1、Designation: F2360 08 (Reapproved 2015)1Standard Test Method forDetermining Luminance of a Membrane Switch Backlit withDiffuse Light Source1This standard is issued under the fixed designation F2360; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se 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.1NOTEThe spelling of interlaboratory in 8.1 was corrected editorially in June 2015.1. Scope1.1 This te
3、st method covers procedures for determining theluminance of a backlit membrane switch. As written, it appliesto a fully assembled switch. For specific purposes, it can beapplied to partially assembled switches with the understandingthat the results pertain only to the partial assembly and will bemod
4、ified as the further assembly proceeds.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the
5、user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Terminology2.1 Definitions:2.1.1 graphic overlaya graphically illustrated layer oftenattached to the topside (or first surface) of the switch assembl
6、yfor protection, cosmetic purposes, or to indicate the locationand function of the 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 membrane switch. E
7、xamples are a flexible layercontaining light emitting diodes (LEDs), often either the top orbottom layer of the switch, or a flexible layer of electrolumi-nescent (EL) material, often a distinct and separate layer addedat assembly.2.1.3 membrane switcha momentary switching device, inwhich at least o
8、ne 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 swit
9、ch 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 swi
10、tchassembly, 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 layer only,in which case the results apply to that layer only and the neteffect on the fully assembled device must be calculat
11、ed,extrapolated, or otherwise inferred.4. Interferences4.1 Tests on incomplete assemblies give results appropriateto that state of assembly. Specifically, later application of agraphic overlay may alter the results.4.2 Failure to fill the sampling aperture of the photometerwill bias the results in a
12、 way which is not necessarilypredictable.4.3 Since every system of illumination changes characteris-tics as it ages, it must be recognized that the results apply to aparticular interval in the lifetime of the system. Characteriza-tion of the aging properties may be addressed in a separate testmethod
13、.4.4 PerpendicularitySince the angular distribution ofemitted light can be altered by any material through which itpasses, it is important that the photometer be held perpendicu-lar to the area to be sampled.4.5 TemperatureSince the performance of many lightsources can vary with temperature, it is i
14、mportant to allow the1This test method is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.18 on PrintedElectronics.Current edition approved June 1, 2015. Published July 2015. Originally approvedin 2004. Last previous edition approved in
15、 2008 as F2360-08. DOI: 10.1520/F2360-08R15E01.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1UUT to thermally stabilize, if necessary, and then record theambient temperature at which the measurements are made.4.6 Ambient LightStray
16、light sources will be detected bythe photometer and will affect the UUT luminance measure-ment. It is important to measure the ambient light beforeilluminating the UUT. This ambient light reading should bezero or as close to zero as possible.5. Apparatus5.1 A working or mounting surface to hold and
17、support theUUT assembly, providing electrical access to the terminationregion from which the illumination is to be powered and visibleaccess to the regions at which the luminance is to be measured.5.2 A power supply providing appropriate and adequatepower to drive the illumination device(s) with app
18、ropriateconnector(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 surface luminance (orradiance). This is typically a spot photometer, with a fairlycompact sampling aperture (1-cm diameter at the minimumwo
19、rking distance). Output should be in foot lamberts (candelaper meter squared). Alternatively, a radiometer may be used, oreven a video photometer, but cognizance must be maintainedof the output units and calibration.5.4 Ameans to support the luminance measuring instrumentat a fixed distance and orie
20、ntation to the UUT.5.5 A means to control stray light and prevent it fromentering the aperture of the photometer.6. Procedure6.1 Mount UUT on the working surface with the illuminatedsurface visible.6.2 Attach a switched power source as appropriate to theillumination device set to the design operatin
21、g point.6.3 Mount the photometer or luminance meter so that theaxis of its field of view is perpendicular to the area of the UUTto be measured. Ensure that the sampling aperture is filled bythe area to be measured on the UUT.6.4 Measure the stray light level by taking a photometerreading while the U
22、UT luminous source is not powered. If thisvalue is not zero or very close to it, do not proceed, but takesteps to reduce the stray light present. This may be as simple asreducing the ambient room light or switching the overheadlights off altogether.6.5 Switch on the luminous source in the UUT.6.6 Me
23、asure the luminance of the sample area of the UUT.7. Report7.1 Report the following information:7.1.1 State of UUT (assembled or not),7.1.2 Stray light level,7.1.3 Luminance measured,7.1.4 Power conditions for the illumination device,7.1.5 Location and size of the sample area or areas,7.1.6 Photomet
24、er used, sample settings, calibration status,and the size of the sampling aperture,7.1.7 Ambient temperature, and7.1.8 Date of test.8. Precision and Bias8.1 The precision of this test method is based on aninterlaboratory study of F2360-04, conducted in 2006. Each ofsix laboratories tested three diff
25、erent types of lamps. A single“test result” represents an individual determination. Everylaboratory produced twelve test results for each material.28.1.1 Repeatability Two test results obtained within onelaboratory shall be judged not equivalent if they differ by morethan the “r” value for that mate
26、rial; “r” is the intervalrepresenting the critical difference between two test results forthe same material, obtained by the same operator using thesame equipment on the same day in the same laboratory.8.1.2 Reproducibilty Two test results shall be judged notequivalent if they differ by more than th
27、e “R” value for thatmaterial; “R” is the interval representing the difference be-tween two test results for the same material, obtained bydifferent operators using different equipment in different labo-ratories.8.1.3 Any judgment in accordance with these two state-ments would have an approximate 95
28、% probability of beingcorrect.8.2 BiasAt the time of the study, there was no acceptedreference material suitable for determining the bias for this testmethod, therefore no statement on bias is being made.8.3 The precision statement was determined through statis-tical examination of 216 results, from
29、 six laboratories, on threetypes of lamps. The three types of lamps used are describedbelow:Lamp 1: manufactured by Metromark: color: amber (X =0.521, Y = 0.462)Lamp 2: manufactured by Nelson Nameplate: color: green(X = 0.186, Y = 0.449)Lamp 3: manufactured by Durel: color: blue (X = 0.155, Y= 0.204
30、)8.3.1 To judge the equivalency of two test results, it isrecommended to choose the lamp closest in characteristics tothe test lamp.9. Keywords9.1 backlit; colorimeter; diffuse light; electroluminescentmaterial; light emitting diodes; luminance; membrane switch;photometer; radiometer; video photomet
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36、Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 1 Luminance (foot lamberts)Lamp AveragexRepeatability StandardDeviationsrReproducibilityStandard DeviationsRRepeatability LimitrReproducibility LimitR1 2.6140 0.0996 0.4386 0.28 1.232 16.0102 0.3321 1.9016 0.93 5.323 4.4033 0.1878 0.5747 0.53 1.61F2360 08 (2015)13
