion, interference – Interaction of objects of size comparable to wavelength •Quantum or photon optics – Interaction of light with atoms and molecules 782 What Is Light ? • Light - particle model (Newton) – Light travels in straight lines – Light can travel through a vacuum (waves need a medium to travel in) – Quantum amount of energy • Light – wave model (Huygens): electromagnetic radiation: sinusiodal wave formed coupled electric (E) and magnetic (H) fields 782 Nature of Light • Wave-particle duality – Light has some wave properties: frequency, phase, orientation – Light has some quantum particle properties: quantum packets (photons). • Dimensions of light – Amplitude or Intensity – Frequency – Phase – Polarization 782 Nature of Light • Coherence - Refers to frequencies of waves • Laser light waves have uniform frequency • Natural light is incoherent- waves are multiple frequencies, and random in phase.
  • Light and Illumination

    Light and Illumination

    ChapterChapter 3333 -- LightLight andand IlluminationIllumination AAA PowerPointPowerPointPowerPoint PresentationPresentationPresentation bybyby PaulPaulPaul E.E.E. Tippens,Tippens,Tippens, ProfessorProfessorProfessor ofofof PhysicsPhysicsPhysics SouthernSouthernSouthern PolytechnicPolytechnicPolytechnic StateStateState UniversityUniversityUniversity © 2007 Objectives:Objectives: AfterAfter completingcompleting thisthis module,module, youyou shouldshould bebe ableable to:to: •• DefineDefine lightlight,, discussdiscuss itsits properties,properties, andand givegive thethe rangerange ofof wavelengthswavelengths forfor visiblevisible spectrum.spectrum. •• ApplyApply thethe relationshiprelationship betweenbetween frequenciesfrequencies andand wavelengthswavelengths forfor opticaloptical waves.waves. •• DefineDefine andand applyapply thethe conceptsconcepts ofof luminousluminous fluxflux,, luminousluminous intensityintensity,, andand illuminationillumination.. •• SolveSolve problemsproblems similarsimilar toto thosethose presentedpresented inin thisthis module.module. AA BeginningBeginning DefinitionDefinition AllAll objectsobjects areare emittingemitting andand absorbingabsorbing EMEM radiaradia-- tiontion.. ConsiderConsider aa pokerpoker placedplaced inin aa fire.fire. AsAs heatingheating occurs,occurs, thethe 1 emittedemitted EMEM waveswaves havehave 2 higherhigher energyenergy andand 3 eventuallyeventually becomebecome visible.visible. 4 FirstFirst redred .. .. .. thenthen white.white. LightLightLight maymaymay bebebe defineddefineddefined
  • Black Body Radiation and Radiometric Parameters

    Black Body Radiation and Radiometric Parameters

    Black Body Radiation and Radiometric Parameters: All materials absorb and emit radiation to some extent. A blackbody is an idealization of how materials emit and absorb radiation. It can be used as a reference for real source properties. An ideal blackbody absorbs all incident radiation and does not reflect. This is true at all wavelengths and angles of incidence. Thermodynamic principals dictates that the BB must also radiate at all ’s and angles. The basic properties of a BB can be summarized as: 1. Perfect absorber/emitter at all ’s and angles of emission/incidence. Cavity BB 2. The total radiant energy emitted is only a function of the BB temperature. 3. Emits the maximum possible radiant energy from a body at a given temperature. 4. The BB radiation field does not depend on the shape of the cavity. The radiation field must be homogeneous and isotropic. T If the radiation going from a BB of one shape to another (both at the same T) were different it would cause a cooling or heating of one or the other cavity. This would violate the 1st Law of Thermodynamics. T T A B Radiometric Parameters: 1. Solid Angle dA d r 2 where dA is the surface area of a segment of a sphere surrounding a point. r d A r is the distance from the point on the source to the sphere. The solid angle looks like a cone with a spherical cap. z r d r r sind y r sin x An element of area of a sphere 2 dA rsin d d Therefore dd sin d The full solid angle surrounding a point source is: 2 dd sind 00 2cos 0 4 Or integrating to other angles < : 21cos The unit of solid angle is steradian.
  • Section 22-3: Energy, Momentum and Radiation Pressure

    Section 22-3: Energy, Momentum and Radiation Pressure

    Answer to Essential Question 22.2: (a) To find the wavelength, we can combine the equation with the fact that the speed of light in air is 3.00 " 108 m/s. Thus, a frequency of 1 " 1018 Hz corresponds to a wavelength of 3 " 10-10 m, while a frequency of 90.9 MHz corresponds to a wavelength of 3.30 m. (b) Using Equation 22.2, with c = 3.00 " 108 m/s, gives an amplitude of . 22-3 Energy, Momentum and Radiation Pressure All waves carry energy, and electromagnetic waves are no exception. We often characterize the energy carried by a wave in terms of its intensity, which is the power per unit area. At a particular point in space that the wave is moving past, the intensity varies as the electric and magnetic fields at the point oscillate. It is generally most useful to focus on the average intensity, which is given by: . (Eq. 22.3: The average intensity in an EM wave) Note that Equations 22.2 and 22.3 can be combined, so the average intensity can be calculated using only the amplitude of the electric field or only the amplitude of the magnetic field. Momentum and radiation pressure As we will discuss later in the book, there is no mass associated with light, or with any EM wave. Despite this, an electromagnetic wave carries momentum. The momentum of an EM wave is the energy carried by the wave divided by the speed of light. If an EM wave is absorbed by an object, or it reflects from an object, the wave will transfer momentum to the object.
  • Multidisciplinary Design Project Engineering Dictionary Version 0.0.2

    Multidisciplinary Design Project Engineering Dictionary Version 0.0.2

    Multidisciplinary Design Project Engineering Dictionary Version 0.0.2 February 15, 2006 . DRAFT Cambridge-MIT Institute Multidisciplinary Design Project This Dictionary/Glossary of Engineering terms has been compiled to compliment the work developed as part of the Multi-disciplinary Design Project (MDP), which is a programme to develop teaching material and kits to aid the running of mechtronics projects in Universities and Schools. The project is being carried out with support from the Cambridge-MIT Institute undergraduate teaching programe. For more information about the project please visit the MDP website at http://www-mdp.eng.cam.ac.uk or contact Dr. Peter Long Prof. Alex Slocum Cambridge University Engineering Department Massachusetts Institute of Technology Trumpington Street, 77 Massachusetts Ave. Cambridge. Cambridge MA 02139-4307 CB2 1PZ. USA e-mail: [email protected] e-mail: [email protected] tel: +44 (0) 1223 332779 tel: +1 617 253 0012 For information about the CMI initiative please see Cambridge-MIT Institute website :- http://www.cambridge-mit.org CMI CMI, University of Cambridge Massachusetts Institute of Technology 10 Miller’s Yard, 77 Massachusetts Ave. Mill Lane, Cambridge MA 02139-4307 Cambridge. CB2 1RQ. USA tel: +44 (0) 1223 327207 tel. +1 617 253 7732 fax: +44 (0) 1223 765891 fax. +1 617 258 8539 . DRAFT 2 CMI-MDP Programme 1 Introduction This dictionary/glossary has not been developed as a definative work but as a useful reference book for engi- neering students to search when looking for the meaning of a word/phrase. It has been compiled from a number of existing glossaries together with a number of local additions.
  • Variable Star Photometry with a DSLR Camera

    Variable Star Photometry with a DSLR Camera

    Variable star photometry with a DSLR camera Des Loughney Introduction now be studied. I have used the method to create lightcurves of stars with an amplitude of under 0.2 magnitudes. In recent years it has been found that a digital single lens reflex (DSLR) camera is capable of accurate unfiltered pho- tometry as well as V-filter photometry.1 Undriven cameras, Equipment with appropriate quality lenses, can do photometry down to magnitude 10. Driven cameras, using exposures of up to 30 seconds, can allow photometry to mag 12. Canon 350D/450D DSLR cameras are suitable for photome- The cameras are not as sensitive or as accurate as CCD try. My experiments suggest that the cameras should be cameras primarily because they are not cooled. They do, used with quality lenses of at least 50mm aperture. This however, share some of the advantages of a CCD as they allows sufficient light to be gathered over the range of have a linear response over a large portion of their range1 exposures that are possible with an undriven camera. For and their digital data can be accepted by software pro- bright stars (over mag 3) lenses of smaller aperture can be grammes such as AIP4WIN.2 They also have their own ad- used. I use two excellent Canon lenses of fixed focal length. vantages as their fields of view are relatively large. This makes One is the 85mm f1.8 lens which has an aperture of 52mm. variable stars easy to find and an image can sometimes in- This allows undriven photometry down to mag 8.
  • Chapter 4 Introduction to Stellar Photometry

    Chapter 4 Introduction to Stellar Photometry

    Chapter 4 Introduction to stellar photometry Goal-of-the-Day Understand the concept of stellar photometry and how it can be measured from astro- nomical observations. 4.1 Essential preparation Exercise 4.1 (a) Have a look at www.astro.keele.ac.uk/astrolab/results/week03/week03.pdf. 4.2 Fluxes and magnitudes Photometry is a technique in astronomy concerned with measuring the brightness of an astronomical object’s electromagnetic radiation. This brightness of a star is given by the flux F : the photon energy which passes through a unit of area within a unit of time. The flux density, Fν or Fλ, is the flux per unit of frequency or per unit of wavelength, respectively: these are related to each other by: Fνdν = Fλdλ (4.1) | | | | Whilst the total light output from a star — the bolometric luminosity — is linked to the flux, measurements of a star’s brightness are usually obtained within a limited frequency or wavelength range (the photometric band) and are therefore more directly linked to the flux density. Because the measured flux densities of stars are often weak, especially at infrared and radio wavelengths where the photons are not very energetic, the flux density is sometimes expressed in Jansky, where 1 Jy = 10−26 W m−2 Hz−1. However, it is still very common to express the brightness of a star by the ancient clas- sification of magnitude. Around 120 BC, the Greek astronomer Hipparcos ordered stars in six classes, depending on the moment at which these stars became first visible during evening twilight: the brightest stars were of the first class, and the faintest stars were of the sixth class.
  • Properties of Electromagnetic Waves Any Electromagnetic Wave Must Satisfy Four Basic Conditions: 1

    Properties of Electromagnetic Waves Any Electromagnetic Wave Must Satisfy Four Basic Conditions: 1

    Chapter 34 Electromagnetic Waves The Goal of the Entire Course Maxwell’s Equations: Maxwell’s Equations James Clerk Maxwell •1831 – 1879 •Scottish theoretical physicist •Developed the electromagnetic theory of light •His successful interpretation of the electromagnetic field resulted in the field equations that bear his name. •Also developed and explained – Kinetic theory of gases – Nature of Saturn’s rings – Color vision Start at 12:50 https://www.learner.org/vod/vod_window.html?pid=604 Correcting Ampere’s Law Two surfaces S1 and S2 near the plate of a capacitor are bounded by the same path P. Ampere’s Law states that But it is zero on S2 since there is no conduction current through it. This is a contradiction. Maxwell fixed it by introducing the displacement current: Fig. 34-1, p. 984 Maxwell hypothesized that a changing electric field creates an induced magnetic field. Induced Fields . An increasing solenoid current causes an increasing magnetic field, which induces a circular electric field. An increasing capacitor charge causes an increasing electric field, which induces a circular magnetic field. Slide 34-50 Displacement Current d d(EA)d(q / ε) 1 dq E 0 dt dt dt ε0 dt dq d ε E dt0 dt The displacement current is equal to the conduction current!!! Bsd μ I μ ε I o o o d Maxwell’s Equations The First Unified Field Theory In his unified theory of electromagnetism, Maxwell showed that electromagnetic waves are a natural consequence of the fundamental laws expressed in these four equations: q EABAdd 0 εo dd Edd s BE B s μ I μ ε dto o o dt QuickCheck 34.4 The electric field is increasing.
  • Basics of Photometry Photometry: Basic Questions

    Basics of Photometry Photometry: Basic Questions

    Basics of Photometry Photometry: Basic Questions • How do you identify objects in your image? • How do you measure the flux from an object? • What are the potential challenges? • Does it matter what type of object you’re studying? Topics 1. General Considerations 2. Stellar Photometry 3. Galaxy Photometry I: General Considerations 1. Garbage in, garbage out... 2. Object Detection 3. Centroiding 4. Measuring Flux 5. Background Flux 6. Computing the noise and correlated pixel statistics I: General Considerations • Object Detection How do you mathematically define where there’s an object? I: General Considerations • Object Detection – Define a detection threshold and detection area. An object is only detected if it has N pixels above the threshold level. – One simple example of a detection algorithm: • Generate a segmentation image that includes only pixels above the threshold. • Identify each group of contiguous pixels, and call it an object if there are more than N contiguous pixels I: General Considerations • Object Detection I: General Considerations • Object Detection Measuring Flux in an Image • How do you measure the flux from an object? • Within what area do you measure the flux? The best approach depends on whether you are looking at resolved or unresolved sources. Background (Sky) Flux • Background – The total flux that you measure (F) is the sum of the flux from the object (I) and the sky (S). F = I + S = #Iij + npix " sky / pixel – Must accurately determine the level of the background to obtaining meaningful photometry ! (We’ll return to this a bit later.) Photometric Errors Issues impacting the photometric uncertainties: • Poisson Error – Recall that the statistical uncertainty is Poisson in electrons rather than ADU.
  • STHF-R Ultra High Flux Gamma Probe Data Sheet

    STHF-R Ultra High Flux Gamma Probe Data Sheet

    Features STHF-R™ Ultra High ■ Measurement of H*(10) Flux Gamma Probe ambient gamma dose equivalent rate up to 1000 Sv/h (100 000 R/h) Description ■ To be connected to The STHF-R ultra high flux Radiagem™, MIP 10 Digital™ probe is designed for the or Avior ® meters measurements of very high ■ Waterproof: 80 m (262.5 ft) gamma dose-equivalent rates water depth up to 1000 Sv/h. ■ Detector: Silicon diode This probe is especially ■ 5 kSv maximum integrated designed for ultra high flux dose measurement which can be found in pools in nuclear ■ Compact portable design for power plants or in recycling detector and detector cable facilities. Effectively this on reel probes box is stainless steel based and waterproof up to 80 m (164 ft) underwater. It can be laid underwater in the storage pools Borated water. An optional ballast weight can be supplied to ease underwater measurements. The STHF-R probe is composed of two matched units: ■ The measurement probe including the silicon diode and the associated analog electronics. ■ An interface case which houses the processing electronics that are more sensitive to radiation; this module can be remotely located up to 50 m (164 ft) from the measurement spot. ■ An intermediate connection point with 50 m length cable to which the interface case can be connected. The STHF-R probe can be connected directly to Avior, Radiagem or MIP 10 Digital meters. The STHF-R unit receives power from the survey meter during operation. STHF-R instruments include key components of hardware circuitry (high voltage power supply, amplifier, discriminator, etc.).