ASTM_F_2359_-_04_2011.pdf

Designation:F235904(Reapproved 2011)Standard Test Method forDetermining Color of a Membrane Switch Backlit withDiffuse Light Source1This standard is issued under the fixed designation F2359;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 theluminous color of a backlit membrane switch.As written,itapplies to a fully assembled switch.For specific purposes,itcan be applied to partially assembled switches,with theunderstanding that the results pertain only to the partialassembly and will be modified as the further assembly pro-ceeds.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.2.Terminology2.1 Definitions:2.1.1 graphic overlaya graphically illustrated layer,oftenattached to the top side of the switch assembly for protection,cosmetic purposes,or to indicate the location and function ofthe switch keys.2.1.2 illumination layera layer in the construction of amembrane switch,which may or may not be a physicallydistinct layer which contains or supports the source of illumi-nation for the switch.Examples are a flexible layer containinglight emitting diodes(LEDs),often either the top or bottomlayer of the switch,or a flexible layer of electroluminescent(EL)material,often a distinct and separate layer added atassembly.2.1.3 membrane switcha momentary switching device,inwhich at least one contact is on,or made of,a flexiblesubstrate.2.1.4 UUTunit under test.3.Significance and Use3.1 Illumination of a switch or of certain features of a switchoften has a functional purpose and must meet specification tosatisfy the functional requirements of the switch.3.2 Illumination of the switch can be affected by variationsin the quality and design of the overlay and its application.3.3 This test method addresses only the optical and visualappearance of the switch and not its electrical function.3.4 This test method is non-destructive.3.5 If this test method is applied to the entire switchassembly,the results can be applied to the whole device.However,it may be sufficient and practical to apply the testeither to a subassembly only,or to the illumination only,inwhich case the results apply to that layer only and the net effecton the fully assembled device must be extrapolated.4.Interferences4.1 Tests on incomplete assemblies give results appropri-ately to that state of assembly.Specifically,later application ofa graphic overlay may alter the results.4.2 Failure to fill the sampling aperture of the colorimeterwill bias the results in a way which is not necessarilypredictable and for which compensation cannot be made.4.3 Since every light source changes characteristics as itages,it must be recognized that the results apply to a particularinterval in the lifetime of the system.Characterization of theaging properties may be addressed in a separate test method.4.4 PerpendicularitySince the angular distribution ofemitted light can be altered by any material through which itpasses,it is important that photometer be held perpendicular tothe area to be sampled.4.5 TemperatureSince the performance of many lightsources can vary with temperature,it is important to allow theUUT to thermally stabilize,if necessary,and then record theambient temperature at which the measurements are made.4.6 Ambient LightStray light sources will be detected bythe photometer and will affect UUT color measurement.It isimportant to measure the ambient light before illuminating theUUT.This ambient light reading should be zero or as close tozero as possible.5.Apparatus5.1 A working or mounting surface to hold and support theUUT assembly,providing electrical access to the termination1This 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 1,2011.Published August 2011.Originallyapproved in 2004.Last previous edition approved in 2004 as F2359-04.DOI:10.1520/F2359-04R11.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 region from which the illumination is to be powered and visibleaccess to the regions at which the luminous color is to bemeasured.5.2 A power supply providing appropriate and adequatepower to drive the illumination device(s)with appropriateconnector(s).This should be specified as dc or ac,with voltageand power level given,and ideally should be switched.5.3 A calibrated device to measure the color of the lumi-nance.This is typically a spot colorimeter or similar equip-ment,with a fairly compact sampling aperture(1-cm diameterat the minimum working distance).Output should be in one ofthe CIE Tristimul