ASTM F2592-09

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Designation:F2592–09
Standard Test Method for
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Measuring the Force-Displacement of a Membrane Switch
This standard is issued under the fixed designation F2592; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.1.6 contact displacement (Tc)—the displacement at con-
tact closure.
1.1 This test method covers the measurement of force
2.1.7 contact force (Fc)—the force at contact closure.
displacement characteristics of a membrane switch.
2.1.8 displacement—measured distance of movement when
1.1.1 This test method replaces Test Method F1570 (Tactile
membrane is depressed.
Ratio). Tactile Response Slope better represents the character-
2.1.8.1 Discussion—Displacement is sometimes referred to
ization of tactile sensation, previously called “Tactile Ratio” in
as “switch travel.”
Test Method .
2.1.9 Fmax—an applied force, maximum force measured
1.1.2 This test method replaces Test Method F1682
prior to or including point (Fmin) (see Fig. 1).
(Travel).
2.1.9.1 Discussion—Sometimes referred to as Actuation
1.1.3 This test method replaces Test Method F1597 (Actua-
Force.
tion and Contact Force).
2.1.10 Fmin—an applied force, minimum force seen be-
1.1.4 This test method replaces Test Method F1997 (Switch
tween Fmax and point at which probe movement ceases.
Sensitivity).
2.1.10.1 Discussion—Fmax can equal Fmin.
1.2 Force displacement hysterisis loop curve can be used in
2.1.11 force-displacement hysteresis curve—relationship
the determination of Actuation Force, Displacement, Contact
between force applied and displacement of a membrane switch
Force, Return Force, and Tactile Response Slope.
in terms of the actuation and return (recovery).
1.3 This standard does not purport to address all of the
2.1.11.1 Discussion—Usually expressed as a line graph;
safety concerns, if any, associated with its use. It is the
sometimes referred to as Force-Travel curve (see Fig. 1).
responsibility of the user of this standard to establish appro-
2.1.12 membrane switch—a momentary switching device in
priate safety and health practices and determine the applica-
which at least one contact is on, or made of, a flexible
bility of regulatory limitations prior to use.
substrate.
2. Terminology 2.1.13 non-tactile switch—switch that does not have a
tactile response and therefore has a response slope equal to
2.1 Definitions:
zero because Fmax and Fmin are the same (see Fig. 2).
2.1.1 break displacement (Tb)—the displacement at contact
2.1.14 return min force (Frmin)—minimum force seen
break.
during return cycle before reaching Frmax.
2.1.2 break force (Fb)—the force at contact break.
2.1.15 return max force (Frmax)—maximum force mea-
2.1.3 circuit resistance—electrical resistance as measured
sured during return cycle after achieving Frmin.
between two test points whose internal contacts, when held
2.1.16 specified resistance—maximum allowable resistance
closed, complete a circuit.
as measured between two terminations whose internal switch
2.1.4 closure (make)—the event at which a specified resis-
contacts are held closed to complete a circuit.
tance is achieved.
2.1.17 switch teasing (break)—the displacement measure-
2.1.5 contact break—point at which circuit resistance is
ment on the force-displacement curve between contact break
higher than specified resistance on return.
(Fb) and return force (Frmin).
2.1.18 switch teasing (make)—the displacement measure-
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ment on the force-displacement curve between contact force
This test method is under the jurisdiction of ASTM Committee F01 on
Electronics and is the direct responsibility of Subcommittee F01.18 on Membrane
(Fc) and minimum force (Fmin).
Switches.
2.1.19 tactile recovery slope—rate of change of return force
Current edition approved June 15, 2009. Published July 2009. Originally
with respect to displacement, as measured between TFrmin
approved in 2006. Last previous edition approved in 2008 as F2592-08. DOI:
10.1520/F2592-09. and TFrmax (see Fig. 3).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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F2592–09
NOTE—Area between forward and return curves is the difference in work by the tactile mechanism showing hysterisis in the tactile system.
FIG. 1 Force Displacement Hysterisis Loop
2.1.20 tactile response—a physical sensation, caused by a 3.5 The amount of switch sensitivity or teasing can also be
sudden collapse or snapback, or both, of a membrane switch. a result of poor surface conductivity that will prevent an
2.1.21 tactile response slope—rate of
...