ASTM F2592-07a
(Test Method)Standard Test Method for Measuring the Force-Displacement of a Membrane Switch
Standard Test Method for Measuring the Force-Displacement of a Membrane Switch
SIGNIFICANCE AND USE
The force and displacement values when converted to a slope are useful in quantifying the differences in tactile response among membrane switches.
Specified resistance is useful to manufacturers and users when designing membrane switch interface circuitry.
Actuation force and contact force are useful to manufacturers and users in determining the suitability, reference and aesthetics of a membrane switch in a given application.
The tendency of a switch to make or break electrical contact at unexpected moments during closure or release can be a sign of a poor design. The degree of teasing can range from a simple annoyance to a failure of critical control process.
The amount of switch sensitivity or teasing can also be a result of poor surface conductivity that will prevent an electrical event even when switch poles are in partial contact.
SCOPE
1.1 This test method covers the measurement of force displacement characteristics of a membrane switch.
1.1.1 This test method replaces Test Method F 1570. The Tactile Response Slope has been determined to be a more representative characterization of a tactile sensation.
1.1.2 This test method replaces Test Method F 1682.
1.1.3 This test method replaces Test Method F 1597.
1.1.4 This test method replaces Test Method F 1997.
1.2 Force displacement hysterisis loop curve can be used in the determination of Actuation Force, Displacement, Contact Force, Return Force, and Tactile Response Slope.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
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Designation:F2592–07a
Standard Test Method for
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Measuring the Force-Displacement of a Membrane Switch
This standard is issued under the fixed designation F 2592; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2.1.9.1 Discussion—Sometimes referred to as Actuation
Force.
1.1 This test method covers the measurement of force
2.1.10 Fmin—an applied force, minimum force seen be-
displacement characteristics of a membrane switch.
tween Fmax and point at which probe movement ceases.
1.1.1 This test method replaces Test Method F 1570. The
2.1.10.1 Discussion—Fmax can equal Fmin.
Tactile Response Slope has been determined to be a more
2.1.11 force-displacement hysteresis curve—relationship
representative characterization of a tactile sensation.
between force applied and displacement of a membrane switch
1.1.2 This test method replaces Test Method F 1682.
in terms of the actuation and return (recovery).
1.1.3 This test method replaces Test Method F 1597.
2.1.11.1 Discussion—Usually expressed as a line graph;
1.1.4 This test method replaces Test Method F 1997.
sometimes referred to as Force-Travel curve (see Fig. 1).
1.2 Force displacement hysterisis loop curve can be used in
2.1.12 membrane switch—a momentary switching device in
the determination of Actuation Force, Displacement, Contact
which at least one contact is on, or made of, a flexible
Force, Return Force, and Tactile Response Slope.
substrate.
1.3 This standard does not purport to address all of the
2.1.13 non-tactile switch—switch that does not have a
safety concerns, if any, associated with its use. It is the
tactile response and therefore has a response slope equal to
responsibility of the user of this standard to establish appro-
zero because Fmax and Fmin are the same (see Fig. 2).
priate safety and health practices and determine the applica-
2.1.14 return min force (Frmin)—minimum force seen
bility of regulatory limitations prior to use.
during return cycle before reaching Frmax.
2. Terminology
2.1.15 return max force (Frmax)—maximum force mea-
sured during return cycle after achieving Frmin.
2.1 Definitions:
2.1.16 specified resistance—maximum allowable resistance
2.1.1 break displacement (Tb)—the displacement at contact
as measured between two terminations whose internal switch
break.
contacts are held closed to complete a circuit.
2.1.2 break force (Fb)—the force at contact break.
2.1.17 switch teasing (break)—the displacement measure-
2.1.3 circuit resistance—electrical resistance as measured
ment on the force-displacement curve between contact break
between two test points whose internal contacts, when held
(Fb) and return force (Frmin).
closed, complete a circuit.
2.1.18 switch teasing (make)—the displacement measure-
2.1.4 closure (make)—the event at which a specified resis-
ment on the force-displacement curve between contact force
tance is achieved.
(Fc) and minimum force (Fmin).
2.1.5 contact break—point at which circuit resistance is
2.1.19 tactile recovery slope—rate of change of return force
higher than specified resistance on return.
with respect to displacement, as measured between TFrmin
2.1.6 contact displacement (Tc)—the displacement at con-
and TFrmax (see Fig. 3).
tact closure.
2.1.20 tactile response—a physical sensation, caused by a
2.1.7 contact force (Fc)—the force at contact closure.
sudden collapse or snapback, or both, of a membrane switch.
2.1.8 displacement—measured distance of movement when
2.1.21 tactile response slope—rate of change of applied
a membrane switch is depressed.
force with respect to displacement, as measured between
2.1.9 Fmax—an applied force, maximum force measured
Tfmax and Tfmin (see Figs. 3 and 4).
prior to or including point (Fmin) (see Fig. 1).
2.1.22 tactile switch—a switch that has a tactile response
and therefore has a response slope less than zero (negative
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This test method is under the jurisdiction of ASTM Committee F01 on
slope).
Electronics and is the direct responsibility of Subcommittee F01.18 on Membrane
Switches.
Current edition approved July 1, 2007. Published August 2007. Originally
approved in 2006. Last previous edition approved in 2007 as F 2592-07.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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F2592–07a
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
2.1.23 Tfmax—Displacement at Fmax. 4.2 Theswitchsampleshouldb
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