ASTM_F_2964_-_12.pdf

Designation:F296412Standard Test Method forDetermining the Uniformity of the Luminance of anElectroluminescent Lamp or Other Diffuse Lighting Device1This standard is issued under the fixed designation F2964;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers procedures for determining theuniformity of the luminance of an electroluminescent(EL)lamp.While written specifically for the purpose of evaluatingEL devices,which are intrinsically very uniform,it can beapplied(judiciously)to the measurement of any diffuse,essentially planar,light source.For specific purposes,it can beapplied to partially assembled devices into which the illumi-nation is installed(such as a membrane switch)as a diagnosticfor the performance of the entire device.In such a case it mustbe understood that the results pertain only to the partialassembly and will be modified as the further assembly pro-ceeds.1.2 The method is to take a 2-dimensional set ofmeasurements,sampling the surface of the unit under test withappropriate density.The method is restricted to measuringluminance only,since variations in color will also show asluminance non-uniformity especially in any photoptically cali-brated measuring device.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2F2360 Test Method for Determining Luminance of a Mem-brane Switch Backlit with Diffuse Light SourceF2771 Test Method for Determining the Luminance Curveof an Electroluminescent Lamp at Ambient Conditions3.Terminology3.1 Definitions:3.1.1 luminance,nmeasure of the brightness or luminousintensity of light,usually expressed in units of candelas persquare metre(cd/m2)or foot lamberts.1 fL=3.426 cd/m2.3.1.2 luminance curve,na graphical representation of thevariation of luminance with time(implicitly under unvaryingoperating conditions).3.1.3 electroluminescent lamp(EL lamp),nessentially acapacitor structure with phosphor and a dielectric sandwichedbetween electrodes,one of which is transparent to allow lightto escape.Application of an ac voltage across the electrodesgenerates a charging field within the phosphor,which causes itto emit light.3.1.4 time to half luminance(THL),nthe elapsed operat-ing time over which the luminance of a lamp maintained underconstant power will be reduced to half of its initial value.3.1.5 UUT,nunit under test.4.Significance and Use4.1 Application of an EL lamp(or other diffuse lightingsource)to illuminate a device has a functional purpose andmust meet specifications to satisfy the functional requirementsof the device.4.2 Illumination of the device or application can be affectedby variations in the quality,efficiency,and design of the lampand any attendant mounting or shading fixtures.4.3 This test method addresses only the optical and visualappearance of the lamp and not its electrical function.4.4 This test method is non-destructive.4.5 This test method is described for application to theillumination layer in which case the results apply to that layeronly.However,it may be desirable and practical to apply thetest to a further assembly or to a fully assembled device withbuilt in illumination.In such a case,the results refer specifi-cally to the subassembly or the entire device respectively.1This test method is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.18 on MembraneSwitches.Current edition approved July 1,2012.Published August 2012.DOI:10.1520/F2964122For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.Interferences5.1 State of AssemblyTests on incomplete assemblies giveresults appropriate to that state of assembly.Specifically,laterapplication of mounting hardware,baffling,or fixtures mayalter the results.5.2 Filling of ApertureFailure to fill the sampling apertureof the photometer will bias the results in a way which is notnecessarily predictable.5.3 Age of DeviceSince every system of illuminationchanges characteristics as it ages,it must be recognized that theresults apply to a particular interval in the lifetime of thesystem.Characterization