ASTM F2592-2008 Standard Test Method for Measuring the Force-Displacement of a Membrane Switch.pdf

1、Designation: F 2592 08Standard Test Method forMeasuring the Force-Displacement of a Membrane Switch1This standard is issued under the fixed designation F 2592; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi

2、on. 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 the measurement of forcedisplacement characteristics of a membrane switch.1.1.1 This test method replaces

3、 Test Method F 1570 (TactileRatio). Tactile Response Slope better represents the character-ization of tactile sensation, previously called “Tactile Ratio” inTest Method F 1570.1.1.2 This test method replaces Test Method F 1682(Travel).1.1.3 This test method replaces Test Method F 1597 (Ac-tuation an

4、d Contact Force).1.1.4 This test method replaces Test Method F 1997 (SwitchSensitivity).1.2 Force displacement hysterisis loop curve can be used inthe determination of Actuation Force, Displacement, ContactForce, Return Force, and Tactile Response Slope.1.3 This standard does not purport to address

5、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:F 1570 Test Method

6、for Determining the Tactile Ratio of aMembrane Switch2F 1597 Test Method for Determining the Actuation Forceand Contact Force of a Membrane SwitchF 1682 Test Method for Determining Travel of a MembraneSwitchF 1997 Test Method for Determining the Sensitivity (Teas-ing) of a Tactile Membrane Switch3.

7、Terminology3.1 Definitions:3.1.1 break displacement (Tb)the displacement at contactbreak.3.1.2 break force (Fb)the force at contact break.3.1.3 circuit resistanceelectrical resistance as measuredbetween two test points whose internal contacts, when heldclosed, complete a circuit.3.1.4 closure (make)

8、the event at which a specified resis-tance is achieved.3.1.5 contact breakpoint at which circuit resistance ishigher than specified resistance on return.3.1.6 contact displacement (Tc)the displacement at con-tact closure.3.1.7 contact force (Fc)the force at contact closure.3.1.8 displacementdisplace

9、ment is sometimes referred toas “switch travel.”3.1.9 Fmaxan applied force, maximum force measuredprior to or including point (Fmin) (see Fig. 1).3.1.9.1 DiscussionSometimes referred to as ActuationForce.3.1.10 Fminan applied force, minimum force seen be-tween Fmax and point at which probe movement

10、ceases.3.1.10.1 DiscussionFmax can equal Fmin.3.1.11 force-displacement hysteresis curverelationshipbetween force applied and displacement of a membrane switchin terms of the actuation and return (recovery).3.1.11.1 DiscussionUsually expressed as a line graph;sometimes referred to as Force-Travel cu

11、rve (see Fig. 1).3.1.12 membrane switcha momentary switching device inwhich at least one contact is on, or made of, a flexiblesubstrate.3.1.13 non-tactile switchswitch that does not have atactile response and therefore has a response slope equal tozero because Fmax and Fmin are the same (see Fig. 2)

12、.3.1.14 return min force (Frmin)minimum force seenduring return cycle before reaching Frmax.3.1.15 return max force (Frmax)maximum force mea-sured during return cycle after achieving Frmin.3.1.16 specified resistancemaximum allowable resistanceas measured between two terminations whose internal swit

13、chcontacts are held closed to complete a circuit.3.1.17 switch teasing (break)the displacement measure-ment on the force-displacement curve between contact break(Fb) and return force (Frmin).1This test method is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibil

14、ity of Subcommittee F01.18 on MembraneSwitches.Current edition approved Nov. 1, 2008. Published December 2008. Originallyapproved in 2006. Last previous edition approved in 2007 as F 2592-07a.2Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.1Copyright AS

15、TM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.18 switch teasing (make)the displacement measure-ment on the force-displacement curve between contact force(Fc) and minimum force (Fmin).3.1.19 tactile recovery sloperate of change of return for

16、cewith respect to displacement, as measured between TFrminand TFrmax (see Fig. 3).3.1.20 tactile responsea physical sensation, caused by asudden collapse or snapback, or both, of a membrane switch.3.1.21 tactile response sloperate of change of appliedforce with respect to displacement, as measured b

17、etweenTfmax and Tfmin (see Figs. 3 and 4).3.1.22 tactile switcha switch that has a tactile responseand therefore has a response slope less than zero (negativeslope).3.1.23 TfmaxDisplacement at Fmax.3.1.24 TfminDisplacement at Fmin.3.1.25 Tfrmaxdisplacement at Frmax.3.1.26 Tfrmindisplacement at Frmin

18、.4. Significance and Use4.1 The force and displacement values when converted to aslope are useful in quantifying the differences in tactileresponse among membrane switches.4.2 Specified resistance is useful to manufacturers and userswhen designing membrane switch interface circuitry.4.3 Actuation fo

19、rce and contact force are useful to manu-facturers and users in determining the suitability, reference andaesthetics of a membrane switch in a given application.4.4 The tendency of a switch to make or break electricalcontact at unexpected moments during closure or release canbe a sign of a poor desi

20、gn. The degree of teasing can rangefrom a simple annoyance to a failure of critical control process.4.5 The amount of switch sensitivity or teasing can also bea result of poor surface conductivity that will prevent anelectrical event even when switch poles are in partial contact.5. Interferences5.1

21、Results compared between a manual measurement sys-tem and automated measurement system can be significantbased on the response time of operator and the equipment.5.2 The switch sample should be mounted on a rigid supportin order to get a more accurate representation of the force anddisplacement (tra

22、vel).6. Apparatus6.1 Test Probe, made of non-elastic material with a circularflat tip with a diameter approximately 50 % of the minimumspacer opening for a non-tactile switch or 50 % of the tactileelement diameter for a tactile switch.NOTEArea between forward and return curves is the difference in w

23、ork by the tactile mechanism showing hysterisis in the tactile system.FIG. 1 Force Displacement Hysterisis LoopF25920826.2 Device, to hold probe securely and provide perpendicu-lar movement into and away from switch under test.6.3 Monitoring Device, suitable to detect Fmax, Fmin,Tfmax, and Tfmin.6.4

24、 Test Surface, flat, smooth, unyielding, and larger thanswitch under test.6.5 Resistance Measuring Device, that is, ohm meter. Thedevice should not apply a voltage outside the operating rangeof the switch contacts.7. Procedure7.1 Pre-Test Setup:7.1.1 Ensure that the test specimen is mounted securely

25、 to arigid substrate.7.1.2 Connect switch terminals to resistance measuringdevice.7.1.3 Position test probe over center of the designated areaof switch.7.1.4 Position probe until tip is just above top surface ofswitch without touching.7.1.5 Precondition switch until approximation of steadystate cond

26、ition is achieved. (note this will typically occurbetween 5 to 25 cycles, and it is recommended that theinstrument and test probe be used when practical.)7.2 In-Process Test7.2.1 Begin by activating test probe movement down at arate not to exceed 13 mm/s.7.2.1.1 Record Force-Displacement data to obt

27、ain, at mini-mum, values for Fmax, Fmin, Fc, Tc, Tfmax, and Tfmin. Otherdata points optional.7.2.2 Continue movement until probe stops or when contactclosure is achieved.7.2.3 Reverse direction of test probe until it is no longertouching the top surface of the switch, and record Fb, Tb,Frmin, Frmax,

28、 Tfrmin, Tfrmax.7.2.4 Repeat 7.2.1 through 7.2.3 four additional times.8. Calculations8.1 Calculate Slopes:8.1.1Tactile Response Slope =Fmax(avg) Fmin(avg)Tfmax(avg) Tfmin(avg)8.1.2Tactile RecoverySlope =Frmax(avg) Frmin(avg)Tfrmax(avg) Tfrmin(avg)8.2 Determine switch teasing at makeoptional.8.2.1 D

29、isplacement switch tease (make) = Tc Tfmin.8.2.2 Force switch tease (make) = Fc Fmin.8.3 Determine switch teasing at breakoptional.8.3.1 Displacement switch tease (break) = Tb Tfrmin.8.3.2 Force switch tease (break) = Fb Frmin.FIG. 2 Non-Tactile Switch Force DisplacementF25920839. Report9.1 Report t

30、he following information:9.1.1 Temperature,9.1.2 Humidity,9.1.3 Barometric pressure,9.1.4 Probe material and diameter,9.1.5 Description of test apparatus,9.1.6 Fmax (avg),9.1.7 Fmin (avg),9.1.8 Fc (avg),9.1.9 Fb (avg),9.1.10 Frmax (avg),9.1.11 Frmin (avg),9.1.12 Tfmax (avg),9.1.13 Tfmin (avg),9.1.14

31、 Tactile Response Slope (avg)must report units ofmeasure for force-displacement for example, newtons/mm,9.1.15 Tactile Recovery Slope (avg), optionalmust reportunits of measure for force-displacement for example,newtons/mm,9.1.16 Part number or description of switch, or both,9.1.17 Date of test,9.1.

32、18 Force-displacement curve, optional,9.1.19 Tfrmax(avg),9.1.20 Tfrmin(avg),9.1.21 Speed of probe (if using automated equipment).9.1.22 Displacement switch tease (make)optional,9.1.23 Force switch tease (make)optional,9.1.24 Displacement switch tease (break)optional, and9.1.25 Force switch tease (br

33、eak)optional.FIG. 3 Tactile Response Slope (TRS)FIG. 4 Tactile Response Slope CalculationF259208410. Precision and Bias10.1 The precision and bias of this test method are underinvestigation11. Keywords11.1 force-displacement curve; membrane switch; sensitiv-ity; switch tease; tactile ratio; tactile

34、recovery slope; tactileresponse slope; travelASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, an

35、d the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revisi

36、on of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you sh

37、ouldmake your views known to the ASTM Committee on Standards, 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).F2592085