1、Designation: F 2360 04Standard Test Method forDetermining Luminance of a Membrane Switch Backlit withDiffuse Light Source1This standard is issued under the fixed designation F 2360; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers procedures for determining theluminance of a backlit membrane switch. As written,
3、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 bemodified as the further assembly proceeds.2. Terminology2.1 Definitions:2.1.1 graphic overlaya graphic
4、ally illustrated layer oftenattached to the topside (or first surface) of the switch assemblyfor 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 physicallydist
5、inct layer which contains or supports the source of illumi-nation for the membrane switch. Examples 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
6、layer addedat assembly.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 sp
7、ecification 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.
8、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 layer only,in which case the resul
9、ts apply to that layer only and the neteffect on the fully assembled device must be calculated,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 r
10、esults.4.2 Failure to fill the sampling aperture of the photometerwill bias the results in a 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
11、 system. Characteriza-tion of the aging properties may be addressed in a separate testmethod.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.
12、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
13、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 support theUUT assembly, providing electrical ac
14、cess to the terminationregion from which the illumination is to be powered and visibleaccess to the regions at which the luminance is to be measured.1This test method is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.18 on MembraneSwit
15、ches.Current edition approved May 1, 2004. Published June 2004.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 A power supply providing appropriate and adequatepower to drive the illumination device(s) with appropriateconnector(s
16、). 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 minimumworking distance). Ou
17、tput 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 A means to support the luminance measuring instrumentat a fixed distance and orientation to the UUT
18、.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 operating point.6.3 Mount
19、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 UUT luminous source
20、 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 Measure the luminanc
21、e 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 Photometer used, sample se
22、ttings, calibration status,and the size of the sampling aperture,7.1.7 Ambient temperature, and7.1.8 Date of test.8. Keywords8.1 backlit; colorimeter; diffuse light; electroluminescentmaterial; light emitting diodes; luminance; membrane switch;photometer; radiometer; video photometerASTM Internation
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26、 at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).F2360042
