ASTM_F_1597_-_02.pdf

Designation:F 1597 02Standard Test Method forDetermining the Actuation Force and Contact Force of aMembrane Switch1This standard is issued under the fixed designation F 1597;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(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the measurement of actuationforce or contact force,or both,of a membrane switch utilizinga pre-determined resistance value.1.2 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:2D 2240 Test Method for Rubber Property-Durometer Hard-nessF 1570 Test Method for Determining the Tactile Ratio of aMembrane Switch3.Terminology3.1 Definitions:3.1.1 actuation force(Fa)the maximum force measureprior to or including point at which contact closure is achievedon a membrane switch.3.1.2 contact closure(make)the event at which a specifiedresistance is achieved.3.1.3 contact force(Fc)the force at contact closure.3.1.4 membrane switcha momentary switching device inwhich at least one contact is on,or made of,a flexiblesubstrate.3.1.5 non-tactile switcha switch assembly that has atactile ratio equal to zero(see Test Method F 1570).3.1.6 specified resistancemaximum allowable resistanceas measured between two terminations whose internal switchcontacts are held closed to complete a circuit.3.1.7 tactile switcha switch assembly that provides atactile ratio greater than zero(see Test Method F 1570).4.Significance and Use4.1 Specified resistance is useful to manufacturers and userswhen designing membrane switch interface circuitry.4.2 Actuation force and contact force are useful to manu-facturers and users in determining the suitability,preferenceand aesthetics of a membrane switch in a given application.5.Apparatus5.1 Test ProbeTest probes that do not meet the followingcriteria must be fully specified and recorded.Do not changeprobe type throughout the duration of the test.Switch to be measuredMaterialSize and ShapeTactile switchMetal or non-elasticFlat tip 25 to 50%of tac-tile element diameter rec-ommended.See Fig.1.Non-tactile switchInert elastomeric materialHardness=A/456 5 perTest Method D 2240Fig.2 or Fig.3 or speci-fied5.2 Test Surface,flat,smooth,unyielding and larger thanswitch under test.5.3 Device,to hold test probe securely and provide perpen-dicular movement into and away from switch under test.5.4 Resistance Measuring Device,that is,ohm meter.Thedevice should not apply a voltage outside the operating rangeof the switch contacts.5.5 Suitable Monitoring Device,to measure force on testprobe.6.Procedure6.1 Pre-Test Setup:6.1.1 Secure switch on test surface.6.1.1.1 Precondition switch by depressing manually 25times.6.1.2 Position test probe over desired area of switch.6.1.3 Lower probe until tip is just above top surface ofswitch without touching.6.1.4 Connect switch terminals to resistance measuringdevice(see Fig.4).6.2 In-Process Test: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 May 10,2002.Published July 2002.Originallypublished as F 159795.Last previous edition F 159701.2For 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.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.6.2.1 Begin by activating test probe movement down at arate not to exceed 13 mm/s.6.2.2 Monitor force and resistance during probe movement.6.2.3 When specified resistance is achieved,record force onprobe as contact force(Fc).6.2.3.1 Stop downward movement of test probe.6.2.4 Record maximum force on probe seen during probemovement as actuation force(Fa).This value can be greaterthan or equal to Fc.6.2.5 Retract test probe to the same position as 6.1.3.6.2.6 Repeat 6.2.1-6.2.5 four more times.7.Calculations7.1 Determine the averages of five readings and record asFc and Fa.8.Report8.1 Report the following information:8.1.1 Temperature,8.1.2 Humidity,8.1.3 Barometric Pressure,8.1.4 Test probe shape and durometer,8.1.5 Actuation force(Fa)(may equal contact force),8.1.6 Contact force(Fc),8.1.7 Specified resistance,8.1.8 Description of probe holding fixture and monitoringdevice,8.1.9 Part number or description of switch,or both,and8.1.10 Date of test.9.Precision and Bias9.1 The precision and bias of this test method are underinvesti